The Pueblans, who we often call the Anasazi, inspire our imaginations because their archeological story is a sad tale, a mystery, but ultimately, a mystery that keeps leading back to a man-made environmental collapse. Recently, as discussed in Jared Diamond's Collapse, scientists have been able to paint a much clearer story of what happened to this great Southwestern civilization. They cut down all their trees, which created a set of conditions: loss of storable staples like pinyon nuts and erosion of the valley floors, which eliminated their foragable food sources.

A western pipistrelle bat hunts in the morning canyon light

When the Pueblo world began to collapse, warfare broke out, and to survive, small bands of Pueblans would hide themselves into fortified structures, high in the cliffs, in places so remote, nobody, under normal circumstances would consider them.

I ponder whether the structure next to me is such a place. Was it a beautiful spot for a family home, next to a lush valley below? Or was it the last resort for a terrified family, defending their meager stock of food?

As I think about this, a hiker notices me and invites herself to chat. She remarks on how well the small structure is preserved. I realize she knows quite a bit about the area, so I invite her into my thoughts. I am a hiker-trap, whenever my large format camera is unfolded. Hikers love to talk to people with big cameras.

We talk about the condors that have already been reintroduced to this region.  Their numbers still precarious, they are the symbol of a subset of habitat restoration called rewilding.

I ask the hiker, who says she is part of a Sierra Club chapter in Arizona, what she thinks about the idea of rewilding Southern Utah - bringing back the bison, the big cats, the brown bears.

She is familiar with these ideas, and in fact, is familiar with an effort called the Yellowstone to Yukon Initiative, the most successful alliance to create a migration corridor for the big animals of North America.

Out loud, I wonder how important rewilding would be to restoring habitats - to, "not making the same mistakes as those guys," pointing to the Pueblo ruin. "What good are condors to habitat restoration?"

The hiker, who has a sort of middle-age lesbian gestalt to her, positions her arms like a teacher, constructing thoughts with her waving movements. She puts her big boot up on a rock, and says, "The big animals have more of an impact on the environment than we think. But we just don't know everything. Some people think we don't need to know everything about something's importance, to restore it."

I tell her about a book I read called, '1491', which looks at the Americas before Christopher Columbus. Archeologists are piecing together a much more complex idea of what native America was like. Again and again, we are learning that the Indians controlled, changed, and sometimes destroyed their environment much more than we had ever imagined.

"Why do we want to restore America's wilderness to the way it was before Columbus?" I said, asking her a question I had been thinking about for weeks, again looking at the stone home next to us. "Why not restore it to the way it was before they got here?"

I tell the hiker about the the idea of pleistocene rewilding, where, instead of restoring habitats to a pre-Columbian state, you take it all the way, to 11,000 years ago.

She says, "Okay, that's absurd."

I say, "There are people who think we need to do that."

She says, "The animals that existed here when the Indians came over are extinct."

"The Indians killed them."

"Sort of, yes," she says. The biggest ones. The mammoths."

We talk a while. The whole time, I wonder if she is imagining big animals running across the mesas in the distance, as I am.

When the hiker bids farewall, I stay out on the cliff, watching the skyline, the arch below, the nutcrackers squabbling from their roosts. Not just mammoths, I thought, but giant sloths, sabertooths, mastodons, llamas, peccaries, dire wolves, stag moose and giant beavers.

It is hard to imagine that the first Americans actually lived among such animals.But some people - a growing movement - imagine it every day. Pleistocene rewilding groups believe that in some cases, we should move the benchmark for our habitat restoration from before 1492, to before 11,000 years ago.

Since the megafauna of that age are extinct, they say, and at our hands at that, why not import them from Africa, and South America, and recreate, as best we can, a corridor of North America before man.

Pleistocene rewilders argue that the flora and habitats of North America are designed for the megafauna from which they evolved. The discussion about how to restore habitats should include the case for the pleistocene rewilding. After all, they say, the absence of megafauna creates a domino effect on habitats - the rest of the habitat cannot thrive without them.

In the imagination of the pleistocene rewilders, elephants may roam the mesas, camels (camels in Texas) may roam the canyons, Zebras may roam along the rivers. All of these are approximations of the types of animals that once managed the ecosystem of this region.

To consider such a possibility is fascinating. Something in it smacks of a bit of environmental fundamentalism. Everybody is looking for a pure connection to the past. I'll look to the future however, and I'll await the great debate over how best to restore our habitats with an open ear.

As I leave the cold canyon in the evening, I spot a mouse. Just a tiny one. I don't even glimpse him long enough to identify him.