Homosexual Beetles Increase Chances of Reproducing?

For decades, homosexual behavior observed in male flour beetles has perplexed animal behaviorists.  The beetles, 3-millimeter long Tribolium castaneum, found in temperate areas, have been the focus of several studies in an attempt to solve the mystery of their homosexual tendencies.  From an evolutionary perspective, homosexuality is counter-productive to the species’ fitness, though it has been observed in many animals, including insects, penguins and primates.  There are several theories to explain the phenomenon.  Some scientists believe the males copulate with other males as practice before attempting to mate with females.  Others suggest that the males need to get rid of old, less effective sperm before mating with females.  Other scientists have even suggested that homosexual behavior is a way of exerting social dominance over other males.  A new study threw a wrench in these hypotheses.

The study, headed by evolutionary ecologist Sara Lewis, of Tufts University, began by marking male and female flour beetles.  The team tracked their individual sexual exploits, while monitoring the paternity of any offspring born in the group.  Their results showed that homosexual encounters did not improve the male’s sexual success with females, and found no connection between homosexuality and social dominance.  What they did find came as a shock:  the sperm leaked by one male onto another during homosexual encounters could actually inseminate a female who later copulated with the second beetle.  In other words, a beetle could inseminate a female without directly breeding with her.  This proves the beetles’ homosexuality a reproductive benefit, as the males can inseminate females without spending the energy necessary for finding and mating with them.  The results were so surprising to the researchers, that the experiment was repeated several times, with the same results.  This research is a triumph for evolutionary biology, as homosexuality in animals is often written off as confusion, and is rarely explored objectively.  

Update: (11/11/2008)

Though zoologists often avoid the topic for fear of crossing into political debate, the fact is that homosexuality has been observed all across the animal kingdom, in captivity and in the wild.  It has been observed in insects, birds, sheep, fruit bats, dolphins, apes and monkeys.  At the New York Central Park Zoo, two male penguins named Ray and Silo have been displaying classic pair bonding behavior for 6 years.  This behavior includes entwining of necks, mutual preening, flipper flapping, and mating, while ignoring females.  In the wild, some male ostriches only court their own sex, and pairs of male flamingos have been known to build nests and raise foster chicks.  Homosexuality in females has been observed in Japanese macaques, though scientists are still unclear on the reason.  It is possible that these relationships have an unknown adaptive pay off, or they could just enjoy it.  In bonobo apes, a close relative of humans, 75% of all sex is non-reproductive, and almost all bonobos are bisexual.  Scientists believe that the bonobos use sex to resolve conflicts in the group.  Temporary homosexual partnering in immature dolphins is believed to be a way to form lifelong bonds.  Explaining he mystery of homosexuality in animals has only begun.  Robin Dunbar, a professor of evolutionary psychology, argues that homosexuality may be a by-product of something else and hold no evolutionary function at all. 

Homosexuality Debate

Bonobo Apes

-Jane de Verges (8)