One of the great science and health revelations of our time is the danger posed by meat-eating. Every day, it seems, we are warned about the harm producing and consuming meat can do to the environment and our bodies. Many of us have tried to limit how much meat we consume, and many of us have tried to give it up altogether. But it is not easy to resist the smoky, cured, barbequed, and fried delights that tempt us. What makes us crave animal protein, and what makes it so hard to give up? And if consuming meat is truly unhealthy for human beings, why didn't evolution turn us all into...