Let the good times roll?

A new paper in PLOS Genetics claims to have found a higher frequency of deleterious mutations in the exome of French Canadians than in the French.  French Canada was founded by a small population (effective Ne about 2900),  but I think that bottleneck has little to do with this increased load. If this result is correct, I see only two possibilities: either  the original settlers already had higher-than-average load, or they were subject to relaxed purifying selection.

We all know that purifying selection is considerably weaker nowadays in the decent parts of the world,  what with chlorinated water  and doctors that cure more often than they kill.  But when you think about it, some recent fast-expanding settler populations must also have been subject to weaker than typical purifying selection, just because they had plenty to eat and relatively low disease incidence.  In premodern Europe, maybe half of the kids lived to grow up, and the numbers for hunter-gatherers are in the same ball park.  But in colonial  New England, it was more like 90%, and I would guess that the numbers were similar in Quebec.  Cold weather helped.  Selection wasn’t as relaxed as it is today, but survival was a lot easier than it had been in typically Malthusian human societies  – and in some cases, the process went on longer than modern medicine has existed (only 3 or 4 generations).  It’s not high paternal age: that was Euro-typical, around 34.

The Frogs have had it rougher than the Canucks.

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19 Responses to Let the good times roll?

  1. So, deleterious environments save us from deleterious mutations, in the long run at least?

    • gcochran9 says:

      Yes, as long as they don’t kill off the population. And of course there are different flavors of selection: one environment might test resistance to famine, another surviving interhuman conflict, while in another resistance to malaria might be the ticket.

      In addition, it helps if the population is big enough to efficiently eliminate slightly deleterious mutations and generate plenty of advantageous ones.

  2. Anonymous says:

    It would be interesting to verify this phenomenon in comparable populations that have grown exponentially such as New England Puritans and say, New Zealanders. However, selection did not relax on Europe’s Ashkenazi population, the Jewish cemeteries are full of children, specially from 1918 (the flu epidemy).

  3. dave chamberlin says:

    I’ve wondered why we are so programed to be highly attracted to a highly symmetrical face, we normally don’t call it it that we call it handsome or beautiful. Maybe this symmetry is the best window we have into the genes of a potentially good mate with fewer than average mutations. Certainly the funny looking kids that are mentally handicapped are an example of the opposite. A slightly off topic question. What do you make of the reports of rapidly decreasing sperm counts in many parts of the world. If these reports are true what is their cause? It wouldn’t surprise me if nature has built in ways of dealing with increased mutational loads besides spontaneous abortion or death of a high percentage of children. Is their a correlation between lower sperm count and higher mutational load.

  4. Patrick Boyle says:

    My second wife was French Canadian. I knew it had to have been something like that.

  5. Matt says:

    French Canadians are r (selected for high reproductive rates in low crowding niches, suited for quick dispersal).

    French are K (selected for high individual quality in crowded niches, near carrying capacity).

    Perhaps Ontarians have suspected this.

    • Michel says:

      No, PISA record of Quebec are much higher than those of France wallonie and even french spinking Swiss. Human relation are much more violent in france than in Quebec. Matt you are so typical of the racist attitude of Anglos-Canadians toward Quebec. Stop reading the haters of the National Post.

      • reiner Tor says:

        Just an observation. PISA record is a good argument. Accusing someone of racism and hate is a bad argument, it actually inclines one to ignore even the good arguments. (BTW is French-Canadians were r-selected, then probably so were Anglo-Canadians, who had an even bigger country for themselves.)

      • Miguel says:

        There is no such thing as an “anglo” Canadian, other than that they speak English as a mother tongue. Stop reading the haters of the Journal de Montreal.

  6. charleskiddell says:

    Huge family size, ‘‘la revanche des berceaux,” or “the revenge of the cradles,’’ presumably contributed. Céline Dion is one of 14 children, and a Catholic French Canadian woman having more than 20 children was not unheard of before the “quiet revolution” of the sixties.

    In 45 years in Quebec I’ve never heard anyone refer to French Canadians as Frogs. I’ve seen it in print once or twice. No, the pejorative is “Pepsi,” or “Pepper,” which I have heard used, humorously and not unkindly. Supposedly this was because Pepsi was the discount cola a long while back and the anglos drank Coke while the francophones drank Pepsi. I’ve been called a Tête Carrée or square head by more than one French Canadian.

    • gcochran9 says:

      No, it is the fraction that survives that determines the strength of selection.

      • Richard Sharpe says:

        I had failed to appreciate this important point until now.

      • charleskiddell says:

        I am tempted to pursue this line of thinking, but I am afraid I’ll get stomped as a newbie commenting on what I only dimly understand. But does not farmers fathering children well into middle age combine with relaxed purifying selection not to arrive at the increased load, but to accelerate the process? Without it the load would not, or not yet be as high as is observed?

        For relaxed purifying selection: in Quebec one had the social safety net of the church to get one through life’s mini-disasters. There’s a steeple in every village. And one had a largely empty land, still empty even now. As late as the sixties there were masses of unskilled and semi-skilled jobs as lumberjacks or farm hands in the rural region I live in (I have see a half-dozen log drives, now a thing of the past), and salmon fishing and mining jobs farther north. There was social and church pressure on a mere landless farmhand, 20th child of a stereotypical family, to marry, and with an inexpensive, or free housing plot and plentiful cheap lumber he could afford to.

        Life’s more serious problems included the boredom of endless winter, some scurvy, and raising enough money to buy a cast iron stove when marrying. Firewood not an issue anywhere in Quebec, even now. One can cut a winter’s supply in two days with unpowered hand tools by culling still standing dead trees in the endless forests. And there was no tradition of dying in foreign wars.

        I think of rural French Canadians as tough people, but they mostly struggled with the cold, lack of sun, and a bland diet, nothing like what I have seen in India or Africa, or Chicago …

        Okay. Stomp.

  7. athEIst says:

    Many years ago a French-Canadian couple were contestants on “I’ve got a Secret”. Both from families in which twins and triplets were common, their secret was they had 36 children!

  8. charleskiddell says:

    I can’t resist. Log driving: http://m.youtube.com/watch?v=upsZZ2s3xv8

  9. I can’t speak for Quebec, but in Manchester NH French-Canadians were called Frogs. Usually by each other. I don’t hear it any more. As national insults go, that one is about as devastating as “limeys” or “krauts.”

    There were more in France who lived well, but a higher percentage in Quebec (NB,NS, NFLD) that simply lived. Until 1900 at least, the poor in France were not merely hungry, but occasionally starving.

    Michel. Touchy much? Nothing was insulting in Matt’s comment. Let me make up for that. I thought Canada was a bilingual country now. Why are you unable to write English?

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