Impact of meat and Lower Palaeolithic food processing techniques on chewing in humans

The genus Homo had considerably smaller cheek teeth, chewing muscles and jaws than earlier hominins; here, the introduction of raw but processed meat, from which energy could more easily be extracted, is shown to have possibly been responsible for this change. Food processing in the Palaeolithic era The arrival of Homo erectus almost two million years ago introduced hominins with dramatically smaller teeth than anything that went before, implying a reduced capacity for processing the amount of food required to sustain a large animal. It is often claimed that the development of cooking allowed for tooth reduction, but cooking didn't become common until about 500,000 years ago. What happened in the interim? Katherine Zink and Daniel Lieberman tested the effects of eating meat — and of simple food preparation techniques — on masticatory effort and oral fracture efficiency. Their findings suggest that the introduction of raw yet eminently chewable meat could have made the difference — together with the use of stone tools to pound the less digestible but starch-rich storable plant materials. The origins of the genus Homo are murky, but by H. erectus , bigger brains and bodies had evolved that, along with larger foraging ranges, would have increased the daily energetic requirements of hominins 1 , 2 . Yet H. erectus differs from earlier hominins in having relatively smaller teeth, reduced chewing muscles, weaker maximum bite force capabilities, and a relatively smaller gut 3 , 4 , 5 . This paradoxical combination of increased energy demands along with decreased masticatory and digestive capacities is hypothesized to have been made possible by adding meat to the diet 6 , 7 , 8 , by mechanically processing food using stone tools 7 , 9 , 10 , or by cooking 11 , 12 . Cooking, however, was apparently uncommon until 500,000 years ago 13 , 14 , and the effects of carnivory and Palaeolithic processing techniques on mastication are unknown. Here we report experiments that tested how Lower Palaeolithic processing technologies affect chewing force production and efficacy in humans consuming meat and underground storage organs (USOs). We find that if meat comprised one-third of the diet, the number of chewing cycles per year would have declined by nearly 2 million (a 13% reduction) and total masticatory force required would have declined by 15%. Furthermore, by simply slicing meat and pounding USOs, hominins would have improved their ability to chew meat into smaller partic