The Energetic Cost of Chewing May Have Shaped Hominin Evolution

Amazing stuff! A very clever approach to use chewing gum for this research! How much did this actually affect our facial appearance (muscles, tendons, bones, blood vessels etc.)?

Masticatory effort, what a teeth gnashing term!  Are these researchers suggesting that chewing is like going to a gym for a physical workout? Let me chew on that for a while! 😊

"Back before the advent of cooking, our early hominid ancestors probably spent a lot of time chewing. ...
Estimates for how long humans have been cooking range from 500,000 to 2 million years ago ... Our ability to draw out excess calories from meats and starchy foods via heat and tool use “changed the entire energetics of modern humans. And basically, you could say it’s allowed the formation of a very large brain.” In this way, the metabolics of chewing is still “one of the fundamental questions of evolution,” ...
Based on a back-of-the-envelope calculation of how much time chimpanzees spend chewing, our early hominid ancestors may have been chewing for five or six hours a day, he says, which may have cost them up to 5 percent of the energy they consumed. It’s possible that this drove the evolution of the form or muscle architecture of the jaw, or changes in tooth morphology ..."

From the abstract:

"Any change in the energetic cost of mammalian mastication will affect the net energy gain from foods. Although the energetic efficiency of masticatory effort is fundamental in understanding the evolution of the human masticatory system, nothing is known currently about the associated metabolic costs of chewing different items. Here, using respirometry and electromyography of the masseter muscle, we demonstrate that chewing by human subjects represents a measurable energy sink. Chewing a tasteless odorless gum elevates metabolic rate by 10 to 15% above basal levels. Energy expenditure increases with gum stiffness and is paid for by greater muscle recruitment. For modern humans, it is likely that mastication represents a small part of the daily energy budget. However, for our ancestors, before the onset of cooking and sophisticated food processing methods, the costs must have been relatively high, adding a previously unexplored energetic dimension to the interpretation of hominin dentofacial fossils."

The Energetic Cost of Chewing May Have Shaped Hominin Evolution | The Scientist Magazine® The simple act of chewing gum can raise the body’s metabolic rate by as much as 15 percent, a study finds.

The cost of chewing: The energetics and evolutionary significance of mastication in humans (open access)