alternatehistory.com

So, I was reading up on some information about the population of India and China, and the question in the title came into my mind. They both have the advantage of highly developed river valleys, and they're not hurt by surrounding desert like Mesopotamia or the Nile. The only places that come to my mind are the Mississippi Valley, if it had the same history of development that these two had had, or possibly some sort of hyper-developed Europe. But would even those be able to support such massive populations, or are there other places which could do so?
Top