Saturday, October 27, 2012

A detour through Europe?

The lithic technology of southwestern France (c. 22,000-17,000 BP) strangely resembles that of the first paleo-Amerindians (c. 12,000). Some people speculate that early Europeans reached North America by crossing the Atlantic. The truth is even more incredible. Early Europeans spread eastward and became the ancestors not only of the Amerindians but also of East Asians. (source)

The recent study by Beleza et al. (2012) has elicited comment on two findings:
  1. European skin turned white long after modern humans had entered Europe (c. 40,000 BP). Moreover, it whitened relatively fast—between 19,000 and 11,000 years ago. Such a narrow timeframe implies some form of selection, and not just relaxation of selection for darker skin. 

  1. The new skin-color alleles did not come from the Neanderthals. This point may have broader repercussions because some have argued that the rapidity of evolution among modern humans required “cherry picking” of useful alleles from Neanderthals and other archaic hominins.

But another finding deserves comment. This is the discovery that an earlier (though minor) lightening of skin color had occurred shortly after the entry of modern humans into Europe:

[…] the initial stages of European skin lightening occurred in a proto-Eurasian population, about 30,000 years ago, after the out-of-Africa migration ~60,000-70,000 years ago […] and slightly more recently than the earliest archaeological evidences for the dispersal of anatomically modern humans in Europe, around 40,000 years ago (Beleza et al., 2012).

It’s widely accepted that the ancestors of Europeans and East Asians parted company long after modern humans had begun spreading out of Africa. It’s usually assumed, however, that this splitting took place somewhere in the Middle East or Central Asia. If we are to believe Beleza et al (2012), it must have happened after the entry of modern humans into Europe.

So the first Europeans were also the first East Asians. Cro-Magnon Man wasn’t just a proto-European. He was also a proto-Eurasian.

From Africa to East Asia … by way of Europe?

A straight line isn’t always the easiest route from point A to point B. In any case, modern humans weren’t going anywhere in particular when they began spreading out of Africa. They were seeking new lands and following the path of least resistance.

Let’s suppose you’re a band of hunter-gatherers in the Levant circa 50,000 BP. What new territories would tempt you? The Iranian Plateau and, beyond it, the arid steppes of Central Asia? No, that doesn’t seem very tempting.

You would look to lands farther north and west along the Mediterranean. Those lands are similar in climate, vegetation, and wildlife. You can continue using the same life skills, since the means of subsistence are almost the same.

As your descendants grow in numbers and spread farther out, they will eventually bump up against an ecological zone that differs in climate, vegetation, and wildlife. At that point, they’ll have to stop their advance and begin a slow process of adaptation within transitional environments on the edge of this zone. Once they’ve sufficiently adapted, they will break out from this “beachhead.” And begin a new wave of advance.

This is what happened when modern humans spread north from the Mediterranean and into more boreal environments with wider seasonal variations. Finally, they encountered the Eurasian steppe-tundra—a vast open plain of grassland stretching from southwestern France to Manchuria. Living in that environment would require a whole suite of new adaptations. The men would have to become much more mobile in order to hunt the herds of wandering herbivores. The women would have to abandon food gathering and take on new tasks like shelter building and garment making. So where do you think those adaptations were developed?

In southwestern France. This “beachhead” was the most southerly and resource-rich portion of the Eurasian steppe-tundra (Mellars, 1985). Sheltered valleys dissected the steppe and offered trees and other non-arctic vegetation, particularly on south-facing slopes (Blades, 1999b). In this protected environment, hunter-gatherers could live off salmon, local game, wild fruits, grains, and tubers while hunting reindeer herds that passed through in the fall and winter (Blades, 1999a; Blades, 1999b; Mellars, 1985). As the climate improved from 30,000 to 27,000 BP, closed forests became established, the herds moved further afield, and reindeer hunting was all but abandoned at valley sites (Blades, 1999b). The men had to move out of the valleys and onto the surrounding tundra tablelands. They now had to make further adaptations: more efficient use of raw materials (wood for fire and shelter, lithic materials); long-distance travel to procure them; and development of extensive social networks (Goebel, 1999; Hahn, 1987).

Sometime after 28,000 BP, they broke out from the beachhead and colonized the tundra plains in their entirety. This breakout may correspond to a demographic expansion (23,000-21,000 BP) of a genetic lineage that occurs most often among the Basques of northern Spain and southwestern France (Richards et al., 1996; Richards et al., 2000). Relatively few people were involved, as indicated by the very low variability of the northern European gene pool (Reich et al., 2001). Presumably, there were many semi-isolated groups, each one tinkering with its own mix of cultural adaptations until one of them got it right and colonized the Eurasian steppe-tundra.

After the breakout, nothing could stop them from spreading east throughout the Eurasian steppe-tundra … all the way to the Pacific Ocean, and from there to Beringia and North America. They would in time become the ancestors of most people living today, not only Europeans but also East Asians and Amerindians.

For this, we have several lines of evidence:

- a Y-chromosome study has found that all North Eurasian peoples descend from a common ancestral population dated to about 15,000 BP (Stepanov & Puzyrev, 2000; see also Armour et al., 1996; Santos et al., 1999; Zerjal et al., 1997).

- the language families of northern Eurasia, particularly Uralic and Yukaghir and more generally Uralic-Yukaghir, Eskimo-Aleut, Chukotko-Kamchatkan and Altaic, share deep structural affinities that point to a common origin and not simply to word borrowing (Cavalli-Sforza, 1994, pp. 97-99; Fortescue, 1998; Rogers, 1986).

- archeological evidence (characteristic lithic technology, grave goods with red ocher, and sites with small shallow basins) also suggests a common cultural tradition throughout Europe and Siberia 20,000 to 15,000 years ago (Goebel, 1999; Haynes, 1980; Haynes, 1982).

- dental and cranial remains from Mal’ta (23,000-20,000 BP) in southern Siberia indicate strong affinities with Upper Paleolithic Europeans (Alexeyev & Gokhman, 1994; Goebel, 1999).

Finally, the lithic technology of southwestern France (c. 22,000-17,000 BP), referred to as “Solutrean”, strangely resembles that of the first paleo-Amerindians (c. 15,000-12,000). Solutrean and Clovis points share common characteristics. Both are thin and bifacial, and both share the intentional use of the outre passé, or overshot flaking technique, which quickly reduces the thickness of a biface without reducing the width.

This similarity has led to the “Solutrean hypothesis”— the idea that early Europeans reached North America by crossing the Atlantic. Again, the easiest route between two points isn’t always a straight line. For the proto-Eurasians of southwestern France, the road to North America ran east ... over the unbroken grasslands of the Eurasian steppe-tundra.


Alexeyev, V.P., & Gokhman, I.I. (1994). Skeletal remains of infants from a burial on the Mal'ta Upper Paleolithic site. Homo, 45, 119‑126.

Armour, J.A.L., Anttinen, T., May, C.A., Vega, E.E., Sajantila, A., Kidd, J.R., Kidd, K.K., Bertranpetit, J., Paabo, S., & Jeffreys, A.J. (1996). Minisatellite diversity supports a recent African origin for modern humans. Nature Genetics, 13, 154‑160.

Beleza, S., A. Múrias dos Santos, B. McEvoy, I. Alves, C. Martinho, E. Cameron, M.D. Shriver, E.J. Parra, & J. Rocha. (2012). The timing of pigmentation lightening in Europeans, Molecular Biology and Evolution, 20, online

Blades, B.S. (1999a). Aurignacian settlement patterns in the Vézère valley, Current Anthopology, 40, 712-719.

Blades, B.S. (1999b). Aurignacian lithic economy and early modern human mobility: new perspectives from classic sites in the Vézère valley of France, Journal of Human Evolution, 37, 91-120.

Cavalli-Sforza, L.L., Menozzi, P. & Piazza, A. (1994). The History and Geography of Human Genes. Princeton: Princeton University Press.

Fortescue, M.D. (1998). Language Relations across Bering Strait. Reappraising the Archaeological and Linguistic Evidence. Cassell: London.

Goebel, T. (1999). Pleistocene human colonization of Siberia and peopling of the Americas: An ecological approach. Evolutionary Anthropology, 8, 208‑227.

Hahn, J. (1987). Aurignacian and Gravettian settlement patterns in Central Europe. In The Pleistocene Old World, O. Soffer (Ed.). New York: Plenum Press, pp. 251‑261.

Haynes, C.V. (1982).Were Clovis progenitors in Beringia? In Paleoecology of Beringia, D.M. Hopkins (Ed.). New York: Academic Press, pp. 383‑398.

Haynes, C.V. (1980). The Clovis culture. Canadian Journal of Anthropology, 1, 115‑121.

Mellars, P.A. (1985). The ecological basis of social complexity in the Upper Paleolithic of Southwestern France. In Prehistoric Hunter‑Gatherers. The Emergence of Cultural Complexity, T.D. Price & J.A. Brown (Eds.). Orlando: Academic Press, pp. 271‑297.

Reich, D.E., M. Cargill, S. Bolk, J. Ireland, P.C. Sabeti, D.J. Richter, T. Lavery, R. Kouyoumjian, S.F. Farhadian, R. Ward, and E.S. Lander. (2001). Linkage disequilibrium in the human genome, Nature, 411, 1999-2001.

Richards, M., H. Côrte-Real, P. Forster, V. Macaulay, H. Wilkinson-Herbots, A. Demaine, S. Papiha, R. Hedges, H.-J. Bandelt, & B. Sykes. (1996). Paleolithic and Neolithic lineages in the European mitochondrial gene pool, American Journal of Human Genetics, 59, 185-203.

Richards, M., V. Macaulay, E. Hickey, E. Vega, B. Sykes, et al. (2000). Tracing European founder lineages in the Near Eastern mtDNA pool, American Journal of Human Genetics, 67, 1251-1276.

Rogers, R.A. (1986). Language, human subspeciation, and Ice Age barriers in Northern Siberia. Canadian Journal of Anthropology, 5, 11‑22.

Santos, F.R., Pandya, A., Tyler‑Smith, C., Pena, S.D.J., Schanfield, M., Leonard, W.R., Osipova, L., Crawford, M.H., & Mitchell, R.J. (1999). The Central Siberian origin for Native American Y chromosomes. American Journal of Human Genetics, 64, 619‑628.

Stepanov, V.A., & Puzyrev, V.P. (2000). Evolution of Y‑chromosome haplotypes in populations of North Eurasia. American Journal of Human Genetics, 67, 220.

Zerjal, T., Dashnyam, B., Pandya, A., Kayser, M., Roewer, L., Santos, F.R., Scheifenhövel, W., Fretwell, N., Jobling, M.A., Harihara, S., Shimizu, K., Semjidmaa, D., Sajantila, A., Salo, P., Crawford, M.H., Ginter, E.K., Evgrafov, O.V., & Tyler‑Smith, C. (1997). Genetic relationships of Asians and Northern Europeans, revealed by Y‑chromosomal DNA analysis. American Journal of Human Genetics, 60, 1174‑1183. 

Saturday, October 20, 2012

When Europeans turned white

No, that’s not a climatic adaptation
(actress Lily Cole - source)

“European skin turned pale only recently”—such was the headline in Science five years ago. 

[…] a new report on the evolution of a gene for skin color suggests that Europeans lightened up quite recently […]  the implication is that our European ancestors were brown-skinned for tens of thousands of years (Gibbons, 2007)

The report had been presented by a postdoc, Heather Norton, at the annual meeting of the American Association of Physical Anthropologists (Norton & Hammer, 2007). Over the following years, I e-mailed periodically to ask her when the study would be published. To make a long story short, she landed a faculty position and found herself overwhelmed by new responsibilities. There were still problems with the dating of this genetic change, and time couldn’t be found to work them out. So the study stayed “on the back burner.”

Five years later, the study has finally been published … by another research team. Beleza et al. (2012) generally confirmed Norton’s preliminary finding but found evidence that Europeans had lightened through a 2-stage process. Around 30,000 years ago, not long after entering Europe, the ancestors of today’s Europeans and East Asians lightened in skin color through a new allele at the KITLG gene. But the real whitening came much later, between 19,000 and 11,000 years ago among ancestral Europeans only, through new alleles at TYRP1, SLC24A5, and SLC45A2. This finding strikes down the two leading explanations for the whiteness of European skin:

1.     As modern humans spread north from Africa and into higher latitudes with less solar UV, their skin had to lose pigmentation to maintain the same level of vitamin-D synthesis. Europeans therefore began to turn white once their ancestors entered European latitudes some 40,000 years ago (Loomis, 1970; Murray, 1934).

This explanation might account for the initial loss of pigmentation circa 30,000 BP, when ancestral Europeans probably became as light-skinned as Amerindians. But it cannot explain the much greater loss of pigmentation more than twenty thousand years later.

2.     Some writers, like Sweet (2002), have suggested that the transition from hunting and gathering to farming increased the body’s need for vitamin D (because cereals contain phytic acids that immobilize calcium and phosphorus within the body and because a high-meat diet seems to reduce vitamin-D requirements). In Europe, however, this transition began only 8,000 years ago and did not reach northern Europe until 7,000-3,000 BP.

Beleza et al. (2012) suggest that a colder climate forced Ice Age Europeans to wear more clothing and spend more time in shelters, thus reducing their exposure to solar UV. It was thus at that time, and not when modern humans first entered Europe, that European skin turned white in order to maintain the same level of vitamin-D synthesis.

But then why didn’t Europeans revert after the Ice Age to their original brown color? And why do we see brown skin in humans who have long lived with weaker solar UV and even colder weather in northern Asia and North America? This is notably the case with Amerindian groups in Canada and Alaska who derive very little vitamin D from either the sun or their diet (Frost, 2012a, 2012b).

In any case, it is only during the summer that solar UV is intense enough for the skin to synthesize vitamin D. Yet European summers were not much cooler during the last ice age than they are today. The Central Russian Plain, for instance, had a July mean temperature of 16° back then, versus 18° now (Hoffecker, 2002, p. 23). So Ice Age Europeans had little reason to be less exposed to solar UV. Indeed, the open steppe-tundra was much more exposed to the sun than the forested environments before and after the Ice Age.

Sexual selection?

There remains of course my explanation (Frost, 2006; Frost, 2008). White skin was not climatically advantageous. It was visually advantageous, as were two other unique color traits. Within this same geographic area, centered on northern and eastern Europe, hair is not only black but also brown, flaxen, golden, or red. Eyes are not only brown but also blue, gray, hazel, or green.

Yet, in each case, the genes are different. European skin lightened mainly through replacement of alleles at three genes: SLC45A2, SLC24A5, and TYRP1. European hair color diversified through a proliferation of new alleles at the MC1R gene. European eye color diversified through a proliferation of new alleles in the HERC2-OCA2 region and elsewhere.

These European color traits have evolved along separate trajectories, yet the goal seems similar—a shift toward brighter and more visible colors. But visible to whom?

To the opposite sex? Sexual selection favors visual qualities that catch the attention of potential mates. In the case of skin color, a pre-existing sexual dimorphism has made lighter skin a visible female characteristic. Women are the “fair sex.” They’re paler than men from puberty onward (Edwards & Duntley, 1939).

Skin color is, in fact, a key visual cue for sex recognition, being even more crucial than face shape (Bruce & Langton, 1994; Hill, Bruce, & Akamatsu, 1995; Russell & Sinha, 2007; Russell et al., 2006; Tarr et al., 2001; Tarr, Rossion, & Doerschner, 2002). When shown a human face, subjects can recognize its sex even if the image is blurred and differs only in color (Tarr et al., 2001).

The specific cues are hue and luminosity. A man is browner and ruddier in hue than a woman because melanin and blood are more present in his skin’s outer tissues (Edwards & Duntley, 1939). A woman has higher luminous contrast between her facial skin and her lips or eyes (Dupuis-Roy et al., 2009; Russell, 2003). These cues may explain the similar evolution of cosmetics in a wide range of culture areas, i.e., women generally seek to lighten their facial color and to increase its contrast with their lip and eye color (Russell, 2003; Russell, 2009; Russell, 2010).

Thus, the more a woman is lighter-skinned, the more she is recognizably female. This is not just a matter of conscious sex recognition. It’s also a matter of men acting on half-conscious feelings. Even when a woman is recognized as such, her mating success may be influenced by subtle differences in the way men perceive her femininity.

Extreme sexual selection on the European steppe-tundra

But if sexual selection were the cause, why did it occur only 19,000 to 11,000 years ago and only in Europe? What was so special about that time and place?

That time frame coincides with the last ice age (25,000-10,000 BP), particularly the glacial maximum (20,000-15,000 BP). In Europe, especially on the northern and eastern plains, there were now vast expanses of steppe-tundra that supported herds of wandering reindeer and other herbivores, which in turn supported a large human population. Bioproductivity was in fact much higher there than on today’s arctic barrens. Steppe-tundra also existed in Asia, but it was colder and drier, being farther north and farther from the moderating influence of the Atlantic Ocean. Its human population was not only smaller but also more vulnerable to periodic extinctions, particularly at the height of the last ice age.

Europe’s steppe-tundra was a singularity among the many environments that modern humans encountered as they spread out from Africa during the Paleolithic. It offered an abundance of food, but almost all of the food was in the form of meat. Since hunting was primarily a male activity, men had to bear almost the entire burden of food provisioning. Women either processed the food that men supplied or did activities unrelated to food, such as garment making or shelter building.

There were also demographic consequences. First, polygyny became less common, being limited to those able hunters who could support more than one family. Second, the death rate among young males increased. In hunter-gatherer societies, the male death rate increases with hunting distance, reaching a maximum in environments where hunters pursue migratory herds over long distances. As a result, women greatly outnumbered men on the mate market. Women had to compete for the attention of potential mates, and sexual selection favored the mating success of those who could.

In other species, sexual selection changes physical appearance from a dull, cryptic coloration to a brighter, more eye-catching one. This is especially true for traits on or near the face—the focus of visual attention. Since most genes for human skin, hair, and eye color are not sex-linked, any selection for new color traits in one sex would spill over onto the other sex. As European women whitened, so did Europeans of both sexes.

In time, sexual selection also leads to sexual dimorphism. Sex-linked alleles would appear through random mutation and gradually replace similar alleles that are not sex-linked. Some sexual dimorphism is indeed evident in European color traits. A twin study has shown that hair is lighter-colored in women than in men, with red hair being especially more frequent, and that women show greater variation in hair color (Shekar et al., 2008). Skin color, however, is actually less dimorphic in light-skinned humans than in those of medium skin color, probably because of a “ceiling effect,” i.e., girls cannot become much lighter-skinned after puberty if the population is already close to the limit of maximum paleness (Frost, 2007).

White European skin evolved relatively fast during the last ice age, specifically from 19,000 to 11,000 years ago. This was also probably the same time frame for the evolution of European hair and eye colors. Anyway, that’s my bet.

These color traits—white skin and a diverse palette of hair and eye colors— are not adaptations to a cooler, less sunny climate. They are adaptations by early European women to intense mate competition, specifically a shortage of potential mates due to a low polygyny rate and a high death rate among young men.

This situation was created by the steppe-tundra that covered most of Europe as late as 10,000 years ago. Early Europeans were able to colonize this environment but only at the price of a severe imbalance between men and women on the mate market.


Beleza, S., A. Murias dos Santos, B. McEvoy, I. Alves, C. Martinho, E. Cameron, M.D. Shriver, E.J. Parra & J. Rocha.(2012).The timing of pigmentation lightening in Europeans, Molecular Biology and Evolution, 20, online

Bruce,V., & S. Langton. (1994). The use of pigmentation and shading information in recognising the sex and identities of faces, Perception, 23(7), 803–822.

Dupuis-Roy, N., I. Fortin, D. Fiset, & F. Gosselin. (2009). Uncovering gender discrimination cues in a realistic setting, Journal of Vision, 9(2), 10, 1–8., doi:10.1167/9.2.10.

Edwards, E.A. & S.Q. Duntley. (1939). The pigments and color of living human skin, American Journal of Anatomy, 65, 1-33.

Frost, P. (2012a). Vitamin D deficiency among northern Native Peoples: a real or apparent problem? International Journal of Circumpolar Health, 71, 18001 - DOI: 10.3402/IJCH.v71i0.

Frost, P. (2012b). Reply to W.B. Grant ‘Re: Vitamin D deficiency among northern Native Peoples’ International Journal of Circumpolar Health, 71, 18435 - DOI: 10.3402/ijch.v71i0.18435

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),169-191.

Frost, P. (2007). Comment on Human skin-color sexual dimorphism: A test of the sexual selection hypothesis, American Journal of Physical Anthropology,133, 779-781.

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

Gibbons, A. (2007). American Association Of Physical Anthropologists Meeting: European Skin Turned Pale Only Recently, Gene Suggests. Science 20 April 2007:Vol. 316. no. 5823, p. 364 DOI: 10.1126/science.316.5823.364a

Hill, H., V. Bruce, & S. Akamatsu. (1995). Perceiving the sex and race of faces: The role of shape and colour, Proceedings of the Royal Society B: Biological Sciences, 261, 367–373.

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

Loomis, W.F. (1970). Rickets. Scientific American, 223, 77-91.

Murray, F.G. (1934). Pigmentation, sunlight, and nutritional disease. American Anthropologist, 36, 438-445.

Norton, H.L. & M.F. Hammer (2007). Sequence variation in the pigmentation candidate gene SLC24A5 and evidence for independent evolution of light skin in European and East Asian populations, Program of the 77th Annual Meeting of the American Association of Physical Anthropologists, p. 179.

Russell, R. (2010). Why cosmetics work. In Adams, R., Ambady, N., Nakayama, K., & Shimojo, S. (eds.) The Science of Social Vision. New York: Oxford.

Russell, R. (2009). A sex difference in facial pigmentation and its exaggeration by cosmetics. Perception, 38, 1211-1219.

Russell, R. (2003). Sex, beauty, and the relative luminance of facial features, Perception, 32, 1093-1107.

Russell, R. & P. Sinha. (2007). Real-world face recognition: The importance of surface reflectance properties, Perception, 36, 1368-1374.

Russell, R., P. Sinha, I. Biederman, & M. Nederhouser. (2006). Is pigmentation important for face recognition? Evidence from contrast negation, Perception, 35, 749-759.

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.

Sweet, F.W. (2002). The paleo-etiology of human skin tone.

Tarr, M.J., D. Kersten, Y. Cheng, & B. Rossion. (2001). It’s Pat! Sexing faces using only red and green, Journal of Vision, 1(3), 337, 337a,, doi:10.1167/1.3.337.

Tarr, M.J., B. Rossion, & K. Doerschner. (2002). Men are from Mars, women are from Venus: Behavioral and neural correlates of face sexing using color, Journal of Vision, 2(7), 598, 598a,, doi:10.1167/2.7.598.

Saturday, October 13, 2012

Now what?

Recent research, such as by historical economist Gregory Clark, suggests that differences in mental and behavioral traits cannot always be ascribed to different reproductive strategies, as Philippe Rushton suggested. There probably will never be a unified theory of human biodiversity … other than the theory of evolution by natural selection.

Last March, I was asked to review a paper for a special issue of Personality and Individual Differences about J. Philippe Rushton. I had no idea that he was gravely ill and would die the same year. Nor did I know that this special issue would come out after his death, as a tribute to his life and work.

That special issue having now been published, and the comments being of a general nature, I am free to post them. A few explanatory notes have been added.


J. Philippe Rushton has long been a voice crying in the wilderness. As such, he has suffered insults, harassment, and even assaults. At one point, the Ontario Provincial Police investigated him (under orders from the Premier of Ontario). His crime? Writing articles for peer-reviewed journals. His life story shows just how little we value academic dissent.

I, for one, value dissenters like Rushton, and it is as a friendly critic that I write the following comments. Like him, I believe that human populations differ statistically in a wide variety of mental capacities and behavioral predispositions. Such differences are even expectable. Around 10,000 years ago, human genetic evolution actually speeded up over a hundred-fold, and this was not a time when humans were entering new physical environments. It was a time when they were entering new cultural environments. Humans were no longer adapting to new types of climate, landscape, and vegetation. They were now adapting to new types of technology, social structure, and codified behavior (Hawks et al., 2007).

Like Rushton, I believe that these mental and behavioral differences must be viewed from the broader perspective of evolutionary theory. I likewise relate them to other human differences, notably in reproductive strategy and mating system.

Unlike Rushton, however, I have no wish to fit all of these differences into a single unifying theory, other than the theory of evolution by natural selection. There is evidence, for instance, that over the past thousand years Ashkenazi Jews have diverged in mean intelligence from Sephardic Jews (Cochran, Hardy & Harpending, 2006). Can this evolutionary change be attributed to a change in reproductive strategy? Isn’t it simply a response to the cognitive demands that come with specializing in trade and crafts?

Such gene-culture co-evolution has probably occurred in other groups, such as the Parsees in India. The high mean intelligence of East Asian societies (China, Korea, Japan) also seems of recent historical origin and may be related to the widespread use of exams as a means of social advancement, especially the imperial civil-service exam. [NOTE: East Asian societies also seem to have undergone the same sort of internal population replacement that Gregory Clark described in his study of English society, see Unz, 1980].

Then there is Gregory Clark’s finding that the English upper and middle classes had been steadily out-breeding the English lower classes until the 19th century. This internal population replacement acted as a strong selection pressure for middle-class values of thrift, self-restraint, and future time orientation (Clark, 2007).  

Thus, humans show a great deal of mental and behavioral variation that does not easily fit into the model of r vs. K. It is even debatable whether this model explains any variation. In other species, the relationship between reproductive strategy and climate zone is actually the reverse of what Rushton postulates. Tropical animals are typically K and non-tropical animals typically r. This is because the latter go through ‘boom and bust’ population cycles, due to a harsher and more unstable climate, and need an ‘r’ reproductive strategy to recover from the frequent downturns:

Thus, in the temperate zones selection often favors high fecundity and rapid development, whereas in the tropics lower fecundity and slower development could act to increase competitive ability. By putting more energy into each offspring and producing fewer total offspring, overall individual fitness is increased. The small clutch sizes characteristic of many tropical birds are consistent with Dobzhansky's hypothesis. (Pianka, 1970)

Rushton is half-right on one point. The human species does seem to have undergone selection for increased intelligence beyond the tropical zone, particularly during the hunting and gathering stage. This is seen in the correlation between latitude and complexity of tools and weapons, as noted by Hoffecker (2002, p. 135) when comparing modern humans and Neanderthals:

Both in terms of the number of types and component parts of individual implements, the complexity of Neanderthal tools and weapons is significantly lower than that of hunter-gatherers in northern latitudes (and more typical of modern groups in temperate or equatorial regions) […] Technological complexity in colder environments seems to reflect the need for greater foraging efficiency in settings where many resources are available only for limited periods of time.

Arctic humans coped with fluctuating resources and a mobile lifestyle by planning ahead, as seen in their use of untended devices (traps and snares) and means of food storage. In addition, these cognitive demands fell on both sexes, unlike the situation in the tropical zone—where women provided for their families year-round with less male assistance (Kelly, 1995, pp. 268-269; Martin, 1974, pp. 16-18). With men providing most of the food, women could enter a new range of tasks: food processing (butchery and carcass transport); shelter building; garment making; leather working; transport of material goods; etc. (Waguespack, 2005). This cognitive revolution would pave the way for later, more impressive developments—what we now call ‘civilization.’

But where do r and K fit into all of this? Arctic hunter-gatherers are, if anything, more ‘r’ than tropical hunter-gatherers, like Pygmies and Khoisans. A high ‘K’ reproductive strategy now prevails throughout sub-Saharan Africa, but this is a relatively recent development due to the expansion of agricultural peoples over the past seven thousand years.

One could make similar criticisms of Rushton’s theorizing on dark coloration and aggression, which is an extension of his r vs. K theory of human differences. [NOTE: Rushton found a cross-species correlation between darkness of coloration and aggressiveness, see Templer & Rushton, 2011]. First, birds are not light- or dark-colored as a function of latitude. Plumage coloration serves largely as a visual signal and not as a UV shield. There are other factors that make it difficult to extrapolate in this respect from humans to non-humans. In humans, the relationship between a tropical environment and male aggressiveness results from a cascade of evolutionary events:

1. Year-round tropical agriculture enables women to provide for themselves and their children with little male assistance.

2. This female reproductive autonomy lowers the cost of polygyny for men. More men can afford to have second wives.

3. More polygyny means more male-male rivalry for access to women. There is thus selection for men with higher testosterone levels, a more robust body build, and greater ability to fight off male rivals.

It is hard to see how this cascade of events applies to other species. Chickens, for instance, have not discovered farming. Nor is their coloration a climatic adaptation.

I am not disputing here the existence of a cross-species correlation between darker coloration and male aggressiveness. But there is an alternate explanation. Whatever the species, individuals are usually born with little or no pigment. Lighter coloration thus becomes associated with vulnerability and a need for parental care and protection. In contradistinction to this sign stimulus, adult males tend to evolve a darker coloration, especially in a context of intense male-male rivalry. This tendency was noted by Guthrie (1970):

Light skin seems to be more paedomorphic, since individuals of all races tend to darken with age. Even in the gorilla, the most heavily pigmented of the hominoids, the young are born with very little pigment. […] Thus, a lighter colored individual may present a less threatening, more juvenile image.

This point is further discussed in Frost (2011). In our own species, there seems to be a strong cross-cultural trend to associate darker skin with men and lighter skin with infants and women.

No theory is born perfect. Imperfections are to be expected and are normally ironed out through debate and discussion. But Rushton has been denied a normal academic environment. Criticism has almost inevitably been of the hostile sort, even to the point of being spiteful, incoherent, and self-contradictory. In this, the marketplace of ideas has suffered as much as he has. And we are all worse off.


Clark G. (2007). A Farewell to Alms. A Brief Economic History of the World. Princeton and Oxford: Princeton University Press

Cochran. G. M. , J. Hardy & H. Harpending. (2006). The natural history of Ashkenazi intelligence. Journal of Biosocial Science, 38, 659-693.

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.

Guthrie, R.D. (1970). Evolution of human threat display organs, Evolutionary Biology 4, 257-302.

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

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

Kelly, R.L.(1955). The Foraging Spectrum. Diversity in Hunter-Gatherer Lifeways. Washington: Smithsonian Institution Press.

Martin, M.K. (1974). The Foraging Adaptation — Uniformity or Diversity? Addison‑Wesley Module in Anthropology 56.

Pianka, E.R. (1970). On r- and K-Selection, The American Naturalist, 104, 592-597.

Templer, D. I., & Rushton, J. P. (2011). IQ, skin color, crime, HIV/AIDS, and income in 50 U.S. states. Intelligence, 39(20), 437-442.

Unz, R. (1980). Preliminary notes on the possible sociobiological implications of the rural Chinese political economy, unpublished paper.

Waguespack, N.M. (2005). The organization of male and female labor in foraging societies: Implications for early Paleoindian archaeology. American Anthropologist, 107, 666-676.

Saturday, October 6, 2012

J. Philippe Rushton (1943-2012) R.I.P.

J. Philippe Rushton. February 8, 1989 (source)

I first heard about J. Philippe Rushton in the mid-1980s. My mother would leave newspaper clippings about him on my desk, thinking I might be interested.  I didn’t know what to think. Wasn’t she a Christian fundamentalist? And why would I be interested?

A few years later, in October 1988, I actually got to meet him. This was at the founding conference in Ann Arbor,Michigan, of what would become the Human Behavior and Evolution Society (HBES).I remember talking to him briefly—something about career opportunities in psychology. I also attended his talk on “r/K reproductive strategies and the evolution of health, longevity and personality.” He was the only one there who broached the topic of psychological differences within the human species. Everybody else, including myself, held to the line that there was only one human nature and that it had assumed its present form back in the Pleistocene on the African savannah.

The following January, Rushton delivered an expanded paper on the same theme at the annual AAAS meeting in San Francisco. That paper was widely reported in the press. And the shit hit the fan. The premier of Ontario, David Peterson, called on the University of Western Ontario to fire him. When the university refused, the Attorney General ordered the Ontario Provincial Police to investigate Rushton. I couldn't believe this sort of thing was happening in my country and in "the free world." But I said nothing, not even to close friends. I was a typical Canadian, I guess.

After several months, the investigation was dropped … because no crime had been committed. He had weathered the storm, and survived. He and a few others who had stood by him.

His defiance may have inspired other academics to come out of the closet. By the mid-1990s, a sort of “Prague Spring” was under way. I remember attending a talk by Vincent Sarich about “the reality of human differences.” This was at the 1996 HBES meeting in Chicago, and his talk was the high point of the meeting. This was also the time when The Bell Curve came out, and when Internet discussion groups made their debut. It now became possible to discuss this topic on a level playing field, without threats or intimidation.  And time and again the “no difference” side got creamed.

Maybe they weren’t used to level playing fields. It was nonetheless flabbergasting to see prominent antiracist scholars, like C. Loring Brace, being reduced to silence when confronted with contrary evidence.

The Prague Spring didn’t last long. There would never be a second edition of The Bell Curve, although it sold very well. Another book on the same topic was spiked by its publisher at the last minute. For that matter, no mainstream publishing house would ever again allow anything on that topic.

It’s now a decade and a half later. With Rushton’s death, the next spring seems far away.