> If these people never went through the social evolutions the rest of the world underwent, they are indeed travelers from the past.

Logical error. That they didn't go through the same social evolutions that we went through doesn't mean they didn't go through any social evolutions at all.

(And indeed they must have; even keeping their societies static takes conscious effort, in the same vein that conservative reactionaries today aren't at all the same people, ethically and sociologically, as the simpler ancestors they try to emulate.)