Age at First Reproduction

Primates have later ages at first reproduction than other mammals of the same body size, and great apes have the latest of any primate except humans whose ages at first birth are generally 5 to 10 years later than the other great apes. Among hunter-gatherers teen-agers are often sexually active, but age at first birth averages around 19. Post-pubertal subfecundity occurs in both women and other primates. While the reasons for it are largely unknown, ovulatory cycles are usually irregular the first years immediately following menarche. The delay in age at first reproduction for men, as for other male primates, is associated with lower success for younger males in competition for mates. Humans are distinguished from other great apes in having cultural rules about both sex and marriage that also affect age at first reproduction. Men are usually older than women at first marriage and age at first reproduction is a few years later for men than women.