Courtney Humphries in Harvard Magazine:
Compare humans to other mammals and a distinguishing feature stands out: our large, cavernous craniums, and the densely folded brains stuffed into them. The human brain is more than triple the size of the brain of chimpanzees, our closest relatives. In particular, it’s the cerebral cortex—the wrinkled outer layer of the brain—that sets us apart. Whales and elephants also have big brains, but they can’t match our cortex in the sheer number of neurons and billions of connections among them. It’s obvious that our big brains are responsible in some way for enabling the unique things that humans do: developing languages, music, and art; using sophisticated tools and technologies; forming complex societies. But what is it about a bigger brain that makes these feats possible?
Randy Buckner, professor of psychology and of neuroscience, and his former student Fenna Krienen, Ph.D. ’13, have proposed a hypothesis to explain how the evolution of a large cortex may have enabled the distinct cognitive skills that humans display. The key is not just size but organization. As the human brain swelled, they argue, the cells in newly evolved areas were increasingly freed from constraints that patterned the simpler connections in other areas, and thus able to connect to each other in more complex ways that enabled new kinds of thinking.