The flight of the lesbian raven

Bruce Bagemihl's "Biological Exuberance" is something of an underground classic. The book meticulously documents the existence of homosexual behaviour among animals. It turns out to be more common and more normal than many care to admit or want to imagine.

A typical misconception is that homosexual behaviour is limited to mammals held in captivity. Another is that animals simply cannot be homosexual, since the purpose of animal life is to procreate. This misconception exists even if we interpret "purpose" in a purely figurative way. Why would natural selection select for homosexuality?

Those willing to explode their preconceptions will definitely find this book shocking, thrilling and even humorous. Brace yourselves for lesbian ravens, gay magpies, aggressive homosexual couples of black swans which adopt and raise chicks, homosexual trios among gulls and bisexual trios among geese! Mammals aren't much better, it seems. Some deer are transgendered, male bighorn sheep live in what one biologist called "homosexual societies", and then there's the bonobo, our evolutionary cousins which many sociobiologists desperately want to blank out since they have the gall to be peaceful, matriarchal, bisexual vegans - quite unlike the common chimp, which can be counted on to act in true evo-psych fashion. And then, maybe not entirely, since common chimps apparently also "do it". Well, at least they still are aggressive hunters!

In a homophobic society, all this is hard to stomach, and Bagemihl devotes several chapters to a historical overview of how scientists have attempted to explain away homosexual behaviour among animals. Calling it aggression, play or aberration are common strategies. Homosexual couples have been called "pseudocouples". And yes, scientists have wondered which animal "plays the female". None of this is terribly surprising to those of us who browsed through the sociobiological literature with its blatant androcentrism, obviously connected to modern, Western patriarchy. If "Mother Nature is a sexist", then of course homosexual behaviour must be an aberration.

Still, there is also a serious scientific issue involved. If natural selection is the central mechanism of evolution, how can homosexual behaviour be selected for? This is a problem even if we assume that the animals in question are "really" bisexual, since homosexual behaviour is time-consuming, time that could be used for heterosexual pursuits instead (or foraging). The problem is even graver for those who believe that all human behaviour is adaptive, since homosexuality among humans exists in a "pure" form. Some gays, after all, don't breed.

The standard Neo-Darwinist response to animal homosexuality, once it was recognized as a real phenomenon, is to find some useful function for it which enhances *heterosexual* reproductive success. Wilson's infamous but daring proposal that homosexuals may have been "helpers at the nest" is a case in point. Bagemihl believes it's heterosexist to ask in what way homosexuality is useful to heterosexuality, but nevertheless argues at length against the common explanations of animal homosexuality. In this context, he also points out that there is a wide variety of non-reproductive and alternative heterosexualities among animals. Many animals don't breed at all, nonbreeding is often non-coerced, and such animals may live longer than breeders. This raises the question in what sense it's adaptive for an individual not to breed? The genes for nonbreeding seem to perpetuate themselves generation after generation, as does homosexuality (among some animals, even pure homosexuality exists).

Unfortunately, at this point Bagemihl essentially gives up any attempt at a scientific explanation, instead devoting an entire chapter to a vaguely spiritual and new agey wordview based on "the wisdom of indigenous peoples". This part of the book sounds more Woodstock than Darwin, and feels completely out of place in an otherwise heavily referenced scientific work. The author's favourite philosopher seems to be George Bataille. The idea of "biological exuberance" seems to be a hippie call to let go of all dogmas and gently flow down the stream of Mysterious Life. Well, at least he's honest.

The rest of us would like a Neo-Darwinist or at least evolutionary explanation to the existence of homosexuality and non-reproductive heterosexuality. Group selection? Bisexual superiority? Is evolution more random than expected? Why should all behaviours be "adaptive", anyway?

Finally, I noticed a few sloppy errors and false starts in this book. Bagemihl uses the naked mole-rat as an example of a species where most individuals don't breed. In this particular case, however, the non-breeding has a logical explanation: mole-rats have the same social structure as social insects, with one "queen" controlling a colony of sterile "workers". At another point, Bagemihl mentions that snow geese and other birds sometimes take care of eggs laid close to their nest by another individual. This admittedly curious behaviour might be an example of brood parasitism, rather than co-operative breeding. (See N.B. Davies' excellent study "Cuckoos, cowbirds and other cheats".) It's also unclear why Bagemihl puts so much emphasis on the competition between males and females within certain species, since this can be explained from a Neo-Darwinist perspective, or even a narrowly sociobiological one.

Despite shortcomings of this kind, "Biological Exuberance" is nevertheless a must read for everyone interested in animals, homosexuality and the uses and misuses of ideology in science.