JUST DISCOVERED: Female Snakes Have Two ‘Naughty Bits’… but that’s exactly what I expected

...every scientific discovery isn’t earth-shattering

Being a biologist is sort of fun. You can talk about taboo subjects without offending anybody because, well, you’re a scientist. You can even use the real words for “private parts” and nobody cares… although I prefer Monty Python’s term “naughty bits.” I guess I’ve never really grown up.

In any event, several weeks ago, I came across an article in the Guardian entitled “Snakes have clitorises: scientists overcome ‘a massive taboo around female genitalia’.” Turns out, the article is about a research paper published by a PhD student at the University of Adelaide. It seems that she identified and described paired clitorises in several species of snake.

As a research scientist, I’m the first to admit that a lot of time and money is squandered on weird research, for instance, determining whether scorpions run slower when they’re constipated, analyzing depictions of ritual enemas on ancient Maya pottery, or trying to make a functional carving knife out of frozen human poop. (Is there a theme here?) However, I do think that anatomy research is really interesting because I teach physiology, and anything I learn about anatomy helps me better understand how physiology works. So, I’m down with the snake article!

However, let’s be honest. Most of us academics — me included — are a bit nerdy. We don’t make a lot of money, we can’t afford cool clothes (even if we knew where to buy them), and we’ve spent years working alone in laboratories mostly unaware of our waning social skills. So, when we discover something that’s pretty interesting (at least to us), we’re not only excited, we need to make a big deal out of it. Everybody wants to feel important once in a while. And, that’s what happened to the snake naughty bits story.

Apparently, after the original article was published, the Guardian got wind of it, and their science reporter began ginning it up. That’s understandable. Science writers want you to read their articles, and young scientists want to be promoted.

However, the story got way overblown. The reporter even quoted the student as saying, “…female genitalia across every species is unfortunately still taboo.” The University of Adelaide PR Department (which got its headline wrong, by the way) said this was “a first-of-its-kind study,” and an Associate Professor crowed, “This discovery shows how science needs diverse thinkers with diverse ideas to move forward."

Wow, I think everybody got a little over excited about snake clitorises!

Frankly, I found it hard to believe that no one else had ever studied female snake naughty bits. And, I didn’t believe that I was the only one who wasn’t surprised that female snakes have two.

So, being the nerd that I am, I had to check. First, I searched the biological journal database (BioOne) through my college library. I found 1,163 articles on “female animal genitalia.” When I looked it up in Google Scholar, I found 228,000 articles, over 16,000 of which were published in the last decade. I even found 6,650 scientific papers using the search term “snake clitoris.” So, if there’s a “massive taboo” out there, it isn’t working. It seems that a lot of scientists like to study animal naughty bits.

Even though the snake study wasn’t the “first-of-its-kind” or particularly earth shattering, I still thought it was interesting, but unsurprising. So, why wasn’t I surprised that female snakes have two clitorises? Well, because male snakes have two penises. They’re called hemipenes. And, we’ve known about them for over a century. In fact, people usually cite E. D. Cope as the first to have described hemipenes in lizards and snakes in 1896, although Cope, himself, cited two earlier 19^th century anatomists (Hermann Stannius and John Gray), and hemipenes were mentioned by Hans Gadow in 1887. It looks like scientists have been studying reptile naughty bits for quite a while.

Anatomically speaking, hemipenes are paired (side-by-side), intromittent organs joined at the base (as if you were making a peace sign with your middle and index fingers). As you might imagine — if you have a wild imagination — these paired penises vary quite a bit in size, shape, and ornamentation. Some are smooth and unadorned. Others are quite ornate and reminiscent of medieval weaponry with elaborate barbs, hooks, spines, and petal-like calyces on the tip. Usually, you don’t see them because when they’re not being used, they’re inverted and tucked away in a pouch near the animal’s tail.

So, here’s the connection between hemipenes and hemiclitorises. By the way, a lot of this applies to you, too.

In mammals (that’s you), birds, and most reptiles, the genitals develop from two populations of progenitor cells that originate on the left and right sides of the embryo near the clusters of cells destined to become its hind legs and tail. (Yes, when you were an embryo, you had a tail, too.) As the embryo develops, these two populations of cells move toward the midline and form a pair of genital buds.

Now, here’s the tricky part. If the two genital buds stay separate — as they do in snakes and lizards — each will form an embryonic phallus, so the animal will have two. These phalluses develop into either a pair of penises or clitorises depending on the levels of circulating male and female sex hormones. So, because penises and clitorises develop from exactly the same embryonic structure, it should not be a surprise that if boy snakes have two, girl snakes will have two (and vice versa).

On the other hand, in mammals (like us), and birds, crocodiles and turtles, when those two pools of progenitor cells move toward the embryo’s midline, they fuse and form a single structure called the genital tubercle. That’s why — under normal developmental circumstances — we mammals begin with a single embryonic phallus that will become either a penis or clitoris, again, in response to circulating sex steroid hormones.

I know what you’re wondering… Yes, there are rare instances in which the genital buds do not fuse into a single genital tubercle in mammals, including people. This can lead to a variety of rare developmental duplication syndromes including penile duplication, or diphallia. That condition was first described in humans by the 17^th-century Swiss physician Johannes Wecker. In general, these duplication syndromes include a variety of other serious developmental problems because the processes from which they arise are so intricate and intertwined.

So, I’m still not convinced that trying to make a carving knife out of frozen poop is a good use of resources. However, studying reptile naughty bits is. It’s not just that the anatomy is interesting. More importantly — as I’ve alluded to here — we share a deep common ancestry of genital structures, developmental mechanisms, and genetics with other vertebrates, including reptiles. Understanding the anatomy and embryology of our evolutionary relatives helps us understand how we became human.

More importantly, however, a deep understanding of the evolutionary and genetic forces that make us human should prevent us from making foolish mistakes, like thinking that developmental anomalies create new types of human beings, or that we can surgically alter a few external body parts and change a person into something they’re not. Biology is more complicated than that. And, everything is biology, after all.