Fig. 6.

A strong positive relationship between male skew (Top frame) and sex differences in skew (Bottom frame), as a function of percent age-adjusted female polygyny in humans. Percent age-adjusted female polygyny is the predicted fraction of women married to men with more than one total wife by age 60 (see ref. 20, for details). The solid line plots the posterior mean regression, while the shaded area plots the 95% posterior credibility region. The black points give the data. Sample size: N = 19 human populations.