A groundbreaking study led by a team of climate geochemists from the Max Planck Institute for Chemistry, University of the Witwatersrand, and Princeton University has uncovered new evidence about the diet of early hominins in South Africa. The research, published in the prestigious journal Science, suggests that early hominins, particularly Australopithecus africanus, had a predominantly vegetarian diet, challenging the prevailing theory that human evolution, including the development of upright posture and large brains, was driven by the consumption of meat.
The Diet of Early Hominins
For decades, scientists have pondered what factors led to the remarkable evolution of early humans. A popular theory posits that the shift from a vegetarian diet to a more carnivorous one was a key driver in the development of traits such as bipedalism (upright walking) and the expansion of brain size. According to this hypothesis, the switch to a meat-heavy diet provided early hominins with the necessary nutritional resources to fuel brain development. However, the new findings from this team of researchers provide compelling evidence against this idea.
The team conducted isotopic analysis on fossilized teeth excavated from the Sterkfontein Caves in South Africa, one of the richest archaeological sites for early human fossils. By studying the nitrogen and carbon isotopes bound to the tooth enamel, the researchers were able to reconstruct the diet of early hominins that lived approximately 3.5 million years ago. This isotopic technique is particularly valuable because it can provide insight into the types of plants or animals an individual consumed during their lifetime, even after millions of years have passed.
The Methodology: Isotopic Analysis of Fossilized Teeth
In their study, the researchers analyzed the isotopic composition of 43 fossilized teeth. Seven of the teeth came from Australopithecus africanus, a species of early hominin, while the remaining samples were from five different mammalian families, providing a broad comparison across various dietary patterns. The teeth from modern species, both herbivores and carnivores, were also analyzed to provide a baseline for comparison.
Carbon and nitrogen isotopes are particularly informative when it comes to determining dietary habits. Carbon isotopes can reveal whether an organism relied on plants that use a C3 photosynthetic pathway (typically associated with trees and shrubs) or a C4 pathway (commonly associated with grasses). Nitrogen isotopes, on the other hand, can indicate the trophic level an organism occupied in the food chain, with higher nitrogen isotope ratios generally pointing to carnivorous diets.
The analysis revealed that the isotopic ratios found in the teeth of Australopithecus africanus closely resembled those of modern herbivores, indicating that these early hominins had a plant-based diet, rather than one that included a significant amount of meat.
Rethinking the “Meat Hypothesis”
The findings challenge a long-standing hypothesis that a shift to carnivory played a critical role in human evolution. This theory, which has been central to many discussions about the development of early hominins, suggests that consuming meat allowed our ancestors to obtain the extra energy needed to support larger brains and more complex social structures. The idea is that animal protein provided a richer, more calorie-dense food source, which could have driven physiological changes.
However, the new evidence from the Australopithecus africanus fossils suggests that early hominins did not rely heavily on meat. Instead, their diet appears to have been largely plant-based, with evidence pointing to a mix of fruits, leaves, and other plant materials. This finding is in line with earlier studies that have suggested that hominins may have consumed a varied diet that included both plant material and small amounts of animal matter, but meat did not appear to play a central role in their sustenance.
The researchers acknowledge that their findings do not entirely rule out the possibility that some hominins may have incorporated more meat into their diet later on. It is possible that a significant dietary shift occurred in later hominin species, potentially contributing to the dramatic evolutionary changes seen in later stages, such as the emergence of larger brains and the development of more advanced social behaviors. However, the team suggests that the role of meat consumption in these transformations may have been overstated in earlier theories.
A Varied but Largely Plant-Based Diet
While the early hominins analyzed in the study were primarily herbivores, the researchers also found evidence suggesting a varied diet. The isotopic signatures indicated that these hominins may have supplemented their plant-based diet with small amounts of animal protein, such as insects or small vertebrates. This finding is consistent with the idea that early hominins had an opportunistic feeding strategy, eating a wide variety of food sources depending on availability.
Interestingly, the research also highlighted that while meat was not a major component of the diet for Australopithecus africanus, the possibility of increased meat consumption in subsequent hominin species remains plausible. For instance, later hominins, such as Paranthropus and Homo habilis, likely included more meat in their diet, as evidenced by tools and butchering marks found on animal bones at archaeological sites.
This nuanced view of early hominin diets challenges the traditional narrative that human evolution was driven primarily by a shift to meat consumption. Instead, it suggests that a more complex interplay of dietary factors—combining plant-based foods with the occasional intake of animal matter—may have been at work, with important implications for understanding the evolution of early human ancestors.
Implications for Human Evolution
The findings from this study are significant not only for their implications about the diet of early hominins but also for the broader field of human evolution. The idea that early hominins may have relied more heavily on plant-based diets challenges assumptions about the relationship between diet and the development of key human traits, such as brain size and bipedalism.
Researchers have long debated how changes in diet influenced the evolution of human traits. One of the prevailing ideas has been that the switch to a more carnivorous diet provided early hominins with the nutritional resources needed to support larger brains. However, if early hominins were primarily herbivorous, it raises questions about what other factors might have contributed to the development of larger brains. The role of environmental pressures, social behavior, and tool use, for example, may have been more influential than previously thought.
Moreover, this study underscores the importance of using interdisciplinary approaches, such as isotopic analysis, to investigate ancient diets. By studying fossilized teeth, researchers can gain a much more accurate and detailed picture of the diets of early hominins than has previously been possible through skeletal morphology alone. This kind of research also opens up new avenues for exploring how diet, climate, and environmental factors influenced the evolutionary pathways of different hominin species.
Conclusion
The new research on the diet of early hominins in South Africa challenges long-standing theories about the role of meat consumption in human evolution. By analyzing isotopic ratios in fossilized teeth, scientists have provided compelling evidence that Australopithecus africanus and other early hominins consumed a largely plant-based diet. While the possibility of increased meat consumption in later hominin species remains, the findings suggest that the dietary shift from vegetarianism to carnivory may not have been as pivotal in human evolution as once thought.
This study not only adds a crucial piece to the puzzle of human evolution but also demonstrates the power of modern scientific techniques to shed light on ancient behaviors and lifestyles. As researchers continue to explore the diets and habits of early hominins, these findings may help refine our understanding of the complex factors that drove the evolution of our ancestors.
Reference: Tina Lüdecke et al, Australopithecus at Sterkfontein did not consume substantial mammalian meat, Science (2025). DOI: 10.1126/science.adq7315