Suzana Herculano-Houzel


Human beings find it incredibly difficult to accept that they are animals. Special in many ways, it’s true – but an animal nonetheless. We like documentaries about the biology of monkeys and lions, but we find it hard to accept that nature can sometimes have a determining influence on our behavior too. We even believe that our hair, eye and skin color are biologically determined. But when it comes to complex behaviors, such as sexuality, things change.

When the first indications emerged in the 1980s that the attraction we feel for one sex or the other is biologically determined, there were demonstrations by homosexual groups both for and against. Some groups welcomed the findings as proof that homosexuality is neither a disease nor a choice, but inevitable biology. Others, on the other hand, felt that their right to be homosexual by choice had been violated. But they shouldn’t.

Sexual preference, that physical attraction one feels for one sex or the other, is in fact determined biologically, and right from the start of life, still in the womb. Genes and hormonal factors influence the formation of the brain regions involved, which will demonstrate their preference later, when they mature in adolescence and respond with excitement to the pheromones of one sex or the other – sometimes the same sex, often the other. On the contrary, there is no evidence that the social environment influences human sexual preference. Around 10% of men and women are attracted to partners of the same sex, and the figure doesn’t change between people raised by a father and mother, two fathers, two mothers, with religion or without it.

Of course, what each person does with their sexual preference is something else, a matter of choice, which unfortunately must take into account all the social and psychological difficulties that discrimination brings. Nature does not rule alone, and it is indeed possible to choose socially to display heterosexual behavior, for or against one’s biological preference. But, thankfully, the brain can do better than that. If 100% of the population has an innate and biologically determined sexual preference, then we are all equal in this respect – even if most of our brains respond to pheromones from the opposite sex. It should be simple, then, to choose to accept this biological preference, ours or others’, whatever it may be. A great choice.

Originally published in Folha de São Paulo on July, 2006.

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