How Did Altruism Evolve?

We often talk about evolution as the survival of the fittest. But if it is, then where did the widespread (and widely admired) impulse to help others even at great cost to ourselves come from? In this episode, host Janna Levin speaks with Stephanie Preston, a professor of psychology and head of the Ecological Neuroscience Lab at the University of Michigan, about the evolutionary, neurological and behavioral foundations for altruism.