Tuesday, August 21, 2007

Trivers-Willard tested

Trivers–Willard at birth and one year: evidence from US natality data 1983–2001

Douglas Almond, Lena Edlund

Proceedings of the Royal Society, B Volume 274, Number 1624 / October 07, 2007
Abstract: Trivers & Willard (TW) hypothesized that evolution would favour deviations from the population sex ratio in response to parental condition: parents in good condition would have more sons and parents in poor condition would have more daughters. We analyse the universe of US linked births and infant deaths to white mothers 1983–2001, covering 48 million births and 310000 deaths. We find that (i) married, better educated and younger mothers bore more sons and (ii) infant deaths were more male if the mother was unmarried and young. Our findings highlight the potential role of offspring sex ratio as an indicator of maternal status, and the role of infant mortality in shaping a TW pattern in the breeding population.

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