This week, we're learning about the past and the future of the human race on the planet we've come to dominate. Rachelle Saunders talks to Chip Walter, founder of AllThingsHuman.net, about his book "Last Ape Standing:The Seven-Million-Year Story of How and Why We Survived." And she speaks to University of Cincinnati paleoecologist Brooke Crowley about the evidence that human activity is the primary driver of change in our ecosystem.