What I think is fascinating (and I'm glad Trammell mentions this in her comment) is that fact that even with such a broad definition as Heng offers, race as a category of difference not only encompasses religion and ethnicity, but also what we think of as more typical markers of race now: things like skin color or physical difference. The examples you pull are excellent on this because, for me, one of the most critical elements of Heng's work is the way it allows us as modern people to understand a much longer and more complex genealogy of racial thought. The iconography you point to from King David and John the Baptist has a clear link to racist narratives about skin color now. By seeing how old these narratives are, and by seeing the contexts in which they used to operate, I think we can get better understanding of how racist narratives operate and come into being.