> populations that have had continuous populations
This misses the point because this isn't about continuity of population in terms of lineage, just perpetual inhabitation. A city such as Sicily over time has exchanged hands and transformed culture many, many times. Cities are cosmopolitan. Demographics change, and culture is not static. It was not for nomadic tribes either. What we can find for them, however, are relics tied to a certain point in time, to a certain place, describing a certain nomadic culture. They are certainly not the same as those persisting today, whether there is some lineage or otherwise.
It also reads funny; what makes them continuous, you mean they did not partake in interracial mingling? We don't know how continuous they really were. We only know that nomadic lifestyle existed a long time, and ultimately is the precursor of settlements; humanity was of course once entirely nomadic, therefore we all have nomadic ancestors. Fukuyama would suggest that centralized agriculture was developed to increase population in order to wage war, which eventually grew enough to necessitate bureaucracy.
> mere mention of nomads would create such a passionate backlash!
I don't see any. Maybe it's something you're feeling?