Perhaps I should have elaborated a little more here; crossed my "I's, dotted my "t's", and patched up any lingering cavities in the molars of human migration.
I'll start again: let's not worry about those impediments to human migration- those formidable unsmiling oceans that break over two thirds of the planetary surface; drifting continents, massive mountain ranges, vast deserts...., ICE ages etc; let's say these irrepressible proto-humans did scamper across mountains, breast-stroke over impassive oceans, tiptoe across the occasional earth-tremor and dodge the odd inconsiderate volcano...., for a hundred thousand years; for it's what they did in the next thirty thousand years that reveals their inherent sedentary nature.
As I suggested earlier, most humans- like most other species- stay put when they find conditions benign enough to support the rudiments of life; they put down roots, put up fences, fight to the death to protect their own patch of land. Even the last of the hunter-gatherers, the australian aborigines, would not stray outside their own tribal territory[ they would go 'walkabout' through the course of a year, but strictly within tribal lands]. And in almost every other sphere of life human beings are prone to opt for the 'familiar'; to reject the 'new'- the unfamiliar; whether it be in regard to people's of another colour or the latest movement in modern art. What this amounts to basically is that the 'territorial imperative' seems stronger in contemporary humans than the impulse to explore the unknown.
What I am suggesting overall is that there must be some underlying impulse that propels humans- other than the needs for nutrition and progeneration- to defy impossible odds and cross oceans and make their way to the moon and beyond[ that is also in defiance of reason and that basic instinct for survival ]....,and that this rogue impulse is the same compulsion that drives whole people's to construct impossibly large and seemingly useless monuments over the planetary surface.
And what I am asking is:
is this seemingly irrational impulse genetically encoded within human nature, or is it perhaps an 'external' force that is directing the course of human evolution??