According to the Trivers-Willard Hypothesis, individuals possessing a trait which improves the reproductive success of males more than females will be more likely to give birth to male offspring than to female offspring. I came across a study that claims to support the hypothesis where the trait in question is promiscuity.
Our analyses of two large nationally representative samples, from the General Social Survey in 1994 and the National Longitudinal Study of Adolescent Health, confirm this prediction. Controlling for a large number of social demographic factors that might be expected independently to influence offspring sex ratios, unrestricted sociosexual orientation significantly increases the odds that the first child is a boy. One standard deviation increase in the unrestrictedness of sociosexual orientation increases the odds of having a son by 12-19%.
That seems like a large effect, if true. Chullo chuck: Barking Up The Wrong Tree.
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February 9, 2011 at 5:54 pm
SB
Did the study control for timing of intercourse to ovulation? Intercourse timed within a day of ovulation disproportionately results in a boy. Sexual promiscuity may be a proxy for frequency of intercourse, which in turn increases the chance that a couple will have sex close to ovulation.
February 9, 2011 at 11:50 pm
jeff
i didnt know that. no they did not control for that.
February 10, 2011 at 7:04 pm
Anonymous
But why control for that? The effect has to work through some channel if it’s true
February 10, 2011 at 10:10 pm
jeff
very good point. i wrote a new post on this.
February 10, 2011 at 10:10 pm
Consider The Equilibrium « Cheap Talk
[…] 10, 2011 in Uncategorized | Tags: evolution, game theory | by jeff Following up on the Trivers-Willard hypothesis. The evidence is apparently that promiscuity, a trait that confers more reproductive advantage on […]