It would be nice to think that as humanity grew up a bit and democracy spread, the number of wars would decrease.
Not so, according to research from the University of Warwick and Humboldt University, which shows that we're actually having more and more.
Between 1870 and 2001, the number of wars between national states rose by an average of two percent a year. Back in 1870, there were just six; by the 1990s, around 36 per year.
And the reasons? Too many new countries and cheaper weaponry, says professor Mark Harrison from the University of Warwick.
"More pairs of countries have clashed because there have been more pairs. This is not reassuring: it shows that there is a close connection between wars and the creation of states and new borders," he says.
And the other reason, he says, is increasing global prosperity, with economic growth making destructive power cheaper.
In addition, the rise of democracy has actually increased the ability to wage war, because it allows states to tax and borrow more than ever before.
"In other words, the very things that should make politicians less likely to want war – productivity growth, democracy, and trading opportunities – have also made war cheaper," says Harrison.
"We have more wars, not because we want them, but because we can."