Unearthing the Past: Our Ancestors’ Surprising Vegetarian Journey

Long before humans developed a taste for meat, one of our earliest hominin predecessors — Australopithecus — adhered to a plant-based diet. Living in eastern and southern Africa circa 3.5 million years ago, the ancient hominin primarily consumed raw plant foods, as per a recent study that examined their fossilized dental remains.

The research, published in the journal Science, represents a significant milestone in the quest to uncover the roots of humans’ meat-eating behaviors. Researchers have often speculated about when our forebears began incorporating meat into their diet, coinciding with the enlargement of the brain and the creation of tools. It seems that Australopithecus did not initiate this pattern, as the study concluded they likely refrained from hunting animals for food, unlike later hominins.

Dental Evidence From the Cradle of Humankind

The technique employed by scientists to validate Australopithecus’‘ plant-based diet — utilizing a novel approach to assess nitrogen isotope ratios in fossilized teeth — has proven to be an effective method in examining ancient nutrition.

The research team examined dental enamel from Australopithecus specimens discovered initially in the Sterkfontein cave close to Johannesburg, South Africa; this cave forms part of a series of significant archaeological locations renowned as the Cradle of Humankind and recognized as a UNESCO World Heritage Site.

The scientists compared the isotopic information of the Australopithecus enamel with dental samples from contemporaneously existing animals, including monkeys, antelopes, and large predators such as hyenas, jackals, and big cats.

The examination of fossilized teeth has become a cornerstone of numerous archaeological inquiries, largely because teeth serve as records of ancient eating habits.

“Tooth enamel is the most resilient substance in the mammalian body and can retain the isotopic signature of an animal’s diet for millions of years,” stated geochemist Tina Lüdecke from the Max Planck Institute for Chemistry and the University of the Witwatersrand in Johannesburg, in a statement.

Learn More: Fossils From The Cradle Of Humankind Might Be Much Older Than Previously Believed

An Age-Old Plant-Centric Diet

When researching what a species consumed millions of years ago, nitrogen isotopes in teeth yield significant insights. This is because the balance of lighter and heavier nitrogen isotopes (nitrogen-14 and nitrogen-15, respectively) within a body varies according to the food type a species ingests.

Waste products from bodily functions, such as urine, feces, and sweat, typically contain a high amount of lighter nitrogen, resulting in a higher ratio of heavier nitrogen to lighter nitrogen in comparison to the food consumed by a species. Essentially, the proportion of heavier to lighter nitrogen increases at higher levels of the food chain. Herbivores display a greater nitrogen isotope ratio than the plants they consume, while carnivores exhibit a greater nitrogen isotope ratio than their prey.

The research indicated that nitrogen isotope ratios in the dental enamel of Australopithecus were consistently low, resembling those found in herbivores and also lower than those found in contemporary carnivores.

This implies that the nutrition of Australopithecus predominantly comprised plant-based materials, although with some fluctuations; they would not have engaged in hunting large mammals for food, a behavior that emerged in Homo erectus and Neanderthals several million years later. While Australopithecus seemed to lack the necessity to sustain themselves with meat from larger beasts, researchers suggest that there exists a possibility they may have consumed some animal protein sources, such as eggs or termites.

Prior studies have indicated that Australopithecus afarensis, a species of australopithecine that existed in East Africa from around 3.9 million to 3 million years ago, probably had a diet rich in grasses, sedges, and succulents commonly found in tropical savannas and deserts.

Learn More: What Animals Did Early Humans Primarily Hunt?

Pursuing the Carnivore Inquiry

Now that scientists have established that Australopithecus is not the origin of early humans’ preference for meat-centric diets, they will now pursue information from various hominin species.

The team intends to investigate fossils from additional locations throughout southern and eastern Africa, as well as southeast Asia, to gather insights regarding the beginnings of human meat consumption. Questions surrounding this enigma and its relevance to evolution remain, yet they may ultimately be resolved by examining what resides within the teeth of extinct species.

“This technique presents thrilling opportunities for comprehending human evolution, and it holds the potential to resolve pivotal questions, such as when did our ancestors start incorporating meat into their diets? And was the onset of meat consumption associated with an increase in brain size?” remarked geochemist Alfredo Martínez-García from the Max Planck Institute for Chemistry, in the release.

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Jack Knudson is an assistant editor at Discover with a keen interest in environmental science and history. Prior to joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously completed an internship at Recycling Today magazine.