Anthropologists believe that civilization emerged independently in only the following six places: Mesopotamia, Egypt, India, China, Mesoamerica, and the Andes. What all of these civilizations have in common is that they were created by either Mongoloids (China, Mesoamerica, the Andes) or Caucasoids (Mesopotamia, Egypt, and India). The reason why only Mongoloids and Caucasoids independently founded civilizations is that only these races had sufficient exposure to the ice age to evolve the intelligence needed.
And yet ironically, it was the least intelligent Caucasoids (Middle Easterners, South Asians) and least intelligent Mongoloids (Native Americans) who made almost all of these civilizations. Why didn’t the more intelligent Caucasoids of Europe originate a civilization? My guess is that the climate was just too cold.
And so we have a paradox. Civilization requires both a smart population and a warm climate to emerge independently. The problem is, unless the climate is too cold for civilization, the people will never evolve the smarts for civilization.
This explains why in the 200,000 years of human history, civilization only emerged in the last several thousand years. Before the ice age, all human populations were just too dumb for civilization. During the ice age, it was just way too cold for civilization. Only after the ice age ended were there people who were both smart enough and warm enough to originate civilizations.
Scholar Michael Hart made a similar argument to explain why agriculture emerged when and where it did, though agriculture probably didn’t require much intelligence since it appears to have emerged independently in Papua New Guinea, suggesting it is not beyond the intelligence of Negroid populations. It is however probably beyond the most primitive Negroids (i.e. Bushmen).
The invention of agriculture was probably only possible once some human races had exceeded an average genetic IQ of 73. By contrast, independent civilizations likely required an average genetic IQ around 90.