Where are all the cities?
Where is the archaeological evidence!?
Where is the archaeological evidence!?
I think that at the stage of development being suggested, there were no "cities," only a group of long term shelters, with associated hearths, storage pits and the like. IOW, you would have a population formally believed to be strictly hunting and gathering nomads, following herds and seasons "suddenly" (funny term for the span that would have been involved) setting down roots hundreds of thousands of years earlier than anyone else on the planet thought to.
If they died off, as many populations did throughout the stone ages, plagues, drought, predation etc, such innovative thinking would have died with them. Of course such a hypothesis must be scrutinized with appropriate skepticism, but its intriguing nonetheless.