The Gender Gap Exists in Animal Genitalia Research, Too

And it's harming evolutionary research.

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May 12 2014, 6:27pm
Image: Shutterstock

The theory of evolution hinges on but one thing: the ability to better pass your genes on to the next generation. Survival is an important part of that, but reproduction is the process by which it happens. By that logic, it makes tons of sense for scientists to study how animals reproduce—so why are scientists spending most of their time studying just penises?

We’ve got a gender wage gap, a gender gap in science jobs, a gender gap in Bitcoin, and now, a gender gap in the study of animal genitalia. A new study published in PLOS Biology found that, in studies that look at reproductive organs, there’s an overwhelming gender bias: Nearly half of all studies that looked at animal genitalia focused on males only; 7.7 percent focused on females only, and 43.7 percent focused on both.

That’s a problem, especially considering that the trend has gotten more pronounced over the past decade or so, even after an influential 2004 paper found that females play an incredibly important role in sexual selection.

Image: PLOS Biology

So, what gives?

Part of it is that penises are often much easier to study, especially in insects, according to Malin Ah-King of Gemany’s Centre for Gender Research, the study's lead author. We’ve learned that penises, especially in the animal kingdom, come in all shapes, sizes, and levels of weaponization, but, for the most part, they tend to be external organs that can be easily studied. Not so with the female genitals of tiny organisms, such as insects. In order to study those females, more complex dissections or CT scans are needed.

“In many animals, especially insects, which are often studied as dried specimens in collections, the male genitalia (which often stick out and are hard and retain their shape even after the specimen has dried up) are much more easy to study than the soft, invaginated, and (after preservation) shriveled female parts,” Menno Schilthuizen, author of Nature’s Nether Regions, wrote to me in an email. If you haven't yet, check out the fascinating Q&A he did with Motherboard contributor Lex Berko a couple weeks ago.

“Malin seems to downplay this explanation by saying that with modern techniques this should not be an obstacle. Sure, it should not be, but to many researchers, it is, and may be part of the explanation for the bias,” he added

Then, there’s the nature of scientific research in general. It’s very rare for a scientist to embark on a completely new strand of study. Often, there are papers that have already studied the male role in reproduction and evolution, so further studies serve to expand on that research—and continue to ignore the female’s role.

Finally, and perhaps most obviously, there’s the disproven stereotype that, in general, males are the “dominant” gender, even in the animal kingdom, where we’ve seen all sorts of crazy things. Traditionally, scientists have suggested that males compete with other males for dominance and for sexual partners, which can lead to rapid evolution of the male genitalia, while the female genitalia more or less sits there, unchanged. That has been proven false in many, many instances, but still the stereotype persists. 

“The theoretical assumption that male components of sexual selection are more important than female ones may be one explanation for the biased focus on male genitals in the field,” Ah-King wrote. Even today the dominant paradigm in the field holds assumptions that steer researchers toward focusing on male subjects more than females: of higher male variance in reproductive success, of males gaining more by multiple mating than females, and of females being choosier and less eager than males.”

One interesting thing to note is that the gender of the researcher doing the study didn’t appear to matter (though, as we see all too often in science, there were far more male researchers studying this than female researchers doing the same). 

No matter the reason for the bias, evolutionary biologists simply need to do a better job of studying the evolution of both male and female genital evolution. Every time that someone does a decent study that includes females, we find that female genitalia are at least as evolved as males: Female mallard ducks have “elaborate and convoluted vaginas” to accommodate those insane corkscrew penises you’ve seen before; female fruit flies have evolved adaptations to male penis spines; water striders have a “genital shield” that protects from “forced copulation by males; some insects have, essentially, reversed sexual organs.  

We’re quickly learning that the world of animal genitals gets more and more intricate the more we study both sexes, so it’s time to stop focusing on males alone, in order to get the bigger picture.

“The study makes us aware that we need to clean up our act and make sure that we do not allow ourselves to reinforce that male-genital bias with every new study we do,” Schilthuizen said. “Let's take the trouble to do those dissections and micro-CT scans and, where necessary, invent new terminology for female genitalia—the science will benefit from it.”