Biological Exuberance: Animal Homosexuality and Natural Diversity

Needless to say, the near extinction of this New Zealand bird is not a result of homosexuality in this species, but rather is due to the destructive effects of human activities—habitat loss because of drainage and hydroelectric development, as well as severe depletion by nonnative species introduced to the islands (Reed 1993:771).

19

For a review of some of these strategies, and information on other possible mechanisms, see the discussion in the following section “Nonreproductive and Alternative Heterosexualities in Animals,” as well as the following references: Cohen, M. N., R. S. Malpass, and H. G. Klein, eds. (1980) Biosocial Mechanisms of Population Regulation (New Haven: Yale University Press); Wilson, E. O. (1975) Sociobiology: The New Synthesis, pp. 82-90 (Cambridge, Mass.: Belknap Press); Wynne-Edwards, V. C. (1965) “Social Organization as a Population Regulator,” in P. Ellis, ed., Social Organization of Animal Communities, pp. 173—80, Symposia of the Zoological Society of London no. 14 (London: Academic Press); Wynne-Edwards, V. C. (1959) “The Control of Population-Density Through Social Behavior: A Hypothesis,” Ibis 101:436-41.

20

For various statements of this hypothesis, see Hutchinson, “A Speculative Consideration of Certain Possible Forms of Sexual Selection in Man”; Kirsch and Rodman, “Selection and Sexuality: The Darwinian View of Homosexuality”; for a refutation, see Futuyama and Risch, “Sexual Orientation, Sociobiology, and Evolution.” It is also possible that the homosexual gene would be recessive, i.e., not expressed when combined with the heterosexual gene—such individuals would therefore not be bisexual, but could still have a reproductive advantage. However, in the absence of any actual genetic information, there is no way to evaluate this version of the hypothesis, since individuals with a recessive homosexual gene would presumably be (superficially) indistinguishable from those with two heterosexual genes (for an alternate view and several other versions of this hypothesis, see McKnight, J. [1997] Straight Science? Homosexuality, Evolution, and Adaptation [London: Routledge]). Therefore, the following discussion is confined to assessing the version in which such individuals are actually behaviorally bisexual (e.g., Weinrich’s 1987 version). In the spirit of the “bisexual superiority” hypothesis, see also Caldwell and Caldwell’s (1967:15) suggestion that bisexuality in Bottlenose Dolphins represents a “more evolved” state because their sexuality is neither limited to reproductive activity nor confined to partners of only one sex. These scientists suggest that Dolphins may be more advanced than humans in this regard, based on the (erroneous) belief that Dolphins do not exhibit exclusive homosexuality, or (in their words) are not “fixated on a biologically inappropriate stimulus to the exclusion of the biologically appropriate one.” For more on the myth of human uniqueness with regard to exclusive homosexuality, see chapter 2.

21

Based on data in fig. 2, Braithwaite 1981:140; on heterosexual partitioning of incubation duties, and the possible advantages of greater male participation, see O‘Brien 1990:1186 and Brugger and Taborsky 1994. Another possible case of bisexual pairs being more successful at reproduction concerns the Snow Goose. Diamond (1989:101) had speculated that female pairs (in this and other species) that fertilize their eggs by mating with males might be able to produce more offspring than heterosexual pairs. However, this does not appear to be a genuine case: the initial suggestion was entirely conjectural and not based on actual long-term studies of the reproductive output of same-sex versus opposite-sex pairs. Furthermore, this idea was later shown to be based on faulty reasoning, since the critical factor for comparing reproductive advantage is the number of goslings produced by each female in the pair, not by the pair as a whole (as the females are usually not related to one another). See Conover (1989) and Grether and Weaver (1990) for further discussion.

22

Ruff (Hogan-Warburg 1966:179; van Rhijn 1973:197, 1991:76; Hugie and Lank 1997:220); Greylag Goose (Lorenz 1979:59-60); Pukeko (Jamieson and Craig 1987a:1251); Guianan Cock-of-the-Rock (Trail and Koutnik 1986:211, 215); Oystercatcher (Heg and van Treuren 1998:690; Ens 1998:635).

23

Sociable Weaver (based on data in Collias and Collias 1980:248[table 5] Bonnet Macaque (based on data in Sugiyama 1971:252, 259—60 [tables 2, 8, 9]); Asiatic Elephant (based on data in Poole et al. 1997:306-7 [fig.5]); Japanese Macaque (Hanby 1974:838; Vasey 1996 and personal communication).

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