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From:
Subject: Re: Most recent common ancestors
Date: 16 Jan 2006 06:01:11 -0800
References: <1137338990.456458.231910@f14g2000cwb.googlegroups.com> <mo4ms15t5bs77ev0ds8bhs690882gdmb15@4ax.com> <dqf5c5$rl4$1@newsg1.svr.pol.co.uk> <dqff7p$afe$1@eeyore.INS.cwru.edu>
In-Reply-To: <dqff7p$afe$1@eeyore.INS.cwru.edu>


Todd A. Farmerie wrote:
> Rob wrote:
>
> > A reason for not accepting the theory that as been presented is Cheddar man
> > discovered in 1903. DNA was extracted from the skeleton and this was
> > compared with a class of boys in or around Cheddar. The teacher also had
> > DNA taken. Upon examination there was ( apparently) enough markers to
> > suggest that the teacher was a descendent of this early man who if memory
> > serves me right dated to the Mesolithic period or some 9000 years ago.
>
> They do not show that he was a descendant, they show that he belonged to
> the same maternal lineage.
>
> Anyhow this misses the point. As has already been pointed out,
> virtually all North American 'natives' probably also descend from
> post-Columbus Euros, even if only through a single
> great-great-great-great-great-great-(etc)-grandfather. The fact that
> they are members of tribes that predate Columbus does not negate this.
> In other words, there is nothing to stop the schoolteacher in question
> from being descended from BOTH the Cheddar man AND Ghengis Khan.

Absolutely.

> That being said, I also find the model flawed, but because it ignores
> inbreeding and isolated populations. Inbreeding was extensive, not so
> much on the level of first-cousin marriage, although that did happen,
> but in terms of most rural villages, where after a couple of hundred
> years with minimal migration they were all descended from the same
> people and no marriage within the community expanded the genetic
> heritage in the slightest. It also means that once a fresh lineage is
> introduced, it too becomes saturating within a couple hundred years.
> The key, then, is isolation, and there are populations so isolated that
> it is unlikely they have acquired European ancestry, and certainly all
> of Europe has not acquired descent from them. In short, such
> statistical approaches require dramatic over-simplification to produce
> results, but these same simplifications that make the analysis possible
> likewise doom the results to represent nothing more than a statistical
> exercise.

Are there really such isolated populations? With nobody ever coming in
from the next island, the next patch of forest, the next valley? Where?

The most literally insular communities of all, in the Pacific Islands,
were settled from elsewhere only in the last thousand years, never mind
the considerable intermixture with Europeans in the last 200. And I'm
not sure if you meant to also include pre-industrial Europe, where
there seems to me to have been quite a lot of movement due to trade,
slavery, war, etc.

Nicholas

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