The World Without Us

As Vance Haynes excavated Murray Springs, he found signs that drought had forced Pleistocene mammals to seek water—a cluster of footprints around one messy hole was clearly an attempt by mammoths to dig a well. There, they would have been easy pickings for hunters. In the layer just above the footprints is a band of black fossilized algae killed in a cold snap cited by many over-chill advocates—except, in paleontology’s equivalent of a smoking gun, the mammoth bones all lie below it, not within it.

Yet one more clue that, had humans never existed, the descendants of these slaughtered mammoths would likely be around today: when their big prey vanished, so did Clovis people and their famous lithic points. With game gone and weather turned cold, perhaps they moved south. But within a matter of years, the Holocene warmed, and successors to the Clovis culture appeared, their smaller spear points tailored to smaller plains bison. An equilibrium of sorts was reached between these “Folsom people” and those remaining animals.

Had these succeeding generations of Americans absorbed a lesson from the gluttony of their ancestors who killed Pleistocene herbivores as if the supply were endless—until it crashed? Perhaps, although the existence of much of the Great Plains themselves is due to fires set by their descendants, the American Indians, both to concentrate game that browse, such as deer, in forest patches, and to create grassland for grazers like buffalo.

Later, as European diseases raced across the continent and nearly extirpated the Indians, the buffalo population surged and spread. They had almost reached Florida when white settlers heading west met them. After nearly all the buffalo were gone, save a few kept as curiosities, the white settlers took advantage of the plains that the Indians’ ancestors had opened, and filled them with cattle.

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From his hilltop laboratory, Paul Martin looks over a desert city that grew along a river, the Santa Cruz, which flowed north from Mexico. Camels, tapirs, native horses, and Columbian mammoths once foraged on its green floodplain. When descendants of the humans who eliminated them settled here, they built huts from mud and branches of riverbank cottonwood and willow—materials that quickly returned to the soil and the river when no longer needed.

With less game, the people learned to cultivate the plants they gathered, and they called the village that evolved Chuk Shon, a name that meant “flowing water.” They mixed harvest chaff with river mud to form bricks, and this practice continued until mud adobes were supplanted by concrete after World War II. Not long after that, the advent of air-conditioning attracted so many people here that the river was sucked dry. They dug wells. When those dried, they dug deeper.

The Santa Cruz River’s desiccated bed is now flanked by Tucson’s civic center, which includes a convention hall whose jumbo concrete-and-steel-beam foundation seems like it should last at least as long as Rome’s Coliseum. The tourists of some distant tomorrow might have a hard time finding it, however, because after today’s thirsty humans are gone from Tucson and from the bloated Mexican border city of Nogales, Sonora, 60 miles south, eventually the Santa Cruz River will rise again. Weather will do what weather does, and from time to time Tucson and Nogales’s dry river will be back in the business of building an alluvial plain. Silt will pour into the basement of the by-then-roofless Tucson Convention Center until it’s buried.

What animals would live atop it is uncertain. Bison are long gone; in a world without people, the cows that replaced them won’t last long without their attendant cowboys to discourage coyotes and mountain lions. The Sonoran pronghorn—a subspecies of that small, speedy Pleistocene relic, the last American antelope—verges on extinction in desert preserves not far from here. Whether there are enough left to replenish the breed before the coyotes finish them off is questionable, but possible.

Paul Martin descends Tumamoc Hill and drives his pickup truck west through a cactus-studded pass into the desert basin below. Before him lie mountains that are sanctuary to some of the last of North America’s wildest creatures, including jaguar, bighorn sheep, and collared peccaries, locally known as javelinas. Many living specimens are on display just ahead at a famous tourist attraction, the Arizona—Sonora Desert Museum, which includes a zoo with subtle, naturally landscaped enclosures.