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Homosexuality is not uniquely human. A wide variety of mammals
and birds experience same-sex sexual encounters. Williams, Adaptation
and Natural Selection, Princeton University Press, 1966, Page
204; Bagemihl, Biological Exuberance: Animal Homosexuality
and Natural Diversity, St Martin's Press, New York, 1999. Just
as with humans, the spectrum of homosexual behaviors is plentiful.
In some cases, homosexual encounters resemble heterosexual courtship. Males
perform to each other the same repertoire of behaviors that they
normally display when courting females. At other times, males
may simply display affection to each other as observed in male
lions who may rub heads and roll around together, without overt
sexual content.
Sexual contact, however, is fairly frequently observed between
members of the same sex. Female bonobos, a highly social
primate, engage in mutual genital rubbing, and other explicitly
sexual types of physical contacts. During same-sex grooming,
male vampire bats develop erections. After engaging in prolonged
sessions of affectionate rubbing, male giraffes display mounting
behaviors that culminate in apparent orgasm. The same kinds
of behaviors are observed in birds. Of tern pairs who shared
in the care and tending of eggs and offspring, it was discovered
that 12% were actually female couples. Apparently, females
fertilized their eggs with paired males, but raised their offspring
with a partner of the same-sex. Lesbian behaviors were also
observed in Japanese macaques. Females have been observed
to spend extended periods of time together, grooming and participating
in sexual activity that ends in orgasm for both partners. For more
examples, read Bagemihl, ibid.
Despite widespread documentation of homosexuality in the animal
kingdom, evolutionary biologists are confounded by it. As
a fruitless, reproductively dead-end, behavior, it logically would
be culled from the population because its practice does not result
in children and therefore would not be inherited by successive
populations. One solution to this dilemma is to say that
homosexuality is not inherited, but is a psychological disorder,
or even a disease. In fact, homosexuality was once classified
as a psychological disorder, but no longer is. More recent
evidence suggests that there is a genetic component to homosexual
behavior. See, e.g., Hamer and Copeland, The Science
of Desire, 1994. Reproductive functions are generally
less precise in execution and more imperfectly timed than other
behaviors because the selective pressure to maintain them in the
gene pool are so great. Williams, Pages 204-205. So
what if a little energy could have been more constructively spent.
If homosexuality is not a disease or a maladaptive behavior, then
what is it? Many homosexuals do reproduce, and could even be more
fecund than heterosexuals when they do, keeping homosexuality flowing
through the gene pool. The possibility that homosexuality
has reproductive advantages for carriers of the genes (e.g., greater
fertility, or better parental care) who do not express the behavior
is one explanation for its stability in the gene pool, making up
for the fact that the gene stops in individuals who expressly manifest
the behavior. It can also be explained as an adaptive behavior
to ease stress in social encounters, and to facilitate cooperation
between individuals who otherwise possess competing interests.
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