At some point during the last 100,000 years, humans began exhibiting traits and behavior that distinguished us from other animals, eventually creating language, art, religion, bicycles, spacecraft, and nuclear weapons-all within a heartbeat of evolutionary time. Now, faced with the threat of nuclear weapons and the effects of climate change, it seems our innate tendencies for violence and invention have led us to a crucial fork in our road. Where did these traits come from? Are they part of our species immutable destiny? Or is there hope for our species’ future if we change?