Göbekli Tepe actually proves that highly organized cities are a lot older than agriculture itself. More broadly, there's a lot of circumstantial evidence that civilization - at least as in highly developed cities allowing for trade, exchange, production of material goods and even creation of impressive stone monuments - is in fact older than was previously thought. Many of those unknown civilizations may been affected by prehistoric cataclysmic events that left their trace in myth, such as the flooding of Doggerland or of the present-day Black Sea due to ancient sea-level rise. That same sea-level rise also means that much of the prehistoric coastline, where the most interesting sites would likely be found, is now well underwater.