Answer:
The official Early River Valley Civilizations are in Mesopotamia, India, ... and across history had some of the greatest cultural and ethnic diversity.
Explanation:It's easy to take the idea of civilization for granted. We are pretty used to the concept of a highly-organized, complex, and completely sedentary society featuring political and social organization. But, as with everything else, at some point this style of society had to be invented. Around the world, we find places where the first civilizations popped up, independently of anything else, and inspired changes throughout that region. We've also noticed that most of these first civilizations tend to have one thing in common: access to fresh water and fertile soil. It makes sense: you need water and food to build a large, non-mobile society, and so we call these the Early River Valley Civilizations. The official Early River Valley Civilizations are in Mesopotamia, India, Egypt, and China, but what about the Americas? The Western Hemisphere was full of advanced civilizations too, and those came from somewhere. Not all of these societies were necessarily river valley based, but they were the first, and that's worth looking at.