This book examines the evolutionary roots of punishment, tracing their presence across history and using them to suggest legal reforms. We evolved to cooperate - albeit grudgingly - with each other, especially along two lines: theft (not stealing the property or well-being of others) and trust (keeping our promises).
Punishment made stealing and breaching sufficiently expensive to permit enough cooperation for our intensely social species to survive and flourish. But punishment was also costly, because of both the risk of a violent response and the potential loss of a group member.
We therefore also evolved a deep reticence to punish, and an urge to forgive when the wrongdoer caused minimal harm or, even after causing great harm, gave reliable signals he or she could be trusted to return to the fold. These urges to blame, forgive, and punish formed an evolutionary template on which all our modern punishing institutions have been built.