Oddly enough the rich resources of California never bred any highly civilized peoples. When the Spanish came they found quite primitive hunter-gatherer clans. Unlike the Misissippi and Ohio river cultures. Or even the agricultural Iroquois or Algonquins.
Years ago the story I read was that the Aztecs had arrived not many cdnturies earlier in the Valley of Mexico, saw an eagle sitting on a cactus by a lake and settled there. Originally it was said they came south from an especially savage small tribe living in the harsh desert lands between the Valley and the US area.
I don’t doubt that cannibalism had its place in the overall survival behavior in troubled food situations. However, specifically with regard to the Aztecs, apparently several generations before the Spaniards arrived a chief advisor of the Aztecs proposed making this a state policy supplied through the ritualistic “flowery” wars against neighboring tribes, especially against the tribe called Tlaxcallans. As a consequence, guess who became Cortez’s chief allies—the Tlaxcallans. Further interesting factoid, guess what the Aztec (Nauhatl) word for tortilla is—tlaxcalli. It has been suggested that the tlaxcallans provided Cortez’s 150 man “Army” with around 200,000 warriors when they invaded tenochtitlan. European guns and horses, made the difference, but angry Tlaxcallans made the victory possible. They were tired of being “lunch”. In their everlasting gratitude, the Spaniards succeeded in robbing the tlaxcallans, “legally” at every chance they could to claim land and other wealth.
Major Indian settlements in Mexico and Central America did not have any large protein animals as were available in the US area like Buffalo, Elk, and deer. For protein they were dependent mostly on turkey, and fish. Human meat, yummy.