Biological Exuberance: Animal Homosexuality and Natural Diversity

Stumptail Macaque (Goldfoot et al. 1980); Rhesus Macaque (Zumpe, D., and R. P. Michael [1968] “The Clutching Reaction and Orgasm in the Female Rhesus Monkey [Macaca mulatta],” Journal of Endocrinology 40:117—23). In what is perhaps the most extreme “experiment” of this type, female Rhesus Macaques were strapped to an apparatus made of iron and wood and forced to undergo stimulation with a dildo or “penis substitute” while their responses were monitored with electrodes (Burton, F. D. [1971] “Sexual Climax in Female Macaca mulatta,” in J. Biegert and W. Leutenegger, eds., Proceedings of the 3rd International Congress of Primatology, vol. 3, pp. 180-91 [Basel: S. Karger]).

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For a sample of some of this debate, see Allen, M. L., and W. B. Lemmon (1981) “Orgasm in Female Primates,” American Journal of Primatology 1:15—34; Rancour- Laferrière, D. (1983) “Four Adaptive Aspects of the Female Orgasm,” Journal of Social and Biological Structures 6:319-33; Baker, R., and M. A. Bellis (1995) Human Sperm Competition: Copulation, Masturbation, and Infidelity, pp. 234-49 (London: Chapman and Hall); Hrdy, S.B. (1996) “The Evolution of Female Orgasms: Logic Please but No Atavism,” Animal Behavior 52:851-52; Thornhill, R., and S. W. Gangstead (1996) “Human Female Copulatory Orgasm: A Human Adaptation or Phylogenetic Holdover,” Animal Behavior 52:853—55. For recent discussions that sidestep the question of sexual pleasure with regard to the “function” of the clitoris, as well as in relation to a variety of specific sexual behaviors (e.g., stimulatory movements such as thrusting during intercourse, multiple ejaculations, lengthy copulations, etc.), see Baker and Bellis, Human Sperm Competition, pp. 126—31; Eberhard, Female Control, pp. 142—46, 204—45, 248—54.

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A similar conundrum pertains to the “function” of the male copulatory organ in birds. Most male birds do not have a penis—insemination is achieved through simple contact of male and female genital apertures—and therefore its occurrence in some birds would appear to be, from a functional standpoint, “superfluous” (which could perhaps also be said about its occurrence in all other species). Moreover, in those species that do have a phallus (about 3 percent of all birds), its precise role in ejaculation and transporting semen remains unclear (see King, A. S. [1981] “Phallus,” in A. S. King and J. McLelland, eds., Form and Function in Birds, vol. 2, pp. 107—47 [London: Academic Press]; Briskie, J. V., and R. Montgomerie [1997] “Sexual Selection and the Intromittent Organ of Birds,” Journal of Avian Biology 28:73-86). In ratites such as Ostriches, Rheas, and Emus, as well as in Ducks and Geese, for example, the penis does not have an orifice connected to the male’s internal reproductive organs, and he simply ejaculates through his cloaca (at the base of the penis) as do all other male birds without a phallus. Although it carries a groove on its outside surface that may help direct semen during penetration, the penis does not transport semen internally. Moreover, in some birds such as buffalo weavers, the phallus has no such groove whatsoever (nor any internal ducts) and its role in sperm transport is even less clear. Consequently, the phallus’s reproductive “function” in these species is nearly as puzzling to biologists as that of the clitoris—the possibility that it could give sexual pleasure (to male and/or female) is rarely, if ever, even considered. Indeed, it is perhaps just as appropriate to speak of a male “clitoris” as it is of an actual “penis” in these cases, since the anatomy and function(s) of this organ may not be directly related to insemination (i.e., sperm transport). In addition, display of the phallus may also be an important element of courtship (as opposed to copulatory) activity in some species, as in the male Ostrich’s “penis-swinging” ceremony (Sauer and Sauer 1966:56-57) and possible penile displays in the white-billed buffalo weaver (Birkhead, T. R., M. T. Stanback, and R. E. Simmons [1993] “The Phalloid Organ of Buffalo Weavers Bubalornis,” p. 330, Ibis 135:326-31).

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