In trying to understand "natural" sexuality, a look at the world of the bonobo is intriguing. Often loosely described as "chimps", bonobos are in fact a quite distinct species, closely allied to both chimps and to humans, and may in fact be the closest of all primates to humans in evolutionary development. In addition to physiological and genetic similarities, they also show some features of sexual behaviour that are unusual in animals - but familiar to humans. For example, females remain sexually receptive for far longer than other species. Instead of being physically ready for sex for just a few days in her cycle, the female bonobo is almost continuously sexually attractive and willing for sex. Intercourse is more frequent than in other primates, although the reproduction rate is similar: there is a partial separation between sex and reproduction. Mating is more often face to face, like humans, than in other animals, where the dog-like position is almost universal. Both males and females become sexually aroused remarkably easily. Oh, and there's a great deal of same sex activity. Frans De Waal, on whose research I base my notes, says that the most typical sexual pattern is genital rubbing between females:
One female facing another clings with arms and legs to a partner that, standing on both hands and feet, lifts her off the ground. The two females then rub their genital swellings laterally together, emitting grins and squeals that probably reflect orgasmic experiences.
De Waal first became interested in bonobo behaviour not for its sexual component, but as part of a study into primate aggression. In continuous observations of bonobos in a zoo, he found that a standard feature of the behaviour was sexual arousal and intercourse immediately before feeding. As soon as a caretaker approached with food, the males would develop erections, and the animals would invite each other for sex. (This is not just an aberration of captivity. Other researchers have observed the same association between food and sex in the wild: after a group had entered trees with ripe fruit, or after they had killed a young prey animal, there would be a flurry of sexual contacts before settling down to eat.)
De Waal later found that it is not just food that leads to sexual arousal, but anything that gets the interest of more than one animal at a time - in other words, anything that could lead to competition. In the zoo environment, when two bonobos share an interest in a cardboard box thrown into the enclosure, they briefly mount each other before playing with the box.
In some aggressive contexts related to conflicts between animals, there will often be genital contact to follow. Where one male drives another away from a female, the two males may later reunite for some mutual genital rubbing. Or if one female strikes a juvenile, its mother may lunge at the other female - but as with the males, this brief conflict will be followed by the two rubbing their genitals together.
De Waal thus concludes that sexual behaviour among bonobos is a mechanism to reduce conflict:
During reconciliations, bonobos use the same sexual repertoire as they do during feeding time. Based on an analysis of many such incidents, my study yielded the first solid evidence for sexual behavior as a mechanism to overcome aggression. Not that this function is absent in other animals--or in humans, for that matter--but the art of sexual reconciliation may well have reached its evolutionary peak in the bonobo. For these animals, sexual behavior is indistinguishable from social behaviour.
Sexual relationships are also used in a more positive way, to forge social bonds, particularly between the females. As with many animal species, bonobos live in clan groups. In their case, the males remain for life in their birth clans, so they will know all the other individuals. It is the female bonobos who leave, and start a new life as adults in a new clan, where they are strangers. They routinely approach one or two senior females, and attempt to establish a sexual relationship. If this is reciprocated, the association becomes permanent, with the older females acting as guardians to the younger. Later, as the newcomers themselves become established seniors within the clan, they may likewise accept sexual approaches from new female arrivals, and take on their guardianship.
Here we can point out that this use of sexual relationships to promote social bonding and avoid conflict has clear parallels in human society. At the domestic level, the "kiss and make-up scenario" is well known, in which a quarrel between partners may be followed by particularly intense love-making. At a grander level, for many centuries of European history, formal marriage was usual only for the wealthy classes, to protect property and inheritance rights. At the highest social levels, dynastic marriages were frequently arranged to ensure political alliances between royal houses - and to reduce the risk of war. Elsewhere, other societies have used homosexual relationships between men in the same dynastic way, to promote cordial relationships between clans. This has been noted in medieval Egypt, and in China.
There is one other feature of bonobo sexuality that I found has a remarkable resemblance to some human practice. Freed from the tight connection between intercourse and reproduction,young and attractive bonobo females are able to use their charms for material gain. Some females have been observed to approach males with an enticing food supply with clear a clearly sexual offer. After intercourse, the male will share his food with the female, who then leaves.
Females offering males sexual favours for profit: sound familiar?
de Waal, Frans B.M. : Bonobo Sex & Society, Scientific American, arch 1995, which I found on-line here
See also my previous post here at QTC:
- The Pygmy Chimpanzee: Evolutionary Biology and Behavior Edited by Randall L. Susman. Plenum Press, 1984.
- THE COMMUNICATIVE REPERTOIRE OF CAPTIVE BONOBOS (PAN PANISCUS) COMPARED TO THAT OF CHIMPANZEES. F.B.M. de Waal in "Behaviour," Vol. 106, Nos. 3-4, pages 183-251; September 1988.
- PEACEMAKING AMONG PRIMATES. F.B.M. de Waal. Harvard University Press, 1989.
- Understanding Chimpanzees Edited by Paul Heltne and Linda A. Marquardt. Harvard University Press, 1989.
- The Last Ape: Pygmy Chimpanzee Behavior and Ecology Takayoshi Kano. Stanford University Press, 1992.
- Chimpanzee Cultures: With a Foreword by Jane Goodall R. Wrangham, W. C. McGrew, F.B.M. de Waal and P. Heltne. Harvard University Press, 1994.