What significance for the development of mankind had such a human attribute as the volume of the brain?

In the process of evolution, the human brain developed rather quickly. It increased in volume, many convolutions appeared and its various lobes developed. Thanks to this, other changes took place. It was thanks to the developed brain that we adapted. The frontal lobe developed first. She is responsible for thinking, perception of the surrounding world and more. Therefore, the “skillful man” gradually turned into a “reasonable man.” Now our brain is also developing, but it is impossible to notice this in a short time.