GENEALOGY-DNA-L ArchivesArchiver > GENEALOGY-DNA > 2002-11 > 1037805294
Subject: Re: [DNA] MRCA calculations
Date: Wed, 20 Nov 2002 10:14:54 EST
In a message dated 11/19/02 6:13:18 PM Pacific Standard Time,
> But this clearly shows the random chance that individuals from two families
> which are close in DNA could easily mutate toward each other and result in
> descendants who have exactly the same DNA patterns but are not related at
This can happen. Population geneticists use the terms "Identical By State"
(IBS) versus "Identical By Descent" (IBD). That is why they prefer slowly
changing markers such as the SNPs used to define haplgroups. However, they
are concerned about much longer time frames (thousands of years) than
genealogists (hundreds of years).
This is not likely to be a practical problem for surname projects with a
well-defined common ancestor in the past few hundred years. Not only would a
mutation have to occur in that time frame, it would have to be the specific
one which would confuse matters. You are bound to face more ambiguities,
because you have a large project and multiple origins for the surname. It's
possible that network diagramming would illustrate some of the conditions you
find in your project, since it includes alternative pathways between one
state and another (that's why they call it a network instead of a tree).
GENEALOGY-DNA List Administrator
DNA preservation kits: >http://www.dnafiler.com