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Archiver > GENEALOGY-DNA > 2002-01 > 1010082642


From:
Subject: Re: [DNA] What happened 50,000 years?
Date: Thu, 3 Jan 2002 13:30:42 EST


In a message dated 01/03/02 1:31:32 AM Pacific Standard Time,
writes:


> Also how can anyone pinpoint our common male ancestor to 59,000 years - just
> take a look at the results produced by Ann's calculator. The Simms Boone
> discussion showed - with two mismatches - MRCA[95%] at 14.1 to 165.5
> generations. Presumably Adam has been dated by analysing Humanity's fan,
> which would produce an even greater range from this calculation. Someone's
> pulling a fast one here !
>

Just a word of caution -- the MRCA calculator is for a sample of two
individuals. The paper which was probably the source of the 59,000 number is
Thomson, "Recent common ancestry of human Y chromosomes: Evidence from DNA
sequence data." They use a different computational method, with a larger
sample size, a larger number of markers with a lower mutation rate (Unique
Event Polymorphisms), and a model of population expansion to arrive at their
number.

Nonetheless, your basic point about a range of values is well taken. The 95%
confidence interval in Thomson's paper is 40,000 to 100,000 years. This is
the basic take-home lesson for everyone, even those who don't want to plow
through all this statistical stuff: if someone spouts a single number for the
MRCA, it's just a rough guideline.

The Thomson paper is available online:

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&;
list_uids=10861004&dopt=Abstract


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