I just finished reading "The Better Angels of Our Nature: Why Violence Has Declined" by Steven Pinker, a book which ranks as among the most important I have ever read.
The strength of the book is in demonstrating the basic premise: that violence is in decline. In graph after graph, Pinker lays out the evidence for a world that has been becoming ever more pacifist. The trends go back centuries, but are most striking in the past 60 years - war fatalities, executions, homicides, violent assault, rape - all have been consistently falling. Pinker makes an iron-clad case that the past is not to be glorified; far from being a golden age, it was a savage "morally retarded" time. We only need to start going back a few decades to return to racial segregation and lynching, legal prosecution of sexuality, a subordinate status for women and routine physical abuse of children. The numbers don't lie, this is a better safer time than has ever existed. Each generation is becoming less violent and more liberal on personal rights and freedoms.
Pinker's attempt to explain why this decline is occurring is less rigorous and more "hand waving", and his ideas of changes in population genetics would not stand up to any mathematical modelling. But it is still an incredibly important book just for attempting to explain one of the most radical changes in human behaviour that has ever occurred.
Hayden had some slightly lighter reading while I concentrated on Pinker