Gay people are often asked by the curious, "When did you first realize you were gay?" In my case, I remember undressing my Superman doll – and being terribly disappointed at the result – as well as being motivated to befriend the more attractive boys in third grade. But hormonally speaking, it wasn't until I was about 14 that I first looked in the mirror and thought to myself, ah, that's what I am all right, it all makes perfect sense now.

It wasn't much of a mystery. After all, lust isn't exactly a subtle thing. Back then I derived as much pleasure from making out with my "girlfriend" as I might have from scraping the plaque from my dog's teeth. In contrast, barely touching legs with a boy I had a crush on sparked an electric, ineffable ecstasy. The point is, whether or not we like, hide or accept what we are, our true identities – gay, straight, bisexual – consciously dawn on each of us during adolescence. We all have a natural "orientation" towards sexual contact with others, and for the most part we're just hopeless pawns to our body's desires.

At least, that's what most people tend to think. But some scientists believe that there may be a fourth sexual orientation in our species, one characterized by the absence of desire and no sexual interest in males or females. Such people are regarded as asexuals. Unlike bisexuals, who are attracted to both males and females, asexuals are equally indifferent to and uninterested in having sex with either gender. So imagine being a teenager waiting for your sexual identity to express itself, waiting patiently for some intoxicating bolus of lasciviousness to render you as dumbly carnal as your peers, and it just doesn't happen. These individuals aren't simply celibate, which is a lifestyle choice. Rather, sex to them is just so ... boring.

In one recent interview study published in the Archives of Sexual Behavior, a group of self-described asexuals was asked how they came to be aware they were different. One woman responded: "I would say I've never had a dream or a fantasy, a sexual fantasy, for example, about being with another woman. So I can pretty much say that I have no lesbian sort of tendencies whatsoever. You would think that by my age I would have some fantasy or dream or something, wouldn't you? ... But I've never had a dream or a sexual fantasy about having sex with a man, either. That I can ever, ever remember."

According to Brock University psychologist Anthony Bogaert, there may be more genuine asexuals out there than we realize. In 2004, Bogaert analyzed survey data from more than 18,000 British residents and found that the number of people (185, or about 1 per cent) in this population who described themselves as "never having a sexual attraction" was just slightly lower than those who identified as being attracted to the same sex (3 per cent). Since this discovery, a handful of academic researchers have been trying to determine whether asexuality is a true biological phenomenon or, alternatively, a slippery social label that some people may prefer to adopt and embrace.

Sexual desire may wax and wane or – as many people on antidepressants have experienced – become virtually nonexistent due to medications or disease. There are also chromosomal abnormalities, such as Turner's syndrome, often associated with an absence of sexual desire. Traumatic events in childhood, such as sexual abuse, can also factor into an aversion to sex. But if it exists as a fourth orientation, true asexuality would be due neither to genetic anomaly or environmental assault; although little is known about its etiology (Bogaert believes it may be traced to prenatal alterations of the hypothalamus), by all appearances most asexual people are normal, healthy, hormonally balanced and sexually mature adults who, for still uncertain reasons, have always found sex to be one big, bland yawn.

Asexuality would therefore be like other sexual orientations in the sense that it is not "acquired" or "situational," but rather an essential part of one's biological makeup. But the story of asexuality is very complicated. For example, as discussion on the AVEN (Asexuality and Visibility Education Network) website forums demonstrate, there is tremendous variation in the sexual inclinations of those who consider themselves to be asexual. Some masturbate, some don't. Some are interested in nonsexual, romantic relationships (including cuddling and kissing but no genital contact), while others aren't. Some consider themselves to be "hetero-asexual" (having a nonsexual aesthetic or romantic preference for those of the opposite sex), while others see themselves as "homo-" or "bi-asexuals." There's even a matchmaking website for sexless love called asexualpals.com.

Yet many asexuals are also perfectly willing to have sex if it satisfies their sexual partners; it's not awkward or painful for them but rather, like making toast or emptying the trash, they just don't personally derive pleasure from the act. Others insist on being in completely sexless relationships, possibly with other asexuals. Thus, while many asexuals are virgins, others are ironically even more experienced than your traditionally sexual friends. Thus, on the one hand there seems to be a sociological issue of people of a marginalized sexual identity gathering steam and beginning to form an identifiable community. On the other hand, there remains – to me – the more intriguing biological issue of asexual essentialism; that is to say, is it really possible to develop "normally" without ever experiencing sexual desire toward any other human being on the face of the earth?

If even a sliver of the asexual community has truly never experienced arousal, then this would pose fascinating questions for our understanding of human sexuality and evolutionary processes.

I still have a lot of questions. Scientists have just scratched the surface in studying human asexuality. You can count the number of studies on the subject on one hand. Does asexuality, like homosexuality, have heritable components? If some asexuals masturbate in the absence of sexual fantasy or porn, then what exactly is it that's getting them physically aroused? (And how does one achieve orgasm – as some asexuals apparently do – without experiencing pleasure?)

Also, if you're on board theoretically with evolutionary psychology, almost all of human cognition and social behaviour somehow boils down to sexual competition. So what would the evolutionary psychologist make of asexuality? If sex is nature's feel-good ruse to get our genes out there, is there actually a natural category of human beings that is immune to evolution's greatest gag?

The only good way to solve the riddle is also a bit unsavoury. But unless psychological scientists ever gather a group of willing, self-identified asexuals and, systematically and under controlled conditions, expose them to an array of erotic stimuli while measuring their physical arousal , the truth of the matter will lie forever hidden away in the asexual's pants.

Loading... Loading... Loading... Loading... Loading... Loading...

Jesse Bering is a research psychologist with Queen's University Belfast. He writes about obscure aspects of human behaviour for Scientific American.