The First Buttholes Might Have Been for Sperm Instead of Poop

Forget everything you thought you knew about your butthole.

It turns out, at least according to a currently unpublished and un-peer-reviewed study, anuses, from which you dispel poop, might have originally been used to dispel sperm. That means that our anuses might have begun their evolutionary journeys as a male sex organ.

Researchers from the University of Bergen in Norway dug into the genetics of xenacoelomorphs, which are a group of tiny creatures without assholes that are distant cousins of flatworms. These critters have a simplified digestive system, essentially a dead-end gut that doubles as a mouth-waste-exit hybrid.

What would eventually evolve into an anus in more complex animals was originally a reproductive hole. There was no dedicated waste evacuation tube. The sperm just got a free pass through the same tube that poop would travel through.

The First Buttholes Might Have Released Sperm Instead of Poo

While xenacoelomorphs use their mouths for everything, from eating to poop, males also have a separate hole for sperm—a “gonadopore,” to be specific. The same genetic tools that were used to create an anus in other animals are what these little guys employ to form their gonadopores.

“Once a hole is there, you can use it for other things,” zoologist Andres Hejnol said while speaking to New Scientist. Hell yeah, brother. A hole is a hole. If an organism has a hole, its body will use it for whatever it needs to. It’s a bit like a cloaca, a multipurpose cavity that is kind of an all-in-one tool that can do a little bit of everything.

Cloacas are commonly found in a wide variety of animals, like reptiles, birds, amphibians, and even some mammals like the platypus. Cloacas are used to expel waste but also double as a reproductive organ. The (again) unpublished and un-peer-reviewed paper suggests that the split between the digestive and reproductive systems happened much later in evolutionary history, long after our ancestors branched off from xenacoelomorphs.

So, yeah. There is a chance that your asshole was once your sperm hole. Do with that information what you will.