If this fascinates you I recommend you read https://en.wikipedia.org/wiki/The_Better_Angels_of_Our_Natur... . It's a book that talks about violence in history. Ötzi is mentioned and so are a few others.
Steven Pinker's assertions in TBAOON are nice and intellectually attractive but ultimately, difficult to prove or disprove. Naseem Taleb had quite a strong reaction to it. " "Pinker doesn’t have a clear idea of the difference between science and journalism, or the one between rigorous empiricism and anecdotal statements. Science is not about making claims about a sample, but using a sample to make general claims and…
I highly doubt the increasing friction between the USA and China (and the rest of the world to be honest) is leading to any sort of third world war so I'm confident that a tendency to violence does in fact decrease in certain societies.