In a brief snippet from a conversation Robert had with Richard Dawkins at the 92 Street Y in New York City, we learn that natural selection is often a brutal arms race, inherently full of suffering and cruelty. But if Darwin's big idea is really predicated on pain and selfishness, why does selflessness exist?

Lynn Levy brings us the story of George Price, who bopped through the 60s like some kind of scientific Forrest Gump. He worked on the atom bomb, transitors, computer-aided-design, and eventually turned his attention to the problem of altruism. Lynn talks to Oren Harman, author of The Price of Altruism, and George's daughters Annamarie and Kathleen, who help us get to know this complicated genius.  In 1967, George left his family, went to London, and wrote a mathematical equation to explain why one creature might sacrifice its own interests for another. Carl Zimmer helps us understand why altruism is such a problem in the first place, and how family might hold the key to understanding apparently selfless acts. The so-called Price Equation changed biology ... and ultimately led Price to spend the rest of his life trying to transcend his own equation.