GENEALOGY-DNA-L Archives

Archiver > GENEALOGY-DNA > 2010-06 > 1277731330


From: "Lee K. Ramsey" <>
Subject: Re: [DNA] Genetic Distance and Probability
Date: Mon, 28 Jun 2010 09:22:24 -0400
References: <000301cb165f$8b7b9f30$a272dd90$@net> <4C280E02.4070906@san.rr.com>
In-Reply-To: <4C280E02.4070906@san.rr.com>


Thanks Al, Diana and T.K.

Having a comprehensive family history, I am able to eliminate a common
ancestor with the 67 marker match (Keith Ramsey) within the last 8
generations. This information was used to recalculate the probability for
the 9 to 24 generation percentages. Thus, I used the 24 generation
percentage as the 'most likely' genealogical time frame for a common
ancestor. The below link for the FTDNA comparison chart seems to fall in
line with what I am able to determine from my paper trail (I have no
response from the matched person, whose paper trail may be less than mind).
Although mutations are random I used the 24 generation (600 years)
probability recalculation as the 'most likely' time frame for a common
ancestor. In my case, this represents more of an exercise in developing a
research stradegy for the surname rather than an exercise in probability and
statistics. It does leave much to ponder. I appreciate everyone's knowledge
and expertise.

http://www.familytreedna.com/my-ftdna/tip-report.aspx?res=67&tokitnum=8FQ6ps
A15u0%3d&fromkitnum=Cey4u0I5WME%3d&gd=3


-----Original Message-----
From:
[mailto:] On Behalf Of Al Aburto
Sent: Sunday, June 27, 2010 10:51 PM
To:
Subject: Re: [DNA] Genetic Distance and Probability

I think FTDNA gives one a range of probabilities to choose from which
yield lesser number of generations ...

The 99.9% probability means: FTDNA is in this case estimating your
common ancestor lived at some unknown time between now and 600 years ago
with 99.9% probability, and that there is a 0.1% probability your common
ancestor lived at greater than 600 years. It is a very _safe_ estimated
range of time (600 years).
Al

> On 6/27/2010 6:16 PM, Lee K. Ramsey wrote:
> The closet surname match I have with FTDNA is the 67 marker test with a
> genetic distance of three, showing a 99.90% probability we share a Common
> Ancestor at 24 generations. (600 yrs = c.1410)
>
>
>
> Having no Common Ancestor within 8 generations the recalculation for the
> paper trail shows there is a 99.77% probability that we share a common
> ancestor at 24 generations.
>
>
>
> Although FTDNA's estimates are on the conservative side, the 24th
generation
> probability for the recalculation seems high for a genetic distance of
> three. What else should be considerate or read into these calculations?
> What other conclusions could be made? Is the early 1400s Common Ancestor
a
> reasonable estimation.
>
>
>
> Lee
>


-------------------------------
To unsubscribe from the list, please send an email to
with the word 'unsubscribe' without the
quotes in the subject and the body of the message

This thread: