Well I know that information about genetic diversity was used to generate the phylogenetic tree since the same sequences are used to determine both, therefore there is data leakage. So I am sure it is circular, it is only a matter of how circular. I think totally circular.<p>Perhaps I am misunderstanding their model, but look at figure S2. It shows the less closely related the sequences at each location, the more likely that was the originating region relative to the others. See how the leafs of the right tree corresponding to location B are more widely distributed (indicating diversity) than those for location A or C (which are more clustered within the tree)?