All the bad news and stories of bad, even horrific, human behavior can overwhelm us, leading to a very pessimistic outlook on humanity. It overshadows the examples of people doing the right thing, acting generously, with kindness and empathy.

Social scientist and physician Nicholas Christakis says its actually our tendency toward goodness that has been a big driver in our evolution. Christakis runs the Human Nature Lab at Yale and was once a hospice physician, work that has informed his research.

He says our need for human connection is one of our most defining characteristics and he’s seen it expressed at the bedside of people at the end of life, holding onto loved ones in their final moments. Christakis joins us to talk about our social evolution, why friendship and love are vital to our species’ survival, and how he maintains his optimism for humankind.