New research published in the scientific journal Science reveals that human ancestors like Australopithecus, who lived approximately 3.5 million years ago in southern Africa, consumed very little to no meat. This finding is based on an analysis of nitrogen isotopes found in the fossilized tooth enamel of seven Australopithecus specimens. The results indicate that these early relatives mainly had plant-based diets, with minimal evidence of meat intake.
The inclusion of meat in diets is seen as a significant milestone in human evolution. Meat, being rich in protein, has been associated with increases in brain size and the development of tool-making abilities. However, pinpointing the time period when early humans began consuming meat, and how that developed over time, has been a challenge. Researchers from the Max Planck Institute for Chemistry in Germany and the University of the Witwatersrand in South Africa have now presented evidence that the Australopithecus species in southern Africa, living between 3.7 and 3.3 million years ago, primarily thrived on a diet rich in plants.
The research involved examining stable isotope data from tooth enamel of Australopithecus found in the Sterkfontein Cave, located near Johannesburg, which is part of South Africa’s “Cradle of Humankind,” an area known for its extensive early hominin fossil collection. The team compared the isotopic data from the Australopithecus teeth with samples from local animals, including monkeys, antelopes, and large predators like hyenas, jackals, and big cats.
Dietary Signatures Found in Tooth Enamel
“Tooth enamel is the hardest tissue found in mammals and can maintain the isotopic record of an animal’s diet for millions of years,” explains geochemist Tina Lüdecke, who led the study. Lüdecke has been heading the “Emmy-Noether Junior Research Group for Hominin Meat Consumption” at the Max Planck Institute for Chemistry since 2021 and is an Honorary Research Fellow at the University of the Witwatersrand. She often travels to Africa to collect fossilized teeth for her studies. Wits University is the custodian of the Australopithecus fossils found in Sterkfontein.
When animals process food, the lighter nitrogen isotope (14N) is favored by biochemical reactions. Consequently, the waste products from their bodies are richer in this lighter isotope. This leads to a higher ratio of the heavier nitrogen isotope (15N) in their body compared to the food they eat. This means that herbivores will have a higher nitrogen isotope ratio than the plants they consume, while carnivores will have a higher ratio than their prey. Thus, a higher ratio of 15N to 14N in a tissue sample suggests a higher trophic level within the food web.
Nitrogen isotope ratios have been effectively used to analyze the diets of modern animals and humans through various organic materials such as hair, claws, and bones. However, in ancient fossils, these measurements were previously limited to samples that are relatively young, just a few tens of thousands of years old, due to the degradation of organic materials over time. In this study, Tina Lüdecke employed a new method developed at the Max Planck Institute for Chemistry to measure nitrogen isotope ratios in fossilized tooth enamel that is millions of years old.
Evidence Indicating a Plant-Based Diet
The research team discovered that while nitrogen isotope ratios in the tooth enamel of Australopithecus showed some variability, they were consistently low, akin to those of herbivores, and much lower than those of current carnivores. This leads them to conclude that these early hominins maintained a diet mostly or entirely composed of plant-based foods. As such, it is unlikely that Australopithecus engaged in regular hunting of large mammals, unlike Neanderthals did millions of years later. Although the researchers cannot completely dismiss the possibility of rare consumption of animal proteins such as eggs or termites, the evidence strongly suggests a predominantly vegetarian diet.
Expanding Fossil Enamel Research
Lüdecke’s team plans to broaden their research by gathering additional data from various hominin species and different time periods. They aim to analyze fossils from other crucial sites across eastern and southern Africa and southeast Asia to investigate when meat consumption began, how it evolved, and if it offered any evolutionary advantages for our ancestors.
“This method opens up exciting new avenues for exploring human evolution and could help answer vital questions, such as when did our ancestors start including meat in their diets? And was the shift towards meat consumption connected to an increase in brain size?” remarks Alfredo MartÃnez-GarcÃa from the Max Planck Institute for Chemistry.
“This study marks a significant advancement in our capacity to understand the diets and trophic levels of all animals over millions of years. The findings clearly demonstrate that the Australopithecus diet lacked significant meat content. We are proud that the groundbreaking use of this new method was initiated at Sterkfontein, which has been making substantial contributions to scientific knowledge for 89 years since Robert Broom discovered the first hominin fossils there,” says Professor Dominic Stratford, Research Director at the Sterkfontein Caves and co-author of the study.
The research received funding from the Max Planck Society, and Tina Lüdecke’s research group is supported by the Emmy Noether program of the German Research Foundation (DFG).
