How Did Altruism Evolve?

We often talk about evolution in terms of competition, 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, Stephanie Preston, a professor of psychology and head of the Ecological Neuroscience Lab at the University of Michigan, talks about the evolutionary, neurological and behavioral foundations for altruism with our new co-host, the astrophysicist and author Janna Levin.