NEUROSCIENCE
Brain Study Casts Doubt on Theory of How Human Intelligence Evolved
Of all the characteristics that distinguish humans from other primates, those related to intelligence hold special interest for scholars and laypeople alike. It's an appropriate enough fascination. After all, what could be more uniquely human than the desire to understand how our big, curious, narcissistic brains evolved? That said, a lot of the story is entirely unknown, and the results of a new study suggest that some of what scientists thought they knew may actually require revision.
According to a popular view of human cognitive capabilities, much of what sets our species apart from the other primates can be attributed to a disproportionate enlargement of a part of the brain known as the frontal cortex that occurred at some point in human evolution. But the evidence traditionally used to support that argument, say Katerina Semendeferi of the University of California at San Diego and her colleagues, comes from small studies that in many cases did not include data from apes, our closest relatives. Furthermore, the studies varied in the way they defined the region of the cortex.
The team's own findings, detailed in the current issue of the journal Nature Neuroscience, led to a rather different conclusion. Using magnetic resonance imaging, the researchers obtained brain scans of 15 living great apes, four lesser apes, five monkeys and 10 humans—a sample larger than any used in the prev