GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2006-07 > 1153576490
From: "Diana" <>
Subject: RE: [DNA] Advice/comments:Differences in Average Mutation Rates
Date: Sat, 22 Jul 2006 09:54:50 -0400
The problem is that you (speaking here of the larger, group "you") are trying to
apply a "mutation rate" as if it were a mathematical constant of nature, like
the rate of acceleration of a falling object in a gravitational field. It's
not. Let me put the next sentence in all caps to emphasize it: MUTATIONS ARE
RANDOM EVENTS, AND RANDOM IS THE *OPPOSITE* OF EVEN.
What people are calling a mutation "rate" is actually a descriptive statistic of
past random events based on various existing data sets. The fact that different
data sets produce different averages should clue us in to the fact that what is
being calculated is not a natural constant, but a description of history. You
cannot take an average mutation "rate" describing one of these large data sets
and turn around and apply it to a small data set, not with any useful
predictability. The issue here is not the accuracy of the calculated average,
that is, not whether it's a valid description of the larger sample, but whether
that average can then be applied to individual cases (i.e., to individual
families in genealogical time). I submit that it cannot be.
The example I like to use to help explain what this means is that of life
expectancy. Based on data from 2004, average life expectancy in the United
States is 77.9 years. How much confidence do you have that you, or anyone else
you know, will die at that exact age? None? Have you ever known anyone who
died at that age? No? Then why would you expect an average mutation rate to be
applicable to a single family over a few generations?
In my opinion, for genealogists, the best use of STR testing is to support or
refute paper genealogies using logical deductions, not mathematical
calculations. And that means testing lots and LOTS of ever-more-distant cousins
to see where the "nodes" occur (between which fathers and sons in each line the
mutations appear), so you can create your own family's hierarchical "tree" of
> -----Original Message-----
> From: [mailto:]
> Sent: Saturday, July 22, 2006 6:22 AM
> Subject: Re: [DNA] Advice/comments:Differences in Average Mutation Rates
> What GIVES: with the incompatabile projectiins.
> Projections which are based on the differences in "average
> mutatiion rate"
> And, when some coherent frame-rerence- msg is develpd; perhaps the
> answer, the msg about the What gives questions
> can be promulgated to the community-at-large.