Look across species and see how the brain evolved. Phylogenetic comparisons suggest that higher brain structures are more recent products of evolution.
Relative Measures of brain evolution : total brain weight
are elephants really smarter than humans?
gives a lineage more consistent with what we know about brain and intelligence (puts mammals over non mammals and humans at top) but within mammals puts porpoise over blue whale and baboon over gorilla.
favors mammals and puts humans at the top
index of cerebral enfolding
puts dolphins over humans. the overall size of human cortex is limited- by the skull and birth limits. (big head baby= C section - which in the wild means death.) Cerebral cortex has gotten bigger and more elaborate over time.
Otogeny Recapitulates Phylogeny
developmental gradient of the brain moves from lower to - with hindbrain developing first then midbrain, and forebrain (cortex) last.