• Although it's not brain size alone that accounts for human intelligence, it certainly plays a pretty important role -- and now, researchers at Duke University have identified the DNA sequence that may be responsible for that particular evolutionary deviation.
  • The DNA sequence, called HARE5, is a gene activity regulator shown to markedly increase the size of a mouse embryo's brain when injected into the embryo. Compared to a mouse embryo injected with chimpanzee HARE5, the mouse embryo's brain grew 12 percent larger.
  • Mice with human HARE5 showed faster proliferation of neuron progenitor cells than mice with chimp HARE5 -- resulting in more neurons, and affecting the neocortex -- the region of the brain involved in higher functions, such as language and reasoning. Towards the end of gestation, the size difference in the brains was visible to the naked eye.

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