Doesn’t have to be large groups to be different groups. That seems like a fallacious argument.
Empirically/anecdotally I bet quite a few people could with 90%+ accuracy pick a (third-generation) Iberian vs Frank vs Polack vs Scandi out of a lineup just by physical features
Alternatively take a reasonably deep look at American (North or South) indigenous tribal societies- the empirical history is thinner there but similar conclusions
Someone posted a photo of eight Italian soccer players all wearing the same uniform and said “there is no meaningful difference between northern and southern Italians, try to tell them apart.”
I guessed, and got 7 of 8 correct. (The one I missed was Sardinian)
Empirically/anecdotally I bet quite a few people could with 90%+ accuracy pick a (third-generation) Iberian vs Frank vs Polack vs Scandi out of a lineup just by physical features
Alternatively take a reasonably deep look at American (North or South) indigenous tribal societies- the empirical history is thinner there but similar conclusions