Scientists have long debated how humans evolved larger brains and whether eating meat played a key role. A new study suggests our early ancestors may not have relied on meat as much as previously believed. Instead, evidence from ancient teeth points to a diet dominated by plants.
Researchers examined fossil teeth from Australopithecus species found in the Sterkfontein Caves of South Africa. These remains date back around 3.5 million years. To investigate diet, scientists measured nitrogen isotopes preserved in the enamel.
Nitrogen-14 and nitrogen-15 occur naturally in food but in different amounts depending on whether the source is plant or animal. Predators tend to accumulate more nitrogen-15 than herbivores. By comparing the isotope ratios, researchers could estimate how much meat early hominins consumed.
Mostly plant-based diet
The results showed that Australopithecus had nitrogen levels similar to herbivores, suggesting a diet largely based on plants. While occasional meat consumption cannot be ruled out, regular meat-eating appears unlikely at this stage in human evolution.
Earlier research had linked meat consumption with the rise of larger brains, citing evidence of stone tools and animal bones with cut marks dating back about 2.9 million years in Kenya. By around 2 million years ago, regular butchering and meat-eating became more common among human ancestors.
Rethinking evolution and brain growth
The findings challenge long-held assumptions that meat was essential to brain development in early hominins. Neanderthals, who lived much later around 250,000 years ago, were heavily reliant on meat. But Australopithecus and other early ancestors may have thrived on a diet that was mostly plant-based.
Researchers caution that more studies are needed before rewriting human evolution textbooks. Still, the evidence from fossil teeth suggests diet may have been more flexible and varied than once thought.
A new perspective
This study opens up new questions about the role of food in human evolution. If meat was not the primary driver of brain growth in early hominins, other factors such as cooking, social behavior, and environmental adaptation may have played bigger roles.
