One of the teeth from seven Australopithecus individuals that got drilled so a small amount of tooth enamel could be analyzed for evidence of meat consumption.
Tina Lüdecke
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Tina Lüdecke
A new study of early human ancestors who lived millions of years ago suggests that they were largely vegetarian, despite the fact that stone tools and cut animal bones have been found from that same time period.
The work marks an important advance in researchers’ ability to reconstruct ancient diets, because it involved developing a new method to look inside tooth enamel for evidence of eating meat.
Meat is of particular interest to paleoanthropologists because they believe that access to abundant high-protein foods must have been essential for the evolution of larger and more complex human brains.
“To power these big machines in our heads, we need a lot of energy, so of course we need high-quality, energy-rich foods,” explains Tina Lüdecke, a scientist at the Max Planck Institute for Chemistry in Germany.
Researchers have long known how to look for chemical signatures linked to the consumption of different types of plants, like grasses versus trees, she says, and have used them on ancient remains “just to get an idea who was in an open grassland savannah, who lived more in a forested environment.”
But the chemical tests used to probe plant consumption reveal nothing about meat consumption, says Lüdecke, “and I was always very frustrated, like many of us—what about meat?”
The Sterkfontein excavation site in South Africa, showing red sediments that contained Australopithecus fossils that were used in this study to recreate their ancient diet.
Dominic Stratford
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Dominic Stratford
Recently, she and her colleagues developed a highly sensitive new kind of chemical analysis that can find tell-tale signs of a meat-heavy diet. The testing involves detecting very, very small amounts of nitrogen in tiny amounts of organic material preserved in tooth enamel.
The researchers have just used it to study an ancient human ancestor called Australopithecus, which lived around 3 million years ago.
“These are still fairly ape-like, small-brained hominins, that already walked upright but had a more apelike walk,” she says.
She got permission to take samples from Australopithecus remains found in a South African cave, and used a dental drill to nab bits of tooth enamel from teeth that belonged to seven individuals.
When her team analyzed these samples and compared them to results from known carnivores and herbivores, they found that “all of these seven individuals were probably not engaging in a lot of meat consumption,” she says. “These were plant eaters, mostly.”
They might have eaten some energy-rich foods not revealed by this kind of testing, like legumes or termites, but the results, published in the journal Science, make it clear that they weren’t living a carnivore lifestyle.
“Here, for the first time, we have actual numbers to put on there to say, ‘Ok, not much meat was consumed for these small-brained hominins,’ ” says Lüdecke. “But then what happened after, right?”
She wants to do this same kind of testing on other past human relatives, to move up the evolutionary chain.
This work is an important step forward in ancient diet reconstruction, says Bernard Wood, a paleoanthropologist at The George Washington University. He wasn’t part of the research group but calls himself a “big fan” of this new research.
“It means that one can look at other hominins, and try and do the same kind of measurements, and try to get a sense of what they were consuming during life,” he says.
For example, he wonders about Homo habilis, an extinct human species that lived about two million years ago.
“It would be great to know whether Homo habilis was eating as much meat as some people think it was,” he says. “I have my doubts.”
The conventional wisdom about Australopithecus used to be that it was a meat-eater, he says, but this study shows it seems to have eaten “no more meat than a bunch of living primates and some groups of chimpanzees.”
