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. Obviously the opportunity for large family size are rare in such resource-limited situations, and costs incurred as a consequence of a high-fertility phenotype detract from fitness.
The same must be the case for old American types whose ancestors – Puritans, for example – arrived early and went through a number of high-fertility generations in colonial days. It’s likely the case for the Mormons, who are largely descended from New Englanders. I’ve heard of odd allele frequencies in CEU (involving FSH) that may relate to this.
Something similar must be true of the Boers as well.
I would guess that a similar process operated among the first Amerindians that managed to get past the ice in North America. America south of the glaciers would have been a piece of cake for anyone tough enough to make a living as a hunter in Beringia – lush beyond belief, animals with no experience of humans. Truly, the Happy Hunting Ground. Selection would have favored high reproduction rates. That process would have reversed when the population saturated. Of course that probably followed a real crash, when they wiped out the megafauna. You might see signs of that old high-reproduction phase in ancient DNA.
The Amish must have experienced simultaneous selection for high reproductive rate and an unusual personality type – individuals that prefer the Amish way of life to that of outsiders.
Amish in Lancaster County, Ashkenazi Jews as a merchant/scribe caste, Tibetans & altitude, pastoralists and lactase tolerance, hunter-gatherers -> peasants : every significant, lasting ecological change creates an altered human population, different in both body and mind.
West Hunter 
One would think that there has always been selection for the inclination to have as many children as possible and that this selection has been strongest where the culture was not explicitly pronatalist as it was among Jews and Puritans.
Conversely, in pronatalist communities there would be relaxation of selection for genetic inclination to have many children. So when the pronatalist culture fades out after many generations the individuals descended from a pronatalist community have little genetic inclination to have big families or any families at all.
“Obviously the opportunity for large family size are rare in such resource-limited situations, and costs incurred as a consequence of a high-fertility phenotype detract from fitness.”
French Canadian Roots, Inducements to produce more babies. (scroll down page)
You’re wrong. The question is not how many babies are possible, but how many are practical. Past a certain point, birds that lay more eggs have fewer surviving offspring. Same for people, if resources are limited. As for incentives for extra children from the French authorities – they operated for six years. The population expansion ran for more than 300 years. Let’s be real. It happened because there was a lot of suitable near-empty land, the same reason that colonial farmers in the British American colonies averaged 9 surviving offspring for several generations.
Re clutch size, Greg, I think folks have searched long and hard for a Lack effect in humans without finding any. Maybe humans know better than to push their fertility that far.
Closest I have seen is what looks like adaptation of pathogens to specific families. A kid gets sick, then his sib gets it and gets even sicker, and in big families by the time the disease got to sib 5 or so they died. This was from historical demographic studies in the Connecticut valley.
HCH
It would be nice if the post included a link to the work of these Canadian Researchers.
“I think folks have searched long and hard for a Lack effect in humans without finding any”
Culture? Priests wandering around preaching “go forth and multiply!” then when the land fills up they put the brakes on by preaching against fornication.
“birds that lay more eggs have fewer surviving offspring. Same for people, if resources are limited”
As I understand it you’re saying that whether a human culture is explicitly pronatalist (like Calvinisn) or not it has no effect on natural selection for the psychological inclination to have many children. I was floating the idea that the selection in a Calvist culture like the Amish would be for an inclination to conform to the rules (thereby having many children) and straightforward selection for the inclination to have the maximum number of children would be relaxed.
In addition to being explicitly pronatalist Calvinisn was a highly effective culture for farmers ( still is to the extent that they were banned from buying land in Dakota not so long ago) due to low consumption of luxuries and cooperation within the group (eg Amish raising barn). Might that have aided the Puritans to expand ?
Got a bit mixed up there. Kevin MacDonald on the Hutterites and Puritans .
“400 Hutterites moved to the US in 1874 and grew to over 20.000 in the following hundred years solely as a result of high fertility. Birth rates averaged 4% an year implying around 10 children per woman, which is close to the theoretical maximum. Hutterite fertility is commonly used as a yardstick by demographers”.
While I have to allow that where there was good land for the taking, (Especially large areas of contiguous settlement such as there wasn’t in Europe, Euro Amish died out) massive expansion was possible. However, in the kind of geometrical expansion of the population demonstrated by the Hutterites, culture was surely very important.
In the 40s and 50s Hutterite land purchases were limited by law in Dakota and Alberta because the other farmers couldn’t compete with their low personal consumption. The French Canadians are not noted for their abstemiousness as far as I know so I think, given the same circumstances, a people with a pronatalist culture would have expanded faster than they did.
“9 surviving offspring for several generations.” Hmm, MacDonald says that completed marriages in Walden Mass in the 1730’s had 9.7 children. I think that could be put down to Puritan culture in that time and place as much as the availability of land . There could be an economic motive for having big families in colonial times but I don’t know how the extra children would have benefited a farmer. Were children useful as labor ?
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“Culture? Priests wandering around preaching “go forth and multiply!” then when the land fills up they put the brakes on by preaching against fornication.”
Just to add. When the priests are preaching go forth and multiply that applies a selection pressure (proportional to religiosity) for those traits conducive to enthusiastic fornication. If/when they hit the brakes that applies selection pressure for the opposite traits.
It’s a shame we can’t do a google search for the number of times American preachers used the phrase “go forth and multiply” or the word “fornication” in sermons in 1700 compared to 1840.
I read the NY times article here: http://www.nytimes.com/2011/10/04/science/04evolve.html?_r=1&adxnnl=1&adxnnlx=1317954465-ufmXoOAv2h4l8aVRf9V+EA
I’m really confused by this study. Many traits, cultural and genetic- the genetic ones ranging from personality to fertility which can intersect with so much else- contribute to age at which a woman has her first child. Traits from the men contribute as well. How were they able to pinpoint any particular genes and find this was selected? And just 4 years over a 140 year period was due to natural selection?
Women have children at ages that are different from the ancestors all the time, and in periods much shorter than 140 years of difference and at age differences much greater than 4 years- how often is this natural selection?
A “merchant/scribe” caste position might select for what we could call a ‘middle-class’ personality within the ‘Big 5’ personality space, as well as higher IQ. Are there any studies which look at the specific scoring of the Ashkenazi community on personality traits?
@Nigel,
IIRC, AJ’s display higher Extroversion and Openness to Experience than average.
Higher Openness to Experience was the only one of the Big 5 positively correlated with higher IQ.
Thanks 344444444r, the NYT article is very good, wish I had read it before commenting.
Stearns mentioned the gist of it on the BBC radio 4 ‘s In Our Own Image – Evolving Humanity several weeks ago.
Link to the actual PNAS article:
http://www.pnas.org/content/early/2011/09/28/1104210108.abstract?sid=95497560-b043-4ba4-bca5-6592c1cf584c
GC: “every significant, lasting ecological change creates an altered human population, different in both body and mind.”
“Problems with Mixed-Race Families, Marriages and Relationships”
http://sociobiologicalmusings.blogspot.com/2011/10/problems-with-mixed-race-marriages-and.html
May hybrid vigour have something to do with new world population expansion? Just wondering? 😉
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