A short extract:
This, I think, is interesting as showing how adaptable people are and how the types of foods they eat and the methods they use to obtain them can change over time. Here are people going from gathering to farming, then back to gathering again, and finally moving to hunting. All this in response to changing conditions and to influences upon them. And more than one of these food-obtaining activities can be taking place at any one time.
About AD 400 conditions for, and knowledge of farming were sufficient to establish the Fremont culture in the eastern Great Basin. Desert culture food collectors began to cultivate maize, beans, and squash. Their villages pottery and fields were small-scale versions of Mogollon and Anasazi farm life in the Southwest. They continued farming until AD 1200 when they returned to food collecting and to bison hunting around AD 1500, possibly due to the increasing aridity of the area. While farming they had continued their food collecting, so agriculture never completely replaced their old methods.