Previous research suggests that our ancient human ancestors were hunter-gatherers who relied heavily on eating animals. These assumptions have been replicated in popular “fad” diets such as Paleo and Carnivore, which emphasize humans’ ancestral diets and encourage heavy meat consumption. However, the science on prehistoric diets remains unclear. Did ancient humans truly prioritize hunting animals and only forage for plants when necessary?

According to the authors of this study, research on this topic typically relies on indirect evidence. Previous scholars excavated objects like spears and arrowheads, stone tools, and large animal bone fragments and made the assumption that large mammal hunting was the norm. However, other excavations suggest that plant-based foods were also part of early human diets, including studies of human dental remains. The authors wonder whether the overrepresentation of hunting-related artifacts in excavations, along with gender biases, have inflated the importance of hunting.   

In this study, researchers tested the hypothesis that human hunter-gatherers in the Andes highlands in South America relied mostly on large mammal hunting. They used a more direct research method called stable isotope analysis — this involves studying certain elements in human bone remains to reveal what types of food ancient humans ate. They also compared this information to plant and animal remains found at the excavation site. They sampled bones from 24 humans who lived in what is now Peru during the Archaic Period (9,000-6,500 years before present).

Researchers assumed their results would show a diverse diet with an emphasis on large animal consumption. However, contrary to previous research, the bone analysis suggested that plants dominated ancient diets in the Andes region, making up between 70-95% of dietary consumption. Wild tuber plants (like potatoes) were the main plant source, while large mammals played a secondary role. Meanwhile, meat from small mammals, birds, and fishes, as well as other plant types, played a much smaller dietary role. 

The authors give several reasons why meat from large mammals may not have been a primary source of food for their subjects. It’s possible that ancient humans hunted these animals for thousands of years, ran out of animal resources, and adjusted their diets accordingly. However, it’s also possible that large mammals didn’t arrive in the region until later, or that humans simply didn’t hunt as much as researchers previously assumed. 

A final explanation is that early Andean populations did heavily hunt large mammals, but also incorporated the plant-based contents of those animals’ stomachs (called “digesta”) into their own diets. More research is required to determine which, if any, of these explanations is the most likely.

Overall, this research suggests that Andean societies from the Archaic period may have relied more on plants than previous researchers assumed. Animal advocates can use these findings to challenge popular narratives that our human ancestors always relied on hunting and consuming animals. Although human diets likely differ depending on the region and time period being studied, it’s important not to make blanket assumptions that all hunter-gatherers, from all prehistoric time periods, followed a single (meat-heavy) diet.