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Archiver > GENEALOGY-DNA > 2007-03 > 1172853837


From: John Cartmell <>
Subject: Re: [DNA] Lactose tolerance evolved recently
Date: Fri, 02 Mar 2007 16:43:57 +0000 (GMT)
References: <4ebd5751d8john@cartmell.demon.co.uk><001501c75ce7$7831d140$6401a8c0@Precision360>
In-Reply-To: <001501c75ce7$7831d140$6401a8c0@Precision360>


On 02 Mar, Lawrence Mayka <> wrote:
> > [mailto:] On Behalf Of John Cartmell If
> > the genome was in the receiving population in low numbers (and hence not
> > picked up by the tests) then introduction of a dairy culture could
> > heavily select for the rare gene.

> The research shows that northern Europe drinks milk via a single allele
> whose age of existence since original mutation is between 2000 and 20,000
> years old. (I don't know why the confidence interval on the age of the
> northern European allele is so much larger than that of the others.) So
> yes, it is theoretically possible that the allele existed at low frequency
> throughout northern Europe for some period prior to the domestication of
> cattle. However, we have no specific reason or evidence to believe
> that--i.e., it is not the most parsimonious explanation.

I'm afraid I don't follow your reasoning. There is a small advantage to late
lactose tolerance at any time - certainly sufficient to cause no surprise if
such a gene is found at low levels in any population. That is supported by
late lactose tolerance arising in different places in different forms. That
such a genetic advantage would be strongly selected for on the introduction of
milk from domesticated animals is not a surprise either.

It *is* the most parsimonious explanation.

--
John

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