Humans were hypercarnivorous ‘apex predators’ for two million years, researchers say

Stone age humans operated as “apex predators”, specialising in hunting large animals for a key period during our evolution spanning around two million years, research by scientists in Israel suggests.

The researchers at Tel Aviv University said they were able to reconstruct the nutrition of stone age humans, and said diets began to substantially change around 85,000 years ago when the extinction of megafauna alongside the decline of other animal food sources led humans to gradually increase the vegetable element in their nutrition.

They said this process continued until homo sapiens had “no choice but to domesticate both plants and animals”, thereby becoming farmers and eventually leading to the flexibilities of the modern human diet.

Dr Miki Ben-Dor of the Jacob M Alkov Department of Archaeology at the university said: “So far, attempts to reconstruct the diet of stone-age humans were mostly based on comparisons to 20th century hunter-gatherer societies. This comparison is futile, however, because two million years ago hunter-gatherer societies could hunt and consume elephants and other large animals, while today’s hunter gatherers do not have access to such bounty.

“The entire ecosystem has changed, and conditions cannot be compared. 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.”

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He added: “Human behaviour changes rapidly, but evolution is slow. The body remembers.”

The researchers said evidence of genetic changes and the appearance of unique stone tools for processing plants led them to conclude that starting about 85,000 years ago in Africa, and about 40,000 years ago in Europe and Asia, a gradual rise occurred in the consumption of plant foods as well as dietary diversity - in accordance with varying ecological conditions.

This rise was accompanied by an increase in the local uniqueness of the stone tool culture, which they said could be compared to the diversity of material cultures in 20th-century hunter-gatherer societies.

In contrast, during the two million years when, according to the researchers, humans were apex predators, long periods of similarity and continuity were observed in stone tools, regardless of local ecological conditions.

Dr Ben-Dor and his colleagues said they examined around 400 scientific papers from different disciplines dealing with the focal question: Were stone-age humans specialised carnivores or were they generalist omnivores?

They said most of the evidence they collated was found in research papers on current biology, particularly in the fields of genetics, metabolism, physiology and morphology.

“One prominent example is the acidity of the human stomach,” said Dr Ben-Dor.

“The acidity in our stomach is high when compared to omnivores and even to other predators. Producing and maintaining strong acidity require large amounts of energy, and its existence is evidence for consuming animal products. Strong acidity provides protection from harmful bacteria found in meat, and prehistoric humans, hunting large animals whose meat sufficed for days or even weeks, often consumed old meat containing large quantities of bacteria, and thus needed to maintain a high level of acidity.

“Another indication of being predators is the structure of the fat cells in our bodies. In the bodies of omnivores, fat is stored in a relatively small number of large fat cells, while in predators, including humans, it’s the other way around - we have a much larger number of smaller fat cells.”

The researchers said their theory was supported by additional archaeological evidence. They cited research that revealed that stable isotopes in the bones of prehistoric humans, as well as hunting practices unique to humans, together suggest that humans specialised in hunting large and medium-sized animals with high-fat content.

“Hunting large animals is not an afternoon hobby,” said Dr Ben-Dor. “It requires a great deal of knowledge, and lions and hyenas attain these abilities after long years of learning. Clearly, the remains of large animals found in countless archaeological sites are the result of humans’ high expertise as hunters of large animals.”

He also suggested human hunting was likely the cause of the demise of many extinct species.

“Many researchers who study the extinction of the large animals agree that hunting by humans played a major role in this extinction - and there is no better proof of humans’ specialisation in hunting large animals. Most probably, like in current-day predators, hunting itself was a focal human activity throughout most of human evolution.”

He added: “Other archaeological evidence - like the fact that specialised tools for obtaining and processing vegetable foods only appeared in the later stages of human evolution - also supports the centrality of large animals in the human diet, throughout most of human history.”

The team said their multidisciplinary reconstruction conducted over almost a decade proposes a “complete change of paradigm in the understanding of human evolution”.

“Contrary to the widespread hypothesis that humans owe their evolution and survival to their dietary flexibility, which allowed them to combine the hunting of animals with vegetable foods, the picture emerging here is of humans evolving mostly as predators of large animals,” the researchers said.

“Archaeological evidence does not overlook the fact that stone-age humans also consumed plants," Dr Ben-Dor said, “but according to the findings of this study plants only became a major component of the human diet toward the end of the era.”

Professor Ran Barkai, also of the Department of Archaeology at Tel Aviv University, and a co-author of the research, said: “Our study addresses a very great current controversy - both scientific and non-scientific.

“For many people today, the Paleolithic diet is a critical issue, not only with regard to the past, but also concerning the present and future. It is hard to convince a devout vegetarian that his/her ancestors were not vegetarians, and people tend to confuse personal beliefs with scientific reality. Our study is both multidisciplinary and interdisciplinary. We propose a picture that is unprecedented in its inclusiveness and breadth, which clearly shows that humans were initially apex predators, who specialised in hunting large animals.”

He added: “As Darwin discovered, the adaptation of species to obtaining and digesting their food is the main source of evolutionary changes, and thus the claim that humans were apex predators throughout most of their development may provide a broad basis for fundamental insights on the biological and cultural evolution of humans.”

The research is published in the American Journal of Physical Anthropology.