Friday, August 27, 2010

A late convert

Cavalli-Sforza with Kistler Prize (2002). The paths of Glory lead …

Human Biology has interviewed Luigi Luca Cavalli-Sforza, probably the best-known human geneticist (Manni, 2010). His worry? The growing rift between anthropology and biology:

Unfortunately, at least in the United States, anthropology is in decline: The cultural moiety is separating from the rest and loves to declare that it is not science—what is it, instead? The rest of the U.S. anthropology departments (variable according to places, but mostly a mixture of physical anthropology, primatology, archaeology, linguistics) fortunately seem to resist this trend, but anthropology seems to be losing ground. There is a need for a new anthropology capable of keeping unity, and to develop human science curricula that may promote an original, fresh outlook.

Why this retreat from biology? Ask almost any anthropologist. You’ll be told that there is much more genetic variation within human populations than between them. With culture, we see the reverse: the differences are primarily between populations. So how can genetic differences explain cultural differences? Such explanations are inevitably wrong and, needless to say, dangerous.

And you’ll be told that this view is endorsed by all credible geneticists, including Cavalli-Sforza. Just read the same interview:

Don’t you feel that results pointing to intracontinental genetic differences can reinforce racist theories, as some pharmacogenomic studies recently did?

LLCS: The between-population genetic variation observed with 650,000 SNPs on the 52 populations of the HGDP is 11% (Li et al. 2008) with a very small standard error. It becomes 16% for the X chromosome, as is expected if nearly all the genetic variation is due to drift—that is, the role of natural selection is very limited. The ca. 30-year-old estimate by Lewontin (1972) of this quantity (15%) was based on other markers and populations and was a reason to encourage banning the use of the word race in humans. In any case the new value is even more supportive of dropping the word race. What we really need to ban is racism, and this is not a socially easy-to-do program. Charles Darwin, already, was skeptical about the usefulness of the race concept in humans, having noted that human variation is geographically almost continuous for most traits.

Man has been studied more carefully than any other animal, and yet there is the greatest possible diversity amongst capable judges whether he should be classed as a single species or race, or as two (Virey), as three (Jacquinot), as four (Kant), five (Blumenbach), six (Buffon), seven (Hunter), eight (Agassiz), eleven (Pickering), fifteen (Bory St. Vincent), sixteen (Desmoulins), twenty-two (Morton), sixty (Crawfurd), or as sixty-three, according to Burke. This diversity of judgment does not prove that the races ought not to be ranked as species, but it shows that they graduate into each other, and that it is hardly possible to discover clear distinctive characters between them.
(Darwin 1871: 226)

Well, no. Darwin was not “skeptical about the usefulness of the race concept in humans” In the above quote, he was denying that humans had diverged into different species. But he did not deny the reality of human races, as he stated a few pages previously:

There is, however, no doubt that the various races, when carefully compared and measured, differ much from each other,—as in the texture of the hair, the relative proportions of all parts of the body, the capacity of the lungs, the form and capacity of the skull, and even in the convolutions of the brain. But it would be an endless task to specify the numerous points of difference.

[…] If a naturalist, who had never before seen a Negro, Hottentot, Australian, or Mongolian, were to compare them, he would at once perceive that they differed in a multitude of characters, some of slight and some of considerable importance. On enquiry he would find that they were adapted to live under widely different climates, and that they differed somewhat in bodily constitution and mental disposition. If he were then told that hundreds of similar specimens could be brought from the same countries, he would assuredly declare that they were as good species as many to which he had been in the habit of affixing specific names.

But why bother quoting Darwin? It’s more fun to quote Cavalli-Sforza!

The differences that exist between the major racial groups are such that races could be called subspecies if we adopted for man a criterion suggested by Mayr (1963) for systematic zoology. Mayr’s criterion is that two or more groups become subspecies when 75 percent or more of all the individuals constituting the groups can be unequivocally classified as belonging to a particular group. As a matter of fact, when human races are defined fairly broadly, we could achieve a much lower error of classification than 25 percent, implying, according to Mayr, the existence of human subspecies. (Cavalli-Sforza & Bodmer, 1977)

Well, that was Cavalli-Sforza back in 1977. Perhaps he was still unaware of Richard Lewontin’s finding that genes vary much more within human populations than between them. Was not this “a reason to encourage banning the use of the word race in humans”?

Except that Lewontin had published that reason in 1972. Five years later, Cavalli-Sforza was apparently still unimpressed. And he continued to use the race concept much later, as in this journal article from the late 1980s:

The first split in the phylo-genetic tree separates Africans from non-Africans, and the second separates two major clusters, one corresponding to Caucasoids, East Asians, Arctic populations, and American natives, and the other to Southeast Asians, (mainland and insular), Pacific islanders, and New Guineans and Australians (Cavalli-Sforza et al., 1988).

Cavalli-Sforza did not convert to race denialism until the mid-1990s, with his opus The History and Geography of Human Genes.

What motivated his conversion? Had Lewontin’s 1972 paper been further bolstered by new data and arguments? Not really. In fact, the 1980s and 1990s saw growing evidence that the same genetic overlap that Lewontin found between human populations also occurs between many species that are nonetheless distinct in anatomy, physiology, and behavior (see previous post).

As one anthropologist told me: “I don't think our perception of the general patterns of genetic variation changed much from '76 to '94, but the intellectual climate that geneticists operate in sure did.”


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

Cavalli-Sforza, L.L., A. Piazza, P. Menozzi, and J. Mountain. (1988). Reconstruction of human evolution: Bringing together genetic, archaeological, and linguistic data. Proc. Natl. Acad. Sci. USA, 85, 6002-6006.

Cavalli-Sforza, L.L. and W.F. Bodmer. (1977). The Genetics of Human Populations, San Francisco: W.H. Freeman and Co.

Darwin, C. R. (1871). The Descent of Man, and Selection in Relation to Sex. London: John Murray.

Lewontin, R.C. (1972). The apportionment of human diversity. Evolutionary Biology, 6,

Manni, F. (2010). Interview with Luigi Luca Cavalli-Sforza: Past research and directions for future investigations in human population genetics, Human Biology, 82, 245–266.

Friday, August 20, 2010

On infidelity

Demon of lust. Chartres Cathedral. To create larger and more complex societies, humans had to restrain impulses that were hitherto considered normal.

Michelle Langley has written an interesting critique of modern sexual behavior, especially with regard to women, In Women’s Infidelity, she argues that:

…. young females are conditioned to believe that they are naturally monogamous and they carry this belief with them throughout their lifetimes. So when women experience feelings that deviate from this belief, particularly after they are married, those feelings can cause enormous internal conflict. Many women resolve the dilemma by dissolving their marriages.

Some women find it easier to think they married the wrong guy than to see themselves as some sort of shameful freak of nature. Their erroneous belief in a monogamous predisposition prevents them from becoming aware of their natural sexual tendencies in the first place. This unawareness can cause a chain reaction that
ultimately destroys their marriages
. (Langley, 2005, pp. 19-20)

Evolutionary psychologists have long assumed that women are hardwired for monogamy. Men presumably learn to be monogamous. Today, both assumptions are in need of rethinking. As we strip away layer after layer of cultural restraint, female sexuality is deviating more and more from its supposedly innate pattern.

The truth is that culture has limited both male and female sexual behavior, specifically by restraining impulses that were hitherto considered normal. This is the price for living in larger and more complex societies. Such social environments work best when individuals can readily cooperate with others, particularly those of the same sex. No one trusts a sexual rival, and nothing destabilizes a society like large numbers of single men. To avoid this scenario, our ancestors had to limit male polygamy and female hypergamy.

How did they do it? In part, circumstances had already done it for them. In part, they consciously did it to themselves. This new niche was most successfully exploited by northern Eurasians who were already highly monogamous, since non-tropical environments made women and children more dependent on men, particularly in winter (Frost, 2008). Our ancestors then imposed cultural restraints to further limit male polygamy and female hypergamy—by shaming, ostracizing, and killing “deviant” individuals.

And now, as the restraints come off, we are no longer—surprise! surprise!—these faithful beings we thought we were.

The time has come to drop the idea that men and women are naturally good. This is a naïve kind of sociobiology that sees culture as an enemy—an unnatural force that prevents us from being truly human (and having fun!). Actually, culture is the main force that has made us human. It has helped us meet the requirements of new environments that are human-specific and that humans would have never colonized without its help. It has been part of our adaptive landscape, no less so than climate or food supply. And, as such, it has favored humans with the right predispositions and personality traits.

But this co-evolution is never complete. Our biological self always lags behind our cultural self. To the extent that we strip away the latter, we become less adapted to our environment. In plain language, we lose part of what we are.


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.

Langley, M. (2005). Women’s Infidelity. Living in Limbo. What women really mean when they say, “I’m not happy.” St. Louis (Mo): McCarlan Pub.

Friday, August 13, 2010

More on European hunter-gatherers

Medieval (?) ice cellar for meat storage (Sweden). Link: runlama
In northern climates, the yearly cycle of changing temperatures encouraged humans to think ahead to the next season.

My last post mentioned the debate over the provenance of present-day Europeans. Do they descend from the hunter-gatherers of Upper Paleolithic and Mesolithic Europe? Or were those people a dead end? Were they replaced by Middle Eastern farmers when agriculture spread into Europe 9,000 to 3,000 years ago?

This debate will eventually be settled when we can genetically compare late European hunter-gatherers with early European farmers. And ‘eventually’ is not far off. Much data will come on-stream over the next three years, probably enough to end the debate. The evidence will probably show that European hunter-gatherers did adopt farming, but not all of them to the same extent. Some did so before others and thus expanded at the latter’s expense. So my hunch is that European farming spread both culturally and demographically. The early farmers were not a random sample of the late hunter-gatherers.

But why is there so much resistance to the idea that European hunter-gatherers became farmers? One reason is that hunter-gatherers do not easily take to farming. This is a point that the anthropologist Marshall Sahlins made. Becoming a farmer is not just a matter of learning new techniques. It’s also a matter of acquiring a different outlook that is geared to future consumption. “Short-term pain for long-term gain.” Food has to be planted in the spring, harvested in the fall, and stored for winter.

Such a trade-off is rare in hunter-gatherer societies. There’s no point in tending a plot of land because you’re constantly on the move. There’s also no point in holding on to stuff because it has to be carried around.

As Sahlins (2005) puts it:

The hunter, one is tempted to say, is "uneconomic man". At least as concerns non subsistence goods, he is the reverse of that standard caricature immortalised in any General Principles of Economics, page one. His wants are scarce and his means (in relation) plentiful. Consequently he is "comparatively free of material pressures", has "no sense of possession", shows "an undeveloped sense of property", is "completely indifferent to any material pressures", manifests a "lack of interest" in developing his technological equipment.

Sahlins quotes from a monograph on the Yahgan Indians:

They do not know how to take care of their belongings. No one dreams of putting them in order, folding them, drying or cleaning them, hanging them up, or putting them in a neat pile. If they are looking for some particular thing, they rummage carelessly through the hodgepodge of trifles in the little baskets. Larger objects that are piled up in a heap in the hut are dragged hither and thither with no regard for the damage that might be done them.

The European observer has the impression that these (Yahgan) Indians place no value whatever on their utensils and that they have completely forgotten the effort it took to make them. Actually, no one clings to his few goods and chattels which, as it is, are often and easily lost, but just as easily replaced [...] The Indian does not even exercise care when he could conveniently do so. A European is likely to shake his head at the boundless indifference of these people who drag brand-new objects, precious clothing, fresh provisions and valuable items through thick mud, or abandon them to their swift destruction by children and dogs [...] Expensive things that are given them are treasured for a few hours, out of curiosity; after that they thoughtlessly let everything deteriorate in the mud and wet. The less they own, the more comfortable they can travel, and what is ruined they occasionally replace. Hence, they are completely indifferent to any material possessions.

For all these reasons, farming has spread more through the expansion of an existing population of farmers than through the conversion of hunter-gatherers.

Sahlins based his conclusions on those hunter-gatherer groups that exist today, generally tropical or semi-tropical groups like the !Kung and the Australian Aborigines. We know much less about the hunter-gatherers who used to roam across Europe. But we do know that they were more future-oriented and possession-oriented.

First, the changing seasons imposed a yearly cycle of resource availability. Natural selection thus favored humans who could plan their behavior with an eye to the next season. For example, it favored the construction of “ice cellars”—deep storage pits dug down to the permafrost as a way to store meat for future use (Hoffecker 2002, p. 161).

Second, the colder climate limited the number of game animals per square kilometer, thus forcing hunters to cover a larger land surface. This in turn favored a capacity to generate mental models of animal movement over space and time. It also favored a capacity (or rather a willingness) to manage traps and snares by periodically checking them.

As Hoffecker (2002, p. 135) notes about early modern humans, tools and weapons were more complex at arctic latitudes than at tropical latitudes. “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.”

Non-tropical humans coped with seasonal variation in resources by planning ahead. They were thus “pre-adapted” for later developments in cultural evolution, including the advent of agriculture.


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

Martin, G. (1961). The Yamana, 5 vols. New Haven, Conn.: Human Relations Area Files. (German edition 1931).

Sahlins, M. (2005).
The Original Affluent Society [Online] in M. Sahlins, Stone Age Economics

Friday, August 6, 2010

How long have Europeans been European?

How long have Europeans been in Europe? Clearly, their ancestors were not Neanderthals, except for an admixture of 1 to 4%. What about the modern humans who came about 35,000 years ago as hunter-gatherers? Or did they too die out? Were they replaced by Middle-Eastern farmers some 9,000 to 3,000 years ago?

This is an ongoing debate and a single study will not decide things one way or the other. In recent years, the evidence has been shifting towards the replacement model. In northern Europe, there seems to have been a genetic divide between late hunter-gatherers and early farmers (although the divide is just as great between the latter and present-day Europeans). In particular, European hunter-gatherers possessed genetic lineages (haplogroup U) that are rare among present-day Europeans.

Now, the pendulum is swinging back. After studying 92 Danish human remains that range in time from the Mesolithic to the Middle Ages, Melchior et al. (2010) have found evidence of genetic continuity from late hunter-gatherers to early farmers.

The extent to which early European farmers were immigrants or descendants of resident hunter-gatherers (replacement vs. cultural diffusion) has been widely debated, and new genetic elements have recently been added. A high frequency of Hg U lineages, especially U5, has been inferred for pre-Neolithic Europeans based on modern mtDNA data, with Hg U5 being fairly specific to Europe.

[…] The present findings indicate that predominantly haplogroup U lineages persist among Neolithic/Bronze Age population samples in Southern Scandinavia and it may point to regional variation in the penetrance rate of these lineages across cultural shifts in different areas of North Europe. Given our small sample sizes from these crucial time periods further studies are certainly required. However, the frequency of Hg U4 and U5 declines significantly among our more recent Iron Age and Viking Age Danish population samples to the level observed among the extant Danish population. Our study therefore would point to the Early Iron Age and not the Neolithic Funnel Beaker Culture as suggested by Malmström et al. (2009), as the time period when the mtDNA haplogroup frequency pattern, which is characteristic to the presently living population of Southern Scandinavia, emerged and remained by and large unaltered by the subsequent effects of genetic drift.

As the authors note, the sample sizes were small. But it is odd that all of the Neolithic and Early Bronze Age samples were either U4 or U5a. These lineages now account for only 1–5% and 5–7% of present-day Europeans.


Melchior, L., N. Lynnerup, H.R. Siegismund, T. Kivisild, J. Dissing. (2010). Genetic diversity among ancient Nordic populations, PLoS ONE 5(7): e11898.