Bruce Bagemihl - Biological Exuberance

H eterosexual animals that never reproduce, homosexual animals that regularly procreate—breeding and sexual orientation often combine in unexpected and paradoxical ways. In an attempt to understand the origin and function of homosexuality, many scientists have suggested that same-sex activity might actually contribute in some way to reproduction or the perpetuation of the species. In this way, they have tried to carve out a “place” for homosexuality in the scheme of things—but a place on the sidelines, with breeding and heterosexuality decidedly in the center. What many people fail to realize is that reproduction itself often occupies a peripheral position in animal life—either being a “marginal” activity among apparently heterosexual animals, or else a common activity among seemingly “marginal” animals such as those involved in homosexuality. In this chapter we’ll explore some of the various attempts to find a “useful” place for homosexuality in the larger patterns of life and consider why these attempts have often been as misguided as efforts to deny such a “purpose” for homosexuality in the first place.

In 1959 noted evolutionary biologist George Evelyn Hutchinson published a proposal that was radical for its time (and even now remains controversial): he advanced the first theory of the evolutionary value of homosexuality. 1Hutchinson argued that since homosexuality appears to be a biological constant, appearing in generation after generation (in both humans and animals) at a rate that far exceeds that of biological “mistakes,” it must perform some useful function rather than be an aberrant behavior, and moreover, it must have a genetic basis. 2Nearly 20 years later, in 1975, renowned biologist Edward O. Wilson published his seminal work Sociobiology, in which he took up the same theme: homosexuality must be beneficial to a species if it keeps reappearing. Since then, many other “positive” explanations have been proposed for animal homosexuality: some provocative, some absurd, but all revolving around the idea that breeding, heterosexuality, or the overall reproductive profile of an individual or species may be enhanced by homosexuality. 3

A number of these proposals have been formulated with reference to homosexuality in human beings and have not been rigorously evaluated (in either people or animals), in part because of the difficulty of finding relevant data or situations with which to test them. Many have not been applied to the domain of animal homosexuality at all, in part because of the inaccessibility of information about same-sex activity in nonhumans. In this section we will explore a number of these “explanations,” evaluating—in many cases, for the first time—whether they hold true for a variety of different species. While many of these proposals are a welcome change from the view that homosexuality is “abnormal,” they still face significant problems. Often such explanations are simply not consistent with the facts about homosexuality across a broad spectrum of animals. In addition, the underlying assumptions of many of these proposals—especially with regard to the participation (or not) of homosexual, bisexual, transgendered, and heterosexual animals in breeding—are frequently incorrect.

Homosexual or transgendered individuals in many human societies perform a special role, acting as shamans, teachers, or caretakers for the benefit of the tribe as a whole, or for particular families. A number of biologists have suggested that homosexuality in animals may work in a similar fashion. One proposal is that homosexual animals, while not reproducing themselves, act as “helpers” in raising the offspring of their relatives, thereby contributing indirectly to the passing on of their own genes. Another idea is that homosexuality, because it is nonreproductive, acts as a self-regulating mechanism to control a species’ population growth. 4Both of these theories have generated considerable controversy, yet little concrete evidence to either support or refute them has been brought forward. Moreover, neither of these proposals has been evaluated with respect to animals—even though they are directly testable with data from animal species—probably because a comprehensive and detailed survey of nonhuman homosexuality has not been previously available. Once the relevant facets of behavior and social organization are considered, however, it becomes quite clear that neither of these hypotheses can be correct.

Underlying each of these proposals is the assumption that animals who engage in homosexuality do not reproduce (and must therefore “contribute” in some other way)—yet this is patently false. As we saw in earlier chapters, bisexuality is widespread in the animal kingdom: in more than half of the mammal and bird species in which homosexuality occurs, at least some individuals engage in both same-sex and opposite-sex interactions. Moreover, actual breeding by animals who participate in homosexuality has been verified in more than 65 species. This includes animals who are heterosexually paired and raise offspring but have outside homosexual interactions (Greenshanks, Little Egrets, Tree Swallows, Gray-capped Social Weavers); animals who engage in homosexuality as single parents (Japanese Macaques, Hanuman Langurs, Northern Fur Seals); animals who raise offspring in bisexual trios or quartets (Black Swans, Greylag Geese, Oystercatchers, Jackdaws) or in same-sex pairs as a result of outside heterosexual matings (Ring-billed Gulls, Western Gulls); females who participate in homosexual activity while pregnant (Gorillas, Takhi, Vicunas) or even while their infants are clinging to them (Bonobos); animals who breed at some point in their lives prior to or following a period of homosexuality (Orang-utans, Rufous Rat Kangaroos, Emus, Silver Gulls, Bicolored Antbirds); homosexuality among those individuals in a population who monopolize most of the breeding opportunities (Nilgiri Langurs, Mountain Zebras, Bighorn Sheep, Ruffs, Pukeko); and animals that have incestuous homosexual relations with their own offspring (White-handed Gibbons, Red Foxes, Livingstone’s Fruit Bats, Ocellated Antbirds). Thus, animals use multiple strategies to combine homosexuality with breeding, and even animals who may “prefer” homosexuality or have more same-sex than opposite-sex interactions can successfully raise offspring. 5It is simply not true that animals who participate in homosexuality are unable to reproduce and pass on their genes to future generations. Of course, some animals are exclusively homosexual and never reproduce (as discussed in chapter 2) or else are unsuccessful breeders in either a heterosexual or a homosexual context, but reproduction is most definitely not limited to animals that only have heterosexual contacts.

Setting aside the fact that the initial premise of these two hypotheses is incorrect, is there nevertheless any validity to the substance and implications of each of these proposals? As it turns out, the animal world offers us a ready-made natural “laboratory,” as it were, to test the first hypothesis, that homosexual animals act as “helpers” for other members of their own species or families. Numerous animals have developed a variety of “helping systems” in which individuals contribute to the care and upbringing of youngsters that are not their own offspring (although they may be relatives). These arrangements take several different forms: communal or cooperative breeding systems (group-living arrangements in which only some animals breed while the others assist them); “day-care” systems such as crèches or nursery groups, in which youngsters from more than one family are pooled together and watched over by one or two caretakers; alloparenting, in which individuals assist parents in duties such as feeding, protecting, carrying, or even “baby-sitting” their offspring; and adoption, involving foster-parenting of orphaned, lost, or abandoned youngsters. 6Yet virtually none of these helper systems is preferentially “staffed” by homosexual animals or associated in any particular way with homosexuality. True, some individuals that engage in homosexuality certainly do act as helpers in some of these systems, but there is not a privileged association between homosexuality and helping as has been hypothesized. In fact, in some instances the connection between homosexuality and helping is the exact opposite of what is predicted by this hypothesis.