DESERT TIME -- A JOURNEY THROUGH THE AMERICAN SOUTHWEST
Chapter 21: bechan
Bechan is a Navajo word meaning big shit, and there is a cave by that name in an obscure canyon in southeastern Utah, and that is what it is full of. Other caves across the Southwest contain some, too, but this one holds nearly three hundred cubic yards of the stuff. It blankets a roomy cave of red Navajo sandstone that is one hundred and seventy-three feet deep, one hundred and three feet wide, up to thirty feet high. Some of the dung boluses are still intact, and they are similar in size and shape to those of an African elephant. They were left by mammoths.
Twelve thousand years ago -- and this is following clues, mind you: dung and hair preserved in this dry cave and others, fossil footprints in lake beds, skeletons preserved in alluvium and tar, radiocarbon dates from bone and boluses, and the behavioral patterns of African elephants, mammoths' close relatives -- twelve thousand years ago a herd of mammoths used the cave as shelter from the sun. Larger than the woolly mammoth of the tundra and northern forests, the matriarchs of this clan stood more than ten feet high at the shoulder. Their tusks were lyrate, incurved. In those days hundreds of thousands of these Columbian mammoths ranged from coast to coast, from north of the Great Lakes to as far south as Florida. They were grazers. Their main feeding grounds were the grass prairies that stretched from Nebraska to Texas, west through New Mexico, Utah, Arizona, southern California, down into the Mexican plateau.
There is other dung in the cave, too. Maybe two kinds of ground sloth rested or bred there between mammoth visits, the Shasta and the big-tongued, most likely; huge plant-eating creatures of open brushy country, slow-moving, solitary. Horses and deer and other hoofed animals used the cave as occasional shelter -- camels, perhaps, mountain deer, brush oxen, stout-legged llamas -- anyway, from goat-sized to the stature of moose. Packrats made their nests in there, too, sheltered from the snow and rain.
Outside the cave a stream ran through the canyon bottom -- there is an ephemeral stream there now but in those days it ran all year and along the stream and its plunge pools were thickets of blue spruce and water birch, elderberries and wild rose, wet meadows of sedge. Flanking the stream were dunes furred with ricegrass, saltbush, clumps of prickly pear. Then as now the packrats hauled in pads of cactus, as well as twigs and bits of everything else, to armor their messy houses. Beyond the dunes and water meadows were gray slopes of sage. The mammoths grazed the sedge meadows and saltbushes and the ricegrass slopes, then they moved on.
All of these plants -- their stems, thorns, twigs, leaves, seeds, sifted from the dung and the packrat middens -- are living species. Some are still growing outside Bechan Cave, others have retreated two or three thousand feet up the mountainsides, or north as far as Idaho; they have shifted ground. It was cooler in those days but not much cooler; wetter, too, but not much wetter.
Now, instead of sagebrush, the slopes above the cave are spotted with blackbrush. Blackbrush is tolerant of drier ground and higher temperatures. The evidence is, that since the mammoths left, the deserts have arrived.
Other things arrived, too. Against one wall of the cave a group of Paiute or Navajo once made a shelter of juniper branches, and left layers of charcoal, chips from stone tools, broken metates. After they left, the packrats added corncobs to their middens.
These people came later; they came much later. The metates and the corn say that these cave visitors were farmers. But the first people who came here to the Southwest eleven thousand years ago were not.
These North American pioneers -- whether they were absolutely the first people or not is in question, but they were the first to leave plentiful hard evidence -- were big-game hunters. Their hunting skills had been honed on the steppes of central Asia. They are known by us as Clovis people. They were named for the site in Clovis, New Mexico, where the assemblage of their campsite tools and artifacts was first recognized as a culture worthy of a name. They are known most of all for the delicate leaf-shaped blades of their projectile points, an inch and a half to five inches long, thin and sharp. They followed their quarry across the swampy ice-free corridor of the Bering land bridge some thirteen thousand years ago, and a millennium or two later they came down here into a country that we could never in our wildest dreams imagine.
Where the deserts lie now there were open steppes of grass and sage. Rivers ran from snowed and forested mountains. Meltwater from retreating glaciers in the Wasatch Front of Utah and the Sierras of California filled desert lake beds, beds that are now flat pans of cracked and crusted salts and silt. There were elk and bison and mule deer and gray wolves and coyotes, as there are now, or were till recently; but they were the least of it. What the hunters saw here was a country of huge beasts: herds of mammoths, herds of giant bison, tapir, capybara, and more herds: several species each of horses, camels, llamas, four-horned pronghorns, deer, oxen, goats. There were ground sloths the size of elephants. There were giant beavers and armadillos. To prey on and scavenge these there were cheetahs, saber-toothed and scimitar-toothed cats, American lions, short-faced bears bigger than grizzlies, giant condors, dire wolves the size of ponies. Now there were Clovis people, too.
Paul S. Martin is an ecologist, and his terrain is the landscape of the past. His area of research is the end of the Pleistocene -- the Pleistocene epoch ended ten thousand years ago; this last ten thousand years is known as the Holocene, or Recent -- so Bechan Cave is his turf, so to speak.
This much is clear: in the final three thousand years of the Pleistocene epoch, three things happened here at once. One: the landscape grew hotter and drier, the glaciers retreated, fast, the deserts crept into the basins and up the foothills. Two: Clovis people arrived in the Southwest. Three: the great animals known as the Pleistocene Megafauna, thirty-three genera of them, disappeared. Paul Martin estimates that the biomass alone of these vanished animals, the sheer weight of them, was seventy-five million tons; roughly the same as all of the domestic livestock and big game now present in North America.
Nowadays Paul Martin is the Acting Director of the Desert Laboratory of the Department of Geosciences at the University of Arizona in Tucson. The lab was founded in 1903 by the Carnegie Institution; it was the first study center to focus on arid lands. From the beginning it took the long view. The desert needs a long view. A saguaro cactus that lives several centuries needs generations of researchers and decades of data to even begin to understand its life cycle, and many desert plants are longer-lived than that: there are creosote bushes whose seeds germinated ten thousand years ago, when the California basins first dried enough to give them a foothold. It takes a long view to understand the contents of Bechan Cave.
One room of the Desert Laboratory is half full of green steel cabinets. These are filled with boxes and bins filled in turn with labeled plastic bags, and they contain the evidence.
There are chunks of fossil packrat midden -- dusty, faintly honeycombed, hard and heavy as rock, black and resinous in cross section, made of packrat garnerings cemented with their feces and urine. Since a packrat rarely goes farther than three hundred feet from its nest and gathers up anything interesting within that: animal bones, twigs, bits of insects, stones, cactus pads, leaves, seeds (some of this for food but much of it to add bulk and protection to its home), these middens are a sampling of the rat's environment. With time, the middens become as dark and glossy as tar. Protected in dry caves for millennia (the oldest fossil midden found was made more than fifty thousand years ago), they can be collected, soaked in water, their contents sorted, identified, carbon-dated. They are collections from the past.
Also in the green cabinets are chunks of Australian stick-rat midden, porcupine midden, too. Plant cell structures are preserved in these even when plant parts have been too finely chewed to be identified by other means, and pollen can be identified as well. There are pieces of dung of the Shasta ground sloth that were found in a cave in Arizona; these look like horse dung, only larger. There are boluses of mammoth dung from Bechan Cave; a large double handful each, brown on the outside, strawy in. There are sloth and camel and horse bones found in Gypsum Cave, Nevada. There's a piece of hair and skin of a ground sloth, found preserved in bat guano in a New Mexican cave. The hide and hair of another ground sloth, a fragment found in South America, is seal-like but very thick; buried in the skin are pebble-shaped bones, dermal bones that served as body armor, though there was plenty of room between them -- at least on the belly of the beast -- to slip a Clovis spear. There are pellets from Harrington's extinct goat, a mountain goat that lived in these mountains as bighorn sheep do now. There are human dung and basket and bone fragments. There's a piece of horse hoof that was found in Rampart Cave, in Arizona; it came from a small horse, burro-sized. Perhaps the carcass of that horse was dragged in there by one of the big cats, one evening in the height of the Wisconsin glacial age, long before the threat of extinction; when simple life and death still ruled the day. The hoof in question was trotting on the plains of Arizona "26,300 years ago, plus or minus 760 years," the label says. Carbon-14 dates are accurate, within a range.
That's just it: the most recent dates of all of the remains of the Pleistocene Megafauna -- all except the human remains -- cluster within a range. Horses evolved in North America north of Mexico, and lived here for a long time. Some crossed to Asia over the land bridge during some pulse of glacial advance: the ancestors of zebras, burros, onagers, the modern horse. But there were half a dozen species ranging here till recent time, from burro-sized to the stature of a thoroughbred. All of these are gone.
The final dates are telling. Horse: 10,370 years ago, give or take 350. Giant beaver: 10,230, give or take 150. Camel: 10,370. American mastodont: 10,395. Mammoth: 10,550. Tapir: 9,400. Fugitive deer: 9,940. Shrub ox: 8,250. Shasta ground sloth: 10,035. I've left out the give-or-takes. The fact is that the last evidence of these animals was left here between fourteen and eight thousand years ago, with the peak of last appearances eleven thousand years ago.
Paul Martin believes that this is no coincidence. The rivers and waterholes were drying out, the ranges of feedstuff were shrinking -- becoming islanded by desert -- but the animals had survived interglacial dry spells before. The arrival of one new predator, one who could stake out a waterhole and wait, who could organize, in fact, might have been the last straw. The animals were climate-stressed, then exposed to a new, unknown, highly efficient predator. They disappeared in a coast-to-coast wave (their extinctions parallel the wave of Clovis migration), went down fast, within centuries, in what Paul calls a "blitzkrieg."
The evidence is convincing. It has convinced him, but not everyone.
Other paleoecologists cite Pleistocene extinctions on other continents,
too; even Africa lost 15 to 20 percent of its species of big
game. Asia lost more, Australia still more. But North America lost
What we think of as having been the animals of the pristine Southwest -- the buffalo and elk, the bighorns, the puma, the gray wolf, the grizzly -- were ragtag remnants of an emptied land.
Holding the little bags of evidence in my hands -- compressed chewed grass stems, terribly dry; a mummified hoof -- I find myself, suddenly, almost in tears. I can almost see them, they're so close, almost here, almost alive in my hands -- shitting is such an intimate live act, and extinction is so final, more final than any death, though just as natural, it turns out.
Paul sits at his desk, leans back in his chair. Long windows look out on the bright landscape of Tumamoc Hill; saguaros and creosote, a scattering of spring wildflowers even in this drought year, but nothing a mammoth would want. Two walls are floor-to-ceiling books and papers, the other two are windowed stone. Several of the books and papers are on the desk and the floor.
"It makes a difference in the way you view the world," he says. There's a pause.
"That there were these extinctions. And so many of them. And that these animals have escaped history," he says.
"They have escaped --" I begin and can't go on, perhaps what I mean is that they have escaped me, but the sentence like so many things hangs there unfinished. Maybe finished enough. Paul nods. Says:
"Escaped. Exactly. Yes."
Peccary and Prickly Pear: A peccary looks misshapen until you realize that its head is what it works (and plays) with. The skull and jaws are massive and the nose is as sensitive as fingertips. Peccaries eat prickly pear, the fruits and the young pads, plus whatever else they can find on or below the ground, both animal and vegetable. They live in families and they're playful and quick and very good to eat, and they can be aggressive, though this one looks sleepy because it is midday: nap time. Their coarse brindled hair helps them to disappear in the shadows of rocks and canyon scrub whenever they want. They live in the Sonoran desert of Arizona and throughout most of Texas.