After measuring ergonomic forces and energy expenditures, Zink and her research partners determined humans with processed food – empowered by tools and fire – were able to reduce the amount of chewing and energy expended while chewing by 20 percent.
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It’s not just a hobby.
Fellow Harvard scientist Richard Wrangham believes that cooking did play a role in developing smaller teeth and jaws.
At this stage cooking can be ruled out as evidence for this did not begin appearing until about 500,000 years ago. When they chew it enough, they had to spit out the food.
Slicing up a mound of raw food isn’t just a tedious chore on the way to dinner.
“If I were to give you raw goat”, Lieberman says, “you’d chew, and nothing would happen”.
There were similar declines in chewing and force when the veg was pounded with rocks before consumption, although meat – even tough goat – was always easier to chew down than the root veg. Researchers also attached instruments to the subject’s jaws to measure the effort.
“What we showed is that by processing food, especially meat, before eating it, humans not only decrease the effort needed to chew it, but also chew it much more effectively” said first author Katie Zink, a lecturer at Harvard University in US.
From the experiment, the researchers concluded that humans are not able to consume meat without help from processing.
The nutritional demands of a large brain would require more efficient eating, which has led to the idea that our vegetarian ape ancestors must have evolved into meat eaters.
“Eating meat and using stone tools to process food apparently made possible key reductions in the jaws, teeth and chewing muscles that occurred during human evolution”, Zink said. “We are partly who we are because we chew less”.
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“Cooking is important, but it’s not the whole story”.
Making that change, however, presented early humans with a new challenge. “You can think of it as being like a rubber band”, Zink said. These changes, in turn, might have supported the evolution of speech and language by changing human facial anatomy, scientists added.
Today we thoroughly enjoy our meals and spend very little time and physical effort chewing them.
LIEBERMAN: Most of the people listening to this, very rarely do we have to put any effort into anything we chew. This was probably the case for our earlier primate ancestors, too. About 50 percent of their day was spent chomping away, just to get enough calories.
“With hindsight, this makes sense”, Lieberman said.
“With the origin of the genus Homo, we went from having snouts and big teeth and large chewing muscles to having smaller teeth, smaller chewing muscles, and snoutless faces”, Lieberman said.
AUBREY: That was about two-and-a-half million years ago. They used to eat raw meat around two million years back. But they had figured out how to break sharp edges off stones to make stone blades, the precursor to modern knives. But if you were to cut that goat up into smallish pieces, your ability to chew that goat into smaller pieces would improve dramatically. “That’s about 2.5 million fewer chews per year”, Zink said. That’s an enormous difference.
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AUBREY: And all of this set our ancestors on the course to smaller teeth and faces and other major changes, too. It possessed larger brains and bodies than other hominins – members of the human family tree dating from the split from chimpanzees onward.
