Dr Karen Hardy from the Catalan Institution for Research and Advanced Studies, along with an international team of experts on human evolution, genetics and environment, pulled together a wealth of data for their theory that – carbohydrate consumption, particularly in the form of cooked starch, was critical for the development of the human brain over the last million years.
Up to 25 per cent of the energy we make, and up to 60 per cent of our glucose, is used by our brain. Glucose is its preferred source of energy and a low carbohydrate diet makes it difficult to supply enough. Starches, an important source of glucose, were widely available to our ancestors in the form of tubers, fruits, seeds and nuts. Raw starches are not digested as well as cooked ones, when they change structure. During our last one million years of evolution we developed a significantly higher amount of the enzyme amylase, which is in our saliva and increases our ability to digest starch.
According to the theory, amylase genes increased once cooking became widespread and glucose for the brain became more available, which in turn enabled an increase in its size.
Hardy et al. 2015. The Importance of Dietary Carbohydrate in Human Evolution. The Quarterly Review of Biology. 90 (3) 251-268.