> “No population is, or ever could be, pure,” Why this obsession with 'purity'? Isn't it obvious that, despite none being pure, some populations are more closely related?
It is obvious, and the same data shows that groups can be very pure indeed. From this very article:
> Genetics also show that India’s caste system, previously thought to have developed under colonial rule, was in place thousands of years earlier.
First, "previously thought to have developed under colonial rule" is just false. The ancient Greeks wrote about India's caste system, thousands of years ago.
Second, what the data shows is not a record of social structure. It shows that modern Indian castes have practiced endogamy -- mating within the group, with negligible inflow from other groups -- for thousands of years.
Most people would be happy to describe this state of affairs as "pure" ancestry.