The Sneaky F*cker Hypothesis

Can mimicking the opposite sex be an evolved reproductive strategy?

This article was originally published in Le Point on 05.10.2025

One of the more provocative ideas I’ve come across in evolutionary biology is the aptly named “sneaky f*cker hypothesis.” It was originally meant for alternate mating strategies in a subset of individuals of a species, such as how some males in the lizard species Uta stansburiana not only resemble females in size and coloration, but also in their behaviors. This presentation enables them to slip past larger, aggressive males and gain access to closely guarded females. Applied to humans, some theorists have postulated that ancestral males who exhibited feminine traits would have similarly been perceived by other males as being less of a romantic rival or threat in the reproductive domain. Those types of sissified men couldn’t possibly be interested in screwing their wives and girlfriends, figured the latter, so they let their guards down and, oops, that sneaker f*cker crept right in and cuckolded them.

If so, these effeminate men would have taken advantage of the ubiquitous stereotype (i.e., erroneous assumption) that gender expression is isomorphic with sexual orientation, and in doing so capitalized on an alternate reproductive strategy. As anyone familiar with the Kinsey Scale knows, sexual orientation tends to work on a sliding scale. And even in those cases where the man was primarily attracted to other males and the stereotype was true, the logic still applies. After all, we might be homosexual, but we’re not infertile. As countless closeted gay men throughout history who found themselves in lustless marriages yet still fathered children would testify, the human erotic imagination is a powerful thing… especially in the pre-electricity dark of night. And of course, identifying as exclusively gay or lesbian is just a recent cultural invention. Some evolutionary theorists believe that the modern sexual identity movement (at least, the “L” and “G” in LGBT) serves to declare oneself as a non-competitor in the reproductive arena, a way to lessen hostilities toward them. (I must admit that, over the years, I’ve occasionally found myself awkwardly easing the anxieties of potentially jealous straight men by somehow worming into the conversation that I play for the other team.)

As it turns out, some of the best indirect evidence of the sneaky f*cker hypothesis in humans doesn’t involve us craftily queer men, but instead women who display “masculine” characteristics. In a study published last year in the journal Personality and Individual Differences, psychologists Julia Hurwitz and Hannah Bradshaw examined whether women judge “masculine women” as less of mating threat.

Some previous work, they tell us, suggested this might be the case. One earlier experiment showed that, comparatively speaking, women felt less comfortable with the idea of their male partners spending time alone with another woman when she had a higher- versus a lower-pitched voice. (All participants heard the same voice; it was just digitally manipulated to achieve the pitch effect.) But Hurwirtz and Bradshaw took things a step further. In their first experiment, hundreds of female participants were presented with a fictitious text-only profile involving another woman—let’s call her “Grace”—and were then asked to rate this character on some quite catty items (e.g., “How many partners do you think Grace has had sex with in the past 12 months?”; “If given the opportunity, would Grace exploit those around her to get what she wanted”: “How likely would you be to introduce Grace to your boyfriend?” etc.).

In one version of the profile, Grace was described as preferring the company of females. “Most of her friends are other girls,” the participants read about her, and she “finds girls easier to get along with.” Another version of the profile, by contrast, stated that most of Grace’s friends were boys and she “finds boys easier to get along with.”

That information alone might be enough to raise most women’s eyebrows, according to the authors. “Women are often wary of trusting other women who claim to be ‘just friends’ with men,” they write. “This distrust is not unfounded as about half of heterosexual college students admit to having engaged in sexual activity with a cross-sex friend or at least thought about it.” We all know the ending to When Harry Met Sally. “Given the predictive nature of cross-sex friendships turning into romantic relationships and, in some cases, male partners leaving their romantic partner for their female friend,” Hurwirtz and Bradshaw explain,

it is unsurprising that women are typically wary of other women who prefer cross-sex friendships. This offers an explanation as to why women who prefer male friends often face aggression and ostracization from their female peers.

In fact, that’s precisely what they found in their first study. Those women who read the version of Grace who preferred male friends perceived her as less trustworthy, more promiscuous, and more of a risk to their own relationships.

But, wondered the investigators, might those negative feelings toward “guys’ girls” be tempered by the latter’s atypical gender expression? In other words, are masculine women who prefer men as friends seen by other women as less of a mating threat? If Meg Ryan’s character of Sally, say, hung out at a loggers’ convention, wielded a chainsaw, and wore flannel shirts and utility boots, Harry might have gotten a very different climax. To get at this, Hurwirtz and Bradshaw inserted some additional information into Grace’s made-up profile. In one version, she was described as having stereotypically masculine hobbies and interests. She was majoring in physics and wanted to be an engineer after graduation; in her spare time, she liked to hunt, fish, and watch sports. In the other version of the profile, Grace was described as having stereotypically feminine hobbies and interests. This version of Grace was studying to be an elementary school teacher, and she was into dancing, art, and gardening.

It turned out—at least in this first experiment—that such abstract stereotypes didn’t matter. Women just weren’t fans of the “guy’s girls,” period, whatever she was majoring in or liked to do in her spare time. However, the researchers did find that moderating effect on women’s judgments when the butch-like detail was made more visual. In that second experiment, Hurwirtz and Bradshaw again asked heterosexual female participants to judge a hypothetical woman, but this time, they zeroed in on an arguably more obvious marker of sexual orientation: clothing choice. Participants saw a faux social media post from a target female, let’s call her “Lina.” The post didn’t show Lina, but included a photo of a piece of clothing, either a dress or a suit, saying that this is what Lina was planning to wear at her best friend’s wedding. As with Grace from before, Lina was depicted as either a guys’ girl or a girls’ girl.

Thus, the female participants were randomly assigned to see one of four possible versions of Lina.

Meet Lina. Lina is 24 years old is planning on attending Mary and Mark’s wedding next weekend. Mark (Mary) and Lina are best friends. Most of Lina’s friends are guys (girls). She is pretty laid back and finds guys (girls) easier to get along with. Before the wedding, Lina posts a picture of the outfit she plans to wear to the wedding on social media.

Just like the previous study, when Lina was depicted as preferring males as friends (including her best friend Mark, the guy getting married), the female participants judged her less favorably than when she was said to prefer other women as friends (including her best friend Mary, the bride). This time, however, the overtly masculine cue—a woman in a suit—did render her less of a mating threat in the eyes of the female judges. Her choice of gender-bending attire was seemingly interpreted as a sign of Lina’s homosexuality: those who saw the photo of the suit were significantly more likely to perceive Lina as a lesbian than those who the dress.

Whether Lina is or is not gay isn’t really the point. People’s behavior is explained not so much by what is real, but rather by what they believe is real. And because women believe such attire denotes homosexuality—and also because men are in fact more attracted to women wearing women’s clothing, so women might presume disinterest on the part of their boyfriends and husbands—that version of Lina in a suit is in a better position to “sneak” in.

Anyway, it’s all quite speculative, and to date there’s not much direct support for the sneaky f*cker hypothesis in humans. But that’s mostly because nobody has bothered to investigate it. I’ve always thought it was plausible, especially given that both homosexuality and gender atypicality (the extent to which a person displays personality and behavioral traits more common in the opposite sex) are moderately heritable. This can also go some way in accounting for the genetic perseveration of these atypical traits, even in societies hostile to them.

One key thing to bear in mind is that none of this implies that the f*cker is trying to be sneaky by presenting with opposite-sex characteristics or has any conscious idea themselves that this is the game plan. That’s as dumb as assuming that all transwomen are wearing a “disguise” just to get into women’s bathrooms. Still, the fact that human reproduction can—and in some cases does—happen unexpectedly, with same-sex competitors failing to ascertain the threat of a gender-atypical rival, makes it a viable hypothesis.

Like what you read? Toss a tip in the jar—any amount that makes sense for you—so I can keep overthinking things on your behalf.