> People are not 'race x' or 'race y' biologically, as if race is some discrete set of features common to a whole population. Every individual has a set of biological features inherited from their ancestors which, theoretically, could include any or all so-called 'races'. Human beings have a continuum of features that is heavily interlaced amongst all the 'races'.

Exactly. One of the people I'll always point to as evidence that race is a social construct is Barack Obama. He was the "first black president". In reality he is, genetically, as "white" as he is "black". We still call him black because of the color of his skin.

If people insist for long enough that racial categories are inherently biological you'll eventually end up in one-drop judgement territory. Not a great place to have a discussion.