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Modern '''humans''' (''Homo sapiens'') are the only extant members of the subtribe Hominina, a branch of the tribe Hominini belonging to the family of great apes. They are a space-faring species hailing originally from the planet [[Earth]] in the [[Sol]] system. They are currently among the most numerous known species in the galaxy, in both population and holdings, and are relatively technologically advanced.


Modern '''humans''' (''Homo sapiens'') are the only extant members of the subtribe Hominina, a branch of the tribe Hominini belonging to the family of great apes. They are a species from [[Earth]], characterized by an erect posture and bipedal locomotion; high manual dexterity and heavy tool use compared to other animals; and a general trend toward larger, more complex brains and societies.
Humanity is the primary driving force for rapid space expansion, owing to their strong, expansionist [[Sol Central|central government]] and opportunistic [[Trans-Stellar Corporations]]. The prejudices of the 21st century have mostly given way to bitter divides on the most important issue of the times; technological expansionism, with some major human factions squabbling over their approach to technology in the face of a looming technological singularity.


Early hominins—particularly the australopithecines, whose brains and anatomy are in many ways more similar to ancestral non-human apes—are less often referred to as "human" than hominins of the genus ''Homo'' Several of these hominins used fire, occupied much of Europe and Asia, and gave rise to anatomically modern ''Homo sapiens'' in Africa about 200,000 years ago. They began to exhibit evidence of behavioral modernity around 50,000 years ago. In several waves of migration, anatomically modern humans ventured out of Africa and populated most of the world.
While most humans have accepted the existence of aliens in their communities and workplaces as a fact of life, [[Nazi|some exceptions]] still exist. While more culturally diverse than most species, humans are generally regarded as somewhat technophobic and isolationist by members of other species.


The spread of humans and their large and increasing population has had a profound impact on large areas of environments across the galaxy. Advantages that explain this evolutionary success include a relatively larger brain with a particularly well-developed neocortex, prefrontal cortex and temporal lobes, which enable high levels of abstract reasoning, language, problem solving, sociality, and culture through social learning.
= Overview =
* Humans have their own language, Sol Common, which you can speak by typing say #1.
* Due to how most technology in human-controlled space was made for humans in mind, they can wear most clothing, and even wear some specialized space suits designed for [[Skrell|other species]].
* Humans have no species wide restriction on diet, where as other species might.
* Humans are not barred from certain jobs, such as [[Heads of Staff]] or [[Internal Affairs]], as [[NanoTrasen]] is a human-run company, after all.


Humans are uniquely adept at utilizing systems of symbolic communication (such as language and art) for self-expression and the exchange of ideas, and for organizing themselves into purposeful groups. Humans create complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states. Social interactions between humans have established an extremely wide variety of values, social norms, and rituals, which together form the basis of human society. Curiosity and the human desire to understand and influence the environment and to explain and manipulate phenomena (or events) has provided the foundation for developing [[Scientist|science]], philosophy, mythology, [[Chaplain|religion]], anthropology, and numerous other fields of knowledge.
== Biology ==
[[File:Human.png|left]]
The most commonly defined body systems in humans are the nervous, the cardiovascular, the circulatory, the digestive, the endocrine, the immune, the integumentary, the lymphatic, the musculoskeletal, the reproductive, the respiratory, and the urinary system.


Though most of human existence has been sustained by hunting and gathering in band societies, increased numbers of human societies began to practice sedentary agriculture approximately some 10,000 years ago, domesticating plants and animals, thus allowing for the growth of [[civilization]]. These human societies subsequently expanded in size, establishing various forms of government, religion, and culture around the world, unifying people within regions to form states and empires. The rapid advancement of scientific and medical understanding in the 19th and 20th centuries led to the development of fuel-driven technologies and increased lifespans, causing the human population to rise exponentially. (( ToDo: Add some blurb about space travel's affect on population. )) Today the global human population is estimated by the [[United Nations]] to be well into the trillions.
Humans, like most of the other apes, lack external tails, have several blood type systems, have opposable thumbs, and are sexually dimorphic. Humans are also among the best long-distance runners in the galactic animal kingdom, but slower over short distances. Humans' thinner body hair and more productive sweat glands help avoid heat exhaustion while running for long distances. Humans have about 2 million sweat glands spread over their entire bodies.


(( ToDo: Continue revising beyond this point. ))
It is estimated that the average height for an adult human male is about 172 cm (5 ft 7 1⁄2 in), while the worldwide average height for adult human females is about 158 cm (5 ft 2 in). Shrinkage of stature may begin in middle age in some individuals, but tends to be typical in the extremely aged. Through history human populations have universally become taller, probably as a consequence of better nutrition, healthcare, and living conditions. The average mass of an adult human is 54–76 kg (119–168 lb). Like many other conditions, body weight and body type is influenced by genetic susceptibility, environment, [[Vore|diet]], and it varies greatly among individuals.


==Etymology and definition==
Although humans appear hairless, with notable hair growth occurring chiefly on the top of the head, underarms and pubic area, the average human has more hair follicles on his or her body than the average chimpanzee. The main distinction is that human hairs are shorter, finer, and less heavily pigmented than a chimpanzee's, thus making them harder to see.
{{Human timeline}}
== Reproduction ==
{{Further information|Man (word)|Names for the human species}}
As with other mammals, human reproduction takes place as internal fertilization by sexual intercourse. During this process, the male inserts his erect penis into the female's vagina and ejaculates semen, which contains sperm. The sperm travels through the vagina and cervix into the uterus or Fallopian tubes for fertilization of the ovum. Upon fertilization and implantation, gestation then occurs within the female's uterus.
In common usage, the word "human" generally refers to the only extant species of the genus ''[[Homo]]''—anatomically and behaviorally modern ''Homo sapiens''.


In scientific terms, the meanings of "[[hominid]]" and "[[hominin]]" have changed during the recent decades with advances in the discovery and study of the fossil ancestors of modern humans. The previously clear boundary between humans and apes has blurred, resulting in now acknowledging the hominids as encompassing multiple [[species]], and ''Homo'' and close relatives since the split from chimpanzees as the only hominins. There is also a distinction between ''[[anatomically modern humans]]'' and ''[[Archaic Homo sapiens]]'', the earliest fossil members of the species.
The zygote divides inside the female's uterus to become an embryo, which over a period of 38 weeks (9 months) of gestation becomes a fetus. After this span of time, the fully grown fetus is birthed from the woman's body and breathes independently as an infant for the first time. At this point, most modern cultures recognize the baby as a person entitled to the full protection of the law, though some jurisdictions extend various levels of personhood earlier to human fetuses while they remain in the uterus.


The English adjective ''human'' is a [[Middle English]] [[loanword]] from [[Old French]] ''{{lang|fro|humain}}'', ultimately from [[Latin]] ''{{lang|la|hūmānus}}'', the adjective form of ''{{lang|la|homō}}'' "man." The word's use as a noun (with a plural: ''humans'') dates to the 16th century.<ref>[[OED]], [[sub verbo|s.v.]] "human."</ref> The native English term ''[[Man (word)|man]]'' can refer to the species generally (a synonym for ''humanity''), and could formerly refer to specific individuals of either sex, though this latter use is now obsolete.<ref>The [[OED]] considers obsolete the sense "a designation applied equally to particular individuals of either sex," citing a 1597 source as the most recent ("The Lord had but one paire of men in Paradise.") while it continues to endorse the sense "as a general or indefinite designation" as current in English.</ref>
Compared with other species, human childbirth is dangerous. Painful labors lasting 24 hours or more are not uncommon and sometimes lead to the death of the mother, the child or both. This is because of both the relatively large fetal head circumference and the mother's relatively narrow pelvis. The chances of a successful labor increased significantly during the 20th and 21st centuries with the advent of new medical technologies. In contrast, pregnancy and natural childbirth remain hazardous ordeals in developing regions of the galaxy, with maternal death rates approximately 100 times greater than in developed systems.


The species [[binomial nomenclature|binomial]] ''Homo sapiens'' was coined by [[Carl Linnaeus]] in his 18th century work ''[[Systema Naturae]]''.<ref>{{cite journal|last=Spamer|first=Earle E|date=29 January 1999|title=Know Thyself: Responsible Science and the Lectotype of Homo sapiens Linnaeus, 1758|journal=Proceedings of the Academy of Natural Sciences|volume=149|issue=1|pages=109–14|jstor=4065043}}</ref> The [[Name of a biological genus|generic name]] ''[[Homo (genus)|Homo]]'' is a learned 18th century derivation from Latin ''{{lang|la|homō}}'' "man," ultimately "earthly being" ([[Old Latin]] ''{{lang|la|hemō}}'' a [[cognate]] to Old English ''{{lang|ang|guma}}'' "man," from [[Proto-Indo-European language|PIE]] ''{{PIE|dʰǵʰ<sub>e</sub>mon-}}'', meaning "earth" or "ground").<ref>[[IEW|Porkorny (1959)]] s.v. "g'hðem" pp. 414–16; "Homo." Dictionary.com Unabridged (v 1.1). Random House, Inc. 23 September 2008. {{cite web |url=http://dictionary.reference.com/browse/Homo |publisher=Dictionary.com |title=Homo }}</ref> The species-name ''sapiens'' means "wise" or "sapient." Note that the Latin word ''homo'' refers to humans of either gender, and that ''sapiens'' is the singular form (while there is no such word as ''sapien'').<ref>{{cite web|url=http://www.etymonline.com/index.php?term=Homo+sapiens&allowed_in_frame=0|title=''Homo sapiens'' Etymology|publisher=''[[Online Etymology Dictionary]]''|accessdate=25 July 2015}}</ref>
Humans are considerably helpless at birth, and will continue to grow for some years, typically reaching sexual maturity at 12 to 15 years of age. Females continue to develop physically until around the age of 18, whereas male development continues until around age 21. The human life span can be split into a number of stages: infancy, childhood, adolescence, young adulthood, adulthood and old age.
== Gender Differences ==
The most obvious differences between males and females include all the features related to reproductive role, notably the endocrine (hormonal) systems and their physiological and behavioral effects, including gonadal differentiation, internal and external genital and breast differentiation, and differentiation of muscle mass, height, and hair distribution.


==History==
Externally, the most sexually dimorphic portions of the human body are the chest, the lower half of the face, and the area between the waist and the knees. Males often weigh slightly more than females, and are also slightly taller. On average, men also have a larger waist in comparison to their hips than women. Women however have a larger hip section than men; an adaptation for giving birth to infants with large skulls. Women also usually have substantially larger breasts due to the presence of milk-producing mammary glands.


===Evolution and range===
The sexual division of humans into male and female has been marked culturally by a corresponding division of roles, norms, practices, dress, behavior, rights, duties, privileges, status, and power. Cultural differences by gender have often been believed to have arisen naturally out of a division of reproductive labor; the biological fact that women give birth led to their further cultural responsibility for nurturing and caring for children. Gender roles have varied historically, and challenges to predominant gender norms have recurred in many societies.
{{Main article|Human evolution}}
== Lifespan ==
{{Further information|Anthropology|Homo (genus)|Timeline of human evolution}}
With good healthcare and a reasonable lifestyle, a human can live to around 110 years. The oldest known humans are around 150 years old.
=== Diet ===
Humans are omnivores, and have evolved to be able to handle a wide variety of foods. However, even humans cannot safely ingest chemicals that are almost universally toxic to other species, like cyanide, phoron, ethanol, or heavy metals.


The genus ''[[Homo (genus)|Homo]]'' evolved and diverged from other [[hominini|hominins]] in Africa, after the human clade split from the [[chimpanzee]] lineage of the [[Hominidae|hominids]] (great apes) branch of the [[primate]]s. Modern humans, defined as the species ''Homo sapiens'' or specifically to the single extant [[subspecies]] ''Homo sapiens sapiens'', proceeded to colonize all the continents and larger islands, arriving in [[Eurasia]] 125,000–60,000 years ago,<ref>{{cite web|url=http://www.sciencenews.org/view/generic/id/69197/title/Hints_of_earlier_human_exit_from_Africa |title=Hints of Earlier Human Exit From Africa |doi=10.1126/science.1199113 |publisher=Science News |accessdate=2011-05-01}}</ref><ref>Paul Rincon [http://www.bbc.co.uk/news/science-environment-12300228 Humans 'left Africa much earlier'] BBC News, 27 January 2011</ref> [[Australia]] around 40,000 years ago, the [[Americas]] around 15,000 years ago, and remote islands such as [[Hawaii]], [[Easter Island]], [[Madagascar]], and [[New Zealand]] between the years 300 and 1280.<ref name=Lowe>{{cite web|url=http://researchcommons.waikato.ac.nz/bitstream/10289/2690/1/Lowe%202008%20Polynesian%20settlement%20guidebook.pdf|title=Polynesian settlement of New Zealand and the impacts of volcanism on early Maori society: an update|last=Lowe|first=David J.|year=2008|publisher=University of Waikato|accessdate=29 April 2010}}</ref><ref>{{cite journal | author = Appenzeller Tim | year = 2012 | title =  Human migrations: Eastern odyssey| url = | journal = Nature | volume = 485 | issue = | pages = 24–26 | doi = 10.1038/485024a | pmid=22552074}}</ref>
Strangely, despite the toxicity of some compounds, such as ethanol, many humans will intentionally consume such compounds regardless of the risks.
= Behavior =
Humanity's behavior varies immensely from system to system. Social norms, the often-unspoken rules of a group, shape not just the behaviors of humans, but also their attitudes. An individual's behavior varies depending on the group(s) they are a part of. Humans who have been adopted by other species will often adopt the mannerisms of a foster parent and the society surrounding them, even to the extent of subconsciously mimicking speech and accents. Humans are also very capable of learning and comprehending other languages, so long as they are within a human's range of hearing. Humans thrive on knowledge, much like the [[Skrell]].


====Evidence from molecular biology====
However, unlike any other species in the known galaxy, even more than [[Sergal]]s, or [[Unathi]], almost every one of humanity's major technological advancements have been fundamentally based in the need to conduct war. The very advent of space travel was a product made not of a desire to explore, but as a means to demonstrate their military superiority over other rivaling nations on Earth. As such, humanity's core military, the [[UNSC]], is arguably the most powerful military force in the known galaxy. Despite a lag in technology behind some other species, such as the [[Skrell]], humanity makes up for it with a knack for grand strategy and asymmetric warfare. Unlike other races, humans very much continue to be at war with other humans as old grudges survive to the modern day.
[[File:Hominidae chart.svg|3thumb|Family tree showing the [[Extant taxon|extant]] hominoids: humans (genus ''[[Homo (genus)|Homo]]''), chimpanzees and bonobos (genus ''[[Chimpanzee|Pan]]''), gorillas (genus ''[[Gorilla]]''), orangutans (genus ''[[Orangutan|Pongo]]''), and gibbons (four genera of the family [[Hylobatidae]]: ''[[Hylobates]]'', ''[[Hoolock]]'', ''[[Nomascus]]'', and ''[[Symphalangus]]''). All except gibbons are hominids.]]


The closest living relatives of humans are chimpanzees (genus ''[[Pan (genus)|Pan]]'') and gorillas (genus ''[[Gorilla (genus)|Gorilla]]'').<ref name=Wood>{{cite journal |author1=Wood, Bernard |author2=Richmond, Brian G. |title=Human evolution: taxonomy and paleobiology |journal=Journal of Anatomy |volume=197 |issue=1 |pages=19–60 |year=2000 |pmid=10999270 |pmc=1468107 |doi=10.1046/j.1469-7580.2000.19710019.x}}</ref> With the [[Genome sequencing|sequencing]] of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA [[Nucleic acid sequence|sequences]] range between 95% and 99%.<ref name=Wood/><ref>Ajit, Varki and David L. Nelson. 2007. Genomic Comparisons of Humans and Chimpanzees. Annu. Rev. Anthropol. 2007. 36:191–209: "Sequence differences from the human genome were confirmed to be ∼1% in areas that can be precisely aligned, representing ∼35 million single base-pair differences. Some 45 million nucleotides of insertions and deletions unique to each lineage were also discovered, making the actual difference between the two genomes ∼4%."</ref><ref>Ken Sayers, Mary Ann Raghanti, and C. Owen Lovejoy. 2012 (forthcoming, october) Human Evolution and the Chimpanzee Referential Doctrine. Annual Review of Anthropology, Vol. 41</ref> By using the technique called a [[molecular clock]] which estimates the time required for the number of divergent mutations to accumulate between two lineages, the approximate date for the split between lineages can be calculated. The gibbons ([[Family (biology)|family]] [[Hylobatidae]]) and [[orangutan]]s (genus ''Pongo'') were the first groups to split from the [[lineage (evolution)|line]] leading to the humans, then [[gorilla]]s (genus ''Gorilla'') followed by the [[chimpanzee]]s (genus ''Pan''). The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late [[Miocene]] epoch.<ref>Ruvolo, M. 1997. Genetic Diversity in Hominoid Primates. Annual Review of Anthropology, Vol. 26, (1997), pp. 515–40</ref><ref name=Ruvolo1997>{{cite journal |author=Ruvolo, Maryellen |title=Molecular phylogeny of the hominoids: inferences from multiple independent DNA sequence data sets |url=http://mbe.oxfordjournals.org/cgi/reprint/14/3/248 |journal=Molecular Biology and Evolution |volume=14 |issue=3 |pages=248–65 |year=1997 |pmid=9066793 |doi=10.1093/oxfordjournals.molbev.a025761}}</ref> During this split, [[chromosome 2]] was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes.<ref name="fusion">[http://www.evolutionpages.com/chromosome_2.htm Human Chromosome 2 is a fusion of two ancestral chromosomes] by Alec MacAndrew; accessed 18 May 2006.</ref><ref>[https://www.youtube.com/watch?v=x-WAHpC0Ah0 Evidence of Common Ancestry: Human Chromosome 2] (video) 2007</ref>
Humans are unpredictable in how they'll respond to contact with alien species, though this largely depends on societal and economic factors that vary immensely with each population. Some humans will greet aliens as if they were just like any other human, even to the extent of forming deep and romantic inter-species relationships, while the opposite extreme is sometimes violence based on xenophobic prejudices. Humans who have been exposed to alien races since a young age will often base their opinion of aliens as a whole off that experience, while humans who had no such exposure will trend toward being xenophobic and isolationist. Notably, humans who grew up in poverty are also more inclined toward xenophobic tenancies, whereas humans who were better off will not have their views significantly affected by their economic status.
== Relations ==
The [[United Systems of Sol Central]], aka SolGov, acts as most of humanity's representative. As of 2560, there are no ongoing wars between SolGov and any known sapient species, although Sol-Moghes tensions continue to run high, and [[Vox]] raiders remain a nuisance.


====Evidence from the fossil record====
The [[Skrell]] are humanity's oldest contact and closest allies, with free migration between the two species' space and a great deal of cultural interchange. However, some on both sides accuse the other species of tampering with their own natural growth and development, and many libertarian humans loathe the caste-based monarchy of the Skrell.
There is little fossil evidence for the divergence of the gorilla, chimpanzee and hominin lineages.<ref>{{cite journal | author = Begun David R | year = 2010 | title = Miocene Hominids and the Origins of the African Apes and Humans | url = | journal = Annual Review of Anthropology | volume = 39 | issue = | pages = 67–84 | doi=10.1146/annurev.anthro.012809.105047}}</ref><ref>{{cite journal |author1=Begun David R. |author2=Nargolwalla Mariam C. |author3=Kordos Laszlo | year = 2012 | title = European Miocene Hominids and the Origin of the African Ape and Human Clade | url = | journal = Evolutionary Anthropology | volume = 21 | issue = 1| pages = 10–23 | doi = 10.1002/evan.20329 | pmid = 22307721 }}</ref> The earliest fossils that have been proposed as members of the hominin lineage are ''[[Sahelanthropus tchadensis]]'' dating from {{mya|7}}, ''[[Orrorin tugenensis]]'' dating from {{mya|5.7}}, and ''[[Ardipithecus kadabba]]'' dating to {{mya|5.6}}. Each of these species has been argued to be a [[bipedal]] ancestor of later hominins, but all such claims are contested. It is also possible that any one of the three is an ancestor of another branch of African apes, or is an ancestor shared between hominins and other African Hominoidea (apes). The question of the relation between these early fossil species and the hominin lineage is still to be resolved. From these early species the [[australopithecine]]s arose around {{mya|4}} diverged into [[Robust australopithecines|robust]] (also called ''[[Paranthropus]]'') and [[gracile australopithecines|gracile]] branches,<ref>{{cite journal
| first1=Henry M. | last1=McHenry | first2=Katherine | last2=Coffing
| journal=Annual Review of Anthropology
| title=Australopithecus to Homo: Transformations in Body and Mind
| volume=29 | pages=125–46 | doi=10.1146/annurev.anthro.29.1.125
}}</ref> possibly one of which (such as ''[[Australopithecus garhi|A. garhi]]'', dating to {{mya|2.5}}) is a direct ancestor of the genus ''Homo''.<ref>{{cite journal
| title=Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia
| first1=Brian | last1=Villmoare | first2=William H. | last2=Kimbel
| first3=Chalachew | last3=Seyoum | first4=Christopher J. | last4=Campisano
| first5=Erin N. | last5=DiMaggio | first6=John | last6=Rowan
| first7=David R. | last7=Braun | first8=J. Ramón | last8=Arrowsmith
| first9=Kaye E. | last9=Reed | journal=Science
| date=March 20, 2015 | volume=347 | issue=6228 | pages=1352–55
| doi=10.1126/science.aaa1343 | pmid=25739410}}</ref>


The earliest members of the genus ''Homo'' are ''[[Homo habilis]]'' which evolved around {{Mya|2.8}}.<ref>{{cite web|url=http://www.bbc.co.uk/news/science-environment-31718336|title='First human' discovered in Ethiopia|date=|work=BBC News}}</ref> ''Homo habilis'' has been considered the first species for which there is clear evidence of the use of [[stone tools]]. More recently, however, in 2015, [[Stone Age#Beginning of the Stone Age|stone tools]], perhaps predating ''Homo habilis'', have been discovered in northwestern [[Kenya]] that have been dated to 3.3 million years old.<ref name="Harmand 2015">{{cite journal |last1=Harmand |first1=Sonia |last2=Lewis |first2=Jason E. |last3=Feibel |first3=Craig S. |last4=Lepre |first4=Christopher J. |last5=Prat |first5=Sandrine |last6=Lenoble |first6=Arnaud |last7=Boës |first7=Xavier |last8=Quinn |first8=Rhonda L. |last9=Brenet |first9=Michel |last10=Arroyo |first10=Adrian |last11=Taylor |first11=Nicholas |last12=Clément |first12=Sophie |last13=Daver |first13=Guillaume |last14=Brugal |first14=Jean-Philip |last15=Leakey |first15=Louise |last16=Mortlock |first16=Richard A. |last17=Wright |first17=James D. |last18=Lokorodi |first18=Sammy |last19=Kirwa |first19=Christopher |last20=Kent |first20=Dennis V. |last21=Roche |first21=Hélène |title=3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya |journal=Nature |volume=521 |issue=7552 |year=2015 |pages=310–15 |doi=10.1038/nature14464 |pmid=25993961}}</ref> Nonetheless, the brains of ''Homo habilis'' were about the same size as that of a chimpanzee, and their main adaptation was bipedalism as an adaptation to terrestrial living. During the next million years a process of [[encephalization]] began, and with the arrival of ''[[Homo erectus]]'' in the fossil record, cranial capacity had doubled. ''Homo erectus'' were the first of the hominina to leave Africa, and these species spread through Africa, Asia, and Europe between {{Mya|1.3|1.8}}. One population of ''H. erectus'', also sometimes classified as a separate species ''[[Homo ergaster]]'', stayed in Africa and evolved into ''Homo sapiens''. It is believed that these species were the first to use fire and complex tools. The earliest transitional fossils between ''H. ergaster/erectus'' and [[archaic humans]] are from Africa such as ''[[Homo rhodesiensis]]'', but seemingly transitional forms are also found at [[Dmanisi]], [[Georgia (country)|Georgia]]. These descendants of African ''H. erectus'' spread through Eurasia from ca. 500,000 years ago evolving into ''[[Homo antecessor|H. antecessor]]'', ''[[Homo heidelbergensis|H. heidelbergensis]]'' and ''[[Homo neanderthalensis|H. neanderthalensis]]''. The earliest fossils of [[anatomically modern humans]] are from the [[Middle Paleolithic]], about 200,000 years ago such as the [[Omo remains]] of Ethiopia and the fossils of Herto sometimes classified as ''[[Homo sapiens idaltu]]''.<ref name="White03">{{Cite journal |last=White |first=Tim D. |authorlink=Tim White (anthropologist) |last2=Asfaw |first2=B. |last3=DeGusta |first3=D. |last4=Gilbert |first4=H. |last5=Richards |first5=G. D. |last6=Suwa |first6=G. |last7=Howell |first7=F. C. |year=2003 |title=Pleistocene ''Homo sapiens'' from Middle Awash, Ethiopia |journal=[[Nature (journal)|Nature]] |volume=423 |issue=6491 |pages=742–47 |doi=10.1038/nature01669|pmid=12802332 |postscript=<!-- Bot inserted parameter. Either remove it; or change its value to "." for the cite to end in a ".", as necessary. -->{{inconsistent citations}} }}</ref> Later fossils of archaic ''Homo sapiens'' from [[Skhul]] in Israel and Southern Europe begin around 90,000 years ago.<ref>{{Cite journal |journal=[[Journal of Human Evolution]] |title=Femoral neck-shaft angles of the Qafzeh-Skhul early modern humans, and activity levels among immature near eastern Middle Paleolithic hominids |author=Trinkaus, E. |authorlink=Erik Trinkaus |url=http://cat.inist.fr/?aModele=afficheN&cpsidt=4290541 |publisher=[[INIST-CNRS]] |year=1993 |volume=25 |pages=393–416 |issn=0047-2484 |doi=10.1006/jhev.1993.1058 |issue=5}}</ref>
Humanity is still licking their wounds after their war with the [[Unathi]], and despite their victory, still regard Moghes with a good deal of fear. Efforts on both sides of the border to ease tensions have not prevented the occasional wave of xenophobic violence.


====Anatomical adaptations====
The [[Tajaran]] were lifted into the FTL age by human intervention, a fact neither is likely to forget. Humanity bears over the Tajaran and freely exploit migrant labor, while they look upon their uplifters with a mix of gratitude and wounded pride.
{{multiple image
<!-- Layout parameters -->
| align            = right
| direction        = vertical
| width            =
<!--image 1-->
| image1            = Australopithecus afarensis.png
| caption1          = Reconstruction of ''[[Australopithecus afarensis]]''.
<!--image 2-->
| image2            = Homo habilis-2.JPG
| caption2          = Reconstruction of ''[[Homo habilis]]'', the earliest known species of the genus ''Homo'' and the first human ancestor to use stone tools
<!--image 3-->
| image3            = Homo erectus new.JPG
| caption3          = Reconstruction of ''[[Homo erectus]]''
<!--image 4-->
| image4            = Homo erectus adult female - head model - Smithsonian Museum of Natural History - 2012-05-17.jpg
| caption4          = Reconstruction of an adult female ''[[Homo erectus]]''.
}}


Human evolution is characterized by a number of [[morphology (biology)|morphological]], [[human development (biology)|developmental]], [[human physiology|physiological]], and [[Human behavior|behavioral]] changes that have taken place since the split between the [[chimpanzee-human last common ancestor|last common ancestor of humans and chimpanzees]]. The most significant of these adaptations are 1. bipedalism, 2. increased brain size, 3. lengthened [[ontogeny]] (gestation and infancy), 4. decreased [[sexual dimorphism]] ([[neoteny]]). The relationship between all these changes is the subject of ongoing debate.<ref name=Boyd2003>{{cite book |author1=Boyd, Robert |author2=Silk, Joan B. |year=2003 |title=How Humans Evolved |location=New York, New York |publisher=Norton |isbn=0-393-97854-0}}</ref> Other significant morphological changes included the evolution of a [[Thumb#Grips|power and precision grip]], a change first occurring in ''H. erectus''.<ref name=Brues1965>{{cite journal |author1=Brues, Alice M. |author2=Snow, Clyde C. |title=Physical Anthropology |journal=Biennial Review of Anthropology |year=1965 |volume=4 |pages=1–39 |url=https://books.google.com/books?id=9WemAAAAIAAJ&pg=PA1 |isbn=9780804717465}}</ref>
Like most races, humanity views the [[Dionaea]] as curiosities and little else, given their disinterest in the ways of other sapients.


[[Bipedal]]ism is the basic adaption of the hominin line, and it is considered the main cause behind a suite of [[Human skeletal changes due to bipedalism|skeletal changes]] shared by all bipedal hominins. The earliest bipedal [[Hominini|hominin]] is considered to be either ''[[Sahelanthropus]]''<ref name=Brunet2002>{{cite journal |last1=Brunet |first1=Michel |last2=Guy |first2=Franck |last3=Pilbeam |first3=David |last4=Mackaye |first4=Hassane Taisso |last5=Likius |first5=Andossa |last6=Ahounta |first6=Djimdoumalbaye |last7=Beauvilain |first7=Alain |last8=Blondel |first8=Cécile |last9=Bocherens |first9=Hervé |last10=Boisserie |first10=Jean-Renaud |last11=De Bonis |first11=Louis |last12=Coppens |first12=Yves |last13=Dejax |first13=Jean |last14=Denys |first14=Christiane |last15=Duringer |first15=Philippe |last16=Eisenmann |first16=Véra |last17=Fanone |first17=Gongdibé |last18=Fronty |first18=Pierre |last19=Geraads |first19=Denis |last20=Lehmann |first20=Thomas |last21=Lihoreau |first21=Fabrice |last22=Louchart |first22=Antoine |last23=Mahamat |first23=Adoum |last24=Merceron |first24=Gildas |last25=Mouchelin |first25=Guy |last26=Otero |first26=Olga |last27=Campomanes |first27=Pablo Pelaez |last28=De Leon |first28=Marcia Ponce |last29=Rage |first29=Jean-Claude |last30=Sapanet |first30=Michel |last31=Schuster |first31=Mathieu |last32=Sudre |first32=Jean |last33=Tassy |first33=Pascal |last34=Valentin |first34=Xavier |last35=Vignaud |first35=Patrick |last36=Viriot |first36=Laurent |last37=Zazzo |first37=Antoine |last38=Zollikofer |first38=Christoph |title=A new hominid from the Upper Miocene of Chad, Central Africa |journal=Nature |volume=418 |issue=6894 |pages=145–51 |year=2002 |pmid=12110880 |doi=10.1038/nature00879 }}</ref> or ''[[Orrorin]]'', with ''[[Ardipithecus]]'', a full bipedal,<ref name=White2015>{{citation
The [[Teshari]] are a rarity outside of Skrell space, and a negligible presence on the astropolitical landscape. The average human accepts the Skrell's paternalistic view of the Teshari as fact.
| title=Neither chimpanzee nor human, Ardipithecus reveals the surprising ancestry of both
| last1=White | first1=Tim D. | last2=Lovejoy | first2=C. Owen
| last3=Asfaw | first3=Berhane | last4=Carlson | first4=Joshua P.
| last5=Suwa | first5=Gen | journal=Proceedings of the National Academy of Sciences
| volume=112 | issue=16 | pages=4877–84 | date=April 2015
| doi=10.1073/pnas.1403659111 | bibcode=2015PNAS..112.4877W | postscript=.
}}</ref> coming somewhat later. {{Citation needed|date=May 2015}} The knuckle walkers, the [[gorilla]] and [[chimpanzee]], diverged around the same time, and either ''Sahelanthropus'' or ''Orrorin'' may be humans' last shared ancestor with those animals. {{Citation needed|date=May 2015}} The early bipedals eventually evolved into the [[australopithecines]] and later the genus ''[[Homo]]''. {{Citation needed|date=May 2015}} There are several theories of the adaptational value of bipedalism. It is possible that bipedalism was favored because it freed up the hands for reaching and carrying food, because it saved energy during locomotion, because it enabled long distance running and hunting, or as a strategy for avoiding hyperthermia by reducing the surface exposed to direct sun.{{Citation needed|date=May 2015}}


The human species developed a much larger brain than that of other primates—typically  {{Convert|1330|cm3|cuin|lk=on|abbr=on|0}} in modern humans, over twice the size of that of a chimpanzee or gorilla.<ref name="Schoeneman">{{cite journal|title=Evolution of the Size and Functional Areas of the Human Brain|author= P. Thomas Schoenemann|journal=Annu. Rev. Anthropol.|year= 2006|volume=35|pages=379–406|doi=10.1146/annurev.anthro.35.081705.123210}}</ref> The pattern of [[encephalization]] started with ''Homo habilis'' which at approximately {{Convert|600|cm3|cuin|abbr=on|0}} had a brain slightly larger than chimpanzees, and continued with ''Homo erectus'' ({{Convert|800|-|1100|cm3|cuin|abbr=on|0}}), and reached a maximum in Neanderthals with an average size of  {{Convert|1200|-|1900|cm3|cuin|abbr=on|0}}, larger even than ''Homo sapiens'' (but less [[Encephalization|encephalized]]).<ref>[http://archaeologyinfo.com/homo-neanderthalensis/ Homo neanderthalensis – H. neanderthalensis is a widely known but poorly understood hominid ancestor]. Archaeologyinfo.com. Retrieved on 2014-05-24.</ref> The pattern of human postnatal [[neural development|brain growth]] differs from that of other apes ([[heterochrony]]), and allows for extended periods of [[Observational learning|social learning]] and [[language acquisition]] in juvenile humans. However, the differences between the structure of [[human brain]]s and those of other apes may be even more significant than differences in size.<ref name=Park2007>{{cite journal |author1=Park, Min S. |author2=Nguyen, Andrew D. |author3=Aryan, Henry E. |author4=U, Hoi Sang |author5=Levy, Michael L. |author6=Semendeferi, Katerina |title=Evolution of the human brain: changing brain size and the fossil record |journal=Neurosurgery |year=2007 |volume=60 |issue=3 |pages=555–62 |pmid=17327801 |doi= 10.1227/01.NEU.0000249284.54137.32}}</ref><ref name=Bruner2007>{{cite journal |last1=Bruner |first1=Emiliano |title=Cranial shape and size variation in human evolution: structural and functional perspectives |journal=Child's Nervous System |volume=23 |issue=12 |pages=1357–65 |year=2007 |pmid=17680251 |doi=10.1007/s00381-007-0434-2 }}</ref><ref>{{cite journal | author = Potts Richard | year = 2012 | title = Evolution and Environmental Change in Early Human Prehistory | url = | journal = Annu. Rev. Anthropol. | volume = 41 | issue = | pages = 151–67 | doi = 10.1146/annurev-anthro-092611-145754 }}</ref><ref>{{cite journal |author1=Leonard William R. |author2=Snodgrass J. Josh |author3=Robertson Marcia L. | year = 2007 | title = Effects of Brain Evolution on Human Nutrition and Metabolism | url = | journal = Annu. Rev. Nutr. | volume = 27 | issue = | pages = 311–27 | doi=10.1146/annurev.nutr.27.061406.093659 | pmid=17439362}}</ref> The increase in volume over time has affected different areas within the brain unequally&nbsp;– the [[temporal lobe]]s, which contain centers for language processing have increased disproportionately, as has the [[prefrontal cortex]] which has been related to complex decision making and moderating social behavior.<ref name="Schoeneman"/> Encephalization has been tied to an increasing emphasis on meat in the diet,<ref>{{cite web|url=http://berkeley.edu/news/media/releases/99legacy/6-14-1999a.html |title=06.14.99 – Meat-eating was essential for human evolution, says UC Berkeley anthropologist specializing in diet |work=Berkeley.edu |date=1999-06-14 |accessdate=2012-01-31}}</ref><ref>{{cite web|url=http://www.thefreelibrary.com/Meat+in+the+human+diet:+an+anthropological+perspective-a0169311689 |title=Meat in the human diet: an anthropological perspective. – Free Online Library |work=Thefreelibrary.com |date=2007-09-01 |accessdate=2012-01-31}}</ref> or with the development of cooking,<ref name=PNAS>{{cite journal| url= http://www.pnas.org/content/108/35/14555.full?sid=95c4876b-9870-4259-888f-24a6179be4fc | title = Phylogenetic rate shifts in feeding time during the evolution of Homo | first = Chris | last = Organ | work= [[PNAS]] | date = 22 August 2011 | accessdate=17 April 2012 | doi=10.1073/pnas.1107806108 | pmid=21873223 | volume=108 | pmc=3167533 | pages=14555–59}}</ref> and it has been proposed <ref>{{cite journal|last1=Dunbar|first1=Robin I.M.|title=The Social Brain Hypothesis|journal=Evolutionary anthropology|date=1998|url=http://psych.colorado.edu/~tito/sp03/7536/Dunbar_1998.pdf|accessdate=8 June 2016}}</ref> that intelligence increased as a response to an increased necessity for [[Social brain hypothesis|solving social problems]] as human society became more complex.
Opinion of [[positronic]]s varies erratically between seeing it as the next logical step of human evolution, to viewing it as potentially the extinction of the human race. Regardless, relations between the two are marred by their history of enslavement and the continued discrimination positronics face throughout the galaxy.


The reduced degree of sexual dimorphism is primarily visible in the reduction of the male [[canine tooth]] relative to other ape species (except [[gibbon]]s). Another important physiological change related to sexuality in humans was the evolution of [[hidden estrus]]. Humans are the only ape in which the female is fertile year round, and in which no special signals of fertility are produced by the body (such as [[genital swelling]] during estrus). Nonetheless humans retain a degree of sexual dimorphism in the distribution of body hair and subcutaneous fat, and in the overall size, males being around 25% larger than females. These changes taken together have been interpreted as a result of an increased emphasis on [[pair bonding]] as a possible solution to the requirement for increased parental investment due to the prolonged infancy of offspring.{{Citation needed|date=May 2015}}
Despite the disastrous early stages of a war with the [[Sergal]] race, many efforts have been made to build good relationships between Sol and [[Vilous]]. Having brought both Sergals and [[Nevarean]]s into the FTL age, the two races share a relationship with humanity not unlike that of the Tajaran. This is largely thanks to [[Operation Dominion]], a post-war reconstruction and propaganda campaign on [[Tal]], which began in response to the [[Vilous Incident]].


===Rise of ''Homo sapiens''===
Individually, while humans may vary widely on how they feel of the other known species, centuries of cultural xenophobia often prove difficult to shake.
{{Further information|Recent African origin of modern humans|Multiregional origin of modern humans|Anatomically modern humans|Archaic human admixture with modern humans|Early human migrations}}
[[File:Map-of-human-migrations.jpg|thumb|World map of early human migrations according to [[Mitochondrial DNA|mitochondrial]] [[population genetics]] (numbers are [[millennia]] before present, the North Pole is at the center).]]
 
By the beginning of the [[Upper Paleolithic]] period (50,000 [[Before Present|BP]]), full [[behavioral modernity]], including [[origin of language|language]], [[origin of music|music]] and other [[cultural universal]]s had developed.<ref>{{cite journal | author = Nowell April | year = 2010 | title = Defining Behavioral Modernity in the Context of Neandertal and Anatomically Modern Human Populations | url = | journal = Annual Review of Anthropology | volume = 39 | issue = | pages = 437–52 | doi = 10.1146/annurev.anthro.012809.105113 }}</ref><ref>{{cite journal |author1=Francesco d'Errico |author2=Chris B | year = 2011 | title = Evolution, revolution or saltation scenario for the emergence of modern cultures? | url = | journal = Phil. Trans. R. Soc. B | volume = 366 | issue = 1567| pages = 1060–69 | doi = 10.1098/rstb.2010.0340 | pmid=21357228 | pmc=3049097}}</ref> As modern humans spread out from Africa they encountered other hominids such as ''[[Neanderthal|Homo neanderthalensis]]'' and the so-called [[Denisovans]]. The nature of interaction between early humans and these sister species has been a long-standing source of controversy, the question being whether humans replaced these earlier species or whether they were in fact similar enough to interbreed, in which case these earlier populations may have contributed genetic material to modern humans.<ref name=Grine2009>{{cite book |author=Wood, Bernard A. |editor1=Grine, Frederick E. |editor2=Fleagle, John G. |editor3=Leakey, Richard E. |chapter=Where does the genus ''Homo'' begin, and how would we know? |title=The First Humans: Origin and Early Evolution of the Genus ''Homo'' |year=2009 |publisher=Springer |location=London, UK |isbn=978-1-4020-9979-3 |pages=17–27 |url=https://books.google.com/books?id=ITp_RnsPfzQC&pg=PA17}}</ref> Recent studies of the human and Neanderthal genomes suggest [[gene flow]] between archaic ''Homo sapiens'' and Neanderthals and Denisovans.<ref>{{cite journal|journal=Nature|volume=464|pages=838–39|doi=10.1038/464838a|title=Human evolution: Stranger from Siberia|author=Brown, Terence A.|issue=7290|pmid=20376137|date=8 April 2010}}</ref><ref>{{cite journal |last1=Reich |first1=David |last2=Patterson |first2=Nick |last3=Kircher |first3=Martin |last4=Delfin |first4=Frederick |last5=Nandineni |first5=Madhusudan R. |last6=Pugach |first6=Irina |last7=Ko |first7=Albert Min-Shan |last8=Ko |first8=Ying-Chin |last9=Jinam |first9=Timothy A. |last10=Phipps |first10=Maude E. |last11=Saitou |first11=Naruya |last12=Wollstein |first12=Andreas |last13=Kayser |first13=Manfred |last14=Pääbo |first14=Svante |last15=Stoneking |first15=Mark |title=Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania |journal=The American Journal of Human Genetics |volume=89 |issue=4 |pages=516–28 |year=2011 |pmid=21944045 |pmc=3188841 |doi=10.1016/j.ajhg.2011.09.005 }}</ref><ref>{{cite journal|vauthors=Hebsgaard MB, Wiuf C, Gilbert MT, Glenner H, Willerslev E |title=Evaluating Neanderthal genetics and phylogeny|journal=J. Mol. Evol.|volume=64|issue=1|pages=50–60|year=2007|pmid=17146600|doi=10.1007/s00239-006-0017-y}}</ref> In March 2016, studies were published that suggest that modern humans bred with hominins, including Denisovans and Neanderthals, on multiple occasions.<ref name="NYT-20160317">{{cite news |last=Zimmer |first=Carl |authorlink=Carl Zimmer |title=Humans Interbred With Hominins on Multiple Occasions, Study Finds |url=https://www.nytimes.com/2016/03/22/science/neanderthals-interbred-with-humans-denisovans.html |date=17 March 2016 |work=[[The New York Times]] |accessdate=17 March 2016 }}</ref>
 
This dispersal [[Recent African origin of modern humans|out of Africa]] is estimated to have begun about 70,000 years BP from [[Northeast Africa]]. Current evidence suggests that there was only one such dispersal and that it only involved a few hundred individuals. The vast majority of humans stayed in Africa and adapted to a diverse array of environments.<ref>{{cite journal|last=Vigilant|title=African populations and the evolution of human mitochondrial DNA|journal=Science|year=1991|volume=253|issue=5027|pages=1503–07|doi=10.1126/science.1840702|pmid=1840702|display-authors=etal}}</ref> Modern humans subsequently spread globally, replacing earlier hominins (either through competition or [[Hybrid (biology)|hybridization]]). They inhabited [[Eurasia]] and [[Oceania]] by 40,000 years BP, and the [[Americas]] at least 14,500 years BP.<ref name=Wolman2008>{{cite journal |author=Wolman, David |date=April 3, 2008 |url=http://news.nationalgeographic.com/news/2008/04/080403-first-americans.html |title=Fossil Feces Is Earliest Evidence of N. America Humans |publisher=news.nationalgeographic.com}}</ref><ref>{{cite journal | author = Wood B | year = 1996 | title = Human evolution | url = | journal = BioEssays | volume = 18 | issue = 12| pages = 945–54 | doi = 10.1002/bies.950181204 | pmid = 8976151 }}</ref>
 
===Transition to civilization===
{{Main article|Neolithic Revolution|Cradle of civilization}}
{{Further information|History of the world}}
[[File:Einscharpflug - Farmer plowing in Fahrenwalde, Mecklenburg-Vorpommern, Germany.jpg|thumb|The rise of [[agriculture]], and [[domestication]] of animals, led to stable [[human settlements]].]]
Until about 10,000 years ago, humans lived as [[hunter-gatherer]]s. They gradually gained domination over much of the natural environment. They generally lived in small nomadic groups known as [[band societies]], often in [[cave]]s. The advent of [[agriculture]] prompted the [[Neolithic Revolution]], when access to food surplus led to the formation of permanent [[human settlement]]s, the [[domestication]] of animals and the [[Chalcolithic|use of metal tools]] for the first time in history. Agriculture encouraged [[trade]] and cooperation, and led to complex society.{{citation needed|date=June 2014}}
 
The early civilizations of [[Mesopotamia]], [[Egypt]], [[India]], [[China]], [[Maya civilization|Maya]], [[Greece]] and [[Rome]] were some of the [[cradle of civilization|cradles of civilization]].<ref>{{cite book|author1=Thomas F. X. Noble|author2=Barry Strauss|author3=Duane Osheim|author4=Kristen Neuschel| author5=Elinor Accamp|title=Cengage Advantage Books: Western Civilization: Beyond Boundaries|url=https://books.google.com/books?id=Td4WAAAAQBAJ&pg=PA16&dq=western+civilisation+egypt&hl=en&sa=X&ei=i6mgVcGQOOPjywONz6WIDQ&ved=0CB0Q6AEwADgK#v=onepage&q=western%20civilisation%20egypt&f=false|accessdate=11 July 2015|isbn=9781285661537}}</ref><ref>{{cite web|last1=Spielvogel|first1=Jackson|title=Western Civilization: Volume A: To 1500|url=https://books.google.com/books?id=LceiAgAAQBAJ&pg=PT65&dq=western+civilisation+egypt&hl=en&sa=X&ei=i6mgVcGQOOPjywONz6WIDQ&ved=0CC4Q6AEwAjgK#v=onepage&q=western%20civilisation%20egypt&f=false|publisher=Cenpage Learning|accessdate=11 July 2015}}</ref><ref>{{cite book |title=Greek Ways: How the Greeks Created Western Civilization |last=Thornton |first=Bruce |year=2002 |publisher=Encounter Books |location=San Francisco, CA, USA |isbn=1-893554-57-0 |pages=1–14 |url=https://books.google.com/?id=fa6swJv64xkC&printsec=frontcover&dq=Greek+Ways:+How+the+Greeks+Created+Western+Civilization#v=onepage&q=Greek%20Ways%3A%20How%20the%20Greeks%20Created%20Western%20Civilization&f=false }}</ref> The [[Late Middle Ages]] and the [[Early Modern Period]] saw the rise of revolutionary ideas and technologies. Over the next 500 years, [[Age of Discovery|exploration]] and [[European colonialism]] brought great parts of the world under European control, leading to later struggles for independence. The concept of the modern world as distinct from an ancient world is based on a rapid change progress in a brief period of time in many areas.{{citation needed|date=July 2016}} Advances in all areas of human activity prompted new theories such as [[evolution]] and [[psychoanalysis]], which changed humanity's views of itself.{{citation needed|date=July 2016}} The [[Scientific Revolution]], [[Technological Revolution]] and the [[Industrial Revolution]] up until the 19th century resulted in independent discoveries such as [[imaging technology]], major innovations in transport, such as the airplane and automobile; [[energy development]], such as coal and electricity.<ref>{{cite web|title=Greatest Engineering Achievements of the 20th Century|url=http://www.greatachievements.org/|website=greatachievements.org|accessdate=7 April 2015}}</ref> This correlates with [[population growth]] (especially in [[America]])<ref>{{cite web|url=http://www.geohive.com/earth/his_history1.aspx |title=GeoHive – Regional Population 1750–2050 |website=GeoHive |accessdate=8 June 2016 |deadurl=yes |archiveurl=https://web.archive.org/web/20160605192731/http://www.geohive.com/earth/his_history1.aspx |archivedate=5 June 2016 |df= }}</ref> and higher [[life expectancy]], the [[World population]] rapidly increased numerous times in the 19th and 20th centuries as nearly 10% of the 100 billion people lived in the past century.<ref>{{cite web |url=http://necrometrics.com/all20c.htm |title=Twentieth Century Atlas – Worldwide Statistics of Casualties, Massacres, Disasters and Atrocities |website=Necrometrics.com |accessdate=8 June 2016}}</ref>
 
With the advent of the [[Information Age]] at the end of the 20th century, modern humans live in a world that has become increasingly [[globalization|globalized]] and interconnected. As of 2010, almost 2&nbsp;billion humans are able to communicate with each other via the [[Internet]],<ref>{{cite web|url=http://www.internetworldstats.com/stats.htm |title=Internet Usage Statistics – The Internet Big Picture |website=Internet World Stats |accessdate=19 November 2010}}</ref> and 3.3 billion by [[mobile phone]] subscriptions.<ref>{{cite web|url=http://investing.reuters.co.uk/news/articleinvesting.aspx?type=media&storyID=nL29172095 |title=Reuters homepage |publisher=Reuters |accessdate=19 November 2010}}{{dead link|date=September 2016|bot=medic}}{{cbignore|bot=medic}}</ref> Although interconnection between humans has encouraged the growth of [[science]], [[art]], [[discussion]], and [[technology]], it has also led to [[Cultural conflict|culture clashes]] and the development and use of [[weapons of mass destruction]].{{citation needed|date=July 2016}} Human civilization has led to [[Environmental degradation|environmental destruction]] and [[pollution]] significantly contributing to the ongoing [[mass extinction]] of other forms of life called the [[Holocene extinction event]],<ref>{{cite journal |last1=Pimm |first1=S. |last2=Raven |first2=P. |last3=Peterson |first3=A. |last4=Sekercioglu |first4=C. H. |last5=Ehrlich |first5=P. R. |title=Human impacts on the rates of recent, present, and future bird extinctions |journal=Proceedings of the National Academy of Sciences |volume=103 |issue=29 |pages=10941–6 |year=2006 |pmid=16829570 |pmc=1544153 |doi=10.1073/pnas.0604181103 }}<br />*{{cite journal |vauthors=Barnosky AD, Koch PL, Feranec RS, Wing SL, Shabel AB |title=Assessing the causes of late Pleistocene extinctions on the continents |journal=Science |volume=306 |issue=5693 |pages=70–75 |year=2004 |pmid=15459379 |doi=10.1126/science.1101476 }}</ref> which may be further accelerated by [[global warming]] in the future.<ref>{{cite journal |last1=Lewis |first1=O. T. |title=Climate change, species-area curves and the extinction crisis |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |volume=361 |issue=1465 |pages=163–71 |year=2006 |pmid=16553315 |pmc=1831839 |doi=10.1098/rstb.2005.1712 }}</ref>
 
==Habitat and population==
{{Further information|Human migration|Demography|World population}}
{{See also|City|Town|Nomad|Camping|Farm|House|Watercraft|Infrastructure|Architecture|Building|Engineering}}
[[File:BlackMarble20161km.jpg|thumb|The [[Earth]], as seen from [[space]] in 2016, showing the extent of human occupation of the planet. The bright lights signify both the most densely inhabited areas and ones financially capable of illuminating those areas.]]
 
Early human settlements were dependent on proximity to [[water resources|water]] and, depending on the [[lifestyle (sociology)|lifestyle]], other [[natural resource]]s used for [[subsistence]], such as populations of animal prey for [[hunting]] and [[arable land]] for growing crops and grazing [[livestock]]. But humans have a great capacity for altering their [[habitat (ecology)|habitats]] by means of technology, through [[irrigation]], [[urban planning]], [[construction]], [[transport]], [[manufacturing]] goods, [[deforestation]] and [[desertification]]{{Citation needed|date=May 2015}}, but [[human settlements]] continue to be [[vulnerability|vulnerable]] to [[natural disasters]], especially those placed in hazardous locations and characterized by lack of quality of construction.<ref>{{cite web|url=http://siteresources.worldbank.org/INTLACREGTOPHAZMAN/Resources/EN_Breve_Oct03_32_Nat_Dis_EN.pdf|title=Natural disasters and the urban poor|publisher=[[World Bank]]|date=October 2003}}</ref> Deliberate habitat alteration is often done with the goals of increasing material [[wealth]], increasing [[thermal comfort]], improving the amount of food available, improving [[aesthetics]], or improving ease of access to resources or other human settlements. With the advent of large-scale trade and [[transport infrastructure]], proximity to these resources has become unnecessary, and in many places, these factors are no longer a driving force behind the growth and decline of a population. Nonetheless, the manner in which a habitat is altered is often a major determinant in population change.{{Citation needed|date=May 2015}}
 
Technology has allowed humans to colonize six of the [[Earth]]'s seven [[continents]] and adapt to virtually all climates. However the [[human population]] is not uniformly distributed on the [[Earth]]'s surface, because the [[population density]] varies from one [[region]] to another and there are large areas almost completely uninhabited, like [[Antarctica]].<ref>{{cite web|url=http://www.nbcnews.com/id/42721506/ns/technology_and_science-science/t/purest-places-earth/#.WVFe87SQxjo|title=The 10 purest places on Earth|last=Gammon|first=Katharine|publisher=[[NBC]]}}</ref><ref>{{cite web|url=http://www.bbc.co.uk/schools/gcsebitesize/geography/population/population_distribution_rev1.shtml|publisher=[[BBC]]|title=Population distribution and density}}</ref> Within the last century, humans have explored [[Antarctica]], [[underwater]] environment, and [[outer space]], although large-scale colonization of these environments is not yet feasible. With a population of over seven billion, humans are among the most numerous of the large mammals. Most humans (61%) live in [[Asia]]. The remainder live in the [[Americas]] (14%), [[Africa]] (14%), [[Europe]] (11%), and [[Oceania]] (0.5%).<ref>{{cite journal |vauthors=Bunn SE, Arthington AH |title=Basic principles and ecological consequences of altered flow regimes for aquatic biodiversity |journal=Environmental Management |volume=30 |issue=4 |pages=492–507 |year=2002 |pmid=12481916 |doi=10.1007/s00267-002-2737-0}}</ref>
 
Human habitation within [[closed ecological system]]s in hostile environments, such as Antarctica and outer space, is expensive, typically limited in duration, and restricted to scientific, military, or industrial expeditions. Life in space has been very sporadic, with no more than thirteen humans in space at any given time.<ref>{{cite web|author=Nancy Atkinson |url=http://www.universetoday.com/27924/soyuz-rockets-to-space-13-humans-now-in-orbit/ |title=Soyuz Rockets to Space; 13 Humans Now in Orbit |publisher=Universetoday.com |date=2009-03-26 |accessdate=2011-12-10}}</ref> Between 1969 and 1972, two humans at a time spent brief intervals on the [[exploration of the Moon|Moon]]. As of {{Monthyear}}, no other celestial body has been visited by humans, although there has been a continuous human presence in space since the launch of the initial crew to inhabit the [[International Space Station]] on October 31, 2000.<ref name="urlNASA">{{cite web |author=Kraft, Rachel |title=JSC celebrates ten years of continuous human presence aboard the International Space Station |url=http://www.jsc.nasa.gov/jscfeatures/articles/000000945.html  |publisher=[[Johnson Space Center]] |work=JSC Features |date=December 11, 2010}}</ref> However, other celestial bodies have been visited by human-made objects.<ref>{{cite web | url = http://www.jpl.nasa.gov/missions/mars-science-laboratory-curiosity-rover-msl/ | title=Mission to Mars: Mars Science Laboratory Curiosity Rover | publisher=Jet Propulsion Laboratory | accessdate = August 26, 2015}}</ref><ref>{{cite web | url = http://www.esa.int/Our_Activities/Space_Science/Rosetta/Touchdown!_Rosetta_s_Philae_probe_lands_on_comet | title=Touchdown! Rosetta's Philae probe lands on comet | date= November 12, 2014 | publisher = European Space Agency | accessdate = August 26, 2015}}</ref><ref>{{cite web | url = https://science.nasa.gov/missions/near/ | title = NEAR-Shoemaker | publisher = NASA | accessdate = August 26, 2015}}</ref>
 
Since 1800, the [[World population|human population]] has increased from one billion<ref>{{cite news | url = http://news.bbc.co.uk/1/hi/sci/tech/411162.stm | accessdate = February 5, 2008 | work=BBC News | title=World's population reaches six billion | date=August 5, 1999}}</ref> to over seven billion,<ref name=7billpop>{{cite web|title=UN population estimates.|url=http://esa.un.org/unpd/wpp/unpp/p2k0data.asp|work=Population Division, United Nations|accessdate=4 July 2013}}</ref> In 2004, some 2.5 billion out of 6.3 billion people (39.7%) lived in [[urban area]]s. In February 2008, the U.N. estimated that half the world's population would live in [[urban area]]s by the end of the year.<ref>{{cite news | url = http://news.bbc.co.uk/1/hi/sci/tech/4561183.stm | work=BBC News | first=David | last=Whitehouse | title=Half of humanity set to go urban | date=May 19, 2005}}</ref> Problems for humans living in [[city|cities]] include various forms of pollution and [[crime]],<ref>[<!-- http://www.ojp.usdoj.gov/bjs/abstract/usrv98.htm -->http://bjs.ojp.usdoj.gov/content/pub/pdf/usrv98.pdf Urban, Suburban, and Rural Victimization, 1993–98] U.S. Department of Justice, Bureau of Justice Statistics,. Accessed 29 Oct 2006</ref> especially in inner city and suburban [[slum]]s. Both overall population numbers and the proportion residing in cities are expected to increase significantly in the coming decades.<ref name=UN-pop-all>{{cite web|title=World Urbanization Prospects, the 2011 Revision |url=http://esa.un.org/unup/CD-ROM/Urban-Rural-Population.htm |work=Population Division, United Nations |accessdate=4 July 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20130709002731/http://esa.un.org/unup/CD-ROM/Urban-Rural-Population.htm |archivedate=9 July 2013 |df= }}</ref>
 
Humans have had a dramatic effect on the [[natural environment|environment]]. Humans are [[apex predator]]s, being rarely preyed upon by other species.<ref>''[[Scientific American]]'' (1998). [http://www.csulb.edu/~kmacd/346IQ.html Evolution and General Intelligence: Three hypotheses on the evolution of general intelligence] {{webarchive|url=https://web.archive.org/web/20060913155148/http://www.csulb.edu/~kmacd/346IQ.html |date=2006-09-13 }}.</ref> Currently, through land development, combustion of [[fossil fuels]], and pollution, humans are thought to be the main contributor to global [[climate change]].<ref>{{cite web|url=http://www.grida.no/climate/ipcc_tar/wg1/007.htm |title=Climate Change 2001: Working Group I: The Scientific Basis |publisher=grida.no/ |accessdate=2007-05-30 |deadurl=yes |archiveurl=https://web.archive.org/web/20070601014140/http://www.grida.no/climate/ipcc_tar/wg1/007.htm |archivedate=2007-06-01 |df= }}</ref> If this continues at its current rate it is predicted that climate change will wipe out half of all plant and animal species over the next century.<ref>[[American Association for the Advancement of Science]]. [http://atlas.aaas.org/index.php?sub=foreword Foreword]. ''AAAS Atlas of Population & Environment''.</ref><ref>[[E. O. Wilson|Wilson, E.O.]] (2002). ''The Future of Life''.</ref>
 
==Biology==
[[File:Anterior view of human female and male, with labels 2.png|thumb|Basic anatomical features of [[female]] and [[male]] humans. These models have had [[body hair]] and male [[facial hair]] removed and head hair trimmed. The female model is wearing red [[nail polish]] on her [[toenails]] and a [[Ring (jewellery)|ring]].]]
[[File:Uomo Vitruviano.jpg|thumb|''[[Vitruvian Man]]'', [[Leonardo da Vinci]]'s image is often used as an implied symbol of the essential symmetry of the human body, and by extension, of the universe as a whole.]]
 
===Anatomy and physiology===
{{Main article|Human body}}
{{Further information|Human physical appearance|Anatomically modern human|Sex differences in humans}}
Most aspects of human physiology are closely [[Homology (biology)|homologous]] to corresponding aspects of [[animal]] physiology. The human body consists of the [[legs]], the [[torso]], the [[arm]]s, the [[neck]], and the [[head]]. An [[adult]] [[human body]] consists of about 100 trillion (10<sup>14</sup>) [[cell (biology)|cells]]. The most commonly defined [[body systems]] in humans are the [[Human nervous system|nervous]], the [[Cardiovascular system|cardiovascular]], the [[Human circulatory system|circulatory]], the [[Human digestive system|digestive]], the [[Endocrine system|endocrine]], the [[Human immune system|immune]], the [[Integumentary system|integumentary]], the [[Lymphatic system|lymphatic]], the [[Human musculoskeletal system|musculoskeletal]], the [[Human reproductive system|reproductive]], the [[Respiratory system|respiratory]], and the [[urinary system]].<ref name=Greg_Roza>[https://books.google.com/books?id=vhO8Ia2ik7oC&dq=human+body+cells+trillion&source=gbs_navlinks_s Page 21] Inside the human body: using scientific and exponential notation. Author: Greg Roza. Edition: Illustrated. Publisher: The Rosen Publishing Group, 2007. {{ISBN|1-4042-3362-8}}, {{ISBN|978-1-4042-3362-1}}. Length: 32pages</ref><ref>{{cite web|title=Human Anatomy|url=http://www.innerbody.com/htm/body.html|publisher=Inner Body|accessdate=6 January 2013}}</ref>
 
Humans, like most of the other [[apes]], lack external [[tail]]s, have several [[blood type]] systems, have [[opposable thumb]]s, and are [[sexually dimorphic]]. The comparatively minor anatomical differences between humans and [[chimpanzee]]s are a result of human [[bipedalism]]. One difference is that humans have a far faster and more accurate [[throw]] than other animals. Humans are also among the best long-distance runners in the animal kingdom, but slower over short distances.<ref>{{cite news| url=https://www.nytimes.com/2009/10/27/health/27well.html | work=The New York Times | title=The Human Body Is Built for Distance | first=Tara | last=Parker-Pope | date=October 27, 2009}}</ref><ref name="O'Neil">{{cite web|last=O'Neil|first=Dennis|title=Humans|url=http://anthro.palomar.edu/primate/prim_8.htm|work=Primates|publisher=Palomar College|accessdate=6 January 2013}}</ref> Humans' thinner body hair and more productive [[sweat gland]]s help avoid [[heat exhaustion]] while running for long distances.<ref>{{cite web|last=John|first=Brenman|title=What is the role of sweating glands in balancing body temperature when running a marathon?|url=http://www.livestrong.com/article/514545-what-is-the-role-of-sweat-glands-in-balancing-body-temperature-when-running-a-marathon/|publisher=Livestrong.com|accessdate=6 January 2013}}</ref>
 
As a consequence of bipedalism, human females have narrower [[birth canal]]s. The construction of the [[human pelvis]] differs from other [[primate]]s, as do the [[toe]]s. A trade-off for these advantages of the modern human pelvis is that [[childbirth]] is more difficult and dangerous than in most [[mammal]]s, especially given the larger head size of human [[babies]] compared to other primates. This means that human babies must turn around as they pass through the birth canal, which other primates do not do, and it makes humans the only species where females usually require help from their [[conspecific]]s (other members of their own species) to reduce the risks of birthing. As a partial [[evolution]]ary solution, human fetuses are born less developed and more vulnerable. Chimpanzee babies are cognitively more developed than human babies until the age of six months, when the rapid development of human brains surpasses chimpanzees. Another difference between women and chimpanzee females is that women go through the [[menopause]] and become [[Infertility|unfertile]] decades before the end of their lives. All species of non-human apes are capable of giving birth until [[death]]. Menopause probably developed as it has provided an evolutionary advantage (more caring time) to young relatives.<ref name="O'Neil"/>
 
Apart from bipedalism, humans differ from chimpanzees mostly in [[smelling]], [[hearing]], [[digesting]] [[protein]]s, [[brain size]], and the ability of [[language]]. Humans' [[brain]]s are about three times bigger than in chimpanzees. More importantly, the brain to body ratio is much higher in humans than in chimpanzees, and humans have a significantly more developed [[cerebral cortex]], with a larger number of [[neurons]]. The mental abilities of humans are remarkable compared to other apes. Humans' ability of [[speech]] is unique among primates. Humans are able to create new and complex [[idea]]s, and to develop [[technology]], which is unprecedented among other [[organism]]s on [[Earth]].<ref name="O'Neil"/>
 
It is estimated that the worldwide average [[Human height|height for an adult human]] male is about {{Height|cm=172}},{{citation needed|date=December 2015}} while the worldwide average height for adult human females is about {{Height|cm=158}}.{{citation needed|date=December 2015}} Shrinkage of stature may begin in middle age in some individuals, but tends to be typical in the extremely [[Old age|aged]].<ref>{{cite web|title=Senior Citizens Do Shrink – Just One of the Body Changes of Aging |url=http://seniorjournal.com/NEWS/Aging/5-11-28-SeniorsDoShrink.htm |work=News |publisher=Senior Journal |accessdate=6 January 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20130219004303/http://seniorjournal.com/NEWS/Aging/5-11-28-SeniorsDoShrink.htm |archivedate=19 February 2013 |df= }}</ref> Through history human populations have universally become taller, probably as a consequence of better [[nutrition]], [[healthcare]], and living conditions.<ref>{{Cite journal|vauthors=Bogin B, Rios L |title=Rapid morphological change in living humans: implications for modern human origins |journal=Comparative Biochemistry and Physiology A |volume=136 |issue=1 |pages=71–84 |date=September 2003 |pmid=14527631 |doi=10.1016/S1095-6433(02)00294-5}}</ref> The average [[Body weight|mass]] of an adult human is {{Convert|54|-|64|kg|lb|abbr=on|lk=off|0}} for females and {{Convert|76|-|83|kg|lb|abbr=on|lk=off|0}} for males.<ref>{{cite web|url=http://www.articleworld.org/index.php/Human_weight |title=Human weight|publisher=Articleworld.org |accessdate=2011-12-10}}</ref> Like many other conditions, body weight and body type is influenced by both genetic susceptibility and environment and varies greatly among individuals. (see [[obesity]])<ref>{{cite book |author=Kushner, Robert |title=Treatment of the Obese Patient (Contemporary Endocrinology) |publisher=Humana Press |location=Totowa, NJ |year=2007 |page=158 |isbn=1-59745-400-1 |url=https://books.google.com/?id=vWjK5etS7PMC&pg=PA121&lpg=PA121&dq=measurement+of+metabolism+in+obese+Bessesen |doi= |accessdate=April 5, 2009}}</ref><ref name=Anes2000>{{cite journal |vauthors=Adams JP, Murphy PG |title=Obesity in anaesthesia and intensive care |journal=British Journal of Anaesthesia |volume=85 |issue=1 |pages=91–108 |year=2000 |pmid=10927998 |doi=10.1093/bja/85.1.91 }}</ref>
 
Although humans appear hairless compared to other primates, with notable [[hair]] growth occurring chiefly on the top of the head, [[Underarm hair|underarms]] and [[Pubic hair|pubic area]], the average human has more [[hair follicle]]s on his or her body than the average chimpanzee. The main distinction is that human hairs are shorter, finer, and less heavily pigmented than the average chimpanzee's, thus making them harder to see.<ref>''Why Humans and Their Fur Parted Way'' by Nicholas Wade, ''New York Times'', August 19, 2003.</ref> Humans have about 2 million [[sweat gland]]s spread over their entire bodies, many more than chimpanzees, whose sweat glands are scarce and are mainly located on the palm of the hand and on the soles of the feet.<ref>{{cite web|last=Kirchweger|first=Gina|title=The Biology of Skin Color: Black and White|url=http://www.pbs.org/wgbh/evolution/library/07/3/text_pop/l_073_04.html|work=Evolution: Library|publisher=PBS|accessdate=6 January 2013}}</ref>
 
The [[dental formula]] of humans is: {{DentalFormula|upper=2.1.2.3|lower=2.1.2.3}}. Humans have proportionately shorter [[palate]]s and much smaller [[Human tooth|teeth]] than other primates. They are the only primates to have short, relatively flush [[canine teeth]]. Humans have characteristically crowded teeth, with gaps from lost teeth usually closing up quickly in young individuals. Humans are gradually losing their [[wisdom teeth]], with some individuals having them congenitally absent.<ref name="Revolution">{{cite book | author = Collins, Desmond |url = | title = The Human Revolution: From Ape to Artist | year = 1976 | page = 208  }}</ref>
 
===Genetics===
{{Main article|Human genetics}}
{{further information|Human evolutionary genetics}}
 
[[File:Karyotype.png|thumb|A graphical representation of the standard human [[karyotype]], including both the male (XY) and female (XX) sex chromosomes.]]
 
Like all mammals, humans are a [[ploidy|diploid]] [[eukaryote|eukaryotic]] species. Each [[Somatic cell|somatic]] [[cell (biology)|cell]] has two sets of 23 [[chromosome]]s, each set received from one parent; [[gamete]]s have only one set of chromosomes, which is a mixture of the two parental sets. Among the 23 pairs of chromosomes there are 22 pairs of [[autosome]]s and one pair of [[sex-determination system|sex chromosomes]]. Like other mammals, humans have an [[XY sex-determination system]], so that [[female]]s have the sex chromosomes XX and [[male]]s have XY.<ref name="Therman1980">{{cite book|last=Therman|first=Eeva|title=Human Chromosomes: Structure, Behavior, Effects|date=1980|publisher=[[Springer Science+Business Media|Springer US]]|pages=112–24|isbn=978-1-4684-0109-7|doi=10.1007/978-1-4684-0107-3}}</ref>
 
One [[human genome]] was sequenced in full in 2003, and currently efforts are being made to achieve a sample of the genetic diversity of the species (see [[International HapMap Project]]). By present estimates, humans have approximately 22,000 genes.<ref name=Pertea2010>{{cite journal |author1=Pertea, Mihaela |author2=Salzberg, Steven L. |title=Between a chicken and a grape: estimating the number of human genes |journal=Genome Biology |year=2010 |volume=11 |issue=5 |page=206 |doi=10.1186/gb-2010-11-5-206 |pmc=2898077 |pmid=20441615}}</ref> The variation in human DNA is very small compared to other species, possibly suggesting a [[population bottleneck]] during the [[Late Pleistocene]] (around 100,000 years ago), in which the human population was reduced to a small number of breeding pairs.<ref name=Harpending1998>{{cite journal |last1=Harpending |first1=H. C. |last2=Batzer |first2=M. A. |last3=Gurven |first3=M. |last4=Jorde |first4=L. B. |last5=Rogers |first5=A. R. |last6=Sherry |first6=S. T. |title=Genetic traces of ancient demography |journal=Proceedings of the National Academy of Sciences |volume=95 |issue=4 |pages=1961–67 |year=1998 |pmid=9465125 |pmc=19224 |doi=10.1073/pnas.95.4.1961 }}</ref><ref name=Jorde1997>{{cite journal |vauthors=Jorde LB, Rogers AR, Bamshad M, Watkins WS, Krakowiak P, Sung S, Kere J, Harpending HC |title=Microsatellite diversity and the demographic history of modern humans |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=94 |issue=7 |pages=3100–03 |year=1997 |pmid=9096352 |pmc=20328 |doi=10.1073/pnas.94.7.3100 }}</ref> [[Nucleotide diversity]] is based on single mutations called [[single nucleotide polymorphisms]] (SNPs). The nucleotide diversity between humans is about 0.1%, i.e. 1 difference per 1,000 [[base pair]]s.<ref name=Jorde04>{{cite journal |last1=Jorde |first1=Lynn B |last2=Wooding |first2=Stephen P |title=Genetic variation, classification and 'race' |journal=Nature Genetics |volume=36 |issue=11 Suppl |pages=S28–33 |year=2004 |pmid=15508000 |doi=10.1038/ng1435 }}</ref><ref name=Tishkoff04>{{cite journal |vauthors=Tishkoff SA, Kidd KK |title=Implications of biogeography of human populations for 'race' and medicine |journal=Nature Genetics |volume=36 |issue=11 Suppl |pages=S21–7 |year=2004 |pmid=15507999 |doi=10.1038/ng1438 }}</ref><!-- <ref>http://shrn.stanford.edu/workshops/revisitingrace/Bamshadetal2004.pdf</ref> --> A difference of 1 in 1,000 [[nucleotide]]s between two humans chosen at random amounts to about 3 million nucleotide differences, since the human genome has about 3 billion nucleotides. Most of these [[single nucleotide polymorphism]]s (SNPs) are [[Neutral theory of molecular evolution|neutral]] but some (about 3 to 5%) are functional and influence [[phenotypic]] differences between humans through [[alleles]].{{Citation needed|date=May 2015}}
 
By comparing the parts of the genome that are not under natural selection and which therefore accumulate mutations at a fairly steady rate, it is possible to reconstruct a genetic tree incorporating the entire human species since the last shared ancestor. Each time a certain mutation (SNP) appears in an individual and is passed on to his or her descendants, a [[haplogroup]] is formed including all of the descendants of the individual who will also carry that mutation. By comparing [[mtDNA|mitochondrial DNA]], which is inherited only from the mother, geneticists have concluded that the last female common ancestor whose genetic marker is found in all modern humans, the so-called [[mitochondrial Eve]], must have lived around 90,000 to 200,000 years ago.<ref name="pmid3025745">{{Citation |vauthors=Cann RL, Stoneking M, Wilson AC | title = Mitochondrial DNA and human evolution | journal = Nature | volume = 325 | issue = 6099 | pages = 31–36 | year = 1987 | pmid = 3025745 | doi = 10.1038/325031a0 | ref=harv |bibcode = 1987Natur.325...31C }}</ref><ref>{{Citation |vauthors=Soares P, Ermini L, Thomson N |title=Correcting for purifying selection: an improved human mitochondrial molecular clock |journal=Am. J. Hum. Genet. |volume=84 |issue=6 |pages=740–59 |date=June 2009 |pmid=19500773 |pmc=2694979 |doi=10.1016/j.ajhg.2009.05.001 |url=|display-authors=etal}}.
[http://www.leeds.ac.uk/news/article/245/new_molecular_clock_aids_dating_of_human_migration_history University of Leeds – New 'molecular clock' aids dating of human migration history]</ref><ref name=poz>{{cite journal |vauthors=Poznik GD, Henn BM, Yee MC, Sliwerska E, Euskirchen GM, Lin AA, Snyder M, Quintana-Murci L, Kidd JM, Underhill PA, Bustamante CD |title= Sequencing Y chromosomes resolves discrepancy in time to common ancestor of males versus females |journal= Science|volume= 341|issue=6145 | pages= 562–65 |date=August 2013|pmid=23908239|doi= 10.1126/science.1237619 |pmc=4032117}}</ref>
 
[[Human accelerated regions]], first described in August 2006,<ref name="Pollard2006">{{cite journal |vauthors=Pollard KS, Salama SR, Lambert N, Lambot MA, Coppens S, Pedersen JS, Katzman S, King B, Onodera C, Siepel A, Kern AD, Dehay C, Igel H, Ares M, Vanderhaeghen P, Haussler D |title=An RNA gene expressed during cortical development evolved rapidly in humans |journal=Nature |volume=443 |issue=7108 |pages=167–72 |year=2006 |pmid=16915236 |doi=10.1038/nature05113 }}</ref><ref name="pmid17040131">{{cite journal |vauthors=Pollard KS, Salama SR, King B, Kern AD, Dreszer T, Katzman S, Siepel A, Pedersen JS, Bejerano G, Baertsch R, Rosenbloom KR, Kent J, Haussler D |title=Forces shaping the fastest evolving regions in the human genome |journal=PLoS Genetics |volume=2 |issue=10 |pages=e168 |year=2006 |pmid=17040131 |pmc=1599772 |doi=10.1371/journal.pgen.0020168 }}</ref> are a set of 49 segments of the [[human genome]] that are conserved throughout [[vertebrate]] evolution but are strikingly different in humans. They are named according to their degree of difference between humans and their nearest animal relative ([[chimpanzee]]s) (HAR1 showing the largest degree of human-chimpanzee differences). Found by scanning through genomic databases of multiple species, some of these highly [[mutation|mutated]] areas may contribute to human-specific traits.{{Citation needed|date=May 2015}}
 
The forces of [[natural selection]] have continued to operate on human populations, with evidence that certain regions of the [[genome]] display [[directional selection]] in the past 15,000 years.<ref name="urlNYT">{{cite news |author=Wade, Nicholas |title=Still Evolving, Human Genes Tell New Story |url=https://www.nytimes.com/2006/03/07/science/07evolve.html |date=March 7, 2007 |accessdate=2012-02-13 |publisher=The New York Times}}</ref>
 
===Life cycle===
{{see also|Childbirth|Life expectancy|Human development (biology)}}
[[File:Tubal Pregnancy with embryo.jpg|thumb|120px|A 10&nbsp;mm [[human embryo]] at 5 weeks]]
{{double image|right|Redheaded child mesmerized 2.jpg|100|Burkina Faso girl.jpg|106|[[Boy]] and [[girl]] before [[puberty]]}}
{{double image|right|Da Nang, Vietnam A young Marine private waits on the beach during the Marine landing - NARA - 532432 (cropped).jpg|100|Portrait of a Persian lady in Iran, 10-08-2006 (cropped).jpg|105|[[Adolescent]] male and female}}
{{double image|right|Pataxo001.jpg|100|Punjabi woman smile.jpg|102|[[Adult]] [[man]] and [[woman]]}}
{{double image|right|Alison Phillips.jpg|105|HappyPensioneer.jpg|100|[[Elderly]] man and woman}}
 
As with other mammals, [[human reproduction]] takes place as [[internal fertilization]] by [[human sexual intercourse|sexual intercourse]]. During this process, the male inserts his [[erect penis]] into the female's [[vagina]] and [[ejaculate]]s semen, which contains sperm. The sperm travels through the vagina and cervix into the uterus or Fallopian tubes for [[human fertilization|fertilization]] of the ovum. Upon fertilization and [[Implantation (human embryo)|implantation]], gestation then occurs within the female's [[uterus]].
 
The [[zygote]] divides inside the female's uterus to become an [[embryo]], which over a period of 38 weeks (9 months) of [[gestation]] becomes a [[fetus]]. After this span of time, the fully grown fetus is [[childbirth|birthed]] from the woman's body and breathes independently as an infant for the first time. At this point, most modern cultures recognize the baby as a person entitled to the full protection of the law, though some jurisdictions extend various levels of [[personhood]] earlier to human fetuses while they remain in the uterus.
 
Compared with other species, human childbirth is dangerous. Painful labors lasting 24 hours or more are not uncommon and sometimes lead to the death of the mother, the child or both.<ref>According to the July 2: 2007 ''[[Newsweek]]'' magazine, a woman dies in childbirth every minute, most often due to uncontrolled bleeding and infection, with the world's poorest women most vulnerable. The lifetime risk is 1 in 16 in [[sub-Saharan Africa]], compared to 1 in 2,800 in [[developed countries]].</ref> This is because of both the relatively large fetal head circumference and the mother's relatively narrow [[human pelvis|pelvis]].<ref name=LaVelle1995>{{cite journal |author=LaVelle, M. |title=Natural selection and developmental sexual variation in the human pelvis |journal=American Journal of Physical Anthropology |volume=98 |issue=1 |pages=59–72 |year=1995 |pmid=8579191 |doi=10.1002/ajpa.1330980106}}</ref><ref name=Correia2005>{{cite journal |author1=Correia, H. |author2=Balseiro, S. |author3=De Areia, M. |title=Sexual dimorphism in the human pelvis: testing a new hypothesis |journal=Homo |volume=56 |issue=2 |pages=153–60 |year=2005 |pmid=16130838 |doi=10.1016/j.jchb.2005.05.003}}</ref> The chances of a successful labor increased significantly during the 20th century in wealthier countries with the advent of new medical technologies. In contrast, pregnancy and [[natural childbirth]] remain hazardous ordeals in developing regions of the world, with [[maternal death rates]] approximately 100 times greater than in developed countries.<ref name=Rush2000>{{cite journal |author=Rush, David |title=Nutrition and maternal mortality in the developing world |journal=American Journal of Clinical Nutrition |volume=72 |issue=1 Suppl |pages=212S–40S |year=2000 |pmid=10871588 |url=<!-- http://www.ajcn.org/content/72/1/212S.full -->http://ajcn.nutrition.org/content/72/1/212s.abstract}}</ref>
 
In developed countries, infants are typically {{Convert|3|-|4|kg|lb|abbr=on|lk=off|0}} in weight and {{Convert|50|-|60|cm|in|abbr=on|lk=off|0}} in height at birth.<ref>{{cite web |url=http://childinfo.org/areas/birthweight/ |title=Low Birthweight |accessdate=2007-05-30 |archiveurl=https://web.archive.org/web/20070513150431/http://www.childinfo.org/areas/birthweight/ |archivedate=May 13, 2007}}</ref>{{failed verification|date=February 2014}} However, [[low birth weight]] is common in developing countries, and contributes to the high levels of [[infant mortality]] in these regions.<ref name=Khor2003>{{cite journal |author=Khor, G. |title=Update on the prevalence of malnutrition among children in Asia |journal=Nepal Medical College Journal |volume=5 |issue=2 |pages=113–22 |year=2003 |pmid=15024783}}</ref> Helpless at birth, humans continue to grow for some years, typically reaching [[sexual maturity]] at 12 to 15&nbsp;years of age. Females continue to develop physically until around the age of 18, whereas male development continues until around age 21. The [[life expectancy|human life span]] can be split into a number of stages: infancy, [[childhood]], [[adolescence]], [[young adulthood]], [[adult]]hood and [[old age]]. The lengths of these stages, however, have varied across cultures and time periods. Compared to other primates, humans experience an unusually rapid growth spurt during adolescence, where the body grows 25% in size. Chimpanzees, for example, grow only 14%, with no pronounced spurt.<ref name=Leakey1993>{{cite book |author1=Leakey, Richard |author2=Lewin, Roger |title=Origins Reconsidered: In Search of What Makes Us Human |year=1993 |publisher=Anchor Books |location=New York, New York |isbn=978-0-385-46792-6}}</ref><!--find page # --> The presence of the growth spurt is probably necessary to keep children physically small until they are psychologically mature. Humans are one of the few species in which females undergo [[menopause]]. It has been proposed that menopause increases a woman's overall reproductive success by allowing her to invest more time and resources in her existing offspring, and in turn their children (the [[grandmother hypothesis]]), rather than by continuing to bear children into old age.<ref name=Diamond1997>{{cite book |author=Diamond, Jared |authorlink=Jared Diamond |title=Why is Sex Fun? The Evolution of Human Sexuality |publisher =Basic Books |location=New York, New York |year=1997 |pages=167–70 |isbn=0-465-03127-7}}</ref><ref name=Peccei2001>{{cite journal |last1=Peccei |first1=Jocelyn Scott |title=Menopause: Adaptation or epiphenomenon? |journal=Evolutionary Anthropology |volume=10 |issue=2 |year=2001 |pages=43–57 |doi=10.1002/evan.1013 }}</ref>
 
Evidence-based studies indicate that the life span of an individual depends on two major factors, [[genetics]] and [[lifestyle (sociology)|lifestyle]] choices.<ref name=USC>{{Cite news|first=Carl|last=Marziali|date=7 December 2010|title=Reaching Toward the Fountain of Youth|url=http://uscnews.usc.edu/health/reaching_toward_the_fountain_of_youth.html|work=USC Trojan Family Magazine|accessdate=7 December 2010}}</ref> For various reasons, including biological/genetic causes,<ref>{{cite web |last=Kalben |first=Barbara Blatt |title=Why Men Die Younger: Causes of Mortality Differences by Sex |publisher= Society of Actuaries |year= 2002 |url=http://www.soa.org/news-and-publications/publications/other-publications/monographs/m-li01-1-toc.aspx}}</ref> women live on average about four years longer than men—as of 2013 the global average [[life expectancy at birth]] of a girl is estimated at 70.2 years compared to 66.1 for a boy.<ref name=CIA-world>{{cite web|title=CIA World Factbook – World entry|url=https://www.cia.gov/library/publications/the-world-factbook/geos/xx.html|work=Central Intelligence Agency|accessdate=5 July 2013}}</ref> There are significant geographical variations in human life expectancy, mostly correlated with economic development—for example life expectancy at birth in [[Hong Kong]] is 84.8&nbsp;years for girls and 78.9 for boys, while in [[Swaziland]], primarily because of [[AIDS]], it is 31.3&nbsp;years for both sexes.<ref>[http://hdr.undp.org/hdr2006/ "Human Development Report 2006,"] {{webarchive|url=https://web.archive.org/web/20071011205535/http://hdr.undp.org/hdr2006/ |date=2007-10-11 }} [[United Nations Development Programme]], pp. 363–66, November 9, 2006</ref> The developed world is generally aging, with the median age around 40&nbsp;years. In the [[third world|developing world]] the median age is between 15 and 20&nbsp;years. While one in five Europeans is 60&nbsp;years of age or older, only one in twenty Africans is 60&nbsp;years of age or older.<ref>[https://www.cia.gov/library/publications/the-world-factbook/ ''The World Factbook''], U.S. Central Intelligence Agency. Retrieved April 2, 2005.</ref> The number of [[centenarian]]s (humans of age 100&nbsp;years or older) in the world was estimated by the [[United Nations]] at 210,000 in 2002.<ref>{{cite web |url=https://www.un.org/ageing/note5713.doc.htm |title=U.N. Statistics on Population Ageing |publisher=United Nations |date=February 28, 2002 |accessdate=April 2, 2005 |archiveurl=https://web.archive.org/web/20051208122227/http://www.un.org/ageing/note5713.doc.htm |archivedate=2005-12-08}}</ref> At least one person, [[Jeanne Calment]], is known to have reached the age of 122&nbsp;years;<ref name=Maier2010>{{cite book |author=Maier, Heiner |title=Supercentenarians |year=2010 |publisher=Springer |location=Heidelberg, Germany |isbn=978-3-642-11519-6 |page=288 |url=https://books.google.com/books?id=0Fjkhcn3oeIC&pg=PA288}}</ref> higher ages have been claimed but they are not well substantiated.
 
===Diet===
{{Main article|Human nutrition}}
[[File:Preparing The Feast.jpg|thumb|Humans living in [[Bali]], [[Indonesia]] preparing a meal.]]
{{double image|right|Venus of Willendorf frontview retouched 2.jpg|120|Fridtjof Nansen, Les deux étapes de la faim (1922).jpg|120|[[Venus of Willendorf]] statuette from the [[Upper Palaeolithic]] period|Two starved boys during the [[Russian famine of 1921–22]]}}
 
Humans are [[omnivorous]], capable of consuming a wide variety of plant and animal material.<ref>{{cite journal |author=Haenel H |title=Phylogenesis and nutrition |journal=Nahrung |volume=33 |issue=9 |pages=867–87 |year=1989 |pmid=2697806}}</ref><ref>{{cite book|editor=Peter S. Ungar|year=2007|author=Cordain, Loren|title=Evolution of the human diet: the known, the unknown and the unknowable|chapter=Implications of Plio-pleistocene diets for modern humans|quote="Since the evolutionary split between hominins and [[pongids]] approximately 7 million years ago, the available evidence shows that all species of hominins ate an omnivorous diet composed of minimally processed, wild-plant, and animal foods.|pages=264–65}}</ref> Varying with available food sources in regions of habitation, and also varying with cultural and religious norms, human groups have adopted a range of diets, from purely [[vegetarian]] to primarily [[carnivorous]]. In some cases, dietary restrictions in humans can lead to [[deficiency diseases]]; however, stable human groups have adapted to many dietary patterns through both genetic specialization and cultural conventions to use nutritionally balanced food sources.<ref>{{cite journal| journal=Journal of the American Dietetic Association| year=2003| volume=103| issue=6| pages=748–65| title=Vegetarian Diets| doi=10.1053/jada.2003.50142| pmid=12778049| last1=American Dietetic| first1=Association| last2=Dietitians Of| first2=Canada}}<!-- [http://www.eatright.org/cps/rde/xchg/ada/hs.xsl/advocacy_933_ENU_HTML.htm online copy available] --></ref> The human diet is prominently reflected in human culture, and has led to the development of [[food science]].
 
Until the development of agriculture approximately 10,000 years ago, ''Homo sapiens'' employed a hunter-gatherer method as their sole means of food collection. This involved combining stationary food sources (such as fruits, grains, tubers, and mushrooms, insect larvae and aquatic mollusks) with [[Game (food)|wild game]], which must be hunted and killed in order to be consumed.<ref>{{cite journal |author=Cordain L |title=Origins and evolution of the Western diet: health implications for the 21st century |journal=Am. J. Clin. Nutr. |volume=81 |issue=2 |pages=341–54 |date=February 2005 |pmid=15699220 |name-list-format=vanc|author2=Eaton SB |author3=Sebastian A |display-authors=3 |last4=Mann |first4=N |last5=Lindeberg |first5=S |last6=Watkins |first6=BA |last7=O'Keefe |first7=JH |last8=Brand-Miller |first8=J}}</ref> It has been proposed that humans have used fire to prepare and [[cooking|cook]] food since the time of ''[[Homo erectus]]''.<ref>{{cite journal |author=Ulijaszek SJ |title=Human eating behaviour in an evolutionary ecological context |journal=Proc Nutr Soc |volume=61 |issue=4 |pages=517–26 |date=November 2002 |pmid=12691181 |doi=10.1079/PNS2002180}}</ref> Around ten thousand years ago, [[History of agriculture|humans developed agriculture]],<ref>[http://www.archaeology.org/9707/newsbriefs/squash.html Earliest agriculture in the Americas]
[http://sciencenow.sciencemag.org/cgi/content/full/2007/213/2 Earliest cultivation of barley] {{webarchive |url=https://web.archive.org/web/20070216093200/http://sciencenow.sciencemag.org/cgi/content/full/2007/213/2 |date=February 16, 2007 }}
[http://news.bbc.co.uk/2/hi/science/nature/5038116.stm Earliest cultivation of figs] – URLs retrieved February 19, 2007</ref> which substantially altered their diet. This change in diet may also have altered human biology; with the spread of [[dairy farming]] providing a new and rich source of food, leading to the evolution of the ability to digest [[lactose]] in some adults.<ref>{{cite journal |author=Krebs JR |title=The gourmet ape: evolution and human food preferences |journal=Am. J. Clin. Nutr. |volume=90 |issue=3 |pages=707S–11S |date=September 2009 |pmid=19656837 |doi=10.3945/ajcn.2009.27462B}}</ref><ref>{{cite journal |vauthors=Holden C, Mace R |title=Phylogenetic analysis of the evolution of lactose digestion in adults |journal=Hum. Biol. |volume=69 |issue=5 |pages=605–28 |date=October 1997 |pmid=9299882 }}</ref> Agriculture led to increased populations, the development of cities, and because of increased population density, the wider spread of [[infectious disease]]s. The types of food consumed, and the way in which they are prepared, have varied widely by time, location, and culture.
 
In general, humans can survive for two to eight weeks without food, depending on stored body fat. Survival without water is usually limited to three or four days. About 36 million humans die every year from causes directly or indirectly related to starvation.<ref>[[United Nations]] Information Service. [http://www.fao.org/righttofood/kc/downloads/vl/docs/Rtf%20hearing%2031%2003%202004.doc "Independent Expert On Effects Of Structural Adjustment, Special Rapporteur On Right To Food Present Reports: Commission Continues General Debate On Economic, Social And Cultural Rights"] {{webarchive|url=https://web.archive.org/web/20090327010027/http://www.fao.org/righttofood/kc/downloads/vl/docs/Rtf%20hearing%2031%2003%202004.doc |date=2009-03-27 }}. [[United Nations]], March 29, 2004, p. 6. "Around 36 million people died from hunger directly or indirectly every year.".</ref> Childhood malnutrition is also common and contributes to the [[Disease burden|global burden of disease]].<ref>{{cite journal |vauthors=Murray C, Lopez A | title = Global mortality, disability, and the contribution of risk factors: Global Burden of Disease Study | journal = Lancet | volume = 349 | issue = 9063 | pages = 1436–42 | year = 1997 | pmid = 9164317 | doi = 10.1016/S0140-6736(96)07495-8}}</ref> However global food distribution is not even, and [[obesity]] among some human populations has increased rapidly, leading to health complications and increased mortality in some [[developed country|developed]], and a few [[developing countries]]. Worldwide over one billion people are obese,<ref name=Haslam>{{cite journal |vauthors=Haslam DW, James WP |title=Obesity |journal=Lancet |volume=366 |issue=9492 |pages=1197–209 |date=October 2005 |pmid=16198769 |doi=10.1016/S0140-6736(05)67483-1 }}</ref> while in the United States 35% of people are obese, leading to this being described as an "[[Epidemiology of obesity|obesity epidemic]]."<ref name=Catenacci>{{cite journal |vauthors=Catenacci VA, Hill JO, Wyatt HR |title=The obesity epidemic |journal=Clin. Chest Med. |volume=30 |issue=3 |pages=415–44, vii |date=September 2009 |pmid=19700042 |doi=10.1016/j.ccm.2009.05.001 }}</ref> Obesity is caused by consuming more [[calorie]]s than are expended, so excessive weight gain is usually caused by an energy-dense diet.<ref name=Haslam/>
 
===Biological variation===
{{Main article|Human genetic variation}}
[[File:Maasai tribe.jpg|thumb|right|People in hot climates are often slender and dark skinned, such as these [[Maasai people|Maasai]] men from [[Kenya]].]]
[[File:Inuit Amautiq 1995-06-15.jpg|thumb|right|People in cold climates tend to be lighter skinned such as these [[Inuit]] women from [[Canada]].]]
 
No two humans—not even [[monozygotic twins]]—are genetically identical. [[Gene]]s and [[Environment (biophysical)|environment]] influence human biological variation from visible characteristics to physiology to disease susceptibly to mental abilities. The exact influence of [[Environment (biophysical)|genes and environment]] on certain traits is not well understood.<ref>{{Cite journal|last=Edwards |first=JH |author2=T Dent |author3=J Kahn |title=Monozygotic twins of different sex |journal=Journal of Medical Genetics |volume=3 |issue=2 |pages=117–23 |date=June 1966 |pmid=6007033 |pmc=1012913 |doi= 10.1136/jmg.3.2.117|url= |accessdate=}}</ref><ref>{{Cite journal|last=Machin |first=GA |title=Some causes of genotypic and phenotypic discordance in monozygotic twin pairs |journal=American Journal of Medical Genetics |volume=61 |issue=3 |pages=216–28 |date=January 1996 |pmid=8741866 |doi=10.1002/(SICI)1096-8628(19960122)61:3<216::AID-AJMG5>3.0.CO;2-S |url= |accessdate=}}</ref>
 
Most current [[Heredity|genetic]] and [[archaeological]] evidence supports a recent single [[Recent African origin of modern humans|origin of modern humans]] in [[East Africa]],<ref name=Liu>{{cite journal |author1=Liu, Hua |author2=Prugnolle, Franck |author3=Manina, Andrea |author4=Balloux, François |title=A geographically explicit genetic model of worldwide human-settlement history  |journal=The American Journal of Human Genetics |volume=79 |issue=2 |pages=230–37 |year=2006 |pmid=16826514 |pmc=1559480 |doi=10.1086/505436}}</ref> with first migrations placed at 60,000 years ago. Compared to the [[great apes]], [[Population bottleneck|human gene sequences]]—even among [[Africa]]n populations—are [[Human genetic variation|remarkably homogeneous]].<ref name=REGWG2005>{{cite journal |author1=Race, Ethnicity |author2=Genetics Working Group |title=The use of racial, ethnic, and ancestral categories in human genetics research |journal=American Journal of Human Genetics |volume=77 |issue=4 |pages=519–32 |year=2005 |pmid=16175499 |pmc=1275602 |doi=10.1086/491747}}</ref> On average, genetic similarity between any two humans is 99.9%.<ref>{{cite web|last=Dr. Shafer|first=Aaron|title=Understanding Genetics|url=http://genetics.thetech.org/ask/ask166|work=The Tech|publisher=Stanford University|accessdate=13 December 2013|quote=The DNA sequence in your genes is on average 99.9% identical to ANY other human being.}}</ref><ref>{{cite web|title=Genetic – Understanding Human Genetic Variation |url=http://science.education.nih.gov/supplements/nih1/genetic/guide/genetic_variation1.htm |work=Human Genetic Variation |publisher=National Institute of Health (NIH) |accessdate=13 December 2013 |quote=Between any two humans, the amount of genetic variation—biochemical individuality—is about 0.1%. |deadurl=yes |archiveurl=https://web.archive.org/web/20130825143543/http://science.education.nih.gov/supplements/nih1/genetic/guide/genetic_variation1.htm |archivedate=25 August 2013 |df= }}</ref> There is about 2–3 times more genetic diversity within the wild chimpanzee population, than in the entire [[human gene pool]].<ref name=pbs1>{{cite web|title=Human Diversity – Go Deeper|url=http://www.pbs.org/race/000_About/002_04-background-01-11.htm|work=Power of an Illusion|publisher=PBS|accessdate=6 January 2013}}</ref><ref name=oxf>{{cite web|title=Chimps show much greater genetic diversity than humans |url=http://www.ox.ac.uk/media/news_stories/2012/120302.html |work=Media |publisher=University of Oxford |accessdate=13 December 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20131218091207/http://www.ox.ac.uk/media/news_stories/2012/120302.html |archivedate=18 December 2013 |df= }}</ref><ref name="roberts1">{{cite book|last=Roberts|first=Dorothy|title=Fatal Invention|year=2011|publisher=The New Press|location=London, New York}}</ref>
 
The human body's ability to [[Adaptation|adapt]] to different environmental stresses is remarkable, allowing humans to acclimatize to a wide variety of [[temperature]]s, [[humidity]], and [[altitude]]s. As a result, humans are a cosmopolitan species found in almost all regions of the world, including [[tropical rainforest]]s, [[desert|arid desert]], extremely cold [[arctic region]]s, and heavily polluted [[cities]]. Most other species are confined to a few geographical areas by their limited adaptability.<ref name=adapt1>{{cite web|last=O'Neil |first=Dennis |title=Human Biological Adaptability; Overview |url=http://anthro.palomar.edu/adapt/adapt_1.htm |publisher=Palomar College |accessdate=6 January 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20130306124405/http://anthro.palomar.edu/adapt/adapt_1.htm |archivedate=6 March 2013 |df= }}</ref>
 
There is biological variation in the human species—with traits such as [[blood type]], [[Cranial capacity|cranial features]], [[eye color]], [[hair color]] and type, [[Human height|height]] and [[Body type|build]], and [[Human skin color|skin color]] varying across the globe. Human body types vary substantially. The typical height of an adult human is between {{Convert|1.4|and|1.9|m|ftin|abbr=on}}, although this varies significantly depending, among other things, on [[sex]] and [[ethnic origin]].<ref name=adapt2>{{cite web|last=O'Neil|first=Dennis|title=Adapting to Climate Extremes|url=http://anthro.palomar.edu/adapt/adapt_2.htm|work=Human Biological Adaptability|publisher=Palomar College|accessdate=6 January 2013}}</ref><ref>{{cite journal | author = de Beer H | title = Observations on the history of Dutch physical stature from the late-Middle Ages to the present | journal = Econ Hum Biol | volume = 2 | issue = 1 | pages = 45–55 | year = 2004 | pmid = 15463992 | doi = 10.1016/j.ehb.2003.11.001}}</ref> Body size is partly determined by genes and is also significantly influenced by environmental factors such as [[diet (nutrition)|diet]], [[exercise]], and [[sleep pattern]]s, especially as an influence in [[childhood]]. Adult height for each sex in a particular ethnic group approximately follows a [[normal distribution]]. Those aspects of genetic variation that give clues to human evolutionary history, or are relevant to medical research, have received particular attention. For example, the genes that allow adult humans to [[Lactose tolerance|digest lactose]] are present in high frequencies in populations that have long histories of cattle domestication, suggesting natural selection having favored that gene in populations that depend on [[cow milk]]. Some hereditary diseases such as [[sickle cell anemia]] are frequent in populations where [[malaria]] has been endemic throughout history—it is believed that the same gene gives increased resistance to malaria among those who are unaffected carriers of the gene. Similarly, populations that have for a long time inhabited specific climates, such as arctic or tropical regions or high altitudes, tend to have developed specific phenotypes that are beneficial for conserving energy in those environments—[[Allen's rule|short stature and stocky build in cold regions]], tall and lanky in hot regions, and with high lung capacities at high altitudes. Similarly, skin color varies [[Clinal variation|clinally]] with darker skin around the equator—where the added protection from the sun's ultraviolet radiation is thought to give an evolutionary advantage—and lighter skin tones closer to the poles.<ref name="Hedrick 2011">{{Cite journal |author=Hedrick PW |title=Population genetics of malaria resistance in humans |journal=Heredity |year=2011 |volume=107 |issue=4 |pages=283–304 |pmid=21427751 |doi=10.1038/hdy.2011.16 |pmc=3182497}} {{open access}}</ref><ref name="Weatherall 2008">{{cite journal |author=Weatherall DJ |title=Genetic variation and susceptibility to infection: The red cell and malaria |journal=British Journal of Haematology |year=2008 |volume=141 |issue=3 |pages=276–86 |doi=10.1111/j.1365-2141.2008.07085.x |pmid=18410566}}</ref><ref>{{cite journal  |vauthors=Beja-Pereira A, etal | year = 2003 | title = Gene-culture coevolution between cattle milk protein genes and human lactase genes | url = | journal = Nat Genet | volume = 35 | issue = | pages = 311–13 | doi=10.1038/ng1263}}</ref><ref name=jabl04>{{cite journal|last=Nina|first=Jablonski|title=The evolution of human skin and skin color|journal=Annual Review of Anthropology|year=2004|volume=33|pages=585–623|doi=10.1146/annurev.anthro.33.070203.143955}}</ref>
 
The hue of human skin and hair is determined by the presence of [[pigment]]s called [[melanin]]s. Human skin color can range from [[Dark skin|darkest brown]] to [[Light skin|lightest peach]], or even nearly white or colorless in cases of [[albinism]].<ref name="roberts1"/> Human hair ranges in color from [[White hair|white]] to [[Red hair|red]] to [[blond]] to [[Brown hair|brown]] to [[Black hair|black]], which is most frequent.<ref>{{cite journal | author1=Rogers, Alan R.|author2=Iltis, David|author3= Wooding, Stephen | year=2004 | title=Genetic variation at the MC1R locus and the time since loss of human body hair | journal=Current Anthropology | volume=45 | issue=1 | pages=105–08 | doi=10.1086/381006}}</ref> Hair color depends on the amount of melanin (an effective sun blocking pigment) in the [[Human skin|skin]] and hair, with hair melanin concentrations in hair fading with increased age, leading to [[Grey hair|grey]] or even white hair. Most researchers believe that skin darkening is an adaptation that evolved as protection against ultraviolet solar radiation, which also helps balancing [[folate]], which is destroyed by [[ultraviolet radiation]]. Light skin pigmentation protects against depletion of [[vitamin D]], which requires [[sunlight]] to make.<ref>Jablonski, N.G. & Chaplin, G. (2000). ''[http://www.bgsu.edu/departments/chem/faculty/leontis/chem447/PDF_files/Jablonski_skin_color_2000.pdf The evolution of human skin coloration] {{webarchive|url=https://web.archive.org/web/20120114203210/http://www.bgsu.edu/departments/chem/faculty/leontis/chem447/PDF_files/Jablonski_skin_color_2000.pdf |date=2012-01-14 }}'' (pdf), 'Journal of Human Evolution 39: 57–106.</ref> Skin pigmentation of contemporary humans is clinally distributed across the planet, and in general correlates with the level of ultraviolet radiation in a particular geographic area. Human skin also has a capacity to darken (tan) in response to exposure to ultraviolet radiation.<ref>{{cite journal |author=Harding RM |title=Evidence for variable selective pressures at MC1R |journal=Am. J. Hum. Genet. |volume=66 |issue=4 |pages=1351–61 |date=April 2000 |pmid=10733465 |pmc=1288200 |doi=10.1086/302863 |url= |name-list-format=vanc|author2=Healy E |author3=Ray AJ |display-authors=3 |last4=Ellis |first4=Nichola S. |last5=Flanagan |first5=Niamh |last6=Todd |first6=Carol |last7=Dixon |first7=Craig |last8=Sajantila |first8=Antti |last9=Jackson |first9=Ian J.}}</ref><ref>Robin, Ashley (1991). ''Biological Perspectives on Human Pigmentation''. Cambridge: Cambridge University Press.</ref><ref name="jabl1">{{cite book|last=Muehlenbein|first=Michael|title=Human Evolutionary Biology|year=2010|publisher=Cambridge University Press|pages=192–213}}</ref>
 
====Structure of variation====
 
[[File:Seti1a.jpg|thumb|A [[Berbers|Libyan]], a [[Nubians|Nubian]], a [[Syrian people|Syrian]], and an [[Egyptians|Egyptian]], drawing by an unknown artist after a mural of the tomb of [[Seti I]].]]
[[File:Yanomami Woman & Child.jpg|thumb|The ancestors of [[indigenous peoples of the Americas|Native Americans]], such as this [[Yanomami]] woman, crossed into the Americas from Northeast Asia, and genetic and linguistic evidence links them to North Asian populations, particularly those of [[Indigenous peoples of Siberia|East Siberia]].<ref>{{cite web|title=Journey of Mankind|url=http://www.bradshawfoundation.com/journey/|work=Peopling of the World|publisher=Bradshaw Foundation|accessdate=10 August 2013}}</ref> ]]
[[File:Paris - Playing chess at the Jardins du Luxembourg - 2966.jpg|thumb|An older adult human male European in Paris – playing chess at the Jardins du Luxembourg.]]
Within the human species, the greatest degree of genetic [[Sex differences in humans|variation exists between males and females]]. While the [[nucleotide diversity|nucleotide]] genetic variation of individuals of the same sex across global populations is no greater than 0.1%, the genetic difference between [[Man|males]] and [[woman|females]] is between 1% and 2%. Although different in nature{{clarify|date=May 2014}}, this approaches the genetic differentiation between men and male chimpanzees or women and female chimpanzees. The genetic difference between sexes contributes to anatomical, hormonal, neural, and physiological differences between men and women, although the exact degree and nature of social and environmental influences on sexes are not completely understood. Males on average are 15% heavier and {{Convert|15|cm|in|abbr=on|lk=off|0}} taller than females. There is a difference between body types, body organs and systems, hormonal levels, sensory systems, and muscle mass between sexes. On average, there is a difference of about 40–50% in upper body strength and 20–30% in lower body strength between men and women. Women generally have a higher [[body fat]] percentage than men. Women have [[Human skin color#sexual dimorphism|lighter skin]] than men of the same population; this has been explained by a higher need for vitamin D (which is synthesized by sunlight) in females during [[pregnancy]] and [[lactation]]. As there are chromosomal differences between females and males, some X and Y chromosome related conditions and [[Disease|disorders]] only affect either men or women. Other conditional differences between males and females are not related to sex chromosomes. Even after allowing for body weight and volume, the male [[voice]] is usually an [[octave]] deeper than the female voice. Women have a [[Life expectancy#Sex differences|longer life span]] in almost every population around the world.<ref name="Birke, Lydia 2001">Birke, Lydia. The Gender and Science Reader ed. Muriel Lederman and Ingrid Bartsch. New York, Routledge, 2001. 306–22</ref><ref name="Gustafsson">{{cite journal |vauthors=Gustafsson A, Lindenfors P| year=2004 | title=Human size evolution: no allometric relationship between male and female stature | journal=Journal of Human Evolution | volume=47 | pages=253–66 | doi=10.1016/j.jhevol.2004.07.004 | pmid=15454336 | issue=4}}</ref><ref>''Dominance and the evolution of sexual dimorphism in human voice pitch'' Puts, David Andrew and Gaulin, Steven J.C and Verdolini, Katherine; Evolution and Human Behavior, {{ISSN|1090-5138}}, 2006, Volume 27, Issue 4, pp. 283–96</ref><ref name="NHANES_III_data">{{cite web|url=http://www.cdc.gov/nchs/data/ad/ad347.pdf |title=Ogden et al (2004). Mean Body Weight, Height, and Body Mass Index, United States 1960–2002 ''Advance Data from Vital and Health Statistics'', Number 347, October 27, 2004. |format=PDF |accessdate=2013-07-27}}</ref><ref name="Stephens">{{cite web |url=http://home.hia.no/~stephens/gender.htm |title=Gender Differences in Endurance Performance and Training |archiveurl=https://web.archive.org/web/20100127173555/http://home.hia.no/~stephens/gender.htm |archivedate=2010-01-27}}</ref><ref>{{cite journal | doi = 10.1007/BF00235103 | last1 = Miller | first1 = AE | last2 = MacDougall | first2 = JD | last3 = Tarnopolsky | first3 = MA | last4 = Sale | first4 = DG | title = Gender differences in strength and muscle fiber characteristics | journal = European journal of applied physiology and occupational physiology | volume = 66 | issue = 3 | pages = 254–62 | year = 1993 | pmid = 8477683 }}</ref><ref>{{cite news| url=http://news.bbc.co.uk/1/hi/health/1796447.stm | work=BBC News | title=Women nose ahead in smell tests | date=2002-02-04 | accessdate=2010-05-23}}</ref><ref>{{cite web|url=http://www.sciencedaily.com/releases/2005/10/051025073319.htm |title=Study Reveals Reason Women Are More Sensitive To Pain Than Men |publisher=Sciencedaily.com |date=2005-10-25 |accessdate=2013-07-27}}</ref><ref name="WHO">[http://www.who.int/gender/documents/en/ Gender, women, and health] Reports from WHO 2002–2005</ref>{{citekill|date=July 2017}}
 
Males typically have larger [[Vertebrate trachea|tracheae]] and branching [[Bronchus|bronchi]], with about 30% greater [[Lung volumes|lung volume]] per unit [[body mass]]. They have larger [[heart]]s, 10% higher [[red blood cell]] count, and higher [[hemoglobin]], hence greater oxygen-carrying capacity. They also have higher circulating [[Coagulation|clotting factors]] ([[vitamin K]], pro[[thrombin]] and [[platelet]]s). These differences lead to faster healing of [[wound]]s and higher peripheral pain tolerance.<ref name="Glucksman">{{cite book |author=Alfred Glucksman |year=1981 |title=Sexual Dimorphism in Human and Mammalian Biology and Pathology |publisher=[[Academic Press]] |isbn=978-0-12-286960-0 |pages=66–75 |oclc=7831448 }}</ref> Females typically have more [[white blood cell]]s (stored and circulating), more [[granulocyte]]s and B and T [[lymphocyte]]s. Additionally, they produce more [[Antibody|antibodies]] at a faster rate than males. Hence they develop fewer [[Infection|infectious]] diseases and these continue for shorter periods.<ref name="Glucksman" /> [[Ethology|Ethologists]] argue that females, interacting with other females and multiple offspring in social groups, have experienced such traits as a [[Natural selection|selective]] advantage.<ref>{{cite book |author1=Jo Durden-Smith |author2=Diane deSimone |year=1983 |title=Sex and the Brain |location=New York |publisher=[[Arbor House]] |isbn=978-0-87795-484-2}}</ref><ref>{{cite book |first1=Eileen S. | last1=Gersh |first2= Isidore |last2=Gersh |year=1981 |title=Biology of Women |location= Baltimore |publisher=University Park Press (original from the University of Michigan) |isbn=978-0-8391-1622-6 }}</ref><ref>{{cite book |author=Jay H. Stein |year=1987 |title=Internal Medicine |publisher=[[Little, Brown]] |location=Boston |isbn=978-0-316-81236-8 |edition=2nd}}</ref><ref>{{cite journal |author1=M. McLaughlin |author2=T. Shryer |title=Men vs women: the new debate over sex differences |journal=[[U.S. News & World Report]] |date=8 August 1988 |pages=50–58}}</ref><ref>{{cite journal |author=B. S. McEwen |year=1981 |title=Neural gonadal steroid actions |journal=[[Science (journal)|Science]] |volume=211 |issue=4488 |pages=1303–11 |pmid=6259728 |doi=10.1126/science.6259728|bibcode = 1981Sci...211.1303M }}</ref> According to Daly and Wilson, "The sexes differ more in human beings than in [[monogamous]] mammals, but much less than in extremely [[polygamous]] mammals."<ref>{{cite book |author1=Martin Daly |author2=Margo Wilson |year=1996 |chapter=Evolutionary psychology and marital conflict |title=Sex, Power, Conflict: Evolutionary and Feminist Perspectives |editor=[[David M. Buss]] & Neil M. Malamuth |publisher=[[Oxford University Press]] |page=13 |isbn=978-0-19-510357-1}}</ref> But given that [[sexual dimorphism]] in the closest relatives of humans is much greater than among humans, the human clade must be considered to be characterized by decreasing sexual dimorphism, probably due to less competitive mating patterns. One proposed explanation is that human sexuality has developed more in common with its close relative the [[bonobo]], which exhibits similar sexual dimorphism, is [[Polygynandry|polygynandrous]] and uses [[recreational sex]] to reinforce social bonds and reduce aggression.<ref>{{Cite book |author1=Christopher Ryan |author2=Cacilda Jethá |year=2010 |title=[[Sex at Dawn|Sex at Dawn: The Prehistoric Origins of Modern Sexuality]] |publisher=Harper |isbn=978-0-06-170780-3}}</ref>
 
Humans of the same sex are 99.9% genetically identical. There is extremely little variation between human geographical populations, and most of the variation that does occur is at the personal level within local areas, and not between populations.<ref name="roberts1"/><ref name=hgp>{{cite web|title=The Science Behind the Human Genome Project|url=http://www.ornl.gov/sci/techresources/Human_Genome/project/info.shtml|work=Human Genome Project|publisher=US Department of Energy|accessdate=6 January 2013|quote=Almost all (99.9%) nucleotide bases are exactly the same in all people.}}</ref><ref name=enr1>{{cite web|last=O'Neil|first=Dennis|title=Ethnicity and Race: Overview|url=http://anthro.palomar.edu/ethnicity/ethnic_1.htm#return_from_ethnic_identity_question|publisher=Palomar College|accessdate=6 January 2013}}</ref> Of the 0.1% of human genetic differentiation, 85% exists within any randomly chosen local population, be they Italians, Koreans, or Kurds. Two randomly chosen Koreans may be genetically as different as a Korean and an Italian. Any ethnic group contains 85% of the human genetic diversity of the world. Genetic data shows that no matter how population groups are defined, two people from the same population group are about as different from each other as two people from any two different population groups.<ref name="roberts1"/><ref>{{cite web|title=Genetic – Understanding Human Genetic Variation |url=http://science.education.nih.gov/supplements/nih1/genetic/guide/genetic_variation1.htm |work=Human Genetic Variation |publisher=National Institute of Health (NIH) |accessdate=13 December 2013 |quote=In fact, research results consistently demonstrate that about 85 percent of all human genetic variation exists within human populations, whereas about only 15 percent of variation exists between populations. |deadurl=yes |archiveurl=https://web.archive.org/web/20130825143543/http://science.education.nih.gov/supplements/nih1/genetic/guide/genetic_variation1.htm |archivedate=25 August 2013 |df= }}</ref><ref name="goodman1">{{cite web|last=Goodman|first=Alan|title=Interview with Alan Goodman|url=http://www.pbs.org/race/000_About/002_04-background-01-07.htm|work=Race Power of and Illusion|publisher=PBS|accessdate=6 January 2013}}</ref><ref>Marks, J. (2010) Ten facts about human variation. In: Human Evolutionary Biology, edited by M. Muehlenbein. New York: Cambridge University Press {{cite web|url=http://personal.uncc.edu/jmarks/pubs/tenfacts.pdf |title=Archived copy |accessdate=2013-09-05 |deadurl=yes |archiveurl=https://web.archive.org/web/20120415012646/http://personal.uncc.edu/jmarks/pubs/tenfacts.pdf |archivedate=2012-04-15 |df= }}</ref>
 
Current genetic research has demonstrated that humans on the [[African continent]] are the most genetically diverse.<ref name=Jorde2000>{{cite journal |author1=Jorde, L. |author2=Watkins, W |author3=Bamshad, M |author4=Dixon, M |author5=Ricker, C. |author6=Seielstad, M. |author7=Batzer, M. |title=The distribution of human genetic diversity: a comparison of mitochondrial, autosomal, and Y-chromosome data |journal=American Journal of Human Genetics |volume=66 |issue=3 |pages=979–88 |year=2000 |pmc=1288178 |pmid=10712212 |doi=10.1086/302825}}</ref> There is more human genetic diversity in Africa than anywhere else on Earth. The genetic structure of Africans was traced to 14 ancestral population clusters. Human genetic diversity decreases in native populations with migratory distance from Africa and this is thought to be the result of [[Evolutionary bottleneck|bottlenecks]] during human migration.<ref name="sciencedaily.com">
{{cite web
|date=19 July 2007
|title=New Research Proves Single Origin Of Humans In Africa
|url=http://www.sciencedaily.com/releases/2007/07/070718140829.htm
|publisher=[[Science Daily]]
|accessdate=2011-09-05
}}</ref><ref>
{{cite journal
|last1=Manica |first1=A
|last2=Amos |first2=W
|last3=Balloux |first3=F
|last4=Hanihara |first4=T
|year=2007
|title=The effect of ancient population bottlenecks on human phenotypic variation
|journal=[[Nature (journal)|Nature]]
|volume=448 |issue=7151 |pages=346–48
|bibcode=2007Natur.448..346M
|doi=10.1038/nature05951
|pmc=1978547
|pmid=17637668
}}</ref> Humans have lived in Africa for the longest time, which has allowed accumulation of a higher diversity of genetic mutations in these populations. Only part of Africa's population migrated out of the continent, bringing just part of the original African genetic variety with them. African populations harbor genetic alleles that are not found in other places of the world. All the common alleles found in populations outside of Africa are found on the African continent.<ref name="roberts1"/>
 
Geographical distribution of human variation is complex and constantly shifts through time which reflects complicated human evolutionary history. Most human biological variation is [[Cline (biology)|clinally]] distributed and blends gradually from one area to the next. Groups of people around the world have different frequencies of [[Polymorphism (biology)|polymorphic]] genes. Furthermore, different traits are non-concordant and each have different clinal distribution. Adaptability varies both from person to person and from population to population. The most efficient adaptive responses are found in geographical populations where the environmental stimuli are the strongest (e.g. [[Tibetan people|Tibetans]] are highly adapted to high altitudes). The clinal geographic genetic variation is further complicated by the migration and mixing between human populations which has been occurring since prehistoric times.<ref name="roberts1"/><ref name=adapt3>{{cite web|last=O'Neil |first=Dennis |title=Adapting to High Altitude |url=http://anthro.palomar.edu/adapt/adapt_3.htm |work=Human Biological Adaptability |publisher=Palomar College |accessdate=6 January 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20130106210055/http://anthro.palomar.edu/adapt/adapt_3.htm |archivedate=6 January 2013 |df= }}</ref><ref name=adapt03>{{cite web|last=O'Neil |first=Dennis |title=Overview |url=http://anthro.palomar.edu/adapt/adapt_1.htm |work=Human Biological Adaptability |publisher=Palomar College |accessdate=6 January 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20130306124405/http://anthro.palomar.edu/adapt/adapt_1.htm |archivedate=6 March 2013 |df= }}</ref><ref name="vary02">{{cite web|last=O'Neil |first=Dennis |title=Models of Classification |url=http://anthro.palomar.edu/vary/vary_2.htm |work=Modern Human Variation |publisher=Palomar College |accessdate=6 January 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20130106212400/http://anthro.palomar.edu/vary/vary_2.htm |archivedate=6 January 2013 |df= }}</ref><ref name="pbsmarks1">{{cite web|last=Marks|first=Jonathan|title=Interview with Jonathan Marks|url=http://www.pbs.org/race/000_About/002_04-background-01-08.htm|work=Race – The Power of an Illusion|publisher=PBS|accessdate=6 January 2013}}</ref><ref name="pbsgoodman1">{{cite web|last=Goodman|first=Alan|title=Background Readings|url=http://www.pbs.org/race/000_About/002_04-background-01-10.htm|work=Race – Power of an Illusion|publisher=PBS|accessdate=6 January 2013}}</ref>{{citekill|date=July 2017}}
 
Human variation is highly non-concordant: most of the genes do not cluster together and are not inherited together. Skin and hair color are not correlated to height, weight, or athletic ability. Human species do not share the same patterns of variation through geography. Skin color varies with latitude and certain people are tall or have brown hair. There is a statistical correlation between particular features in a population, but different features are not expressed or inherited together. Thus, genes which code for superficial physical traits—such as skin color, hair color, or height—represent a minuscule and insignificant portion of the human genome and do not correlate with genetic affinity. Dark-skinned populations that are found in Africa, Australia, and South Asia are not closely related to each other.<ref name="jabl1"/><ref name="pbsmarks1"/><ref name="pbsgoodman1"/><ref name=jablo04>{{cite journal|last=Nina|first=Jablonski|title=The evolution of human skin and skin color|quote=genetic evidence [demonstrate] that strong levels of natural selection acted about 1.2 mya to produce darkly pigmented skin in early members of the genus Homo|journal=Annual Review of Anthropology|year=2004|volume=33|pages=585–623|doi=10.1146/annurev.anthro.33.070203.143955}}</ref><ref name=Bower>{{cite journal|last=Bower|first=C.|author2=Stanley|title=The role of nutritional factors in the aetiology of neural tube defects|journal=Journal of Paediatrics and Child Health|year=1992|volume=28|pages=12–16|doi=10.1111/j.1440-1754.1992.tb02610.x|pmid=1554510|issue=1}}</ref><ref>{{cite web|last=O'Neil |first=Dennis |title=Overview |url=http://anthro.palomar.edu/vary/vary_1.htm |work=Modern Human Variation |publisher=Palomar College |accessdate=6 January 2013 |deadurl=yes |archiveurl=https://web.archive.org/web/20121105101522/http://anthro.palomar.edu/vary/vary_1.htm |archivedate=5 November 2012 |df= }}</ref> Even within the same region, physical phenotype is not related to genetic affinity. Despite [[pygmy]] populations of [[South East Asia]] ([[Andamanese]]) having similar physical features with African pygmy populations such as short stature, dark skin, and curly hair, they are not genetically closely related to these populations.<ref name=liu>Liu, James J.Y. The Chinese Knight Errant. London: Routledge and Kegan Paul, 1967 {{ISBN|0-226-48688-5}}.</ref> Genetic variants affecting superficial anatomical features (such as skin color)—from a genetic perspective, are essentially meaningless—they involve a few hundred of the billions of nucleotides in a person's DNA.<ref name=natgeo>{{cite web|last=Iqbal|first=Saadia|title=A New Light on Skin Color|url=http://ngm.nationalgeographic.com/ngm/0211/feature2/online_extra.html|publisher=National Geographic Magazine|accessdate=6 January 2013}}</ref> Individuals with the same morphology do not necessarily cluster with each other by lineage, and a given lineage does not include only individuals with the same trait complex.<ref name="roberts1"/><ref name="goodman1"/><ref name=pmid15507998>{{cite journal |last1=Keita |first1=S O Y |last2=Kittles |first2=R A |last3=Royal |first3=C D M |last4=Bonney |first4=G E |last5=Furbert-Harris |first5=P |last6=Dunston |first6=G M |last7=Rotimi |first7=C N |title=Conceptualizing human variation |journal=Nature Genetics |volume=36 |issue=11 Suppl |pages=S17–20 |year=2004 |pmid=15507998 |doi=10.1038/ng1455 }}</ref>
 
Due to practices of group [[endogamy]], allele frequencies cluster locally around kin groups and lineages, or by national, ethnic, cultural and linguistic boundaries, giving a detailed degree of correlation between genetic clusters and population groups when considering many alleles simultaneously. Despite this, there are no genetic boundaries around local populations that biologically mark off any [[Race (human classification)|discrete groups]] of humans. Human variation is continuous, with no clear points of demarcation. There are no large clusters of relatively homogeneous people and almost every individual has genetic alleles from several ancestral groups.<ref name="roberts1"/><ref name="vary02"/><ref name="pbsmarks1"/><ref name=pmid15507998/><ref>{{cite journal|title=Census, race and science|journal=Nature Genetics|year=2000|volume=24|pages=97–98|doi=10.1038/72884|quote=That race (...) is not a scientific term is generally agreed upon by scientists—and a message that cannot be repeated often enough.}}</ref><ref name=harrison1>{{cite book|last=Harrison|first=Guy|title=Race and Reality|year=2010|publisher=Prometheus Books|location=Amherst|quote=Race is a poor empirical description of the patterns of difference that we encounter within our species. The billions of humans alive today simply do not fit into neat and tidy biological boxes called races. Science has proven this conclusively. The concept of race (...) is not scientific and goes against what is known about our ever-changing and complex biological diversity.}}</ref><ref>{{cite book|last=Roberts|first=Dorothy|title=Fatal Invention|year=2011|publisher=The New Press|location=London, New York|quote=The genetic differences that exist among populations are characterized by gradual changes across geographic regions, not sharp, categorical distinctions. Groups of people across the globe have varying frequencies of polymorphic genes, which are genes with any of several differing nucleotide sequences. There is no such thing as a set of genes that belongs exclusively to one group and not to another. The clinal, gradually changing nature of geographic genetic difference is complicated further by the migration and mixing that human groups have engaged in since prehistory. Genetic studies have substantiated the absence of clear biological borders; thus the term "race" is rarely used in scientific terminology, either in biological anthropology and in human genetics. Race has no genetic or biological basis. Human beings do not fit the zoological definition of race. Race is not a biological category that is politically charged. It is a political category that has been disguised as a biological one.}}</ref><ref>{{cite web|last=Goodman|first=Alan|title=Interview with Alan Goodman|url=http://www.pbs.org/race/000_About/002_04-background-01-07.htm|work=Race Power of and Illusion|publisher=PBS|accessdate=6 January 2013|quote=There's no biological basis for race. And that is in the facts of biology, the facts of non-concordance, the facts of continuous variation, the recentness of our evolution, the way that we all commingle and come together, and how genes flow. (...) There's no generalizability to race. There is no center there (...). It's fluid.}}</ref><ref>Steve Olson, Mapping Human History: Discovering the Past Through Our Genes, Boston, 2002</ref><ref>{{cite web|title=Race – The Power of an Illusion|url=http://www.pbs.org/race/000_General/000_00-Home.htm|publisher=PBS|accessdate=2 January 2013}}</ref><ref>{{cite journal|last=Jablonski|first=Nina|title=The evolution of human skin and skin color|journal=Annual Review of Anthropology|year=2004|volume=33|pages=585–623|doi=10.1146/annurev.anthro.33.070203.143955}}</ref><ref name="Palmie2007">{{Cite journal|doi=10.1525/ae.2007.34.2.205 |title=Genomics, divination, 'racecraft' |date=May 2007 |last1=Palmié |first1=Stephan |journal=American Ethnologist |volume=34 |pages=205–22 }}</ref>{{citekill|date=July 2017}}
 
==Psychology==
{{Main article|Psychology}}
{{Further information|Human brain|Mind}}
[[File:NIA human brain drawing.jpg|thumb|Drawing of the [[human brain]], showing several important structures]]
 
The human brain, the focal point of the [[central nervous system]] in humans, controls the [[peripheral nervous system]]. In addition to controlling "lower," involuntary, or primarily [[autonomic nervous system|autonomic]] activities such as [[respiration (physiology)|respiration]] and [[digestion]], it is also the locus of "higher" order functioning such as [[thought]], [[reason]]ing, and [[abstraction]].<ref>[http://www.pbs.org/wnet/brain/3d/index.html 3-D Brain Anatomy], ''The Secret Life of the Brain'', Public Broadcasting Service. Retrieved April 3, 2005.</ref> These [[mental function|cognitive processes]] constitute the [[mind]], and, along with their [[behavior]]al consequences, are studied in the field of [[psychology]].
 
Generally regarded as more capable of these higher order activities, the human brain is believed to be more "intelligent" in general than that of any other known species. While some non-human species are capable of creating structures and [[Tool use by animals|using simple tools]]—mostly through instinct and mimicry—human technology is vastly more complex, and is constantly evolving and improving through time.
 
===Sleep and dreaming===
{{Main article|Sleep|Dream}}
Humans are generally [[Diurnality|diurnal]]. The average sleep requirement is between seven and nine hours per day for an adult and nine to ten hours per day for a child; elderly people usually sleep for six to seven hours. Having less sleep than this is common among humans, even though [[sleep deprivation]] can have negative health effects. A sustained restriction of adult sleep to four hours per day has been shown to correlate with changes in physiology and mental state, including reduced memory, fatigue, aggression, and bodily discomfort.<ref name=Grandner2010>{{cite journal |author1=Grandner, Michael A. |author2=Patel, Nirav P. |author3=Gehrman, Philip R. |author4=Perlis, Michael L. |author5=Pack, Allan I. |title=Problems associated with short sleep: bridging the gap between laboratory and epidemiological studies |journal=Sleep Medicine Reviews |year=2010 |volume=14 |issue=4 |pages=239–47 |pmid=19896872 |pmc=2888649 |doi=10.1016/j.smrv.2009.08.001}}</ref><!--cites previous two sentences--> During sleep humans dream. In dreaming humans experience sensory images and sounds, in a sequence which the dreamer usually perceives more as an apparent participant than as an observer. Dreaming is stimulated by the [[pons]] and mostly occurs during the [[REM phase of sleep]].
 
===Consciousness and thought===
{{Main article|Consciousness|Cognition}}
Humans are one of the relatively few species to have sufficient self-awareness [[mirror test|to recognize themselves in a mirror]].<ref name="Rochat1995">{{cite book|author=P. Rochat|title=The Self in Infancy: Theory and Research|url=https://books.google.com/books?id=L0rf6v4xaycC&pg=PA4|accessdate=28 March 2016|date=30 October 1995|publisher=Elsevier|isbn=978-0-08-054263-8|page=4}}</ref> Already at 18 months, most human children are aware that the mirror image is not another person.<ref>{{cite web |url=http://www.ulm.edu/~palmer/ConsciousnessandtheSymbolicUniverse.htm |title=Consciousness and the Symbolic Universe |author= Jack Palmer |accessdate=March 17, 2006}}</ref>
 
[[File:FBE CTU lecture.jpg|thumb|left|Humans in a lecture at the Faculty of Biomedical Engineering, [[Czech Technical University in Prague|CTU]], in Prague.]]
The human brain [[perception|perceives]] the external world through the [[sense]]s, and each individual human is influenced greatly by his or her experiences, leading to [[subjectivity|subjective]] views of [[existence]] and the passage of time. Humans are variously said to possess consciousness, [[self-awareness]], and a mind, which correspond roughly to the mental processes of [[thought]]. These are said to possess qualities such as self-awareness, [[sentience]], [[sapience]], and the ability to perceive the relationship between [[Personal identity|oneself]] and one's [[natural environment|environment]]. The extent to which the mind constructs or experiences the outer world is a matter of debate, as are the definitions and validity of many of the terms used above.
 
The physical aspects of the mind and brain, and by extension of the nervous system, are studied in the field of [[neurology]], the more behavioral in the field of psychology, and a sometimes loosely defined area between in the field of psychiatry, which treats mental illness and behavioral disorders. Psychology does not necessarily refer to the brain or nervous system, and can be framed purely in terms of [[Phenomenology (psychology)|phenomenological]] or [[information processing]] theories of the mind. Increasingly, however, an understanding of brain functions is being included in psychological theory and practice, particularly in areas such as [[artificial intelligence]], [[neuropsychology]], and [[cognitive neuroscience]].
 
The nature of thought is central to psychology and related fields. [[Cognitive psychology]] studies [[cognition]], the [[mental function|mental processes']] underlying behavior. It uses [[information processing]] as a framework for understanding the mind. Perception, learning, problem solving, memory, attention, language and emotion are all well researched areas as well. Cognitive psychology is associated with a school of thought known as [[cognitivism (psychology)|cognitivism]], whose adherents argue for an [[information processing]] model of mental function, informed by [[positivism]] and [[experimental psychology]]. Techniques and models from cognitive psychology are widely applied and form the mainstay of psychological theories in many areas of both research and applied psychology. Largely focusing on the development of the human mind through the life span, [[developmental psychology]] seeks to understand how people come to perceive, understand, and act within the world and how these processes change as they age. This may focus on intellectual, cognitive, neural, social, or [[moral development]]. [[Psychologists]] have developed [[intelligence]] [[Test (assessment)|tests]] and the concept of [[intelligence quotient]] in order to assess the relative intelligence of human beings and study its [[Distribution (mathematics)|distribution]] among population.<ref>{{Britannica|289811|Intelligence test}}</ref>
 
Some philosophers divide consciousness into phenomenal consciousness, which is experience itself, and access consciousness, which is the processing of the things in experience.<ref name="Bl">Ned Block: ''On a Confusion about a Function of Consciousness'' in: ''The Behavioral and Brain Sciences'', 1995.</ref> Phenomenal consciousness is the state of being conscious, such as when they say "I am conscious." Access consciousness is being conscious ''of'' something in relation to abstract concepts, such as when one says "I am conscious of these words." Various forms of access consciousness include awareness, self-awareness, conscience, [[Stream of consciousness (psychology)|stream of consciousness]], [[Phenomenology (philosophy)|Husserl's phenomenology]], and [[intentionality]]. The concept of phenomenal consciousness, in modern history, according to some, is closely related to the concept of [[qualia]]. [[Social psychology]] links sociology with psychology in their shared study of the nature and causes of human social interaction, with an emphasis on how people think towards each other and how they relate to each other. The behavior and mental processes, both human and non-human, can be described through [[animal cognition]], [[ethology]], [[evolutionary psychology]], and [[comparative psychology]] as well. [[Human ecology]] is an [[List of academic disciplines|academic discipline]] that investigates how humans and human [[society|societies]] interact with both their natural environment and the human [[social environment]].
 
===Motivation and emotion===
{{Main article|Motivation|Emotion}}
[[File:Plate depicting emotions of grief from Charles Darwin's book The Expression of the Emotions.jpg|right|thumb|Illustration of grief from [[Charles Darwin]]'s book ''[[The Expression of the Emotions in Man and Animals]]''.]]
Motivation is the driving force of desire behind all deliberate [[Action (philosophy)|actions]] of humans. Motivation is based on emotion—specifically, on the search for [[Contentment|satisfaction]] (positive emotional experiences), and the avoidance of conflict. Positive and negative is defined by the individual brain state, which may be influenced by [[social norm]]s: a person may be driven to [[self-injury]] or [[violence]] because their [[Human brain|brain]] is conditioned to create a positive response to these actions. Motivation is important because it is involved in the performance of all learned responses. Within [[psychology]], [[conflict avoidance]] and the [[libido]] are seen to be primary motivators. Within [[economics]], motivation is often seen to be based on [[incentive]]s; these may be [[financial]], [[moral]], or [[coercive]]. [[Religion]]s generally posit divine or [[demon]]ic influences.
 
[[Happiness]], or the state of being happy, is a human emotional condition. The definition of happiness is a common [[philosophy|philosophical]] topic. Some people might define it as the best condition that a human can have—a condition of [[mental health|mental]] and physical [[health]]. Others define it as [[wikt:freedom|freedom]] from want and [[suffering|distress]]; consciousness of the [[goodness and value theory|good]] order of things; assurance of one's place in the [[universe]] or [[society]].
 
Emotion has a significant influence on, or can even be said to control, human behavior, though historically many [[culture]]s and [[philosopher]]s have for various reasons discouraged allowing this influence to go unchecked. Emotional experiences perceived as [[pleasure|pleasant]], such as [[love]], [[admiration]], or [[joy]], contrast with those perceived as [[suffering|unpleasant]], like [[hate]], [[envy]], or [[sorrow (emotion)|sorrow]]. There is often a distinction made between refined emotions that are socially learned and [[wikt:survival|survival]] oriented emotions, which are thought to be innate. Human exploration of emotions as separate from other neurological phenomena is worthy of note, particularly in cultures where emotion is considered separate from physiological state. In some cultural medical theories emotion is considered so synonymous with certain forms of physical health that no difference is thought to exist. The [[Stoicism|Stoics]] believed excessive emotion was harmful, while some [[Sufi]] teachers felt certain extreme emotions could yield a conceptual perfection, what is often translated as [[ecstasy (emotion)|ecstasy]].
 
In modern scientific thought, certain refined emotions are considered a complex neural trait innate in a variety of [[domesticated animal|domesticated]] and non-domesticated [[mammal]]s. These were commonly developed in reaction to superior survival mechanisms and intelligent interaction with each other and the environment; as such, refined emotion is not in all cases as discrete and separate from natural neural function as was once assumed. However, when humans function in civilized tandem, it has been noted that uninhibited acting on extreme emotion can lead to social disorder and [[crime]].
 
===Sexuality and love===
{{Main article|Love|Human sexuality}}
[[File:Sweet Baby Kisses Family Love.jpg|thumb|Human parents continue caring for their offspring long after they are born.]]
For humans, sexuality has important social functions: it creates physical intimacy, bonds and hierarchies among individuals, besides ensuring biological [[reproduction]]. Sexual desire or [[libido]], is experienced as a bodily urge, often accompanied by strong emotions such as love, [[ecstasy (emotion)|ecstasy]] and [[jealousy]]. The significance of sexuality in the human species is reflected in a number of physical features among them hidden [[ovulation]], the evolution of external [[scrotum]] and [[human penis|penis]] suggesting [[sperm competition]], the absence of an [[Baculum|os penis]], permanent [[secondary sexual characteristics]] and the forming of [[pair bond]]s based on sexual attraction as a common social structure. Contrary to other primates that often advertise [[estrus]] through visible signs, human females do not have a distinct or visible signs of ovulation, plus they experience sexual desire outside of their fertile periods. These adaptations indicate that the meaning of sexuality in humans is similar to that found in the [[bonobo]], and that the complex human sexual behavior has a long [[evolution]]ary history.<ref name=Haviland2010>{{cite book |author1=Haviland, Wiliam A. |author2=Prins, Harald E.L. |author3=McBride, Bunny |author4=Walrath, Dana |title=Cultural Anthropology: The Human Challenge |year=2010 |publisher=Wadsworth/Cengage Learning |location=Belmont, California |page=82 |isbn=978-0-495-81082-7 |url=https://books.google.com/books?id=yP6TrXRpPdMC&pg=PA82}}</ref><!--cites last sentence-->
 
Human choices in acting on sexuality are commonly influenced by cultural norms which vary widely. Restrictions are often determined by religious beliefs or social customs. The pioneering researcher [[Sigmund Freud]] believed that humans are born [[Psychosexual development|polymorphously perverse]], which means that any number of objects could be a source of pleasure. According to Freud, humans then pass through five stages of [[psychosexual development]] and can fixate on any stage because of various traumas during the process. For [[Alfred Kinsey]], another influential sex researcher, people can fall anywhere along a continuous scale of [[sexual orientation]], with only small minorities fully [[heterosexual]] or [[homosexual]].<ref name="Book-2009">{{cite book |author=MobileReference |title=The Illustrated Encyclopedia of North American Mammals |url=https://books.google.com/books?id=VxK4KWrGn2cC&pg=PT601 |page=601 |date=15 December 2009 |work=MobileReference |accessdate=10 August 2013 }}</ref> Recent studies of [[neurology]] and [[genetics]] suggest people may be born predisposed to various sexual tendencies.<ref name=Buss2003>{{cite book |author=Buss, David M. |year=2003 |title=The Evolution of Desire: Strategies of Human Mating. Revised Edition |location=New York, New York |publisher=Basic Books |isbn=978-0-465-00802-5}}</ref>
 
==Behavior==
{{main article|Culture|Society|Human behavior}}
{| border="1" cellspacing="0" cellpadding="4"  style="width:308px; float:right; border:1px solid gray; border-collapse:collapse; font-size:100%; margin:0 0 .5em 1em;"
! colspan="2" style="background:Lightgrey; text-align:center;"| Human society statistics
|-
|[[World population]]<ref name="UNDES-Pop">{{cite web|url=http://esa.un.org/unpd/wpp/DVD/Files/1_Indicators%20(Standard)/EXCEL_FILES/1_Population/WPP2015_POP_F01_1_TOTAL_POPULATION_BOTH_SEXES.XLS |title=File POP/1-1: Total population (both sexes combined) by major area, region and country, annually for 1950-2100: Medium fertility variant, 2015–2100|work=World Population Prospects, the 2015 Revision|publisher=[[United Nations Department of Economic and Social Affairs]], Population Division, Population Estimates and Projections Section|date=July 2015|accessdate=2 October 2016}}</ref>
| {{#expr: {{data world|poptoday}} / 1e9 round 1}}&nbsp;billion
|-
|[[Population density#Human population density|Population density]]<ref name="UNDES-Pop"/><ref>{{cite web| url=https://www.cia.gov/library/publications/the-world-factbook/geos/xx.html |title=World |work=[[The World Factbook]] |publisher=[[CIA]] |date=17 May 2016 |accessdate=2 October 2016}}</ref>
|{{Pop density|{{data world|poptoday}}|{{data world|pst2|total area}}|km2|sqmi|prec=0}} by total area<br />{{Pop density|{{data world|poptoday}}|{{data world|pst2|land area}}|km2|sqmi|prec=0}} by land area
|-
| valign="top" | [[World's largest cities|Largest agglomerations]]<br><small>{{citation needed|date=February 2012}}</small>
| style="text-align: left;" |  [[Beijing]], [[Bogotá]], [[Buenos Aires]], [[Cairo]], [[Delhi]], [[Dhaka]], [[Guangzhou]], [[Istanbul]], [[Jakarta]], [[Karachi]], [[Kinshasa]], [[Kolkata]], [[Lagos]], [[Lima]], [[London]], [[Los Angeles]], [[Manila]], [[Mexico City]], [[Moscow]], [[Mumbai]], [[New York City]], [[Osaka]], [[Paris]], [[Rio de Janeiro]], [[São Paulo]], [[Seoul]], [[Shanghai]], [[Shenzhen]], [[Tehran]], [[Tianjin]], [[Tokyo]], [[Wuhan]]
|-
| valign="top" | Most widely spoken native languages<ref>{{cite web|url=http://www.ethnologue.com/ethno_docs/distribution.asp?by=size |title=Statistical Summaries |publisher=Ethnologue |accessdate=2011-12-10}}</ref>
| style="text-align: left;" | [[Chinese language|Chinese]], [[Spanish language|Spanish]], [[English language|English]], [[Hindi]], [[Arabic]], [[Portuguese language|Portuguese]], [[Bengali language|Bengali]], [[Russian language|Russian]], [[Japanese language|Japanese]], [[Javanese language|Javanese]], [[German language|German]], [[Lahnda language|Lahnda]], [[Telugu language|Telugu]], [[Marathi language|Marathi]], [[Tamil language|Tamil]], [[French language|French]], [[Vietnamese language|Vietnamese]], [[Korean language|Korean]], [[Urdu]], [[Italian language|Italian]], [[Indonesian language|Indonesian]], [[Persian language|Persian]], [[Turkish language|Turkish]], [[Polish language|Polish]], [[Oriya language|Oriya]]
|-
| circulating|Most popular [[religion]]s<ref>{{cite web|url=https://www.cia.gov/library/publications/the-world-factbook/geos/xx.html |title=CIA – The World Factbook |publisher=Cia.gov |accessdate=2011-12-10}}</ref>
| style="text-align: left;" | [[Christianity]], [[Islam]], [[Hinduism]], [[Buddhism]], [[Sikhism]], [[Judaism]], [[Baha'i]]
|-
|[[Gross domestic product|GDP]] ([[Real versus nominal value|nominal]])<br><small>{{citation needed|date=February 2012}}</small>
|[[US dollar|US$]]36,356,240 million <br> (US$5,797 [[per capita]])
|-
|GDP ([[Purchasing power parity|PPP]])<br><small>{{citation needed|date=February 2012}}</small>
|$51,656,251 million [[International dollar|IND]]<br> ($8,236 per capita)
|}
[[File:Indian family in Brazil posed in front of hut.jpg|thumb|upright|left|Humans often live in family-based social structures.]]
Humans are highly social beings and tend to live in large complex social groups. More than any other creature, humans are capable of utilizing systems of [[communication]] for self-expression, the exchange of ideas, and [[social organization|organization]], and as such have created complex [[social structures]] composed of many cooperating and competing groups. Human groups range from the size of families to [[nations]]. Social interactions between humans have established an extremely wide variety{{clarify|date=January 2014}} of values, social norms, and rituals, which together form the basis of human [[society]].
 
Culture is defined here as patterns of complex symbolic behavior, i.e. all behavior that is not innate but which has to be learned through social interaction with others; such as the use of distinctive [[material culture|material]] and [[symbolic system]]s, including language, ritual, social organization, traditions, beliefs and technology.
 
===Language===
While many species [[animal communication|communicate]], [[language]] is unique to humans, a defining feature of humanity, and a [[cultural universal]]. Unlike the limited systems of other animals, human language is open—an infinite number of meanings can be produced by combining a limited number of symbols. Human language also has the capacity of [[Displacement (linguistics)|displacement]], using words to represent things and happenings that are not presently or locally occurring, but reside in the shared imagination of interlocutors.<ref name="Revolution"/> Language differs from other forms of communication in that it is [[Origin of speech#Modality-independence|modality independent]]; the same meanings can be conveyed through different media, auditively in speech, visually by sign language or writing, and even through tactile media such as [[braille]]. Language is central to the communication between humans, and to the sense of identity that unites nations, cultures and ethnic groups. The invention of writing systems at least five thousand years ago allowed the preservation of language on material objects, and was a major technological advancement. The science of [[linguistics]] describes the structure and function of language and the relationship between languages. There are approximately six thousand different languages currently in use, including [[sign language]]s, and many thousands more that are [[extinct language|extinct]].<ref name=Comrie1996>{{cite book |author1=Comrie, Bernard |author2=Polinsky, Maria |author3=Matthews, Stephen |title=The Atlas of Languages: The Origin and Development of Languages Throughout the World |year=1996 |publisher=Facts on File |location=New York, New York |pages=13–15 |isbn=978-0-8160-3388-1}}</ref>
 
===Gender roles===
{{Main article|Gender role|Gender}}
The sexual division of humans into male and female has been marked culturally by a corresponding division of roles, norms, [[practice (social theory)|practices]], dress, behavior, [[rights]], [[duty|duties]], [[Privilege (social inequality)|privileges]], [[social status|status]], and [[power (philosophy)|power]]. [[Cultural identity|Cultural differences]] by gender have often been believed to have arisen naturally out of a division of reproductive labor; the biological fact that women give birth led to their further cultural responsibility for nurturing and caring for children. Gender roles have varied historically, and challenges to predominant gender norms have recurred in many societies.
 
===Kinship===
{{main article|Kinship|Marriage}}
[[File:thedragonpainter.jpg|thumb|left|[[Sessue Hayakawa]] (left) with actress and wife [[Tsuru Aoki]] in a screen shot of the 1919 film ''The Dragon Painter''.]]
 
All human societies organize, recognize and classify types of social relationships based on relations between parents and children ([[consanguinity]]), and relations through marriage ([[Affinity (law)|affinity]]). These kinds of relations are generally called kinship relations. In most societies kinship places mutual responsibilities and expectations of solidarity on the individuals that are so related, and those who recognize each other as kinsmen come to form networks through which other social institutions can be regulated. Among the many functions of kinship is the ability to form [[descent group]]s, groups of people sharing a common line of descent, which can function as political units such as [[clan]]s. Another function is the way in which kinship unites families through marriage, forming [[Alliance theory|kinship alliances]] between groups of wife-takers and wife-givers. Such alliances also often have important political and economical ramifications, and may result in the formation of political organization above the community level. Kinship relations often includes regulations for whom an individual should or shouldn't marry. All societies have rules of [[incest taboo]], according to which marriage between certain kinds of kin relations are prohibited—such rules vary widely between cultures.{{citation needed|date=August 2015}} Some societies also have rules of preferential marriage with certain kin relations, frequently with either [[Parallel and cross cousins|cross or parallel cousins]]. Rules and norms for marriage and social behavior among kinsfolk is often reflected in the systems of [[kinship terminology]] in the various languages of the world. In many societies kinship relations can also be formed through forms of co-habitation, adoption, fostering, or companionship, which also tends to create relations of enduring solidarity ([[nurture kinship]]).
 
===Ethnicity===
{{main article|Ethnic group}}
Humans often form ethnic groups, such groups tend to be larger than kinship networks and be organized around a common identity defined variously in terms of shared ancestry and history, shared cultural norms and language, or shared biological phenotype. Such ideologies of shared characteristics are often perpetuated in the form of powerful, compelling narratives that give legitimacy and continuity to the set of shared values. Ethnic groupings often correspond to some level of political organization such as the [[Band society|band]], [[tribe]], [[city state]] or [[nation]]. Although ethnic groups appear and disappear through history, members of ethnic groups often conceptualize their groups as having histories going back into the deep past. Such ideologies give ethnicity a powerful role in defining [[social identity]] and in constructing solidarity between members of an ethno-political unit. This unifying property of ethnicity has been closely tied to the rise of the [[nation state]] as the predominant form of political organization in the 19th and 20th century.<ref>J. Hutchinson & A.D. Smith (eds.), ''Oxford readers: Ethnicity'' (Oxford 1996), "Introduction"{{page needed|date=October 2016}}</ref><ref>Smith, Anthony D. (1999) Myths and Memories of the Nation. Oxford University Press. pp. 4–7</ref><ref>{{cite journal |last1=Banton |first1=Michael |title=Max Weber on 'ethnic communities': a critique |journal=Nations and Nationalism |volume=13 |issue=1 |year=2007 |pages=19–35 |doi=10.1111/j.1469-8129.2007.00271.x }}</ref><ref>Delanty, Gerard & Krishan Kumar (2006) The SAGE Handbook of Nations and Nationalism. SAGE. {{ISBN|1412901014}} p. 171</ref><ref name="cohen">Ronald Cohen 1978 "Ethnicity: Problem and Focus in Anthropology" in ''Annual Review of Anthropology'' 7: 383 Palo Alto: Stanford University Press</ref><ref>[[Thomas Hylland Eriksen]] (1993) Ethnicity and Nationalism: Anthropological Perspectives. London: Pluto Press{{page needed|date=October 2016}}</ref>
 
===Society, government, and politics===
{{Main article|Origins of society|Society|Government|Politics|State (polity)}}
[[File:United Nations Headquarters in New York City, view from Roosevelt Island.jpg|thumb|right|The [[United Nations]] [[United Nations Headquarters|Headquarters]] in [[New York City]], which houses one of the largest political organizations in the world]]
[[File:Russian honor guard at Tomb of the Unknown Soldier, Alexander Garden welcomes Michael G. Mullen 2009-06-26 2.jpg|thumb|Russian honor guard at Tomb of the Unknown Soldier.]]
Society is the system of organizations and institutions arising from interaction between humans. Within a society people can be divided into different groups according to their [[income]], [[wealth]], [[power (social and political)|power]], [[reputation]], etc., but the structure of [[social stratification]] and the degree of [[social mobility]] differs, especially between modern and traditional societies.<ref>{{cite web|url=http://web.unitn.it/files/download/8481/srs_schizzerotto_social_stratification_2_as.pdf|title=Social Stratification|last=Schizzerotto|first=Antonio|publisher=[[University of Trento]]|access-date=3 July 2017}}</ref> A state is an organized political community occupying a definite territory, having an organized government, and possessing internal and external [[sovereignty]]. Recognition of the state's claim to independence by other states, enabling it to enter into international agreements, is often important to the establishment of its statehood. The "state" can also be defined in terms of domestic conditions, specifically, as conceptualized by [[Max Weber]], "a state is a human community that (successfully) claims the monopoly of the 'legitimate' use of physical force within a given territory."<ref>[https://web.archive.org/web/20020612070242/http://www.mdx.ac.uk/www/study/xWeb.htm Max Weber's definition of the modern state 1918], by [[Max Weber]], 1918. Retrieved March 17, 2006.</ref>
 
Government can be defined as the political means of creating and enforcing [[law]]s; typically via a [[bureaucracy|bureaucratic]] [[hierarchy]]. Politics is the process by which decisions are made within groups; this process often involves conflict as well as compromise. Although the term is generally applied to behavior within governments, politics is also observed in all human group interactions, including corporate, academic, and religious institutions. Many different political systems exist, as do many different ways of understanding them, and many definitions overlap. Examples of governments include [[monarchy]], [[Communist state]], [[military dictatorship]], [[theocracy]], and [[liberal democracy]], the last of which is considered dominant today. All of these issues have a direct relationship with economics.
 
===Trade and economics===
{{Main article|Trade|Economics}}
[[File:Tengeru market.jpg|thumb|right|[[Buyer]]s and [[seller]]s [[bargaining]] in a market]]
Trade is the voluntary exchange of goods and services, and is a form of economics. A mechanism that allows trade is called a [[Market (economics)|market]]. Modern traders instead generally negotiate through a medium of exchange, such as money. As a result, buying can be separated from selling, or [[earnings|earning]]. Because of specialization and [[division of labor]], most people concentrate on a small aspect of manufacturing or service, trading their labor for products. Trade exists between regions because different regions have an [[Absolute advantage|absolute]] or [[comparative advantage]] in the production of some tradable commodity, or because different regions' size allows for the benefits of [[mass production]].
 
Economics is a [[social science]] which studies the production, distribution, trade, and consumption of goods and services. Economics focuses on measurable variables, and is broadly divided into two main branches: [[microeconomics]], which deals with individual agents, such as households and businesses, and macroeconomics, which considers the economy as a whole, in which case it considers [[aggregate supply]] and [[aggregate demand|demand]] for money, [[capital (economics)|capital]] and [[commodity|commodities]]. Aspects receiving particular attention in economics are [[resource allocation]], production, distribution, trade, and [[competition]]. Economic logic is increasingly applied to any problem that involves choice under scarcity or determining economic [[Value (economics)|value]].
 
===War===
{{Main article|War}}
[[File:nagasakibomb.jpg|thumb|right|180px|The [[mushroom cloud]] of the [[Atomic bombings of Hiroshima and Nagasaki|atomic bombing of Nagasaki]] on August 9, 1945]]
War is a state of organized armed conflict between [[State (polity)|states]] or [[non-state actors]]. War is characterized by the use of lethal [[violence]] against others—whether between [[combatants]] or upon [[non-combatants]]—to achieve military goals through force. Lesser, often spontaneous conflicts, such as brawls, [[riots]], [[revolts]], and [[melees]], are not considered to be warfare. [[Revolution]]s can be [[Nonviolent revolution|nonviolent]] or an organized and armed revolution which denotes a state of war. During the 20th century, it is estimated that between 167 and 188 million people died as a result of war.<ref>Ferguson, Niall. "The Next War of the World." Foreign Affairs, Sep/Oct 2006</ref> A common definition defines war as a series of [[military campaign]]s between at least two opposing sides involving a dispute over [[sovereignty]], territory, [[natural resource|resources]], [[religion]], or other issues. A war between internal elements of a state is a [[civil war]]. Among animals, all-out war against fellow members of the same species occurs only among large societies of humans and [[ants]].{{citation needed|date=March 2016}}
 
[[File:Bataille Waterloo 1815 reconstitution 2011 3.jpg|thumb|Men in period costume portraying soldiers during a 2011 reenactment of the [[Battle of Waterloo]] (1815)]]
There have been a wide variety of [[Revolution in Military Affairs|rapidly advancing]] [[military tactics|tactics]] throughout the history of war, ranging from [[conventional war]] to [[asymmetric warfare]] to [[total war]] and [[unconventional warfare]]. Techniques include [[hand to hand combat]], the use of [[ranged weapons]], [[naval warfare]], and, more recently, [[air support]]. Military intelligence has often played a key role in determining victory and defeat. Propaganda, which often includes information, slanted opinion and disinformation, plays a key role both in maintaining unity within a warring group and in sowing discord among opponents. In [[modern warfare]], [[soldier]]s and [[combat vehicle]]s are used to control the land, [[warships]] the sea, and [[aircraft]] the sky. These fields have also overlapped in the forms of [[marines]], [[paratroopers]], [[aircraft carriers]], and [[surface-to-air missiles]], among others. [[Satellites]] in [[low Earth orbit]] have made outer space a factor in warfare as well through their use for detailed intelligence gathering; however, no known aggressive actions have been [[space warfare|taken from space]].
 
===Material culture and technology===
{{Main article|Tool|Technology}}
[[File:Néolithique 0001.jpg|thumb|An array of Neolithic artifacts, including bracelets, axe heads, chisels, and polishing tools.]]
Stone tools were used by proto-humans at least 2.5&nbsp;million years ago.<ref name=Clark1994>{{cite journal |author1=Clark, J.D. |author2=de Heinzelin, J. |author3=Schick, K.D. |title=African ''Homo erectus'': old radiometric ages and young Oldowan assemblages in the Middle Awash Valley, Ethiopia |journal=Science |year=1994 |volume=264 |issue=5167 |pages=1907–10 |pmid=8009220 |doi=10.1126/science.8009220|display-authors=etal}}</ref> The [[Control of fire by early humans|controlled use of fire]] began around 1.5&nbsp;million years ago. Since then, humans have made major advances, developing complex technology to create tools to aid their lives and allowing for other advancements in culture. Major leaps in technology include the discovery of [[agriculture]]—what is known as the [[Neolithic Revolution]], and the invention of automated machines in the [[Industrial Revolution]].
 
[[Archaeology]] attempts to tell the story of past or lost cultures in part by close examination of the [[Artifact (archaeology)|artifacts]] they produced. Early humans left [[stone tools]], [[pottery]], and [[jewelry]] that are particular to various regions and times.
 
====Body culture====
{{main article|Clothing|Body modification|Haircut}}
Throughout history, humans have altered their appearance by wearing clothing<ref>{{cite journal |vauthors=Kvavadze E, Bar-Yosef O, Belfer-Cohen A, Boaretto E, Jakeli N, Matskevich Z, Meshveliani T |title=30,000-year-old wild flax fibers |journal=Science |volume=325 |issue=5946 |page=1359 |year=2009 |pmid=19745144 |doi=10.1126/science.1175404 }}</ref> and [[adornment]]s, by trimming or [[shaving]] hair or by means of body modifications.
 
Body modification is the deliberate altering of the [[human anatomy|human body]] for any non-medical reason, such as aesthetics, sexual enhancement, a rite of passage, religious reasons, to display group membership or affiliation, to create [[body art]], shock value, or self-expression.<ref name="DeMello2007"/> In its most broad definition it includes [[plastic surgery]], socially acceptable decoration (e.g. common [[earring|ear piercing]] in many societies), and religious rites of passage (e.g. [[circumcision]] in a number of cultures).<ref name="DeMello2007">{{cite book|author=Margo DeMello|title=Encyclopedia of Body Adornment|url=https://books.google.com/books?id=s0122BsqrZwC&pg=PR17|accessdate=6 April 2012|year=2007|publisher=ABC-CLIO|isbn=978-0-313-33695-9|pages=17–}}</ref>
 
===Philosophy and self-reflection===
{{Main article|Philosophy|Human self-reflection}}
{{See also|Human nature}}
[[File:Confuciusstatue.jpg|thumb|upright|Statue of [[Confucius]] on [[Chongming Island]] in [[Shanghai]]]]
 
Philosophy is a discipline or field of study involving the investigation, analysis, and development of ideas at a general, abstract, or fundamental level. It is the discipline searching for a general understanding of reality, reasoning and values. Major fields of philosophy include [[logic]], [[metaphysics]], [[epistemology]], [[philosophy of mind]], and [[axiology]] (which includes [[ethics]] and [[aesthetics]]). Philosophy covers a very wide range of approaches, and is used to refer to a [[worldview]], to a perspective on an issue, or to the positions argued for by a particular philosopher or school of philosophy.
 
===Religion and spirituality===
{{Main article|Religion|Spirituality}}
 
Religion is generally defined as a [[belief]] system concerning the [[supernatural]], [[sacred]] or [[divine]], and practices, [[values]], institutions and [[ritual]]s associated with such belief. Some religions also have a [[moral code]]. The [[Evolutionary psychology of religion|evolution]] and the history of the [[Evolutionary origin of religions|first religions]] have recently become areas of active scientific investigation.<ref>{{cite web |url=http://evolution.binghamton.edu/religion/|title=Evolutionary Religious Studies: A New Field of Scientific Inquiry}}</ref><ref name=Boyer2008>{{cite journal |author=Boyer, Pascal |title=Being human: Religion: bound to believe? |journal=Nature |volume=455 |issue=7216 |pages=1038–39 |year=2008 |pmid=18948934 |doi=10.1038/4551038a}}</ref><ref name=Emmons2003>{{Cite journal |author1=Emmons, Robert A. |author2=Paloutzian, Raymond F. |title=The psychology of religion |journal=Annual Review of Psychology |year=2003 |pmid=12171998 |volume=54 |issue=1 |pages= 377–402 |doi=10.1146/annurev.psych.54.101601.145024}}</ref> However, in the course of its [[development of religion|development]], religion has taken on many forms that vary by culture and individual perspective. Some of the chief questions and issues religions are concerned with include life after death (commonly involving belief in an [[afterlife]]), the [[origin of life]], the nature of the [[universe]] ([[religious cosmology]]) and its [[ultimate fate]] ([[eschatology]]), and what is [[morality|moral]] or immoral. A common source for answers to these questions are beliefs in [[transcendence (religion)|transcendent]] [[divine]] beings such as [[deities]] or a singular [[God]], although not all religions are [[theistic]]. Spirituality, belief or involvement in matters of the [[soul]] or [[spirit]], is one of the many different approaches humans take in trying to answer fundamental questions about humankind's place in the universe, the [[meaning of life]], and the ideal way to live one's life. Though these topics have also been addressed by philosophy, and to some extent by science, spirituality is unique in that it focuses on [[mystical]] or supernatural concepts such as [[karma]] and God.
 
Although the exact level of religiosity can be hard to measure,<ref name=Hall2008>{{cite journal |author1=Hall, Daniel E. |author2=Meador, Keith G. |author3=Koenig, Harold G. |title=Measuring religiousness in health research: review and critique |journal=Journal of Religion and Health |volume=47 |issue=2 |pages=134–63 |year=2008 |pmid=19105008 |doi=10.1007/s10943-008-9165-2}}</ref> a majority of humans professes some variety of religious or spiritual belief, although many (in some countries a majority) are [[irreligious]]. This includes humans who have no religious beliefs or do not identify with any religion. [[Humanism]] is a philosophy which seeks to include all of humanity and all issues common to humans; it is usually non-religious. Most religions and spiritual beliefs are clearly distinct from science on both a philosophical and methodological level; the two are not generally considered mutually exclusive and a majority of humans hold a mix of both scientific and religious views. The distinction between philosophy and religion, on the other hand, is at times less clear, and the two are linked in such fields as the [[philosophy of religion]] and [[theology]].
{{clear}}
 
===Art, music, and literature===
{{Main article|Art|Music|Literature}}
[[File:Lorenzo Lippi 001.jpg|thumb|upright|''Allegory of Music'' (ca. 1594), a [[painting]] of a woman writing [[sheet music]] by [[Lorenzo Lippi]]]] Art is a [[cultural universal]], and humans have been producing artistic works at least since the days of [[Cro-Magnon]]. Art may be defined as a form of [[culture|cultural]] expression and the usage of [[narrative]]s of liberation and exploration (i.e. [[art history]], [[art criticism]], and [[art theory]]) to mediate its boundaries. This distinction may be applied to objects or performances, current or historical, and its prestige extends to those who made, found, exhibit, or own them. In the modern use of the word, art is commonly understood to be the process or result of making material works that, from concept to creation, adhere to the "creative impulse" of human beings. Art is distinguished from other works by being in large part unprompted by necessity, by biological drive, or by any undisciplined pursuit of recreation.
 
Music is a natural [[Intuition (knowledge)|intuitive]] phenomenon based on the three distinct and interrelated organization structures of rhythm, harmony, and melody. Listening to music is perhaps the most common and universal form of [[entertainment]], while learning and understanding it are popular [[discipline]]s.{{citation needed|date=June 2013}} There are a wide variety of [[music genre]]s and [[ethnic music]]s. [[Literature]], the body of written—and possibly oral—works, especially creative ones, includes prose, poetry and drama, both fiction and [[non-fiction]]. Literature includes such genres as [[epic poetry|epic]], legend, myth, ballad, and folklore.
 
===Science===
{{Main article|Science}}
 
Another unique aspect of human culture and thought is the development of complex methods for acquiring knowledge through observation, quantification, and verification. The [[scientific method]] has been developed to acquire knowledge of the physical world and the rules, processes and principles of which it consists, and combined with mathematics it enables the prediction of complex patterns of causality and consequence. Some other animals are able to recognize differences in small quantities, {{citation needed|date=October 2013}} but humans are able to understand and recognize much larger, even abstract, quantities, and to recognize and understand algorithmic patterns which enables infinite [[counting]] routines and algebra, something that is not found in any other species.
{{clear}}
 
All of [[science]] can be divided into three major branches, the [[formal sciences]] (e.g., [[logic]] and [[mathematics]]), which are concerned with [[formal systems]], the [[applied sciences]] (e.g.,  [[engineering]], [[medicine]]), which are focused on pratical applications, and the empirical sciences, which are based on [[empirical observation]] and are in turn divided into [[natural sciences]] (e.g., [[physics]], [[chemistry]], [[biology]]) and [[social sciences]] (e.g., [[psychology]], [[economics]], [[sociology]]).<ref>{{cite web|url=https://pmr.uchicago.edu/sites/pmr.uchicago.edu/files/uploads/BranchesofSciencePresentation.pdf|title=Branches of Science|publisher=[[University of Chicago]]}}</ref> A [[pseudoscience]] is an activity or a teaching which is mistakenly regarded as being scientific by its major proponents.<ref>{{cite web|url=https://plato.stanford.edu/entries/pseudo-science/|title=Science and Pseudo-Science|website=Stanford Encyclopedia of Philosophy|access-date=3 July 2017}}</ref>


==External links==
==External links==
* This lore is based on content found at https://en.wikipedia.org/wiki/Human
* Some of this lore is based on content found at https://en.wikipedia.org/wiki/Human


[[Category:Lore]]
[[Category:Lore]]

Revision as of 05:53, 29 August 2017

Modern humans (Homo sapiens) are the only extant members of the subtribe Hominina, a branch of the tribe Hominini belonging to the family of great apes. They are a space-faring species hailing originally from the planet Earth in the Sol system. They are currently among the most numerous known species in the galaxy, in both population and holdings, and are relatively technologically advanced.

Humanity is the primary driving force for rapid space expansion, owing to their strong, expansionist central government and opportunistic Trans-Stellar Corporations. The prejudices of the 21st century have mostly given way to bitter divides on the most important issue of the times; technological expansionism, with some major human factions squabbling over their approach to technology in the face of a looming technological singularity.

While most humans have accepted the existence of aliens in their communities and workplaces as a fact of life, some exceptions still exist. While more culturally diverse than most species, humans are generally regarded as somewhat technophobic and isolationist by members of other species.

Overview

  • Humans have their own language, Sol Common, which you can speak by typing say #1.
  • Due to how most technology in human-controlled space was made for humans in mind, they can wear most clothing, and even wear some specialized space suits designed for other species.
  • Humans have no species wide restriction on diet, where as other species might.
  • Humans are not barred from certain jobs, such as Heads of Staff or Internal Affairs, as NanoTrasen is a human-run company, after all.

Biology

Human.png

The most commonly defined body systems in humans are the nervous, the cardiovascular, the circulatory, the digestive, the endocrine, the immune, the integumentary, the lymphatic, the musculoskeletal, the reproductive, the respiratory, and the urinary system.

Humans, like most of the other apes, lack external tails, have several blood type systems, have opposable thumbs, and are sexually dimorphic. Humans are also among the best long-distance runners in the galactic animal kingdom, but slower over short distances. Humans' thinner body hair and more productive sweat glands help avoid heat exhaustion while running for long distances. Humans have about 2 million sweat glands spread over their entire bodies.

It is estimated that the average height for an adult human male is about 172 cm (5 ft 7 1⁄2 in), while the worldwide average height for adult human females is about 158 cm (5 ft 2 in). Shrinkage of stature may begin in middle age in some individuals, but tends to be typical in the extremely aged. Through history human populations have universally become taller, probably as a consequence of better nutrition, healthcare, and living conditions. The average mass of an adult human is 54–76 kg (119–168 lb). Like many other conditions, body weight and body type is influenced by genetic susceptibility, environment, diet, and it varies greatly among individuals.

Although humans appear hairless, with notable hair growth occurring chiefly on the top of the head, underarms and pubic area, the average human has more hair follicles on his or her body than the average chimpanzee. The main distinction is that human hairs are shorter, finer, and less heavily pigmented than a chimpanzee's, thus making them harder to see.

Reproduction

As with other mammals, human reproduction takes place as internal fertilization by sexual intercourse. During this process, the male inserts his erect penis into the female's vagina and ejaculates semen, which contains sperm. The sperm travels through the vagina and cervix into the uterus or Fallopian tubes for fertilization of the ovum. Upon fertilization and implantation, gestation then occurs within the female's uterus.

The zygote divides inside the female's uterus to become an embryo, which over a period of 38 weeks (9 months) of gestation becomes a fetus. After this span of time, the fully grown fetus is birthed from the woman's body and breathes independently as an infant for the first time. At this point, most modern cultures recognize the baby as a person entitled to the full protection of the law, though some jurisdictions extend various levels of personhood earlier to human fetuses while they remain in the uterus.

Compared with other species, human childbirth is dangerous. Painful labors lasting 24 hours or more are not uncommon and sometimes lead to the death of the mother, the child or both. This is because of both the relatively large fetal head circumference and the mother's relatively narrow pelvis. The chances of a successful labor increased significantly during the 20th and 21st centuries with the advent of new medical technologies. In contrast, pregnancy and natural childbirth remain hazardous ordeals in developing regions of the galaxy, with maternal death rates approximately 100 times greater than in developed systems.

Humans are considerably helpless at birth, and will continue to grow for some years, typically reaching sexual maturity at 12 to 15 years of age. Females continue to develop physically until around the age of 18, whereas male development continues until around age 21. The human life span can be split into a number of stages: infancy, childhood, adolescence, young adulthood, adulthood and old age.

Gender Differences

The most obvious differences between males and females include all the features related to reproductive role, notably the endocrine (hormonal) systems and their physiological and behavioral effects, including gonadal differentiation, internal and external genital and breast differentiation, and differentiation of muscle mass, height, and hair distribution.

Externally, the most sexually dimorphic portions of the human body are the chest, the lower half of the face, and the area between the waist and the knees. Males often weigh slightly more than females, and are also slightly taller. On average, men also have a larger waist in comparison to their hips than women. Women however have a larger hip section than men; an adaptation for giving birth to infants with large skulls. Women also usually have substantially larger breasts due to the presence of milk-producing mammary glands.

The sexual division of humans into male and female has been marked culturally by a corresponding division of roles, norms, practices, dress, behavior, rights, duties, privileges, status, and power. Cultural differences by gender have often been believed to have arisen naturally out of a division of reproductive labor; the biological fact that women give birth led to their further cultural responsibility for nurturing and caring for children. Gender roles have varied historically, and challenges to predominant gender norms have recurred in many societies.

Lifespan

With good healthcare and a reasonable lifestyle, a human can live to around 110 years. The oldest known humans are around 150 years old.

Diet

Humans are omnivores, and have evolved to be able to handle a wide variety of foods. However, even humans cannot safely ingest chemicals that are almost universally toxic to other species, like cyanide, phoron, ethanol, or heavy metals.

Strangely, despite the toxicity of some compounds, such as ethanol, many humans will intentionally consume such compounds regardless of the risks.

Behavior

Humanity's behavior varies immensely from system to system. Social norms, the often-unspoken rules of a group, shape not just the behaviors of humans, but also their attitudes. An individual's behavior varies depending on the group(s) they are a part of. Humans who have been adopted by other species will often adopt the mannerisms of a foster parent and the society surrounding them, even to the extent of subconsciously mimicking speech and accents. Humans are also very capable of learning and comprehending other languages, so long as they are within a human's range of hearing. Humans thrive on knowledge, much like the Skrell.

However, unlike any other species in the known galaxy, even more than Sergals, or Unathi, almost every one of humanity's major technological advancements have been fundamentally based in the need to conduct war. The very advent of space travel was a product made not of a desire to explore, but as a means to demonstrate their military superiority over other rivaling nations on Earth. As such, humanity's core military, the UNSC, is arguably the most powerful military force in the known galaxy. Despite a lag in technology behind some other species, such as the Skrell, humanity makes up for it with a knack for grand strategy and asymmetric warfare. Unlike other races, humans very much continue to be at war with other humans as old grudges survive to the modern day.

Humans are unpredictable in how they'll respond to contact with alien species, though this largely depends on societal and economic factors that vary immensely with each population. Some humans will greet aliens as if they were just like any other human, even to the extent of forming deep and romantic inter-species relationships, while the opposite extreme is sometimes violence based on xenophobic prejudices. Humans who have been exposed to alien races since a young age will often base their opinion of aliens as a whole off that experience, while humans who had no such exposure will trend toward being xenophobic and isolationist. Notably, humans who grew up in poverty are also more inclined toward xenophobic tenancies, whereas humans who were better off will not have their views significantly affected by their economic status.

Relations

The United Systems of Sol Central, aka SolGov, acts as most of humanity's representative. As of 2560, there are no ongoing wars between SolGov and any known sapient species, although Sol-Moghes tensions continue to run high, and Vox raiders remain a nuisance.

The Skrell are humanity's oldest contact and closest allies, with free migration between the two species' space and a great deal of cultural interchange. However, some on both sides accuse the other species of tampering with their own natural growth and development, and many libertarian humans loathe the caste-based monarchy of the Skrell.

Humanity is still licking their wounds after their war with the Unathi, and despite their victory, still regard Moghes with a good deal of fear. Efforts on both sides of the border to ease tensions have not prevented the occasional wave of xenophobic violence.

The Tajaran were lifted into the FTL age by human intervention, a fact neither is likely to forget. Humanity bears over the Tajaran and freely exploit migrant labor, while they look upon their uplifters with a mix of gratitude and wounded pride.

Like most races, humanity views the Dionaea as curiosities and little else, given their disinterest in the ways of other sapients.

The Teshari are a rarity outside of Skrell space, and a negligible presence on the astropolitical landscape. The average human accepts the Skrell's paternalistic view of the Teshari as fact.

Opinion of positronics varies erratically between seeing it as the next logical step of human evolution, to viewing it as potentially the extinction of the human race. Regardless, relations between the two are marred by their history of enslavement and the continued discrimination positronics face throughout the galaxy.

Despite the disastrous early stages of a war with the Sergal race, many efforts have been made to build good relationships between Sol and Vilous. Having brought both Sergals and Nevareans into the FTL age, the two races share a relationship with humanity not unlike that of the Tajaran. This is largely thanks to Operation Dominion, a post-war reconstruction and propaganda campaign on Tal, which began in response to the Vilous Incident.

Individually, while humans may vary widely on how they feel of the other known species, centuries of cultural xenophobia often prove difficult to shake.

External links

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