And still the only unhappy tribe wishing to return to the happy forest life, are bored urban office staff and hippies; while the former happy tribes, having migrated from the happy tree friends life to the low-life suburban reality, prefer to keep their new unhappy life.
Probably, the happiness of the HG life is overestimated.
The San still survive because they do it in the most poor regions of the desert, unappropriate for the more developed (and thus numerous) Bantu, who need pastures and plowlands.
So, they are separated by lack of interest.
Family settlements can evolve into fortified family settlements, where all citizens are relatives, and an alien has poor chances even to survive, let alone become a true human.
The city is principally different. It consists of individual families, whose place in the city hierarchy is significant, while their family hierarchy is very short and doesn't play much role. Any urban family can be easily replaced with another family.
All what the family tribal people can reach without external invasion, is a large family clan settlement, where everyone has his role, and is stuck in the family hierarchy.
They don't need development, they are happy with primitive technologies. They need to capture more land, to grow or steal more cattle.
If one of them has moved to a city, he is pushed by his family, and is pulling other family members, to create a family outpost in the city. Then he tries to corrupt the city officers to let the clan capture the city commandment, and then starts pumping money into his family clan settlement.
That's the only way of thinking, available for the family tribal society. That's not how a city can appear, let alone the empire.
The only way to appear for the urban civilisation is when some local authority combines an intertribal gang army (protoEmpire), cut out the majority of other clans (to decrease their need in fertile land, to behead the tribe, and to disintegrate the tribe hierarchy, making belonging to the clan insignificant and dangerous, enough to become forgotten), and let the survivors (together with the clans who surrendered) settle at the special places under commandment of the Imperial gang teams.
Then the Empire must start extracting all strong/brave men from the conquered clans (by provoking them or by kind suggesting), by recruiting them into the Imperial army with no return, and by killing those who is enough strong and brave to rebel, but doesn't want to be recruited. Violence against the conquered women is the usual way to provoke and select the possible rebels. Also the best women from the conquered clans should be taken away into the Imperial cities as wives and mothers.
At some point the conquered clans get dissipated and assimilated.
That's how it worked.
But this requires several conditions:
1) the Imperial culture must be enough developed to feed both conquerors and surviving conquered, and to feed the great amount of soldiers;
2) the Imperial culture must provide the Imperial gangarmy with advanced weapon (iron knives and axes vs stone ones, maybe horses);
3) the Imperial economy should be developed enough to mass produce food, tools, and weapon;
4) there should still exist a primal authority, like a famous military cult sanctuary, obedience to whom is unquestionable for the tribes of the intertribal gangarmy; also it's their military and administrative brain, central bank and storehouse, military academy, etc.
This means that the cities and the empire can appear only in a metallurgical society living on a fertile land.
And once such empire has appeared, it will smash any proto-empires around, because it started first.
To become such empire, they should first become peasants rather than hunters, because the agriculture automatically increases their population density by orders of magnitude.
So, the hunters-gatherers, co-existing with the agricultural society, automatically become a marginal minority, and either get assimilated, or get eliminated.
The co-existence of the named Amerindian peasants and hunterers at one place just illustrates the pathetically low production of their agriculture. That's why any their settlement had no chances to become a city.
Any tribal settlement is just a tribal settlement, it's not a city and doesn't have a chance to become it.
Especially since the American continent and Pacific islands have rather poor nature in sense of farming. It was modified by hack-and-slash, crop rotation, artifical fertilizers, and the biota replacement (the earthworms, the cattle manure, etc), and it's either equatorial (so what's not in jungle, turns into desert) or mountains. So, it just looks like a green hell with parrots, but actually it's a swamp in a desert or a rocky desert.
So, the Amerindians and the Pacific people had poor chances to develop something much more advanced due to low fertility of the territory, causing low population density, which was making useless or impossible any technological efforts (you can't be a potter, when your village is a hundred of people, and they use palm leaves and grass baskets).
Yes, the civilisation never was a product of good will and kind intentions.
But others disappeared.
De mortuis nil nisi bonum.
