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Meat and tools, not the advent of cooking, was the trigger that freed early humans to develop a smaller chewing apparatus, a study suggests.
This in turn may have allowed other changes, such as improved speech and even shifts in the size of the brain.
The authors conclude that cooking became commonplace much later.
Prof Daniel Lieberman and Dr Katherine Zink from Harvard University have published their work in the journal Nature.
The earliest members of our genus, Homo, are only sparsely represented in the fossil record.
By the time the species Homo erectus appeared about two million years ago, humans had evolved bigger brains and bodies that had increased our daily energy requirements.
But paradoxically, they had also evolved smaller teeth, as well as weaker chewing muscles and bite force. They also had a smaller gut than earlier human ancestors.
One of the possible reasons for these changes, cooking, did not become commonplace until 500,000 years ago, the researchers found. This means that it probably did not play a significant role in the evolution of smaller chewing muscles and teeth.
“If you were to go and spend time with chimpanzees, you’d find that they spend.. about half of their day chewing,” said Prof Lieberman.
“At some point in human evolution, there was a shift – we started to eat less. This shift is made possible by two factors: we eat a much higher quality diet than our ancestors, but we also eat food that has been heavily processed.”
Read full, original post: Meat eating accelerated face evolution