An analysis of brain scans from more than 600 children and adolescents reveals correlations between size of brain regions unique to humans and intelligence test scores. This finding, published in JNeurosci, was largely due to genetic factors, suggesting evolutionary expansion of the human brain — and the cognitive abilities it supports — is under strong genetic control.
Cerebral surface area has expanded dramatically over the course of human evolution. Brain regions that have undergone evolutionary expansion tend to follow a similar pattern during individual development. Despite these trends, brain structure can vary greatly between similar people. The relative contribution of genetic and environmental factors to brain surface area differences in children has been unclear.
Eric Schmitt and colleagues found more than 85 percent of differences in total cerebral surface area in their sample, which included identical and fraternal twins, could be attributed to genetic factors. The researchers also report a modest relationship between surface area of the brain’s language centers and scores on standard intelligence tests. Together these results provide new insight into the evolution and development of the human brain.