> The average American would understand if those two branches lived among us today

Shall I break the news or you find out yourself?.. ok, I will do it.

Those two branches do live among Americans. Afro-American people have the biggest genetic diversity in America and their genetic subgroups are so distinctive that they require separate testing in clinical studies. I bet you won’t be able to tell the difference between them from their appearance though. Now good luck redefining the concept of race with this knowledge.