Recent human evolution

Recent human evolution refers to evolutionary adaptation and selection and genetic drift within anatomically modern human populations, since their separation and dispersal in the Middle Paleolithic. Following the peopling of Africa some 130,000 years ago, and the recent Out-of-Africa expansion some 70,000 to 50,000 years ago, some sub-populations 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.[1] Selection pressures were especially severe for populations affected by the Last Glacial Maximum in Eurasia, and for sedentary farming populations since the Neolithic.

Adaptations have also been found in modern populations living in extreme climatic conditions such as the Arctic and the Tibetan Plateau, as well as immunological adaptations such as resistance against brain disease in populations practicing mortuary cannibalism.[2][3]

Introgression

Some climatic adaptations, such as high-altitude adaptation in humans, are thought to have been acquired by archaic admixture. Introgression of genetic variants acquired by Neanderthal admixture have different distributions in European and East Asians, reflecting differences in recent selective pressures. A 2014 study reported that Neanderthal-derived variants found in East Asian populations showed clustering in functional groups related to immune and haematopoietic pathways, while European populations showed clustering in functional groups related to the lipid catabolic process.[4] A 2017 study found correlation of Neanderthal admixture in modern European populations with traits such as skin tone, hair color, height, sleeping patterns, mood and smoking addiction.[5]

Upper Paleolithic

Physiological or phenotypical changes have been traced to Upper Paleolithic mutations, such as the East Asian variant of the EDAR gene, dated to c. 35,000 years ago.[6]

Recent divergence of Eurasian lineages was sped up significantly during the Last Glacial Maximum, the Mesolithic and the Neolithic, due to increased selection pressures and founder effects associated with migration.[7] Alleles predictive of light skin have been found in Neanderthals, [8] but the alleles for light skin in Europeans and East Asians, associated with, KITLG and ASIP, are (as of 2012) thought to have not been acquired by archaic admixture but recent mutations since the LGM.[9] Phenotypes associated with the "white" or "Caucasian" populations of Western Eurasian stock emerge during the LGM, from about 19,000 years ago. The light skin pigmentation characteristic of modern Europeans is estimated to have spread across Europe in a "selective sweep" during the Mesolithic (19 to 11 ka). The associated TYRP1 SLC24A5 and SLC45A2 alleles emerge around 19 ka, still during the LGM, most likely in the Caucasus. [10] The HERC2 variation for blue eyes first appears around 14 ka in Italy and the Caucasus.[11]

Inuit adaptation to high-fat diet and cold climate has been traced to a mutation dated the Last Glacial Maximum (20,000 years ago).[12] Average cranial capacity in modern human populations varies in the range of 1,200 to 1,450 cm3 (adult male averages). Larger cranial volume is associated with climatic region, the largest averages being found in populations of Siberia and the Arctic.[13] Both Neanderthal and EEMH had somewhat larger cranial volumes on average than modern Europeans, suggesting the relaxation of selection pressures for larger brain volume after the end of the LGM.[14]

Holocene

Evolutionary adaptations have sped up significantly, at an estimated 100-fold pace compared to the Paleolithic, since the beginning of the Holocene, primarily in the farming populations of Eurasia.[15] Hawks et al. (2007) have tied this effect to new selection pressures arising from the new diets, new modes of habitation, and immunological pressures related to the domestication of animals.[15]

Examples for adaptations related to agriculture and animal domestication include East Asian types of ADH1B associated with rice domestication,[16] or lactase persistence.[17]

A recent adaptation has been proposed for the Austronesian Sama-Bajau in the form of an enlarged spleen which provides a larger amount of oxygen-rich red blood cells during, developed under selection pressures associated with subsisting on freediving over the past thousand years or so.[18]

In historical times, the emergence of complex societies, such as the medieval manorialism system in Northwestern Europe, have been suggested as the cause of selection pressures on various alleles related to behavioral and personality traits, such as heightened empathy (ADRA2b) and guilt culture (BDNF, 5-HTTLPR).[19]

In modern historical times, since industrialization, some trends have been observed: for instance, menopause is evolving to occur later.[20] Other reported trends appear to include lengthening of the human reproductive period and reduction in cholesterol levels, blood glucose and blood pressure in some populations.[20]

See also

References

  1. ↑ Wade, N (2006-03-07). "Still Evolving, Human Genes Tell New Story". The New York Times. Retrieved 2008-07-10.
  2. ↑ Medical Research Council (UK) (November 21, 2009). "Brain Disease 'Resistance Gene' evolves in Papua New Guinea community; could offer insights Into CJD". ScienceDaily. Rockville, MD: ScienceDaily, LLC. Retrieved 2009-11-22.
  3. ↑ Mead, S.; Whitfield, J.; Poulter, M.; Shah, P.; Uphill, J.; Campbell, T.; Al-Dujaily, H.; Hummerich, H.; Beck, J.; Mein, C. A.; Verzilli, C.; Whittaker, J.; Alpers, M. P.; Collinge, J. (2009). "A Novel Protective Prion Protein Variant that Colocalizes with Kuru Exposure". The New England Journal of Medicine. 361 (21): 2056–2065. doi:10.1056/NEJMoa0809716. PMID 19923577.
  4. ↑ "Specifically, genes in the LCP [lipid catabolic process] term had the greatest excess of NLS in populations of European descent, with an average NLS frequency of 20.8±2.6% versus 5.9±0.08% genome wide (two-sided t-test, P<0.0001, n=379 Europeans and n=246 Africans). Further, among examined out-of-Africa human populations, the excess of NLS [Neanderthal-like genomic sites] in LCP genes was only observed in individuals of European descent: the average NLS frequency in Asians is 6.7±0.7% in LCP genes versus 6.2±0.06% genome wide." Ekaterina E. Khrameeva, Katarzyna Bozek, Liu He, Zheng Yan, Xi Jiang, Yuning Wei, Kun Tang, Mikhail S. Gelfand, Kay Prufer, Janet Kelso, Svante Paabo, Patrick Giavalisco, Michael Lachmann & Philipp Khaitovich "Neanderthal ancestry drives evolution of lipid catabolism in contemporary Europeans", Nature Communications 5, Article number: 3584 (2014), doi:10.1038/ncomms4584.
  5. ↑ Michael Dannemann 1 and Janet Kelso, "The Contribution of Neanderthals to Phenotypic Variation in Modern Humans", The American Journal of Human Genetics 101, 578–589, October 5, 2017.
  6. ↑ Traits affected by the mutation are sweat glands, teeth, hair thickness and breast tissue. Kamberov et al., "Modeling Recent Human Evolution in Mice by Expression of a Selected EDAR Variant", Cell Volume 152, Issue 4, p691–702, 14 February 2013, DOI: https://dx.doi.org/10.1016/j.cell.2013.01.016. Journalistic report: East Asian Physical Traits Linked to 35,000-Year-Old Mutation, NYT, 14 February 2013.
  7. ↑ S. Beleza et al., "The Timing of Pigmentation Lightening in Europeans", Molecular Biology and Evolution, Volume 30, Issue 1, 1 January 2013, Pages 24–35, doi:10.1093/molbev/mss207. "As previously emphasized (Jablonski and Chaplin 2000), it is likely that the climatic conditions prevailing during the last glaciation favored cultural modifications that limited exposure to UVR, like shelter seeking and the wearing of more protective clothing. Moreover, seasonality (differences in solar radiation between the summer and the winter) is thought to have significantly increased from 18,000 to 10,000 years ago, extending the duration “vitamin D winters” and augmenting the risks of vitamin D insufficiency (COHMAP Consortium 1988; Gamble and Soffer 1990; Jablonski 2004; Parra 2007). Additionally, it is conceivable that population growth after the LGM was also an important factor in the onset of the selective sweeps observed for these three genes in Europe. As previously noted (Hawks et al. 2007; Karasov et al. 2010; Pritchard et al. 2010), effective population size is one of the most important factors limiting the availability of adaptive mutations."
  8. ↑ Lalueza-Fox; Römpler, H; Caramelli, D; Stäubert, C; Catalano, G; Hughes, D; Rohland, N; Pilli, E; Longo, L; Condemi, S; de la Rasilla, M; Fortea, J; Rosas, A; Stoneking, M; Schöneberg, T; Bertranpetit, J; Hofreiter, M; et al. (2007). "A melanocortin-1 receptor allele suggests varying pigmentation among Neanderthals". Science. 318 (5855): 1453–1455. doi:10.1126/science.1147417. PMID 17962522.
  9. ↑ Belezal, Sandra; Santos, A. M.; McEvoy, B.; Alves, I.; Martinho, C.; Cameron, E.; Shriver, M. D.; Parra, E. J.; Rocha, J. (2012). "The timing of pigmentation lightening in Europeans". Molecular Biology and Evolution. 30 (1): 24–35. doi:10.1093/molbev/mss207. PMC 3525146. PMID 22923467.
  10. ↑ S. Beleza et al., "The Timing of Pigmentation Lightening in Europeans", Molecular Biology and Evolution, Volume 30, Issue 1, 1 January 2013, Pages 24–35, doi:10.1093/molbev/mss207. see also: E. R. Jones, "Upper Palaeolithic genomes reveal deep roots of modern Eurasians", Nature Communications volume 6, Article number: 8912 (2015), https://www.nature.com/articles/ncomms9912 doi:10.1038/ncomms9912].
  11. ↑ Fu, Qiaomei; Posth, Cosimo (May 2, 2016). "The genetic history of Ice Age Europe". Nature. doi:10.1038/nature17993.
  12. ↑ Matteo Fumagalli et al., "Greenlandic Inuit show genetic signatures of diet and climate adaptation", Science Vol. 349, Issue 6254, 18 Sep 2015, pp. 1343-1347, DOI: 10.1126/science.aab2319
  13. ↑ Kenneth L. Beals, Courtland L. Smith, and Stephen M. Dodd, "Brain Size, Cranial Morphology, Climate, and Time Machines" CURRENT ANTHROPOLOGY V01. 25, NO 01984 (3 June 1984), fig. p. 304. "We offer an alternative hypothesis that suggests that hominid expansion into regions of cold climate produced change in head shape. Such change in shape contributed to the increased cranial volume. Bioclimatic effects directly upon body size (and indirectly upon brain size) in combination with cranial globularity appear to be a fairly powerful explanation of ethnic group differences." "Morphological Adaptation to Climate in Modern Homo sapiens Crania: The Importance of Basicranial Breadth". Wioletta Nowaczewska, Pawe D browski1 and Lukasz KuŸmiñski.
  14. ↑ Beals, Kenneth; Smith, Courtland; Dodd, Stephen (1984). "Brain Size, Cranial Morphology, Climate, and Time Machines" (PDF). Current Anthropology. 12 (3): 301–330. doi:10.1086/203138.
  15. 1 2 John Hawks, Eric T. Wang, Gregory M. Cochran, Henry C. Harpending, and Robert K. Moyzis. Recent acceleration of human adaptive evolution. Proceedings of the National Academy of Sciences of the United States of America of America. Published online before print December 17, 2007, doi:10.1073/pnas.0707650104. PNAS December 26, 2007 vol. 104 no. 52 20753-20758. http://www.pnas.org/content/104/52/20753.short
  16. ↑ Peng, Y. et al. The ADH1B Arg47His polymorphism in East Asian populations and expansion of rice domestication in history. BMC Evolutionary Biology 10, 15 (2010).
  17. ↑ Ségurel, Laure; Bon, Céline (2017). "On the Evolution of Lactase Persistence in Humans". Annual Review of Genomics and Human Genetics. 18 (1): 297–319. doi:10.1146/annurev-genom-091416-035340. PMID 28426286. Ingram, Catherine J. E.; Mulcare, Charlotte A.; Itan, Yuval; Thomas, Mark G.; Swallow, Dallas M. (2008-11-26). "Lactose digestion and the evolutionary genetics of lactase persistence". Human Genetics. 124 (6): 579–591. doi:10.1007/s00439-008-0593-6. ISSN 0340-6717.
  18. ↑ Ilardo, M. A.; Moltke, I.; Korneliussen, T. S.; Cheng, J.; Stern, A. J.; Racimo, F.; de Barros Damgaard, P.; Sikora, M.; Seguin-Orlando, A.; Rasmussen, S.; van den Munckhof, I. C. L.; ter Horst, R.; Joosten, L. A. B.; Netea, M. G.; Salingkat, S.; Nielsen, R.; Willerslev, E. (2018-04-18). "Physiological and Genetic Adaptations to Diving in Sea Nomads". Cell. 173 (3): 569–580.e15. doi:10.1016/j.cell.2018.03.054. Gislén, A., Dacke, M., Kröger, R.H., Abrahamsson, M., Nilsson, D.-E., and Warrant, E.J., "Superior underwater vision in a human population of sea gypsies." Curr. Biol. 2003; 13: 833–836.
  19. ↑ Peter Frost, The Hajnal Line and Gene-Culture Coevolution in Northwest Europe, Advances in Anthroplogy Vol.7 No.3, August 2017, DOI: 10.4236/aa.2017.73011.
  20. 1 2 Byars, S. G.; Ewbank, D.; Govindaraju, D. R.; Stearns, S. C. (2009). "Natural selection in a contemporary human population". Proceedings of the National Academy of Sciences. 107 (suppl_1): 1787–1792. Bibcode:2010PNAS..107.1787B. doi:10.1073/pnas.0906199106. PMC 2868295. PMID 19858476.
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