“Apparently no organs evolve faster and into more variable shapes than those involved in procreation.”

Throughout the animal kingdom, genitals are very complex—way more complex than they are in humans. Take the male argonaut octopus, for example, which has a detachable penis that can swim on its own. Or consider female kangaroos, which have three vaginas and two uteruses each. On the surface, these genitals might seem way more complicated than they actually need to be for reproductive purposes. So why is that?

As you’ll learn in the absolutely fascinating TED-Ed video below, it’s because animal genitals actually evolved to serve multiple purposes. Their penises and vaginas aren’t just vessels for depositing and receiving sperm; rather, the males of many animal species also use their penises to enact various courtship behaviors, while the females use their genitals to manage and control which males get to deposit sperm and, ultimately, which sperm gets to fertilize their eggs.

Watch the full video to learn more about why genitals are the organs that evolve the fastest in the animal kingdom.