AP Photo

Monkeys are closely related to us and their brains have long served as an indispensable model for understanding how our own brain works. But we're separated from each other by millions of years of evolution, so there are some major differences between their brains and ours. On the one hand, we can't assume that the results from experiments on their brains can be generalized to humans. But on the other, a better understanding of our differences can provide important clues about the evolutionary forces that shaped the human brain.