in the American Southwest, the overall trend for 500 years or so before Europeans arrived was the gradual abandonment of maize and beans, which people had been growing in some cases for thousands of years, and a return to a foraging way of life. If anything, during this period Californians were the ones doing the spreading, with populations originally from the east of the state bringing new foraging techniques, and replacing previously agricultural peoples, as far away as Utah and Wyoming.
