Question

How did the domestication and cultivation of grains and legumes lead to the building of cities and political systems?

Answer 1

Wow, this seems more like a history question than Biology.

Answer 2

History, yes. But i'll answer anyway. In a nutshell: wherever there is food, there are people. People basically had to live around wherever food was available. Now that they no longer had to chase after buffalo/animals, they stayed stationary and started communities leading to cities and political systems in the long run. hope this helps! ask if you need more :D