Biological Exuberance: Animal Homosexuality and Natural Diversity

As in most other “explanations” of homosexuality, these include both “proximate” and “ultimate” factors (a distinction widely employed in evolutionary biology). “Proximate” explanations focus on the immediate behavioral, social, physiological, demographic, environmental, and other factors that supposedly “trigger” or lead to homosexual activity, while “ultimate” explanations focus on the wider reproductive and evolutionary benefits that supposedly accrue from such activity.

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Weinrich, Sexual Landscapes; Ruse, M. (1982) “Are There Gay Genes? Sociobiology and Homosexuality,” Journal of Homosexuality 6:5—34; Kirsch, J. A. W., and J. E. Rodman (1982) “Selection and Sexuality: The Darwinian View of Homosexuality,” in W. Paul, J. D. Weinrich, J. C. Gonsiorek, and M. E. Hotveldt, eds., Homosexuality: Social, Psychological, and Biological Issues, pp. 183-95 (Beverly Hills, Calif.: SAGE Publications); Wilson, E. O. (1978) On Human Nature, pp. 142-47 (Cambridge, Mass.: Harvard University Press); Trivers, R. L. (1974) “Parent-Offspring Conflict,” pp. 260—62, American Zoologist 14:249-64. For a critique of these theories as applied to humans, see Futuyama, D. J., and S. J. Risch (1984) “Sexual Orientation, Sociobiology, and Evolution,” Journal of Homosexuality 9:157—68. For specific examples of homosexuality cited as a possible population-regulation mechanism—including nonreproductive sexuality as a stress-induced response to overpopulation in some species, and homosexuality as a form of “birth control” in humans—see Calhoun, J. B. (1962) “Population Density and Social Pathology,” Scientific American 206(2):139-48; von Holst, D. (1974) “Social Stress in the Tree-Shrew: Its Causes and Physiological and Ethological Consequences,” in R. D. Martin, G. A. Doyle, and A. C. Walker, eds., Prosimian Biology, pp. 389-411 (Pittsburgh: University of Pittsburgh Press); Denniston 1980:38 (Squirrel Monkey); Harris, M. (1980) Culture, People, and Nature, p. 208 (New York: Harper and Row). For more on the special “role” of homosexual and transgendered humans in some indigenous cultures, see chapter 6.

5

See the discussion of same-sex parenting in chapter 1.

6

See pp. 206—7 for further discussion of these and other alternate parenting arrangements.

7

For a complete list of bird species with helpers, see Brown, J. L. (1987) Helping and Communal Breeding in Birds, pp. 18—24 (table 2.2) (Princeton: Princeton University Press). Three other species in which homosexual behavior occurs (Ostriches, House Sparrows, and Sociable Weavers) are classified by Brown as having helpers, but it is not clear that these represent genuine cases of helping. Even if they did, however, they would still not support the “helper” theory of homosexuality because homosexuality is either not limited to helpers in these species, or else not all helpers engage in homosexual behavior. In Ostriches “helping” behavior actually consists of foster-parenting by breeding pairs of males and females (ibid., p. 161); homosexuality only occurs in males in this species, and probably nonbreeders at that. In House Sparrows helping occurs occasionally among juveniles, probably of both sexes, and in only some populations (p. 31), while homosexual behavior only occurs in (a few) adult males. And in Sociable Weavers, breeding pairs are assisted in building communal nests, probably by birds of both sexes, but such birds do not help feed their young (see Maclean 1973); homosexuality occurs in both breeders and nonbreeders, but only males. Recently, helping behavior by adolescent males has also been discovered in Greater Rheas; however, this phenomenon is distinct from same-sex coparenting (and sexual activity) in this species, which involves adult males‘(Codenotti and Alvarez 1997:570). For other surveys of the phenomena of communal breeding and helpers in birds, see Skutch, A. F. (1987) Helpers at Birds’ Nests: A Worldwide Survey of Cooperative Breeding and Related Behavior (Iowa City: University of Iowa Press); Stacey, P. B., and W. D. Koenig, eds. (1990) Cooperative Breeding in Birds (Cambridge: Cambridge University Press).

8

See chapters 1 and 4 for discussion of the fact that many cases of homosexuality in animals have probably been missed, overlooked, or remain to be discovered.

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