Steven Pinker: A brief history of violence
If people had behaved in the 20th Century as they did in the Bible, several billion people would have died in war, not several hundred million. There are more people alive today, meaning that the raw numbers of deaths are higher, but people are fundamentally far less violent and in percentage terms violence has continually decreased since the enlightenment.
Steven Pinker is a Canadian psychologist with a talent, rather like Richard Dawkins, for thinking logically and writing clearly, while still remaining poetic. His books about language and the brain are popular science classics.
Here he talks at the famous TED conference, on the subject of violence, demolishing both the conservative fallacy of a morally superior past, and the liberal delusion about benign pre-scientific cultures.