A look at an early European

 

Kostenki Man, reconstructed by Mikhail Gerasimov (1907-1970). An early European who was not yet phenotypically European.

 

Who were the first Europeans? We now have a better idea, thanks to a new paper about DNA from a man who lived some 38,700 to 36,200 years ago. His remains were found at Kostenki, a well-known Upper Paleolithic site in central European Russia (Seguin-Orlando et al., 2014).

Kostenki Man tells us several things about the first Europeans and, more broadly, the first non-African humans:

The Neanderthal encounter

Modern humans received their Neanderthal admixture when they were just spreading out of Africa some 54,000 years ago. At that time, they had not yet encountered the Neanderthals and were entering the territory of the Skhul/Qafzeh hominids, a semi-archaic people of the Middle East. So we may have got our Neanderthal admixture indirectly. The Skhul/Qafzeh hominids had probably interbred with their Neanderthal neighbors to the north, and our ancestors may have then picked up this admixture while in the Middle East. 

When our ancestors spread farther north into Europe, some 45,000 to 42,000 years ago, they could have interbred directly with Neanderthals, but they didn't. Perhaps the two groups were just too different. They seem to have intermixed only via a third party that was neither fully modern nor fully archaic.

A strange detour ... and then another!

There was initially a large continuous population across northern Eurasia, perhaps composed of nomads who pursued wandering herds of reindeer across the European Plain and its eastward extension into central and northern Asia.

Not long before the time of Kostenki Man, these Northern Eurasians began to split into three regional groups: Western Eurasians, Eastern Eurasians, and the ancestors of Middle Eastern farmers. The degree of reproductive isolation is unclear, however, and gene flow may have continued between all three groups until the onset of the last ice age some 25,000 years ago. This may be why Kostenki Man does not fit perfectly into any of the three groups, although he is genetically closest to Western Eurasians.

Yes, Northern Eurasians were ancestral to the early farming peoples of the Middle East. It seems that early modern humans had to head north, learn to hunt reindeer, and then head south again before they could start farming. Sounds like a strange detour. Wouldn't it have been easier to stay put and do it locally? You know, Middle-Eastern hunter-gatherers becoming Middle Eastern farmers? Apparently not.

It gets even more convoluted. After some of those Northern Eurasians had gone south to the Middle East, some of their farming descendants "returned" to Europe and partially replaced its hunter-gatherers, particularly in southern and central Europe. This second detour has been greeted with disbelief. Dienekes (2014), for instance, has written: "I don't think many archaeologists would derive European farmers from Russia (Russia is actually one of the last places in Europe that became agricultural)."

True, but farming requires a mindset that may have come from those northern hunters (Frost, 2014). When Piffer (2013) looked at human variation in alleles at COMT, a gene linked to executive function, working memory, and intelligence, he found that northern hunting peoples had more in common with farming peoples than with other hunter-gatherers, "possibly due to the higher pressure on technological skills and planning abilities posed by the adverse climatic conditions."

That mindset made farming possible, but the first steps toward farming could not be taken in a cold climate. They had to be taken in a place with a long growing season and a wide variety of domesticable plants and animals, such as in the Middle East. Once farming had developed there, it could move back north, while taking along its technologies, its food crops, and its livestock species. 

Farming can develop in the tropics with a "tropical" mindset, but it looks very different. The farming that arose in West Africa is overwhelmingly women's work and seems to have wholly developed out of female plant gathering. The guinea fowl is the only animal that has been domesticated for food consumption in sub-Saharan Africa.

The Ice Age was not so bad 

The Upper Paleolithic humans of northern and eastern Europe did not die out during the last ice age, as was commonly thought. They survived the glacial maximum intact.

The European phenotype came later

Kostenki Man was dark-skinned, dark-eyed, and rather short. These details, curiously enough, appear not in the paper but in a review of the paper, published by the same journal, as well as in an interview with one of the authors (Associated Press, 2014; Gibbons, 2014). 

So we now have an upper bound for the emergence of the European phenotype, i.e., light skin and a diverse palette of hair and eye colors. The lower bound has been set by the remains of a Swedish hunter-gatherer, dated to 8,000 years ago, who had the "European" allele for light skin at the gene SLC24A5 (Skoglund et al., 2014).

Conclusion

My main criticism centers on the dating to 38,700 - 36,200 years ago. At the Kostenki site, the radiocarbon dating used to be some 10,000 years younger. It was then recalibrated to an older range of dates when a layer of volcanic ash at the site was attributed to a volcano that had erupted in southern Italy some 39,000 years ago. This recalibration was initially controversial, but the controversy has since subsided (Sinitsyn and Hoffecker, 2006). I would not rule out a subsequent re-recalibration.

By retrieving ancient DNA from an early modern human, we have made a key advance in human paleogenetics, perhaps more so than by sequencing the Neanderthal genome. We again see that evolution did not slow down with the emergence of anatomically and behaviorally modern humans some 60,000 years ago. It actually began to speed up, as humans began to enter not only new natural environments but also new cultural environments of their own making.

 

References 

Associated Press (2014). DNA study dates Eurasian split from East Asians, The Columbus Dispatch, November 6

http://hosted2.ap.org/OHCOL/07e34bb59e064cedb7e2776e8db4b4f7/Article_2014-11-06-EU--Eurasian%20Split/id-ae36fa368c634c7383d807942bd5fe67 

Dienekes (2014). Genome of Kostenki-14, an Upper Paleolithic European (Seguin-Orlando, Korneliussen, Sikora, et al. 2014), Dienekes' Anthropology Blog, November 7

http://dienekes.blogspot.ca/2014/11/genome-of-kostenki-14-upper-paleolithic.html  

Frost, P. (2014). The first industrial revolution, Evo and Proud, January 18

http://evoandproud.blogspot.ca/2014/01/the-first-industrial-revolution.html 

Gibbons, A. (2014). European genetic identity may stretch back 36,000 years, Science, News, November 6

http://news.sciencemag.org/archaeology/2014/11/european-genetic-identity-may-stretch-back-36000-years 

Piffer, D. (2013). Correlation of the COMT Val158Met polymorphism with latitude and a hunter-gather lifestyle suggests culture-gene coevolution and selective pressure on cognition genes due to climate, Anthropological Science, 121, 161-171.

https://lesacreduprintemps19.files.wordpress.com/2014/01/correlation-of-the-comt-val158met-polymorphism-with-latitude-and-a-hunter-gather-lifestyle-suggests-culturee28093gene-coevolution-and-selective-pressure-on-cognition-genes-due-to-climate.pdf 

Seguin-Orlando, A., T.S. Korneliussen, M. Sikora, A.-S. Malaspinas, A. Manica, I. Moltke, A. Albrechtsen, A. Ko, A. Margaryan, V. Moiseyev, T. Goebel, M. Westaway, D. Lambert, V. Khartanovich, J.D. Wall, P.R. Nigst, R.A. Foley, M.M. Lahr, R. Nielsen, L. Orlando, and E. Willerslev. (2014). Genomic structure in Europeans dating back at least 36,200 years, Science, Published online 6 November 2014

http://www.sciencemag.org/content/early/2014/11/05/science.aaa0114
http://www2.zoo.cam.ac.uk/manica/ms/2014_Seguin_Orlando_et_al_Science.pdf  

Sinitsyn, A.A., and J.F. Hoffecker. (2006). Radiocarbon dating and chronology of the Early Upper Paleolithic at Kostenki, Quaternary International, 152-153, 164-174.

http://www.sciencedirect.com/science/article/pii/S1040618206000206 

Skoglund, P., H. Malmstrom, A. Omrak, M. Raghavan, C. Valdiosera, T. Gunther, P. Hall, K. Tambets, J. Parik, K-G. Sjogren, J. Apel, E. Willersley, J. Stora, A. Gotherstrom, and M. Jakobsson. (2014). Genomic diversity and admixture differs for stone-age Scandinavian foragers and farmers, Science, 344 (6185), 747-750.

http://www.sciencemag.org/content/344/6185/747.short

 

SLC24A5: Reply to Greg Cochran

 

Ethiopian manuscript paintings (source: A. Davey). Ethiopians have a self-image that is lighter-skinned than their actual selves. If the prevalence of SLC24A5 is higher in Ethiopia than the degree of admixture from lighter-skinned peoples across the Red Sea, this discrepancy may be explained by social selection for lighter skin.

 

Greg Cochran has been asking why the “European” allele for SLC24A5 has been so successful, not only in Europe but also elsewhere. He seems to be hinting that this allele has a selective advantage that is unrelated to skin color.

I posted the following comments at his website. References have been inserted for this post.

 

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SLC24A5 is one of three genes involved in the whitening of European skin, the other two being SLC45A2 and TYRP1. This whitening occurred over a relatively short time and long after the entry of modern humans into Europe some 40,000 years ago. Sandra Beleza’s team estimates that all three genes “went white” between 11,000 and 19,000 years ago (Beleza et al, 2013). Victor Canfield’s team, working only with SLC24A5, estimates between 7,600 and 19,200 years ago (Canfield et al., 2014).

So, yes, white European skin is not an adaptation to weaker sunlight; otherwise, it would have evolved much earlier. Are we looking at some pleiotropic effect then? In that case, this effect would involve not only SLC24A5 but the other two genes as well. Perhaps, but I’d like to see the evidence.

No, I’m not going to invoke sexual selection to explain the apparent success of the “European” allele for SLC24A5. Sexual selection, especially sexual selection of women, occurs under very limited circumstances.  I believe that there was an episode of very intense sexual selection of women, but this episode was confined to northern and eastern Europe during the time frame of 10,000 to 20,000 years ago, i.e., the last ice age (Frost, 2006; Frost, 2008).

How then do we explain the much greater geographic and historical success of this allele? The answer is part of the larger one of why lighter-skinned folks have done better than darker-skinned folks. Mean temperature is inversely correlated with technological complexity, even going back to the hunter-gatherer stage of cultural evolution. This is partly because colder environments created a greater need for heat conservation (by means of tailored clothing and insulated shelters) and partly because their food resources were more dispersed and typically available for short periods of time. There was thus strong selection in such environments for time budgeting, forward planning, and the ability to manage storage technologies (ice cellars) and untended facilities (traps, snares). Northern hunters were pre-adapted for technological complexity and thus better able to exploit the sort of complex cultural environments that developed much later in time (Hoffecker, 2002, pp. 6-12).

Is this the whole story? You point to Ethiopians as an example where SLC24A5 seems to be present at a higher frequency than Caucasian admixture. This discrepancy can probably be explained by social selection for lighter skin, as indicated by an Israeli study that found light-skin preference among Falasha children (Munitz et al., 1987).  This preference may be learned, although there is evidence that people are predisposed to associate lighter skin with certain good qualities (as a result of a mental algorithm that uses skin tone for identification of women and young infants) (Frost, 2011). For whatever reason, social selection for lighter skin is a reality in Ethiopia, and it probably has had some impact on the prevalence of SLC24A5.

 

Question from ‘RS’: Sexual selection, especially sexual selection of women, occurs under very limited circumstances. So you are equally attracted to all women?

 

Sexual selection is not the same thing as sexual preference. In other words, what you prefer is not necessarily what you will get. It all comes down to the law of supply and demand.

Sexual selection occurs when too many of one sex have to compete for too few of the other. Normally, the males have to compete for the females. The reverse is rare in nature. It happens when (1) males die much earlier than females do and (2) the costs of providing for a second mate are too high for almost all males. In human hunter-gatherers, the ratio of men to women on the mate market declines as one moves away from the equator. It reaches its lowest point in open steppe-tundra environments, where almost all food is obtained by men through hunting and where male mortality is high because men have to pursue mobile herds of game over long distances in a cold environment that offers few alternate sources of food.

Steppe-tundra covered most of northern and eastern Europe during the Late Pleniglacial (25,000 to 10,000 BP). I use the term “last ice age” in order to be better understood. There was a series of ice ages during the Pleniglacial (70,000 to 10,000 BP), but modern humans had to adapt only to the last one. To date, it looks like the most visible features of Europeans (white skin, multi-hued hair and eyes) evolved during the time window of the Late Pleniglacial. If the estimates by Beleza and Canfield are to be believed, the time window is somewhere between 20,000 and 10,000 BP.

These estimates seem to conflict with the recent findings of brown-skinned Mesolithic Europeans from Spain (7,000 BP) and Luxembourg (8,000 BP). I would argue that the changes to hair, eye, and skin color took place within a relatively restricted geographic area (essentially the plains of northern and eastern Europe) and later spread outward. It’s silly to argue that these changes must have originated in the Middle East, since the Middle East was inhabited by an African-like population until at least 12,000 BP. This population (the Natufians) shows no biological continuity with later Middle Easterners.

 

References

 

Beleza, S., Murias dos Santos, A., McEvoy, B., Alves, I., Martinho, C., Cameron, E., Shriver, M.D., Parra E.J., and Rocha, J. (2013). The timing of pigmentation lightening in Europeans. Molecular Biology and Evolution, 30, 24-35.

http://mbe.oxfordjournals.org/content/30/1/24.short 

Canfield, V.A., A. Berg, S. Peckins, S.M. Wentzel, K.C. Ang, S. Oppenheimer, and K.C. Cheng. (2014). Molecular phylogeography of a human autosomal skin color locus under natural selection, G3, 3, 2059-2067.

http://www.g3journal.org/content/3/11/2059.full 

Cochran, G. (2014). Shades of pale, January 27, West Hunter

http://westhunt.wordpress.com/2014/01/27/shades-of-pale/

Frost, P. (2011). Hue and luminosity of human skin: a visual cue for gender recognition and other mental tasks, Human Ethology Bulletin, 26(2), 25-34. http://media.anthro.univie.ac.at/ISHE/index.php/bulletin/bulletin-contents 

Frost, P. (2008). Sexual selection and human geographic variation, Special Issue: Proceedings of the 2nd Annual Meeting of the NorthEastern Evolutionary Psychology Society. Journal of Social, Evolutionary, and Cultural Psychology, 2(4), pp. 169-191.

http://www.jsecjournal.com/articles/volume2/issue4/NEEPSfrost.pdf

Frost, P. (2006). European hair and eye color - A case of frequency-dependent sexual selection? Evolution and Human Behavior, 27, 85-103.

Hoffecker, J.F. (2002). Desolate Landscapes. Ice-Age Settlement in Eastern Europe. New Brunswick: Rutgers University Press.

Munitz, S., B. Priel, and A. Henik. (1987). Color, skin color preferences and self color identification among Ethiopian and Israeli born children, in M. Ashkenazi and A. Weingrod (eds.), Ethiopian Jews and Israel. (pp. 74-84). New Brunswick (U.S.A.): Transaction Books.