Long before humans acquired an appetite for meat, one of our earliest hominin ancestors Australopithecus stuck to a vegetarian diet. The ancient hominin, living in eastern and southern Africa around 3.5 million years ago, ate primarily plant-based foods, according to a new study that analyzed their fossilized teeth.The study, published in the journal Science, marks the latest chapter in the hunt to unearth the foundation of humans carnivorous tendencies. Scientists have regularly speculated about when our ancestors began to consume meat, coinciding with the growth of the brain and the development of tools.It appears that Australopithecus did not start this trend, as the study concluded that they likely did not hunt animals for consumption like later hominins did. Teeth From the Cradle of HumankindThe process used by researchers to confirm Australopithecus' vegetarian diet involving a new technique to measure nitrogen isotope ratios in fossilized teeth has proven to be an instrumental tool in studying ancient diets.The research team turned to tooth enamel from Australopithecus individuals originally found in the Sterkfontein cave near Johannesburg, South Africa; this cave is part of a system of influential archaeological sites, famously known as the Cradle of Humankind and recognized as a UNESCO World Heritage Site.The researchers compared isotopic data of the Australopithecus enamel with tooth samples from coexisting animals, including monkeys, antelopes, and large predators like hyenas, jackals, and big cats.Fossilized teeth analysis has become the crux of numerous archaeological studies, mainly because the teeth act like records of ancient diets.Tooth enamel is the hardest tissue of the mammalian body and can preserve the isotopic fingerprint of an animals diet for millions of years, said geochemist Tina Ldecke of the Max Planck Institute for Chemistry and the Johannesburg-based University of the Witwatersrand, in a statement.An Ancient Plant-Based DietWhen studying what a species ate millions of years ago, the nitrogen isotopes found in teeth provide valuable answers. This is due to the ratio of light and heavy isotopes of nitrogen (nitrogen-14 and nitrogen-15 respectively) in the body, which varies based on the type of food a species consumes.Products of bodily waste, such as urine, feces, and sweat, tend to contain high proportions of light nitrogen, leading to an increase in the ratio of heavy nitrogen to light nitrogen in comparison to the food eaten by a species. Essentially, the ratio between heavy and light nitrogen increases in higher levels of the food chain. Herbivores have a higher nitrogen isotope ratio than the plants they eat, and carnivores have a higher nitrogen isotope ratio than the prey they eat.The research team found that nitrogen isotope ratios in the tooth enamel of Australopithecus were consistently low, similar to ones examined in herbivores and also lower than ones examined in contemporary carnivores.This suggests that the diet of Australopithecus mostly consisted of plant-based foods, albeit with some variation; they wouldnt have hunted large mammals for consumption, an activity that appeared in Homo erectus and Neanderthals a few million years later. Although Australopithecus seemingly had no need to nourish themselves with meat from larger animals, the researchers say there is a chance they still ate some animal protein sources like eggs or termites.Previous research has shown that Australopithecus afarensis, a species of australopithecine that lived in East Africa from around 3.9 million years to 3 million years ago, likely had a diet of grasses, sedges, and succulents typically found in tropical savannas and deserts.Read More: Which Animals Did Early Humans Mainly Hunt?Continuing the Carnivore SearchNow that researchers are certain that Australopithecus isnt the starting point of early humans' affinity toward meat-based diets, they will now seek data from different hominin species.The team plans on examining fossils from additional sites across southern and eastern Africa, as well as southeast Asia, to obtain clues on the origins of human meat consumption. Questions on this puzzle and its implications for evolution persist, but they may one day be answered by looking at what lies within the teeth of extinct species.This method opens up exciting possibilities for understanding human evolution, and it has the potential to answer crucial questions, for example, when did our ancestors begin to incorporate meat in their diet? And was the onset of meat consumption linked to an increase in brain volume? said geochemist Alfredo Martnez-Garca of the Max Planck Institute for Chemistry, in the release. Article SourcesOur writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:Natural History Museum. Australopithecus afarensis, Lucy's speciesJack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.