You lie awake at night on an African savanna,
amid the animal shrieks, the clamor of birds, and the insects' drone. Then
out of the darkness comes a riff of loud, explosive barks, trailing off
into a series of grunts: the copulation call of the female baboon. "It's
really quite spectacular," says Guy Cowlishaw, a biologist at University
College London. Cowlishaw and his colleague Sanjida O'Connell have listened
to many such calls, 152 in fact. They eavesdrop not out of any prurient
interest but to shed light on a provocative, if little researched, question--why
certain female primates call out loudly during copulation.
Are they simply cries of pleasure? "Obviously it may very well be a pleasurable experience," says Cowlishaw. "That's difficult for us to say." But most animal behaviorists believe the calls have an evolutionary significance. One hypothesis is that female baboons cry out in order to synchronize orgasm with males, which would aid fertilization by helping sperm travel up the reproductive tract. Another theory suggests that subordinate females call out to advertise that they have the support of a male, which may help them avoid harassment by high-ranking females. But after eight months of observing mating baboons at a Namibian nature preserve, Cowlishaw and O'Connell realized that these theories did not explain what they were seeing.
The biologists found that females cried out after copulation, so the calls couldn't possibly have been orgasmic. Moreover, females of all ranks made the calls, even dominant females who would never be bothered by other females. Cowlishaw and O'Connell have found support for a different theory. The calls, they say, promote competition among males--and among sperm.
By calling out, often while darting away from her paramour, a female tries to attract other males to mate with her. Such promiscuity, say Cowlishaw and O'Connell, increases her chances of getting good genes for her offspring: of the several males that copulate with her, the one with the fittest sperm will succeed in fertilizing her. Moreover, uncertain paternity also helps the female. Dominant males may attack and kill infant baboons that they have not sired. But if a male thinks he may be the father of a baby baboon, then in the interest of promoting the spread of his own genes, he won't harm the baby.
What does all this say about human behavior? "Personally," says Cowlishaw, "I think the connection would be quite tenuous."