It's hard to completely generalize, because modernity is a pretty short timeframe and things are moving very quickly relative to the rest of history, but Pinker

It's hard to completely generalize, because modernity is a pretty short timeframe and things are moving very quickly relative to the rest of history, but Pinker's premise (which is well defended) is that human progress is inexorably toward less violence, both in terms of warfare and criminal/interpersonal violence. That's in large part because violence is becoming a less effective means of social advancement. Having effective, more or less trustworthy police and courts goes a long way toward both making violent behavior risky, and reducing the need for vigilante justice/vengeance violence. And civil courts help resolve disputes without resorting to violence. Likewise, trade and economic stability have become so effective that it makes little sense for nations to engage in war with their neighbors anymore. War is bad for business!