8. The Sumerians - Fall of the First Cities

Arizona is very hot, very arid, and also very favourable for agriculture, with significant production of lettuce and cotton. As long as you can make sure your crops get water through irrigation (which ancient Mesopotamians were very skilled at), your crops will thrive. In fact, the heat and sunlight actually provide a bit of an advantage. However, a number of factors eventually led to the collapse of the civilisations in the fertile crescent. One factor has been the region getting warmer and drier, which poses a challenge even with irrigation. As an example of how different the climate is now from what it was then, Uruk used to be on a channel of the Euphrates, but now that riverbed is completely dried up. Meanwhile, Ur was once a coastal city, but is now ten miles inland. Another factor for the collapse of these civilisations is that the process of irrigation accumulated salt in the soil. The very process that made complex civilisation possible in this part of the world eventually contributed to its end. I recommend the Fall of Civilizations podcast for more on this and other societies: [this video]