What's human about the human brain?
Understanding how human brain organization differs from that of other species is essential for understanding the neural bases of human cognitive and behavioral specializations. Nevertheless, neuroscientists have largely ignored this subject. A review of the small body of available evidence indicates that the human brain became enormously enlarged following the divergence of humans from African apes, with association cortex expanding disproportionately. There is, however, no evidence that humans evolved new cortical areas; indeed, a reasonable case can be made that classical language areas have homologs in nonhuman primates. Humans possess morphological characteristics (sylvian-fissure asymmetries) and features of cortical histology that monkeys lack, although apes are more similar to humans in these respects. We can improve our understanding of human brain specializations by directly comparing humans, apes, and other nonhuman primates using the wide array of available morphological and histological techniques that do not require invasive or terminal procedures
