This famous bet — between a biologist and an economist — was over population growth. It started three decades ago, but it helped set the tone for environmental debates that are still happening today.
The biologist at the heart of this bet was Paul Ehrlich at Stanford. He wrote a best-selling book in 1968 called The Population Bomb. It was so popular he appeared on The Tonight Show with Johnny Carson.
He told Carson, "There are 3.6 billion people in the world today, and we are adding about 70 million a year. And that's too many.