For as long as it has been in society's crosshairs, homosexuality has been part of a very simple debate: is it natural or is it a choice? The question of whether it was helpful to a species was never considered; after all, do we question whether it's better for humanity to boast a specific eye color or personality? Now however, a new study has revealed that the trait can be very helpful to a species, and you won't believe how.

Just What IS Homosexuality, Really?

Before the 'big reveal,' it's probably important to point out that being homo- or bi-sexual isn't exclusive to humans and great apes. It's not even exclusive to mammals. Back in 1999, researcher and author Bruce Bagemihl outlined homosexual behaviors in about 500 extensively observed species, including bison, seagulls, dolphins, cats, salmon, and even emu, in his book Biological Exuberance: Animal Homosexuality and Natural Diversity.

In 2006 researchers from the Norwegian Natural History Museum at the University of Oslo updated that list, naming a stunning 1,500 animals that were regular practitioners of same-gender sex. The question then became, "so they do it, but what for?" After all, species growth certainly won't benefit from same-sex copulation, as anyone familiar with 'the birds and the bees' could tell you.

A 2006 study of frequent female-on-female sexual practices among Japanese macaque monkeys came to a very simple conclusion. Looking at all the inventive positions and apparent excitement of the animals, a team of four experts basically said, "they do it because it feels good." (Scroll to read on...)

Humans can sometimes forget that many animals enjoy sex just as much as we do, and will actively seek out sexual gratification, even if doesn't necessarily mean a child will be born. However, the same argument implies that when it's time to pop a baby out, each and every mature female will still seek out a male mate and become a mother. In that sense, could it be argued that they are actually bisexual?

The trouble is, researchers can't get inside the head of an animal, especially one as complex as an old-world monkey. It remains very difficult to determine if these female macaques are actually sexually attracted to one another, or if they simply get bored.

We can say that fruit flies, however, definitely do a lot less thinking.

The Thing About Fruit Flies

Like many of the Earth's simplest insects, the fruit fly has long been seen more like a tiny thing on autopilot than a conscious creature. Sure, it makes what we could call "decisions" - fly here, eat that, mate that, die here - but for researchers, those decisions have always been painfully predictable. That, along with their simple genetic code and biological design, has long made them an ideal model for research.

And yet, despite their predicable 'programming,' even fruit flies engage in same-sex sexual behaviors (SSB). To find out why, a team of researchers from the University of St Andrews launched an investigation using both genetic and behavioral testing.

First, the team screened SSB flies for common genetic information that purely heterosexual flies lacked. A study of an unprecedented 800 gay men recently ran similar testing, identifying several key genetic drivers that would at-least nudge a person toward homosexuality. It's important to note then, that this latest work runs under the same assumption: that homosexuality can have natural, genetic origins.

The argument can be made that some of these flies simply were mistaken during their homosexual encounters. However, it was male flies that frequently engaged in traditional courtship behaviors - such as licking, singing or attempted mounting - with another male that the researchers paid special attention to. A fly may mix up the genders of those around them on occasion, but not several times over. (Scroll to read on...)

It's a Gay Day for Fruit Flies

The team identified several genetic lines of flies that either consistently showed high levels of SSB, or low levels of SSB and then divided. They then interbred these groups and examined the offspring.

And here's where things get interesting.* The researchers determined that while it was difficult to tell if all SSB genes led to more SSB behavior in a male offspring, most female offspring associated with these genes boasted a higher rate of successful reproduction.

That is to say, the daughter of a homosexual male often wound up having far more children of her own, compared to the daughter of a "straight" male fly.

This, the researchers argue, could explain why homosexuality remains a common trait in so many species. Despite the fact that its existence may reduce reproduction in one generation, it may actually result in swelling numbers in the generations that follow - actually aiding the species while simultaneously ensuring that SSB genes stick around.

And that's an exciting revelation for experts, as it helps bolster the claim that - contrary to some assertions - natural selection would NOT weed out homosexuality if it is a natural trait. In fact, it may even encourage it.

Of course, it's important to remember that this is certainly no nail in the coffin for the homosexuality debate. While fruit flies are relatively simple creatures, humans are certainly not, and there are plenty of other factors to consider. Still, this study should be welcome food for thought for anyone looking for a bigger picture - and all from some very tiny flies.

I've said it before, but nature can be pretty darn surprising, and always in the best ways.

*Results of the study were published in the Proceedings of the Royal Society: B.

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