> The exceptions could be only in well isolated populations. Indo-
European
> groups (at least in Europe) definitely were not isolated. Thus I
guess that
> modern ethnic groups inhabiting Europe are more genetically diverse
than
> their ancestors some thousand years ago.
>
I read somewhere that some Native American tribes were highly
specialized (that would be genetically, you need enzymes (=proteins)
to digest) with respect to the food they ate, eg. including a
particular species of maize. And once they go off that food and start
on European food they go pop and get overweight, as many of them are
today. The only similar European example I can think of is the
inverse correlation between the length of time since agriculture was
introduced and the incidence of gluten intolerance in the population.
But one might also imagine a similar correlation between the time
since metal working was intriduced and susceptibility to heavy metal
poisoning. It's not been checked, to mu knowledge.
Also, it occured to me once, a type of resistance built in one group
of people might work enzyme-wise, thus genetically, in different
ways, if the groups were separate at the time they were exposed to
this new environmental factor. Which means that once they cross-
breed, even if both groups are resistant to a certain type
of 'potential poison', their offspring might not be (since not all
the genes required for the set of enzymes might have been
transmitted).
Torsten