Study: Chopping food, eating meat helped ancient humans evolve

Slicing up a mound of raw food isn’t just a tedious chore on the way to dinner. Chopped food, along with an embrace of meat, helped make us human, new evidence suggests.

Both meat consumption and the Paleolithic version of kitchen prep paved the way for major changes in the anatomy of ancient humans, according to a study in this week’s Nature. Stone Age humans evolved smaller faces and teeth after they threw off vegetarianism and began investing a little more time on their meals, the study argues.

Those anatomical changes not only made early humans look more like the Homo sapiens we know today, but also may have helped them run and talk.

Previous research highlighted cooking as a turning point in the evolution of our species. The researchers involved in the new study say cooking alone can’t explain the major renovations of the head and face seen in our ancestors living 2 to 3 million years ago.

“Cooking is important, but it’s not the whole story,” says Harvard University’s Daniel Lieberman, an author of the new study. “What we show in this paper is that food processing” – slicing and pounding – “had really important and profound effects.”

The paper also stands out for depending on locally sourced goat carcasses. Lieberman and his Harvard colleague Katherine Zink fed raw goat meat, yams, carrots and beets to intrepid volunteers “nice enough to chew for science,” Zink says. As the volunteers chomped, the scientists measured the number and forcefulness of their chews.

The volunteers’ teeth couldn’t break down the tough goat. But when the meat was sliced into small pieces, the volunteers needed fewer chews before being able to swallow. The same was true with veggies pounded with a stone versus those eaten intact.

The scientists calculate that adding meat, especially sliced meat, to the diet allowed early humans to tuck away just as many calories with less jaw action. That may explain the relatively small teeth and chewing muscles of the early human Homo erectus, which appeared soon after meat-eating and stone tools became popular. Without the need for massive food-processing gear, early humans were free to evolve smaller snouts, better for running, and shorter jaws, better for speech.

Researchers who weren’t involved with the study praised its authors for examining prehistoric food trends besides cooking. Matt Sponheimer of the University of Colorado, Boulder, said ancient humans may not have eaten much meat, but he finds it plausible that chopping and pounding helped shape human anatomy.

The researchers’ Harvard colleague Richard Wrangham disputes the idea that cooking didn’t play a role in smaller teeth and jaw muscles. As evidence, he cites Homo erectus’s relatively small digestive tract, which he says couldn’t glean enough calories from raw plants.

Lieberman responds that little is know for sure about the guts of early humans. Solid evidence that early humans were routinely roasting their antelope haunch doesn’t appear until 500,000 years ago, well after Homo erectus arrived on the scene.

“If there’s (earlier) evidence of fire, we don’t have it,” Lieberman says. “But what we do have evidence for is food processing. … You don’t have to invoke cooking to see what we see.”