> An important caveat. All these estimates are based on coalescent theory,
> which is a very successful area within population genetics. CT basically
> deals with phylogenies of different alleles in the same species, and uses
> those phylogenies to estimate things such as most recent common
> ancestors,
> effective population sizes and measures of gene flow. One of the most
> common assumptions is that the genes must be selectively neutral or at
> least nearly neutral. Any strongly beneficial mutation in the y
> chromosome
> could increase the frequency of that allele as well as other linked genes
> ("a selective sweep"). As a consequence, the estimated time for the most
> recent common ancestor would be biased towards the present, which
> could be
> the case here.
I absolutely agree with this, and that is one of the reasons that Adam and
Eve simply HAD to be earlier than what Christian apologists claim. Any
selection that we don't know about definitely moves the coalescence time
toward the present. But, apologists don't understand that and even those who
want to accept the mtDNA Eve theory claim that humans were created 150,000
years ago (or less) yet nuclear genes show coalescence times 5-10 times
longer than mtDNA.
>
> On the other hand, calculations by Francisco Ayala using the same
> coalescent theory suggested that the human effective population size
> (number of reproductively active individuals in a population)
> never became
> smaller than 50 individuals since the divergence from chimps. This is
> inconsistent with the idea of a very strong populational bottleneck with
> only one active female.
No one ever believed that there was only one active female--even the
advocates of mtDNA Eve. She just happened to be the only one who left her
mtDNA to us. There was an entire population of women when mtDNA Eve was on
earth--she wasn't the first. She was a descendant of the real Eve. One can
see this effect in family names on Pitcairn Island. They started with 6
family names. Today, due to men not leaving male offspring, they are down to
3 surnames in only 200 years. The y-chromosome structure on Pitcairn Island
would reflect this. They didn't start with 3 males, though the evidence
could not be used to prove the existence of the other 3.
glenn
see http://www.flash.net/~mortongr/dmd.htm
for lots of creation/evolution information
>
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