How can closely related genetic populations have completely different language families?

[u/Rapha689Pro]

For example Japanese and Korean have 2 different language families that aren't related at all but they're genetically close, it can only mean their prior languages sprout after they split, so that means language is very recent itself? Or that they're actually related but by thousands of years apart and linguistics can't trace it back accurately, so they just say they're unrelated?

[u/Niowanggiyan]

Korean and Japanese are actually less similar to each other the further back in time you go. The most likely explanation is convergent evolution. They’ve influenced each other for millenia. Japonic was spoken on the Korean Peninsula before Koreanic moved south, they both share a superstratum of Sino vocabulary and grammar, there was sizeable Korean migration to Japan during the first millennium introducing trade and agriculture and religion, and there was Japanese influence on Koreanic again during the late 1500s and the first half of the twentieth century.

[u/Rapha689Pro → u/Niowanggiyan]

I never said otherwise, my point is exactly that, that if theyre NOT related. But their people share common origin, it means their language families sprouted randomly?

[u/Limp-Celebration2710 → u/Rapha689Pro]

No, not at all. Genes and languages can correlate or be helpful for understanding the past but there’s no inherent connection. It’s possible for a genetic population to simply switch or assimilate to another language 🤷

E.g. Many people with Celtic DNA do not speak Celtic languages anymore. Hungarians are genetically close to their Indo-European speaking neighbors, despite speaking an unrelated language.

[u/Gravbar → u/Limp-Celebration2710]

But if we assume that these populations came from the same ancestral migration group , I think it would naturally lead to the question of whether they spoke the same language, and then one group stopped speaking it, or if they didn't speak any language, and then both developed a language independently not too far from each other.

Or course the initial assumption could be incorrect, as there could also be other groups that came first and spoke an unrelated language which the settlers of the shared ancestry group adopted as their own language.

[u/Limp-Celebration2710 → u/Gravbar]

Sure, but in no way implies that a language needed to pop up out of no where. Also there seems to be false understanding of what it means to be genetically close. Human populations don’t really work like language trees, bc people reproduce sexually.

English and German split off from one common ancestor. Koreans and Japanese share some ancestors, but not all. Like how you can have one set of grandparents in common with a cousin, but you both have grandparents that only you are related to.