Is Their An Evolutionary Role for
Homosexuality and Same-Sex Attraction?
Male homosexuality doesn't make complete sense from an evolutionary
point of view. It appears that the trait is heritable, but because
homosexual men are much less likely to produce offspring than heterosexual
men, shouldn't the genes for this trait have been extinguished long
ago? What value could this sexual orientation have, that it has
persisted for eons even without any discernible reproductive advantage?
One possible explanation is what evolutionary psychologists call
the "kin selection hypothesis." What that means is that
homosexuality may convey an indirect benefit by enhancing the
survival prospects of close relatives. Specifically, the theory
holds that homosexual men might enhance their own genetic prospects
by being "helpers in the nest." By acting altruistically
toward nieces and nephews, homosexual men would perpetuate the
family genes, including some of their own.
Two evolutionary psychologists, Paul Vasey and Doug VanderLaan
of the University of Lethbridge, Canada tested this idea for the
past several years on the Pacific island of Samoa. They chose
Samoa because males who prefer men as sexual partners are widely
recognized and accepted there as a distinct gender category --
called fa'afafine -- neither man nor woman. The fa'afafine tend
to be effeminate, and exclusively attracted to adult men as sexual
partners. This clear demarcation makes it easier to identify a
sample for study.
Past research has shown that the fa'afafine are much more altruistically
inclined toward their nieces and nephews than either Samoan women
or heterosexual men. They are willing to babysit a lot, tutor
their nieces and nephews in art and music, and help out financially
-- paying for medical care and education and so forth. In a new
study, the scientists set out to unravel the psychology of the
fa'afafine, to see if their altruism is targeted specifically
at kin rather than kids in general.
They recruited a large sample of fa'afafine, and comparable samples
of women and heterosexual men. They gave them all a series of
questionnaires, measuring their willingness to help their nieces
and nephews in various ways -- caretaking, gifts, teaching --
and also their willingness to do these things for other, unrelated
kids. The findings, reported on-line this week in the journal
Psychological Science, lend strong support to the kin selection
idea. Compared to Samoan women and heterosexual men, the fa'afafine
showed a much weaker link between their avuncular -- or uncle
like -- behavior and their altruism toward kids generally. This
cognitive dissociation, the scientists argue, allows the fa'afafine
to allocate their resources more efficiently and precisely to
their kin -- and thus enhance their own evolutionary prospects.
To compensate for being childless, each fa'afafine would have
to somehow support the survival of two additional nieces or nephews
who would otherwise not have existed. "If kin selection is
the sole mechanism by which genes for male same-sex sexual attraction
are maintained over time," the fa'afafine must be "super
uncles" to earn their evolutionary keep, explains Vasey.
Consequently, Vasey suggests "that the fa'afafine's avuncularity
probably contributes to the evolutionary survival of genes for
male same-sex sexual attraction, but is unlikely to entirely offset
the costs of not reproducing."
Do these findings have any meaning outside of Samoa? Yes and
no. Samoan culture is very different from most Western cultures.
Samoan culture is very localized, and centered on tight-knit extended
families, whereas Western societies tend to be highly individualistic
and homophobic. Families are also much more geographically dispersed
in Western cultures, diminishing the role that bachelor uncles
can play in the extended family, even if they choose to. But in
this sense, the researchers say, Samoa's communitarian culture
may be more -- not less -- representative of the environment in
which male same-sex sexuality evolved eons ago. In that sense,
it's not the bachelor uncle who is poorly adapted to the world,
but rather the modern Western world that has evolved into an unwelcoming
February 5, 2010