Everybody, apparently, needs good neighbours, but in many parts of the world, your neighbours can be your worst enemy. In the past century, more than 100 million people have lost their lives to violent conflicts. Most of these were fought between groups of people living physically side by side, but separated by culture or ethnicity.

Now, May Lim and colleagues from the New England Complex Systems Institute have developed a mathematical model that can predict where such conflicts by looking at how different groups are spread out in a given area.

According to their research, violence is most likely to erupt in areas with poorly-defined boundaries between large and culturally different groups. Their model predicted