The real puzzle of the Basques for me is the blood group Rh- question. The exceptionally high incidence of this blood type among the Basques is one of the factors that convinced scholars in the days before modern population genetics that they were genetically different from neighbouring populations. Here a post on Gene Expression tackles the issue:
[url="http://www.gnxp.com/MT2/archives/002759.html%22]Are Basques Different[/url].
Razib cites Henry Harpending on the possibility of selection for Rh- among the Basques
I've always wondered about that; most people seem to assume the Rh- trait originated with the Basques, simply because worldwide, it is found most concentrated in ~their modern population. But they're a very ancient culture, perhaps the oldest one still living in Europe, & probably indigenous to the region that they continue to inhabit.
So, lately I'm more inclined to believe that the reason for it, is due to the reaction of the Basques to invasion from Indo-Europeans, by subsequently & stringently isolating themselves from 'foreigners'.
It very likely could have been ~introduced into their ancient population, by the marauding & intrusive Aryan tribes of the Near East. The Rh- trait being recessive / Mendelian, would tend to become gradually more prevalent in a fairly closed, exclusive group such as theirs' has been, historically.
I now wonder whether the increasing prevalence of Rh- genes in their contemporary group, might someday begin to have some serious repercussions on their overall health & biological future, thereby affecting their beautifully unique ethnic status quo.
In other words, keeping to themselves ethnically, probably seemed vital for their survival at some point in time. But I believe it was a response to attack by outside forces, & not their original natural behavior. In turn, the very mechanism which they employed to survive, may have had unforeseeable & serious drawbacks.
So instead of being some glamorous trait, it could be rather a terrible curse. Before embracing & owning it, maybe the Basques & others ought to see it for what it really is: a recessive trait, with associated problems attached (reduced fecundity being one of the most obvious ones).
I would point to the modern Cherokee as a prime example of how the Rh- factor may be introduced into a distinct tribal population, becoming more problematic over time.