Infertility and same-sex attraction in women.

A polygyny hypothesis of female sexual fluidity proposes that women may have been evolutionarily selected to be sexually fluid, in order to have occasional sex with their cowives in polygynous marriage to reduce tension and conflict inherent in such marriage, while at the same time reproducing children with their husbands. Among others, the hypothesis predicts that women who are biologically (but not surgically) infertile would experience greater same-sex attraction. Biological infertility stems from natural, evolutionarily familiar causes such as menopause, whereas surgical infertility stems from artificial, evolutionarily novel causes such as tubal ligation or hysterectomy. Consistent with the prediction, the analyses of the National Survey of Family Growth data showed that biological infertility, but not surgical infertility, was significantly associated with same-sex self-identified labels, behavior and sexual attraction in women. Biological infertility nearly doubled the odds of women having engaged in same-sex behavior and the number of same-sex partners in the last 12 months and nearly tripled the number of same-sex partners in life. In sharp contrast, biological infertility was not associated (and surgical infertility was significantly negatively associated) with same-sex attraction in men.

Why do very unattractive workers earn so much?

Kanazawa and Still (2018) showed that very unattractive workers earned more than unattractive workers, sometimes more than average-looking or attractive workers, because they had higher levels of intelligence and education, but they did not explain why very unattractive workers had higher intelligence and education. There are both theoretical and empirical reasons to expect that some intelligent men may prefer to marry very unattractive women. The analysis of the National Longitudinal Study of Adolescent Health (Add Health) shows that very unattractive women were significantly more likely to be married at Age 29 than unattractive or average-looking women, and their spouses or partners earned significantly more than those of unattractive or average-looking women. If intelligent men have historically preferred to marry very unattractive women generation after generation, then, because both general intelligence and physical attractiveness are highly heritable, this can explain why very unattractive workers are more intelligent and achieve higher education, thereby earning more. It can also explain why the positive correlation between intelligence and physical attractiveness is not larger despite assortative mating of intelligent men of higher status and physically attractive women over many generations.