 The corn stalks functioned as a support for the beans.The beans fixed nitrogen into a usable form for the corn and squash, and the broad squash leaves provided shade for the soil, which aided in preventing evaporation and controlling weeds(Kowtko 2006, 54).As the success of the Three Sisters spread, many cultures turned away from hunting and gathering and relied much more on farming (Kowtko 2006, 55).