One of the myths that's floating around is the romanticized image of hunter-gatherers. Back to at least Rousseau, people have imagined that contemporary society is horrible, but that ancient humans were somehow more in tune with nature.
As with all idealized images, this is not quite true. Ancient societies were considerably more violent, both to each other and neighboring tribes, and were probably responsible for many mega-fauna extinctions. They were probably more prosperous than following agricultural societies, and possibly many contemporary societies.
This idealization extends to ancient Americans, who were thought either savages unfit to manage land or else the best people who ever lived--a standard to which we can compare and degrade our own unsustainable follies. As it turns out, civilization in pre-contact America was extensive, long-lasting, highly urban, highly dependent on agriculture, and had a dramatic impact on the landscape from the Amazonian jungle to the North American plains. The vast herds of buffalo and birds encountered in the 19th century are not a legacy of a pristine past, but a direct result of the deaths of countless residents due to Old World diseases. Ancient societies managed the landscape at will, with many destructive consequences and other good ones. Contemporary societies are doing the same.
It's also interesting that new discoveries are pushing back the dates of the earliest American finds to be contemporary with the earliest Asian river-based civilizations. Somehow, human societies independently discovered parallel technologies and social organizations at around the same time. I guess there is some rate of mental evolution necessary to make these advances which hit a threshold worldwide around that time, aided by global climate trends.