I think this is generally true, but it might be more correct to say this: The oldest surviving culture(s) for a particular landmass and / or the existing cultur

I think this is generally true, but it might be more correct to say this: The oldest surviving culture(s) for a particular landmass and / or the existing culture(s) present for the first wave of recorded migration. We have good evidence that the Mayan and Aztec peoples had groups that preceded them on the land, but they are still indigenous.