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I'm going to try showing this better. Vertical distances represent time. Horizontal distances are a convenience for lettering and presentation.



   cats    ducks    garter snakes   frogs   smallmouth bass
    |        |            |           |           |
    |        |            |           |           |
    |        \            /           |           |
    |         ancient diapsids        |           |
    |                |                |           |
    ancient          |                |           |
    synapsids        /                |           |
     \              /                 |           |
      \            /                  |           |
       basal reptiles___              |           |
                        \             |           |
                         \___...______|           |
                                      |           |
                                   ancient        |
                                  amphibians      |
                                      |           |
                                      \           |
                                   some Devonian fish
                                           |
                                           |

The evolutionary model says that modern smallmouth bass should be as far from "some Devonian fish" as modern mammals and all other modern descendants of "some Devonian fish." Why? Because the last time everything was together was before amphibians diverged from fish. This is borne out, except we can only check the fairly modern stuff against each other. (No Devonian DNA survives.)

Do data from molecular clocks tend to match the expected pattern predicted by cladistics? To a stunning degree, yes. Convergence of Independent Phylogenies.

The evolutionary model says that modern smallmouth bass should be as far from "some Devonian fish" as modern mammals and all other modern descendants of "some Devonian fish." Why? Because the last time everything was together was before amphibians diverged from fish.

Perhaps a better answer would have been, "There has been just as much time and about as many generations in the line leading from the Devonian fish to the smallmouth bass as in any other line, so why wouldn't there be a corresponding number of neutral mutations?"