Concealed Ovulation - Evolutionary Hypotheses

Evolutionary Hypotheses

Concealed (or “hidden”) ovulation means the period of fertility is not detectable in woman, whereas chimpanzees advertise ovulation by an obvious swelling of the genitals. Women can be partly aware of their ovulation along the menstrual phases, but men are essentially unable to detect ovulation in women. Most primates have semiconcealed ovulation, thus one can think that the common ancestor had semiconcealed ovulation, that was transmitted to gorillas, but that later evolved in concealed ovulation in humans and advertised ovulation in chimpanzees (see Homininae and "Why is Sex Fun?").

There are multiple evolutionary psychology explanations for concealed ovulation. Some posit that the lack of signaling in some species is a retained ancestral trait, not something that existed previously and later disappeared. If signaling is supposed to have existed and was lost, then it could have been merely due to reduced adaptive importance and lessened selection, or due to direct adaptive advantages for the concealment of ovulation. Yet another possibility, specifically for humans, is that while highly specific signaling of the ovulation is absent, the female form evolved to mimic permanent signaling of fertility. Several hypotheses aim toward answering these questions. It may be possible for elements from multiple hypotheses to be true.