What do textbooks normally do to the river valley civilizations?

Textbooks normally frame the river valley civilizations as the first civilizations. As rivers were great sources of water, and generally created fertile arable land on the banks, these locations also allowed for goods and people to be transported more easily, and allowed for fishing and hunting of animals that came to drink. These early civilizations were known as hydraulic empires as they commanded the river and exerted control of access to the water sources within their governmental structures. These river valley civilizations were seen as the first and as the innovators for new technologies.

I believe the answer is: River valley civilizations are oftentimes split up into separate civilizations.

Many textbooks described that river valley civilizations eventually split into several regions which later on become Egypt, Mesopotamia, and China. Even though this is entirely possible, there is no solid historical proof that could be used to defend this claim.