A New Discovery About Ancient Human Societies Upends What We Thought, Scientist Says

If you try to picture a paleo diet, scenes of a caveperson tearing hunks of animal flesh off a bone probably come to mind. But new analysis of remains from an ancient Andean culture has revealed that these hunter-gatherers mostly survived off plants, not meat—a blow for die-hard paleo-gym-bros everywhere.

In a study published on Wednesday in PLoS ONE, researchers analyzed the chemical composition of 9,000- to 6,500-year old human bones from the Wilamaya Patjxa and Soro Mik’aya Patjxa sites in Peru and concluded that close to 80 percent of these early humans’ diets were plant-based. 

The findings fly in the face of conventional wisdom—and even previous scientific evidence— that says early Andeans preferred eating llama-like animals and deer. Even recent excavations of the sites have found arrowheads, flakes left behind from making stone tools, and animal bones—all suggesting a meat-heavy diet.

“If you had talked to me before this study and asked me what I thought early human diets were in the Andes mountains I would have told you very confidently that it’s on the order of 80 percent meat-based and 20 percent plant-based. In fact we had it completely reversed,” study co-author, archeologist Randy Haas told Motherboard. 

Hard materials like bone or stone are preserved better than plants, and simply finding these materials at a site doesn’t tell researchers anything about how much meat people actually ate. It’s likely that the evidence for hunting has been “overinflated,” according to Haas, leaving a lot of room for interpretation and misconception. 

In the latest study, he and his team both sieved through material found in burn and storage pits at the Peruvian sites and conducted stable isotope analysis of human remains found there. Isotopes of carbon and nitrogen change their signature and ratio as they move through ecosystems; from the air, to plants, to animals, to other animals. By analyzing the type and relative amounts of those isotopes, scientists can figure out how much plant or animal matter ancient people ate.

Their analysis revealed that somewhere between 75 to 95 percent of the Andeans’ diets were made up of plants, and the rest land animals. Based on a closer look at the fragments of plants left behind at the sites and patterns of tooth wear, researchers think that most of the plants the Andeans ate were probably root tubers like potatoes.

Haas has several theories about why these ancient peoples might have been more plant-based. One is that they hunted local animals to near-extinction by 9,000 years ago. Another is that early humans just didn’t hunt as much as we previously thought. Other studies have suggested that hunter-gatherer diet preferences can be dictated not just by food availability, but also culture.

Archeologists’ overall understanding of early human diets is based on a principle called optimal foraging—basically, people want to maximize the amount of calories they get for the effort they put into getting it. Under that assumption, eating meat makes sense if there are plenty of animals around. Once animal numbers start to dwindle, people will slowly incorporate more plants. “That’s still a reasonable way to think about it,” says Haas, but he and other scholars thought that this transition from more-meat to more-plants happened over thousands of years. “These findings suggest to me that if this transition happened, then it happened very quickly.” 

He goes further to say that the study makes them question their fundamental understanding of how these agrarian cultures evolved. “These humble foragers, beginning 9,000 years ago, started the process of domesticating a few resources that would eventually become the foundation for state economies, and eventually they would become food products that are some of the most important food products in the global economy today.”

Haas says that while it’s not possible to generalize this particular finding to all early human populations around the world, “it allows us to reject any sense that early human diets were categorically and broadly meat-based everywhere around the world.”

It’s true that researchers generally agree there’s no ‘one paleo-diet fits all’ but Haas believes the overall pervasiveness of the idea that paleo diets are predominantly meat-based may have more to do with popular culture than actual science. He hopes this study may make a dent in that narrative too. “I do this work because I think it can inform or have some implications for understanding humanity today.”

Haas predicts that future researchers may turn up similar, plant-focused findings. “Because those other archeologists in other parts of the world are working with the same kinds of biases that I’m working with, they will find that plants played a more prominent role in early human diets.”