This is fascinating. Gobekli Tepe, an archeological site being excavated in Turkey, is many thousands of years older than the first "known" civilizations, 10,000-8,000 BCE, when Mesopotamian Sumer, the "first," was dated to about 4,000 - 3,500 bce.
The tell includes two phases of use, believed to be of a social or ritual nature by site discoverer and excavator Klaus Schmidt, dating back to the 10th–8th millennium BCE.[4] During the first phase, belonging to the Pre-Pottery Neolithic A (PPNA), circles of massive T-shaped stone pillars were erected – the world's oldest known megaliths.[5]
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So there were advanced civilizations occurring five to seven millenia before what has been thought. Some anthropologists surmise these people came from coastal areas that had been displaced by great floods because some of the animals and plants depicted on the pillars are not native to that region.
One thing that is so fascinating to me is that the giant pillars are shaped and arranged so similarly to the megaliths at Stonehenge.
I'm including one link--it is an amazing discovery. Lots of places you can look.
Göbekli Tepe - Wikipedia