In humanity's more than 100,000 year history, we have evolved from vulnerable creatures clawing sustenance from Earth to a sophisticated global society manipulating every inch of it. In short, we have become the dominant animal. Why, then, are we creating a world that threatens our own species? What can we do to change the current trajectory toward more climate change, increased famine, and epidemic disease?

Renowned Stanford scientists Paul R. Ehrlich and Anne H. Ehrlich believe that intelligently addressing those questions depends on a clear understanding of how we evolved and how and...