3.3 Male mate preferences

Male reproductive success was historically limited by sexual access to fertile females. Selection therefore favored male preferences attuned to cues of a partner's fertility and reproductive value — and, for long-term mates, to the problem of paternity certainty.

Cues to fertility

Because female fertility is strongly age-graded and not directly observable, men evolved preferences for observable cues that correlated with fertility: youthfulness, clear skin, lustrous hair, and features associated with health and estrogen. These are signals, not the trait itself — men did not evolve to read fertility directly but to track its visible correlates.

Reproductive value vs. current fertility

A subtle distinction matters. Current fertility is the probability of conceiving now; reproductive value is the expected future reproductive output. The two peak at slightly different ages. Men seeking short-term mates and men seeking long-term mates weight these differently, which helps explain age-preference patterns.

The paternity problem

Males face a problem females never do: paternity uncertainty. A woman is always certain her child is hers; a man, before modern testing, could not be. This asymmetry shaped male sexual psychology profoundly — including preferences for cues of fidelity in long-term mates and the particular form male jealousy takes, a topic we return to.

A grounding example

Studies of waist-to-hip ratio by Devendra Singh found that men across many cultures tend to rate a female waist-to-hip ratio around 0.7 as most attractive. This ratio is not arbitrary: it correlates with youth, health, hormonal profile, and the absence of current pregnancy — all cues to fertility. Even when overall body weight preferences vary across cultures, the preference for this proportion recurs, suggesting men evolved to track a reliable signal of reproductive potential rather than any single body size.