In a recent Current Biology article, “Male Chimpanzees Prefer Mating with Old Females,” Muller, Thompson, and Wrangham report on the sexual attraction of males to females in the Kanyawara chimpanzee community in Kibale National Park, Uganda. The authors indicate that female chimpanzee mothers become more sexually attractive with age. A concept that is contrary to human norms.
“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 (i.e. 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.”
The authors note that the functional explanation for this attractiveness is not necessarily clear and long-term data is currently undergoing analysis to better explain some possibilities: older females tend to be high ranking which translates into increased fitness (and chimps do not go through menopause), more experience as a mother could lead to increased infant survival, and the genes of those who live longer are desirable.
In the meantime, the authors conclude that natural selection has shaped the values for female mates quite differently for chimps and humans.
“Chimpanzee males may not find the wrinkled skin, ragged ears, irregular bald patches, and elongated nipple of their aged females as alluring as human men find the full lips and smooth complexions of young women, but they are clearly not reacting negatively to such cues.”