Anything but lean and green: Early humans were apex meat-eaters, study finds

A recent study published in the American Journal of Physical Anthropology suggests that for 2 million years, Homo sapiens and their ancestors primarily fed on meat, positioning themselves at the top of the food chain. The research team included anthropologists from Tel Aviv University in Israel and the University of Minho in Portugal.

Reconstructing the diets of hominids who lived as far back as 2.5 million years ago has been challenging because plant remains do not preserve as easily as animal bones, teeth, and shells. Anthropologists have traditionally relied on modern-day ethnography to determine what early humans gathered, based on the assumption that little has changed. However, Miki Ben-Dor, a researcher at Tel Aviv University, and his colleagues argue that this assumption is a significant mistake.

"Human behavior changes rapidly, but evolution is slow. The body remembers," Ben-Dor stated, according to Science Alert. He and his team decided to use other methods to reconstruct the diet of Stone Age humans: to examine the memory preserved in our own bodies, our metabolism, genetics, and physical build. Ben-Dor explained, "For example, geneticists have concluded that areas of the human genome were closed off to enable a fat-rich diet, while in chimpanzees, areas of the genome were opened to enable a sugar-rich diet."

By analyzing evidence present in our bodies—such as metabolism, genetics, and physical structure—the researchers found that humans have higher fat reserves and can rapidly turn fats into ketones when needed. Unlike other omnivores, human fat cells are small and numerous, similar to those of a predator. Our digestive systems resemble those of higher carnivores, and humans have unusually strong stomach acid, which helps break down proteins and kill harmful bacteria. Compared with other primates, humans need more energy per unit of body mass, especially for the energy-hungry brain. Human social structures, such as raising children, limit the time available for food gathering.

The study also analyzed evidence on tool use, signs of trace elements, nitrogen isotopes in Paleolithic remains, and dental wear to confirm that Homo sapiens and their cousins were predominantly carnivorous until the Upper Paleolithic, about 11,700 years ago. During this time, Homo sapiens used their ingenuity and endurance to hunt large animals. Large beasts like mammoths, mastodons, and giant sloths roamed the landscape in far greater numbers than today.

With so much water locked up as ice, ecosystems around the world were vastly different from today. During the last great ice age, most of what is now Europe and North America was regularly buried under thick glaciers, and the environment was very different from today, with large mammals dominating the landscape. The frequency with which Homo sapiens preyed on these herbivores has been difficult to determine. Chemical analysis of bones and tooth enamel has found localized examples of diets heavy in plant material, but extrapolating this to humanity as a whole is not straightforward.

According to Ben-Dor and his colleagues, modern hunter-gatherers have given us a distorted idea of what our ancestors ate. They argue that ecosystems and environmental conditions have radically changed over the millennia, making it misleading to base conclusions on modern observations. "We decided to use other methods to reconstruct the diet of Stone Age humans: to examine the memory preserved in our own bodies, our metabolism, genetics, and physical build," Ben-Dor said.

After the Upper Paleolithic, studies on modern hunter-gatherer communities become more relevant as a decline in large animal populations and cultural fragmentation led to increased plant consumption. The Neolithic revolution of farming and agriculture was a result of these changes. Despite the fact that our evolutionary past does not necessarily have to guide our current food choices, understanding the role we occupied in the food chain has a significant impact on our health, physiology, and our impact on the environment in past eras.

This article was written in collaboration with generative AI company Alchemiq