There is a huge void in the history of man from the neolithic age up until about 10,000 years ago.
That spans about 50k or so years.
What was going on during that time?.........................
Yeah, that is a fascinating question. Apparently there is evidence of high civilization in Turkey (and perhaps in South America) prior to the Sumerians but not much has been excavated of it yet. Of course, determining the time of something becomes almost a matter of faith when there is no writing.
One of the most fascinating and mysterious sites is Puma Puku in Bolivia or Peru. Too lazy to look it up. But the workmanship of the stones is at today’s standards or better.