Why Did Scientists Wait So Long to Study the Snake Clitoris?

The delay is representative of a major problem in biology: Female and intersex animals are understudied compared with their male counterparts

Common European Adders
A male (silver) and female (brown) common European adder meet prior to mating. Scientists are just beginning to understand female sexual anatomy in snakes. David Tipling / Education Images / Universal Images Group via Getty Images

Few biologists thought the snake clitoris was anything worth studying. For more than a century, reptile researchers have spilled plenty of ink about the anatomy and function of the sexual organs of male lizards and snakes, structures known as the hemipenes. Meanwhile, the female equivalent, hemiclitores, were not described in truly scientific detail until 1995. Even less was known about the anatomy of intersex reptiles. Any structure other than the male hemipenis was assumed by men in zoological fields to be vestigial or to only act as additional stimulation for male reptiles. “You often see scientists make assumptions that female genitals are simple, uniform and generally uninteresting,” says journalist and Vagina Obscura author Rachel E. Gross, “when the reality is that no one has systematically looked.”

The first attempted description of hemiclitores in lizards and snakes dates all the way back to 1886, when they were described as little more than “shallow invaginations” on the reptiles. Decades of silence followed, even as biologists continued to pontificate on the significance of hemipenes in male lizards and snakes, closely related reptiles collectively called squamates. A 2014 review of studies focused on animal genitals, for example, found that researchers focused on male genital anatomy alone in more than half of the sample studies between 1989 and 2013, with less than 20 percent considered female genital anatomy alone during the same period. Even more recently, less than a decade ago, biologists continued to insist that the hemiclitores of female lizards and snakes served little to no function, just as experts on human anatomy long ignored the clitoris and assumed that whatever biological relevance it has is secondary to cisgender men’s anatomy. As University of Adelaide biologist Megan Folwell and colleagues noted in an Integrative and Comparative Biology paper last year, however, the anatomy and behavior of male snakes is only half the story—if even that. The anatomy of female and intersex reptiles is essential to understanding their behavior and even telling the differences between species.

The lack of direct research on female and intersex squamates has only created confusion. While scientists have completed a handful of studies about hemiclitores in lizards, Folwell and co-authors point out, various reports of the same structures in snakes were misidentified hemipenes, anal glands and other body parts, with some authors uncritically citing past references without double-checking the anatomy of the reptiles for themselves. Given that the literature on snake hemiclitores and the anatomy of intersex snakes is so sparse, Folwell and co-authors concluded that no one had adequately identified whether female snakes even possess hemiclitores at all. The snakes should have had the structures—especially because they are squamates, like lizards—but no one had found proof positive.

But Folwell and colleagues had an ace up their sleeve. Soon after they released their biological review, the researchers published “First evidence of hemiclitores in snakes” this past December in Proceedings of the Royal Society B—more than 120 years after the complementary male structures were detailed. By studying the external and internal anatomy of the reptiles, CT scans and investigation of the snakes’ tissues, the biologists identified hemiclitores in at least nine species of snakes from four different families, including vipers and pythons. Unlike the hemipenes of males, the researchers found, the hemiclitores remain inside the body and can be found behind the single orifice, or cloaca, along the tail. Some species have larger hemiclitores than others, but, finally, after decades of confusion, Folwell and co-authors provided a clear look at what other experts had only guessed at.

If any upside exists to the mountain of research carried out on male reptile anatomy, it’s that past studies gave Folwell and colleagues plenty of information to compare their new findings against. Snake hemiclitores are not just modified scent glands or smaller versions of hemipenes, the authors found, and instead are specialized structures that have a role to play in the way snakes mate. Hemiclitores differ between snake species, for example, which suggests that the size, shape and placement of the organs are influenced by evolution as much as those of male snakes and can’t be written off as insignificant. The subtle differences are important enough that the anatomy of snake hemiclitores might help researchers distinguish between closely related snake species, as well as better identify intersex snakes that are often miscategorized by experts. And the hemiclitores are important to the snakes themselves. “The presence of nerve bundles and single nerve fibers in the hemiclitores may be indicative of tactile sensitivity, similar to the mammalian clitoris,” the authors write, which probably means that all the rubbing and looping snakes do while mating probably feels good for the female snakes.

Snakes are not the only animals to be affected by sexism in science, of course. But this bias is not going unchallenged. Biologists are questioning what was always assumed about the anatomy of female and intersex animals and how sexism in science has skewed how we understand nature. “If we look at the wildly diverse world we call nature,” says Gross, who previously worked for Smithsonian as a science editor, “we find dominant females, plum-sized clitorises, same-sex couples, male-male-female triads, asexual reproduction, male-to-female transformations and so much more.” All of these phenomena, and more, are part of understanding the world around us on its own terms and how other species don’t always fit neatly into our cultural perceptions.

The sexist beliefs people had about women and their space in society spilled over into views of nature, what New Mexico State University biologist Teri Orr summarizes as “the sentiment that females are the vessels into which the male component, genital or ejaculate arrives” rather than organisms to be understood fully in their own right.

Historians of science are well-versed in the ways fields traditionally filled with men have misunderstood and even demonized the bodies of other sexes and genders. Generations of zoologists have even created a sex bias in museum collections, with male animals more often used in research collections than females—especially in species where males are brightly colored, have prominent horns or are otherwise flashy. A 2019 survey found that specimens used to set the standard for a species’ attributes—called a type—were only 27 percent female for birds and 39 percent for mammals. Even our understanding of ancient and extinct life is affected. Another 2019 study found that fossils of ancient bison, brown bears, mammoths and other Ice Age mammals in museum collections and displays are mostly male. Much of what we know about life on Earth has been distorted by generations of men studying mostly male specimens and paying little attention to the biology of other sexes.

Imbalances in collections and research focus have allowed non-male animals of various sorts to be brushed aside—and not only among reptiles. Just as snake hemiclitores were ignored in favor of male organs, so have the “os clitoridis” or clitoral bones of many mammals such as rodents and primates. “I would suggest that the baculum,” or bone in the penis of some mammals, “has been described in countless rodents while in female the baubellum,” or clitoral bone, “is almost entirely ignored,” Orr says, with some experts in the field unaware that a female equivalent exists at all. Research onto this part of the mammal skeleton is scant, and a 2016 study carried out by a team of men proposed that the broad variation of clitoral bone shapes hints that the structure doesn’t have any function. Orr identifies such hypotheses as underlying sexism, in which male anatomy is viewed as mysterious and interesting, while female anatomy is assumed to have less of a role or function. In the case of the baubellum, as with the hemiclitores in snakes, it may be that the variations have more to do with differences between species or mating-related behaviors that have likely gone unnoticed or unstudied.

Human biology isn’t immune from such misapprehensions, either. Many ideas about our own bodies that are treated as common knowledge actually have more to do with sexist cultural projections than reality, such as the cartoon image of sperm rapidly swimming toward an egg simply bobbing in place. “Perhaps this is why it is only recently that female scientists have started to uncover how sperm are actively moved by the female,” Orr notes, with the sperm’s contribution to fertilization being minimal by comparison—a realization that’s come from studies of humans, rodents and other animals. Even more broadly, Gross adds, female anatomy is often simplified to represent the “lock” in a “lock and key” arrangement or with imagery of the female body being “the field on which males compete.” When scientists look at nature with the idea that males are active, females are passive, and sex is binary, they are prone to repeatedly making mistakes.

Sexism is only part of the story, however. People of all genders are prone to internalizing and repeating biological fallacies, because we are rarely familiar with how such knowledge was assembled in the first place. Against that background, Gross notes, researchers from varied backgrounds are often best placed to question what has long been taken as ironclad truth. “It takes those who have been historically marginalized by science, such as women, LGTBQ people and people of color, to believe those questions are worth asking in the first place,” she notes.

The way scientists study and understand other species is always carried out in the context of who they are and where they are coming from. The greater the diversity of scientists, the better society en masse can ascertain whether something is real or a mirage.

Mistakes and misunderstandings about the lives of other species are often reflections of what we don’t yet comprehend about ourselves. Gross recounts a story passed on to her by biologist Patty Brennan, who was studying what happens during pregnancy to the vaginas of sharks known as dogfish. Brennan sifted through the literature on human pregnancy to get some background information, Gross recalls, but Brennan could find little information on what happens to vaginas in humans during pregnancy. “The idea that we could research such a common anatomical experience in sharks before doing so in humans,” Gross says, “is pretty revealing.”

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