"Hunter-gatherers led the least intrusive lifestyles. ... The land and its varied flora and fauna was kept pristine."

Totally delusion emotive 'fuzzy feeling' belief, sorry - the documented evidence shows the land did not remain the same, it kept changing - at a much slower rate only because they had less destructive power than later arrivals.

Even Australia's fauna and flora has changed over the alleged 40,000+ years of since human arrival towards a type of fauna that burns more easily, and results in the land being drier, driving out the rain forest ecology, due to the 'fire-stick farming' practices, which caused a new living balance. When left alone, the land rapidly becomes clogged with highly flammable materials which causes greater devastation to the fauna, and has the long term potential, depending on the right weather conditions, to lead to massive erosion and eventual desertification.

There is evidence that similar changes have occurred in the continental USA.