Imagine a world that is a really nasty place to live, more or less populated with players that always defect, except there's a little cluster of tit-for-tat players that live in some kind of nucleus and they get to play with each other a lot because they're geographically sequestered. They will start building up a lot of points, and also because that translates into offspring, they'll start to take over the population. So in fact, Axelrod showed that a little island of cooperation can emerge and spread and eventually will take over the world, which is fantastic.