Archiver > GENEALOGY-DNA > 2006-03 > 1142202663

From: (John Chandler)
Subject: Re: [DNA] Re: Ages of S28+ (and S21+)
Date: Sun, 12 Mar 2006 17:31:03 -0500 (EST)
References: <001201c6454c$b8bbbc20$bec79045@Ken1> <001f01c645d7$329441e0$d7588456@d6e4z6>
In-Reply-To: <001f01c645d7$329441e0$d7588456@d6e4z6> (

Alan wrote:
> In this scenario, if DYS390 has reduced from anything like 100% being
> DYS390=24 (within the founding subgroup) to its current 69.7%, then the
> DYS390 modal has decomposed ( 30.3% in 20,000 yrs) at about 1.52% per 1,000
> years in the Atlantic region.

One thing you're leaving out is the non-linear nature of the decay
process. For example, if we take the generation length to be 30
years, then there are 667 generations in 20,000 years. Over that
time, the frequency of DYS390=24 is falling progressively, so that the
decay rate itself is declining, and, not only that, but the amounts of
DYS390=23 and DYS390=25 are increasing, and these both lead to a
rising rate of replenishment. The long and short of it is that the
implied mutation rate in falling to 69.7% in 667 generations is 0.0005
per generation, which comes to 2% decay in the last 1,000 years (33
generations). Not 1.52%. The larger the total decay, the more important
the effect of this non-linearity.

John Chandler

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