French Canadians: an evolving gene pool

In French Canadians, Tay Sach’s is caused by 2 different mutations that arose within a relatively small geographic area and short time frame (neither mutation is reported in France). This area (Bas St-Laurent and Charlevoix) is also the one where English Canadian merchants and managers were historically the least present. Is there a link between the two?

The field of human genetics has focused more on some gene pools than on others, with French Canadians being one of its favorites. There are two reasons:

1. While numbering some six million today in Quebec alone, they descend almost entirely from 8,500 or so founders—mostly French settlers with some Amerindian and British admixture. Such a homogeneous gene pool can more easily show how mutations spread and how natural selection works.

2. The genetic lineages are relatively easy to reconstruct for the past three to four centuries, partly because French Canadians have tended to stay put in the same locality, at least until recently, and partly because Catholic parishes have kept detailed records of births, marriages, and deaths.

The French Canadian gene pool is showing us that human evolution did not stop in remote prehistoric times. Yes, natural selection is ongoing. It has produced significant genetic change even over the last three to four centuries.

Decline in Amerindian admixture

One example of recent selection is the decline in Amerindian admixture. According to a genealogical study of parish registers, Amerindians made up 1.2% of all founders but now account for only 0.1 - 0.3% of current ancestry (Bherer et al., 2010).

Both estimates certainly understate Amerindian admixture. Such admixture was under-reported by parish registers because it tended to occur in frontier areas and through common-law marriages. Amerindian admixture also entered the French Canadian gene pool via Acadians, whom Bherer et al (2010) list as a separate ethnic group.

Nonetheless, this under-reporting should have affected the above two estimates more or less equally. If we look at the lineages for which we do have information, it seems that Amerindian admixture has tended to reduce their reproductive success.

Why? One reason is that it largely occurred among French settlers who were already more marginal than average, either socially (lower on the social scale) or spatially (farther away from the main zone of settlement). Such people had fewer opportunities for success and thus tended to have fewer children who would survive to adulthood.

Ferron and Cliché (1982, p. 35) describe this social differentiation for Beauce County, in southeastern Quebec:

Beginning in the 19th century, the inhabitants were split into two social groups. In one, the inhabitants were stable, hardworking, preoccupied with their heritage of land and family, and governed by an increasingly strict ethic. In the other group were the marginal folk, the métissés [mixed with Amerindians], the less rich, and those who mucked about. They would settle on the periphery of the parish, in “the concessions” …

Because the two groups differed in their circumstances, behavior, and sub-cultural characteristics, it is hardly surprising that they followed different trajectories of reproductive success.

Tay Sach’s: founder effect or selection?

Tay Sach’s disease is unusually common among French Canadians, particularly in eastern Quebec. In Rimouski, the heterozygote frequency is 7.6%, compared to 4.2% for Ashkenazi Jews and 0.3% for French Canadians in Montreal (De Braekeleer et al, 1992). The medical literature almost always explains it as a founder effect that was amplified by the rapid population growth of French Canadians from the mid-18th to mid-20th centuries.

This explanation is challenged by Zlotogora (1994), who points out that French Canadian Tay Sach’s is produced by two different mutations: one that originated on the south shore of the lower St. Lawrence and another that originated on the north shore (Charlevoix County). Neither mutation has been reported from France. Thus, on two separate occasions and in a very small population, something has maintained a genetic mutation that has failed to maintain itself in a much larger population.

Nor does a founder effect easily explain how 2 out of 8,500 founders (0.02%) could have produced the incidences we now see in eastern Quebec or even French Canada in general.

In Ashkenazi Jews, the high incidence of Tay Sach’s has been attributed to natural selection, specifically some advantage associated with mental processing. Indeed, Tay Sach’s is one of four different genetic illnesses that are unusually common among Ashkenazim and that affect the same metabolic pathway in brain tissues (lysosomal storage) (Zlotogora, 1994). In the homozygous state, the alleles in question produce neurological degeneration, mental retardation, and other neural problems. In the heterozygous state, however, they may have helped Ashkenazi Jews cope with mentally demanding occupations, such as in finance or in cottage industry crafts (Cochran et al., 2006; Frost 2007; Murray, 2007)

But why would this natural selection operate among French Canadians? Weren’t they the ones who toiled on the land and in the factories while English Canadians monopolized the skilled brainwork of trade, accounting, and management? First of all, this is a caricature of reality. There has always been a French Canadian middle class, although it was historically smaller in size than the English Canadian one.

More to the point, middle-class English Canadians were not uniformly spread across the province. Demographically and economically, they used to dominate the Ottawa valley, the Montreal area, the Eastern Townships, Quebec City, and the eastern and southern portions of the Gaspé Peninsula. Economically, they also dominated the hinterland of Trois-Rivières and the Lac Saint-Jean region (timber industry). This leaves two regions where, historically, they were virtually non-existent—the same regions that report unusually high incidences of Tay Sach’s.

An economic niche existed and had to be filled. In the absence of ethnic outsiders, middle-class French Canadians would have had more opportunities to go into business, marry earlier, and have larger families. Is this what happened in the lower St. Lawrence and Charlevoix County?

An obvious test would be to review Tay Sach genealogies in these two regions to see whether heterozygotes were over-represented in mentally demanding occupations, i.e., small business, law, medicine, accounting, etc.

References

Bherer, C., D. Labuda, M.-H. Roy-Gagnon, L. Houde, M. Tremblay, and H. Vézina (2010). Admixed ancestry and stratification of Quebec regional populations, American Journal of Physical Anthropology, in press.

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

De Braekeleer, M., P. Hechtman, E. Andermann, and F. Kaplan. (1992). The French Canadian Tay-Sachs disease deletion mutation: identification of probable founders, Human Genetics, 89, 83-87.

Ferron, M. & R. Cliché. (1982). Les Beaucerons. Ces insoumis, Montreal: Hurtubise HMH.

Frost, P. (2007). Natural selection in proto-industrial Europe, Evo and Proud, November 16.
http://evoandproud.blogspot.com/2007/11/natural-selection-in-proto-industrial.html

Murray, C. (2007). Jewish Genius. Commentary, April

Roy-Gagnon, M-H., C. Moreau, C. Bherer, P. St-Onge, D. Sinnett, C. Laprise, H. Vézina, D. Labuda. (2011). Genomic and genealogical investigation of the French Canadian founder population structure, Human Genetics, in press.

Zlotogora, J. (1994). High frequencies of human genetic diseases: founder effect with genetic drift or selection? American Journal of Medical Genetics, 49, 10-13.

Religiosity and the origins of civilization

Scenes of daily life from Sumer. The causes of civilization are not to be found in early art, writing, or architecture. These are merely the consequences of a preceding mental revolution.

Humans have gone through three stages of development: hunting/gathering, simple agricultural societies, and complex agricultural societies. The last stage brought us most of what we call “civilization”— state formation, class differentiation, urbanization, writing systems, literate culture, and so on.

What caused this transition from simple to complex agricultural societies? Was it simply the passage of time? Doubtful. Some societies have made this transition sooner than others. Others have never made it.

According to Atkinson and Whitehouse (2011), this debate has shifted away from technological causes and toward social and symbolic ones:

The main drivers of the great transition from small-scale hunter-gatherer societies in the pre-pottery Neolithic to the vast and complex civilizations of East Asia, MesoAmerica and the Fertile Crescent are still much debated […] Doubts have been growing with respect to the explanatory power of technological innovation, and attention has been focused increasingly on changes in social and symbolic worlds.

For the two authors, the change in the mode of subsistence (from hunting/gathering to agriculture) paved the way for a change in the mode of religiosity. It was this second transition that actually made the complexification of society possible. Humans became accustomed to a more systematized and accumulative form of thinking, and it was this new mental space that eventually became translated into a new physical space of buildings, roads, towns, and so forth.

Atkinson and Whitehouse argue that human societies seem to cluster into two modes of religiosity:

1. An “imagistic” mode associated with hunter-gatherers. Religiosity is focused on non-routine events that evoke an intense state of mental arousal (initiation, ordeals, bodily mutilation, etc).

2. A “doctrinal” mode associated with agricultural societies. Religiosity is more routine and is focused on frequently repeated teachings and rituals that generally evoke a less intense state of mental arousal.

Among hunter-gatherers, religiosity is meant to be traumatic. The aim is to create a vivid experience with long-lasting effects, such as an emotional bond that will keep men loyal to each other for hunting or war.

In agricultural societies, religiosity supports tasks that occur more often and more regularly:

Whereas the exploitation of wild resources requires only sporadic group co-operation (e.g., in hunting larger game), the domestication of animals and plants fosters increasingly routinized forms of collaborative labour (e.g., clearing, planting, harvesting and building). In traditional societies, such activities are typically punctuated by rituals.

There is thus selection for a new kind of mental space:

Put simply, the proposed doctrinal mode is seen as favouring high-frequency, low-arousal rituals, allowing large bodies of religious teachings to be stored in semantic memory, reproduced stably and spread efficiently as oral tradition.

[…] The doctrinal mode is based around frequently repeated teachings and rituals. High-frequency ritual performances allow complex networks of ideas to be transmitted and stored in semantic memory and give rise to generic identity markers ascribed to large-scale ‘imagined communities.’

It was this new mental space that made complex societies possible. Thus, the causes of civilization are not to be found in early art, writing, or architecture. These are merely the consequences of a preceding mental revolution. Atkinson and Whitehouse argue that the doctrinal mode of religiosity created a positive feedback loop of increasing cultural complexity:

If the emergence of agriculture drives an overall increase in the frequency of communal rituals, it also indirectly opens up opportunities for other features of the doctrinal mode to appear.

Other features might include organized priesthoods, ways to codify, transmit, and organize religious traditions (such as writing), and methods to enforce group cooperation and resource control.

Atkinson and Whitehouse do not ask why this mental revolution occurred in some agricultural societies and not in others. Tropical horticulturalists, for example, seem to have permanently stalled at the stage of simple societies. One reason may be that year-round agriculture enables women to provide for themselves and their offspring with limited male assistance. When agriculture is largely a female task, it is less likely to generate communal forms of religiosity that structure everyone’s mental space.

In addition, female reproductive autonomy reduces the costs of polygyny and thus increases male-male rivalry for mates. Such rivalry makes it harder to bring the men of a community together into stable communal structures. Yet such structures must be in place before rituals can become fully communalized on a regular basis, this being the first step toward complexification of mental space and, hence, society itself.

Reference

Atkinson, Q.D. & H. Whitehouse. (2011). The cultural morphospace of ritual form : Examining modes of religiosity cross-culturally, Evolution & Human Behavior, 32, 50-62.

On Neanderthals, Denisovans, and other archaics

Andaman Islanders. Related peoples once inhabited the coastal regions of southern, southeastern, and eastern Asia.

The past year brought two major advances: the long awaited sequencing of the Neanderthal genome and the genetic sequencing of an another archaic human, the Denisovans of East Asia, whose existence had previously been unsuspected.

The bottom line comes down to four points:

Before the East African ‘big bang’ gave rise to modern humans some 80,000 to 60,000 years ago, there had been at least four groups of archaic humans:

a) Skhul-Qafzeh hominins
- were almost modern anatomically
- were derived from a demic expansion that spread over most of Africa and the Middle East about 110,000 years ago
- evolved directly into modern humans through the rapid expansion of an East African subgroup

b) Neanderthals
- differed much more anatomically from modern humans
- were behaviorally similar to Skhul-Qafzeh hominins
- probably had body fur and other cold adaptations
- were derived from an earlier expansion out of Africa 250,000 - 400,000 years ago
- inhabited Europe, the Middle East (during glacial maxima), Central Asia, and Siberia as far east as Lake Baikal

c) Hobbits
- were small and possibly a form of Homo erectus
- inhabited at least a portion of southeast Asia
- may have been a regional variant of the Denisovans

d) Denisovans (Homo altaiensis?)
- were another archaic population distinct from modern humans
- inhabited Asia from Lake Baikal eastward (see earlier post)

These archaic humans have left significant genetic admixture in all modern human populations. The admixture is about 1 to 4% in Eurasians (from Neanderthals), 8% in Melanesians (from Neanderthals and Denisovans), and 13% in sub-Saharan Africans (from Skhul-Qafzeh-like hominins).

This admixture might have accelerated human evolution by providing modern humans with useful alleles. To date, no such alleles have been found. The admixture seems to be confined to genes of low adaptive value.

Although Denisovans inhabited East Asia, they left no admixture in present-day East Asians. Yet their admixture is discernible in present-day Melanesians. It seems that the first modern humans to replace Denisovans were not ancestral East Asians but rather ancestral Melanesians. This is consistent with archeological and ethnographic evidence that the coastal regions of southern, southeastern, and eastern Asia were initially settled by people related to the indigenous populations of Melanesia, Papua-New Guinea, and Australia. After the last ice age, they were gradually replaced by populations originating in northern Eurasia (see earlier post). Today, they survive in relic groups like the Veddas of Sri Lanka, the Andaman Islanders, the Semang of the Malayan peninsula, and the Aeta of the Philippines.

References

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

Reich, D., R.E. Green, M. Kircher, J. Krause, N. Patterson, E.Y. Durand, et al. (2010). Genetic history of an archaic hominin group from Denisova Cave in Siberia." Nature, 468, 1053-1060.

Watson, E., P. Forster, M. Richards, and H-J. Bandelt. (1997). Mitochondrial footprints of human expansions in Africa, American Journal of Human Genetics, 61, 691-704.

Looking forward to 2011

Time to die. This parasitic fungus begins as a spore on an ant’s body. It germinates, grows inside its host and eventually directs the ant’s brain to climb a plant and clamp its mandibles around a leaf or stem. The fungus then kills its host.

It won’t be such a bad year. Stock markets will reach record highs and pundits will say we’ve entered a sustained boom. For many people, life will never again be so good as it will be this year.

The main worry will be price rises for many commodities. With a return to even modest rates of economic growth, demand will outstrip supply in several areas. Talk of “peak oil” will be joined by concerns over “peak food” and “peak water.” Serious water shortages will hit the American southwest and southeast.

There will also be concern over the decline in physical infrastructure, i.e., roads, bridges, and the like. Most of this infrastructure was built during the postwar boom of the 1950s and 1960s. Now it’s falling apart.

Finally, there will be concern over behavioral infrastructure, albeit less openly expressed. The market economy may be self-generating, but it doesn’t self-generate in a vacuum. As the historical economist Gregory Clark has shown, the market economy began to develop once a certain behavioral profile had become the norm—above all, a commitment to honesty and a rejection of violence and theft as means of self-enrichment. If the current population is replaced by one where people casually cheat and steal, transaction costs will escalate throughout the economy. A lot of economic activity will simply cease to be cost-effective.

Economists are afraid that a sharp rise in interest rates will abort the present recovery. Or a sharp rise in commodity prices. Frankly, I’m more worried about the behavioral changes.

Yes, humans are ingenious creatures. We’ll undoubtedly think of something. Nonetheless, the coming decade will confront us with several different challenges. Do we have enough fingers to plug all the holes in the dike? I’m not so sure, especially given the obliviousness of our political and economic elites.

Anyway, these problems won’t really bite until the second half of the decade. So enjoy life.

This year, I’ll try to use my recent book, Femmes claires, hommes foncés. Les racines oubliées du colorisme, to raise awareness of skin tone and gender/face recognition.

In short, the human face is a special visual object. We don’t learn to recognize it. Instead, the brain has a hardwired capacity for face recognition. This point is no longer debated. Controversy begins when we turn to the elements of this hardwired facial schema.

It is increasingly apparent, especially with recent work by Richard Russell and by Frédéric Gosselin’s research team, that one key element is skin tone, specifically facial coloration and luminosity. This visual element is apparently used to distinguish between male and female faces.

In pursuing this line of research, we should above all:

- locate the region of the brain that harbors this mental module. Gosselin’s team suggest that the location may be in the infero-temporal cortex, which handles both face perception and color perception. The best approach would likely be a real-time MRI study.

- show that this mental capacity is indeed hardwired and not learned. The best approach would be a twin study, such as Zhu et al (2009) used to show that face recognition is hardwired.

- identify other areas of cognition and behavior (sexual attraction, emotional distancing, etc.) that may be influenced by the output of this module.

The challenge here is not so much funding as access to special resources (real-time MRI brain scanning, large pools of identical and fraternal twins, etc.). And beyond that challenge lies another one: persuading other academics that this line of research is worth pursuing.

Other topics

This year, I hope to write posts on the following two topics. Depending on what turns up, these posts may eventually become publishable articles.

Parasite manipulation: Certain parasites can manipulate host behavior in a number of surprisingly specific ways. Although parasite manipulation has been documented for many non-human species, possible human examples are still lacking. One problem is paradigmatic. When a non-human animal acts strangely, we suspect parasite manipulation. When a human acts strangely, we just see a strange behavior.

I will argue that a likely candidate for parasite manipulation in our species is vaginal yeast, specifically the more aggressive strains associated with vulvovaginal candidiasis. This parasite has evolved the capacity to cross the blood/brain barrier and may manipulate certain neural circuits in both the female host and her regular male partner.

A new cold war? When the Cold War ended some two decades ago, it seemed that we had come to the “end of history.” All nations now agreed on the best social system: a free market economy combined with certain communitarian values (the family, the local community, the nation, etc.).

Yet, after a period of apparent convergence, the world is once more repolarizing into two opposing blocs. In the Eastern bloc, the decline of Marxism-Leninism has allowed a resurgence of pre-revolutionary social values, often with the encouragement of the State. Meanwhile, these same values are withering away in the Western bloc. Our ideal is now the self-defining individual who freely operates within a post-national, post-gender, and post-family world. But this freedom does not include the right to adhere to older social values. Such adherence is increasingly scorned as pathological, if not criminal.

This repolarization is especially visible on the Korean peninsula, where it is fueling renewed tensions. Will we see a Second Korean War? And will this war escalate into a larger, more global conflict?

References

Brainwashed by a parasite, Neurophilosophy, August 9, 2007
http://scienceblogs.com/neurophilosophy/2007/08/brainwashed_by_a_parasite.php

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

Clark, G. (2009). The indicted and the wealthy: surnames, reproductive success, genetic selection and social class in pre-industrial England,
http://www.econ.ucdavis.edu/faculty/gclark/Farewell%20to%20Alms/Clark%20-Surnames.pdf

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

Frost, P. (2010). Femmes claires, hommes foncés. Les racines oubliées du colorisme, Quebec City: Presses de l’Université Laval.

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

Russell, R., B. Duchaine, and K. Nakayama. (2009). Super-recognizers: People with extraordinary face recognition ability. Psychonomic Bulletin & Review, 16(2):252-257.

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

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

Zhu, Q., Y. Song, S. Hu, X. Li, M. Tian, Z. Zhen, Q. Dong, N. Kanwisher, and J. Liu. (2009). Heritability of the specific cognitive ability of face perception, Current Biology, 20:137-142.