Archiver > GENEALOGY-DNA > 2005-06 > 1118176315

From: (John Chandler)
Subject: Re: [DNA] Middle Eastern ancestral markers on new Euro 1.0 test
Date: Tue, 7 Jun 2005 16:31:55 -0400 (EDT)
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Andrew wrote:
> That is simply wrong, and not just unsatisfying, because it is tautological.

Unfortunately, you've got that exactly backwards. A tautological
definition defines something to be itself and is therefore
automatically correct and even undeniable, though perhaps not as
useful as it could be.

> Using the adjectives "statisical" and "operational" do not stop this from
> being bad procedure. In a discussion about whether X causes Y, you are
> *defining* observations of Y as "operational" observations of X.

Before you go off in a tizzy, bear in mind that we weren't talking
about causes of either X or Y. I merely presented a working
definition of a commonly used evolutionary term based on what can be
observed, rather than on speculation. It bears repeating a third
time: the observation of a signficant difference in survival rate *is*
the operational definition of selective advantage, and, in fact, there
is no other way to define selective advantage.

> Not really clear. I think I understood...

There's the rub. You had a preconceived opinion and didn't pay proper
attention to anything that didn't "fit".

> Given the context, what is important is that famine etc *can* happen in the
> population as a whole. And it is obvious that this is true, no? In fact
> extremely localised famine sounds very odd indeed. So it is in fact you who
> assumes something odd: that famine can only happen in one village at a time
> for example.

You're still not paying attention. I invite you to go back and read
my last message again. This time, do not assume that I meant something
other than what I said.

> Then the question remains "how do you exclude bottlenecks?"

Very simply: by observation. The effect of a bottleneck is a drastic
reduction in genetic diversity along with a potentially dramatic shift
in the gene pool. If you don't find the loss of diversity, then you
can't postulate a bottleneck.

John Chandler

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