Proponents of the Paleo philosophy, a popular diet based on foods believed to have been eaten by cavemen, are overlooking a gruesome staple of their meals: other people.

Researchers at the University of Tübingen in Germany found that Neanderthals had a taste for human bones and meat. The study published in the journal Scientific Reports on Wednesday found that cannibalism dates back as far as 45,000 years ago. Neanderthal remains discovered in France and the Iberian Peninsula bear cut marks, as well as percussion indentations that show bones were purposefully crushed to extract the marrow.

“These indications allow us to assume that the Neanderthals practiced cannibalism. The many remains of horses and reindeer found in Goyet were processed the same way,” Hervé Bocherens, a University of Tübingen professor and lead researcher, told the Guardian.

Not much information is known about Neanderthals who existed between 40,000 and 45,000 years ago, since most research looks at those who lived close to when the human subspecies died out around 30,000 years ago. Some theories suggest that lack of resources contributed to their extinction, while other studies bolster the theory that Neanderthals were an appetizing dinner: A study published in 2009 suggested that humans ate the species to extinction.

“Neanderthals met a violent end at our hands, and in some cases we ate them,” Fernando Rozzi, an anthropologist at the National Center of Scientific Research in Paris, told Time.

No Paleo diet guides were immediately amended to reflect the latest findings.