An idea abandoned by its father

Italian wall lizard (Podarcis sicula) (Credit: Charles J. Sharp). Five mating pairs were taken from one island to another, and over the next thirty generations the transplanted population became remarkably different from the parent population.

Unlike other animals, we adapt not only to natural environments but also to cultural environments of our making. We thus direct our own evolution. At the same time we are busy redesigning our cultural environment, the latter is just as busy redesigning us. Like the natural environment, it favors the survival and reproduction of those who best fit in.

This concept of gene-culture coevolution began with anthropologist Claude Lévi-Strauss in a 1971 lecture:

... Among early humans, biological evolution may have selected for pre-cultural traits like upright posture, manual dexterity, sociability, symbolic thinking, and ability to vocalize and communicate. It was culture, however, once it came into being, that consolidated these traits and propagated them. When cultures specialize, they consolidate and favor other traits, like resistance to cold or heat in societies that have willingly or unwillingly had to adapt to extreme climates, like dispositions to aggressiveness or contemplation, like technical ingenuity, and so on. In the form these traits appear to us on the cultural level, none can be clearly linked to a genetic basis, but we cannot exclude that they are sometimes linked partially and distantly via intermediate linkages. In this case, it would be true to say that each culture selects for genetic aptitudes, which then, via a feedback loop, influence the culture that had initially helped to strengthen them.

Credit is usually given, however, to geneticist Luigi Luca Cavalli-Sforza. In 1976, he developed the first mathematical models for gene-culture coevolution with another geneticist, Marcus Feldman, and in 1978-1979 he spoke on this subject to a cultural evolution class at Stanford (Feldman & Cavalli-Sforza 1976; Stone & Lurquin 2005, p. 108). Two of his students were Robert Boyd and Peter Richerson, who later wrote a seminal book on gene-culture coevolution (Boyd & Richerson 1985). In the mid-1980s, he decided to test this concept in the field by investigating the cultural and genetic bases of artistic talent among the Inuit:

One of the most remarkable phenomena in the contemporary Canadian Arctic is the presence of highly-acclaimed art forms — carving in stone and ivory, and printing on paper. The question we ask is: how can we account for the wide-spread distribution of such talent in a small dispersed population? (Berry & Cavalli-Sforza 1986, p. 2)

To answer this question, he organized a joint project with psychologist John W. Berry at Queen's University and anthropologist Bernard Saladin d'Anglure at Université Laval. The Inuit were chosen for study because their high rate of adoption made it possible "to distinguish cultural from biological inheritance by studying correlations of adopted children with foster relatives on one hand and biological relatives on the other" (Berry & Cavalli-Sforza 1986, p. 5). Also, until recently, Inuit had lived off the land and, as such, had "abilities [that] are considered to be adaptive to a nomadic and hunting life style" (Berry & Cavalli-Sforza 1986, p. 3). Berry argued that the artistic talent of the Inuit came from certain mental skills that helped them during hunting.

Hunters, by this way of thinking, require good visual acuity, keen disembedding skills and a well-developed sense of spatial orientation. To hunt successfully, the hunter must be able to discern the object of the quest (which is often embedded in a complex visual landscape), then disembed the object, and finally return to home base. In contrast, agriculturalists need not develop these particular skills, but rather they need to invest in other areas of development, such as conservation (in both the economic and the Piagetian senses) and close social interactions. (Berry 2008, p. 3)

The project fell through. Cavalli-Sforza said he had to quit because of illness. Neither of his biographies, however, mention any illness during that time period (Frost 2014). Interestingly, his American biography ascribes his interest in culture at that time to a desire to disprove the existence of mental differences between human populations:

Yet another source of his interest in culture was the idea that the concept of human cultural learning was a valid weapon against racist arguments that differences between people (for example, different IQ scores among ethnic groups) were due to biologically determined "racial" differences. (Stone & Lurquin, 2005, p. 86)

The reality was a bit different. He believed in the importance of culture, but not as an entity separate and distinct from biology. This put him in opposition not only to the racists he denounced in the 1960s but also to the antiracists who increasingly viewed him with suspicion from the late 1980s onward.

With Cavalli-Sforza out of the picture, research on gene-culture coevolution languished over the next quarter-century. This field of research needed a high-profile champion in academia, and all of the possible candidates were either unable or unwilling.  Cavalli-Sforza never was suited for the job, being too timid and, frankly, too easy to blackmail. (Do you really think his wartime research on anthrax involved only mice?)

Lately, there seems to have been a renewal of interest, as seen in this review article on "Human biological and psychological diversity":

Humans migrated out of Africa at least 50,000 years ago and occupied many different ecological and climatological niches. Because of this, they evolved slightly different anatomical and physiological traits. For example, Tibetans evolved various traits that help them cope with the rigors of altitude; similarly, the Inuit evolved various traits that help them cope with the challenges of a very cold environment. It is likely that humans also evolved slightly different psychological traits as a response to different selection pressures in different environments and niches. One possible example is the high intelligence of the Ashkenazi Jewish people. Frank discussions of such differences among human groups have provoked strong ethical concerns in the past. We understand those ethical concerns and believe that it is important to address them. However, we also believe that the benefits of discussing possible human population differences outweigh the costs. (Winegard et al. 2017)

This article is a good read, and I was intrigued by its examples of fast evolution, particularly the Italian wall lizards. Five mating pairs were taken from one island to another, and over the next thirty generations the transplanted population became remarkably different from the parent population. The lizards were now larger, had shorter hind limbs, and could bite with much more force. Even more remarkably, they had a new morphological trait: a cecal valve—a muscle between the large and small intestines that slows down food movement and allows digestion of cellulose. This is an adaptation to the abundance of plant food on that island, but it is surprising that an entirely new trait could evolve so fast.

As far back as Darwin, biologists have described evolutionary change as slow. This is true only when organisms live in slowly changing environments. Transplant them into a very different one, and they will evolve very fast. This has been especially true for modern humans, who over the past 50,000 years have spread into a wide range of natural environments from the tropics to the arctic and into an even wider range of cultural environments:

Humans, like many animals, actively alter their environment, which changes the selection pressures they face (Laland et al. 2001; Laland and Sterelny 2006). In fact, humans may be the paradigmatic example of a niche-creating species, using brains rather than brawn to conquer the world (Baumeister 2005; Pinker 2010). Across the globe, humans devised distinctive cultural systems to cope with their environments, creating vastly different selective regimes from one culture to another. (Winegard et al. 2017)

Humans are indeed niche creators who have speeded up their own diversification. Nonetheless, they aren't alone in diversifying so fast. For example, some animal and plant species have spread into a wide range of new habitats since the last ice age, thereby giving rise to many new populations. Whether these recent populations are "sibling species," "subspecies," or "races"—the distinction is often arbitrary—their example can help us understand our own genetic diversity (Frost 2011).

These populations, like our own, seem to have evolved much more anatomically than they have genetically. Their anatomies are often distinct from each other, with no overlap, yet their genomes overlap considerably—there is far more genetic variation within each population than between them. So they are easier to tell apart by their appearance than by their genes. 

Why this discordance between genes and anatomy? Genes don't lie, do they? To make sense of this puzzle, we need to understand three points:

• When a gene has different "alleles" or versions of itself, these alleles vary in their degree of similarity, some performing very differently and others identically or almost so—often because the gene itself is little more than "junk DNA.
• Population boundaries separate not only different populations but also different natural or cultural environments. This is especially true for humans. The cultural environment usually differs, even when the natural environment is the same.
• If the alleles of a gene perform differently, some of them will be more useful to one population than to another because they do better in one environment than in another. The more differently they perform, the more their frequencies will differ across population boundaries, with some alleles being more common in some populations than in others. Conversely, if the alleles perform identically, they will do equally well in all environments and tend to be equally common in all populations. To the extent that different alleles are present within a single population, the reasons will be more stochastic and less related to the usefulness of any one allele. Genetic variation within a population is therefore disproportionately due to alleles that perform similarly.

So genetic variation between populations differs qualitatively from genetic variation within each population. The first kind matters a lot more than the second kind. There are exceptions to this rule, e.g., balanced polymorphisms, founder effects, genetic drift, but that's the general picture. So when you read that genes vary far more within human populations than between them, you should keep in mind that we see the same pattern with many sibling species that are nonetheless anatomically and behaviorally distinct. This pattern tells us only that the populations in question are very young. It doesn't tell us how different they really are from each other, since real evolutionary change can happen very fast—as we saw with the Italian wall lizards. 

References

Berry, J.W. (2008). Models of Ecocultural Adaptation and Cultural Transmission: The Example of Inuit Art, paper presented at the conference Adaptation et socialisation des minoritiés culturelles en région, June 3-4, Quebec City.

Berry, J.W., and L.L. Cavalli-Sforza. (1986). Cultural and genetic influences on Inuit art. Report to Social Sciences and Humanities Research Council of Canada, Ottawa.

Boyd, R. and P.J. Richerson. (1985). Culture and the Evolutionary Process, Chicago: Chicago University Press.

Feldman, M.; Cavalli-Sforza, L. (1976). Cultural and biological evolutionary processes, selection for a trait under complex transmission, Theoretical Population Biology, 9: 238-59.

Frost, P. (2014). L.L. Cavalli-Sforza. A bird in a gilded cage, Open Behavioral Genetics, March 28,

http://openpsych.net/OBG/2014/03/l-l-cavalli-sforza-a-bird-in-a-gilded-cage/

Frost, P. (2011). Human nature or human natures? Futures, 43: 740-748.

https://www.researchgate.net/profile/Peter_Frost2/publication/251725125_Human_nature_or_human_natures/links/004635223eaf8196f0000000.pdf  
Lévi-Strauss, C. 1971). Race et culture, conférence de Lévi-Strauss à l'UNESCO le 22 mars 1971 (Audio). Polit'productions
http://politproductions.com/content/%C2%ABrace-et-culture%C2%BB-conf%C3%A9rence-de-l%C3%A9vi-strauss-%C3%A0-lunesco-le-22-mars-1971-audio  

Stone, L. and P.F. Lurquin. (2005). A Genetic and Cultural Odyssey. The Life and Work of L. Luca Cavalli-Sforza, New York: Columbia University Press.

Winegard, B., B. Winegard, and B. Boutwell. (2017). Human biological and psychological diversity, Evolutionary Psychological Science, 3(2): 159-180.

http://atavisionary.com/wp-content/uploads/2017/05/Human-Biological-and-Psychological-diversity.pdf