I am aware of this.
Various groups of humans have been expanding and contracting in their range ever since mom and dad's ancestors got kicked off Mars/Venus/out of Eden/evolved up from the Engineer's DNA at an Icelandic waterfall. Some groups get overrun by the next expansion wave, some contract on their own, some mingle and forge new identity, etc.
I like to think everyone knows this hence my lame attempt at a little levity.
Now to digress, it seems curious to me that there a more than a few stories in various parts of the world about "magical" people who lived/acted in mysterious ways that did things that "modern" inhabitants didn't understand. Over time, mythology develops, fact becomes fiction, but memory of sorts is preserved. Though I have zero proof, part of me thinks these stories are a way of knowing that there were people here before (the current population killed them off/chased them off/ruined their way of life such that they died off). Sure, making a myth out of earlier people could be used to denigrate their existence (thus making it easier to live with any atrocities), but the other side of that coin, is shared memory/recognition that today's humans stand on the shoulders (and broken bones) of those who went before. Reconciling the yin and yang of past, present, and future, is tough work, so again, tiny bit of humor, and occasional delicious fermented malt beverage, seemed to be called for.
PS
Sorry Mrs. McGrevey for ending that last sentence with a proposition.