A detailed investigation of the expansion in human brains over 7 million years finds faster growth in modern humans and our nearest relatives than our predecessors. Nevertheless, brains have grown as species evolved, rather than suddenly jumping when one branch of humanity replaced another. Brain size and intelligence do not correlate perfectly, but the findings are the best guide … for how our intellectual capacities [reached] their current state.
One finding … is that Neanderthal brains grew throughout their history, contradicting the idea they were unable to adapt. In fact, Homo neanderthalensis shows the fastest increase in brain size of any species in the study, including Homo sapiens.
Evidence of continuous growth within a species adds to the developing conclusion that species boundaries are not as sharp as we once imagined.
