Is homosexuality "natural"?

Gay marriage. Strangely, this opportunity to celebrate a loving unity has emerged as one of the most divisive issues of our time. While most people against gay marriage cite religious reasons, some have argued that homosexuality “ain’t natural”, implying that this sort of behavior does not exist in nature. We will leave it to others to debate the religious arguments, but science has made it abundantly clear that homosexuality is perfectly natural.

In the beginning, there was no sex. That’s because in the beginning, there was no Barry White. Actually, our most ancient, single-celled progenitors simply had no need for sex since they could just split right down the middle to make a daughter cell. Aside from an occasional mistake during DNA replication, asexual reproduction results in a veritable clone of the parent cell. While no fun, it is an efficient system on an individual level – so efficient that asexual organisms like bacteria continue to dominate this world in terms of abundance.

It’s only love doing its thing.

But if everyone were a literal “chip off the ol’ block”, it leaves little room for diversity to appear rapidly within the species. Sex may have evolved because it is a powerful means to diversify the species’ portfolio; the more diverse the members of a species are, the more likely that some could survive a catastrophic event, such as a viral infection that wipes out 90% of the population, or the release of The Matrix sequels, which bored countless moviegoers to death. Sex creates diversity among the species because instead of generating clones, the offspring are a blend of two genomes. Thus, there is a greater chance that the children will possess unique characteristics, some of which may have never been seen before in that population. This diversity can give sexual organisms an advantage when battling parasites or predators, an idea known as “The Red Queen Hypothesis”.

If sex is such an advantage for a species, than why is there homosexuality? Scientists do not yet know the definitive answer to this question, but some plausible ideas have been put forth. First, we are a product of our genes. Our genes largely govern the types and amounts of hormones and hormone receptors coursing through our veins. Our genes contain the blueprint to build brain structures such as the hypothalamus, which is known to control sex hormone release and behavior. Variations in these genes could conceivably alter a person’s biochemistry of attraction – they could be attracted to members of the same sex, both sexes, or have no attraction to either sex (asexual). It is also highly likely that epigenetic factors from the environment interplay with our genes to create sexual preference. Whatever the case may be, we do not get to pick our genes or our biochemistry. Just like eye color or the ability to curl one’s tongue, people have absolutely no choice in their sexual orientation.

One thing that is undeniably certain is that homosexuality is not exclusive to humans. In fact, it is EVERYWHERE. All sorts of animals across different kingdoms – from insects to primates – exhibit homosexual behavior. Let's review some examples.

As any sheepherder will tell you, as many as one in ten rams are gay.

Sorry, wrong "Rams"!

How about penguins? Yes! There was even a famous story a couple years ago about two gay penguin males in a zoo, Buddy and Pedro, who became “gay penguin parents”. Proving that two gay dads can successfully raise a family, these king penguins teamed up to incubate an egg and bonded as any heterosexual family would have done.

A children’s book based on the two penguin dads is available.

Homosexual behavior is in the air. A variety of birds, such as the Laysan Albatross, and insects, such as flour beetles, have been observed in same-sex pairings. Finally, come with me to the sea of love and you’ll find homosexual activity in bottlenose dolphins. 

As mentioned before, homosexuality is also observed in other primates such as our close cousin, the bonobo. Bonobos are so into free love that they have even been referred to as “the hippie ape”. Both males and females are bisexual and use sex as a greeting and to resolve conflict. This is also why they make “Planet of the Apes” movies and not “Planet of the Bonobos”.

Why would species do this? Isn’t the emergence of homosexuality akin to draining the gene pool since reproduction will be reduced? The answer may be all about balance. Sometimes a species proliferates faster than resources can be replenished, which could lead to extinction. Homosexuality has been postulated by the Pulitzer Prize winner sociobiologist E.O. Wilson to be a means of population control, bringing the species into biological balance with the resources in its environment. While there is evidence that homosexuality has a biologic or sociobiologic component, the degree to which these play a role is still being defined.

Contributed by:  Bill Sullivan

Follow Bill on Twitter.

Van Houdenhove E, Gijs L, T'sjoen G, & Enzlin P (2014). Asexuality: A Multidimensional Approach. Journal of sex research, 1-10 PMID: 24750031

Rice WR, Friberg U, & Gavrilets S (2012). Homosexuality as a consequence of epigenetically canalized sexual development. The Quarterly review of biology, 87 (4), 343-68 PMID: 23397798