October 12, 2011
Natural Selection Sped Up French Canadian Reproduction
Greg Cochran points out new research showing that freed from the Malthusian Trap French Canadians underwent natural selection that selected for genes for earlier reproduction.
French Canadian researchers have shown that natural selection has noticeably sped up reproduction among the inhabitants of Île aux Coudres, an island in the St. Lawrence River – in less than 150 years. Between 1799 and 1940, the age at which women had their first child dropped from 26 to 22, and analysis shows this is due to genetic change.
This has to be the case for French Canada generally. There were about 5,000 permanent settlers, including 1600 women: they account for about 90% of the ancestry of the 7 million Francophones in Quebec (along with a substantial number in New England). During that rapid expansion, genes that favored fast reproduction surely increased in frequency. Today the French of Quebec must differ significantly (in those genes that influence this trait) from people in France, which has had relatively slow population growth. Slower reproduction must be favored – lead to greater fitness – in a more Malthusian society.
The Amish population is currently doubling at a 14 year rate. Any small population that can maintain a high rate of doubling will eventually become a very large population. If the very high fertility groups (ethnies?) in developed countries maintain their high fertility rates for the next couple hundred years they'll swamp the rest of the populations of these countries.
The power of natural selection makes me skeptical that industrialized countries will remain outside the Malthusian Trap.
the age of 22 is not a surprisingly early age of first child birth. If anything, it's surprisingly late age for a society without economic constraints on early marriage. If a male starts to do useful work around 13 and is basically an adult (if not necessarily a landowner) at 18, what is stopping a 17 year old female from marrying him and having children?
I don't feel like digging for statistics, but anecdotally it was well known in late Soviet Union that people married (and usually had at least one kid) around the time of completion of education, which would be around 18 for people without college (high school graduation at 16 and 2 years in the army) and around 22 for college grads. They were able to do so because of full employment (albeit at fairly low wage) and not particularly onerous (compared to modern America) divorce laws.
Unless of course you let your country get swamped with competitors, who aren't necessarily gifted with the sort of genetic traits the maintenance of your desired society requires...
I find it hard to believe that in 1799, when there was either none or very poor quality birth control, that the women reached 26 before getting pregnant, especially when you had a much smaller population of women than men, who were fighting over them.
Would it not more likely be due to poor health in the colonies than birth prevention?
British Canadians in the early 1900's used to be know as some of the most fertile in the empire, since modern birth controls thats changed everything.
Michael L and no,
You can't imagine your way back to what it was like then. You've got to read the details. A great place to start is A Farewell To Alms by Gregory Clark. Find out what fertility was like (at least in England) in the era of the Malthusian Trap. Find out how long marriage was delayed due to poverty. What's reported above is reasonable given the known background knowledge about Malthusian Trap fertility.
My Great Great Aunt: 23 children My Grandmother: 7 children My Mother: 3 children My Sister: 1 child
Obviously my great great Auntie had all the genes she needed for radpid reproduction, but despite this, the birth rate of my enormous family has plummeted over the last 100 years. Natural selection was overwhelmed by changes in the environment, both physical and social, that the genes found themselves in. Natural selection has quite a job ahead of it and faces a constantly shifting target as the environment changes.
But one thing I do predict is that babies will become nicer over time, as people who have a pleasent child will be more likely to have a second one.
So "analysis shows this is due to genetic change." This is big news, because last I heard we had very little idea which genes out of the thousands involved in reproduction actually allowed earlier menarche and potential pregnancy. There are plenty of well known environmental factors that delay or advance first pregnancy (e.g., cultural delayed marriage/sex, poor nutrition, availability of birth control/abortion, etc.). In the last couple of centuries average age of menarche (first period) had decreased several years, mostly due to improved nutrition, but since this was from the 15-16 year old range down to the 12-13 year old range it doesn't seem to impact much the described 26 to 22 year old first pregnancy.
This has all the markings of a statistical 'study' with some SWAGing tacked on.
I can easily imagine that lots of people in French working class in early 19th century could not afford having kids. Which ties into to the whole "French orphanage as a form infanticide" meme and the June Days revolt in 1848. But here we are talking about Canada with abundant land available for all that come. In such utopian conditions both 26 and 22 are too late of an age to marry and have kids. When you are young, employed and happy, you don't need special genes to get a girlfriend knocked up, marry her and live happily ever after.
Earlier menarche is not necessarily due to "improved" nutrition but more likely the exact opposite in modern westerners. Likewise the larger bodies of modern western peoples are not necessarily due to better health, though it is a common belief. Our food supply is really screwed up and people are addicted to crap that no doubt causes hormonal changes.
Regarding early menarche this Matt Stone said it the best: http://180degreehealth.blogspot.com/2007/11/leave-britney-alone.html
French orphanages for infanticide: I am guessing you are referring to John Boswell's book The Kindness of Strangers: The Abandonment of Children in Western Europe from Late Antiquity to the Renaissance. That was an eye-opener for me.
I'd like to see a comparison of French and English fertility as a function of age in the 18th and earlier centuries. Did the English do a better job of delaying fertility when poor? Did they abandon fewer children as a result?
Looking back at my previous comment, I wasn't very clear in explaining why I think natural selection will have little or no effect on birth rates in the modern world. By natural selection I mean differental reproduction resulting in a change in allele frequency - not cultural change. The Amish, apart from a few oddities resulting from inbreeding, are pretty much genetically identical to other groups of settlers that came to North America. It is not their genes but their culture that has resulted in their current high birth rate. One could argue that their culture will be so successful that the Amish will inherit the earth through reproductive success, but that's not natural selection, at least not as the word is used in biology.
It is possible to imagine ways that natural selection could operate in the modern world to increase birthrates, but each change is likely to be countered with a delibrate environmental change. For example, an genetic predisposition to latex allergies could be spreading through the population right now, but this is countered by improvements in allergy treatment and polyurethane condoms, not to mention the development of roboprostitutes. The inability to remember whether or not one has taken an oral contraceptive might be selected for, but is countered by smart phone reminder apps, changes in contraception, and genetic screening by parents who won't want their offspring to be that vague.