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From: "Ken Nordtvedt" <>
Subject: Re: [DNA] Y-STR Mutation rate
Date: Tue, 3 Jan 2006 17:11:18 -0700
References: <43BA9D15.11854.CC059D@localhost>


Size as such and uniform growth rate size (even shrinkage) does not affect a
population's expected diversity or average squared differences. And
fundamental mutation rate in individuals is not connected to group size.
Small group statistical properties will be more easily affected (perturbed)
as a rule than will the statistical properties of large populations. And
extreme population shrinkage might lose some diversity, but less than one
might think unless the limit of a single surviving family is reached.

There are different mutation rates for different markers. If you separately
tabulate the average squared difference for each marker for a population you
find the ASDs are larger for the fast mutating markers and smaller for the
slow mutating markers. But there is lots of variance seen in the ASDs, as
math analysis finds there should be.

The text book statements usually are that most mutations are harmful, not
helpful. The picture is a very intricate machine; tinker with it; the odds
are greater you will hinder its performance rather than enhance its
performance. How do the good mutations prevail? Greater reproductive
success of some mutational modifications leads to their greater presence in
future generations. Natural selection while being a mathematical tautology
is nevertheless profound and deeply robust as a concept and mechanism.

Large regions of the dna material, especially in the Y chromosome, are
thought to be close to junk dna, not coding for anything important. If so,
their mutations should be neutral from a selection perspective.

Ken
----- Original Message -----
From: "Drew Baumann Roberts" <>
To: <>
Sent: Tuesday, January 03, 2006 4:49 PM
Subject: Re: [DNA] Y-STR Mutation rate


> Ken, Ann, et al--
>
> Does it follow then that small groups increase mutation rate?
>
> And, when we speak of "Mutation Rate", aren't we talking about a Set of
> Variables?
>
> Obviously a dominant leader of a group, or any sexually active and
> successful male,
> is going to have more offspring and therefore a greater impact on a small
> group than
> a large group, assuming his offspring prosper and pass on his genes and
> encounter
> no greater mortality from disease or warfare than the others in his group.
>
> Do we know or think most mutations are beneficial or at least, benighn,
> and not
> harmful from a purely medical or physical standpoint?
>
> Then, when populations expand due to favorable weather, or available food,
> or some
> other aspect of their environment or culture (Harems, Polygamy, Religion,
> etc.) and
> small groups increasingly interact and exchange genes at a higher rate
> than
> previously with different haplotypes, does this decrease the effective
> mutation rate in
> that combinig, larger population?
>
> Just some things I have been wondering about.
>
> Drew
>
> On 3 Jan 2006 at 13:07, Ken Nordtvedt wrote:
>
>> So any mechanism which creates reproductive success variations within
>> a population reduces effective mutation rate.
>>
>> Ken
>>
>>
>>
>> > However, I've suggested that "social" selection might play a role,
>> > like the Genghis Khan effect where the descendants of one man come
>> > to dominate the haplotype diversity measures. The Zhivotovksy study
>> > was based on measuring variability in the Roma (gypsies) and some
>> > Pacific Islanders. I can easily imagine a dominant chieftain effect
>> > in those populations. However again, list members who worked on
>> > simulations didn't seem to think that could account for the
>> > discrepancy, either.
>> >
>> > Ann Turner
>
>
>
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