Even the deeply mourned American chestnut, devastated everywhere after a fungal blight entered New York around in a shipment of Asian nursery plants, still hangs on in the New York Botanical Garden's old forest—literally by its roots. It sprouts, sends up skinny shoots two feet high, gets knocked back by blight, and does it again.
One day, perhaps, with no human stresses sapping its vigor, a resistant strain will finally emerge. Once the tallest hardwood in American eastern forests, the resurrected chestnut trees will have to coexist with robust non-natives that are probably here to stay—Japanese barberry, Oriental bittersweet, and surely ailanthus.
Everyone has something to offer. But botanically, we're xenophobic. We love native species, and want aggressive, exotic plant species to go home. Trim and youthful in his early fifties, Peters has spent much of his life in forests. His field research has revealed that pockets of wild palm nut trees deep in the Amazon, or of durian fruit trees in virgin Borneo, or of tea trees in Burma's jungles, aren't accidents. Once, humans were there, too. As will this one. In fact, it has done so since soon after Homo sapiens appeared here. Eric Sanderson's Mannahatta Project is re-creating the island as the Dutch found it—not some primordial Manhattan forest no human had set foot on, because there wasn't one.
In the clearings grew shrubs of chokecherry, fragrant sumac, rhododendron, honeysuckle, and assorted ferns and flowering plants. Spartina and rose mallow appeared in the salt marshes. As all this foliage filled these warming niches, warm-blooded animals followed, including humans. A dearth of archeological remains suggests that the first New Yorkers probably didn't settle, but camped seasonally to pick berries, chestnuts, and wild grapes.
They hunted turkey, heath hens, ducks, and white-tailed deer, but mainly they fished. The surrounding waters swarmed with smelt, shad, and herring. Brook trout ran in Manhattan streams. Oysters, clams, quahogs, crabs, and lobsters were so abundant that harvesting them was effortless. Large middens of discarded mollusk shells along the shores were the first human structures here.
By the time Henry Hudson first saw the island, upper Harlem and Greenwich Village were grassy savannas, cleared repeatedly with fire by the Lenni Lenape for planting. Much of the island was still as green and dense as the Bialowieza Puszcza. Subsequently, two more made it into town, as well as a wild turkey. The rewilding of New York City may not wait until people leave. Later, he took over the bridges that link Staten Island to the mainland and Long Island.
Del Tufo himself spans an ocean. His olive features bespeak Sicily; his voice is pure urban New Jersey. His bridges are under a constant guerrilla assault by nature. Its arsenal and troops may seem ludicrously puny against steel-plated armor, but to ignore endless, ubiquitous bird droppings that can snag and sprout airborne seeds, and simultaneously dissolve paint, would be fatal.
Del Tufo is up against a primitive, but unrelenting foe whose ultimate strength is its ability to outlast its adversary, and he accepts as a fact that ultimately nature must win. Not on his watch, though, if he can help it. First and foremost, he honors the legacy he and his crew inherited: their bridges were built by a generation of engineers who couldn't possibly have conceived of a third of a million cars crossing them daily—yet 80 years later, they're still in service.
Peter's Cathedral: something this mighty is here forever. Yet Jerry Del Tufo knows exactly how these bridges, without humans to defend to them, would come down. It wouldn't happen immediately, because the most immediate threat will disappear with us. It's not, says Del Tufo, the incessant pounding traffic. The GW alone has enough galvanized steel wire in its three-inch main cables to wrap the Earth four times. Oil, antifreeze, and snowmelt dripping from cars wash salt into catch basins and crevices where maintenance crews must find and flush it.
With no more people, there won't be salt. There will, however, be rust, and quite a bit of it, when no one is painting the bridges. At first, oxidation forms a coating on steel plate, twice as thick or more as the metal itself, which slows the pace of chemical attack. For steel to completely rust through and fall apart might take centuries, but it won't be necessary to wait that long for New York's bridges to start dropping. The reason is a metallic version of the freeze-thaw drama.
Rather than crack like concrete, steel expands when it warms and contracts when it cools. So that steel bridges can actually get longer in summer, they need expansion joints. In winter, when they shrink, the space inside expansion joints opens wider, and stuff blows in. Wherever it does, there's less room for the bridge to expand when things warm up.
With no one painting bridges, joints fill not only with debris but also with rust, which swells to occupy far more space than the original metal. The concrete could crack where the beam is bolted to the pier. Or, after a few seasons, that bolt could shear off. Eventually, the beam could walk itself right off and fall.
Rust that forms between two steel plates bolted together exerts forces so extreme that either the plates bend or rivets pop, says Del Tufo. Arch bridges like the Bayonne—or the Hell Gate over the East River, made to hold railroads—are the most overbuilt of all. They might hold for the next 1, years, although earthquakes rippling through one of several faults under the coastal plain could shorten that period.
Should any of their sections separate, the Atlantic Ocean would rush in. Until then, more coyotes follow the footsteps of the intrepid ones that managed to reach Central Park. Deer, bear, and finally wolves, which have reentered New England from Canada, arrive in turn. By the time most of its bridges are gone, Manhattan's newer buildings have also been ravaged, as wherever leaks reach their embedded steel reinforcing bars, they rust, expand, and burst the concrete that sheaths them.
Older stone buildings such as Grand Central—especially with no more acid rain to pock their marble—will outlast every shiny modern box. Missing, however, are nearly all fauna adapted to us. Rising water, tides, and salt corrosion have replaced the engineered shoreline, circling New York's five boroughs with estuaries and small beaches. With no dredging, Central Park's ponds and reservoir have been reincarnated as marshes.
Without natural grazers—unless horses used by hansom cabs and by park policemen managed to go feral and breed— Central Park's grass is gone. A maturing forest is in its place, radiating down former streets and invading empty foundations. Coyotes, wolves, red foxes, and bobcats have brought squirrels back into balance with oak trees tough enough to outlast the lead we deposited, and after years, even in a warming climate the oaks, beeches, and moisture-loving species such as ash dominate.
With bridges finally down, tunnels flooded, and Manhattan truly an island again, moose and bears swim a widened Harlem river to feast on the berries that the Lenape once picked. Amid the rubble of Manhattan financial institutions that literally collapsed for good, a few bank vaults stand; the money within, however worthless, is mildewed but safe. Not so the artwork stored in museum vaults, built more for climate control than strength. Without electricity, protection ceases; eventually museum roofs spring leaks, usually starting with their skylights, and their basements fill with standing water.
Ceramics, however, are doing fine, since they're chemically similar to fossils. Unless something falls on them first, they await reburial for the next archaeologist to dig them up. Corrosion has thickened the patina on bronze statues, but hasn't affected their shapes. Even if the Statue of Liberty ends up at the bottom of the harbor, Appelbaum says, its form will remain intact indefinitely, albeit somewhat chemically altered and possibly encased in barnacles. That might be the safest place for it, because at some point thousands of years hence, any stone walls still standing—maybe chunks of St.
Paul's Chapel across from the World Trade Center, built in from Manhattan's own hard schist—must finally fall. Three times in the past , years, glaciers have scraped New York clean. The mature beech-oak-ash-ailanthus forest will be mowed down. Then it was hauled to the dump and returned to the Earth. The next toolmaker to arrive or evolve on this planet might discover and use it, but by then there would be nothing to indicate that it was us who put it there.
The reasons involve continental drift, the Earth's mildly eccentric orbit, its wobbly axis, and swings in atmospheric carbon dioxide. For the last few million years, with the continents basically where we find them today, ice ages have recurred fairly regularly and lasted upwards of , years, with intervening thaws averaging 12, to 28, years.
The last glacier left New York 11, years ago. Many scientists now guess that the current intermission before the next frigid act will last a lot longer, because we've managed to postpone the inevitable by stuffing our atmospheric quilt with extra insulation. Comparisons to ancient bubbles in Antarctic ice cores reveal there's more C 0 floating around today than at any time in the past , years. If people cease to exist tomorrow and we never send another carbon-bearing molecule skyward, what we've already set in motion must still play itself out.
Among the human-crafted artifacts that will last the longest after we're gone is our redesigned atmosphere. He finds he must draw on all those disciplines to describe how humans have turned the atmosphere, biosphere, and the briny deep into something that, until now, only volcanoes and colliding continental plates have been able to achieve.
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Volk is a lanky man with wavy dark hair and eyes that scrunch into crescents when he ponders. Leaning back in his chair, he studies a poster that nearly fills his office bulletin board. It portrays atmosphere and oceans as a single fluid with layers of deepening density. Until about years ago, carbon dioxide from the gaseous part above dissolved into the liquid part below at a steady rate that kept the world at equilibrium.
Now, with atmospheric C 0 levels so high, the ocean needs to readjust. But because it's so big, he says, that takes time. As it saturates, that slows. It loses some C 0 to photosynthesizing organisms. So is the land, where excess carbon will cycle through soil and life-forms that absorb but eventually release it. So where can it go? At the bottom, the lid is slightly open—to volcanoes.
But it's much longer. Carbonic acid dissolves soil and minerals that release calcium to groundwater. Rivers carry this to the sea, where it precipitates out as seashells. That will take about , years. Another is that the more oceans warm, the less C 0 they absorb, as higher temperatures inhibit growth of C0 -breathing plankton. Still, Volk believes, with us gone the oceans' initial 1,year turnover could absorb as much as 90 percent of the excess carbon dioxide, leaving the atmosphere with only about 10 to 20 extra parts per million of C 0 above the ppm preindustrial levels.
During the time that the extra carbon is being slowly sopped up, however, palmettos and magnolias may be repopulating New York City faster than oaks and beeches. In a third, wishful scenario, the two extremes might blunt each other enough to hold temperatures suspended in between.
Depending on exactly how much of it and Antarctica go, Manhattan might become no more than a few islets, one where the Great Hill once rose above Central Park, another an outcropping of schist in Washington Heights. Ice Eden Had humans never evolved, how might the planet have fared?
Or was it inevitable that we did? And if we disappeared, would—or could—we, or something equally complicated, happen again? The Great African Rift Valley is the continuation of a tectonic parting of the ways that began even earlier in what is now Lebanon's Beqaa Valley, then ran south to form the course of the Jordan River and the Dead Sea. Then it widened into the Red Sea, and is now branching down two parallel cleavages through the crust of Africa.
Lake Tanganyika fills the Rift's western fork for miles, making it the longest lake in the world. Just as annual snowfalls preserve a history of climate in glaciers, pollen grains from surrounding foliage settle in the depths of bodies of freshwater, neatly separated into readable layers by dark bands of rainy-season runoff and light seams of dry-season algal blooms. At ancient Lake Tanganyika, the cores reveal more than the identities of plants.
They show how a jungle gradually turned to fire-tolerant, broad-leafed woodland known as miombo, which covers vast swathes of today's Africa. There they planted crops such as finger millet, whose signature also appears. All this and more can be learned from mud recovered with 10 meters of steel pipe lowered on a cable and, aided by a vibrating motor, driven by the force of its own weight into the lake bed—and into , years of pollen layers. A next step, says University of Arizona paleolimnologist Andy Cohen, who heads a research project in Kigoma, Tanzania, on Lake Tanganyika's eastern shore, is a drill rig capable of penetrating a 5million- or even million-year core.
Such a machine would be very expensive, on the order of a small oildrilling barge. But it would be worth it, says Cohen, because this is Earth's longest, richest climate archive. But there's good reason to believe that circulation at the tropics is also involved. We know a lot about climate change at the poles, but not at the heat engine of the planet, where people live. The pollens would be the same that our ancestors inhaled, even broadcast from the same plants they touched and ate, because they, too, emerged from this Rift.
East of Lake Tanganyika in the African Rift's parallel branch, another lake, shallower and saline, evaporated and reappeared various times over the past 2 million years. A stream draining Tanzania's volcanic highlands to the east gradually cut a gorge through those layers meters deep. The gray rubble of Olduvai Gorge, now a semidesert bristling with sisal, eventually yielded hundreds of stone-flake tools and chopper cores made from the underlying basalt. Some of these have been dated to 2 million years ago.
In , 25 miles southwest of Olduvai Gorge, Mary Leakey's team found a trail of footprints frozen in wet ash. They were made by an australopithecine trio, likely parents and a child, walking or fleeing through the rainy aftermath of an eruption of the nearby Sadiman volcano.
Their discovery pushed bipedal hominid existence back beyond 3. From here and from related sites in Kenya and Ethiopia, a pattern emerges of the gestation of the human race. It is now known that we walked on two feet for hundreds of thousands of years before it occurred to us to strike one stone against another to create sharp-edged tools. The dust we breathe here, blown by zephyrs that leave a coating of gray tuff powder on Olduvai's sisals and acacias, contains calcified specks of the very DNA that we carry.
Animal bones in these places—some from hippo, rhino, horse, and elephant species that became extinct as we multiplied; many of them honed by our ancestors into pointed tools and weapons—help us know how the world was just before we emerged from the rest of Mammalia. What they don't show, however, is what might have impelled us to do so. But at Lake Tanganyika, there are some clues. They lead back to the ice. At one time, these dropped through gallery rain forest. Then came miombo woodland. Today, most of the escarpment has no trees at all.
Its slopes have been cleared to plant cassava, with fields so steep that farmers are known to roll off them. An exception is at Gombe Stream, on Lake Tanganyika's eastern Tanzanian coast, the site where primatologist Jane Goodall, a Leakey assistant at Olduvai Gorge, has studied chimpanzees since The national park that surrounds it is Tanzania's smallest—only 52 square miles. Where it opened into woodland and savanna, lions and cape buffalo lived. Although chimps are the most intensely studied primates at Gombe, its rain forest is also home to many olive baboons and several monkey species: vervet, red colobus, red-tailed, and blue.
During , a Ph. Red-tailed monkeys have small black faces, white-spotted noses, white cheeks, and vivid chestnut tails. With different coloring, body size and vocalizations, no one would confuse blue and redtailed monkeys in the field. Yet in Gombe they now apparently mistake one another, because they have begun to interbreed. From the forest floor, she scrapes their feces, in which fragments of intestinal lining attest to a mix of DNA resulting in a new hybrid.
Only she thinks it's something more. Genetics indicate that at some point 3 million to 5 million years ago, two populations of a species that was the common ancestor to these two monkeys became separated. In Gombe, the opposite has apparently occurred. At some point, as new forest filled the barrier that once divided these two species, they found themselves sharing a niche. Or, maybe even with advantage over the parents, because the habitat has changed.
Such as evolve. Something similar may have happened here before. Once, when its Rift was only beginning to form, Africa's tropical forest filled the continent's midriff from the Indian Ocean to the Atlantic. Great apes had already made their appearance, including one that in many ways resembled chimpanzees.
The American physical anthropologist Richard Wrangham has given this undiscovered ape a name: Pan prior. Prior, that is, to Pan troglodytes, today's chimpanzee, but also prior to a great dry spell that overtook Africa about 7 million years ago. What caused this was an ice age advancing from the poles. With much of the world's moisture locked into glaciers that buried Greenland, Scandinavia, Russia, and much of North America, Africa became parched. No ice sheets reached it, although glacial caps formed on volcanoes like Kilimanjaro and Mount Kenya.
But the climatic change that fragmented Africa's forest, more than twice the size of today's Amazon, was due to the same distant white juggernaut that was smashing conifers in its path. That faraway ice sheet stranded populations of African mammals and birds in patches of forest where, over the next few million years, they evolved their separate ways. At least one of them, we know, was driven to try something daring: taking a stroll in a savanna. In southwest Uganda, there's a place where it's possible to see our history reenacted in microcosm.
Chambura Gorge is a narrow ravine that cuts for 10 miles through a deposit of dark brown volcanic ash on the floor of the Rift Valley. For chimpanzees, this oasis is both a refuge and a crucible. Lush as it is, the gorge is barely yards across, its available fruit too limited to satisfy all their dietary needs. So from time to time, brave ones risk climbing up the canopy and leaping to the rim, to the chancy realm of the ground.
With no ladder of branches to help them see over the oat and citronella grasses, they must raise themselves on two feet. They select a tree they calculate they can reach without becoming food themselves. Then, as we also once did, they run for it. Ice retreated. Trees regained their former ground and then some, even covering Iceland.
After more than a million years of walking on two feet, its legs had lengthened and its opposable big toes had shortened. It was losing the ability to dwell in trees, but its sharpened survival skills on the ground had taught it to do so much more. Now we were hominids. Somewhere along the way, as Australopithecus was begetting Homo, we learned not only to follow the fires that opened up savannas that we'd learned to inhabit, but how to make them ourselves.
For some 3 million years more, we were too few to create more than local patchworks of grassland and forests whenever distant ice ages weren't doing it for us. Yet in that time, long before Pan priors most recent descendant, surnamed sapiens, appeared, we must have become numerous enough to again try being pioneers. Or were they losers, temporarily out-competed by tribes of stronger blood cousins for the right to stay in our cradle?
Or were they simply going forth and multiplying, like any beast presented with rich resources, such as grasslands stretching all the way to Asia? Exiles or adventurers, the ones who survived filled Asia Minor and then India.
A land bridge got them through much of Indonesia, but to reach New Australopithecus africanus. And then, 11, years ago, observant Homo sapiens in the Middle East figured out a secret until then known only to select species of insects: how to control food supplies not by destroying plants, but by nurturing them. Because we know the Middle Eastern origin of the wheat and barley they grew, which soon spread southward along the Nile, we can guess that—like shrewd Jacob returning with a cornucopia of gifts to win over his powerful brother, Esau—someone bearing seeds and the knowledge of agriculture returned from there to the African homeland.
So much water was frozen into glaciers that the oceans were feet lower than today. At that same time, other humans who had kept spreading across Asia arrived at the farthest reach of Siberia. For 10, years, it had lain under more than half a mile of ice. But now, enough had receded to reveal an ice-free corridor, in places 30 miles wide. Picking their way around meltwater lakes, they crossed it.
Chambura Gorge and Gombe Stream are atolls in an archipelago that is all that remains of the forest that birthed us. In these forest islands, surrounded by seas of agriculture and settlement, the last of Pan priors other offspring still cling to life as it was when we left to become woodland, savanna, and finally city apes. To the north of the Congo River, our siblings are gorillas and chimpanzees; to the south, bonobos.
But suppose we had stayed—or suppose that, when we were exposed on the savanna, the ancestors of today's lions and hyenas had made short work of us. What, if anything, would have evolved in our place? To stare into the eyes of a chimpanzee in the wild is to glimpse the world had we stayed in the forest. Their thoughts may be obscure, but their intelligence is unmistakable.
Hollywood images mislead, because its trained chimps are all juveniles, as cute as any child. However, they keep growing, sometimes reaching pounds. A wild chimpanzee, who lives in a perpetual state of gymnastics, has perhaps three to four pounds of fat. The rest is muscle. Michael Wilson, the curly-haired young director of field research at Gombe Stream, vouches for their strength.
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He has watched them tear apart and devour red colobus monkeys. Superb hunters, about 80 percent of their attempts are successful kills. These are pretty bright creatures. He's watched chimps over months patiently pick off males of neighboring clans until the territory and the females are theirs. The unavoidable comparisons to human aggression and power struggles became his research specialty.
It's kind of depressing. Michael Wilson, hiking in the rain forest, hears drumbeats that he knows are chimpanzees pounding on buttress roots, signaling each other. He runs after them, up and down Gombe's 13 stream valleys, hurdling morning glory vines and lianas strung across baboon trails, following chimp hoots until, two hours later, he finally catches them at the top of the Rift. Five of them are in a tree at the edge of the woodland, eating the mangoes they love, a fruit that came along with wheat from Arabia. A mile below, Lake Tanganyika flashes in the afternoon sunlight, so vast it holds 20 percent of the world's freshwater and so many endemic fish species that it's known among aquatic biologists as the Galapagos of lakes.
In the opposite direction, past Gombe's boundaries, are farmers who also have rifles, and who are tired of chimps who snatch their oil palm nuts. Other than humans and each other, the chimpanzees have no real predators here. If humans were gone, however, they might not need to. Probably the baboons would take first advantage, radiating out, carrying seeds in their poop, which they'd plant.
Soon you'd have trees sprouting wherever there's suitable habitat. Eventually, the chimps would follow. Until, of course, the ice returns. 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? While the U. 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.
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. That part of their otherwise stunning expedition proved a failure; the most impressive big mammal they cited was the bighorn sheep.
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. Over the next two centuries, paleontologists there and elsewhere would show that many species had in fact died.
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.
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. In , 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. 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. During the time frame that coincided with his sediment samples, starting about 13, 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. There were giant shortfaced 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.
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Giant beavers, as big as today's black bears. 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. 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, years old, but unmistakably a turd. The beast that excreted it was a Shasta ground sloth. This one, however, was the size of a cow. 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.
That was only half the size of a ground sloth in Argentina and Uruguay, which at 13, 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.
The manure pile was five feet high, 10 feet across, and more than 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, years: "It's pretty simple.
When people got out of Africa and Asia and reached other parts of the world, all hell broke loose. 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, years ago, they had been Homo sapiens for at least 50, 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. Both the people and their lithic points are known as Clovis, named for the New Mexico site where they were first discovered. 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.
We'd have 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. One challenge to Paul Martin's theory questions whether Clovis people were actually the first humans to enter the New World.
Goodbye to all this
It is written from the point of view of a science journalist with explanations and testimonies backing his predictions. There is no unifying narrative, cohesive single-chapter overview, or thesis. Weisman's thought experiment pursues two themes: how nature would react to the disappearance of humans and what legacy humans would leave behind. He interviews biologist E. Wilson and visits with members of the Korean Federation for Environmental Movement at the Korean Demilitarized Zone where few humans have penetrated since He profiles soil samples from the past years and extrapolates concentrations of heavy metals and foreign substances into a future without industrial inputs.
Carbon dioxide levels in the atmosphere and implications for climatic change are likewise examined. With material from previous articles, Weisman uses the fate of the Mayan civilization to illustrate the possibility of an entrenched society vanishing and how the natural environment quickly conceals evidence. Weisman finds that their structures crumble as weather does unrepaired damage and other life forms create new habitats.
In Turkey, Weisman contrasts the construction practices of the rapidly growing Istanbul , as typical for large cities in less developed countries, with the underground cities in Cappadocia. Due to a large demand for housing in Istanbul much of it was developed quickly with whatever material was available and could collapse in a major earthquake or other natural disaster.
Weisman uses New York City as a model to outline how an unmaintained urban area would deconstruct. He explains that sewers would clog, underground streams would flood subway corridors, and soils under roads would erode and cave in. From interviews with members of the Wildlife Conservation Society  and the New York Botanical Gardens  Weisman predicts that native vegetation would return, spreading from parks and out-surviving invasive species.
Without humans to provide food and warmth, rats and cockroaches would die off. Weisman explains that a common house would begin to fall apart as water eventually leaks into the roof around the flashings, erodes the wood and rusts the nails, leading to sagging walls and eventual collapse.
After years, all that would be left would be aluminum dishwasher parts, stainless steel cookware, and plastic handles. In space, the Pioneer plaques , the Voyager Golden Record , and radio waves would outlast the Earth itself. Breaking from the theme of the natural environment after humans, Weisman considers what could lead to the sudden, complete demise of humans without serious damage to the built and natural environment.
That scenario, he concludes, is extremely unlikely. While he admits it is a "draconian measure",  he states, "The bottom line is that any species that overstretches its resource base suffers a population crash. Limiting our reproduction would be damn hard, but limiting our consumptive instincts may be even harder. The book was first published on July 10, , as a hardback in the United States by St. The paperback was released in July Pete Garceau designed the cover art for the American release, which one critic said was "a thick layer of sugar-coated sweetness in an effort to not alarm potential readers.
But I'm harmless! No, really! Cover art for the international releases contrast the natural environment with a decaying built environment. Adam Grupper voiced the ten-hour-long, unabridged English language audiobook which was published by Macmillan Audio and BBC Audiobooks , and released simultaneously with the hardcover book.