Re: FW: Dawkins & Convergent Evolution- the final word (?)

From: Philip Jonkers (
Date: Wed Aug 29 2001 - 19:45:03 BST

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    Subject: Re: FW: Dawkins & Convergent Evolution- the final word (?)
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    I guess all the sensible things on this convergence issue
    have already aptly been said by Vincent and Joe, but I can't resist to add
    one little comment.

    > > <Dawkins discusses this dilemma in The Blind Watchmaker: "It is
    > > vanishingly improbable that the same evolutionary pathway should
    > > ever be followed twice.
    > > And it would seem similarly improbable, for the same statistical
    > > reasons, that two lines of evolution should converge on the same
    > > endpoint from different starting points. It is all the more
    > > striking... that numerous examples can be found in real nature,
    > > in which independent lines of eovlution appear to have converged,
    > > from very different starting points, on
    > > what looks very like the same end-point.

    As it stands it is somewhat confusing as the passage casts a little doubt on
    natural selection, I have to agree this much with Ted.
    He raises confusion in the second part (It is all the ...).
    Nonetheless, no unsurmountable problems for the theory of natural selection

    I agree, the probability of two species parellely traversing
    (i.e. both going through the same genetic changes) the same path of
    evolution is statistically non-existent. But the emergence of two
    species that superficially resemble one-another is quite finite.
    Compare, for instance, carcharadontosaurus with tyrannosaurus-rex.
    The odds of the showing-up of two similar species is very small, nonetheless.
    However, given the fact that the earth has known and still knows many
    species, the expectation value, i.e. number of species-pairs * prob. of
    similarity at any given time, might be quite large. Therefore, from
    a brute-force statistical point of view, emergence of two similar species
    (albeit from entirely different genera) is not a sheer impossibility
    but a fair possibility. Nature has obeyed this statistical rule at
    least to fair degree by presenting a sufficient number of cases.

    Philip Jonkers.



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