According to a new study, our ancestors between 2 and 3 million years ago started to spend far less time and effort chewing by adding meat to their diet and by using stone tools to process their food. The researchers estimate that such a diet would have saved early humans as many as 2.5 million chews per year, and made possible further changes that helped make us human.
One of the biggest puzzles in human evolution is how species such as Homo erectus evolved smaller teeth, smaller faces, and smaller guts, and yet managed to get more energy from food to pay for their bigger brains and bodies before cooking was invented. “What we showed is that…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” said 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.
By changing their diets to include just 33 percent meat, and processing their food — slicing meat and pounding vegetables — before eating, Zink and Lieberman found that the muscular effort required per chew and the number of chews required per day was reduced by almost 20 percent. They also found that by simply slicing meat with the sorts of simple tools available more than 2 million years ago, humans were able to swallow smaller, more easily digestible pieces than would have been possible without using tools. More. Paper. (paywall)
We looked at this work earlier: Tools and meat eating, not cooking (which came much later), speeded human evolution.
This account suffers from three basic problems that afflict all such accounts:
1. It explains what doesn’t need explaining. Processing (and preserving) food in a variety of ways across the globe is a great idea. But how did we come to develop the idea? That’s bound up with the origin of the human mind.
2. Such explanations attempt to place the burden of the origin of the mind on a single development that just sort of happened, when the evidence favours a large variety of interrelated developments. The latter pattern is not much explored for reasons unrelated to evidence.
3. We don’t really know when cooking got started; only the earliest date for which we have evidence. 300 kya? We don’t know fors ure it long postdated tools.
Researchers escape censure by settling for yet another one-size-fits-all suggestion, via creative research as in this case. But ten years from now, there will be dozens more.
Curiously, traditional mythologies often attributed the developments as the gifts of a friendly god. And it didn’t always turn out too well for the god.
Which at least warns us that the area has long been understood to be complex. If we’ve got an easy answer, it’s probably wrong.
See also: Human origins: The war of trivial explanations