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Archiver > GENEALOGY-DNA > 2006-08 > 1154507676


From: "Diana" <>
Subject: RE: [DNA] research strategy for genealogists
Date: Wed, 2 Aug 2006 04:34:36 -0400
In-Reply-To: <562.37a4c92.32016c35@aol.com>


I said the hypothetical example I gave was unrealistic, just to illustrate that
having the same value at a marker doesn't prove you have the same ancestry.
It's a given that we all have common ancestors if we go back far enough, I was
speaking of how genealogists, working in genealogical time, can best use these
data.

My point, and apparently I didn't make it well, was that taking a cladistic
approach (creating a hierarchy by finding the nodes, i.e., creating a tree by
finding the branching points) was a more effective/valid/accurate/useful
approach than simply assessing relatedness based on "overall resemblance."
Everyone accepts analyzing SNP data cladistically, it simply strikes me as odd
that people aren't using a cladistic approach to analyzing STR data. It's such
an obvious methodology to use.

Diana

> -----Original Message-----
> From: [mailto:]
> Sent: Tuesday, August 01, 2006 9:47 PM
> To:
> Subject: Re: [DNA] research strategy for genealogists
>
> In a message dated 7/31/2006 2:30:52 PM Pacific Daylight
> Time,
> writes:
>
> > The difference between animal morphology and Y-chromosome
> STRs is that the
> > former is being driven by natural selection, while we are
> assuming the
> > latter is
> > selection neutral, meaning the resemblances are technically
> coincidence, not
> > convergence. So, how does "resemblance" caused by coincidence or
> > convergence
> > affect our Y-DNA STR research strategy? Is having two
> unrelated animals
> > look
> > alike similar to having similar STR motifs? The answer is,
> yes, in terms of
> > having to figure out how to separate real relationship from
> a superficial
> > resemblance.
>
> It is surprisingly difficult to achieve this state of
> coincidence/convergence. I know you meant it to dramatize
> your point, but your specific example would
> be well nigh impossible to achieve. I ran some simulations
> one time with
> easier starting points -- just one or two differences out of
> 37 markers. The
> results were summarized in this old message (long URL, ends in +F)
>
>
> http://listsearches.rootsweb.com/cgi-bin/ifetch2?/u1/textindic
es/G/GENEALOGY-DNA+2005+17283828476+F
>
> Convergence occurred in a very small percentage of cases, so
> it's not a good
> explanation for why different surnames have the same
> haplotype. Relatively
> speaking (pun!), it's far more likely that they have the same
> haplotype because
> they descend from a common ancestor who lived before the time
> surnames were
> adopted. It's harder to estimate the relative probability of
> another explanation,
> that different surnames have the same haplotype because of
> name changes and
> misattributed paternity in more recent times, where there's
> some chance of
> finding a paper trail.
>
> Ann Turner
>
>
> ==============================
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>
>
>
>

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