Humans love to try to find what makes us different from other animals, but as it turns out, the difference might not be exactly what you’d expect: We spend a lot less time and energy chewing food. In fact, it was this very difference that pushed us to evolve into humans, according to a new study out of Harvard.
A normal human might spend a few hours eating, but our closest living relatives, chimpanzees, spend half of every day chewing—a difference that started two or three million years ago, when our ancestors added meat to their diet and began to process food using stone tools.
Fire wasn’t invented for another 1.5 to 2.5 million years—and the researchers were curious about what ancient humans did when cooking wasn’t an option. They hypothesized that processing raw food by slicing or pounding it drastically decreased chewing effort, to the point that our ancestors began to evolve different head and facial features—granting us smaller mouths and larger brains.
Studying chewing patterns
To test this idea, the team recruited participants to come chew vegetables and raw, sliced, pounded, or cooked goat meat—which they approximated was the best equivalent to the game early humans ate—while the researchers used instruments to measure how much jaw effort was needed to chew. After chewing the food to the point where they would normally swallow, it was spit out and analyzed.
“What we found was that humans cannot eat raw meat effectively with their low-crested teeth. When you give people raw goat, they chew and chew and chew, and most of the goat is still one big clump – it’s like chewing gum,” said co-author Daniel Lieberman, the Edwin M. Lerner II Professor of Biological Sciences, in a statement. “But once you start processing it mechanically, even just slicing it, the effects on chewing performance are dramatic.”
In fact, according to the study in Nature, by using these simple processing techniques, ancestral humans made 20 percent fewer chews per day—adding up to 2.5 million fewer chews per year. Cutting or pounding the food into smaller pieces also made it much easier for our stomachs to digest.
The evolution of the ability to chew food into smaller particles gave mammals a big boost of extra energy because smaller particles have a higher surface area to volume ratio, allowing digestive enzymes to then break food down more efficiently,” said Lieberman.
Naturally, this allowed us to save enormous amounts of time and energy all around—which had huge consequences.
“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.
“Those changes, and others, allowed for selection for speech and other shifts in the head, like bigger brains. Underlying that, to some extent, is the simplest technology of all: slicing meat into smaller pieces, and pounding vegetables before you chew them.”
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Image credit: Thinkstock
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