From: Jens Elmegaard Rasmussen
On Fri, 9 Aug 2002, richardwordingham wrote:
> --- In cybalist@..., "matt6219" <matt62@...> wrote:
> > http://news.bbc.co.uk/1/hi/sci/tech/2174437.stm
> The paper is 'Y genetic data support the Neolithic demic diffusion
> model', Lounès Chikhi, Richard A. Nichols , Guido Barbujani , and
> Mark A. Beaumont (http://www.pnas.org - 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,
> http://www.stats.ox.ac.uk/~macaulay/papers/richards_2000.pdf ) where
> Table 5 shows a relatively _low_ Neolithic contribution (11% ±5%)
> 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).
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