Fig. 16

The lineages leading to contemporary species have all been evolving for exactly the same amount of time. Rates of morphological change may vary among lineages, but the amount of time that separates two living lineages from their common ancestor does not. This figure shows the relationships among a sample of vertebrate lineages, all of which have been evolving for exactly the same amount of time, even if some lineages have undergone more change or more branching than others or if some taxonomically identifiable subsets of those lineage (e.g., teleost fishes) arose earlier than others (e.g., mammals). It is therefore a fallacy to describe one modern species as “more evolved” than another. Note, however, that this is a cladogram rather than an ultrametric tree, such that one cannot assume that any or all of G, H, E, F, C, and B are equal, only that the total amount of time between root and tip is the same along each of the lineages