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From: "Ken Nordtvedt" <>
Subject: Re: [DNA] revised TMRCA calcuations for the R-L21 results
Date: Sat, 30 May 2009 08:51:10 -0600
References: <5FF64B53E8C84111A12F5129E3704405@PC>


----- Original Message -----
From: "Lancaster-Boon" <>


> It is a common misunderstanding that Y diversity in a population should
> work
> like mixing colours. It strikes me that this might be a good metaphor for
> showing what is wrong with that idea.
>
> Two colours can mix, and become a new colour. Y chromosomes do not mix.
> They
> have to stay Yellow or Red. So any mixing of Red Y and Yellow Y in a
> population does not lead to Orange, it leads to a dynamic situation in
> which
> either Red or Yellow will eventually start to dominate for reasons which
> have little to do with initial numbers.
>
> Best Regards
> Andrew

Example: A population of an initial 1000 men experiences as a whole a rate
of zero population growth over hundreds of generations. The extinction rate
of male lines over that period is about 99 percent due to the random
flucuations of male offspring number. The average surviving line (about ten
of them) will be represented by 100 descendants at the end, i.e. those
surviving lines experienced on average a 100-fold demographic expansion ---
some even greater, some less.

Ken



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