● New research paints a picture in which the population of large mammals declined resulting in an increase in human brain size.
● Evolution, the theory argues, favored large brain humans who could successfully hunt smaller, faster animals for food.
● Brain size has grown significantly over the past 2 million years, but there is controversy over why this is the case. Some say the increase was the result of many small environmental changes over time. Others argue there might have been one major change, like this one.