Processing food likely helped human evolution

March 10, 2016

Breaking food into smaller, more easily digested pieces may have helped allow early human ancestors to evolve into humans, according to a paper out of Harvard University that appeared in Nature.

Researchers have long wondered how human ancestors were able to develop smaller teeth, faces, and guts while also receiving enough energy from their food for their bigger brains and bodies before cooking was invented. According to the paper, around 2 to 3 million years ago, human ancestors began using stone tools to process their food, reducing the amount of time and effort needed to chew it.

“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," says Katie Zink, the first author of the study, and a lecturer working in the lab of Daniel Lieberman, the Edwin M. Lerner II Professor of Biological Sciences. “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.”

In the study, the researchers asked volunteers to chew raw goat meat to approximate the toughness and texture of the game that early humans ate and used instruments attached to their jaws to measure the effort involved.

“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,” says Lieberman. “But once you start processing it mechanically, even just slicing it, the effects on chewing performance are dramatic.”

“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,” he adds. The time saved from chewing, which most mammals must spend almost all of their days doing, also freed humans to spend that time hunting and gathering and ultimately creating communities of shared labor.

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