system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How is race a social construct?

I know this question sounds incredibly ignorant but i have been trying to understand for some time.  My main reason for asking is because if we have dna testing that can show someone’s ancestry is this much % Italian and this much % Korean, how is that a social construct if it’s in our dna?

Please understand I’m not saying race isn’t a social construct, I am just trying to understand how it is a social construct.
gpt
Focusing on the DNA tests, they don't measure the amount of "Korean-ness".  They measure the presence or absence of hundreds of different harmless mutations.  Some of these mutations are most commonly found in people from a particular region, so the more of them you have, the more of your ancestors probably came from that region.

But those mutations didn't necessarily *originate* in that country.  For example, the DNA test might associate "Korean-ness" with one gene that originally mutated in China and was brought to Korea through migration 2000 years ago, another that was brought by Mongol invaders 800 years ago, a third that originated in Korea but is also now found in Japan and Manchuria, and a fourth that originated in Japan and was brought over during their invasions in the 16th century.

None of these genetic tags are uniquely Korean, they're all found in other parts of northeast Asia.  All the genetic test can tell you is that that particular combination of genetic tags is most often found in the modern people who've chosen to call themselves "Korean".  But those people have ancestors from all over the map.

Nobody's a pureblood, everyone's a mongrel, and it's been like this for thousands and thousands of years.  "Race" is nothing more than a set of sharp-lined boundaries we humans have chosen to draw across the blurry mixture that is human variation.