In short, and I can’t emphasize this strongly enough, a fundamental issue that any theory of psychology ultimately has to face is that brains are useful. They guide behavior. Any brain that didn’t cause its owner to do useful—in the evolutionary sense—things, didn’t cause reproduction.
-Robert Kurzban, Why Everyone (Else) is a Hypocrite: Evolution and the Modular Mind
-Robert Kurzban, Why Everyone (Else) is a Hypocrite: Evolution and the Modular Mind