Here's to you, Mrs. Chimpinson

3 minute read

Muller and colleagues (2006) found that male chimpanzees approach older females more often for copulation (compared to younger females), more males tend to hang around with older females in estrus (compared to younger females), older females tend to mate more often with high-ranking males, and males compete more aggressively to mate with older females:

This study demonstrates that male chimpanzees do not merely disdain young females but actively prefer older mothers to younger mothers. Our findings are consistent with evidence that a variety of mammals demonstrate male choosiness and with prior indications that, in other promiscuously breeding primates, young females are generally eschewed. They provide a stark contrast to patterns of male mate choice in our own species. Such choice has been clearly established, both by cross-cultural studies showing that women's sexual attractiveness peaks in the late teens to early twenties and declines steadily thereafter with age and parity, and experimental data showing that many of the features men find sexually attractive are paedomorphic; these features include large eyes, wide cheekbones, narrow cheeks, small noses, slight chins, slender jaws, low waist-to-hip ratios, and high voices.
At least three human traits that do not occur in chimpanzees could contribute to the observed difference in male mate choice. Long-term pair bonds are hypothesized to promote preferences for youth because men who choose relatively young partners maximize their future reproductive opportunities with those partners. Direct paternal investment may favor men who choose young mates because young women are less likely to have offspring from previous partners, and this minimizes men's contributions to unrelated offspring. Menopause, and the associated decline in female fecundity starting in the late twenties, may further exaggerate preferences for youth by limiting women's future fertility. In contrast, males of more promiscuous species, such as the chimpanzee, are expected to focus on their immediate reproductive opportunities and discount females' longer-term reproductive value. Additionally, unlike humans, chimpanzees provide no direct paternal care to offspring and show no evidence for menopause. Further analysis of male mate choice among species in which such traits are isolated will help in discriminating their relative importance for the evolution of male preference for youth.

The title of the post suggests the obvious: there is no single human pattern of male mating preference; there is variability around a mean, including certain strong aversions. This must be true of chimpanzees also, so the question is why the mean should be different.

The suggestion here is not unreasonable, but I think it is incomplete. In humans, for example, there is a very strong influence of personal history and continuing interactions -- which explains why older men would choose to continue with their wives instead of going for younger women. Old-fashioned sentimentalists like me call this "love" (Hi, Gretchen!).

Since older chimpanzee females have a much longer history with resident males than do young females, who mainly came from somewhere else, it seems just as plausible that familiarity is important to chimpanzees as well. In that context, a preference for younger females might depend on group structure, dispersal strategies, and the lack of availability of older females, not merely on ultimate lifetime investment. I mention this because it would have been very difficult for a hominid to make the jump immediately to very long consortships from a chimpanzee-like group structure, but it might have been relatively easier from other group structures.

Another solution, which the paper mentions, is the importance of rank for older chimpanzee females, which plays a direct role in their offspring's fitness -- including their male offspring. If a male wants to maximize the chance of having high-ranking male offspring, the way to do it is to mate with a high-ranking female. In humans, this can sometimes be much less important because paternity may be recognized -- a high-ranking male may confer rank to his sons directly.


Muller MN, Thompson ME, Wrangham RW. 2006. Male chimpanzees prefer mating with old females. Curr Biol 16:2234-2238. DOI link