HUMAN EVOLUTION EXPANDED BRAINS TO INCREASE EXPERTISE CAPACITY, NOT IQ Target Article on Brain-Expertise

Why do modern humans have larger brains than earlier people such as Homo erectus? As large brains cause problems in childbirth, infancy and locomotion, the advantage they offer must be substantial. This advantage might be associated with increased IQ, but there is a problem: evidence from MRI volumetric surveys, microcephaly and hemispherectomy shows that there exist individuals with psychometrically normal IQ but Homo-erectus-sized brains. Why did evolution increase brain size (with its associated costs) when humans (as these individuals demonstrate) can have normal IQ without bigger brains? I propose that the advantage may be related to increased capacity for an aspect of intelligent behaviour not measured by IQ tests but critical to the survival of our simple hunter-gatherers ancestors: the capacity to develop expertise.