Indeed.
20,000 years of human history without omission in a single paragraph, far beyond my skill level. BUT !
I mentioned Barry Farber earlier today. He said "Oy!" is 4,000 years of Jewish history reduced to a single syllable.
Omitting?
I was contemplating the variety of habitats, & cultures of the various aboriginal American nations as I was composing that post.
I do not know if their chieftains knew of the common ancestry of the neighbor nations they traded, & warred with.
But surely Cherokee & Paiute had different life-styles / survival skills than the Mohawk & Ojibwa.
No hurry.
Psychologist Joy Browne acknowledged we move toward pleasure, and away from pain.
I suspect the lowest pain path appealed to many.
Bear in mind, even in stone-age culture there is division of labor.
There's a African proverb: To go fast, go alone. To go far, go together.
It's a cognitive blunder to ascribe single or simple motive to 20,000 years of human history.
No doubt motives driving the 9,000 mile migration included love, hate, Nitrogen depletion of the soil, & countless etc.

Some say Mars.