I agree with all you have said -but with a caveat!.
The problem is that there appears to be nothing limiting the size of the
population during the period mentioned -- the way that I see the growth
of the humanoid population. They had the entire world to spread over and
they did just that.
Except for major catastrophes in one area or another another, the growth
of the human population has been continuous (as best I see the
literature). Therefore, the problem is one of why a particular
chromosome would disappear without any EXTERNAL pressures!!?
My suspicion would be that other than population pressures caused the
disappearance of the MANY Y-chromosomes that existed besides the "ADAM"
of the texts. Selection by "natural selection", methinks.
IMHO
Walt
-
asa-owner@lists.calvin.edu wrote:
>
> >One cannot argue with the data, so it must have happened. Why it
> >happened, seems to require more that a simple example of how one
> >randomly selected line can die out. I can generate examples where
> >each line should increase without limit, unless some competition
> >exists with limited resources ---- then it is easy.<
>
> The limits to total population size provide the limiting resources.
> The basic assumption is that each starting individual has a certain
> probability of contributing genes to the next generation, which has a
> certain size. Even if there is no difference in evolutionary merit
> between two alleles in a population, random fluctuations in
> reproductive success will produce varying proportions of the alleles
> in the next generation. Such random walks in a finite population
> will eventually result in the disappearance of alleles. Thus, a
> small population loses alleles rapidly whereas large populations
> change slowly. Even negative alleles have some chance of becoming
> established. The relative benefit conveyed by the allele, the
> initial proportions of the alleles, the rate of mutation, and the
> population size (including any changes it is undergoing) are among
> the important factors.
>
> Graur and Li, Molecular Evolution, Sinauer Press have a good
> discussion if you can get ahold of a copy. It is expensive but might
> be in university libraries.
>
> The analogy of surnames is good in that it is fairly obvious that
> little selective pressure exists, yet changes clearly take place. A
> standard example comes from Johann Sebastien Bach. Despite his
> having about 20 kids, no one since the mid-1800's has inherited the
> Bach name from his descendants (nor his Y chromosome).
>
> Dr. David Campbell
> Old Seashells
> University of Alabama
> Biodiversity & Systematics
> Dept. Biological Sciences
> Box 870345
> Tuscaloosa, AL 35487 USA
> bivalve@mail.davidson.alumlink.com
>
> That is Uncle Joe, taken in the masonic regalia of a Grand Exalted
> Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at
> Droigate Spa
-- =================================== Walt Hicks <wallyshoes@mindspring.com>In any consistent theory, there must exist true but not provable statements. (Godel's Theorem)
You can only find the truth with logic If you have already found the truth without it. (G.K. Chesterton) ===================================
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