Genetic differences don’t mean it’s not made up. It’s not like we studied people’s genes and went “hm yes you can divide this ethnic group into four subgroups,

Genetic differences don’t mean it’s not made up. It’s not like we studied people’s genes and went “hm yes you can divide this ethnic group into four subgroups, Science!” People made a system where they divided themselves, and over time that division resulted in some small but noticeable amount of genetic divergence. But there are, like, trillions of different genetic differences between all of us, and you could draw totally different lines around people and find a genetic basis if you really wanted. The genetic basis is used to justify the arbitrary groups; the groups are not an emergent phenomenon of the genetics.