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Archaic human admixture with modern Homo sapiens is known to have occurred at least twice in history: with Neanderthals, and with the Denisova hominin. A minimum estimated 1 to 4 percent of the DNA in Europeans and Asians (i.e. French, Chinese and Papua probands) is non-modern, and shared with ancient Neanderthal DNA rather than with Sub-Saharan Africans (i.e. Yoruba and San probands).[1][2] A minimum additional estimated 4-6% of Melanesian DNA is from the archaic Denisovan hominins from Asia.[3] Recent DNA analysis also indicates Sub-Saharan African admixture with a now extinct archaic population. [4]


Neanderthals

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Various theories of Neanderthal admixture in modern human DNA, i.e. the result of interbreeding of Neanderthals and anatomically modern humans during the Middle Paleolithic have been debated throughout the 20th century, and in terms of genetics throughout the 2000s.[5][6]

In May 2010, the Neanderthal Genome Project presented preliminary genetic evidence that interbreeding did likely take place and that a small but significant portion of Neanderthal admixture is present in modern non-African populations. The interbreeding hypothesis is a controversially discussed scenario of Neanderthal extinction, the disappearance of Neanderthal traits from the fossil record about 30,000 years ago. Nonetheless, and according to recent genetic studies, modern humans seem to have mated with "at least two groups" of ancient humans: Neanderthals and Denisovans.[7]

History

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The hypothesis, variously under the names of interbreeding, hybridization, admixture or hybrid-origin theory, has been discussed ever since the discovery of Neanderthal remains in 19th century, though earlier writers believed that Neanderthals were a direct ancestor of modern humans. Thomas Huxley suggested that many Europeans bore traces of Neanderthal ancestry, but associated Neanderthal characteristics with primitivism, writing that since they "belong to a stage in the development of the human species, antecedent to the differentiation of any of the existing races, we may expect to find them in the lowest of these races, all over the world, and in the early stages of all races."[8]

In the early twentieth century, Carleton Coon argued that the Caucasoid race is of dual origin consisting of Upper Paleolithic (mixture of H. sapiens and neanderthalensis) types and Mediterranean (purely H. sapiens) types. He repeated his theory in his 1962 book The Origin of Races.[9]

Stan Gooch in Personality and Evolution (1973) and The Neanderthal Question (1977) develops a theory of Neanderthal/Cro-Magnon hybridization, based not on an examination of anatomy but of his understanding of modern human psychology and society, which he claimed owes a significant debt to Neanderthal culture. Gooch's theories were dismissed by academia. Gooch refined his theory in Cities of Dreams (1989) and The Neanderthal Legacy (2008).

The focus of the debate shifted from the study of anatomy to archaeogenetics in the 2000s and to the study of ancient DNA with the Neanderthal Genome Project, beginning in 2006.

The question of Neanderthal/Cro-Magnon hybridization is reflected in 20th century popular culture, in works such as La Guerre du feu (1911), Dance of the Tiger (1978, 1980) by Finnish palaeontologist Björn Kurtén, and the Earth's Children series by Jean M. Auel, published from 1980.

Genetics

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Further information: Neanderthal Genome Project and admixture mapping

A draft sequence publication by the Neanderthal Genome Project in May 2010 indicates that Neanderthals share more genetic lineages with Non-African populations than with African populations. According to the study, this scenario is best explained by gene flow from Neanderthals to modern humans after humans emerged from Africa. An estimated 1 to 4 percent of the DNA in Europeans and Asians (e.g. French, Chinese and Papua probands) is non-modern, and shared with ancient Neanderthal DNA rather than with Sub-Saharan Africans (e.g. Yoruba and San probands). Though less parsimonious than gene flow, ancient sub-structure in Africa, could account for the higher levels of Neanderthal lineages detected in Eurasians. [10]

No evidence supporting this has been found in mitochondrial DNA analyses of modern Europeans, suggesting at least that no direct maternal line originating with Neanderthals has survived into modern times.[11][12][13]

Variation in microcephalin, a critical regulator of brain size whose loss-of-function by damaging mutations may also cause primary microcephaly, was claimed to be the strongest evidence of admixture as of 2007. One type of the gene, known as D, has a high worldwide frequency (~70%), but a young coalescence age to its most recent common ancestor, ~37,000 years ago. The remaining types (non-D) coalesce to ~990,000 years ago, while the separation time between D and non-D is estimated at ~1,100,000 years ago. An evolutionary advantage of D is possible but controversial.[14]

The distribution of the D allele, high outside Africa but low in sub-Saharan Africa (29%), has been suggested to indicate involvement of an archaic Eurasian population, and current estimates of the divergence time between modern humans and Neanderthals based on mitochondrial DNA are in favor of the Neanderthal lineage as the most likely archaic Homo population from which introgression into the modern human gene pool took place.[15][16] However, according to Svante Pääbo, ancient DNA from Croatian Neanderthal fossils found at Vindija shows that they carried the non-D allele of microcephalin, and there is no evidence for admixture or introgression.[17][18] However a study published in May 2010 found that a Neanderthal individual from Mezzena Rockshelter (Monti Lessini, Italy), possessed the ancestral version of D, rather than the derived version which is common among Eurasian populations. The study did not rule out interbreeding between Neanderthals and modern humans, but indicates that the particular DNA sample provides no support to the theory that Neanderthals contributed the derived allele of D to modern humans.[19]

Based on a 2001 study of the gene that results in red-headedness,[20] some commentators speculated that Neanderthals had red hair and that some red-headed and freckled humans today share some heritage with Neanderthals.[21][22] A 2007 study analysing Neanderthal DNA found that some Neanderthals were red-haired, but the mutation to the MC1R gene which caused red hair in Neanderthals is not found in modern humans.[23]

There is evidence that some immune related genes are of Neanderthal origin. HLA-C*0702 is common in modern Europeans and Asians but rarely[24] seen in Africans, but is found in Neanderthals. It is thought that this immune gene may have been picked up by humans after leaving Africa to help deal with European diseases that the Neanderthals had evolved defenses for.[25]

Anatomy

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The most vocal proponent of the hybridization hypothesis on anatomical grounds has been Erik Trinkaus of Washington University.[26] Trinkaus claims various fossils as hybrid individuals, including the "child of Lagar Velho", a skeleton found at Lagar Velho in Portugal dated to about 24,000 years ago.[27] In a 2006 publication co-authored by Trinkaus, the fossils found in 1952 in the cave of Pestera Muierii, Romania, are likewise claimed as hybrids. [28]

In his work Neanderthal, Paul Jordan points out that without some interbreeding, certain features on some "modern" skulls of Eastern European Cro-Magnon heritage are hard to explain.[29] In another study, researchers have recently found in Peştera Muierilor, Romania, remains of European humans from 30 thousand years ago who possessed mostly diagnostic "modern" anatomical features, but also had distinct Neanderthal features not present in ancestral modern humans in Africa, including a large bulge at the back of the skull, a more prominent projection around the elbow joint, and a narrow socket at the shoulder joint. Analysis of one skeleton's shoulder showed that these humans, like Neanderthal, did not have the full capability for throwing spears.[30]

The paleontological analysis of modern-human emergence in Europe has been shifting from considerations of the Neanderthals to assessments of the biology and chronology of the earliest modern humans in western Eurasia. This focus, involving morphologically modern humans before 28,000 years ago, shows accumulating evidence that they present a variable mosaic of derived modern human, archaic human, and Neanderthal features.[28][31][32] Studies of fossils from the upper levels of the Sima de las Palomas, Murcia, Spain, dated to 40,000 years ago, establish the late persistence of Neanderthals in Iberia. This reinforces the conclusion that the Neanderthals were not merely swept away by advancing modern humans. In addition, the Palomas Neanderthals variably exhibit a series of modern-human features rare or absent in earlier Neanderthals. Either they were evolving on their own towards the modern-human pattern, or more likely, they had contact with early modern humans around the Pyrenees. If the latter is the case, it implies that the persistence of the Middle Paleolithic in Iberia was a matter of choice, and not cultural retardation.[33]

Modern-human findings in Abrigo do Lagar Velho, Portugal, of 24,500 years ago, allegedly featuring Neanderthal admixtures, have been published.[34] However the interpretation of the Portuguese specimen is disputed.[35]

Denisova hominin

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Tests comparing the Denisova hominin genome with those of six modern humans whose genome has been sequenced, a ǃKung from South Africa, a Nigerian, a French person, a Papua New Guinean, a Bougainville Islander and a Han Chinese showed that between 4% and 6% of the genome of Melanesians (represented by the Papua New Guinean and Bougainville Islander) derives from a Denisovan population, possibly introduced during the early migration of the ancestors of Melanesians into Southeast Asia. This history of interaction suggests that Denisovans once ranged widely over eastern Asia.[3]

Melanesians thus emerge as the most "archaic"-admixed population, having Denisovan/Neandertal-related admixture of ~8%.

Archaic Admixture in Africa

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Analysis of DNA data indicates that contemporary Sub-Saharan African populations contain a small percentage of genetic material from a now extinct archaic population (similar to the non-African admixture with Neanderthal and Denisova). The admixture occurred approximately 35,000 years ago with a archaic population that diverged from the ancestors of modern humans approximately 700,000 years ago. [36]

See also

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References

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  1. ↑ Green, Richard E.; et al. (2010-05-07). "A Draft Sequence of the Neandertal Genome". Science. 328 (5979): 710–722. doi:10.1126/science.1188021. PMID 20448178. {{cite journal}}: Explicit use of et al. in: |author= (help)
  2. ↑ "NEANDERTALS LIVE!". john hawks weblog. Retrieved 2010-12-31.
  3. ↑ a b Reich, David; Green, Richard E.; Kircher, Martin; Krause, Johannes; Patterson, Nick; Durand, Eric Y.; Viola, Bence; Briggs, Adrian W.; Stenzel, Udo; Johnson, Philip L. F.; Maricic, Tomislav; Good, Jeffrey M.; marques-Bonet, Tomas; Alkan, Can; Fu, Qiaomei; Mallick, Swapan; Li, Heng; Meyer, Matthias; Eichler, Evan E.; Stoneking, Mark; Richards, Michael; Talamo, Sahra; Shunkov, Michael V.; Derevianko, Anatoli P.; Hublin, Jean-Jacques; Kelso, Janet; Slatkin, Montgomery; Pääbo, Svante (2010), "Genetic history of an archaic hominin group from Denisova Cave in Siberia", Nature, 468 (7327): 1053–1060, doi:10.1038/nature09710, PMID 21179161 {{citation}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)
  4. ↑ Michael F. Hammer; et al. (2011-07-27). "Genetic evidence for archaic admixture in Africa". PNAS. {{cite journal}}: Explicit use of et al. in: |author= (help)
  5. ↑ Fagundes, Nelson J. R. (2007). "Statistical evaluation of alternative models of human evolution". PNAS. The National Academy of Sciences of the USA. 104 (45): 17614–17619. Bibcode:2007PNAS..10417614F. doi:10.1073/pnas.0708280104. PMC 2077041. PMID 17978179. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  6. ↑ Hodgson JA, Disotell TR (2008). "No evidence of a Neanderthal contribution to modern human diversity". Genome Biol. 9 (2): 206. doi:10.1186/gb-2008-9-2-206. PMC 2374707. PMID 18304371.
  7. ↑ Mitchell, Alanna (January 30, 2012). "DNA Turning Human Story Into a Tell-All". NYTimes. http://www.nytimes.com/2012/01/31/science/gains-in-dna-are-speeding-research-into-human-origins.html. Retrieved January 31, 2012. 
  8. ↑ Thomas Huxley, The Aryan Question and Pre-Historic Man (1890), Collected Essays VII.
  9. ↑ Coon, Careton, The Origin of Races, From Neanderthal to Nordic in Wuerm I", 1962, page 529.
  10. ↑ R. E. Green; et al. (2010). "A Draft Sequence of the Neandertal Genome". Science. 328 (5979): 710–722. Bibcode:2010Sci...328..710G. doi:10.1126/science.1188021. PMID 20448178. {{cite journal}}: Explicit use of et al. in: |author= (help)
  11. ↑ Krings M, Stone A, Schmitz RW, Krainitzki H, Stoneking M, Pääbo S (1997). "Neandertal DNA sequences and the origin of modern humans". Cell. 90 (1): 19–30. doi:10.1016/S0092-8674(00)80310-4. PMID 9230299. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  12. ↑ No Neandertals in the Gene Pool, Science (2004).
  13. ↑ Serre, D; Langaney, A; Chech, M; Teschler-Nicola, M; Paunovic, M; Mennecier, P; Hofreiter, M; Possnert, G; Pääbo, S (2004). "No evidence of Neandertal mtDNA contribution to early modern humans". PLoS Biology. 2 (3): 313–7. doi:10.1371/journal.pbio.0020057. PMC 368159. PMID 15024415.
  14. ↑ Mekel-Bobrov, N.; et al. (2007). "The ongoing adaptive evolution of ASPM and Microcephalin is not explained by increased intelligence". Hum. Mol. Genet. 16 (6): 600–8. doi:10.1093/hmg/ddl487. PMID 17220170. {{cite journal}}: Explicit use of et al. in: |author= (help)
  15. ↑ Evans, Patrick D. (2006-11-07). "Evidence that the adaptive allele of the brain size gene microcephalin introgressed into Homo sapiens from an archaic Homo lineage". PNAS. 103 (48): 18178–18183. Bibcode:2006PNAS..10318178E. doi:10.1073/pnas.0606966103. PMC 1635020. PMID 17090677. Retrieved 2008-05-26. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  16. ↑ Evans, Patrick D. (2005-09-09). "Microcephalin, a Gene Regulating Brain Size, Continues to Evolve Adaptively in Humans". Science. 309 (5741): 1717–1720. Bibcode:2005Sci...309.1717E. doi:10.1126/science.1113722. PMID 16151009. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  17. ↑ Morgan, James (12 February 2009). "Neanderthals 'distinct from us'". BBC News. http://news.bbc.co.uk/1/hi/sci/tech/7886477.stm. Retrieved 2009-10-11. 
  18. ↑ Gitlin, Jonathan M. (23 February 2009). "A Neanderthal in the family: working with ancient DNA". Ars Technica. http://arstechnica.com/science/news/2009/02/a-neanderthal-in-the-family-ars-at-aaas.ars. Retrieved 2009-10-11. 
  19. ↑ Lari, Martina; Rizzi, Ermanno; Milani, Lucio; Corti, Giorgio; Balsamo, Carlotta; Vai, Stefania; Catalano, Giulio; Pilli, Elena; Longo, Laura (2010). "The Microcephalin Ancestral Allele in a Neanderthal Individual". PLoS ONE. PLoS ONE. 5 (5): e10648. Bibcode:2010PLoSO...510648L. doi:10.1371/journal.pone.0010648. PMC 2871044. PMID 20498832.
  20. ↑ Red hair a legacy of Neanderthal man
  21. ↑ "Red-Heads and Neanderthals". May 2001. Archived from the original on 18 October 2005. Retrieved 2005-10-28.
  22. ↑ "Nicole's hair secrets". The Daily Telegraph (London). 2002-02-10. Archived from the original on 11 december 2005. http://web.archive.org/web/20051211173522/http://www.arts.telegraph.co.uk/connected/main.jhtml?xml=/connected/2002/10/04/ecfhair04.xml&sSheet=/connected/2002/10/04/ixconn.html. Retrieved 2005-11-02. 
  23. ↑ Rincon, Paul (25 October 2007). "Neanderthals 'were flame-haired'". BBC. http://news.bbc.co.uk/2/hi/science/nature/7062415.stm. 
  24. ↑ "Populations of Sub-Saharan Africa sorted by C*0702 allele frequency". The Allele Frequency Net Database. Retrieved January 2012. {{cite web}}: Check date values in: |accessdate= (help)
  25. ↑ Marshall, Michael (2011). "Breeding with Neanderthals helped humans go global". New Scientist. Retrieved January 2012. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |month= ignored (help)
  26. ↑ Dan Jones: The Neanderthal within., New Scientist 193.2007, H. 2593 (3 March), 28–32. Modern Humans, Neanderthals May Have Interbred [dead link]; Hayes, Jacqui (2 November 2006). "Humans and Neanderthals interbred, according to our anatomy". http://www.cosmosmagazine.com/node/814. Retrieved January 2012. 
  27. ↑ "The Lagar Velho 1 Skeleton". Talk Origins. Retrieved January 2012. {{cite web}}: Check date values in: |accessdate= (help); Text "July 2000" ignored (help); Sample, Ian (14 September 2006). "Life on the edge: was a Gibraltar cave last outpost of the lost neanderthal?". http://www.guardian.co.uk/science/story/0,,1871842,00.html. Retrieved January 2012. ; Hawks, John (2006-09-13). "Not a lasting last for the Neandertals". http://johnhawks.net/weblog/reviews/neandertals/gorhams_28000_date_2006.html. Retrieved January 2012. 
  28. ↑ a b Soficaru A, Dobos A, Trinkaus E (2006). "Early modern humans from the Peştera Muierii, Baia de Fier, Romania". Proceedings of the National Academy of Sciences. 103 (46): 17196–201. Bibcode:2006PNAS..10317196S. doi:10.1073/pnas.0608443103. PMC 1859909. PMID 17085588. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  29. ↑ Jordan, Paul (2000). Neanderthal. Sutton Publishing. ISBN 0750919345. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help); Unknown parameter |month= ignored (help)
  30. ↑ Hayes, Jacqui (2 November 2006). "Humans and Neanderthals interbred". Cosmos. http://www.cosmosmagazine.com/node/814. Retrieved 17 May 2009. 
  31. ↑ Trinkaus E, Moldovan O, Milota S, Bîlgăr A, Sarcina L, Athreya S, Bailey SE, Rodrigo R, Mircea G, Higham T, Ramsey CB, van der Plicht J (2003). "An early modern human from the Peştera cu Oase, Romania". Proceedings of the National Academy of Sciences. 100 (20): 11231–6. Bibcode:2003PNAS..10011231T. doi:10.1073/pnas.2035108100. PMC 208740. PMID 14504393. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  32. ↑ Trinkaus E (2007). "European early modern humans and the fate of the Neandertals". Proceedings of the National Academy of Sciences. 104 (18): 7367–72. Bibcode:2007PNAS..104.7367T. doi:10.1073/pnas.0702214104. PMC 1863481. PMID 17452632. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)
  33. ↑ Washington University in St. Louis (8 December 2008). "Late Neandertals and Modern Human Contact in Southeastern Iberia". Newswise. http://newswise.com/articles/view/547207/. Retrieved 16 May 2009. 
  34. ↑ Duarte C, Maurício J, Pettitt PB, Souto P, Trinkaus E, van der Plicht H, Zilhão J (1999). "The early Upper Paleolithic human skeleton from the Abrigo do Lagar Velho (Portugal) and modern-human emergence in Iberia". Proceedings of the National Academy of Sciences. 96 (13): 7604–9. Bibcode:1999PNAS...96.7604D. doi:10.1073/pnas.96.13.7604. PMC 22133. PMID 10377462. Retrieved 17 May 2009. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  35. ↑ Ruzicka J, Hansen EH, Ghose AK, Mottola HA (1979). "Enzymatic determination of urea in serum based on pH measurement with the flow injection method". Analytical Chemistry. 51 (2): 199–203. doi:10.1021/ac50038a011. PMID 33580. {{cite journal}}: |access-date= requires |url= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  36. ↑ Michael F. Hammer; et al. (2011-07-27). "Genetic evidence for archaic admixture in Africa". PNAS. {{cite journal}}: Explicit use of et al. in: |author= (help)
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