A while back, Glenn claimed that the age of Mitochondrial Eve (approx 300,000
years) contradicted Hugh Ross's creation time frame. I have researched this
claim and fount it to be based on circular reasoning.
As a further check on the data, Ruvolo calculated the diversity
between humans and chimps, and she came up with a figure 27 times
the diversity within humans. She then used estimates of the time
when the two species diverged (6 million to 10 million years ago)
and derived a coalescence time for the human population of between
222,000 and 370,000 years. (Ann Gibbons, Science, vol 259, 26
February 1993, p. 1249)
So Eve's age was calculated based on the assumption that chimps and humans
had a common female ancestor 6-10 million years ago.
Similarly, the ages calculated for Adam depend on assuming a male human/
chimp common ancestor.
This value [for the divergence rate] was determined by using 14 My
as the branching date for the orangutan lineage and 5 My as the age
of the human/chimp-gorilla split, as proposed by M. Hasegawa, H.
Kishino, and T.A. Yano (Journal of Human Evolution, 18, 461, 1989)
The rate was derived by averaging over all pairwise comparisons.
(Dorit et al, Science, vol 268, 26 May 1995, Note 11 p. 1185)
Glenn further suggested that Hugh Ross was being dishonest when he said,
"This non-variation suggests no evolution has occurred in male ancestry."
but I read this as Ross explaining the significance of non-variation to his
lay audience.
Glenn went on to quote M.F. Hammer:
These results are not inconsistent with a recent sequencing survey
of the third intron of the Zfy gene that revealed complete
monomorphism. When the HKA test is applied (in comparison with both
mtDNA and Beta-globin), the null hypothesis is not rejected. However,
the unusually low level of divergence between human and chimpanzee Zfy
introns (a nearly threefold lower D value compared with the YAP locus)
makes this region uninformative for inferring human population history.
(Hammer, Nature, vol 378, 23 November 1995, p. 377)
and suggest that Hugh Ross should retract his "Chromosome Study Stuns
Evolutionist" article.
But Dorit et al write:
There are three general classes of explanation for the lack of
variation of a chromosomal region: purifying selection, chance
absence of segregating sites or recent common ancestry.
(Dorit et al., Science, vol 268, 26 May 1995, p. 1183)
Both Hammer and Dorit et al. reject the possibility of selection:
Selection at this intron cannot account for the absence of variation,
as interspecific comparisons of the sequences of this intron in other
primates show that variable sites are distributed throughout the
intron and include at least 21 unambiguous transitions, 14 unambiguous
transversions, and 4 insertions or deletions. Furthermore, these data
suggest that the absence of recombination in this region of the Y
chromosome does not detectably slow rates of interspecific divergence;
indeed, Y-linked sequences have been shown to exhibit accelerated
rates of evolution. (Dorit et al. p. 1183)
Therefore, the data provide no evidence for a recent fixation of a
favorable mutation anywhere on the non-recombining portion of the Y
chromosome (or the mtDNA molecule). (Hammer p. 377)
So if Dorit et al. are correct and the three types of explanation for non-
variation are 1) selection, 2) statistical aberration and 3) recent common
ancestry, then why does Hammer say that the Zfy intron cannot be used to infer
anything about human population history? His suggestion that a small
divergence between humans and chimps is enough to discard this evidence is
questionable because it amounts to the suggestion that selection has maintained
the monomorphism of the intron. Both Dorit et al and Hammer show that there is
no evidence of this occuring. In fact, Dorit explicitly says that selection
cannot be the reason for the lack of variation because interspecific divergence
of the intron between FOUR primate species shows significant variation.
In Christ,
robert van de water
associate researcher
UCLA