Is there any scientific evidence that the differences in violence across societies aren’t caused by religious differences? Yes, lots of it! First, there are hundreds of studies which show that poor countries are – on average – many times more violent and undemocratic than rich ones. And then there is one very comprehensive and rigorous study by Inglehart and Welzel which shows that there is only a very small – almost insignificant – cultural influence if you control for other factors – especially economic ones – and that economic change leads to cultural change (many times more than the other way round). I highly recommend their book on the topic from which I have learned more about the world we live in than from any other one.