To gain a clearer perspective on just how their founding agrarian communities coped with a harsh and sudden climate shift, the researchers amassed a database of hundreds of food materials and their radiocarbon dates, all collected from 230 dig sites across the region.
The ages, densities, and locations of the agricultural products reflected a story already familiar to archaeologists, of a widespread population – broken up into lots of smaller, localized settlements – practicing farming techniques that suited their local conditions.
Up to around 400 CE, the land was a patchwork of foragers and farmers. Some were more the latter, growing more substantial crops that included maize and beans to supplement diets.
Significantly, by the 6th century, a sharp rise in population growth began to limit the amount of farmland available. Where dispersed kin groups were once keen to pack up and move when opportunities presented, by the middle of the century they were sitting tight and collaborating with their neighbors in more complex social groups.
Comparing the evidence of this cultural mixing in their database with the climate records represented by tree rings from the Colorado Plateau, the researchers argued there was a strong link between the climate changes and cultural shifts.
"Archaeologists have long recognized that demographic and social change transformed Ancestral Pueblo societies during the late 6th and early 7th centuries CE, but we contend that these changes are best understood when juxtaposed with the consequences of extreme cold at the beginning of this interval," the team writes.
The hardships in the wake of the year 536 CE put the mix of emerging communities across the southwest to the test. Some could reorganize, developing socio-political ties that saw them through. Others failed to flourish. In the end, the years from hell served as a selection process for cultural practices that could bring people together and allow them to share their experience to weather the tough times.
For instance, an ancient farming community that occupied the Cedar Mesa and Grand Gulch was known to raise domesticated turkeys. By 550 CE, this practice was common across the entire southwest region, indicating a sharing of knowledge and a push to diversify food sources.
Within a few generations, the skies cleared once more and good times returned. Armed with new cooperative social practices, the Ancient Puebloans would go on to establish a rich, resilient civilization that would last centuries.
