The problem of ethnicity, genetics and diversity of Runeterra/

Good evening, fellow summoners (I know I know, there are no summoners anymore, but I like that form of greeting).

I'm young student of oriental studies and an amateur of anthropology, therefore I'm interested in how the ethnicities in Runeterra worked. There are two options:

1. Once upon a time, all the races and civilizations mixed together and formed a multi-cultural society for unknown reasons (I assume that magic could be the thing, that pushed them towards unity), and then something really, really bad happened, like, Rune Wars, so their local cultures were fused together to create Runeterra we know today.
2. Riot completely ignored it when it comes to genetics, like Lucian being a Demacian, or Karma/many caucasian characters being a part o Shurima.

I will only try to talk about first option. It is hard to see how the diversity of league's cast works with the genetics. What was a homeland of black people, what was the homeland of hindu, like Karma. It would seem that black people had to migrate from far south of the continent, yet there is nothing to call it canon. There is an option that Icathia was the homeland of black people, but we know nothing of how the pure blood icathians looked like. And even if that's the part they came from, then why can we see all those white people? Assuming, that they were mixing races for all those housands of years, they all should have darker skin tones, blonde hair would be extremely rare and all that stuff. Maybe most of black people were anihilated with the fall of Icathia and only emmigrants who moved to Shurima and today's Demacia were left. Then, there is that one woman, who makes this all senseless. Karma, as a hindu person has no place of origin in the map of Runeterra, there is no exotic and hot, yet suitable river place, where that race could potentially live. I mean, probably, we do not know how Runeterra looked like before Rune Wars, maybe there was a place like this in Shurima. Their migration points seems pretty... unconventional, but I assume this game doesn't really care for it, I mean, those characters joined the game, when Riot tried to catch fans attention, so they included people of all races without even thinking of genetics. In my honest opinion putting Karma in Ionnia is extremely racist and ignorant, mostly because the diversity of Asian cultures and ethnicity come from its enormous size (as we know, Ionnia is extremely small, to small to be the place of origin of both hindu-like people, eastern asians and caucasians). But, what do I know, this isn't probably worth any effort, so I'll just stay still until Riot decide how it all started.