From BBC:
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 note that cooking became commonplace much later. They argue that it was the stone tools, not cooking, that made the difference.
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.
They tested their idea on human subjects.
The findings suggest that by eating a diet of one-third meat, and using stone tools to process the food – slicing the meat and pounding the plant material – early humans would have needed to chew 17% less often and 26% less forcefully.
In their paper, Lieberman and Zink argue: “We further surmise that meat eating was largely dependent on mechanical processing made possible by the invention of slicing technology. More.
Can we be sure when cooking got started?
See also: Human origins: The war of trivial explanations
Neanderthals started fires with Mn compound?
and
Did Neanderthals follow the Paleo diet? Yes if it includes plenty of mammoths and rhinoceros