New study calls an old evolutionary assumption into question.
How hard-wired are humans to be carnivores? How central is meat-eating to our evolutionary history?
There’s a widespread belief that eating meat became much more common with the advent of big-brained Homo erectus, two million years ago, based on increased archaeological evidence of meat-eating from that point.
But new research in Proceedings of the National Academy of Sciences has called that belief into question, suggesting that the numbers don’t quite add up.
“Generations of paleoanthropologists have gone to famously well-preserved sites in places like Olduvai Gorge looking for — and finding — breathtaking direct evidence of early humans eating meat, furthering this viewpoint that there was an explosion of meat-eating after two million years ago,” says Dr Andrew Barr, assistant professor of anthropology at George Washington University, US, and lead author on the paper.
“However, when you quantitatively synthesise the data from numerous sites across eastern Africa to test this hypothesis, as we did here, that ‘meat made us human’ evolutionary narrative starts to unravel.”
The researchers examined data on animal bones from nine research areas in eastern Africa, comprising dates of between 2.6 and 1.2 million years ago.
They found that, once they’d accounted for variation in sampling over time, there was no evidence that meat-eating increased once Homo erectus appeared. While there was an increase in marked animal bones after the advent of Homo erectus, this was likely because sites from this time period had been more extensively studied and sampled.
“I’ve excavated and studied cut-marked fossils for over 20 years, and our findings were still a big surprise to me,” says co-author Dr Briana Pobiner, a research scientist at the Smithsonian’s National Museum of Natural History, US.
“This study changes our understanding of what the zooarchaeological record tells us about the earliest prehistoric meat-eating. It also shows how important it is that we continue to ask big questions about our evolution, while we also continue to uncover and analyse new evidence about our past.”
The researchers believe it’s important to investigate other explanations for the anatomical and behavioural differences that started to appear with Homo erectus. The development of controlled fire for cooking, for instance, might be one factor.
“I would think this study and its findings would be of interest not just to the palaeoanthropology community but to all the people currently basing their dieting decisions around some version of this meat-eating narrative,” says Barr.
“Our study undermines the idea that eating large quantities of meat drove evolutionary changes in our early ancestors.”