Total number of neurons, not enlarged prefrontal region, is hallmark of human brain

A new scientific study ends a long-standing theory to explain human’s remarkable cognitive abilities: that human evolution involved the selective expansion of the brain’s prefrontal cortex.
It does so by determining that the prefrontal region of the brain which orchestrates abstract thinking, complex planning and decision making contains the same proportion of neurons and fills the same relative volume in non-human primates as it does in humans.
Scientists behind the study caim that people need to drop the idea that the human brain is exceptional. Our brain is nothing but a primate brain with one distinctive feature: It has the highest number of cortical neurons of any primate. Humans have 16 billion compared with 9 billion in gorillas and orangutans and six-to-seven billion in chimpanzees. It is remarkable, but it is not exceptional.

http://news.vanderbilt.edu/2016/08/...ed-prefrontal-region-hallmark-of-human-brain/