Re: [tied] Re: Finding agriculture's 'genetic signature'

From: Jens Elmegaard Rasmussen
Message: 14281
Date: 2002-08-09

Dear Richard and List,

Why is that unlikely? To me, it is what I would have expected. The men
were quite probably those who moved in cases of real invasion, so genetic
traces originating from males ought to stand out more clearly that traces
watered down by the interference of local females.


On Fri, 9 Aug 2002, richardwordingham wrote:

> --- In cybalist@..., "matt6219" <matt62@...> wrote:
> >
> >
> The paper is 'Y genetic data support the Neolithic demic diffusion
> model', Lounès Chikhi, Richard A. Nichols , Guido Barbujani , and
> Mark A. Beaumont ( - Proceedings of the National
> Academy of Sciences of the USA, August 2002).  Accessible to
> *subscribers* after searching on the first author's surname.  One-off
> subscriptions are possible.
> Has anyone looked at it critically?  The abstract says, 'We analyze a
> large dataset of 22 binary markers from the non-recombining region of
> the Y chromosome (NRY), by using a genealogical likelihood-based
> approach. The results reveal a significantly larger genetic
> contribution from Neolithic farmers than did previous indirect
> approaches based on the distribution of haplotypes selected by using
> post hoc criteria.'  This immediately makes me wonder how sound their
> hypotheses are.  There is evidence, acknowledged in some papers, that
> the intense selectional pressure on the Y-chromosome can bias
> statistical dating techniques.  Also, mutation rates appear to be a
> lot more variable in the non-recombinant part of the Y-chromosome
> than in mitochondrial DNA, where there are known hot sites (with
> rates dependent on certain bases) that have had to be disregarded in
> some analyses.
> > Contributions ranged from 15-30% in France and Germany, to 85-100%
> > in southeastern European countries such as Albania, Macedonia, and
> > Greece.
> This is strikingly different to (Richards 2000,
> ) where
> Table 5 shows a relatively _low_ Neolithic contribution (11% ±5%)
> to
> the Eastern Mediterranean part of Europe, but also records a _high_
> (20%) proportion of recent arrivals there, which he attributes
> to  'the heavy historical gene flow between Greece and other
> populations of the Eastern Mediterranean'.  While greater female
> mobility may blur out some gradients in proportions, I don't see how
> it converts an area with a relatively high Neolithic proportion (as
> evidenced by stay-at-home men) to one with a relatively low Neolithic
> proportion (as evidenced by mobile women).
> Regards,
> Richard.
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