When is a penis not a penis? When it belongs to a female insect, say scientists investigating the animal kingdom’s first documented instance of an evolutionary genital swap. The Brazilian cave-dwelling male, Neotrogla, has been found to possess a vagina and vice versa, making this an historic case of sex organ switcheroo.
Where the discovery is truly unique is that the species’ females take on both the traditionally male role in copulation—using an “elaborate, penis-like structure... [to] anchor the female to the male”—as well as retaining their usual biological function of providing the egg. A woman’s work really is never done.
Interestingly, scientists don’t just class every animal with a penis as male: determining the sex as such comes down to how big a creature’s gametes are. The largest of these are usually provided by females (the egg), which, in Neotrogla’s case, holds. But the real game changer is that they also take the lead when it comes to mating—inserting their penis (or, more accurately, gynosome) into males for fertilization and nutrients. Given that their mating sessions can last up to 70 hours, their bedroom—well, cave—performances seem pretty darn impressive.
This reversal of intromittent organs (ordinarily part of a male organism designed to deliver sperm during intercourse) is the first of its kind to display what looks like reversed sexual selection, developed over time by females of the species competing with one another to receive “seminal gifts” from males. While this kind of natural selection is ordinarily driven by males fighting to prove themselves as the most sexually competent, “correlated evolution is detected between the female penis and male genitalia,” the study found, proof of Darwin’s theory in action.
Though pseudo-penises of this ilk have been found in other species before (in lemurs and spotted hyenas, among others), this is thought to be the first record of animal copulation in which females are responsible for penetrating the opposite sex. These gender-bending bugs may have adapted to their new roles as a result of poor resources in their habitat, the research proffers, alongside the fact copulation is particularly beneficial to female Neotrogla, who absorb nutrients through it. Their desire to mate at an increased rate, then, could be part of the reasoning behind how they have become the dominant sex of their species.
Though pseudo-penises of this ilk have been found in other species before, this is thought to be the first record of animal copulation in which females are responsible for penetrating the opposite sex.
“Typically in sexual animals, males with their many, cheap gametes benefit most from as many copulations as possible, while females see little positives to this,” says evolutionary biologist Mark Scherz. "The sexual arms race shows a reversal of pressure in this case, which is extremely unusual, as it is the female, with her barbed gynosome, freely seeking out other matings."
“It will be important to unveil why, among many sex-role-reversed animals, only Neotrogla evolved the elaborated female penis,” adds Keio University's Yoshitaka Kamimura.
Indeed, not only are these findings fascinating from a scientific perspective, but they could also yield enormous changes in how communities—both animal and otherwise—are governed in the future. With most societal structures initially put in place as a result of men’s dominance over women—particularly sexually—the notion that females could become the more physically powerful sex could entirely transform the way the sexes are perceived.
To use humans as an example, just how different would history have been if women had the power bestowed upon them that female Neotrogla have been found to possess? This biological predisposition may be less influential for insects living in the depths of a Brazilian cave than for 21st century women, but the concept of natural female dominance at its core would surely have implications at every level.
This is evidently a long way off, though. “A complete reversal in this system requires an enormous amount of evolutionary change, and the pressures and stages underlying such a transition are hard to imagine,” Scherz concludes.
But this will now be put to the test in the lab by creating Neotrogla colonies, where the extent of this evolutionary genital jumble can be answered more conclusively. “Further controlled studies of the mating system of Neotrogla species ... would provide an extremely rare opportunity to test the generality and relative importance of some hypotheses about sexual selection,” say researchers behind the report.
Three whole days of taking the lead in the bedroom, they carry the children afterwards and have the potential to transform social norms? Lady Neotroglites, we salute you.