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Homo sapiens

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Homo sapiens
Temporal range: 0.2–0 Ma
Middle PleistocenePresent
Akha man and woman in northern Thailand – husband carries stem of banana-plant, which will be fed to their pigs
Male and female H s. sapiens
(Akha in northern Thailand,
2010 photograph)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Infraorder: Simiiformes
Family: Hominidae
Genus: Homo
Species: H. sapiens
Binomial name
Homo sapiens
Linnaeus, 1758
Subspecies

H. s. sapiens
H. s. idaltu
H. s. neanderthalensis(?)
H. s. rhodesiensis(?)
(others propsed)

Homo sapiens is the systematic name used in taxnomy (also known as binomial nomenclature) for anatomically modern humans, i.e. the only extant human species. The name is Latin for "wise man" and was introduced in 1758 by Carl Linnaeus (who is himself also the type specimen).

Extinct species of the genus Homo are classified as "archaic humans". This includes at least the separate species Homo erectus, and possibly a number of other species (which are variously also considered subspecies of either H. sapiens or H. erectus. H. sapiens idaltu (2003) is a proposed extinct subspecies of H. sapiens.

The age of speciation of H. sapiens out of ancestral H. erectus (or an intermediate species such as Homo heidelbergensis) is estimated to have taken place at roughly 315,000 years ago. However, there is known to have been continued admixture from archaic human species until as late as some 30,000 years ago; this is also the time of disappearance of any surviving archaic human species, which were apparently absorbed by the recent Out-Of-Africa expansion of Homo sapiens beginning some 50,000 years ago.

Name and taxonomy

The binomial name Homo sapiens was coined by Carl Linnaeus (1758).[2] The Latin noun homō (genitive hominis) means "human being."

Extant human populations have historically been divided into subspecies, but since c. the 1980s all extant groups tend to be subsumed into a single species, H. sapiens, avoiding division into subspecies altogehter.[3]

Some sources show Neanderthals (Homo neanderthalensis) as a subspecies (Homo sapiens neanderthalensis).[4][5] Similarly, the discovered specimens of the Homo rhodesiensis species have been classified by some as a subspecies (Homo sapiens rhodesiensis), although it remains more common to treat these last two as separate species within the Homo genus rather than as subspecies within H. sapiens.[6]

Age and speciation process

Schematic representation of the emergence of H. sapiens from earlier species of Homo. The horizontal axis represents geographic location; the vertical axis represents time in millions of years ago. Blue areas denote the presence of a certain species at a given time and place. Early modern humans spread from Africa across different regions of the globe and interbred with other descendants of Homo heidelbergensis, namely Neanderthals, Denisovans, and unknown archaic African hominins (top right).[7]

Traditionally, there are two competing views in paleoanthropology about the origin of H. sapiens: the recent African origin and the multiregional origin. Since 2010, genetic research has led to the emergence of an intermediate position, characterised by mostly recent African origin with the addition of limited admixture (introgression) from archaic humans.

The recent African origin of modern humans is the mainstream model that describes the origin and early dispersal of anatomically modern humans. The theory is called the (Recent) Out-of-Africa model in the popular press, and academically the recent single-origin hypothesis (RSOH), Replacement Hypothesis, and Recent African Origin (RAO) model. The hypothesis that humans have a single origin (monogenesis) was published in Charles Darwin's Descent of Man (1871). The concept was speculative until the 1980s, when it was corroborated by a study of present-day mitochondrial DNA, combined with evidence based on physical anthropology of archaic specimens. According to genetic and fossil evidence, archaic Homo sapiens evolved to anatomically modern humans solely in Africa, roughly 200,000 years ago, with members of one branch leaving Africa by 60,000 years ago and over time replacing earlier human populations, such as Neanderthals and Homo erectus. More recently, in 2017, fossils found in Jebel Irhoud (Morocco) suggest that Homo sapiens may have evolved as early as 315,000 years ago;[8] and other evidence suggests that Homo sapiens may have migrated from Africa as early as 120,000 years ago, particularly into Asia,[9][10] and even as early as 270,000 years ago.[11][12]

The recent single origin of modern humans in East Africa was the near-consensus position held within the scientific community prior to 2010.[13]

However, significant archaic human admixture with modern humans in was discovered in the 2010s. Green et al. (2010) suggest that their findings are consistent with Neanderthal admixture of up to 4% in some populations. But the study also suggests that there may be other reasons why humans and Neanderthals share ancient genetic lineages.[14] In August 2012, a study by scientists at the University of Cambridge questioned this conclusion, hypothesising instead that the DNA overlap is a remnant of a common ancestor of both Neanderthals and modern humans. That study however does not explain why only a fraction of modern humans have Neanderthal DNA.[15][16]

The multiregional origin model, proposed by Milford H. Wolpoff[17] in 1988[18] provides another explanation for the pattern of human evolution. Multiregional origin holds that the evolution of humanity from the beginning of the Pleistocene 2.5 million years BP to the present day has been within a single, continuous human species.

Homo sapiens idaltu, the other known subspecies, is now extinct.[19] Homo neanderthalensis, which became extinct 30,000 years ago, has sometimes been classified as a subspecies, "Homo sapiens neanderthalensis"; genetic studies now suggest that the functional DNA of modern humans and Neanderthals diverged 500,000 years ago.[20]

The Omo remains (discovered between 1967 and 1974), dated to some 195,000 years ago, were long considered the oldest known fossils identifiable as anatomically modern humans. A number of studies molecular biology conducted between 2005 and 2010 have yielded results compatible with the age of the Omo remains, placing the common ancestor of all modern human populations[dubious ] some 200,000 years ago.[21]

The San people of Southern Africa have been found to be the human population with the deepest temporal division from all other contemporary populations, estimated at close to 130,000 years ago. A 2011 study has classified them as one of "ancestral population clusters". The same study also located the origin of the first wave of expansion of H. sapiens, beginning roughly 130,000 years ago, in southwestern Africa, near the coastal border of Namibia and Angola.[22]

Following the second Out-of-Africa expansion, some 70,000 to 50,000 years ago, some subpopulations of H. sapiens have been essentially isolated for tens of thousands of years prior to the early modern Age of Discovery. Combined with archaic admixture this has resulted in significant genetic variation, which in some instances has been shown to be the result of directional selection taking place over the past 15,000 years, i.e. significantly later than possible archaic admixture events.[23]

References

  1. ^ Global Mammal Assessment Team (2008). "Homo sapiens". IUCN Red List of Threatened Species. Version 2008. International Union for Conservation of Nature. Retrieved 12 February 2015. 
  2. ^ Linné, Carl von (1758). Systema naturæ. Regnum animale (10th ed.). pp. 18, 20. Retrieved 19 November 2012. .
  3. ^ The history of claimed or proposed subspecies of H. sapiens is complicated and fraught with controversy. The only widely recognized archaic subspecies is H. sapiens idaltu (2003). The name H. s. sapiens is due to Linnaeus (1758), and refers by definition the subspecies of which Linnaeus himself is the type specimen. However, Linnaeus postulated four other extant subspecies, viz. H. s. afer, H. s. americanus, H. s. asiaticus and H. s. ferus for Africans, Americans, Asians and Malay. This classification remained in common usage until the mid 20th century, sometimes alongide H. s. tasmanianus for Australians. See e.g. John Wendell Bailey, The Mammals of Virginia (1946), p. 356.; Journal of Mammalogy 26-27 (1945), p. 359.; The Mankind Quarterly 1-2 (1960), 113ff ("Zoological Subspecies of Man"). The division of extant human populations into taxonomic subspecies was gradually given up in the 1970s (e.g. Grzimek's Animal Life Encyclopedia, Volume 11, p. 55).
  4. ^ Hublin, J. J. (2009). "The origin of Neandertals". Proceedings of the National Academy of Sciences. 106 (38): 16022–7. Bibcode:2009PNAS..10616022H. doi:10.1073/pnas.0904119106. JSTOR 40485013. PMC 2752594Freely accessible. PMID 19805257. 
  5. ^ Harvati, K.; Frost, S.R.; McNulty, K.P. (2004). "Neanderthal taxonomy reconsidered: implications of 3D primate models of intra- and interspecific differences". Proc. Natl. Acad. Sci. U.S.A. 101 (5): 1147–52. Bibcode:2004PNAS..101.1147H. doi:10.1073/pnas.0308085100. PMC 337021Freely accessible. PMID 14745010. 
  6. ^ "Homo neanderthalensis King, 1864". Wiley-Blackwell Encyclopedia of Human Evolution. Chichester, West Sussex: Wiley-Blackwell. 2013. pp. 328–331. 
  7. ^ Stringer, C. (2012). "What makes a modern human". Nature. 485 (7396): 33–35. Bibcode:2012Natur.485...33S. doi:10.1038/485033a. PMID 22552077. 
  8. ^ Callaway, Ewan (7 June 2017). "Oldest Homo sapiens fossil claim rewrites our species' history". Nature. doi:10.1038/nature.2017.22114. Retrieved 11 June 2017. 
  9. ^ Bae, Christopher J.; Douka, Katerina; Petraglia, Michael D. (8 December 2017). "On the origin of modern humans: Asian perspectives". Science. 358 (6368): eaai9067. doi:10.1126/science.aai9067. Retrieved 10 December 2017. 
  10. ^ Kuo, Lily (10 December 2017). "Early humans migrated out of Africa much earlier than we thought". Quartz. Retrieved 10 December 2017. 
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  12. ^ Posth, Cosimo; et al. (4 July 2017). "Deeply divergent archaic mitochondrial genome provides lower time boundary for African gene flow into Neanderthals". Nature Communications. doi:10.1038/ncomms16046. Retrieved 4 July 2017. 
  13. ^ Liu, Hua; et al. (2006). "A Geographically Explicit Genetic Model of Worldwide Human-Settlement History". The American Journal of Human Genetics. 79 (2): 230–237. doi:10.1086/505436. PMC 1559480Freely accessible. PMID 16826514. Currently available genetic and archaeological evidence is generally interpreted as supportive of a recent single origin of modern humans in East Africa. However, this is where the near consensus on human settlement history ends, and considerable uncertainty clouds any more detailed aspect of human colonization history.  "Out of Africa Revisited". Science. 308 (5724): 921g. 2005-05-13. doi:10.1126/science.308.5724.921g. Retrieved 2009-11-23.  Nature (2003-06-12). "Human evolution: Out of Ethiopia". Nature. 423 (6941): 692–695. Bibcode:2003Natur.423..692S. doi:10.1038/423692a. PMID 12802315. Retrieved 2009-11-23.  "Origins of Modern Humans: Multiregional or Out of Africa?". ActionBioscience. Retrieved 2009-11-23.  "Modern Humans – Single Origin (Out of Africa) vs Multiregional". Asa3.org. Retrieved 2009-11-23. 
  14. ^ Green, RE; Krause, J; Briggs, AW; Maricic, T; Stenzel, U; Kircher, M; Patterson, N; Li, H; Zhai, W; Fritz, M. H. Y.; Hansen, N. F.; Durand, E. Y.; Malaspinas, A. S.; Jensen, J. D.; Marques-Bonet, T.; Alkan, C.; Prufer, K.; Meyer, M.; Burbano, H. A.; Good, J. M.; Schultz, R.; Aximu-Petri, A.; Butthof, A.; Hober, B.; Hoffner, B.; Siegemund, M.; Weihmann, A.; Nusbaum, C.; Lander, E. S.; Russ, C.; et al. (2010). "A Draft Sequence of the Neandertal Genome". Science. 328 (5979): 710–22. Bibcode:2010Sci...328..710G. doi:10.1126/science.1188021. PMC 5100745Freely accessible. PMID 20448178. 
  15. ^ Study casts doubt on human-Neanderthal interbreeding theory, The Guardian, Tuesday 14 August 2012
  16. ^ Anders Eriksson and Andrea Manica Effect of ancient population structure on the degree of polymorphism shared between modern human populations and ancient hominins PNAS 2012 : 1200567109v1-201200567. July 20, 2012
  17. ^ Wolpoff, MH; Hawks, J; Caspari, R (2000). "Multiregional, not multiple origins". Am J Phys Anthropol. 112 (1): 129–36. doi:10.1002/(SICI)1096-8644(200005)112:1<129::AID-AJPA11>3.0.CO;2-K. PMID 10766948. 
  18. ^ Wolpoff, MH; JN Spuhler; FH Smith; J Radovcic; G Pope; DW Frayer; R Eckhardt; G Clark (1988). "Modern human origins". Science. 241 (4867): 772–4. Bibcode:1988Sci...241..772W. doi:10.1126/science.3136545. PMID 3136545. 
  19. ^ Human evolution: the fossil evidence in 3D, by Philip L. Walker and Edward H. Hagen, Dept. of Anthropology, University of California, Santa Barbara. Retrieved April 5, 2005.
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  22. ^ Henn, Brenna; Gignoux, Christopher R.; Jobin, Matthew (2011). "Hunter-gatherer genomic diversity suggests a southern African origin for modern humans". Proceedings of the National Academy of Sciences of the United States of America. National Academy of Sciences. 108 (13): 5154–62. Bibcode:2011PNAS..108.5154H. doi:10.1073/pnas.1017511108. PMC 3069156Freely accessible. PMID 21383195. 
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External links

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