Total number of neurons— not enlarged prefrontal region —hallmark of human brain

A new scientific study puts the final nail in the coffin of 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.

“People need to drop the idea that the human brain is exceptional,” said Vanderbilt University neuroscientist Suzana Herculano-Houzel, who directed the study. “Our brain is basically a primate brain. Because it is the largest primate brain, it does have 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.”

In her popular science book The Human Advantage: A New Understanding of How Our Brain Became Remarkable (MIT Press: March 2016), Herculano-Houzel explains how human brains grew so large, even larger than the brains of gorillas and orangutans, whose bodies are larger than ours. Her answer is surprisingly simple. It is the invention of cooking.

Cooking allowed early humans to overcome the energetic barrier that limits the size of the brains of other primates, she has determined. However, when the human brains grew larger they maintained the basic structure of the primate brain, including the size of the prefrontal cortex, her latest study has found.

The comparison of the relative size of the prefrontal region in primate brains is described in a paper titled “No relative expansion of the number of prefrontal neurons in primate and human evolution” by Herculano-Houzel and postdoctoral fellow Mariana Gabi published online this week in the Proceedings of the National Academy of Sciences early edition.

PR:https://news.vanderbilt.edu/2016/08/09/total-number-of-neurons-not-enlarged-prefrontal-region-hallmark-of-human-brain/

Book:https://mitpress.mit.edu/books/human-advantage