It’s an old Hollywood trope: the hero with heart always wins. In fact, science says that sense of duty to others is the whole reason the human race exists at all. Brian Hare, a professor of evolutionary anthropology, psychology and neuroscience at Duke University, joins host Krys Boyd to talk about how sharing and caring led early humans to evolve past their rivals. His article “Survival of the Friendliest,” co-written with Vanessa Woods, appears in Scientific American.