It's also flowing from higher elevations to lower elevations. So as you go south, you get to higher and higher elevations. Now, the reason why the river is so important, we've studied this multiple times, rivers are a source of fresh water. When they flood, they make the surrounding soil fertile. They're suitable for agriculture. And the Nile Valley is one of the first places that we see agriculture emerging during the Neolithic period. In fact, human settlement, we believe, was along this Nile River Valley as far as 6,000 BCE, or 8,000 years ago.