Well, after all, it explains everything, right. So here’s a claim that natural selection explains the lowering of the age of first births to women in Quebec during a 140 year period. (In PNAS , October, 2011).
Before you read the abstract below, here is a potted history of Quebec: At the close of the Seven Years’ War, France (the loser) had to decide between giving Britain (the winner) Quebec or Louisiana. The French king preferred the jazz and jambalaya (so to speak) to the “few thousand acres of snow” up north. So it was worse, you see than Quebec losing the war. That can be romantic. Rather, the Quebecois, so consciously French it hurt, were actually dumped by France.
The British did not interfere with their religion (Catholic), their language (French), their culture (les habitants), or – within reason – their laws (civil code). But the Quebecois realized that they were at risk of becoming an endangered minority anyway, due to huge numbers of non-French-speaking immigrants streaming into Canada, who usually learned English rather than French. Up until about the 1960s, they were devout Catholics, and by a confluence of choices and events, they simply had more children than others. Some called it “revenge of the cradle.” Of course, bigger families meant earlier marriage for women.
Now that Catholicism has collapsed in Quebec as a serious cultural force, the birthrate is very low, even for Canada, and the language and culture are in danger from that cause, despite sometimes extreme legislation to protect them, including outright paying people to have kids. In the light of this history, why would anyone be looking for a role that “natural selection” played in early marriage ages for Quebecois women, apart from the need to demonstrate Darwinism?
Evidence for evolution in response to natural selection in a contemporary human population
Emmanuel Milota,1, Francine M. Mayera, Daniel H. Nusseyb, Mireille Boisverta, Fanie Pelletierc, and Denis Réalea
It is often claimed that modern humans have stopped evolving because cultural and technological advancements have annihilated natural selection. In contrast, recent studies show that selection can be strong in contemporary populations. However, detecting a response to selection is particularly challenging; previous evidence from wild animals has been criticized for both applying anticonservative statistical tests and failing to consider random genetic drift. Here we study life-history variation in an insular preindustrial French-Canadian population and apply a recently pro posed conservative approach to testing microevolutionary responses to selection. As reported for other such societies, natural selection favored an earlier age at first reproduction (AFR) among women. AFR was also highly heritable and genetically correlated to fitness, predicting a microevolutionary change toward earlier reproduction. In agreement with this prediction, AFR declined from about 26–22 y over a 140-y period. Crucially, we uncovered a substantial change in the breeding values for this trait, indicating that the change in AFR largely occurred at the genetic level. Moreover, the genetic trend was higher than expected under the effect of random genetic drift alone. Our results show that microevolution can be detectable over relatively few generations in humans and underscore the need for studies of human demography and reproductive ecology to consider the role of evolutionary processes.
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