Earlier quoted context omitted.
Ethnicities and tribes and inclusion therein are ambiguous, and it changes over time. Look at any society and its history. They're not homogeneous. All the historical countries and tribes were multiethnic. One example is Rome. Every region or province, even Italia, consisted of different ethnic groups. At one point there was a diverse group in a small area called the Latins. The Romans were a single ethnic group in L…
What's that got to do with anything? What's stopping me from identifying variation in the frequency of different traits between ethnic groups in the current day ? It's not a virtue to pretend not to notice such things (or, indeed, to be truly incapable of the most basic pattern recognition). I think the argument could then be made that if you identify traits common to closely related tribes (eg. indigenous East Afric…
As an example, slavery in the US created an artificial category or label of black people out of many unrelated peoples, calling them inferior by nature and using that to justify unethical systems.