Science Alert reports:

In the area where the Colorado, Utah, Arizona and New Mexican borders now meet, ancestral Pueblo societies thrived and then collapsed several times, over the span of 800 years.

Each time they recovered, their culture transformed. This shifting history can be seen in their pottery and the incredible stone and earth dwellings they created. During 300 of those years, some Pueblo peoples, who also used ink tattoos, were ruled by a matrilineal dynasty.

As in the collapse of other ancient civilizations, ancestral Pueblo social collapses align with periods of changing climate – but Pueblo farmers often persevered through droughts, suggesting that there was more to their collapses than just environmental conditions.

So last year archaeologists took a closer look at what was happening in these societies, before 1400 CE, leading up to their times of upheaval. Using tree-ring analyses of wood beams for building construction allowed the researchers to construct a time series of the Pueblo societies’ productivity.

Peak construction periods were clustered around good maize growing seasons, even though these times, on average, were not climatically better for growing maize than when there was a lull in said construction.

The recent research found that while the societies often bounced back fairly quickly after construction lulled, there were distinct slow-downs in recovery that coincided with increased signs of violence.

This sort of system slowdown can be seen in other regional collapses of ancient societies like the Neolithic Europeans, that had no link to changing climates. It’s also a feature of complex systems as diverse as the tropical rainforest and the human brain. [Continue reading…]