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Archiver > GENEALOGY-DNA > 2001-11 > 1005851490


From: "Allan S. Gleason" <>
Subject: Re: [DNA] Generation length
Date: Thu, 15 Nov 2001 11:11:30 -0800
References: <bf.16ef4ca4.292525d1@aol.com>


I certainly like those numbers better! My small group averaged 31.x years with
the exception of a pair of sibs who had pretty old grandfathers! Two of them
were in their late 40's and one was in his mid-50's shifting them up to a 36 year
average! BYU/Relative Genetics uses 25 years in their calculations.

Am headed for Arizona tomorrow for the winter so will be off the list for a few
days - much to the relief of many of you. However, if I don't get creamed by a
sixteen wheeler, I'll be back with a different email address and a plethora of
new but still stupid comments.

Allan





wrote:

> DNA test reports give us a probability range on how many generations ago the
> Most Recent Common Ancestor (MRCA) lived. Many sources use a value of 20-25
> years per generation to calculate how many years ago that would be. This has
> always struck me as being far too short for historical times. The article
> cited below gives a detailed analysis of 100 French Canadian pedigrees with
> an average depth of 9 generations. They summarize their results as
>
> 29 years -- mtDNA (maternally inherited)
> 31 years -- X chromosomes
> 35 years -- Y chromosomes (paternally inherited)
> 32 years -- autosomes (non-sex chromosomes)
> 30 years -- all types combined
>
> This seems more congruent with my own genealogical records. I'm sure the
> numbers would be lower in prehistoric times, but I still have my doubts about
> the 20 year figure.
>
> Am J Hum Genet 2000 Feb;66(2):651-8
>
> New estimates of intergenerational time intervals for the calculation of age
> and origins of mutations.
>
> Tremblay M, Vezina H.
>
> The full text is available online. I'm giving the URL to PubMed instead of
> the journal publisher because PubMed a neat new feature with links to
> textbooks. When you click on that icon, certain terms in the abstract and
> subject headings are highlighted, and you can dive into the relevant section
> in a textbook. Once you're in the books section, you can also browse any
> book.
>
> http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&;
> list_uids=10677323&dopt=Abstract
>
> ==============================
> Visit Ancestry.com for a FREE 14-Day Trial and enjoy access to the #1
> Source for Family History Online. Go to:
> http://www.ancestry.com/rd/redir.asp?targetid=702&sourceid=1237

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