French Canadians and recent cognitive evolution
Areas of high prevalence of Tay-Sachs, eastern Quebec
In French Canada, two alleles for Tay-Sachs arose independently, and over a short time span, in two adjoining areas that had few British or American merchants. Did that vacant niche favor the reproductive success of French Canadians with the right abilities?
Some 10,000 years ago, human genetic evolution sped up more than a hundred-fold. This was not because we were adapting to a lot of new natural environments. By then, our ancestors had already spread from the Tropics to the Arctic. We were adapting to an ever-widening range of cultural environments and, thus, to new ways of being, living, and doing (Cochran and Harpending 2009; Hawks et al. 2007; Rinaldi 2017).
Those new ways were “cultural” in a broad sense, and not in the narrow sense of “ethnic.” Culture is everything that humans do and make. Two populations can differ culturally and yet see themselves as the same ethnically.
The last point is important because cognitive differences are often associated with ethnic differences. Cognitive ability can diverge, however, even between populations that share the same ethnic identity. Let me explain, using the example of French Canada.
Tay-Sachs among French Canadians
Tay-Sachs is an inherited neurological disorder caused by defective storage of sphingolipids in neural tissue. Psychomotor deterioration appears around four to six months of age, followed by axial hypotonia, limb spasticity, seizures, and blindness. Death usually results by the age of four.
Tay-Sachs is common among Ashkenazi Jews and is often thought of as a Jewish disease. Yet it reaches a high prevalence in a few other populations, particularly French Canadians. Among the latter, it has three unusual characteristics:
It is highly localized, being concentrated in eastern Quebec. In Rimouski, the heterozygote frequency is 7.6%, versus 4.2% among Ashkenazi Jews and 0.3% among French Canadians in Montreal (De Braekeleer et al. 1992).
It is caused by two mutant alleles: one that is prevalent on the north shore of the St. Lawrence (regions of Charlevoix, Saguenay, Lac Saint-Jean) and another that is prevalent on the south shore (Bas Saint-Laurent) (Hechtman et al. 1992; Zlotogora 1994; De Braekeleer 1995).
It seems to be of recent origin. The two alleles are absent in France and must have reached their current prevalence after the British conquest of Quebec in 1759 (Hechtman et al. 1992; De Braekeleer 1995).
The above characteristics are inconsistent with a founder effect, i.e., a chance deviation in gene frequency between a population and its parental stock. A founder effect might be the cause if there were only one mutation. Here, two normally rare mutations, with the same physiological effect, have become prevalent in adjacent populations. This looks more like convergent evolution: two populations coming to resemble each other through the same pressure of natural selection.
A founder effect?
Yet the literature routinely explains French Canadian Tay-Sachs as a founder effect. This is largely because eastern Quebec has high rates of other genetic disorders. Surely they must all be due to founder effects of one sort or another. Or perhaps inbreeding. Or something.
Those other genetic disorders resemble Tay-Sachs in one curious respect. Of the top ten, six are primarily neurological and two secondarily so (Laberge et al. 2005). Is this pattern typical? Of the top ten genetic disorders in the United Kingdom, only three are primarily or secondarily neurological (Genetic Alliance UK 2016).
One of the eastern Quebec disorders, mucolipidosis type II, is a sphingolipid storage disease like Tay-Sachs. It reaches a heterozygote frequency of 2.6% in the regions of Saguenay and Lac Saint-Jean, the highest reported rate for this disorder (Plante et al. 2008). French Canadians are also thought to have high rates of two other sphingolipid storage diseases: Gaucher’s disease and mucopolysaccharidosis type IV (Laberge et al. 2005).
The alternative explanation is natural selection: carriers of Tay-Sachs have enjoyed a reproductive advantage over non-carriers. That explanation may seem unlikely because Tay-Sachs leads to early death and no reproduction. But that outcome happens only if the carrier has both copies of a Tay-Sachs allele (homozygote) and not just one (heterozygote). Because heterozygosity is much more common than homozygosity, the clear disadvantage of having two alleles could be offset by a slight advantage of having just one.
Does such an advantage exist? Tay-Sachs is caused by neural tissue storing excessive amounts of sphingolipids, which promote the growth of neural axons. Heterozygous individuals should be better at storing sphingolipids and forming new neural connections. They should thus have higher cognitive ability. If we look at another sphingolipid storage disorder, Gaucher’s disease, we see that engineers and scientists are at least six times more common among Israelis with Gaucher’s disease than among Ashkenazi Jews in general (Cochran et al. 2006).
The selection pressure that favored those sphingolipid storage alleles should have favored alleles elsewhere on the genome with similar effects, thus helping their carriers become better at reading, writing, calculating, negotiating, and planning, notably for buying and selling goods and producing crafts for a market (Cochran et al. 2006; Murray 2007). The Tay-Sachs allele would have thus become more common among Ashkenazi Jews, since successful traders and artisans contributed disproportionately to that community’s population growth, particularly its surge from an estimated 25,000 in 1300 to over eight and a half million by 1900 (DellaPergola 2001, p. 12).
Tay-Sachs in French Canada: historical and economic background
Is Tay-Sachs common in eastern Quebec for the same reason? The idea might seem farfetched. Were not French Canadians historically the farmers and English Canadians the businessmen?
In reality, there were always some French Canadian businessmen, but their numbers were limited by cultural and legal barriers or by competition from British and American immigrants. Those limitations varied over time and space. Whereas cultural and legal barriers were stronger under the French Regime, immigrant competition was stronger under the British Regime, especially in western and central Quebec.
French Regime (1608-1759)
French colonists saw the market as a very secondary source of the necessities of life. In the countryside, where three-quarters of them lived, each family produced most of its food, clothes, and furniture. People did not usually sell their labor in a market; instead, they would supply it under long-term agreements of mutual assistance, such as between tenant farmers and their seigneur. Farming itself was primarily for subsistence and only secondarily for sale of surplus produce to middlemen. Wheat yields were only 4 to 6 bushels per arpent (0.85 acre) (Ouellet 1966, pp. 8-9, 52-53, 81-82).
In the towns, markets did exist but were State-regulated. Government officials controlled food prices and wholesale trade (Vallières et al. 2008, pp. 219, 223, 520, 521). To give consumers first priority, merchants were forbidden to purchase from farmers before certain hours of the morning (Vallières et al. 2008, p. 505). Urban markets were localized in time and space, being typically marketplaces where buyer and seller met face to face and personally supervised each transaction. Those points in space could not coalesce into a true market economy largely because buyers and sellers did not trust each other enough.
Just as insufficient trust confined the market economy to localized points in space, lack of foresight confined it to the present point of time. People tended to sacrifice future needs for short-term gains, as noted by the Jesuit missionary and explorer Pierre-François-Xavier de Charlevoix:
The English colonist amasses worldly goods and makes no superfluous expenses; the French colonist enjoys what he has, and often shows off what he has not. The former works for his heirs; the latter leaves his own in need … (Ouellet 1966, p. 7).
That was one reason why French officials distrusted the market economy and had to intervene for the long-term interest. A similar view was held after the conquest by the first British governor, who saw the local mindset as a hindrance to development of a true market economy:
… the inhabitants are inclinable enough to be lazy, and not much skilled in Husbandry. [T]he great dependancies they have hitherto had on the Gun and fishing rod, [which] made them neglect tillage beyond the requisites of their own consumption and the few purchases they needed, the Monopolies that were carried on here in every branch, [which] made them careless of acquiring beyond the present use, and their being often sent on distant parties and detachments, to serve the particular purposes of greedy and avaricious men without the least view to public utility, were circumstances under which no country could thrive (Murray 1902 , pp. 51-52).
British Regime and after (1759- )
The British conquest of 1759 put Quebec on the road to a more market-driven economy. Britain itself was moving in the same direction by advocating free trade and rejecting mercantilism. On the local level, the conquest weakened groups that previously had State backing, thereby freeing up room for merchants, petty traders, self-employed artisans, and other entrepreneurs who could navigate in the new economic environment.
A gulf developed between the landed gentry, who thought of society in terms of absolutism, feudalism, bureaucracy, birth, and tradition, and the middle class [bourgeoisie] who now intended to redefine society in terms of its values. This was perhaps one of the most important consequences of the conquest. The bureaucracy as well as the landed gentry and the military elite saw their social role challenged by a middle class that demanded its autonomy and that intended to exercise a social influence in proportion to its economic dynamism (Ouellet 1966, p. 96).
The ranks of the growing middle class were filled by British and American immigrants in western and central Quebec, particularly in the Ottawa valley, Montreal, Trois-Rivières, Quebec City, and the Eastern Townships. A similar situation prevailed on the southern and eastern shores of the Gaspé Peninsula.
British and American immigrants were much scarcer in the rest of eastern Quebec, i.e., the Charlevoix, Saguenay, and Lac Saint-Jean regions on the north shore of the St. Lawrence and the Beauce and Bas Saint-Laurent regions on the south shore. Since that territory lay farther from the American border and lacked major ports, it was settled overwhelmingly by local people of French descent. Nonetheless, its built environment of roads, bridges, and other physical structures arose almost entirely during the British Regime. Social structures were likewise less influenced by the French Regime. The seigneurial system lasted only a few decades in Bas Saint-Laurent, versus nearly two centuries farther upriver (Fortin and Lechasseur 1993, p. 311).
The absence of English-speaking immigrants was striking to Alexis de Tocqueville when he passed through Bas Saint-Laurent in 1831:
In this portion of Canada, one does not hear English at all. The population is only French, and yet when one encounters an inn, or a merchant, the sign is in English (De Tocqueville 2003, p. 185).
With little competition from British or American merchants, an enviable niche opened up for French Canadians with the right abilities. In the Saguenay region, during the nineteenth century:
Success in trade was never easy because of the competition, the fragility of the markets, and the instability of business conditions. The ablest managed to live or survive. Others, the greatest number, closed shop after a few years. Only those possessing exceptional qualities would make a fortune (Lapointe 1996, p. 3).
Likewise in the Beauce region, “out of ten merchants who remained more than ten years in business, only four or five succeeded” (Courville et al. 2003, p. 257).
Success required special talents. This point is made in a biography of John Guay (1828-1880), a leading French Canadian merchant of the Saguenay region:
Improvising one’s way into becoming a merchant is not possible for anyone who so wishes. It takes talent and of course capital. Spontaneous generation was very uncommon in 19th-century Quebec, indeed nonexistent in John Guay’s case. The family environment in which he grew up predisposed him to develop an interest and also aptitudes for the businesses of trade, forestry, and farming. His successful career henceforth proved that a French Canadian merchant could ably penetrate the world of business; a world where, let us remember, English Canadians controlled most of the commercial and industrial activities (Lapointe 1996, p. 126).
How did French Canadians penetrate the world of business? John Guay’s father built bridges, wharfs, and sawmills on contract before becoming a merchant (Lapointe 1996, pp. 18-24). In the Beauce region, people went into business as innkeepers, as tavern operators, or as farmers who traded in livestock or grain (Bélanger et al. 1990, p. 62, Courville et al. 2003, pp. 261-262). Often, farm work would never be fully given up. This may be why so many French Canadian merchants of the nineteenth century failed to identify themselves as such to census takers (Courville et al. 2003, pp. 261-262). It may also be that the title of marchand or commerçant was viewed as somewhat disreputable.
To become a full-fledged merchant, the preconditions seem to have been familiarity with cash transactions and frequent negotiation of agreements on a case-by-case basis. A third one was a certain outlook on life. This precondition has been discussed by the historical economist Gregory Clark with respect to late medieval England. As England became a settled society, with the State imposing a monopoly on violence, successful individuals were those who could settle disputes amiably and profit from current actions further into the future—in short, those who had middle-class values of thrift, foresight, self-control, and sobriety (Clark 2007).
Expansion of the market economy and the middle class
Such individuals were initially a small minority in England. Their descendants, however, grew in number and replaced the lower classes through downward mobility, eventually accounting for most of the population by the 1800s. Their values came to dominate English society and laid the moral, cultural, and behavioral basis of the Industrial Revolution (Clark 2007; Clark 2009a; Clark 2009b).
That process ended with the Industrial Revolution. Previously, production had taken place in family-run cottage industries whose owners, if successful, expanded their workforces by having bigger families (Seccombe 1992, pp. 182-183, 205-206). Now, production was in factories whose owners simply hired as many workers as they wished. Industrialists no longer translated their economic success into reproductive success. Henry Ford, for instance, had only one child.
In Quebec, the family remained the prevailing unit of production well into the twentieth century. This was especially the case with farms and small businesses that dealt directly with the market economy while keeping the actual production in a pre-market economy of unpaid family labor. There was thus a strong incentive to have children. In Quebec City, at the turn of the twentieth century, the fertility rate was higher among French Canadians who worked for themselves at home than among those who worked for an employer at another location. A home-based shoemaker could bring his wife and children into different stages of production, i.e., cutting the hides, dyeing, sewing, fitting pieces together, etc. Factory employees could not count on help from family members (Marcoux et al. 2006, pp. 73-85; Marcoux 2009, pp. 107-120).
Merchants, too, used child labor. There was thus a positive feedback between family size and income. The merchant John Guay had ten children who lived to adulthood, twice the average of French Canadians of his time (Lapointe 1996, p. 110).
Whatever the occupation, what mattered was not so much your occupation per se as your access to the market economy, which could vary considerably. Farming, for instance, ranged from subsistence agriculture to market gardening. If you could exploit the possibilities of the market economy, you could earn more money and support more children, who in turn could marry earlier and have larger families of their own. More money also meant less mortality, especially infant mortality—a major curb on reproductive success until the twentieth century.
That factor might explain why fertility correlated positively with literacy in all occupations of the Saguenay region throughout the nineteenth century and long after. Literate individuals may have gained more resources for family formation, being better able to navigate in the market economy and needing less supervision by third parties (employer, manager, custodian, etc.). The literacy-fertility correlation would not become negative until 1946-1955 among farmers and 1931-1935 in other occupations, a reversal that came much later to Quebec than elsewhere apparently because of the Catholic Church’s hostility to contraception (Bouchard and Roy 1991).
The growing number of market-oriented individuals—in short, the middle class—created a distinct cultural environment with its own norms. To succeed in that environment, you had to adapt, just as humans have had to adapt to different climates, landscapes, and food sources.
Cultural evolution thus paved the way for biological evolution. This process, called Baldwinian selection, can be broken down into three stages:
Individuals behave in a certain way through conscious effort, within an envelope of possible phenotypes allowed by the genotype.
Such behavior creates a new cultural environment, which in turn selects for a genotype that more easily produces the desired behavior. A heritable predisposition increasingly takes over from conscious effort.
There is thus a shift toward a new mean genotype and a new envelope of possible phenotypes.
The above gene-culture co-evolution may explain the high rates of Tay-Sachs and other sphingolipid storage disorders in eastern Quebec. Such disorders may be only the tip of the iceberg, i.e., the most harmful outcomes among a much larger number of benign outcomes. We know less about the latter because there is less interest in genetic traits that cause no harm.
Have French Canadians been shaped by gene-culture co-evolution? The possibility is intriguing but raises several questions.
Was there enough time?
One question is the length of time. How could natural selection have produced significant genetic change over a span of two and a half centuries? That is a mere ten generations. Yet the time span could not have been much longer. Given that the two Tay-Sachs mutations are absent in France and uncommon over most of Quebec, both alleles must have reached their current high prevalence once French Canadians had already settled eastern Quebec, a process that took place largely during the British Regime.
If the Tay-Sachs heterozygote frequency had been 0.3% among French Canadians at the time of the conquest, ten generations could have been enough to bring it up to the current level of 7.6% in Rimouski if we assume a 25-30% fitness advantage. In addition, there may have been selection effects from the mass out-migration of the late nineteenth century, when many French Canadians left the area for factory work in New England. The emigrants tended to be landless farmers, rather than merchants, and may have been less likely to carry the Tay-Sachs allele.
Such rapid evolution seems to have been common in our species. Natural selection has altered at least 7% of the human genome over the last 40 thousand years, with most of the change happening since farming emerged less than ten thousand years ago (Hawks et al. 2007). That rapid evolution seems to have been driven by adaptation to a wide range of new cultural environments defined by technology, social structure, and rules of behavior.
Rapid evolution has been shown with respect to fertility among French Canadians, specifically those inhabiting the island of Île aux Coudres in the St. Lawrence. Its settlers came from a land-poor environment where young people postponed marriage until their parents handed over the farm. The age of marriage was much lower in New France because farmland was much more plentiful. Also lower was the mean age of first reproduction (AFR). From 1800 to 1940, AFR fell by four years, not through a lowering of the mean age of marriage but rather through a shortening of the mean interval between marriage and first birth. The ultimate cause could not have been a change in nutrition. Nor could it have been some kind of cultural lag, since AFR fell at a constant rate during that time. The likeliest explanation is a gradual shift in the gene pool toward highly fertile couples who could better exploit the opportunities for early family formation (Milot et al. 2011).
The Beauce region
The Beauce region stretches southeast of Quebec City and covers the Chaudière valley up to the American border. Like the rest of eastern Quebec, it has had relatively little settlement by English-speakers and has thus developed its own middle class, so much so that Beaucerons are stereotyped as business-minded go-getters—the “Yankees” of Quebec. Yet the region has low rates of sphingolipid storage disorders, like Tay-Sachs.
Settlers arrived earlier in the Beauce region than elsewhere in eastern Quebec. They also seem to have been less homogeneous, coming from a wider range of regions in France and including discharged German mercenaries (Ferron and Cliché 1982, pp. 3-4,123-124). This larger and more diverse gene pool may have supplied a greater number of suitable individuals for the niches that opened up after the conquest, as Quebec moved from a semi-feudal society to a market-driven one. Natural selection had more leeway to favor alleles with fewer harmful side effects.
Tay-Sachs elsewhere in North America
A high prevalence of Tay-Sachs has been reported from three other groups in North America: the Cajuns of Louisiana; a Pennsylvania Dutch community; and people of Irish origin (Branda et al. 2004; Kelly et al. 1975; McDowell et al. 1992; Mules et al. 1992). In the second group, the cause may be a founder effect, since Tay-Sachs occurs in several related families who form 3% of the population of two townships (Kelly et al. 1975). On the other hand, two separate alleles are responsible, despite the small size of this semi-isolate (Mules et al. 1992). A founder effect less easily explains Tay-Sachs among the Cajuns and the Irish, who have multiple Tay-Sachs alleles (Branda et al. 2004; McDowell et al. 1992).
The above three groups may have followed the same sort of gene-culture coevolution. Like the French Canadians of eastern Quebec, they made the transition to a market economy later and faster than the English did. It may be that their market-savvy individuals tended to have a less optimal mix of alleles, including some that are detrimental in a homozygous state.
Why are vitamin D deficiency disorders also prevalent?
Finally, eastern Quebec has a higher prevalence of two apparently non-neurological disorders: pseudo-vitamin D-deficiency rickets and cystinosis. Both lead to rickets through an inability to synthesize or process enough vitamin D. The same symptom is also associated with a third eastern Quebec disorder: Tyrosinemia type I. By way of comparison, rickets is not caused by any of the top ten genetic disorders of the United Kingdom.
Vitamin D deficiency does not seem to affect adult cognition (Annweiler et al. 2009; Maddock et al. 2017). But there may be early developmental effects. When rat fetuses are deprived of vitamin D, the newborn pups have larger brain volumes and show more cell proliferation in their brains. This is consistent with the anti-proliferative effect of this vitamin on body tissues. Prenatal vitamin D deficiency thus seems to increase the rate of neuronal proliferation while decreasing the rate of neuronal cell death (Eyles et al. 2003). If prenatal vitamin D deficiency affects humans similarly, the result may be improved cognitive ability, albeit at a high cost for homozygous individuals.
Avenues for future research
In recent years, researchers have identified alleles associated with educational attainment, thus creating a means to measure the genetic component of cognitive ability (Lee et al. 2018). Because the genetic history of French Canadians is well documented, thanks to the records of births, deaths, and marriages kept by the Catholic Church, it should be possible to chart the cognitive evolution of French Canadians over time and space, particularly with respect to eastern Quebec.
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This is a revised version of an earlier paper:
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Prenatal vitamin D deficiency is associated with worse cognitive outcomes.