[The evolution of the brain in the genus Homo: the neurobiology that makes us different]

For the most part, what makes us different from other animal species is comprised within our brain. However, there is no single factor, no singular reason accounting for the difference between our brain and others; rather, differences appear multiple.

Here we perform an up-to-date review of the main divergences between ours and other species' brains, which might be explaining the singularities of our behavior. When brain volume is on focus, it can be appreciated that our brain is certainly large both in relative and absolute terms, being also the case that some subdivisions of the prefrontal regions, as much as the parietal or temporal lobes appear notably increased in size relative to other brain areas. Also at variance with other species, our brain is consistently more asymmetric. But differences also involve the cellular level. In this regard, they have been reported different and peculiar proportions of neurons both within and between cortical columns, as much as certain types of neurons (like fusiform and mirror neurons) that, even if they are not exclusively human, they display in our species peculiar quantitative and functional features. Finally, neuronal receptor systems seem to exhibit exclusively human traits that might be crucial to understanding some of the singularities of the evolution of our brain.