I know that this is probably late in comming, but I have some thoughts on
ethnicity.  It appears to me that the problem is not ethnicity in itself,
but rather can it be seen in the archaeological record.  Can one
definitively pick out the ethnic make up of the fragile remains of material
culture from a somewhat jumbled pile?  I would say probably not, at least
not with out a lot of good hard supporting evidence from outside of the
archaeological context.  This does not mean that there is no ethnicity in
material culture.  Many Northern Europeans in the Great Lakes area continued
"Traditional" forms of woodworking, art, dress and space use for several
generations.  The Penn Germans are another example, as are many Native
American groups throughout the country. Unfortunately many of these
distinctive "markers" do not show up in and archaeological context.  If a
tree falls in the forest and no-one is there to hear it, does it make a
sound (or something like that).
Stephen Cook