Friday, 28 January 2011

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.

10 comments:

Tod said...

The " skilled brainwork of trade, accounting, and management" is not too different from the GC/HH paper but "they may have helped Ashkenazi Jews cope with mentally demanding occupations, such as in ... cottage industry crafts" is quite a bit different. Cottage industry crafts are not the same thing as finance and management, number of such jobs is pretty limited but most importantly the crucial aspect which you stressed in 2007 is missing.

"They were not specialized craftsmen in life-trades with skills developed through long years of apprenticeship; they were semi-skilled family labour teams which set up in a line of business very quickly, adapting to shifts in market demand" (Seccombe, 1992, p. 182). Their workforce was their household. In more successful households, the workers would marry earlier and have as many children as possible. In less successful ones, they would postpone marriage or never marry."

That is not true of finance at all.

Architects of Annihilation: Auschwitz and the Logic of Destruction,(2002) P. 47 Says of the 30s
" the majority of Poland's Jews worked in commerce or the skilled trades. For the most part they were self employed, often running tiny businesses stalls or workshops from which the owner could barely make a living. The Jewish industrial workers were employed for the most part in small scale enterprises where frequently the entire workforce was Jewish[...] Most Jewish traders did not sell their goods through shops as such - not as visitors to Poland from Western Europe understood the term. Instead they worked the streets,selling from handcarts, hawkers tray. market stalls, or straight out of their coat pockets. They bartered or sold all manner of household goods, new or second hand, complete or incomplete. Cobblers, tailors, tinkers or knife grinders frequently set up shop in the single room where a family of four lived, or else the carried their tools around with them For many Jew , children as well as adults necessity had been the mother of invention, reviving trades which had long since disappeared from other parts of Europe - the water carrier for example. There was not a lot of money to be made in such businesses"

The kids can help out a semi skilled family team. Ally cites a estimate (by a Nazi of course) that the Jewish population in Eastern Europe went from 2 million in 1800 to 7 million in 1900 The book continues 'there had been a 'multiplication in the number of Jews [in eastern Europe] such had never been seen'"

Tay Sach's is a evolutionarily sub optimal 'quick fix' which imposes considerable fitness costs in illnesses. I think that is a reason to think disease causing mutations are a response to a sudden new situation (ie Cottage industry crafts) rather than a long standing occupation followed by a few of high status (ie financiers) which slowly spread downwards as I believe GC and HH's paper is saying.

Thats not to say that Jewish financiers and bankers did not lead to some kinds of genes for intelligence speading though the Jewish population over the very long haul. But I think that kind of evolution would be slow but sure and not result in any genetic illnesses. French Canadians got one variety of the the 'quick fix'.

Siryako said...

"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."

So products of miscegenation are ultimately weeded out in the long run?

Ben10 said...

What about the Tay Sacks, in the genetic context of the french canadians, is doing something different, in the heterozygous state that is, than being (supposedly) supersmart like in the jewish genetic background.

Wikipedia says:
"French Canadians of southeastern Quebec have a carrier frequency similar to Ashkenazi Jews, but they carry a different mutation"

Being dropped in a different environnment than metropolitan France, they certainly didn't just face the need to be smart where anglos where absent (ahemmm, note: dumb farmers don't live longer than dumb merchants).
What about fertility in the french canadians ?
Huge families were reported, like 8, 10, 12 kids. People say it was 1) the 'custom' of the time and 2) the pressure from the catholic church, but honestly, these numbers seem crazy. At the same time in France, I doubt you could easily find families of 12, and I'm pretty sure the local curé, would have been as happy with families of 6 than families of 12. So, somehow, french canadian women seem to have been super-fertile for a while and, to me, 12 kids is a little bit weird. Maybe the female hets T-S carriers were superfertile.
It would be interesting to know the average size family of these TS carriers during Quebec's history.

Kiwiguy said...

OT, but interesting paper by some Chinese researchers:

" Here, we study the level of population differentiation among different populations of human genes. Intriguingly, genes involved in osteoblast development were identified as being enriched with higher FST SNPs, a result consistent with the proposed role of the skeletal system in accounting for variation among human populations. Genes involved in the development of hair follicles, where hair is produced, were also found to have higher levels of population differentiation, consistent with hair morphology being a distinctive trait among human populations. Other genes that showed higher levels of population differentiation include those involved in pigmentation, spermatid, nervous system and organ development, and some metabolic pathways, but few involved with the immune system."

Different level of population differentiation among human genes

Anonymous said...

Continuing from the previous article, this tells us why men are more important to civilisation and culture than women.

It is the way that men attract mating partners. Women have no such need, so vastly fewer of them do.

Tod said...

Ben 10, asked "What about fertility in the french canadians ?"

Read the linked article. The most successful men in cottage industries had the biggest families in order to expand their workforce. Having 12 kids made perfect sense from a commercial point of view if you were succesful.

Tay Sach’s is like Nitrous oxide injection for a gasoline engine. To make a reliable engine there has to be a long testing program. If you suddenly need a more powerful engine but don't have the time to develop a new one the fastest and most simple way is to use nitrous oxide injection on your old engine. Of course the engine will suffer more malfunctions as a result.

So from a evolutionary point of view natural selection was 'telling' French Canadians in Lawrence and Charlevoix County 'get smarter now, I don't care how you do it, just do it.

The reason that the English in Canada dont have Tay Sach’s is that they were the result of large and long drawn out testing program for 'smart genes'. The English in Canada were the result of selection on a far bigger population, with a bigger choice of advantageous genes.

Anonymous said...

Of course, it further has to be stated that the level of civilisation seen in, say, China or Europe, is not possible in places where women can support themselves and their offspring by themselves.

So, in some sense, it is a blind outcome of selection forces, but there is no selection pressure on the child-bearing sex (which, by definition, must be female) to be innovative or eschew well-worn practice for something that just might work; her genetic future is damned the minute she does that.

It is only those males who's genetic future is already damned who would risk doing something new ...

So much of our behavior is genetically programmed.

Peter Frost said...

Tod,

Yes, people in cottage industries led Europe's great demographic expansion, particularly during the 1700s and early 1800s and particularly in Great Britain, the Netherlands, and the Ashkenazi communities of Eastern Europe. Their genetic characteristics became, to a large degree, those of modern Europeans.

I see this especially in my mother's family tree (the Corkings). They were either small-time merchants or craftsmen, and initially (early 1700s they had only 3 children per generation. Then, in the late 1700s they started having around a dozen children per generation.

Siryako,

No, it depends on the circumstances. In much of Latin America, there was a similar "lightening" trend. Natural increase was higher among the White or near-White elements of the population, and these elements tended to become proportionately greater over time, even in places (like Puerto Rico) where European immigration was limited.

Ben10,

In Quebec, high fertility was the rule almost everywhere. In contrast, Tay-Sachs is very unevenly distributed.

Anon,

You're going off on a tangent. If we return to the original question, women were just as present as men in communal structures of religiosity, e.g., priestesses, prophetesses, seers, vestal virgins, wise women, etc.

Tod said...

Slight error in punctuation above corrected version reads :-

The book continues "there had been a 'multiplication in the number of Jews [in eastern Europe] such had never been seen'"



Also I was a bit careless above with a quote from Aly's book which ought to read :-

"For many Jews, children as well as adults, necessity had been the mother of invention"

Anonymous said...

AND in Novia Scotia there is an increased incidence of a variant of another disease which is more commonly found in Ashkenazi Jews (Niemann Pick type A). The incidence of Niemann-Pick type D is concentrated at higher frequencies in Novia Scotia. I hypothesize that the incidence of these disease has nothing at all to do with selection for intelligence but instead is correlated by unknown mechanisms with the incidence of curly black hair.