The Raw and the Cooked

Human evolution may have gained much from the extra energy cooking made available

What is cooking good for? Many answers have been advanced: it makes food easier to digest, preserves meat, avoid parasites and infections; but there is one answer that has come up in the course of a Harvard study published in Proceedings of the National Academy of Sciences that may matter as much if not more than any of these reasons. It seems cooked food provides us more energy than raw food does.

Rachel Carmody, graduate student at Harvard, fed two groups of mice a series of diets that consisted of either meat or sweet potatoes prepared in four ways—raw and whole, raw and pounded, cooked and whole, and cooked and pounded—over 40 days. The results showed that cooked meat delivered more energy to mice than raw. The distinction here is important. It is not that cooked meat has more energy, it is that we can benefit more from energy in cooked food.

This lends support to the theory that it is cooking that provided the fuel for a sudden expansion in human body and brain size approximately 1.9 million years ago. This theory had been advanced years earlier by Richard Wrangham, but it wasn't until Carmody's work that scientists had hard evidence to either support or refute it.

"I'm a biologist by training," Wrangham has said. "If you want to understand the anatomical, physiological and behavioural features of a species, its diet is the first thing you ask about… But with humans, everyone had said what's key about humans is the fact that we are variable, that we are good at solving problems, so human adaptation in general is the result of our brains. But this, right away, strays from the fundamental biological concept of diet… For the first time, we have a clear answer to why cooking is so important cross culturally and biologically—because it gives us increased energy, and life is all about energy."