Evolutionary biologist Virpi Lummaa has discovered that Finnish women in previous generations suffered a variety of adverse effects when they bore and raised sons.
Among the impacts: a reduced lifespan, greater vulnerability to disease due to higher testosterone exposure during pregnancy, daughters who were less likely to reproduce, and smaller subsequent children. Additionally, having a grandmother around was more helpful than having a grandfather (probably because she helped with childrearing while he just sat around and ate food).
While modern reproductive technologies have mitigated a lot of the effects seen in pre-industrial families, it is still intriguing to consider these impacts in light of the strong cultural bias favoring the bearing of sons. Perhaps it is a type of "peacock effect", whereby the individuals who still thrive in the face of handicapping or indulging in risky behavior are considered stronger and more robust. Or, as my mother asserts, the value balances out an apparent difference in general robustness and health between male and female young, where males often are weaker to start with.
Of course, having too many sons can be evolutionarily disadvantageous too...
Friday, February 15, 2008
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3 comments:
As someone with a Y-chromosome, I'll accept the men suck argument ... still, i wouldn't say that the statistical correlation of being gay and having several older brothers demonstrates that "having too many sons can be evolutionarily disadvantageous". There are plenty of cutting-edge biologists who believe just the opposite, such as Bruce Bagemihl. He uses animal studies (yes Virginia, there are many species that exhibit gay behavior ... and not just penguins) to argue that non-reproductive, same-sex sexual relationships can be advantageous from an evolutionary perspective.
There a nice little post over at http://scienceblogs.com/dispatches/2008/02/gay_penguins_hide_the_children.php?utm_source=mostactive&utm_medium=linkabout the book "And Tango makes Three," which retells the true story of two male penguins who took turns sitting on an orphaned egg at the Central Park Zoo.
I actually completely agree with both of you that homosexual orientation can actually present benefits, evolutionarily speaking. That remark had a hefty dose of dry sarcasm mixed in with the irony. :)
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