[zuminator]

All of that is true, but it has little to do with why race exists as a persistent meme. We don't segregate ourselves by blood type, height, or BMI, even though they have certain genetic and medical correlates.

The purpose of race is social differentiation, not medical. That's why identifying himself as mongrel got the author in trouble. He was punking the social order. That's what needed to be upheld, not their data codes. Doubtful they would've grilled him for hours for writing an EBCDIC-incompatible circumflexed vowel in his surname.

That's also why identifying oneself as mixed-race can be problematic. People don't know where to place you in the pecking order, and if you're on their team. It's not like people are concerned for your health, "B-b-but if you put the wrong race you might get a contraindicated blood pressure medication in 30 years!!!"