From the genealogy-dna list @ rootsweb.

Theola

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Yes, lactase persistence was certainly heavily favored by natural selection.
Within 7000 years, a single allele from a single origin somehow swept across
northern Europe in steamroller fashion, and spread in lesser percentages
across most of western Eurasia.

The point here is that the British Isles were not genetically 'inaccessible'
if lactase persistence swept through them so quickly.

> [mailto:[log in to unmask]] On Behalf Of
> Maybe being beneficial, natural selection-wise, the lactose
> gene on chromosome 2 had a leg up over non-selective R1b
> haplotypes, where drift would occur only very slowly?