Imagine that, aside from a few wanderers and pilgrims, no one ever returned to New Orleans. Imagine that the thousands of people who fled the French Quarter, the Ninth Ward and other neighborhoods in the face of Hurricane Katrina turned their backs on their homes, on the shops and the bars, and let them sink slowly into the Mississippi River Delta mud.

Now, imagine that 1,000 years later, you arrive on the scene, all written record of what happened having long ago been lost. With a little digging, you find houses abandoned, the contents of the former residents’ lives scattered, or, in places, still sitting exactly where they were left. You find couches and clothing, forks and knives, framed photographs.

Imagine trying to piece together what happened there, in the last days before the exodus.

That’s what archaeologists in the Four Corners region have spent the past century doing: slowly assembling the pieces of a grand puzzle that explains why the Anasazi people left the area roughly 700 years ago. Craig Childs, the author of 11 books about nature and the Southwest, has worked with many of these archaeologists, and as he writes in this issue’s cover story, there is no simple solution to this mystery.

There was environmental calamity, to be sure — in the case of the Anasazi, it was a great drought. But there was also a massive buildup of humanity just before the fall; there was fire and murder; there was ritual and ceremony. The more pieces we find, the more complex the puzzle becomes.

New Orleans’ story might shed some light on the Anasazis’ fate, however. Residents there knew they were living in an inhospitable place, and that their defenses might not stand up to a major storm. But Katrina still caught the city flat-footed. Thousands who didn’t have the means to leave, or who had weathered storms before, dug in. We read about the price they paid: Hundreds died; many more were stranded in flooded homes or on rooftops. And of course, there were the tens of thousands who sought shelter in the Superdome and the convention center, with the promise of temporary shelter and quick evacuation.

There were also those who made it out in time, carrying their belongings with them, and those who stayed to help. But what was most striking about Katrina’s aftermath was just how quickly society unraveled as help failed to arrive — the bands of gunmen roaming the streets, the murder and the rape.

The fall of New Orleans isn’t as simple as, "Storm hits, residents flee." It is a story of nature’s immense power, but it is also a story of a government’s failure, a society’s fragility, of the light and dark sides of human nature.

In the end, the story of the Anasazis’ exodus from the Four Corners must be the same: both epic and mundane, monstrous and human. And as we set out to rebuild New Orleans, the Anasazi may have lessons for us — lessons about the beauty and the risks of building a society in a region as harshly indifferent to human wellbeing as the Four Corners — or the Mississippi River Delta.