This book is the perfect bridge between Dawkins highly influential "The Selfish Gene" and Ridley's own "The Rational Optimist". It starts by questioning the paradox of our selfish gene and altruistic social behaviour, and ends it with the importance of exchange and trust; the source and basis for virtue. The importance of exchange in our development and future is of course what he discussed even more in The Rational Optimist. It has a lot of interesting theories, stories, and ideas. But feels a bit lacking in cohesiveness at times. If you want to know more about our social evolution, this book is recommended.