1) The first great megalithic stone circles were built by hunter-gatherers at Göbekli Tepe. They deliberately buried their construction 7,000 years before we see any evidence of city-states in Sumer, the constructions of Old Kingdom Egypt or the structures of Stonehenge (http://www.andrewcollins.com/page/articles/Gobekli.htm).
2) The great Egyptian pyramids never contained mummies. Like us, the Ancient Egyptians buried their dead in tombs: https://awhico.com.com/blog/egyptianpyramidmysticism. We are still trying to figure out the real purposes of the pyramids.
3) Modern civilized components such as literature, libraries and codified laws were well established in Sumer millennium before the Babylonians or Greeks: https://awhico.com.com/blog/egyptianpyramidmysticism.
4) In North and South America humans were happy and productively “farming” long before Europeans arrived. The area was densely populated with healthy and civilized people http://planet1051.com/ancient-louisiana-city-poverty-point-is-as-old-as-the-pyramids-in-egypt/ or https://en.wikipedia.org/wiki/1491:_New_Revelations_of_the_Americas_Before_Columbus.
5) Much of sub-Saharan Africa was densely populated before Europeans “arrived”. We are still trying to understand the many, many, many stone circles in southern Africa: http://www.thesouthafrican.com/200-000-year-old-city-found-in-southern-africa-set-to-re-write-history/.
6) Hunter-gatherers continue to persist in highly evolved cultures around the world today. They may be the most resilient form of human cultures. See what Graham Hancock says about them: https://youtu.be/aDejwCGdUV8?t=2h23m4s.