The World Without Us - Alan Weisman (2007)

Part I

Chapter 5. The Lost Menagerie

I

N A DREAM, you walk outside to find your familiar landscape swarming with fantastic beings. Depending on where you live, there might be deer with antlers thick as tree boughs, or something resembling a live armored tank. There’s a herd of what look like camels—except they have trunks. Furry rhinoceroses, big hairy elephants, and even bigger sloths—sloths?? Wild horses of all sizes and stripe. Panthers with seven-inch fangs and alarmingly tall cheetahs. Wolves, bears, and lions so huge, this must be a nightmare.

A dream, or a congenital memory? This was precisely the world that Homo sapiens stepped into as we spread beyond Africa, all the way to America. Had we never appeared, would those now-missing mammals still be here? If we go, will they be back?

AMONG THE VARIOUS slurs hurled at sitting presidents throughout the history of the United States, the epithet with which Thomas Jefferson’s foes smeared him in 1808 was unique: “Mr. Mammoth.” An embargo that Jefferson slapped on all foreign trade, intended to punish Britain and France for monopolizing shipping lanes, had backfired. While the U.S. economy was collapsing, his opponents sneered, President Jefferson could be found in the East Room of the White House, playing with his fossil collection.

This was true. Jefferson, a passionate naturalist, had been enthralled for years by reports of huge bones strewn around a salt lick in the Kentucky wilderness. Descriptions suggested that they were similar to remains discovered in Siberia of a species of giant elephant, thought by European scientists to be extinct. African slaves had recognized big molars found in the Carolinas as belonging to some kind of elephant, and Jefferson was sure these were the same. In 1796 he received a shipment, supposedly of mammoth bones, from Greenbriar County, Virginia, but a huge claw immediately alerted him that this was something else, possibly some immense breed of lion. Consulting anatomists, he eventually identified it and is credited for the first description of a North America ground sloth, today named Megalonyx jefersoni.

Most exciting to him, though, were testimonies by Indians near the Kentucky salt lick, allegedly corroborated by other tribes farther west, that the tusked behemoth in question still lived in the north. After he became president, he sent Meriwether Lewis to study the Kentucky site on the way to joining William Clark for their historic mission. Jefferson had charged Lewis and Clark not only with traversing the Louisiana Purchase and seeking a northwest river route to the Pacific, but also with finding live mammoths, mastodons, or anything similarly large and unusual.

That part of their otherwise stunning expedition proved a failure; the most impressive big mammal they cited was the bighorn sheep. Jefferson later contented himself with sending Clark back to Kentucky for the mammoth bones that he displayed in the White House, today part of museum collections in the United States and France. He is often credited with founding the science of paleontology, though it was not really his intention. He’d hoped to belie an opinion, espoused by a prominent French scientist, that everything in the New World was inferior to the Old, including its wildlife.

He was also fundamentally mistaken about the meaning of fossil bones: he was convinced that they must belong to a living species, because he didn’t believe that anything ever went extinct. Although often considered America’s quintessential Age of Enlightenment intellectual, Jefferson’s beliefs corresponded to those held by many Deists and Christians of his day: that in a perfect Creation, nothing created was ever intended to disappear.

He articulated this credo, however, as a naturalist: “Such is the economy of nature that no instance can be produced of her having permitted any one race of her animals to become extinct.” It was a wish that imbued many of his writings: he wanted these animals to be alive, wanted to know them. His quest for knowledge led him to found the University of Virginia. Over the next two centuries, paleontologists there and elsewhere would show that many species had in fact died. Charles Darwin would describe how these extinctions were part of nature itself—one variety morphing into the next to meet changing conditions, another losing its niche to a more powerful competitor.

Yet one detail that nagged at Thomas Jefferson and others after him was that the big-mammal remains turning up didn’t seem all that old. These weren’t heavily mineralized fossils embedded in solid layers of rock. Tusks, teeth, and jawbones at places like Kentucky’s Big Bone Lick were still strewn on the ground, or protruding from shallow silt, or on the floor of caves. The big mammals they belonged to couldn’t have been gone that long. What had happened to them?

The Desert Laboratory—originally the Carnegie Desert Botanical Laboratory—was built more than a century ago on Tumamoc Hill, a butte in southern Arizona overlooking what was then one of North America’s finest stands of cactus forest and, beyond that, Tucson. For nearly half the lab’s existence, a tall, broad-shouldered, affable paleoecologist named Paul Martin has been here. During that time the desert below Tumamoc’s saguaro-covered slopes disappeared under a snarl of dwellings and commerce. Today, the Lab’s fine old stone structures occupy what developers now covet as prime view property, which they continually scheme to wrest from its present owner, the University of Arizona. Yet when Paul Martin leans on his cane to gaze out his lab’s screened doorway, his frame of reference for human impact is not merely the past century, but the last 13,000 years—since people came to stay.

In 1956, a year before arriving here, Paul Martin had spent the winter in a Quebec farmhouse, during a postdoctoral fellowship at the University of Montreal. A case of polio contracted while collecting bird specimens in Mexico as a zoology undergraduate had rerouted his research from the field to the laboratory. Holed up in Canada with a microscope, he studied sediment cores from New England lakes that dated back to the end of the last ice age. The samples revealed how, as the climate softened, surrounding vegetation changed from treeless tundra to conifers to temperate deciduous—a progression some suspected led to mastodon extinction.

One snowbound weekend, weary of counting tiny grains of pollen, he opened a taxonomy text and started tallying the number of mammals that had disappeared in North America over the past 65 million years. When he reached the final three millennia of the Pleistocene epoch, which lasted from 1.8 million until 10,000 years ago, he started to notice something odd.

During the time frame that coincided with his sediment samples, starting about 13,000 years ago, an explosion of extinctions had occurred. By the beginning of the next epoch—the Holocene, which continues today—nearly 40 species had disappeared, all of them large terrestrial mammals. Mice, rats, shrews, and other small fur-bearing creatures had emerged unscathed, as had marine mammals. Terrestrial megafauna, however, had taken an enormous, lethal wallop.

Among the missing were a legion of animal kingdom Goliaths: giant armadillos and the even-bigger glyptodonts, resembling armor-plated Volkswagens, with tails that ended in spiked maces. There were giant short-faced bears, nearly double the size of grizzlies and, with extra long limbs, much faster—one theory suggests that giant short-faced bears in Alaska were why Siberian humans hadn’t crossed the Bering Strait much earlier. Giant beavers, as big as today’s black bears. Giant peccaries, which may have been prey to Panthern leo atrox, the American lion that was considerably bigger and swifter than today’s surviving African species. Likewise, the dire wolf, the largest of canines, with a massive set of fangs.

The best-known extinct colossus, the northern woolly mammoth, was only one of many kinds of Proboscidea, including the imperial mammoth, largest of all at 10 tons; the hairless Columbian mammoth, which lived in warmer regions; and, in California’s Channel Islands, a dwarf mammoth no taller than a human—only the collie-sized elephants on Mediterranean islands were smaller. Mammoths were grazing animals, evolved to steppes, grassland, and tundra, unlike their much older relatives, the mastodons, which browsed in woods and forests. Mastodons had been around for 30 million years, and ranged from Mexico to Alaska to Florida—but suddenly they, too, were gone. Three genera of American horses: gone. Multiple varieties of North American camels, tapirs, numerous antlered creatures ranging from dainty pronghorns to the stag moose, which resembled a cross between a moose and an elk but was larger than either, all gone, along with the saber-toothed tiger and the American cheetah (the reason why the sole remaining pronghorn species of antelope is so fleet). All gone. And all pretty much at once. What, Paul Martin wondered, could possibly have caused that?

The following year, he was on Tumamoc Hill, his big frame again perched over a microscope. This time, rather than pollen grains saved from decay by an airtight covering of lake-bottom silt, he was viewing magnified fragments preserved in a moisture-free Grand Canyon cave. Soon after he arrived in Tucson, his new boss at the Desert Lab had handed him an earthen gray lump the approximate size and shape of a softball. It was at least 10,000 years old, but unmistakably a turd. Mummified but not mineralized, it yielded identifiable fibers of grasses and flowering globe mallow. The plentiful juniper pollen Martin found confirmed his subject’s great age: temperatures near the floor of the Grand Canyon have not been cool enough to sustain juniper for eight millennia.

The beast that excreted it was a Shasta ground sloth. Today, the only surviving sloths are two tree-dwelling species found in the Central and South American tropics, small and light enough to quietly inhabit rain forest canopies far from the ground, out of harm’s way. This one, however, was the size of a cow. It walked on its knuckles like another of its surviving relatives, the giant South American anteater, to protect the claws it used to forage and to defend itself. It weighed half a ton, yet it was the smallest of the five sloth species that lumbered around North America, from the Yukon to Florida. The Florida variety, the size of a modern elephant, topped three tons. That was only half the size of a ground sloth in Argentina and Uruguay, which at 13,000 pounds stood taller than the largest mammoth.

A decade would pass before Paul Martin got to visit the opening in the red Grand Canyon sandstone wall above the Colorado River where his first sloth dung ball had been collected. By then, extinct American ground sloths had come to mean much more to him than simply more oversized mammals that had mysteriously toppled into oblivion. The fate of sloths would provide what Martin believed was conclusive proof of a theory forming in his mind as data accumulated like layers of stratified sediment. Inside Rampart Cave was a mound of dung deposited, he and his colleagues concluded, by untold generations of female sloths who took shelter there to give birth. The manure pile was five feet high, 10 feet across, and more than 100 feet long. Martin felt like he’d entered a sacred place.

When vandals set it on fire 10 years later, the fossil dung heap was so enormous that it burned for months. Martin mourned, but by then he had been setting blazes of his own in the paleontology world with his theory of what had wiped out millions of ground sloths, wild pigs, camels, Proboscidea, multiple species of horses—at least 70 entire genera of large mammals throughout the New World, all vanished in a geologic twinkling of about 1,000 years:

“It’s pretty simple. When people got out of Africa and Asia and reached other parts of the world, all hell broke loose.”

Martin’s theory, soon dubbed the Blitzkrieg by its supporters and detractors alike, contended that, starting with Australia about 48,000 years ago, as humans arrived on each new continent they encountered animals that had no reason to suspect that this runty biped was particularly threatening. Too late, they learned otherwise. Even when hominids were still Homo erectus, they had already been mass-producing axes and cleavers in Stone Age factories, such as the one at Olorgesailie, Kenya, discovered a million years later by Mary Leakey. By the time a group of them arrived at the threshold of America 13,000 years ago, they had been Homo sapiens for at least 50,000 years. Using their bigger brains, humans by then had mastered not just the technology of attaching fluted stone points to wooden shafts, but also the atlatl, a handheld wooden lever that enabled them to propel a spear fast and precisely enough to fell dangerously large animals from a relatively safe distance.

The first Americans, Martin believes, were the ones who expertly produced the leaf-shaped flint projectile points found widely throughout North America. Both the people and their lithic points are known as Clovis, named for the New Mexico site where they were first discovered. Radiocarbon dates of organic matter found in Clovis sites have sharpened past estimates, and archaeologists now agree that Clovis people were in America 13,325 years ago. What exactly their presence signifies is, however, still a matter for hot dispute, beginning with Paul Martin’s premise that humans perpetrated the extinctions that killed off three-fourths of America’s late Pleistocene megafauna, a menagerie far richer than Africa’s today.

Litoptern.
Macrauchenia patachonica.
ILLUSTRATION BY CARL BUELL.

Key to Martin’s Blitzkrieg theory is that in at least 14 of those sites, Clovis points were found with mammoth or mastodon skeletons, some stuck between their ribs. “If Homo sapiens had never evolved,” he says, “North America would have three times as many animals over one ton as Africa today.” He ticks off Africa’s current five: “Hippos, elephants, giraffes, two rhinoceroses. We’d have 15. Even more, when we add South America. There were amazing mammals down there. Litopterns that looked like a camel with nostrils on top of their nose rather than on the tip. Or toxodons, one-ton brutes like a cross between a rhino and hippo, but anatomically neither.”

All these existed, the fossil record shows, but not everyone agrees on what happened to them. One challenge to Paul Martin’s theory questions whether Clovis people were actually the first humans to enter the New World. Among the objectors are Native Americans wary of any suggestion that they immigrated, which would undermine their indigenous status; they denounce the idea that their origins trace to a Bering land bridge as an attack on their faith. Even some archaeologists question whether a Bering ice-free corridor really existed, and suggest that the first Americans actually arrived by water, skirting the ice sheet to continue down the Pacific coast. If boats reached Australia from Asia nearly 40 millennia earlier, why not boats between Asia and America?

Still others point to a handful of archaeological sites that supposedly predate Clovis. Archaeologists who excavated the most famous of these, Monte Verde, in southern Chile, believe that humans may have settled there twice: once 1,000 years prior to Clovis, the other time 30,000 years ago. If so, at that time the Bering Strait would likely not have been dry land, meaning an ocean voyage from some direction was involved. Even the Atlantic has been suggested, by archaeologists who think that Clovis techniques for flaking chert resemble paleolithics that developed in France and Spain 10,000 years earlier.

Questions about the validity of Monte Verde’s radiocarbon dates soon cast doubt over initial claims that it proved early human presence in the Americas. Matters were further muddied when most of the peat bog that had preserved Monte Verde’s poles, stakes, spear points, and knotted grasses was bulldozed before other archaeologists could examine the excavation site.

Even if early humans did somehow find their way to Chile before Clovis, argues Paul Martin, their impact was brief, local, and ecologically negligible, like that of the Vikings who colonized Newfoundland before Columbus. “Where are the abundant tools, artifacts, and cave paintings that their contemporaries left all over Europe? Pre-Clovis Americans wouldn’t have met competing human cultures, like the Vikings did. Only animals. So why didn’t they spread?”

The second, more fundamental controversy about Martin’s Blitzkrieg theory, for years the most accepted explanation for the fate the of the New World’s big animals, asks how a few nomadic bands of hunter-gatherers could annihilate tens of millions of large animals. Fourteen kill sites on an entire continent hardly add up to megafaunal genocide.

Nearly half a century later, the debate Paul Martin ignited remains one of science’s greatest flash points. Careers have been built upon proving or attacking his conclusions, fueling a protracted, not-always-polite war waged by archaeologists, geologists, paleontologists, dendro- and radiochronologists, paleoecologists, and biologists. Nevertheless, nearly all are Martin’s friends, and many are his former students.

The leading alternatives they’ve proposed to his overkill theory involve either climate change or disease, and have inevitably come to be known as “over-chill” and “over-ill.” Over-chill, with the greatest number of adherents, is partly a misnomer, because both overheating and overcooling get blamed. In one argument, a sudden temperature reversal at the end of the Pleistocene, just as glaciers were melting away, plunged the world briefly back into the Ice Age and caught millions of vulnerable animals unaware. Others propose the opposite: that rising Holocene temperatures doomed furry species, because they had adapted over thousands of years to frigid conditions.

Over-ill suggests that arriving humans, or creatures that accompanied them, introduced pathogens that nothing alive in the Americas had ever encountered. It may be possible to prove this by analyzing mammoth tissues that will likely be discovered as glaciers continue to thaw. The premise has a grim analog: Most descendants of whoever were the first Americans died horribly in the century following European contact. Only a tiny fraction lost their lives to the point of a Spanish sword; the rest succumbed to Old World germs for which they had no antibodies: smallpox, measles, typhoid, and whooping cough. In Mexico alone, where an estimated 25 million Meso-Americans lived when the Spaniards first appeared, only 1 million remained 100 years later.

Even if disease mutated from humans to mammoths and the other Pleistocene giants, or passed directly from their dogs or livestock, that would still put the blame on Homo sapiens. As for over-chill, Paul Martin replies: “To quote some paleo-climate experts, ‘Climate change is redundant.’ It’s not that the climate doesn’t change, but that it changes so often.”

Ancient European sites show that Homo sapiens and Homo nean-derthalensis both drifted north or south with advancing or receding ice sheets. Megafauna, Martin says, would have done the same. “Large animals are buffered against temperature by their size. And they can migrate long distances—maybe not as far as birds, but compared to a mouse, pretty well. Since mice, pack rats, and other small, warm-blooded creatures survived the Pleistocene extinctions,” he adds, “it’s hard to believe that a sudden climate shift made life intolerable for big mammals.”

Plants, even less mobile than animals, and generally more climatesensitive, also seem to have survived. Among the sloth dung in Rampart and other Grand Canyon caves, Martin and his colleagues encountered ancient pack rat middens layered with thousands of years of vegetation remains. With the possible exception of a single variety of spruce, no species harvested by pack rat or sloth residents of these caves met temperatures extreme enough to spell their extinction.

But the clincher for Martin is the sloths. Within a millennium of the Clovis people’s appearance, every slow, plodding, easy target of a ground sloth was gone—on the continents of North and South America. Yet radiocarbon dates confirm that bones found in caves in Cuba, Haiti, and Puerto Rico belonged to ground sloths still alive 5,000 years later. Their ultimate disappearance coincided with the eventual arrival of humans in the Greater Antilles 8,000 years ago. In the Lesser Antilles, on islands that humans reached even later, like Grenada, the sloth remains are even younger.

“If a change in climate was powerful enough to exterminate ground sloths from Alaska to Patagonia, you’d expect it would also take them out in the West Indies. But that didn’t happen.” This evidence also suggests that the first Americans arrived on the continent on foot, not as seafarers, since it took them five millennia to reach the Caribbean.

On another, far-distant island, is a further hint that, had humans never evolved, Pleistocene megafauna might be around today. During the Ice Age, Wrangel Island, a wedge of rocky tundra in the Arctic Ocean, was connected to Siberia. It was so far north, however, that humans entering Alaska missed it. As warming seas rose in the Holocene, Wrangel was again isolated from the mainland; its population of woolly mammoths, spared but now stranded, was forced to adapt to the limited resources of an island. During the span in which humans went from caves to building great civilizations in Sumer and Peru, Wrangel Island’s mammoths lived on, a dwarf species that lasted 7,000 years longer than mammoths on any continent. They were still alive 4,000 years ago, when Egyptian pharaohs ruled.


Giant ground sloth.
Megatherium americanum.
ILLUSTRATION BY CARL BUELL.

More recent still was the extinction of one of the most astonishing of Pleistocene megafauna: the world’s biggest bird, which also lived on an island humans overlooked. New Zealand’s flightless moa, at 600 pounds, weighed twice as much an ostrich and stood nearly a yard taller. The first humans colonized New Zealand about two centuries before Columbus sailed to America. By the time he did, the last of 11 moa species was all but gone.

To Paul Martin, it’s obvious. “Big animals were the easiest to track. Killing them gave humans the most food, and the most prestige.” Within 100 miles of his Tumamoc Hill laboratory, past the Tucson jumble, are three of the 14 known Clovis kill sites. The richest of them, Murray Springs, strewn with Clovis spear points and dead mammoths, was found by two of Martin’s students, Vance Haynes and Peter Mehringer. Its eroded strata, wrote Haynes, resembled “pages in a book that record the last 50,000 years of Earth history.” Those pages contain obituaries of several extinct North American species: mammoth, horse, camel, lion, giant bison, and dire wolf. Adjacent sites add tapir, and two of the few megafauna that survive today: bear and bison.

Which raises a question: Why did they survive, if humans were slaughtering everything? Why does North America still have grizzlies, buffalo, elk, musk ox, moose, caribou, and puma, but not the other big mammals?

Polar bears, caribou, and musk ox inhabit regions where relatively few humans have ever lived—and those who did found fish and seals to be far easier prey. South of the tundra, where trees resume, live bears and mountain lions, furtive and fleet creatures adept at hiding in forests or among boulders. Others, like Homo sapiens, entered North America around the time that the Pleistocene species departed. Today’s plains buffalo are genetically closer to Poland’s wisent than to the now-extinct giant bison that were killed at Murray Springs. After the giant bison were gone, the plains buffalo population exploded. Likewise, today’s moose came from Eurasia after the American stag moose were extinguished.

Carnivores such as sabre-toothed tigers likely disappeared along with their prey. Some former Pleistocene residents—tapirs, peccaries, jaguars, and llamas—escaped farther south to forested refuges in Mexico, Central America, and beyond. Along with the die-off of the rest, this left huge niches to be filled, and eventually buffalo, elk, and company rushed in to fill them.

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.

______________

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.

Martin’s destination, a few miles shy of there, isn’t subtle at all. The International Wildlife Museum was designed to replicate a French Foreign Legion fort in Africa. It houses the collection of a late millionaire big-game hunter, C. J. McElroy, who still holds many world records, including the world’s biggest mountain sheep—a Mongolian argali—and the biggest jaguar, bagged in Sinaloa, Mexico. The special attractions here include a white rhino, one of 600 animals shot by Teddy Roosevelt during a 1909 African safari.

The museum’s centerpiece is the faithfully reproduced 2,500-square-foot trophy room of McElroy’s Tucson mansion, which bears the taxidermized spoils of a lifelong obsession with killing large mammals. Locally often derided as the “dead animal museum,” for Martin on this night, it’s perfect.

The occasion is the launch of his 2005 book, Twilight of the Mammoths. Just behind his audience rises a phalanx of grizzly and polar bears, frozen forever in mid-attack. Above the podium, its ears extended like gray spinnakers, is the trophy head of an adult African elephant. To either side, every breed of spiral horns found on five continents is represented. Pulling himself from his wheelchair, Martin slowly scans the hundreds of stuffed heads: bongo, nyala, bushbuck, sitatunga, greater and lesser kudu, eland, ibex, Barbary sheep, chamois, impala, gazelle, dik-dik, musk ox, cape buffalo, sable, roan, oryx, waterbuck, and gnu. Hundreds of pairs of glass eyes fail to return his moist blue gaze.

“I can’t imagine a more appropriate setting,” he says, “to describe what amounts to genocide. In my lifetime, millions of people slaughtered in death camps, from Europe’s Holocaust to Darfur, are proof of what our species is capable of. My 50-year career has been absorbed by the extraordinary loss of huge animals whose heads don’t appear on these walls. They were all exterminated, simply because it could be done. The person who put this collection together could have walked straight out of the Pleistocene.”

He and his book conclude with a plea that his accounting of the Pleistocene mega-massacre be a cautionary lesson that stops us from perpetrating another that would be far more devastating. The matter is more complicated than a killer instinct that never relents until another species is gone. It involves acquisitive instincts that also can’t tell when to stop, until something we never intended to harm is fatally deprived of something it needs. We don’t actually have to shoot songbirds to remove them from the sky. Take away enough of their home or sustenance, and they fall dead on their own.