Early humans had surprising diets 3.5 million years ago

The debate about when our ancestors started eating meat has taken an unexpected turn. While we’ve long associated early human evolution with meat consumption, a recent study reveals that some of our earliest ancestors stuck to a mostly plant-based diet.

The research was led by Dr. Tina Lüdecke from the Max Planck Institute for Chemistry in Germany in collaboration with researchers from South Africa.

The findings challenge our previous assumptions about early hominin diets.

Teeth hold clues of ancient diets

A team of researchers from the Max Planck Institute for Chemistry in Germany and the University of the Witwatersrand (Wits University) in South Africa analyzed nitrogen isotopes in the fossilized tooth enamel of seven Australopithecus individuals.

These fossils were recovered from the Sterkfontein Caves near Johannesburg, a site rich in early hominin remains.

By comparing these isotopic signatures to those of coexisting animals – including herbivores like antelopes and monkeys, as well as carnivores such as hyenas and big cats – the scientists established the positrons of Australopithecus in the prehistoric food web.

The nitrogen isotope ratios in the Australopithecus teeth were consistently low, closely resembling those of plant-eating animals. This strongly suggests that these early human ancestors primarily consumed a plant-based diet and did not regularly eat meat.

While the researchers acknowledge that Australopithecus may have occasionally consumed animal proteins such as eggs or insects, their findings indicate that meat was not a significant part of their diet.

Plant-based vs. meat diets

The key to this discovery lies in the analysis of nitrogen isotopes, which provide reliable indicators of an animal’s diet. When animals digest food, their bodies process nitrogen in a way that leaves distinct chemical traces.

Specifically, the ratio of heavy nitrogen isotopes (15N) to light nitrogen isotopes (14N) increases as one moves up the food chain.

Herbivores, which consume plants, have lower nitrogen isotope ratios, while carnivores have higher ratios because they consume herbivores.

“Tooth enamel is the hardest tissue of the mammalian body and can preserve the isotopic fingerprint of an animal’s diet for millions of years,” noted geochemist Tina Lüdecke.

Nitrogen isotopes reveal ancient diets

By measuring nitrogen isotope ratios in fossilized tooth enamel, scientists can determine whether an organism primarily consumed plants or animals.

While this method has been widely used to study the diets of modern animals and humans, it was previously limited to fossils only tens of thousands of years old due to the degradation of organic material over time.

However, Lüdecke and her team applied a breakthrough technique developed in Alfredo Martínez-García’s laboratory at the Max Planck Institute for Chemistry. This method allowed the researchers to extract nitrogen isotope data from fossilized tooth enamel that is millions of years old.

Evolution of meat in diets

One of the most significant aspects of this study is how it challenges existing theories about the role of meat in human evolution.

Many researchers have theorized that the consumption of animal resources, especially meat, played a crucial role in the development of larger brains and more advanced tool-making abilities.

The protein and fat found in meat have been linked to the evolutionary increase in brain size seen in later hominins. However, direct evidence of when meat became a staple in the human diet has remained elusive.

Australopithecus did not eat meat

The findings from this study suggest that Australopithecus did not regularly hunt or consume large mammals, unlike Neanderthals, who lived millions of years later and actively pursued large game.

This implies that the shift toward a meat-based diet occurred later in human evolution, possibly with the emergence of the genus Homo.

“This method opens up exciting possibilities for understanding human evolution,” said Martínez-García. “It has the potential to answer crucial questions, for example, when did our ancestors begin to incorporate meat in their diet? And was the onset of meat consumption linked to an increase in brain volume?”

Major breakthrough in dietary research

This research represents a major breakthrough in the study of ancient diets. Previous studies relied on indirect evidence, such as tool use and wear patterns on teeth, to infer what early hominins ate.

However, by directly measuring nitrogen isotopes in fossilized tooth enamel, Lüdecke’s team has provided the most concrete evidence yet that Australopithecuswas largely herbivorous.

“This work represents a huge step in extending our ability to better understand diets and trophic levels of all animals back into the scale of millions of years. The research provides clear evidence that its diet did not contain significant amounts of meat,” said Professor Dominic Stratford, director of research at the Sterkfontein Caves.

“We are honored that the pioneering application of this new method was spearheaded at Sterkfontein, a site that continues to make fundamental contributions to science even 89 years after the first hominin fossils were discovered there by Robert Broom.”

Future research directions

Lüdecke’s team now plans to expand their research by analyzing fossilized tooth enamel from other early hominin species across different time periods and geographic regions.

By collecting data from key fossil sites in eastern and southern Africa as well as Southeast Asia, they hope to better understand when and how meat consumption became a regular part of the human diet.

The research could help answer long-standing questions about whether the introduction of meat provided an evolutionary advantage.

Did meat consumption contribute to the development of larger brains? Did it play a role in social structures and hunting behaviors? These are the types of questions that future studies will seek to address.

The study, funded by the Max Planck Society and supported by the German Research Foundation’s Emmy Noether program, marks a major advancement in the field of paleoanthropology.

By applying cutting-edge scientific techniques to ancient fossils, researchers are now able to uncover new details about the dietary habits of our distant ancestors.

Meat and diet of human ancestors

The findings from this study challenge traditional assumptions about early human diets. Rather than being early hunters, Australopithecus appears to have relied primarily on plant-based food.

This research provides a clearer picture of how human nutrition evolved over millions of years and highlights the importance of continued exploration in the field of evolutionary anthropology.

As scientists refine their methods and expand their dataset, we may soon uncover even more details about the dietary habits that shaped the course of human evolution.

One thing is clear – our journey from plant eaters to omnivorous beings was not as straightforward as once thought.

The study is published in the journal Science.

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