Further proof race is a social construct:

I wanted a picture of a running woman for a lesson.  I was sure most students would know the verb "to run" and confident at least a few of them would be able to say "she likes running" if prompted.  I chose this one:

Looks like she's flying.  Thanks, Google Images.

Most of my students were able to say "she likes running" as predicted.  However, when I asked "Where do you think she's from?" things got a bit weird.  I asked this question re this random woman in 10 classes last week and in every one someone immediately called out "Kenya!"

Perhaps you're thinking the worldwide fame of Kenyan distance runners has penetrated Korean pop culture to such an extent that here running itself is associated with Kenya and Kenyans.  I assure you this is not the case.  My students think this woman is from Kenya because Kenya is the only African country they can name.  I know this because my follow-up question in each class was "Why Kenya?" and the answer was always "black" or "black skin" or the ungrammatical slap in the face "she is black people."

You may consider this misidentification of a tanned woman as a black African a product of ignorance, and that's fair.  These students have probably never seen a "black" person in real life, much less met one.  The only non-Asians they know are the English teachers they've had the last 3 years:  probably 2 or 3 waygooks total, and they met me only last week.

But I don't want to dwell on the ignorance here, not when there's a far more instructive observation to be made:  the difference between a "white" person with a tan and a "black" person is not immediately clear to Korean children because it isn't obvious.