Social stratification, such that sons inherit their father’s rank and the attractive daughters of low-ranking parents marry upwards, may be sufficiently widespread and longstanding to have had selective consequences in human evolution. We present evidence from families in the North West of England that a correlate of rank, that is, the difference in age between husbands and wives ( D a ), predicts the sex of first-born children and the asymmetry of daughters. High D a couples, i.e., where husbands are older than wives, tend to have first-born sons, asymmetric daughters, and low waist:hip ratios in the adult females. Low D a couples, i.e., where wives are older than husbands, tend to have first-born daughters, symmetric daughters, and adult females with high waist:hip ratios. When D a is at the modal difference the sex ratio of first borns is close to 1:1, and family size and symmetry of wives are higher than at the extremes of D a . It is suggested that before their first full-term pregnancy women in high D a unions invest more in male than female embryos, resulting in an overall loss of the latter, while women in negative D a unions invest more in female than male embryos, resulting in selective loss of males and the production of symmetric female infants. First-born sons of high D a couples will inherit their father’s rank and, as symmetry is related to attractiveness in humans, the symmetric daughters of low D a couples may marry upwards.