Debate over recent human evolution: pros and cons

Acceleration of recent human evolution. Age distribution of alleles under selection (Hawks et al. 2007)

A decade has passed since a research team led by John Hawks published a strange finding: human genetic evolution accelerated more than a hundred-fold some 10,000 years ago. This was when hunting and gathering began to give way to farming, which in turn brought other changes, all of which required adjustments to mind and body. All in all, new cultural and natural environments have reshaped 7% of the human genome over the last 40,000 years:

Some of the most radical new selective pressures have been associated with the transition to agriculture. For example, genes related to disease resistance are among the inferred functional classes most likely to show evidence of recent positive selection. Virulent epidemic diseases, including smallpox, malaria, yellow fever, typhus, and cholera, became important causes of mortality after the origin and spread of agriculture. Likewise, subsistence and dietary changes have led to selection on genes such as lactase. (Hawks et al. 2007)

Instead of adapting only to the natural environment, humans have adapted to cultural creations of their own making, things like prepared food, clothing, shelter, way of life, social organization, sedentary versus nomadic living, religious strictures, and so on.

This finding may come as a surprise. As a university student I learned that culture has greatly reduced the importance of natural selection in our species. Instead of adapting genetically to our environment, we adapt culturally. That was, and still is, the normative view.

Debates in the scientific literature: 2008 to 2010

So what are we to believe? Perhaps there have been other findings over the last decade, either pro or con.

In 2008, a research team led by Matthieu Foll and Oscar Gaggiotti calculated a higher estimate of recent human evolution: over 23% of the human genome. By using an FST test and data from 53 human populations, they found evidence for selection at 131 out of 560 random loci. When this methodology was repeated with other random loci, the same estimate of 23% came up.

A review paper by Joshua Akey notes, however, that these genome-wide scans are problematic in two ways. On the one hand, they miss genes that are known to have contributed to recent human evolution. On the other, these different scans disagree on the regions of the human genome that have been evolving rapidly:

Strikingly, only 722 regions (14.1%) were identified in two or more studies, 271 regions (5.3%) were identified in three or more studies, and 129 regions (2.5%) were identified in four or more studies (Fig. 1). Furthermore, the integrated map of positive selection does not include several of the most compelling genes with well-substantiated claims of positive selection, such as G6PD and DARC. (Akey 2009)

A closer look at the data suggests that recent evolution is highly localized on the human genome. If the size of the region is decreased, the probability increases of that region containing either no genes at all under selection or several under selection. Making the regions smaller makes it easier, strangely enough, to find regions with multiple genes under selection. "This paradoxical observation [...] is due to the marked difference in the average size of regions identified in single versus multiple studies (~80 kb and 300 kb, respectively)" (Akey 2009).

So estimates of recent human evolution seem to range from a low of 7% of the genome (Hawks et al. 2007) to a high of 23% (Foll and Gaggiotti 2008). Even the 7% estimate, however, has been criticized in the literature, specifically by two papers. The first one was Pickrell et al. (2009):

We find that putatively selected haplotypes tend to be shared among geographically close populations. [...]. This suggests that distinguishing true cases of selection from the tails of the neutral distribution may be more difficult than sometimes assumed, and raises the possibility that many loci identified as being under selection in genome scans of this kind may be false positives. Reports of ubiquitous strong (s = 1 - 5%) positive selection in the human genome (Hawks et al. 2007) may be considerably overstated. (Pickrell et al. 2009)

The argument here is that a genetic variant with high selective value should spread beyond its area of origin, instead of remaining bottled up there. Yet this is unlikely for two reasons. First, recent variants, by definition, have little time to spread very far. Second, and more importantly, the selective value of a genetic variant is a function of its natural and cultural environment. A variant that succeeds in one environment will be less successful in another.

The criticism made by Pickrell et al. (2009) was repeated by Hermisson (2009). If the data are controlled for geographic region, the evidence for recent human evolution virtually disappears:

[...] introduction of hierarchical structure based on five previously established geographic regions reduces the frequency of selection candidates from 23% (Foll and Gaggiotti, 2008) to no more than expected by chance (that is, comparable with the 1% significance level applied). (Hermisson 2009)

The implication is that recent human evolution is largely due to founder effects and other forms of genetic drift. Genetic drift, however, would not produce the observed signatures of natural selection, as Nicholas Wade noted in a review of this research the following year:

One of the signatures of natural selection is that it disturbs the undergrowth of mutations that are always accumulating along the genome. As a favored version of a gene becomes more common in a population, genomes will look increasingly alike in and around the gene. Because variation is brushed away, the favored gene's rise in popularity is called a sweep. Geneticists have developed several statistical methods for detecting sweeps, and hence of natural selection in action. (Wade 2010).

Moreover, this signature is much stronger in some geographic regions than in others:

A new approach to identifying selected genes has been developed by Anna Di Rienzo at the University of Chicago. Instead of looking at the genome and seeing what turns up, Dr. Di Rienzo and colleagues have started with genes that would be likely to change as people adopted different environments, modes of subsistence and diets, and then checked to see if different populations have responded accordingly.

She found particularly strong signals of selection in populations that live in polar regions, in people who live by foraging, and in people whose diets are rich in roots and tubers. [..] The fewest signals of selection were seen among people who live in the humid tropics, the ecoregion where the ancestral human population evolved. [...] there seem to be more genes under recent selection in East Asians and Europeans than in Africans, possibly because the people who left Africa were then forced to adapt to different environments. "It's a reasonable inference that non-Africans were becoming exposed to a wide variety of novel climates," says Dr. Stoneking of the Max Planck Institute. (Wade 2010)

Joshua Akey remains cautious on this point:

A specific example of the difficulties in interpreting signatures of spatially varying selection is the observation that non-African populations tend to show more evidence for recent positive selection relative to African populations (Akey et al. 2004; Storz et al. 2004; Williamson et al. 2007; but see Voight et al. 2006). While this may be due to increased selection as humans migrated out of Africa and were confronted with new environmental pressures (such as novel climates, diets, and pathogens), differences in demographic history or rates of recombination and mutation between African and non-African populations may obscure the relationship between signatures of selection across populations. (Akey 2009)

Since 2010: consensus among some, skepticism and hostility among others

After 2010, Google Scholar turns up only brief references to the original paper by John Hawks et al., most of them favorable or neutral in tone. If one judges by the scientific literature alone, there seems to be broad support for the notion that recent evolution has accelerated in our species. And the original estimate of 7% recent evolutionary change may err on the low side

Yet many people remain unconvinced. Last week Razib Khan reproached me: "you take the accelerationist hypothesis as a given. it's not. at least at that magnitude (i think most ppl agree holocene resulted in faster rate of change)." Indeed, most people seem to view these findings with incredulity, to put it mildly, as a journalist from Discover magazine found:

Not surprisingly, the new findings have raised hackles. Some scientists are alarmed by claims of ethnic differences in temperament and intelligence, fearing that they will inflame racial sensitivities. Other researchers point to limitations in the data. Yet even skeptics now admit that some human traits, at least, are evolving rapidly, challenging yesterday's hallowed beliefs. (McAuliffe 2009)

A decade later, the barriers to acceptance are still considerable. Chen et al. (2016) identifies four sources of opposition:

- Evolutionary psychologists, who believe that human nature took shape in the Pleistocene. According to this view, genetic influences on behavior are too complex to have changed much since then.

- Cultural determinists, who believe that "once humans invented culture, natural selection was halted because humans could overcome nature through culture."

- People who point out that we are all 99.9% genetically alike. So there is little room for genetic differences within our species.

- People who believe that genetic differences are inconsequential to human behavior.

There are counter-arguments to the above. Genetic influences on existing behaviors can evolve very fast (Harpending and Cochran 2002). And that figure of 99.9% genetic identity is an over-estimate, the best estimate being 99%. Even if we assume that this 1% difference is spread evenly across the genome, that tiny difference could significantly alter the way each and every gene works.

Nonetheless, such counter-arguments would still leave many unconvinced. And others wouldn't even listen. Some beliefs are foundational, being difficult to challenge without seeming to attack an entire worldview. In such cases, reactions can be nasty.

That's normal. Strong disagreement is the stuff of scientific debate. What's less normal is that some people will seek not to debate but to judge and punish. That fate befell a coauthor of the 2007 paper on recent human evolution. In 2015, the Southern Poverty Law Center (SPLC) prepared and published a file on Henry Harpending ... under the heading "Extremist Info." The opening words sounded no less ominous:

Henry Harpending is a controversial anthropologist at the University of Utah who studies human evolution and, in his words, "genetic diversity within and between human populations."

The file went on to state:

Harpending is most famous for his book, co-authored with frequent collaborator Gregory Cochran, The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, which argues that humans are evolving at an accelerating rate, and that this began when the ancestors of modern Europeans and Asians left Africa. (SPLC 2015)

One wonders what exactly is intended by this public naming and shaming. After all, the SPLC has no legal mandate to judge and punish, although it seems to think so. Indeed, it acts like a law-enforcement agency without being constrained by the law and without being answerable to an elected body.

Henry Harpending died scarcely a year later, yet his file is still there on the SPLC website. Even in death he's still a grave threat … as is apparently anyone else who believes in the evidence for recent human evolution.

References

Akey, J.M. (2009). Constructing genomic maps of positive selection in humans: Where do we go from here? Genome Research 19: 711-722.

https://pdfs.semanticscholar.org/9199/dab2542982e282eaf28fc303008c20583db7.pdf

Chen, C., R.K. Moyzis, X. Lei, C. Chen, and Q. Dong. (2016). "The enculturated genome: Molecular evidence for recent divergent evolution in human neurotransmitter genes." In Joan Y. Chiao, Shu-Chen Li, Rebecca Seligman, Robert Turner (eds). The Oxford Handbook of Cultural Neuroscience. Oxford.

https://books.google.ca/books?id=rtbiCgAAQBAJ&printsec=frontcover&hl=fr&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false

Cochran, G. and H. Harpending. (2010). The 10,000 Year Explosion: How Civilization Accelerated Human Evolution, New York: Basic Books.

Foll, M., and O. Gaggiotti. (2008). A Genome-Scan Method to Identify Selected Loci Appropriate for Both Dominant and Codominant Markers: A Bayesian Perspective. Genetics 180(2):977-993.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2567396/

Harpending, H., and G. Cochran, (2002). In our genes, Proceedings of the National Academy of Science. USA. 99(1):10-12.

https://s3.amazonaws.com/academia.edu.documents/43528175/In_our_genes20160308-5744-8wzdxj.pdf?AWSAccessKeyId=AKIAIWOWYYGZ2Y53UL3A&Expires=1524495810&Signature=XEX4Jqbe%2FAD3Faud9Re0M1ECEys%3D&response-content-disposition=inline%3B%20filename%3DIn_our_genes.pdf

Hawks, J., E.T. Wang, G.M. Cochran, H.C. Harpending, and R.K. Moyzis. (2007). Recent acceleration of human adaptive evolution, Proceedings of the National Academy of Science USA 104:20753-20758.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2410101/

Hermisson, J. (2009). Who believes in whole-genome scans for selection? Heredity 103, 283-284

https://www.nature.com/articles/hdy2009101  

McAuliffe K. (2009). They don't make Homo sapiens like they used to. Our species-and individual races-have recently made big evolutionary changes to adjust to new pressures. Discover February 9

http://discovermagazine.com/2009/mar/09-they-dont-make-homo-sapiens-like-they-used-to

Pickrell, J.K., G. Coop, J. Novembre, S. Kudaravalli, J.Z. Li, D. Absher, B.S. Srinivasan, G.S. Barsh, R.M. Myers, M.W. Feldman, and J.K. Pritchard. (2009). Signals of recent positive selection in a worldwide sample of human populations. Genome Research 19(5): 826-837

http://europepmc.org/articles/pmc2675971  

SPLC. (2015). Henry Harpending. Extremist Info

https://www.splcenter.org/fighting-hate/extremist-files/individual/henry-harpending

Wade, N. (2010). Adventures in very recent evolution. The New York Times, July 19

https://www.nytimes.com/2010/07/20/science/20adapt.html

Do Chinese people get bored less easily?

 

Boy in a café (S. Yao, Wikicommons)

 

All humans were once hunter-gatherers. Back then, versatility came with the territory. There were only so many game animals, and they differed a lot in size, shape, and color. So you had to enjoy switching back and forth from one target animal to another. And you had to enjoy moving from one place to another. Sooner or later you'd have to.

Beginning 10,000 years ago, farmers made their appearance. Now monotony came with the territory. A plot of land wasn't something you could forget while you took off somewhere else. It needed constant care. The tasks were also more repetitive: ploughing, sowing, harvesting ...

Things worsened as farming became more advanced. You had to focus on one crop and a limited number of key tasks.

Different means of subsistence have selected for different mental traits, and this selection has had genetic consequences. Monotony avoidance has a heritability of 0.53 (Saudino, 1999). This predisposition has usually been a handicap in modern societies, so much so that it often leads to criminality. Males with a history of early criminal behavior tend to score high on monotony avoidance, as well as on sensation seeking and low conformity (Klinteberg et al., 1992).

Today, if you have trouble fitting into your society, you might still survive and reproduce. In the past, you probably wouldn’t. Other people would take your place in the gene pool and, over successive generations, their mental makeup would become the norm.

That’s gene-culture co-evolution. We have reshaped the world we live in, and this human-made world has reshaped us. After describing how our ancestors radically changed their environment, Razib goes on to write: "We were the authors of those changes, but in the process of telling that story, we became protagonists within it" (Khan, 2014).

 

China: a case study

Advanced farming—intensive land use, task specialization, monoculture—has profoundly shaped East Asian societies, particularly China. This is particularly so for rice farming. Because the paddies need standing water, rice farmers must work collectively to build, dredge, and drain elaborate irrigation networks. Wheat farming, by comparison, requires no irrigation and only half as much work.

Advanced farming seems to have favored a special package of predispositions and inclinations, including greater acceptance of monotony. This has been shown in two recent studies.

The first one was about boredom and how people experience it in their lives. The results from the 775 Chinese participants were then compared with the results from a previous survey of 572 Euro-Canadians. It was found that the Chinese participants were less likely to feel bored in comparable situations. They seemed to value low-arousal (calm, relaxation) versus high arousal (excitement, elation) in the case of Euro-Canadians (Ng et al., 2014). 

The authors attributed their findings to cultural learning. One may wonder, however, why preference for low arousal persists in the face of China’s massive influx of high-arousal Western culture.

Relational thinking, collectivism, and favoritism

The second study had the aim of seeing whether the sociological differences between rice farmers and wheat farmers have led to differences in mental makeup. When 1,162 Han Chinese performed a series of mental tasks, the results differed according to whether the participants came from rice-farming regions or wheat-farming regions (Talhelm et al., 2014).

When shown a list of three items, such as “train”, “bus”, and “tracks”, and told to choose two items that pair together, people from rice-farming regions tended to choose "train and tracks," whereas people from wheat-farming regions tended to choose "train and bus." The former seemed to be more relational in their thinking and the latter more abstract. This pattern held up even in neighboring counties along China's rice-wheat border. People from the rice side of the border thought more relationally than did people from the wheat side.

A second task required drawing pictures of yourself and your friends. In a prior study, Americans drew themselves about 6 mm bigger than they drew their friends, Europeans drew themselves 3.5 mm bigger, and Japanese drew themselves slightly smaller. In the present study, people from rice regions were more likely than people from wheat regions to draw themselves smaller than they drew their friends. On average, people from wheat regions self-inflated 1.5 mm, and people from rice regions self-deflated -0.03 mm.

A third task required imagining yourself doing business with (i) an honest friend, (ii) a dishonest friend, (iii) an honest stranger, and (iv) a dishonest stranger. This person might lie, causing you to lose money. Or this person might be honest, causing you to make money. You could reward or punish this person accordingly. A previous study found that Singaporeans rewarded friends much more than they punished them. Americans were much more likely to punish friends for bad behavior. In this study, people from rice regions were more likely to remain loyal to friends regardless.

Interestingly, these findings came from people with no connection to farming at all. They grew up in a modern urban society, and most were too young to have known the China that existed before the economic reforms of the late 1970s.  It looks like rice regions have favored hardwiring of certain psychological traits: less abstract thinking and more relational thinking, less individualism and more collectivism, and less impartiality toward strangers and more favoritism toward kin and friends.

 

Why farming sucks, for you but not for me

These findings corroborate the ethnographic literature on the differences in mentality between hunter-gatherers and farmers. Hunter-gatherers typically see farming as a kind of slavery, and they have trouble understanding well-meaning outsiders who want to turn them into land-slaves.

Yes, for the same land area, farming can produce much more food. But it's hard work, not only physically but mentally as well. Humans had to undergo a change in mentality before they could make the transition from hunting and gathering to farming

Those humans ended up transforming not just their physical landscape but also their social and cultural landscape … and ultimately themselves. By creating new values and social relations, they changed the rules for survival and reproduction, thereby changing the sort of mentality that future generations would inherit.

Humans transformed the world through farming, and the world returned the favor.

  

References

 

Khan, R. (2014). Our cats, ourselves, The New York Times, The Opinion Pages, November 24

http://www.nytimes.com/2014/11/25/opinion/our-cats-ourselves.html

Klinteberg, B., K. Humble, and D. Schalling. (1992). Personality and psychopathy of males with a history of early criminal behaviour, European Journal of Personality, 6(4), 245-266.

http://psycnet.apa.org/psycinfo/1993-18051-001
 

Ng, A.H., Y. Liu, J-Z. Chen, and J.D. Eastwood. (2014). Culture and state boredom: A comparison between European Canadians and Chinese, Personality and Individual Differences, 75, 13-18.

http://www.sciencedirect.com/science/article/pii/S0191886914006321
 

Saudino, K.J., J.R. Gagne, J. Grant, A. Ibatoulina, T. Marytuina, I. Ravich-Scherbo, and K. Whitfield. (1999). Genetic and environmental influences on personality in adult Russian twins, International Journal of Behavioral Development, 23, 375-389.

http://jbd.sagepub.com/content/23/2/375.short
 

Talhelm, T., X. Zhang, S. Oishi, C. Shimin, D. Duan, X. Lan, and S. Kitayama. (2014). Large-scale psychological differences within China explained by rice versus wheat agriculture, Science, 344, 603-607.

http://internationalpsychoanalysis.net/wp-content/uploads/2014/05/RiceversusWheatScience-2014-Talhelm-603-8.pdf

Did Europeans become white in historic times?

 

Tătăroaice – Petre Iorgulescu-Yor (source). Today, the steppes north of the Black Sea lie within the European world—politically, culturally, and demographically. Not so long ago, they were home to nomads of Central Asian origin.

 

A new study shows that Europeans underwent strong selection for white skin, non-brown eyes, and non-black hair … during historic times!

Here we present direct estimates of selection acting on functional alleles in three key genes known to be involved in human pigmentation pathways—HERC2, SLC45A2, and TYR—using allele frequency estimates from Eneolithic, Bronze Age, and modern Eastern European samples and forward simulations. Neutrality was overwhelmingly rejected for all alleles studied, with point estimates of selection ranging from around 2-10% per generation. Our results provide direct evidence that strong selection favoring lighter skin, hair, and eye pigmentation has been operating in European populations over the last 5,000 y. (Wilde et al., 2014) 

 

If true, this finding would contradict other recent findings. Two studies have found a much earlier time frame for the whitening of European skin: 11,000 to 19,000 years ago (Beleza et al., 2013) and 7,600 to 19,200 years ago (Canfield et al., 2014). Two studies of ancient DNA indicate that non-brown eyes were already in existence 7,000 years ago in Spain (Olalde et al., 2014) and 8,000 years ago in Luxembourg (Lazaridis et al., 2013). Moreover, the genes responsible are the same as the ones in above quote. 

So who is right and who is wrong? All of these studies are probably right, but only for some early Europeans and not for all. In the latest study, the samples come from a very small part of Europe—the steppes north of the Black Sea:²

Ancient DNA was retrieved from 63 out of 150 Eneolithic (ca. 6,500-5,000 y ago) and Bronze Age (ca. 5,000-4,000 y ago) samples from the Pontic-Caspian steppe, mainly from modern-day Ukraine. […] We also genotyped the three pigmentation-associated SNPs in a sample of 60 modern Ukrainians (28) and observed an increase in frequency of all derived alleles between the ancient and modern samples from the same geographic region (Table 1 and Fig. S1). This implies that the pigmentation of the prehistoric population is likely to have differed from that of modern humans living in the same area.

[…] Inferring natural selection based on temporal differences in allele frequency requires the assumption of population continuity. To this end we compared the 60 mtDNA HVR1 sequences obtained from our ancient sample to 246 homologous modern sequences (29–31) from the same geographic region and found low genetic differentiation (F_ST = 0.00551; P = 0.0663) (32). Coalescent simulations based on the mtDNA data, accommodating uncertainty in the ancient sample age, failed to reject population continuity under a wide range of assumed ancestral population size combinations. (Wilde et al., 2014)

The authors are placing the burden of proof on the wrong null hypothesis when they state that their simulations “failed to reject population continuity.” The null hypothesis should be population discontinuity. For example, Swedes and Greeks differ in skin tone and eye color, and if we compare their autosomal DNA we get a comparable F_ST of 0.0084 (Genetic History of Europe, 2014). Admittedly, F_ST is different with mitochondrial DNA.

I suspect the authors ruled out population discontinuity because their F_ST seemed incompatible with a non-European population giving way to a European one. If so, they forgot one thing. They were comparing a population of the present with one that existed some 5,000 years ago. If you go farther and farther back in time, any human population will look more and more ancestral to a present-day population. This is especially so in northern Eurasia, where a population ancestral to both Europeans and Amerindians existed some 20,000 years ago. Yes, the F_ST does seem incompatible with a non-European population giving way to a European one, but this is because the ancient DNA comes from a non-European population that was closer to the time of common origin for all northern Eurasians.

This ancient DNA may come from a mixed European/Central Asian population or an intermediate and now extinct population, perhaps similar to the Lapps. If we look at the derived (European) alleles for the three genes in question (HERC2, SLC45A2, TYR), the frequencies fall halfway between those of Europeans and Asians (see Table 1 in the paper). In any case, this population does not have to be of non-European origin to be noticeably darker in skin color. As shown by the recent Mesolithic findings from Luxembourg and Spain, there used to be apparently native dark-skinned populations in the heart of Europe.

 

Historical background 

The hypothesis of population discontinuity becomes even more plausible if we look at the history of this region. Today, the steppes north of the Black Sea lie within the European world—politically, culturally, and demographically. Not so long ago, they were home to nomads of Central Asian origin. The latest of them, the Tatars, held sway until the 18th century.

The Tatars intermixed extensively with Slavic wives and concubines, so much so that they now look almost as fair as other Europeans. But they were originally quite swarthy, as attested by medieval sources. In a 14th-century romance, The King of Tars, a Tatar Khan converts to Christianity and turns white in the baptismal water. Two other chronicles of the same period describe how a Tatar Khan's Christian concubine bears him a son white on one side and black on the other. When baptized, the child emerges from the water white on both sides (Hornstein, 1941; Metlitzki, 1977, p. 137).

Medieval writers often noticed this difference in skin color. Genoese notaries usually described Tatar slaves as olive-skinned (Plazolles Guillen, 2012, p. 119). Florentine acts of sale give the following numerical breakdown of Tatar slaves by skin color: black 2, brown 18, olive 161, fair 11, reddish 5, white 45 (Epstein, 2001, p. 108). During a trial, a slave tried to regain her freedom by claiming to be Russian and, hence, Christian. Her owner rebuked her, saying: “You’ve lied to me. You look more like a Tatar, not at all like a Russian” (Plazolles Guillen, 2012, p. 119).

The Tatars were preceded by other nomads of Central Asian origin. The Scythians (8th to 2nd century BC) were likewise described as dark-skinned. Hippocrates wrote: “The Scythian race are tawny from the cold, and not from the intense heat of the sun, for the whiteness of the skin is parched by the cold, and becomes tawny” (Hippocrates).

One can find references to the contrary (Scythians, 2014). Keep in mind that the word “Scythian” was often used in the ancient world to encompass all northern peoples:

To the ancient Greeks the Scythians, Sarmatians, Germans, and Goths were the remote northern races of antiquity. Geographically near to one another, they were often grouped together under the term “Scythians,” which by the third century B.C.E. no longer had an ethnic or national connotation and had come to designate the peoples of the remote north. (Goldenberg, 2003, p. 43)

The term “Scythian” may also have subsumed different peoples north of the Black Sea, some of whom came from Central Asia and others from areas farther north and west.

 

Conclusion

Because this region is on the periphery of the European world and has been exposed to migrations from Central Asia, population change is a likelier explanation for the findings of Wilde et al.

These findings are nonetheless interesting. Together with the ancient DNA from Mesolithic hunter-gathers in Spain and Luxembourg, we have further proof that many early Europeans were brown-skinned. Indeed, this seems to have been the physical appearance of all Europeans during their first 20,000 years in Europe. Only later, within the time frame of 20,000 to 10,000 years ago, did some of them become white.

This may seem surprising to those who believe that white skin is an adaptation to weak sunlight at high latitudes. It was thought that Europeans became white because their ancestors no longer needed dark pigmentation to protect themselves against sunburn and skin cancer. Meanwhile, light pigmentation became necessary to maintain synthesis of vitamin D. There was admittedly the example of dark-skinned peoples who have long lived at similar latitudes in Asia and North America, but that counterfactual was attributed to the availability of vitamin D from a marine diet, such as among the Inuit of northern Canada.
 

Wilkes et al. do, in fact, address the apparent contradiction between their findings and the hypothesis that ancestral Europeans became white to maintain adequate production of vitamin D in their skin. In their Discussion section, they suggest that the shift from hunting and gathering to farming led to a decrease in dietary vitamin D (from fatty fish and animal liver). The main problem with this explanation is that farming came late to many parts of Europe: about 2,000 to 3,000 years ago for East Baltic peoples and less than 3,000 years ago for Finnish peoples (and incompletely at that). This leaves a very narrow time frame for evolution from brown skin to white skin. Ultimately, this question will be resolved with retrieval of ancient DNA from these populations.

 

Notes

1. Although Wilde et al. mention hair color, they did not study the main hair-color gene, MC1R.

2. Razib Khan has a great map of the ancient DNA samples.

 

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 

Epstein, S.A. (2001). Speaking of Slavery. Color, Ethnicity, & Human Bondage in Italy, Ithaca: Cornell University Press. 

Genetic History of Europe. (2014). Wikipedia

http://en.wikipedia.org/wiki/Genetic_history_of_Europe

Goldenberg, D.M. (2003). The Curse of Ham. Race and Slavery in early Judaism, Christianity, and Islam, Princeton: Princeton University Press. 

Hippocates. On Airs, Waters, and Places, part 20. Translated by Francis Adams

http://classics.mit.edu/Hippocrates/airwatpl.20.20.html

Hornstein, L.H.  (1941). New analogues to the King of Tars, Modern Language Review, 36, 433-442. 

Khan, R. (2014). Descent and selection is a bugger: Black Kurgans, March 12, The Unz Review: An Alternative Media Selection

http://www.unz.com/gnxp/descent-and-selection-is-a-bugger/ 

Lazaridis, I., Patterson, N., Mittnik, A., Renaud, G., Mallick, S., et al. (2013). Ancient human genomes suggest three ancestral populations for present-day Europeans, BioRxiv, December 23.

http://biorxiv.org/content/early/2013/12/23/001552.full-text.pdf+html

Metlitzki, D. (1977). The Matter of Araby in Medieval England, New Haven and London, Yale University Press. 

Olalde, I., M.E. Allentoft, F. Sanchez-Quinto, G. Saintpere, C.W.K. Chiang, et al. (2014).  Derived immune and ancestral pigmentation alleles in a 7,000-year-old Mesolithic European, Nature, early view

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12960.html

Plazolles Guillen, F. (2012). “Negre e de terra de negres infels …”: Servitude de la couleur (Valence, 1479-1516), in R. Botte and A. Stella (eds.) Couleurs de l’esclavage sur les deux rives de la Méditerranée (Moyen Âge – xx^e siècle), pp. 113-158, Paris: Karthala. 

Scythians. (2014). Wikipedia

http://en.wikipedia.org/wiki/Scythians  

Wilde, S., A. Timpson, K. Kirsanow, E. Kaiser, M. Kayser, M. Unterländer, N. Hollfelder, I.D. Potekhina, W. Schier, M.G. Thomas, and J. Burger. (2014). Direct evidence for positive selection of skin, hair, and eye pigmentation in Europeans during the last 5,000 y, Proceedings of the National Academy of Sciences, published ahead of print.

http://www.pnas.org/content/early/2014/03/05/1316513111.full.pdf+html

The brown man with blue eyes

Venus of Willendorf (30,000 – 27,000 BP). Is that a special headdress … or peppercorn hair? (source: Matthias Kabel)

Europeans already had blue eyes while still hunter-gatherers. This is what we’ve learned after retrieving ancient DNA from two Mesolithic individuals, one from Luxembourg, dated to 8,000 years ago, and another from Spain, dated to 7,000 years ago (Dienekes, 2013; Lazaridis et al.,2013). These are late hunter-gatherers, so there is always the possibility of gene flow from early European farmers. Nonetheless, the time of origin now seems earlier for the palette of European eye colors and probably for the palette of European hair colors. How much earlier? Probably within the same time frame when European skin turned white: somewhere between 11,000 and 19,000 years ago according to Beleza et al. (2013) or between 7,600 and 19,200 years according to Canfield et al. (2014). Although different genes are responsible for eye, hair, and skin color, there was probably a single selection pressure that seems to have acted primarily on early European women (Frost, 2006; Frost, 2008).

Interestingly, although the Luxembourg man was blue-eyed, he also had brown skin. He lacked the ‘European’ alleles at all three genes involved in the whitening of European skin. Such a genotype is extremely rare today in unadmixed Europeans (Khan, 2014). Equally odd is the fact that this brown-skinned European lived long after (Beleza et al., 2013) or probably after (Canfield et al., 2014) the time period when European skin turned white. How could that be? Well, these estimates apply only to the ancestors of living Europeans. This individual may not have been so lucky.

When the last ice age ended some 10,000 years ago, it may be that only some European populations had acquired a fully ‘European’ phenotype, i.e., white skin, multi-hued eyes and hair, a more childlike face, and longer, straighter hair. This phenotype would have been most predominant on the former steppe-tundra of northern and eastern Europe. Moving outward from this region, one would have seen humans with more and more of the evolutionarily older traits, i.e., brown skin, uniformly brown eyes and black hair, a more robust face, and short, frizzy hair.

This older phenotype might have persisted well into the Holocene in peripheral and isolated parts of Europe.  As Fleure (1945) notes:

In a few places in Sweden, Britain, and France, people have been noticed who show characteristics of the skull and face that remind one of late-Paleolithic man: these people are usually darker, in hair and eyes, than their neighbors; sometimes they even have swarthy skins.

Even in Scandinavia, we find references in folklore and mythology to an ancient dark-skinned population. A Norse poem, the Rigsthula, describes how the god Rig created a class of thralls who were black-haired, swarthy, and flat-nosed (Jonassen, 1951). This theme comes up elsewhere in Old Norse literature (Karras, 1988).

This leads us to the debate over the discovery of so-called ‘Negroid’ skeletal remains in Europe. Clearly, these individuals were not African, but nor were they like present-day Europeans. They seem to represent an older phenotype that had already lost predominance by Holocene times. The skeletal evidence is reviewed by Boule and Vallois (1957, pp. pp. 291-292):

‘In Brittany, as well as in Switzerland and in the north of Italy, there lived in the Polished Stone period, in the Bronze Age and during the early Iron Age, a certain number of individuals who differed in certain characters from their contemporaries’, in particular in the dolichocephalic character of their skull, in possessing a prognathism that was sometimes extreme, and a large grooved nose. This is a matter of partial atavism which in certain cases, as in the Neolithic Breton skull from Conguel, may attain to complete atavism. Two Neolithic individuals from Chamblandes in Switzerland are Negroid not only as regards their skulls but also in the proportions of their limbs. Several Ligurian and Lombard tombs of the Metal Ages have also yielded evidences of a Negroid element.

Since the publication of Verneau’s memoir, discoveries of other Negroid skeletons in Neolithic levels in Illyria and the Balkans have been announced. The prehistoric statues, dating from the Copper Age, from Sultan Selo in Bulgaria are also thought to portray Negroids. In 1928 René Bailly found in one of the caverns of Moniat, near Dinant in Belgium, a human skeleton of whose age it is difficult to be certain, but which seems definitely prehistoric. It is remarkable for its Negroid characters, which give it a resemblance to the skeletons from both Grimaldi and Asselar.

It is not only in prehistoric times that the Grimaldi race seems to have made its influence felt. Verneau has been able to see, now in modern skulls and now in living subjects, in the Italian areas of Piedmont, Lombardy, Emilia, Tuscany, and the Rhone Valley, numerous characters of the old fossil race.

This older phenotype must have gradually disappeared as the newer phenotype spread outwards from the plains of northern and eastern Europe. Why did one replace the other? What sort of selective advantage did the newer phenotype confer? The reason probably had less to do with physical appearance and more to do with the mental toolkit that humans had developed on the steppe-tundra of the last ice age. These northern hunting peoples were pre-adapted to technological complexity and thus better able to exploit the opportunities of later cultural environments (Frost, 2010). Some of them, specifically the semi-sedentary hunter-fisher-gatherers around the North Sea and the Baltic, would become pre-adapted not only to technological complexity but also to social and economic complexity (Frost, 2013).

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

Boule, M. and H.V. Vallois. (1957). Fossil Men. New York: Dryden Press. 

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 

Dienekes (2013).  Mesolithic Iberians (La Braña-Arintero) not ancestors of modern ones,

Dienekes’ Anthropology Blog
http://dienekes.blogspot.ca/2013/12/europeans-neolithic-farmers-mesolithic.html

Fleure, H.J. (1945). The distribution of types of skin color, Geographical Review, 35, 580-595. 

Frost, P. (2013). Origins of Northwest European guilt culture. Part II, Evo and Proud, December 14

http://evoandproud.blogspot.ca/2013/12/origins-of-northwest-european-guilt.html

Frost, P. (2010). Out of North Eurasia, Evo and Proud, May 27

http://evoandproud.blogspot.ca/2010/05/out-of-north-eurasia.html 

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.

Jonassen, C.T. (1951). Some historical and theoretical bases of racism in northwestern Europe, Social Forces, 30, 155-161.

Karras, R.M. (1988). Slavery and Society in Medieval Scandinavia. New Haven. 

Khan, R. (2014). Phenotypic Whiteness as an Outcome of Neolithic Admixture, The Unz Review: An Alternative Media Selection, January 3.

http://www.unz.com/gnxp/phenotypic-whiteness-as-an-outcome-of-neolithic-admixture/ 

Lazaridis, I., Patterson, N., Mittnik, A., Renaud, G., Mallick, S., et al. (2013). Ancient human genomes suggest three ancestral populations for present-day Europeans, BioRxiv, December 23.

http://biorxiv.org/content/early/2013/12/23/001552.full-text.pdf+html 

He who pays the piper ...

You want to publish a book about HBD? You’ll have to find a wealthy patron.

Debate is continuing over Ron Unz’s article on Race, IQ, and Wealth. In a favorable review at Living Anthropologically, the following comment caught my eye:

Unz has money, and he uses it to publish and promote. Unz apparently gave out at least $500,000 to Gregory Cochran, co-author with Harpending on The 10,000 Year Explosion: How Civilization Accelerated Human Evolution and with John Hawks on Recent acceleration of human adaptive evolution.

Raised eyebrows ... And those people aren’t the only ones. Ron’s 2009 tax return mentions donations to Steve Sailer and Razib Khan, among others (Unz, 2009).

Once upon a time academics got grants or sabbaticals for book writing. But that option is becoming less and less feasible if you want to write about human biodiversity. Getting your manuscript published is even more problematic. In the past, you could submit it to a publishing house and they would have it assessed by an expert in the field. Today, that system is almost extinct, at least in North America. You must go through a ‘literary agent’ who will pitch your manuscript at wine and cheese parties. It’s a system that is highly prone to abuse: schmoozing, petty bribery, and sleeping with the right people.

There are only two other options: publish on a shoestring budget or find a wealthy patron. Like Ron Unz. But what do you do when your patron starts promoting ideas you feel are wrong? Do you say nothing? Or do you bite the hand that feeds you?

The act of giving money is not wholly altruistic. Implicitly, it can become a form of control. The receiver thinks twice before doing anything that might offend the giver. And the giver may drop hints …

Other happenings

- Emily Sohn has recently interviewed me for an article in Discovery News. See here.

- A journal article will soon come out on the relationships between blue eye color and feminization of facial structure. This finding is consistent with other evidence of sex linkage for non-brown eyes and non-black hair. Indeed, a twin study has shown that hair is, on average, lighter-colored in women than in men, with red hair being especially more frequent in females. Women also show greater variation in hair color (Shekar et al., 2008). All of this, in turn, is consistent with a selection pressure, possibly sexual selection, that has acted more strongly on European women than on European men to diversify the palette of human hair colors.

References

Anon. (2012). Race IQ – Game Over: It was always all about wealth, August 9, Living Anthropologically http://www.livinganthropologically.com/2012/08/09/race-iq-game-over/

Shekar, S.N., D.L. Duffy, T. Frudakis, G.W. Montgomery, M.R. James, R.A. Sturm, & N.G. Martin. (2008). Spectrophotometric methods for quantifying pigmentation in human hair—Influence of MC1R genotype and environment. Photochemistry and Photobiology, 84, 719–726.

Sohn, E. (2012). Why do so many women go blonde? August 14, Discovery News http://news.discovery.com/human/miley-cyrus-blonde-hair-120814.html

Unz, R. (2012). Race, IQ, and Wealth, The American Conservative, July 18. http://www.theamericanconservative.com/articles/race-iq-and-wealth/

Unz, R. (2009). Return of Private Foundation (IRS) http://irs990.charityblossom.org/990PF/200912/207181582.pdf

The puzzle of Neanderthal admixture

Skhul V – one of the Skhul-Qafzeh hominins. Were they the middleman between Neanderthal genes and the modern human genome?

When I initially published my last post, I pooh-poohed the rumors about the reconstructed Neanderthal genome. How could modern humans have Neanderthal DNA when no such admixture appeared in previous analyses of mtDNA, dentition, and noncoding DNA? Any Neanderthal admixture would have to be less than 1%.

I then logged on to Razib Khan’s site. The news had just broken: modern humans outside Africa are 1 to 4% Neanderthal. I hurriedly rewrote my post and spent the rest of the day eating crow.

In retrospect, I now realize I had put too much faith in the existing data. I had also ignored the warning signs. The HBD community correctly decoded the silence that had fallen over Pääbo’s research team, as well as a remark made by Linda Vigilant.

Despite the crow-phagia, this is good news. It means the end to a long and bitter conflict between proponents of two models of human origins: ‘Out of Africa’ versus multiregionalism. Anthropologists may still disagree, but the room for disagreement has greatly shrunk from what it was only a week ago. We can now move on.

The winning model is a weak version of Out of Africa. Modern humans are largely descended from a series of population expansions that began around 80,000 years ago somewhere in eastern Africa and culminated c. 60,000 BP in a ‘big bang’ that would create 96-99% of the gene pool outside Africa. The remaining 1-4% came from archaic Europeans and Asians, i.e., Neanderthals in Europe and West Asia, and other hominins elsewhere (Almas in Siberia? Hobbits in southeast Asia?). This admixture seems to have occurred in two stages: an early one in the Middle East, when modern humans began spreading out of Africa, and a later one, when modern humans began to spread from Asia to Oceania (Dalton, 2010). Curiously, the admixture looks Neanderthal in both cases.

Did this admixture contribute anything useful? We still don’t know. Some academics had identified the new variant of the microcephalin gene as being probably of Neanderthal origin, but this variant is absent from the reconstructed Neanderthal genome. To date, Pääbo’s team is of the opinion that “the Neanderthal DNA does not seem to have played a great role in human evolution” (Wade, 2010).

Surprisingly, the same level of Neanderthal admixture was found in a French subject, a Chinese subject, and a Papuan subject. This seems to suggest that Neanderthal admixture happened when modern humans began spreading out of Africa, probably in southwest Asia. But why was there no further admixture in Europe, where the two populations co-existed much longer? If there had been, we would see more Neanderthal admixture in present-day Europeans, but we don’t.

There are several possible explanations:

1. Noise in the data obscures the higher level of Neanderthal admixture in present-day Europeans. The picture should become clearer once we have sequenced 100% of the Neanderthal genome, and not the current 60% (Richard Green in an interview on CBC).

2. Early modern Europeans were replaced by Middle Eastern immigrants when farming replaced hunting and gathering (Green et al., 2010).

3. In Europe, early modern humans greatly outnumbered the Neanderthals. Subsequent admixture thus had little effect (Green et al., 2010).

4. In East Asia and Oceania, ‘Neanderthal admixture’ is actually a proxy for something else. These regions had non-Neanderthal archaic populations that were probably more closely related to the Neanderthals than to modern humans. If so, ‘Neanderthal admixture’ in these regions may correspond, more or less, to admixture with other archaic humans (my idea).

5. Neanderthal genes entered modern Eurasian populations indirectly, via an intermediate Middle Eastern population that already had Neanderthal admixture (because of prolonged contact) while being fairly close to modern humans in appearance and behavior. Modern humans may thus have more readily intermixed with them but not with Neanderthals in Europe. The latter were so different in appearance and behavior that admixture would have been minimal (my idea).

I’m inclined toward the last two explanations. Explanation #4 would explain why the later admixture in Asia/Oceania seems to have been as ‘Neanderthal’ as the early admixture in the Middle East. Unfortunately, to test this explanation, we must first reconstruct the genome of archaic humans from the Asia/Oceania transition zone. This will be difficult, if not impossible, given the accelerated degradation of DNA in the tropics.

Explanation #5 is also tempting. Not long before modern humans began spreading out of Africa, the Middle East was home to a population with both modern human and Neanderthal characteristics, as attested by remains from Skhul and Qafzeh in northern Israel. These hominins first appeared in the Levant some 120,000 years ago, perhaps as part of an earlier out-of-Africa expansion into south Asia. Their technology was Mousterian and Neanderthal-like, but their anatomy was relatively modern with some archaic features (Kidder et al., 1992; Pearson, 1998). These “almost-moderns” existed on the periphery of a range centered on the African continent. Only a bit farther north were the Neanderthals of Europe and West Asia.

When the climate cooled during the Early Pleniglacial (70,000-55,000 BP), the southern limit of the Neanderthal range shifted accordingly. Neanderthals then occupied the Levant until the arrival of modern humans some 50,000 years ago (Grun & Stringer, 1991; Schwarcz et al., 1989; Valladas et al., 1987).

What happened to the Skhul-Qafzeh hominins? They probably moved farther south, perhaps to the Hejaz. Such a location would have been athwart the main line of expansion of modern humans as they spread out of Africa. Unfortunately, despite many interesting sites, there has been no dating so far of early human occupation in Saudi Arabia (Petraglia & Alsharekh, 2003).

References

Dalton, R. (2010). Neanderthals may have interbred with humans. Genetic data points to ancient liaisons between species. Naturenews, April 20.
http://www.nature.com/news/2010/100420/full/news.2010.194.html

Green, R.E., J. Krause, A.W. Briggs, T. Maricic, U. Stenzel, M. Kircher, et al. (2010). A draft sequence of the Neandertal genome, Science, 328, 710-722.
http://www.sciencemag.org/cgi/reprint/328/5979/710.pdf

Grun, R., and C.B. Stringer. (1991). Electron spin resonance dating and the evolution of modern humans, Archaeometry, 33, 153-199.

Kidder, J.H., R.L. Jantz, and F.H. Smith. (1992). Defining modern humans: A multivariate approach, in G. Bräuer and F.H. Smith (eds.) Continuity or Replacement. Controversies in Homo Sapiens Evolution, pp. 157-177, Rotterdam: A.A. Balkema.

Pearson, O.M. (1998). Postcranial Morphology and the Origin of Modern Humans, Ph.D. dissertation, State University of New York at Stony Brook, Ann Arbor: University Microfilms International.

Petraglia, M.D. and A. Alsharekh. (2003). The middle palaeolithic of Arabia: implications for modern human origins, behaviour and dispersals, Antiquity Journal, 77, 671–684.
http://repository.ksu.edu.sa/jspui/handle/123456789/5520

Schwarcz, H.P., B. Blackwell, P. Goldberg, and A.E. Marks. (1979). Uranium series dating of travertine from archaeological sites, Nahal Zin, Israel, Nature, 277, 558-560.

Valladas, H., J.L. Joron, G. Valladas, B. Arensburg, O. Bar-Yosef, A. Belfer-Cohen, P. Goldberg, H. Laville, L. Meignen, Y. Rak, E. Tchernov, A.M. Tillier, and B. Vandermeersch. (1987). Thermoluminescence dates for the Neanderthal burial site at Kebara in Israel, Nature, 330, 159-160.

Wade, N. (2010). Signs of Neanderthals mating with humans, New York Times, May 7, 2010.http://www.nytimes.com/2010/05/07/science/07neanderthal.html (read)