There is amazing variation in penises throughout the animal kingdom. Some phalluses have multiple heads (spiny anteaters), others are shaped like a corkscrew (lake ducks), and others are several times the length of the creature’s entire body (barnacles). By contrast, the mammalian "fleshy inflatable cylinder” we’re all used to seems pretty boring, right? As it turns out, however, the anatomy of the human penis is actually quite fascinating.

In this TED video, comparative biologist Diane Kelly shares what she has gleaned from years of penile research. As you’ll see, it turns out that something as seemingly simple and straightforward as the mechanics of an erection is really quite complex. After watching this video, I think you’ll agree with Kelly that anatomy is far from being a “dead” science and there’s still a lot we have to learn about our own bodies.