New research published in Science journal suggests that early human ancestors, such as Australopithecus, which inhabited southern Africa about 3.5 million years ago, primarily followed a plant-based diet, consuming very little or no meat. This conclusion stems from an analysis of nitrogen isotopes found in the fossilized tooth enamel of seven Australopithecus specimens. The findings show that these early hominins mostly relied on plants, with limited evidence of animal consumption.
The inclusion of animal products, particularly meat, in the diet of early humans has been a critical aspect of understanding our evolution. Meat consumption has been linked to the development of larger brain sizes and tool-making abilities. However, concrete evidence of when and how meat became a part of human ancestors’ diets has been hard to pinpoint. A team of researchers from Germany’s Max Planck Institute for Chemistry and South Africa’s University of the Witwatersrand (Wits University) have now provided new insights, indicating that Australopithecus, which lived in southern Africa between 3.7 and 3.3 million years ago, predominantly ate plants.
The research team studied stable isotope data from the tooth enamel of Australopithecus found in the Sterkfontein cave near Johannesburg, an area rich in early hominin fossils. They compared the isotope ratios from these hominins to those of contemporary animals, including monkeys, antelopes, and carnivores like hyenas, jackals, and large cats.
Tooth Enamel Preserves Dietary Signatures
“Tooth enamel, being the hardest tissue in the body, can preserve a detailed isotopic record of an animal’s diet for millions of years,” explains Tina Lüdecke, the lead researcher of the study. Lüdecke, who leads the “Emmy-Noether Junior Research Group for Hominin Meat Consumption” at the Max Planck Institute for Chemistry in Mainz, Germany, is also an Honorary Research Fellow at the University of the Witwatersrand’s Evolutionary Studies Institute. She regularly travels to Africa to analyze fossilized teeth as part of her research. Wits University manages the Sterkfontein Caves, where these fossils were discovered.
When animals digest food, the biochemical processes favor the “light” nitrogen isotope (14N). As a result, the breakdown products in their bodies contain a higher proportion of this lighter isotope. This leads to an increase in the “heavy” nitrogen isotope (15N) in the excretions like urine, feces, and sweat. Herbivores have a higher nitrogen isotope ratio than the plants they consume, while carnivores have a higher ratio than their prey. By analyzing the 15N to 14N ratio, researchers can determine the trophic level of an organism in the food chain.
Stable nitrogen isotope ratios have long been used to study the diets of living animals and humans through hair, bones, and other materials. However, previous studies of ancient materials have been limited to those that are only tens of thousands of years old due to the degradation of organic compounds over time. In this study, Lüdecke’s team used a novel technique developed by Alfredo Martínez-García at the Max Planck Institute for Chemistry to measure nitrogen isotope ratios in tooth enamel that is millions of years old.
Diet Primarily Plant-Based
The isotope data from the tooth enamel of Australopithecus revealed that the nitrogen isotope ratios were consistently low, aligning more closely with those of herbivores and significantly lower than those of carnivores. These results suggest that while the diet of these early hominins may have varied, it was largely plant-based. The evidence indicates that Australopithecus did not regularly hunt large animals, unlike later hominins like Neanderthals. While it cannot be ruled out that they occasionally consumed animal protein sources such as eggs or termites, the overwhelming evidence points to a predominantly vegetarian diet.
Future Research Directions
Lüdecke and her team plan to expand their research by analyzing additional fossilized remains from different hominin species and from different time periods. Their goal is to explore the emergence of meat consumption and its potential evolutionary benefits. They will also study fossils from key sites in eastern and southern Africa, as well as southeast Asia, to gain a better understanding of the evolution of human diets.
“This innovative technique offers exciting prospects for unraveling the history of human evolution,” says Alfredo Martínez-García from the Max Planck Institute for Chemistry. “It holds the potential to answer critical questions, such as when our ancestors first incorporated meat into their diet and whether this change was linked to increases in brain size.”
“This research is a major breakthrough in understanding the diets and trophic positions of animals over millions of years,” adds Professor Dominic Stratford, Director of Research at the Sterkfontein Caves and co-author of the study. “The work conducted here at Sterkfontein, a site that has contributed so much to science since the discovery of the first hominin fossils in 1936, is a key milestone in advancing our understanding of human dietary evolution.”
