Native American Documentary - The Dark Secrets of The Ancient Anasazi.
This is my assessment .. the Ancestral Puebloans were a race of builders from Mexico who migrated north sometime around 700 AD to escape the culture of human sacrifice and cannibalism that flourished south of the border, they were farmers and tillers of the soil and settled peacefully in Chaco Canyon, where they used their building skills to erect the amazing Great Houses and towns a la Pueblo Bonito.
Pueblo Bonito & Chaco Canyon Culture.
.Then at around 1200 AD or so another tribe came up from Mexico these were the Anasazi which means ancient enemy in the Navajo tongue, they were cannibals who raided the Puebloan towns and great houses, murdering and eating those who would not survive the journey south and taking the rest back to Mexico as slaves
Ancient Cliff Palace in Mesa Verde, Colorado.
Not withstanding the Mexican cannibals did not stop at Chaco Canyon but progressed all the way into Utah seeking, searching and cannibalising as they went, a la Professor Turner finding evidence of cannibalism right unto the extent of their range .. the surviving Ancestral Puebloans had never lost their building skills and built the very elaborate cliff dwellings we see today as places of refuge.
Alpha Fort - The Greater New River Mesa.
The depredations appear to have continued until the Chaco Canyon culture per se was wiped out, where after the survivors were absorbed by the Hopi and the Navajo!However the Anasazi eventually located them and laid seige, as before they took the skilled workers back to Mexico as slaves and ate everyone else, the survivors still had the building ethic however their skill level had decreased exponentially, thus the hilltop forts and lookouts they built are the rude dry stone constructions we see today in Arizona and New Mexico.