what your kids' gender says about you

Constraints in the Evolution of Sex Ratio Adjustment

When the relative fitness of male and female offspring varies with environmental conditions, evolutionary theory predicts that parents should adjust the sex of their offspring accordingly.
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Natural Selection of Parental Ability to Vary the Sex Ratio of Offspring

Theory and data suggest that a male in good condition at the end of the period of parental investment is expected to outreproduce a sister in similar condition, while she is expected to outreproduce him if both are in poor condition. Accordingly, natural selection should favor parental ability to adjust the sex ratio of offspring produced according to parental ability to invest. Data from mammals support the model: As maternal condition declines, the adult female tends to produce a lower ratio of males to females.

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Should attractive males have more sons?

Exogenous shocks to the human sex ratio: the case of September 11, 2001 in New York City.
R. Catalano, T. Bruckner, A.R. Marks, and B. Eskenazi (2006)

some of the some authors - Sex ratios in California following the terrorist attacks of September 11, 2001 (abstract)