El Salt site during excavation (courtesy of PLOS-ONE)

Scientists have really stepped in it this time. A 50,000-year-old pile of poop found at a Neanderthal campsite in Spain suggests Neanderthals might not have been the meatheads we think they are.

Until this discovery, we only had indirect evidence of what our ancient human cousins ate. Studies of their teeth and the plants and animals that existed alongside them suggested Neanderthals ate only meat.

But chemical analysis of poop samples discovered at an archaeological site in Alicante, Spain, suggests Neanderthals may have enjoyed significant servings of plants too.

USA Today summed up the findings:

Three of the five Neanderthal samples contained high levels of compounds created by the breakdown of cholesterol, which is found in animal foods. But two additional samples contained those same compounds as well as those produced by the breakdown of molecules found in plant-based foods. The ratio of the different compounds points to a human origin, the researchers say.

Analysis of the poop also turned up evidence of parasites such as hookworms and pinworms in numbers that would have made modern humans very, very sick, one of the researchers told National Geographic.

The findings were reported Wednesday in the journal PLOS ONE by a group of Massachusetts Institute of Technology researchers led by Ainara Sistiaga.

Oddly enough, the feces was found atop an ancient campfire where researchers were looking for clues as to how our ancestors prepared food.

“I thought they were cooking in there, so I was looking for lipids from cooking,” Sistiaga told USA Today. “Instead, analysis revealed traces of an activity that doesn’t usually take place atop a blazing fire, but I don’t think they were using [the site as a toilet] when the fire was active.”

Preserved dung – a fancy phrase for old poop – has been found at other sites, including a roughly 6,000-year-old sample from a large Neolithic village in Turkey, and what could be a 14,000-year-old sample from a cave in Oregon, USA Today said. But the five samples from Spain are the oldest examples of human excrement ever found, dating back 50,000 years.

What we still don’t know is whether vegetables were a staple of the Neanderthal diet or an occasional side dish – it’s hard to tell from just five samples found at one site. Nor have researchers calculated the meat-to-veggie ratio of the samples they found.

Paleontologist Erik Trinkaus of Washington University in St. Louis told National Geographic it’s the first study to provide direct chemical proof that Neanderthals ate vegetables. Other recent discoveries offered only indirect evidence — such as plant remains found on teeth — that Neanderthals weren’t strict carnivores.

Several researchers interviewed by USA Today express reservations about the findings.

The compounds measured by Sistiaga and her colleagues have probably degraded over time, making them unreliable as indicators of human feces, says Michael Richards of the University of British Columbia. The study does not rule out bears, which are also omnivorous, as the source of the coprolites, says Hervé Bocherens of the University of Tübingen in Germany.

However, Sistiaga told National Geographic that the compounds she tested for are “very stable” and are present in ratios found only in humans.

If Neanderthals are proven omnivorous, it would undermine the suggestion of some researchers that their meat-centered diet ultimately led to their extinction when they had to compete for resources with other omnivorous early humans.