Remember that history professor that would berate you for drawing penises in your notebook during class? Well you may have been on to something.

There have been numerous theories throughout history surrounding Stonehenge. Some believe it was a burial place, while others are convinced it was built by aliens. But our money is on this latest theory.

Professor Terence Meaden, an archaeologist with University of Oxford, claims that the stone structure is a 6,000-year-old monument to penises. After studying Stonehenge and 20 other Neolithic stone circles in the UK, Meaden concluded that it was built for fertility rituals of ancient societies. They’re designed to create giant shadows shaped as penises, which “penetrate” the inner circle as the sun rises, hitting the central “female” stone. He spent 120 days over five years photographing the structures at sunrise, finding that the “moving fertility play” happens eight times a year, starting with the winter solstice.

“My basic discovery is that many stone circles were built at a time of a fertility religion,” Meaden said in his study, which was published in theJournal of Lithic Studies. “And that stones were positioned such that at sunrise on auspicious dates of the year, phallic shadows would be cast from a male-symbolic stone to a waiting female-symbolic stone.”

Other experts have been quick to try and debunk Meaden’s theory. Because the idea that aliens left it that way is so much more logical.

“Devised in the late Neolithic, this could be a dramatic visual representation of the cosmic consummation of the gods between a sky father and the earth mother goddess,” Meaden further states.

So, keep that in mind the next time you strike a cute pose under one of these stone arches for your Insta story. Someone was probably having sex on that very spot, 6,000 years ago.