Evolutionary Specializations of the Human Prefrontal Cortex

It has been controversial whether the frontal lobes or the prefrontal cortex in particular, are selectively enlarged in the human brain. We report new analyses in an effort to settle the issue. We conclude that the proportions of the different lobes, including the frontal lobes, are similar in the brains of humans and great apes. However, within each of these lobes the association cortex has expanded in the human brain as a proportion of the lobe as a whole. Allometric analyses suggest that this effect is more dramatic for the prefrontal cortex than for other association areas. We argue that this enlargement most likely occurred in the last 200. 000 years during the evolution of our direct ancestors. During this period these ancestors were moving into new environmental niches and facing severe problems that threatened survival. We propose that the selective advantage of prefrontal enlargement related to the ability to solve these problems by behavioral adaptations.