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Archiver > GENEALOGY-DNA > 2011-01 > 1293982888


From: "Ken Nordtvedt" <>
Subject: Re: [DNA] How old is Y-Chromosome Adam?
Date: Sun, 2 Jan 2011 08:41:28 -0700
References: <mailman.255.1293782436.1099.genealogy-dna@rootsweb.com><3203DE795D7E4D24B6A24928379E156E@anatoldesktop><AANLkTi=F+O4hFtK900wWetyKtfjzJB90r_CYi+5cc8h8@mail.gmail.com><3494E649-D554-4BFA-A206-80C054DBB9B6@vizachero.com><19954443.178870.1293883908917.JavaMail.www@wwinf2233><004001cba9d5$b0498ed0$c2482dae@Ken1><C4D1EA69-E1DC-4EB2-8F2C-E97B0E9971F3@vizachero.com><005a01cba9dc$a6a96650$c2482dae@Ken1><5E0F95F0B965408DB2815855E6B42C45@lop><AANLkTimVz4+h41_r+ZwEv+zhaWaOaVWO8Kf0xih-fV2t@mail.gmail.com><00f901cbaa01$d1a63110$c2482dae@Ken1><AANLkTimQxMy8g-wVgiqzp-4SiQ9RAVBs0PGq+BTjJbAx@mail.gmail.com><D41627AD-C565-4766-B899-2CE421596718@vizachero.com><AANLkTin92hWJUngGsmV8HqLXqC+0Gu_Uzkua0RCeWWLb@mail.gmail.com><DDD7CB70-75CD-48EF-AE59-FFAB4EF9DD5B@vizachero.com><AANLkTi=9ROdk1A2HtC3TtR2rr=nvX73bc0_TgTMm5-7D@mail.gmail.com>


----- Original Message -----
From: "Dienekes Pontikos" <>

but that it's not clear which markers provide better
estimates.

[[ Hopefully no one will try to make age estimates with single STRs ---
whether genealogical, ancient, let alone genetic Adam application.

sigmaG / G = [ (1+4mG) /2mG ]^1/2

Let's consider G = 2500 generations

For very fast STR with m = 1/100
sigmaG/G = 1.42

For the very slow STR with m = 1/10000
sigmaG/G = 1.41


All that matters in this domain is how many (N) STRs you will combine in an
estimate. Then you gain a further 1 / N^1/2 factor in sigmaG / G,
reflecting the fractional contraction of the distribution for the sum of STR
variances about its average (central limit theorem).

Then when you look at a few dozen STR individual G estimates taken from
distributions with sigmas like that you will surely get the wild set of
estimates you show from some data set.

The variance distributions for individual STRs are simply too broad for time
depths of 2500 generations to make individual STR estimates meaningful one
by one.

And this is pure statistics. Complications in the model from the simple,
single mutation rate for each STR, have not yet been brought into the
picture. It is this latter issue which should be worked out and quantified
in as non-anecdotal a way as possible. KN ]]


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