Neanderthals ate a diet consisting of 80 percent red meat and 20 percent plant-based food, according to two new associated studies that analyzed skeletons of early humans from Europe and Asia.

The findings support earlier research that at least some paleo diets relied heavily on red meats; included some fruits, vegetables and other plant materials; and were mostly, if not completely, devoid of seafood. The latest studies are published in the Journal of Human Evolution and the journal Quaternary International.

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"We have taken a detailed look at the Neanderthals' diet," co-author Hervé Bocherens of the Senckenberg Center for Human Evolution and Palaeoenvironment at the University of Tübingen said in a press release. He added that he and his team also looked at the diet of Stone Age Homo sapiens.

"In the process," he said, "we were able to determine that the extinct relatives of today's humans primarily fed on large herbivorous mammals, such as mammoths and woolly rhinoceroses."

Bocherens and his colleagues analyzed Neanderthal and animal remains from two excavation sites in Belgium. They also looked at the diet of modern humans from the same time period, 45,000–40,000 years ago. The animals included mammoths, woolly rhinoceroses, wild horses, reindeer, European bison, cave hyenas, bears, lions and wolves.

Isotope analysis of the collagen (component of connective tissue) in the various bones demonstrated that the Neanderthals' diet differed markedly from that of other predatory animals living at the same time.

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"Previously, it was assumed that the Neanderthals utilized the same food sources as their animal neighbors," Bocherens said. "However, our results show that all predators occupy a very specific niche, preferring smaller prey as a rule, such as reindeer, wild horses or steppe bison, while the Neanderthals primarily specialized on the large plant-eaters such as mammoths and woolly rhinoceroses."

Anthropologists have found weapons, like spears, associated with Neanderthals, who must have had a very organized, group approach to hunt such large prey.

While they clearly loved their meat, Neanderthals were also eating fruits, vegetables and other plants, too.

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"In this study, we were able for the first time to quantitatively determine the proportion of vegetarian food in the diet of the late Neanderthals," Bocherens said. "Similar results were found for more recent Stone Age humans."

The scientists hope that this and future studies continue to shed light on what might have led to the disappearance of Neanderthals and their culture around 40,000 years ago. Neanderthals did not seem to be starving to death, so the researchers are ruling out that diet was a decisive factor.

It could just be, as many other studies suggest, that Neanderthals and their ways were absorbed into the modern human population due to interbreeding. It is now known that people of European and Asian descent are part Neanderthal.

Video: Did We Eat All the Neanderthals?

Regarding seafood, it should be noted that while this and other studies are putting a lot of emphasis on red meat's importance in early paleo diets, later populations of Europeans and Asians relied heavily on fish and other seafood, with many living to ripe old ages. Humans today, of course, can become vegetarians, with other studies concluding that plant-based diets may increase lifespan.

Time will tell if certain cultures, or perhaps even individuals, are better evolved for any particular diet.