Problems for Y-chromosme Adam

From: Glenn Morton (glennmorton@entouch.net)
Date: Thu Jun 19 2003 - 17:18:09 EDT

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    Years ago, Hugh Ross made the claim that the genetic data for the
    Y-chromosome put Adam within the past 60,000 years. I criticised this at
    the time, because the research he cited couldn't be used in the way he did.
    The study had found little genetic variation in the human Y-chromosome.
    That is a fact. Hugh had written:

    "A British team composed of geneticists Simon Whitfield, John Sulston, and
    Peter Goodfellow examined a much larger segment of the human Y chromosome, a
    segment composed of 100,000 nucleotide base pairs, in 5 ethnically distinct
    men. The divergence they observed was so small as to shrink that date
    projection to somewhere between 37,000 and 49,000 years ago. This newest
    date for man's progenitor has come within the range of biblically determined
    dates for Adam. If the Genesis genealogies are anywhere from 10 to 80
    percent complete, as most conservative scholars suggest, the Adam of Eden
    lived between 7,500 and 60,000 years ago.
            "What is more, the paper by Whitfield, Sulston, and
    Goodfellow explains how
    the integration of their Y-chromosome data with a variety of other data on
    such factors as bone morphology and geographic distribution, among others,
    shows that Homo sapiens could not have evolved by natural processes from
    Homo erectus." Hugh Ross, "Searching for Adam," Facts & Faith, Vol 10, No.
    1, p. 4

    Now comes some genetic information which shows that the Y-chromosome has a
    mechanism which tends to erase mutations meaning that all the estimates for
    the age of the Y-chromosome are out the window. The mechanism would make the
    Y-chromosome appear young when in fact it isn't.
    The region of the Y-chromsome which shows such limited variability is
    palindromic between the strands. Thus if a mutation occurs on one strand,
    the other strand can be used to correct the error. Gene conversion is the
    mechanism:

    "If gene conversion between palindrome arms was responsible for our
    findings, it might leave traces in the recent genealogy of the human MSY. In
    particular, we might find evidence that single nucleotide differences
    between the two arms of a human MSY palindrome had been eliminated by gene
    conversion. Examination of two CDY genesˇone in each arm of palindrome
    P1ˇrevealed a duplicated site of sequence variation that fulfilled this
    prediction. By sequencing this duplicated site in diverse, unrelated men, we
    identified some Y chromosomes with a C at this site in both arms of P1 (C/C
    chromosomes), other chromosomes with a C in one arm and a T in the second
    arm (C/T chromosomes), and other chromosomes with a T in both arms (T/T
    chromosomes; Fig. 2a). We confirmed these findings using a
    PCR/restriction-digestion assay (Supplementary Fig. 4). This single
    nucleotide substitution occurs at nucleotide 381 of the CDY coding region
    but does not alter the predicted amino acid sequence." Rozen, S. et al.
    Nature 423, 873-876 (2003)

    WHat is more, there is very little divergence between us and the chimps
    showing that this chromosome can't be used as Ross wants.

    "Near uniformity of arm-to-arm sequence divergence in both human and
    chimpanzee palindromes (Table 2 in ref. 1 and Fig. 1b) suggests a
    steady-state balance between new mutations that create differences between
    arms, and gene-conversion events that erase these differences." Rozen, S. et
    al. Nature 423, 873-876 (2003)

    And the age of these palindromic sequences pre-date the human-chimp split.

    "Using comparative sequencing in great apes, we demonstrate here that at
    least six of these MSY palindromes predate the divergence of the human and
    chimpanzee lineages, which occurred about 5 million years ago." Rozen, S. et
    al. Nature 423, 873-876 (2003).

    "These findings suggested that: (1) most palindromes found in the modern
    human MSY were already present, in the MSY, in the common ancestor of humans
    and chimpanzees; and (2) inner boundaries are more highly conserved than
    outer boundaries." Rozen, S. et al. Nature 423, 873-876 (2003)

    Once again, we find evidence for connection between us and the apes. A
    connection, I might add, which Christian apologists will ignore.



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