If you want to see sex stuff as part of your job, go into archeology. The ancient world is littered with images of a phallus, a Venus figurine worthy of Hugh Hefner, and even a vulva painting.

Still, most prehistoric erotic art is abstract, disembodied. It doesn’t explicitly depict sex-crazed ancients screwing their brains out for fun and fertility.

But one little-known, mysterious archaeological site does. The Kangjiashimenji Petroglyphs are bas-relief carvings in a massive red-basalt outcropping in the remote Xinjiang region of northwest China. The artwork includes the earliest—and some of the most graphic—depictions of copulation in the world.

Petroglyphs in Hutubei, Xinjiang province, China. Courtesy of Jeannine Davis-Kimball, Credit and link: Slate

The World’s Oldest Pornography by Mary Mycio, Slate