By 1.8 million years ago, Homo erectus sliced up raw meat with stone tools before eating it…It was a momentous move, making it possible to consume more calories while reducing chewing effort…Faces and jaws got smaller while an energy-rich diet allowed brains and bodies to enlarge…Evolutionary shrinkage of bones and muscles involved in chewing affected other parts of the body, …An expanded vocal tract boosted the ability to make speech sounds. And a repositioned spinal cord, resulting from realignment of the base of the skull, increased the ability to walk and run long distances.
Cooking made it even easier to chew and digest meat and edible plants …hominids began to regularly cook food only about 500,000 years ago. Cooking stimulated further jaw and facial shrinkage in Homo sapiens, but not in H. erectus…Instead, a taste for sliced, raw meat got those facial changes off to a fast start in H. erectus, the scientists conclude.
Researchers have long noted that H. erectus skulls display relatively smaller jaws and faces than hominid species from more than 2 million years ago that preceded the Homo genus.
…H. erectus would have needed to chew its food 17 percent less often — more than 2.5 million fewer chews per year — and 26 percent less forcefully than if only unprepared plants were consumed, the scientists estimate.
The new study provides the first evidence for a decades-old assumption that tool-assisted meat eating prompted the evolution of smaller faces in early Homo… “The key is the consumption of sliced meat, enabled by the use of stone tools.”