What Animal Penises Tell Us About Our Own

Emily Willingham, the author of Phallacy, talks to us about everything from octopus intercourse to dusty old sex binaries.

The cover of Emily Willingham's book Phallacy appears multiple times.
Photo illustration by Slate. Photo by Penguin Random House.

The ancient spider had a teeny, tiny erection. Well, technically the 99-million-year-old Halitherses grimaldii is a spiderlike animal. But this specimen was discovered by a German scientist, trapped in sap, with, yes, an erect penis.

In Phallacy: Life Lessons From the Animal Penis, which publishes Tuesday, Emily Willingham details how, of all the thousands of arachnids and crucial discoveries that the arachnologist had made, nothing garnered the the same ecstatic attention as that erection. Willingham closes the anecdote with a declaration: “Nothing gets clicks like a story about dicks, even if it’s about a penis that’s 1.5 millimeters long and millions of years old.”

Who can resist a story about a penis? Not you, it seems. (Thank you for clicking on this very article!) Phallacy, in the penis-story department, does not disappoint. Willingham, a urology researcher turned science writer, gives readers stories about everything from the 8-foot penises attached to blue whales, to the corkscrew penises on ducks, to the rodentlike marsupials that have intercourse for hours even as they reach the brink of death.

But the examination of the differences among many, many species’ penises is just one aspect of the book, which also delves into our cultural understanding of organs. At its most compelling, the book is pointing out its title “phallacy”: that the human penis deserves to be imbued with so much power. In the scope of the animal world, the book makes clear again and again, it really isn’t much to write home about.

I spoke with Willingham about her book and what animal penises can tell us about humans’. Our interview has been edited and condensed for clarity.

Madeline Ducharme: Your book has a section about animals that detach their penises as part of reproduction. That’s sort of an ultimate fear for humans, losing a penis. People see it as emasculating. But in other animals, it’s natural part of their process, and actually how they make things happen for themselves. What did it feel like to find those contradictions?

Emily Willingham: I would point out that obviously we are not constructed so that our penises are meant to fall off. It’s not a common occurrence, but it is a common anxiety. And the last chapter [“The Rise and Fall of the Phallus”] addresses some of the psychology around that. In animals where that does occur, sometimes it is for the safety of the animal with the penis. So the example of the paper nautilus is a cephalopod, an octopus. The male is so much smaller than the female that it just kind of drops his arm off. The males have an arm that they use to deliver gametes, and this particular octopus is so much smaller than the female. The male will just kind of sneak up and drop off the arm and rush away as fast as possible so that the female doesn’t eat the rest of him.

A lot of other species are even more extreme. They’ll just give up their whole bodies to the female. That is a nutrition thing more than anything else. It’s really like, Here are some amino acids because you’re about to be charged with growing new babies.

Situating Phallacy in a particular genre is interesting to think about because it’s very much a science book, but there are also elements of psychology and even sociology and sexual politics. How have you thought about that element of this book?

It does not slot directly into any one category. I think that maybe the best way to think of it is this: It’s a book that unpacks the mix of sociocultural factors and evolutionary biology as they relate to genitalia and our human attitudes about them.

But I don’t know how you put that on a specific shelf at Barnes & Noble. That’s not exactly a label. I consider it to be a feminist book as well.

Say more about that.

The book, of course, is ostensibly about penises, which people do tend to associate with males and men. But the central chapter of the book is about how the vaginas have been left out of scientific research and the factors that feed into that, which have to do with who’s been asking the questions and how they choose to answer them over the decades of science in this area. And the fact that we’re omitting the other partner in this genital handshake means that we have a lot of questions unanswered. There’s so much more research to be done.

You can see, I mean, just in the cultural moment now, with “WAP,” right? With Cardi B and Megan Thee Stallion, people were just so appalled that somebody would be making a reference to a wet ass pussy. I don’t think we have enough out there that normalizes the discussion [of vaginas]. That applies to the research aspects as well.

People really like talking about penises. While I was reading your book, I kept thinking of a recent article in the New York Post about a man who was regrowing a penis out of his arm after losing his penis to an infection. The way that story went viral was a perfect case study for how obsessed we are with sensationalized stories about the penis.

So I have a Google alert set for penis right now, which means, every day in my inbox, I end up with a little blurb on all of the stories that mention penises. I get the obsession with penises. I mean, look at me—I just wrote a book about these things that I hope people buy so that they can learn about them.

I think that our genitalia and anything associated honestly with reproduction fascinates us. But also, I like this story about the man having a body part replaced by being able to grow another one on his arm. And it honestly doesn’t matter to me which body part it is, because the ability to regrow it is the cool part to me. I could understand that if I had a penis and it were at risk for that, even if it were just the lowest, lowest, lowest, most minuscule risk during my lifetime, it would be comforting to know that there was the possibility that I could grow one on my arm if I lose this one, right?

Recently, I think we’ve dramatically changed the way we talk about gender because of trans activists. What do those changes mean for someone like you who’s studying the way genitalia has been intertwined with essentialist ideas of gender?

In the course of my work, I’ve measured a lot of penises, and I can say that there is a continuum of sizes and other things. Anywhere you look when you’re talking about genitalia, there is a continuum. And the people who are pushing back against the right of trans people to exist are ignoring the science that says that there are continua of features, including behavioral expression and anatomical features.

Although we as humans really like to pocket things into binaries, the biological evidence does not support that. The people who insist on these dusty old binaries need to move out of the way at this point.

What do you think is our way forward in creating a world where the penis is not absolutely centered all the time?

On the human front, I think that we can redefine what we view as masculinity. I think there are multiple masculinities and ways to be masculine. There is an overarching imperative right now of an impossible masculinity that I think leaves a lot of people who seek it angry, disoriented, confused, and, for some of them, self-entitled.

I think that we could use a cultural shift from an emphasis on physical strength, on not showing certain emotions, and on the quick-strike, thrusting brilliance that everybody seems to revere and shift toward emphasizing features like empathy, kindness, and authentic expression. How do you go about that? Well, that’s a whole other book, which I’m actually currently writing. I’m writing a book on the brain next, and some of the themes in that include people who want their brains to work faster or smarter. Why do we prioritize that over our brains being more empathetic, or kinder?