This is the first example I've found where cliques are actually good for something: minimizing contagion. Finally, a sound evolutionary reason for behavior that, while gratifying to popular people, is horrible for society as a whole.
... may not be as closely linked as thought. I'm glad someone actually did some research on this topic, instead of just assuming it. In my observation, humans often act like an opportunistic infection. They may not cause extinction outright, although they certainly can, but they are very prone to helping along the process for species already stressed by something else such as climate change.