Welsh Y chromosomes.

The current _National Geographic_ (June 2001) has an article on Wales.
In it, the noted geneticist Steve Jones is quoted on a certain Y
chromosome:

--start quote--
There is a Y chromosome that is quite rare in England and Europe but
common in Wales ... above all in West Wales. ... The link of the Welsh
Y chromosome is not with those who see themselves as real Celts but
with the Basques of northern Spain.
--end quote--

From the point of view of languages, it would be very foolish to deny
that Vasconic was considerably more widespread than now, or even, in
Roman days, and may have extended northward even into the British
Isles and beyond.

Nonetheless, so far as I know, there has never ever been any
suggestion whatsoever than there is some sort of Basque substratum in
Welsh -- or anywhere in GB or Ireland. No comment can be made on what
language this group of current Welsh-speakers may have originally
spoken before Celtic some several thousands of years ago, or what
language was spoken in Britain before the advent of Celtic.

Nonetheless, the genetic evidence is interesting. This certainly
demonstrates that an early vector of the spread of humanity into
Western Europe was along the Atlantic, up from Spain. And it adds
force to the usual wisdom that IE spread from the east, replacing
everything (except Basque) in its wake, leaving no evident substratum
except for that in Germanic.

How, when and why IE replaced all these other languages is an
interesting question, one that has not been satisfactorily answered.