Home > Anti-evolution, Evolution, Intelligent Design > Ctenophores and early branching

Ctenophores and early branching

April 13, 2008

A few days back I took on Denyse O’Leary’s "science journalism by press release" modus operandi. Now, T. Ryan Gregory has taken on the same press release while dispelling the "early branching equals primitive" fallacy that underlies O’Leary’s claims. Wander on over and have a read.

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  1. Colugo
    April 13, 2008 at 5:02 pm | #1

    Gregory makes relevant points, but the issue is about convergence as well as complexity. One explanation for the findings is that comb jellies have independently evolved an extraordinary number of features that converge on other relatively advanced metazoans, especially jellyfish. (“Advanced” compared to placozoans and sponges.) And in which case Eumetazoa is paraphyletic. In contrast, the LCA of vertebrates and echinoderms must had a lot of traits characteristic of both groups. In fact, they have diverged rather than converged, with echinoderms evolving radial symmetry.
    (Then again, possible viable morphological pathways from a primitive metazoan foundation may be quite limited, mandating a host of evolutionary convergences between comb jellies and jellyfish.)
    A more likely scenario, I think, is that sponges are a “degenerate” (I know, we’re not supposed to use these terms) group, perhaps one that became unicellular and re-evolved multicellularity.
    Perhaps the simplest explanation is that the study’s conclusion is erroneous. Who knows. More information will resolve the matter.

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