When did humans’ ancestors start to eat meat regularly? Premium

Scientists have been learning more about the diets of early hominins, particularly their reliance on plants.

For decades, scientists have been learning more about the diets of early hominins, particularly their reliance on plants. Yet we still don’t know when these ancestors of humans started eating meat.

This is a frustrating gap in our understanding of human evolution. We think regular meat consumption was one of the main drivers of brain growth and evolution in hominins, because animal products are calorie-dense and easier to digest than unprocessed plant foods. They also contain all the essential amino acids and are rich in biologically important nutrients, minerals and vitamins.

What we do know is that by the time our genus, Homo, emerged over two million years ago, hominins were regularly eating meat. This is clear from their increased reliance at this point on stone tools to butcher and process meat products. We’ve also found fossil bones with cut marks that indicate butchering.

But that doesn’t explain when and where regular meat eating started and which species of our ancestors made that crucial shift.

Now, thanks to fossilised tooth enamel, we’re a step closer to an answer. In a study with several other co-authors, we measured nitrogen isotopes in the enamel from fossilised teeth belonging to the hominin genus Australopithecus, discovered in South Africa’s Sterkfontein Caves. This is one of the oldest known human ancestor species.

Atoms of the same element can have different versions, called isotopes, which have the same number of protons but different numbers of neutrons. This makes them slightly heavier or lighter but chemically similar. For example, nitrogen has two stable isotopes: nitrogen-14 (¹⁴N) and nitrogen-15 (¹⁵N). These occur naturally, but their ratio varies in nature. In food webs, nitrogen isotopes become enriched as you move up the chain, meaning predators have higher ¹⁴N/¹⁵N ratios than herbivores.

Identifying these isotopes is a way to reconstruct ancient diets and ecosystems, helping scientists understand how past environments shaped the survival of species – including early humans.