GENEALOGY-DNA-L Archives
Archiver > GENEALOGY-DNA > 2002-08 > 1030724903
From:
Subject: Re: [DNA] How Specific is 12 marker test
Date: Fri, 30 Aug 2002 12:28:23 EDT
In a message dated 08/29/02 8:23:16 AM Pacific Daylight Time,
writes:
> If two or more individuals in a study match on all 12 markers and they share
> a surname and all live in the Southern States of the USA, what is considered
> their probability of sharing a common ancestor in the last 300+ years. The
> sequence shared is said to be a 90% probability of being Amerindian. So how
> far back in generations does this point to a MRCA? Thanks.
I guess you're asking about the cumulative probability. There's a graph at
Walsh's web site which is based purely on behavior of random events.
http://nitro.biosci.arizona.edu/ftdna/12-0-0.html
The other factors you mentioned -- sharing a surname, living in the same
region, and (probably) rarity of the haplotype -- are all factors which we
intuitively feel would increase the probability that they share a common
ancestor. They are independent lines of evidence and reinforce each other.
However, we have no way of quantifying those factors.
Ann Turner
GENEALOGY-DNA List Administrator
http://lists.rootsweb.com/index/other/Miscellaneous/GENEALOGY-DNA.html
DNA preservation kits: http://www.dnafiler.com
This thread: