Midpoint Rooting of a network of relationships

    Given an unrooted network of evolutionary distances among four species of caniform Carnivora, midpoint rooting places the root halfway between the two most divergent taxa. In this case, the maximum pairwise species difference is 110 + 57 + 183 = 350 between Ailuropoda & Procyon. The root is therefore placed at 350 / 2 = 175 on this connection, which falls on the Procyon branch, 8 units from the internode. The rooted network can be drawn with Procyon as the outgroup to the other three, with the known bear (Ursus) and suspected bear (Ailuropoda) as the most similar pair.

    The evolutionary implication is that, because Ailuropoda and Ursus are most similar ( (110 + 85) / 2 = 98 ) ), they are also most closely related, if the amount of evolutionary change is proportional to time since separation.