• For some prehistoric humans in the Andes, the Paleo diet meant eating lots of plants
• The diet of was likely made up of 80% plants, a study found. 
• There were as many types of Paleo diets as there were human populations back then, an expert said.

The popular Paleo diet is based on the belief that we are better off eating like our ancestors by sticking to a largely meat-heavy diet.

But a new study suggests that some of our ancestors didn’t gorge on meat at all, but preferred a diet that was largely made up of plants.

“Conventional wisdom holds that early human economies focused on hunting — an idea that has led to a number of high-protein dietary fads such as the paleo diet,” Randy Haas, Assistant Professor of Anthropology at the University of Wyoming who led the study, said in a press release.

“Our analysis shows that the diets were composed of 80 percent plant matter and 20 percent meat,” he said.

The research, published Wednesday, studied the remains of ancient people buried in the Andean Altiplano of Peru about 9,000 years ago.

It adds to a body of evidence that suggests prehistoric diets were already incredibly varied, ranging from meat-heavy to meat-poor, said Herman Pontzer, a professor of evolutionary anthropology at Duke University told Business Insider.

“One way to think about it is as soon as anybody tells you that the Paleo diet was one thing, you can stop listening,” said Pontzer, who wasn’t involved in the study.

You are what you eat

When you look at an anthropological site, it is easy to think that humans always loved a good barbecue.

“Animal bone is often better preserved, more abundant, and easier to recover from archaeological sites,” Ceren Kabukcu, an archaeobotanist who studies ancient diets from the University of Liverpool, told BI.

The same goes for the sharp rock and bone tools used for hunting.

This so-called preservation bias has led some prominent researchers to think Palaeolithic humans must have prioritized hunting over gathering.

But the advent of more modern analytical techniques, including mass spectrometry, has changed the story. For instance, scientists can now read what people were eating at the time from the type of atoms, or isotopes, preserved inside human bones, such as nitrogen.

“When you eat proteins, you’re eating nitrogen and all nitrogen in the world comes in different flavors,” said Pontzer.

If you eat something higher up the food chain, “you keep on adding this sort of special form of nitrogen,” he said. This isotope binds to the bones as they grow, and scientists can read them thousands of years later.

Haas and his collaborators carried out these kinds of analyses on the bones of 24 people of Wilamaya Patjxa and Soro Mik’aya Patjxa in Peru.

This was a group of mobile foragers that lived between 9,000 and 6,500 years ago about 2.3 miles above sea level. At that time agricultural and pastoral economies did not yet exist, “at least not to the extent that we know them today,” Haas told BI in an email.

The group has long been thought to be mostly meat eaters. But Haas and colleagues’ investigation, published in the peer-reviewed journal PLoS ONE on Wednesday, found they ate between 70-95% of plant matter in their diet.

Tubers — cousins of the modern-day potato — likely made up the bulk of their meals.

“I was shocked by the result—ca. 80% plant-based diet among early Andean foragers,” said Haas.

“It was clear at that point that I had the story all wrong, and there was a good explanation for why that was so (preservation bias),” he said.

There is no one Paleo diet

This isn’t the only research that disproves the model often held up by proponents of the modern-day definition of the Paleo diet.

Paleo-diet traditionalists uphold the definition popularised by sports physiologist Loren Cordain in the early 2000s. He called on people to eat a meat-heavy, carb-poor diets to emulate their ancestors.

Since then, people have come up with variations of this idea, like the pegan diet — a mix of the paleo and vegan diet.

These diets might work for you as an individual, but as far as the anthropological evidence goes, they don’t stack up, Pontzer said.

“Where it starts to get strange is when we start to engage in the storytelling about the past to prop up a particular extreme view of what we’re supposed to eat,” he said.

What’s clear is that a meat-heavy diet isn’t reflective of what people ate thousands of years ago.

Instead, prehistoric populations went for whatever was available around them, almost always relying on a healthy mix of hunting and gathering.

“Gathering is dependable. You always come home with something,” said Pontzen.

Some populations, like the Arctic people, may have mostly relied on big game for their food, said Pontzer, who also wrote “Burn,” a book that touches on the topic.

But others, like the early Australian and South American populations, seem to have eaten mostly plants. Many others were somewhere in between.

Early humans or close ancestors didn’t necessarily shun starchy foods, Pontzer said. One study, for instance, found on Neanderthals ate plenty of starchy carbohydrates.

These diets changed with the seasons or as resources ran out.

And as investigation techniques get more sophisticated, we may learn even more about our ancestors’s meals by revisiting the evidence, said Haas.

“Humans, as far as we’ve ever been able to tell, have eaten a really diverse diet and can do well on all kinds of diets,” said Pontzer,

“Keep your diet that works. But I do wish that we would have less of this kind of revisionist history to support our choices of diet because there’s really little evidence of that,” said Pontzer.