“Male Chimpanzees Prefer Mating With Old Females”, Martin N. Muller, Melissa Emery Thompson, Richard W. Wrangham2006-11-21 ()⁠:

Cross-cultural studies indicate that women’s sexual attractiveness generally peaks before motherhood and declines with age. Cues of female youth are thought to be attractive because humans maintain long-term pair bonds, making reproductive value (ie. future reproductive potential) particularly important to males. Menopause is believed to exaggerate this preference for youth by limiting women’s future fertility.

This theory predicts that in species lacking long-term pair bonds and menopause, males should not exhibit a preference for young mates. We tested this prediction by studying male preferences in our closest living relative, the chimpanzee (Pan troglodytes).

We show that despite their promiscuous mating system, chimpanzee males, like humans, prefer some females over others. However, in contrast to humans, chimpanzee males prefer older, not younger, females.

These data robustly discriminate patterns of male mate choice between humans and chimpanzees. Given that the human lineage evolved from a chimpanzee-like ancestor, they indicate that male preference for youth is a derived human feature, likely adapted from a tendency to form unusually long term mating bonds.

Figure 1: Female Attractiveness Increases with Age in Chimpanzees. Attractiveness index is an average of 4 rank measures of male sexual interest (% male copulatory approaches, male party size, average rank of male mating partners, and rate of male-male mating aggression). Age and attractiveness were positively and statistically-significantly correlated in our study population (r~S~ = 0.73, n = 19, p < 0.001).
Figure 1: Female Attractiveness Increases with Age in Chimpanzees. Attractiveness index is an average of 4 rank measures of male sexual interest (% male copulatory approaches, male party size, average rank of male mating partners, and rate of male-male mating aggression). Age and attractiveness were positively and statistically-significantly correlated in our study population (rS = 0.73, n = 19, p < 0.001).

…In order to evaluate male mate preferences, we analyzed 5 years of aggression data (1998–4200222ya) and 8 years of copulation data (1996–7200321ya) from the Kanyawara chimpanzee community in Kibale National Park, Uganda. The classic problem with inferring mating preferences from mating behavior is that completed copulations always reflect some compromise between male and female reproductive strategies. Males may fail to mate with their preferred partners either because competition from other males is intense or because females express conflicting preferences. We thus employed multiple measures of female attractiveness to assess the consistency of male choice.

…Anecdotal data from Gombe, Tanzania suggest that the correlation of male mate preference with female age is characteristic of the species. Goodall21 describes some old females there as being exceptionally attractive to males, and Tutin7 found that in 30 cases where adult males had a choice between two estrous females in close proximity, they mated with the older of the two 27×.