Scientists have discovered the oldest known human poop, which is already providing valuable insight into the life of Neanderthals who lived in Spain approximately 50,000 years ago.

Researchers confirmed on June 25 that they found five samples of human fecal matter at an archeological site called El Salt, in the floor of a rock shelter where Neanderthals once lived.

"So far, it is the only fossil evidence that gives us information of the ingestion and the regular meals of our ancestors," said Ainara Sistiaga, a geoarchaeologist at the Massachusetts Institute of Technology and University of La Laguna who was one of the researchers, according to Reuters.

The researchers examined the fossils to try figuring out the types of food the Neanderthals ate.

Analysis of the samples provided a better understanding of the diet of this extinct human species, and offered the first evidence that Neanderthals were omnivores, meaning they also ate vegetables with their meat, according to Reuters.

"Understanding the diet of past human species closely related to our own will help us gain perspective on our evolutionary constraints and adaptability," Sistiaga said.

Their findings did prove that Neanderthals mainly consumed meat, as suggested by the large amounts of one such "biomarker" called coprostanol, which forms by the bacterial reduction of cholesterol in the gut. They also found solid evidence for significant plant intake as well, thanks to the presence of a compound called 5 beta-stigmastanol, which is found in plants.

"It's like any other fossil," said Massachusetts Institute of Technology geobiology professor Roger Summons, another of the researchers, according to Reuters. "Fossils provide our most direct link with organisms from the past."

Neanderthals are the closest extinct relative to homo sapiens, our species, and disappeared after early modern humans first entered Europe from Africa.

It is believed that Neanderthals prospered across Europe and Asia from around 250,000 to 40,000 years ago and interbred with Homo sapiens before disappearing for good.

Before finding the fecal matter, scientists believed Neanderthals mainly ate meat, with a small chance that they ate some veggies as well. They've never had direct evidence like these fossils provided however, according to Reuters.

"Sometimes in prehistoric societies, individuals used their teeth as tools, biting plants among other things. We can't assume they were actually eating plants based on finding microfossils in teeth," Sistiaga said.

The specific foods consumed were not identified by the researchers, but they did note that animal remains suggested they hunted deer and horses.

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