Credit: Carl Wiens
We won’t ever know what the Anasazi were thinking on the eve of the 13th century when they abandoned the cities they had worked so long to build on the Colorado Plateau. The reasons had something to do with climate — a great drought and, perhaps on top of that, a mini ice age. If that wasn’t enough to defeat a thriving culture, there was the turmoil that came from just not knowing. Why were the sky and earth behaving so strangely? Why wasn’t the old magic working anymore?
The rains were not just sparser. They were no longer coming when they were supposed to — when the seedlings were in the ground waiting for water. Cooler temperatures were putting an earlier end to the growing season. Fields had been overplanted, forests stripped of wood. Crops were failing as people reverted from agriculture to hunting and gathering and fighting violently over food.
Chaco Canyon and Mesa Verde — these grand stone settlements fell silent, repurposed centuries later as national parks and monuments, memorials to the repercussions of ancient climate change.
There are many theories seeking to explain the abandonment, abstracted from faint clues in old rocks and bones and in the patterns of tree rings and pollen deposition. By some measures, there was enough water, just barely, for the Anasazi settlements to hang on. And there is evidence that they had survived drier times. A more complex story has emerged as archaeologists try to infer what they can from changes in architectural styles and pottery design — hints perhaps of a people trying out new rituals, new ways to entreat suddenly indifferent gods.
Something was happening — a slow horror, perhaps so slow that it didn’t feel like a horror, until the Anasazi’s culture began to unwind. Did their leaders engage at first in denial and then quiet deliberation? When that failed, did communities split into factions with the conservatives insisting on standing their ground — clinging to the old ways and waiting for the rains to return — and the liberals pushing for new approaches? Did a visionary arise? Some Moses leading a migration? Or three Moseses leading migrations in different directions?
One way or the other, the Anasazi disintegrated, the people moving southward. Their descendants are believed to live now in the pueblos of New Mexico and Arizona, perched on mesa tops and hugging the banks of the Rio Grande.
In modern times, many of these pueblos divide themselves, for reasons they keep from the anthropologists, into kinship groups called summer and winter people or squash and turquoise people. Could these divisions be imprints left from that 13th-century upheaval?
It is frustrating how little is known. Compared with the Byzantines, the Normans, or the Mongols, the Anasazi left such faint traces, like ripples from the radiation of their own Big Bang. They have an oral history but it is mostly secret. And there is only so much that can be derived from mythology. The closest we have to records are the crude rock etchings called petroglyphs. Were these symbols in a rudimentary language or just doodling?
Our own deliberations — imprinted onto electromagnetic waves — have been pulsing outward from Earth since the first radio news shows in the 1920s and 30s, interspersed with the “Grand Ole Opry” and the “Amos ’n’ Andy” show.
By now broadcasts about greenhouses gases, melting ice caps and rising sea levels are rippling far beyond Alpha Centauri, along with the carefully calculated outrage of Rush Limbaugh and Glenn Beck. As the waves travel farther, they converge asymptotically toward a vanishing point. Even at their strongest they might seem as esoteric to curious aliens as Anasazi rock art.
Our later emanations, if they are ever understood, might tell of great feats of geoengineering: swarms of orbiting mirrors to bounce back sunlight, oceans fertilized to create carbon-absorbing algae blooms.
The Anasazi had to make do with simpler technology — water catchment basins, irrigation channels. But when all else failed at least they had somewhere to go.
Stuck here on Earth, do we embrace the Anthropocene — this new geological epoch in which the human race has become its own force of nature? Or do we hunker down for the sixth extinction? Faced with the dilemma, we cleave as naturally as a crystal into factions, like the squash people and the pumpkin people.
Diane Ackerman is one of the latest to join the environmental optimists, who believe that the same kind of technological prowess that got us into this mess will help us adapt to it, in ways we can only begin to imagine. (Her new book, “The Human Age: The World Shaped by Us” is reviewed on Page 5.)
With her following, Ms. Ackerman may become the counterpart to Bill McKibben, the environmentalist whose book “Eaarth” (he changed the name of the planet since we have irremediably transformed the place) called for a return to simpler times with backyard farms instead of lawns and decentralized green energy. The Anasazi with solar panels on the roof.
Finally there is the 25 percent of Americans (“cool skeptics,” as a Gallup poll called them) who don’t believe the keepers of the models — the interpreters of the signs. As we flail we are generating so much data that future archaeologists, if they exist, may be overwhelmed — the opposite problem presented by the Anasazi.
More than 700 years after their fall, we have the knowledge to tell us what is going wrong this time with the atmosphere. But that has made it no easier to agree on a plan. Science can only lay the case out on the table. For all our supercomputers and climatological models, what happens next will come down to something unpredictable: the meteorology of the human mind.