 This kind of work is important, in part because of the uses to which well-confirmed cultural phylogenies can be put. It may be easiest to illustrate their value via a simple example. On the face of things, looking for correlations is a reasonable (albeit fallible) way to discover causal relationships. If, for example, people who smoke often get lung cancer, and people with lung cancer are often smokers, then we have good evidence that smoking causes lung cancer (or perhaps that lung cancer causes smoking). But there can be strong correlations that do not indicate causation. If, for example, we find that there is a strong correlation in animals between making a moo sound and producing large quantities of milk, we should not conclude that one causes the other. Mooing and milk production go together because the creatures in question share ancestors in common, who both mooed and gave lots of milk. Of course, in the case of cows this fact of common ancestry is so obvious that we hardly notice how it informs our causal inference. But cultural phylogenies are unobvious. Russell Gray, among others, has long argued that when we understand them better, our knowledge of phylogenies can then confirm, or undermine, causal hypotheses that are claimed on the basis of correlation. 