Given that the probability of conception per coital act is estimated to be about. It would be very difficult for a man to have more than 30 extra-pair copulation partners in a year, especially in the ancestral environment, where our ancestors lived in a small band of about genetically related individuals men, women, and children. So should more attractive parents have more sons instead? SHARE Physically more attractive parents are more likely to have daughters than physically less attractive parents, both in the United States and in the United Kingdom. It would therefore be nearly impossible for a physically attractive man to match the reproductive success of a physically attractive woman through only short-term mating. Physical attractiveness of the NCDS respondents is measured at age 7 by their teachers, who choose up to three adjectives from a highly eclectic list of five to describe the children physically: Can handsome sons achieve higher reproductive success than beautiful daughters? Hence physical attractiveness is more beneficial to girls than to boys. It appears that natural selection does help individual genes to spread, by subtly biasing the offspring sex ratio so that beautiful people, who can benefit from having a daughter, do indeed have slightly more daughters than ugly people, who cannot so benefit. Men prefer beautiful women for both long-term and short-term mating, whereas women prefer handsome men only for short-term mating casual affairs and one-night stands , not for long-term mating, for which other traits, such as wealth and status, become more important. Thus the gTWH predicts that physically more attractive parents are more likely to have daughters than physically less attractive parents, and, as I explain in the earlier post , the analysis of the National Longitudinal Study of Adolescent Health Add Health confirms the prediction. In an earlier post , I explain that the logic of the generalized Trivers-Willard hypothesis gTWH leads to the prediction that physically more attractive parents are more likely to have daughters than physically less attractive parents. Multiple binary logistic regression analysis shows that being physically attractive statistically significantly increases the odds of having a daughter as the first child, net of sex, age at first child, education , social class, earnings, height, and weight.