Tag Archives: Patricia Brennan

The Complexity and Variety of Animal Vaginas

Laurie and Debbie say:

female duck’s reproductive tract; an elaborate spring-shape that spiraled in the opposite direction as the male’s member. Art by Catherine Delphia.

We were completely delighted with Rachel Gross’s article in Smithsonian,“Why Have Female Animals Evolved Such Wild Genitals?” The article, which is adapted from Gross’s new book, Vagina Obscura, starts with ducks. Duck sex is particularly violent and nonconsensual:

Ducks tended to mate for at least a season. However, extra males lurked in the wings, ready to harass and mount any paired female they could get their hands on. This often leads to a violent struggle, in which males injure or even drown the female. In some species, up to 40 percent of all matings are forced. The tension is thought to stem from the two sexes’ competing goals: The male duck wants to sire as many offspring as possible, while the female duck wants to choose the father of her children.

Colombian biologist Patricia Brennan, featured in Gross’s piece, was watching a duck mating and started getting fascinated first with duck penises, which led her to a deep study of duck vaginas, which in some cases seem to have evolved.

… to make the male’s job harder: It was like a medieval chastity belt, built to thwart the male’s explosive aim. In some cases, the female genital tract prevented the penis from fully inflating, and was full of pockets where sperm went to die. In others, muscles surrounding the cloaca could block an unwanted male, or dilate to allow entry to a preferred suitor.  ,,, Whatever the females were doing, they were succeeding. In ducks, only 2 to 5 percent of offspring are the result of forced encounters.


Dissected duck vagina (left) and corresponding penis (right), spiraling in opposite directions.

But it’s not just ducks, and it’s not just birds.

A world opened up before Brennan’s eyes: the vast variety of animal vaginas, wonderfully varied and woefully unexplored. For centuries, biologists had praised the penis, fawning over its length, girth, and weaponry. Brennan’s contribution, simple as it may seem, was to look at both halves of the genital equation. Vaginas, she would learn, were far more complex and variable than anyone thought. Often, they play active roles in deciding whether to allow intruders in, what to do with sperm, and whether to help a male along in his quest to inseminate. The vagina is a remarkable organ in its own right, “full of glands and full of muscles and collagen, and changing constantly and fighting pathogens all the time,” she says. “It’s just a really amazing structure.”

To center females in genitalia studies, she knew she would need to go beyond ducks and start to open “the copulatory black box” of female genitalia more broadly. And, as she explored genitals, from the tiny, two-pronged snake penis to the spiraling bat vagina, she kept finding the same story: Males and females seemed to be co-evolving in a sexual arms race, resulting in elaborate sexual organs on both sides.

First, are we surprised that penises have been extensively studied and vaginas have been ignored? Spoiler warning: Nope.

Second, it gets even more complicated and intriguing. Brennan teamed up with Dara Orbach, a Canadian researcher studying dolphin genitalia. They established that porpoise vaginas function much as duck vaginas do, as control devices and rape prevention.

And then there’s pleasure:

… in the middle of their dolphin vagina dissections, the scientists stumbled across something else: a massive clitoris, partly enfolded in a wrinkled hood of skin. While the human clitoris has long been cast (erroneously) as small and hard to find, this one was virtually impossible to miss. When fully dissected out, it was larger than a tennis ball. “It was enormous,” Brennan says.


Female dolphins have been seen masturbating by rubbing their clitorises against other dolphins.

That dolphins would have a well-developed clitoris was no surprise. Brennan and Orbach both knew that these charismatic creatures engage in frequent sexual behavior for reasons like pleasure and social bonding. Females have been seen masturbating by rubbing their clitorises against sand, other dolphins’ snouts and objects on the sea floor. Yet while other scientists had guessed that the dolphin clitoris might be functional, no one had actually tried to figure out how it worked.


vaginas of cetaceans, pinnipeds and manatees.

Why don’t we know this? Well, Charles Darwin is emblematic of the problem:

when it came to genital evolution, Darwin left much to be desired. The father of evolution generally eschewed talking about genitals, considering their main function to be fitting together mechanically, as a lock fits into a key. Moreover, he characterized female animals almost universally as chaste, modest and virtually devoid of sexual urges. In his lesser known writings, he described a world in which females honored their “husbands” and kept “marriage-vows.” Although he observed a few counter-examples—i.e. females with several “husbands” or those that seemed to pursue sex for pleasure—he steered clear of them, likely out of a sense of Victorian propriety.

Working against Darwin and his generations of male disciples, evolutionary biologist Joan Roughgarden, author of the 2004 book Evolution’s Rainbow: Diversity, Gender, and Sexuality in Nature and People, examines same-sex interactions and solo pleasure in various species, including bonobos, close genetic relatives of humans.

Roughgarden, a transgender woman who transitioned a few years before writing her book, could see the damage more clearly than most. Sexual selection theory “denies me my place in nature, squeezes me into a stereotype I can’t possibly live with—I’ve tried,” she writes in Evolution’s Rainbow.

Gross concludes her excerpt with a rallying cry:

“Biology need not limit our potential. Nature offers a smorgasbord of possibilities for how to live,” Roughgarden writes. Rather than chaste Victorian couples marching two by two up the ramp into Noah’s neat and tidy ark, “the living world is made of rainbows within rainbows within rainbows, in an endless progression.”



Thanks to Shayin Gottlieb for the pointer.

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