JK Rowling slammed for asking if she can be Black if she likes “Motown & fancy myself in cornrows”

Mate, no. I understand the practical existence of race (well... to the extent a nonracialized person can) what I'm talking about is the expert consensus that: the matter of where the boundaries between races get drawn is determined by social factors, not biological.

The question of whether an ethnicity was (and is) 'white' or not was a political question, not a biological one.