Humans have exceptional skills and abilities that largely depend on their brains. One of the major questions of modern neuroscience is to understand how the human brain evolved. In general, we share brain features and functions with other animals in proportion to how closely we are related to them. Thus, we are more similar to our closest living relatives, chimpanzees and bonobos, than to more distant relatives, such as rats and mice, or even more distant still, zebrafish. As we make inferences about the evolution of the human brain, or any other complex brain, such as elephant or whale brains, from studies of other animals, we benefit from an increasing understanding of phylogeny and thus our relationships to other animals.