Human Evolution Not A Result Of Increased Size Of The Brain's Frontal Lobes: A Study

The evolution of the human brain is not, contrary to popular belief, a matter of the size of the frontal lobes, argues anthropologist Robert Barton of Durham University in his new study published in the Proceedings of the National Academy of Sciences.

Rather, by using a new method used to detect shifts in evolutionary rates, he and his colleagues from Reading University argue that the rate of change in the frontal cortex volume along the evolutionary branch leading up to humans was “unremarkable” and, in fact, outpaced by other branches.

Furthermore, the scientists found that while the frontal lobe did increase in size, it did so in tight correspondence to size increases in other areas of the brain and the brain’s overall size, as well as decreases in frontal neuron densities.

"This means that areas traditionally considered to be more primitive were just as important during our evolution,” Burton said in a press release.

Based on this new information, the study states, “The search for the neural basis of human cognitive uniqueness should therefore focus less on the front lobes in isolation and more on distributed neural networks.”

What’s more, the scientists believe their discovery suggests that areas of the brain that were previously thought to be more primitive, such as the cerebellum, may have an overlooked and important role in human cognition and its disorders, including autism and dyslexia.

Furthermore, Barton and his colleagues argue that many of the high-level abilities that take place in the human brain are carried out by more extensive brain networks involving different areas of the brain and that it’s the structure of these extended networks versus the size of any specific area that is most critical for cognitive functioning.

Ultimately, according to Barton, the “human frontal lobes are exactly the size expected for a non-human brain scaled up to human size.”

The study was funded by The Leverhulme Trust.