Comments/Questions re Phylum level evolution

Date: Thu Aug 24 2000 - 05:14:58 EDT

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    Thank you for your review of the changes that took place in the
    Pre-cambrian/Cambrian biota.

    You provided evidence that 1) precursors to the Cambrian animals have been
    found, and 2) some evidence that the Cambrian explosion was not sudden or

    You overinterpret the data when you say that the "appearance which is now
    known to be a very gradual appearance of more and more complex animal life
    forms extending from 700 million years ago to 500 million years." By this
    interpretation, the Cambrian explosion is a non-event.

    Others disagree. You haven't dealt with Bowring et. al.'s (Science, 261,
    Sept. 3, 1993) estimate that the Cambrian explosion lasted at most 10 million
    years and as little as 5 million.

    Gould called the event an "overt evolutionary burst to large size and greatly
    increased anatomical variety in the subsequent Cambrian explosion" (Natural
    History, 7/98-8/98).

    Moreover he said,: "The Cambrian explosion ranks as such a definitive
    episode in the history of animals..." and then goes on to acknowledge the
    need to understand antecedents and the unfolding of this cardinal geological

    These views hardly sound like a very gradual appearance of more and more
    complex animals, as you described it.

    The question I raise is that mechanism was involved.

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