The received knowledge is that human cognitive abilities are due to humans having a larger frontal cortex than other animals. This ‘fact’ is now in doubt. Even if Sherlock Holmes had a noble forehead, we can’t assume the the frontal lobes are the key to intelligence. This idea may even be hindering clearer understanding of the brain.
ScienceDaily reports (here) on research by Barton Venditti. “Human frontal lobes are not relatively large”, inPNAS, May 2013.
Here is the abstract:
“One of the most pervasive assumptions about human brain evolution is that it involved relative enlargement of the frontal lobes. We show that this assumption is without foundation. Analysis of five independent data sets using correctly scaled measures and phylogenetic methods reveals that the size of human frontal lobes, and of specific frontal regions, is as expected relative to the size of other brain structures. Recent claims for relative enlargement of human frontal white matter volume, and for relative enlargement shared by all great apes, seem to be mistaken. Furthermore, using a recently developed method for detecting shifts in evolutionary rates, we find that the rate of change in relative frontal cortex volume along the phylogenetic branch leading to humans was unremarkable and that other branches showed significantly faster rates of change. Although absolute and proportional frontal region size increased rapidly in humans, this change was tightly correlated with corresponding size increases in other areas and whole brain size, and with decreases in frontal neuron densities. The search for the neural basis of human cognitive uniqueness should therefore focus less on the frontal lobes in isolation and more on distributed neural networks.”