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From: Gary Felix <>
Subject: Re: [DNA] revised TMRCA calcuations for the R-L21 results
Date: Wed, 3 Jun 2009 21:38:41 -0700 (PDT)


Never said they had to be identical or in the same generation. It may have taken thousands of years before the Y and Mtdna lines accumulated variance that survives until today. In relative terms this is "almost" pertaining to the ages of Adam and Eve (who would be older). Crawford said they expected similar ages because their effective population sizes were expected to be equal.

>It is because of the inherent randomness of some of the processes
(drift, bottlenecks, >sex-specific demographics, natural selection) that
you would not expect these two >individuals to have lived at the same
time.  That would be a phenomenally great >coincidence.

Specifically how would you explain this big a difference between TMRCA est. of 171-238Kya for the Mtdna line and the 46-109kya of TMRCA of Y? 

Gary
Mexico DNA Project Admin.

______________________________________________________
--- On Wed, 6/3/09, Thomas Gull <> wrote:

From: Thomas Gull <>
Subject: Re: [DNA] revised TMRCA calcuations for the R-L21 results
To: "genealogy dna" <>
Date: Wednesday, June 3, 2009, 5:58 AM


How would anyone explain that by total coincidence all living humans were provably descended from two specific individuals who lived at the same moment within the last 150,000 or so years?  The odds against that are astronomically large unless there would be some extremely specific process that makes the two chains of event work in lockstep.  There isn't.  I agree 100% with VV - why would anyone have ever expected the Y-DNA and mtDNA trails for living humans to lead back to one male and one female living in the same generation?  I'm sure it made headlines because of the Biblical Adam and Eve concept. But that's not what we're talking about here - not the "first humans" concept, but the "last winners in the genetic sweepstakes" concept. And there was one "sweepstakes" for males and one for females, with no scientific process that would make you expect them to end up in the same timeframe statistically.


It is because of the inherent randomness of some of the processes (drift, bottlenecks, sex-specific demographics, natural selection) that you would not expect these two individuals to have lived at the same time.  That would be a phenomenally great coincidence.


> Date: Tue, 2 Jun 2009 19:26:16 -0700
> From:
> To:
> Subject: Re: [DNA] revised TMRCA calcuations for the R-L21 results
>
> >> TMRCA for Y and Mtdna should theoretically go back almost to genetic 
> >> Adam and Eve respectively.
>
> >Sure, but the the TMRCA estimates need not be identical (or even 
> >similar) this there is no a priori reason to presume MRCA-Y and MRCA-
> >mtDNA were contemporaries of each other.  That is, there is nothing 
> >that dictates they lived in the same time or place.
>
> Not so. Crawford states this was unexpected and the news made headlines about 10 years ago. Google genetic adam and eve. He references Wilder et al 2004b when he states that it could be natural selection or sex specific demographic processes.
>
> >No.  The lower effective population size (assuming that Crawford is 
> >even right on this point) would cause the TMRCA to be lower in 
> >reality.  Lower TMRCA estimates are reflecting the reality, not a 
> >distortion of it.
>
> How would you explain differently, genetic adam being about half the age of genetic eve when Geneticists say it is drift or sex specific demographic processes?
>
> Gary
> Mexico DNA Project Admin.
>


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