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February 15, 2013
Q. Go ahead now. Put your big brain to work trying to answer this intriguing question: How did we become such a big-brained species?
A. We humans boast about 1,400 cubic centimeters of brain volume, or roughly three times that of the chimpanzee, our closest evolutionary cousin, says Michael Balter in Science magazine. While the brains of whales and elephants surpass ours in absolute measure, proportionally (based on body weight) ours are bigger. So why did “natural selection bestow such generous largesse on the human noggin”? One fascinating theory, by psychologist Robin Dunbar of the University of Oxford (and others), argues that brain size correlates with the size of a species' social group, with our large neocortex needed to help keep track of who is doing what to whom. Adds biological anthropologist Robert Seyfarth, this social brain hypothesis has generated a huge amount of research, with one study even showing “a positive correlation between gray matter density and the number of Facebook friends an individual has.”
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