Water is humongous in terms of early development of civilizations. So river valleys, and not just rivers, but river valleys, where the river kind of flows low and usually into a larger body of water is generally where we find the Neolithic world development. Remember, the Paleolithic world is more of, or the Old Stone Age, is more of people really being nomadic and kind of wandering around, still based on geography, but more about kind of weather and the scarcity of food supply, chasing the buffalo or the Ice Age, those kinds of concepts. And as the Ice Age comes to an end, you know, people differ about this when the Neolithic Age started, but I would guess anywhere from 30,000 years ago to 10,000 years ago, you start having people chilling, you know, where they're going to discover that near these early, you know, these river valleys that they don't have to keep traveling because they have the ability, because of the geography, to grow food. And eventually, animal husbandry, where they can domesticate animals and they don't have to chase buffaloes and such. So the examples on the test most often are Egypt, that you have Egypt developing by the Nile and all of the rich soil there. You have the Tigris and the Euphrates, where you have Mesopotamia, Babylonia, those early early civilizations develop into city-states.