Endgame
Late Pleistocene Extinction and
the Sudden Sunset of Clovis
As quickly as they appeared on the scene, Clovis hunters suddenly disappear from the Earth. Clovis people probably survived, at least some of them, but the iconic projectile point vanishes along with the last fossil records of mammoth and mastodon. Thirty-three other genera (the total number is variously believed to be between 33 and 37) of North American megafauna also died off, about half of them, some scientists believe, within a tiny temporal window of 500 years—between 13,200 and 12,700 years ago.
“Megafauna” generally means adult animals of a hundred pounds or more.
So Clovis hunters show up in Montana 13,100 years ago and less than three centuries later all these magnificent animals are dead. For the first time since emerging from Africa, modern humans participate in a major sudden extinction event (Australian Pleistocene extinction probably also took place on a longer, slower time-frame, climaxing 46,000 to 48,000 years ago). The degree to which people were responsible is debated among a mix of causes including climate changes, introduced diseases and an asteroid impact.
The Late Pleistocene extinctions are one of the great mysteries in human history.
Fierce debates rage around what knocked off the megafauna. To blame it all on Homo sapiens begs the dark question of the nature of the beast: Are we humans the murderous, homicidal brutes so deservedly kicked out of Eden, ready to duke or nuke it out to the end of the Earth or are we at heart the deeply sentient beings we sometimes suspect ourselves to be, capable of tolerance, generosity and the kind of empathy it will require to deal with our own terminal crisis—the irreversible global climate change we likely have already brought upon ourselves?
The crucible of stewing ideas to explain Late Pleistocene extinctions in the America transcends archaeology, paleontology and even science. At bedrock, it is a question of philosophy.
Montana’s great novelist A.B. Guthrie wrote, “Each man kills the thing he loves. No man ever did it more thoroughly than the fur hunters.” He’s talking beaver. Our own mountain men, though not Indians, were about as aboriginal as Europeans would ever get.
The “Rewilding” movement of modern conservationists who want to restore some of the megafauna, such as substituting elephants for mammoth, to North America’s plains, points out that our standard of ecological excellence—the state of America in the discovery year of 1492—actually represents an impoverished landscape, already plundered of its magnificent wildlife 12,800 years ago (later Native Americans also significantly altered the land with fire and agriculture). The sudden disappearance of North America’s large mammals lurks as a metaphor for the way humans regard the earth, the rapaciousness with which we consume and destroy the beauty of nature.
One of the possible answers to the extinctions is a theory called “overkill,” a hypothesis formulated some forty-five years ago. The overkill theory postulates a band of highly skilled hunters bursting out of the ice-free corridor before 13,000 years ago, then radiating out blitzkrieg-style in a widening wave of megafaunal slaughter until they reach the oceans and Central America. The band might have started out with as few as 100 Clovis hunters but the population reproduced rapidly. The prey—mammoth, mastodon, ground sloth, camels and horses—had not been hunted by humans before and were therefore naïve and easy to kill.
Other explanations for the sudden disappearance of the great American megafauna include climate change, diseases introduced by people or their dogs and an asteroid smashing into the Great Lakes region. And there are combinations of these factors to explain the extinctions. Maybe climate and disease started to disrupt animal interactions by fragmenting populations or altering their ecological relationships. The big critters might have already begun their decline and human hunting just added the finishing coup-de-grace.
Many Late Pleistocene extinction arguments, however, tend to favor single theory causes.
As a tapestry for discussion of megafauna extinction, what evidence is available? The Clovis hunters were on the scene from 13,100 to almost 12,800 years ago. Older dates are possible but contested. The commencement of climate warming occurred 14,700 years ago and was interrupted by the sudden chill of the Younger Dryas, the temperature dropping 27 degrees Fahrenheit in Greenland. The date for the onset of the Younger Dryas is 12,880 years ago. It lasted nearly 1,300 years, when the current Holocene epoch begins. These are relatively precise dates from ice cores. The opening of the ice-free corridor dates back to at least 13,300 or 13,500 years (as evidenced by the elk antler foreshaft from the Montana Clovis child burial) and might have eventually provided passage for icy blasts of Arctic air blowing down from Alaska thereby cooling the climate.
More elusive is the timetable of when the megafauna disappeared; the 34 to 37 genera of animals didn’t all die off at the same moment. But a growing body of radiocarbon dates and stratigraphic data seems to be narrowing the time most of the big animals succumbed to a 500-year window. Others think the megafauna were on the way out 1,500 years before Clovis even showed up and the extinction event was spread over several millennia. The most vulnerable animals, then and today, tend to be large ones with low reproductive rates.
Dates for this extinction are approximate, as the fossil record doesn’t necessarily reflect the last surviving members of their taxa; a few mammoths survived until six to four-thousand years ago on islands near the Bering Strait. Some radiocarbon dates suggest the extinction was staggered over time, with horses and camels dying out 200 years before mastodons and mammoths. Yet carefully excavated Clovis sites in southeastern Arizona show that all these animals, along with tapirs, dire wolves and American lions, disappeared from the Earth at the same time, about 12,900 years ago. A black, carbon-rich layer of sediment that dates to just less than 12,900 years ago marks the disappearance of Clovis from the archaeological record. In the southwest, they are called “black mats” and probably correspond to a rise in the water table following a regional drought. Clovis tools and mammoth (and other now-extinct animals) bones appear just below the layer but not within it or above it. Black-mat layers shows up at about 70% of Clovis sites across America. In the Southwest, they are probably caused by algae growth; in the East, organic carbon from increased moisture or burning is more common. All seem synchronous with the abrupt onset of the Younger Dryas (YD) cooling.
The beginning of the YD does indeed sound like a doomsday event: The sudden sunset of Clovis culture, the extinction of three-dozen genera of animals including birds and small mammals. Some authorities think North American human numbers plummeted; at a number of formerly Clovis locations, the fluted blade technology reemerges as a smaller bison-hunting weapon, wielded by a perhaps smaller population of Folsom hunters. Other archaeologists dispute population decline by counting the number of post-Clovis Paleoindian projectile points and sites, which they argue shows that the immediate post-Younger Dryas population remained stable. But at most stratified Clovis sites, the carbon-rich layer seems to be the end of human activity for a long time.
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When polled, archaeologists usually point to a mix of climate change and over-hunting to explain the American extinctions. It’s difficult to isolate climate. After a great deal of discussion, the question—who or what caused the American megafauna extinctions at the end of the Pleistocene—might come down to a belief system.
The quandary: When humans colonize a new island, even a great big one like North America, do the island’s creatures, shortly thereafter, begin to go extinct? Every time and unavoidably? Good books are written about island biogeography and most of the evidence points in the direction of the two-legged predator. But the deal is not quite sealed. The question I often ask myself is if I think the great American Pleistocene animals would have gone extinct without the effects of changing climates (I also wonder if the Clovis phenomenon could have ever taken place without our continental warming)? After all, a number of climate reversals came and went and only the last one saw a massive extinction, the difference being human hunters on the scene.
The reasoning, at least mine, is circular: the Allerød warming of 14,700 years ago perhaps unleashed the beginning of a human invasion, which climaxed with Clovis. But the warming didn’t directly kill off the megafauna. The Younger Dryas cooling at 12,880 years marks both the functional end of Clovis and the megafauna, but this return to a cold climate should have been weather to which the American megafauna was already adapted. Clovis, as manifested by its lithic technology, disappeared because there were no more very large mammals left to hunt: Or because they knocked off the last mammoths? It’s a snake eating its tail.
Some things don’t add up. Did the short-faced bear impede settlement of North America prior to Clovis? If so, did its population decline prior to Clovis? And if they did so, what caused the bear population to plummet? No doubt because of a lack of available prey and the carcasses of herbivores, which, again, could be due to climate change, habitat fragmentation and/or hunting pressure. Any time you knock a top-predator out of an ecosystem, cascading chaotic destabilization results; we don’t begin to understand how these removals might have affected the Late Pleistocene habitats. Why did the Clovis colonization succeed so expansively whereas the pre-Clovis occupation apparently just sizzled in place? Was it the Clovis tool kit, dogs and their hunting techniques or the absence of Pleistocene bears and lions that paved the way? There’s plenty of residual confusion here and the best available evidence doesn’t quite solve the problem.
Paleo-extinction is still a formidable mystery.
The discussion is more challenging.
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Why hunt the biggest animals? A mammoth is a lot of meat and outweighs a puny human by a hundred times. Bringing down a great big one means prestige, a feast, a party and maybe reproductive opportunities. Pursuit of mammoth herds fits the leapfrog notion of Clovis colonization: Theory has it that the Bølling-Allerød warming period at the end of the Ice Age fragmented the remaining mammoth populations into oasis-like pockets of habitat, which made them vulnerable to hunters. Kill sites for the horse, ground sloth or camel have not been found (Clovis tools from a cache found in 2008 near Boulder, Colorado tested positive for horse and camel protein residue) but mammoth bones, as opposed to smaller mammals, are more often recognized as something exotic due to their massive size and the big fossils are probably more resistant to erosion, thus more often preserved intact.
It’s argued that these kill sites demonstrate that Clovis people were for the most part the fast moving adventurous elephant hunters out-of-Alaska. In a few productive ecological niches near the end of the southern extension of non-desert habitat (where they may have run out of easily hunted big game), Clovis people found good foraging habitat and chert quarries, where they could settle down and live like generalized hunters and gatherers. In short, the fact that a few sites indicate a generalized subsistence pattern of living doesn’t refute the idea that, elsewhere, highly mobile Clovis hunters were chasing diminishing herds of big game. The size of the Clovis population, its growth and genetic diversity remains elusive, despite mind-boggling models.
Some of those models imply that Clovis hunters, armed with their signature weapon, followed their preferred prey, the mammoth, from one valley to the next, perhaps leap-frogging between mammoth refugia, which might explain the explosive nature of their colonization. Detailed knowledge of local plants and landscapes were unnecessary. Regional variations of the classic Clovis point didn’t appear because the entire band picked up and left in pursuit of the next herd of big mammals. High quality lithic materials from quarries were important. They camped in the open, and didn’t use caves much. As game ran out and the band was subjected to stress, the theory goes, they could choose between changing territories and switching resources. Instead of taking the time to learn about available new food resources, they just moved on.
One should step back before brushing off human-overkill to explain the end of the Pleistocene extinctions. Severe climate shifts had taken place several times in the Americas without any noticeable megafauna die off. The climate was even hotter, with higher seas, during the interglacial period 125,000 years ago. The difference during Clovis times: Homo sapiens were on the scene.
After Clovis and the extinctions of the huge animals, the fluted blade tradition lingered as a smaller, finer bison-hunting tool (Folsom). Big game hunting persisted, especially in the West for a couple thousand years and then, nearly everywhere, people seem to have settled down and lived as generalized hunters and gatherers until agriculture arrived.
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Humans, or their dogs, coming from Asia could have introduced viral diseases that might have jumped species boundaries and infected the American animal populations. The viral diseases AIDS (HIV), SARS and the “Spanish” flu of 1918 jumped from animals to humans; maybe the reverse took place. Zoonotic diseases can be bacterial, such as bubonic plague, although the scary ones today tend to be viral and of the RNA variety, which can mutate and adapt rapidly. Cross-species transmission tend to occur when humans and animals are increasingly coming into contact with one another, as they might have during the climatic-induced wildlife movements of the Late Pleistocene or, ever so alarmingly today, with 7 billion humans beginning to flee the consequences of global warming.
One would think, however, in such a broad spectrum of Pleistocene species that went extinct, resistance to specific diseases would preclude wholesale die off. After all, the mostly viral microbes would require a high degree of transmissibility and fairly strong dose of deadly virulence. But again, for such infectious agents to cross the boundaries of so many different species in such a brief time period seems unlikely. The highest population estimates for Clovis people (generous estimates are less than a million hunter/gatherers; more cautious guesses place Clovis numbers at around 50,000), and their dogs, still paint a stark landscape where interactions between humans and animals were extremely limited—compared to our surging two-legged hordes spilling into our last 21st century wildlife habitats.
If such a plague unfolded 13,000 years ago, the evidence would be hard to find. You would need fossil DNA from extinct animals, and then attempt to identify the DNA or RNA of a pathological virus amid that of the host. Modern molecular genetic techniques can sometimes do this sort of thing but I understand you need to know what you are looking for, and we don’t.
An extinction-causing “Comet Impact Theory” was introduced to the public in 2007, proposing that an extraterrestrial impact, probably a comet or asteroid, exploded in the atmosphere somewhere over Canada north of the Great Lakes 12,900 years ago. No crater has been found (the ice-sheet could have absorbed the blast), but the team believes the products (micro-meteorites, elevated iridium levels and nano-diamonds) found in black mats across the country indicate an impact event and associated widespread burning away from the ice-sheets. Others say these are ordinary components of cosmic dust steadily raining down on Earth and samples provided by the team for radiocarbon dating were found to be contaminated. Whether this theoretical impact could have been solely responsible for the abrupt cooling event or merely a regional contributor to the Younger Dryas is another question.
In 2012, the same scientists expanded their search and found melt-glass materials in Pennsylvania, South Carolina and Syria, which they believe resulted from a large cosmic body impacting the Earth’s atmosphere.
Many authorities doubt the impact theory altogether: A recent study demonstrated that black (charcoal) mats simply mean global weather changes. The same markers may simply indicate a wetland environment. Wildfires occur with each episode of climate change. In the case of the onset of the Younger Dryas, no comet is necessary to explain widespread burning; the sudden cooling killed off vast pine forests, providing sufficient fuel (before the pine needles fell off) to account for lightning torched large-scale fires and the concentration of charcoal particles.
At any rate, the impact, if it indeed occurred, didn’t by itself cause the extinction of the Pleistocene megafauna, which some think had already been in decline for 2,000 years. Sloth survived the theoretical impact in Caribbean islands, mammoth endured in Alaska, the South American megafauna was still going strong 12,500 years ago and grizzlies and buffalo are still here.
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What information could be drawn from these events? Clovis culture blossomed in a time of global warming, rising oceans and melting ice. Mid-North America was prime wildlife territory for fast-moving big game hunters. All this ended suddenly 12,880 years ago with the severe cooling of the Younger Dryas. Scientists like to point out that nearly every animal over 220 pounds died off and only animals weighing less than that survived this extinction. A notable exception was the grizzly (along with modern bison, moose, elk, caribou, musk ox, polar bear and chunky humans).
Why did some large mammals survive while the other megafauna disappeared close to the Younger Dryas cooling? Grizzlies are relatively recent arrivals to North America, having crossed over from Siberia some 50,000 to 70,000 years ago. The omnivorous bears evolved alongside humans. Elk and modern moose are even more recent immigrants; they show up in Beringia about the same time as the earliest pre-Clovis dates and thus knew humans as formidable predators. As a hunted species, elk may have gained a slight advantage as prey animals. Bison and caribou might have survived because of their vast numbers and musk ox and polar bear tends to live in cold, remote habitats.
Grizzlies are generalized omnivores, much like humans. The paleontological literature mentions a few 13,000-year-old brown bear fossils from the lower-48; if these specimens still exist, isotopic analysis on bear bone might indicate what they were eating before and after the time of the “black mat” formation giving us a hint of what daily life was like during this extreme climatic event.
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Mushrooms are fruiting bodies of fungi, which are neither plant nor animal. When you kick a mature mushroom or puffball, the little cloud of dust you see consists of millions of spores. The abundance of dung fungus, Sporormeilla spp., spores has been proposed as a proxy for the presence or absence of the large Pleistocene herbivores—the fungus indicates megafauna. Dung fungus refers to the kind of fungus that must pass through an animal’s digestive tract to complete its life cycle. The microscopic spores of fungus are then picked up by winds and deposited on lakes, where they sink to the bottom. Thus, scientists have studied sediment core samples from lakes in New York, the West and Indiana. Some twenty species of Sporormeilla are hosted in the feces of mammals, birds and probably other creatures. But mostly, these scientists think, in mammal shit. Recent waterholes grazed by modern cattle have been studied for comparison and, yes, the relative abundance of Sporormeilla does indicate when cows were present.
The results from the eastern lakes, contrasted to the western sediment cores, are not identical. In California and Colorado, the frequency of dung fungus falls off sharply at about 12,800 years ago. This would be the expected result just before or at the extinction of big mammals at the time of the Younger Dryas onset. An increase of charcoal particles, indicating ancient wildfires, follows this spore decline.
The New York lake sediment cores, however, show Sporormeilla declining about 14,500 years ago, some 1,400 years before Clovis people show up in the archaeological record. After the disappearance of the megafauna (as represented by the spore decline), the pollen samples indicate that the vegetation underwent change, perhaps because the megafauna wasn’t around to put grazing pressure on the land, chewing and altering it into communities for which there are no modern analogs. The spore decline is followed by charcoal, more evidence of burning.
Much the same pattern is claimed for the cores taken from a kettle pond, Appleman Lake, in Indiana. The Sporormeilla spore frequencies are treated as an absolute proxy for the herbivore megafauna and its local abundance, it is suggested, represents North America. The first decline in Sporormeilla spores begins 14,800 years ago and continues to a final decline a thousand years later, when the spore-to-pollen ratio dropped below 2 percent, signaling a disappearance of the large herbivores from the area. These results are argued by the involved scientists as a collapse or local extinction event, unrelated to any comet/asteroid-impact theory and probably unrelated to climate change. As the authors state: “Megafaunal populations collapsed from 14,800 to 13,700 years ago, well before the final extinctions and during the Bølling-Allerød warming period. Human impacts remain plausible, but the decline predates Younger Dryas cooling and the extraterrestrial impact event proposed to have occurred 12,900 years ago.”
So, what caused the decline? We are left, the scientists say, with humans coming into the lower states 1,500 years before Clovis, hunting the megafauna towards extinction and setting fire to the landscape. Of course, there is no solid archaeology to support the presence or activities of such effective hunters. Similar interpretations are made for the New York record: An initial blitzkrieg-like hunting spree 14,500 years ago, they argue, precipitating a sharp decline in the megafauna followed by a buildup of non-grazed fuel with subsequent burning.
What comes to mind is that these events, as interpreted from Sporormeilla spore frequencies as a proxy for the presence or absence of the megafauna, may represent very local occurrences. The steep decline of dung fungus spores might just mean the herds of megafauna simply moved away to another region or habitat. In comparison studies of present day cattle/Sporormeilla relationships, the amount of spores you recover depend on how far from the shore of the lake or pond you are; the highest densities of Sporormeilla occur next to the bank, not in the middle of the pond. The scientists’ broad interpretations overrun the confined evidence. The fossil record should reflect this abrupt decline to confirm these conclusions. If you could sample a hundred or a thousand lakes across North America, some very interesting patterns might emerge.
Canadian paleontologists have found evidence that, just prior to the Holocene, mammoth and horse dominated the Late Pleistocene landscape in central Alberta. Perhaps these now-extinct mammals returned north to beat the heat.
The initial dates for estimates of Sporormeilla declines in New York and Indiana, 14,500 and 14,800 years ago, are very close to the beginning of the Bølling-Allerød global warming event at 14,700 years ago. Climate change could have influenced vegetation types and megafauna distribution in patterns for which we have yet to find evidence, triggering the herds to migrate and leave the area.
Climate warming, at 14,700 years ago, may have also accommodated the movement of human hunters throughout the continent, beginning a chain of environmental changes, nudged along by big game hunting during a time of weather upheavals. Thus we have the scarce and scattered pre-Clovis “hunters.” It’s one thing to accept that a few people made it south of the glaciers before Clovis, but quite a stretch to think there were enough of them to directly contribute to an overkill of the megafauna.
In New York, the mastodons lasted until 13,000 years ago, by direct dating on bone; they didn’t go out 14,500 years ago, or 13,700 years ago, as the fungal-spore-data indicated. The huge grazers of the Late Pleistocene routinely chewed the habitat into a relatively fireproof landscape, but when they departed, became extinct or migrated, fuel accumulated. Lightning struck and grass and forest fires scorched the land. The presence of humans to set the fires is not required to explain all the charcoal in the sediment layers, although early hunters might have torched a few blazes on their own.
What the heavily extrapolated Sporormeilla dates from Indiana might mean, rather than representing the entire continent, is that it was a time of climatic flux in grassland habitats and the great herds were moving around a lot.
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One last note on extinction theories: A very recent study on the tooth wear of Pleistocene lions and sabertooth cats mired in the La Brea tar pits indicated there wasn’t much change in dietary habits of these predators at the end of the Pleistocene. To the scientists, this means carnivore life was no tougher or more difficult than before humans showed up; declining number of prey was not a primary cause of extinction for these large cats. When prey resources are limited (due to human hunting or climate change), the assumption is that carnivores consume carcasses more completely, chewing up the bones and breaking or leaving distinctive wear-marks on their teeth. Another assumption of the study is that specimen percent-abundance is a proxy for social behavior—that the 80 mostly male, large cranium American lions were less social than the 2,000 sabertooth cats. Another prominent American archeologist has alternatively suggested that Smilodon fatalis may not have been especially bright, as the sabertooth was the second most frequently trapped carnivore (4,000 dire wolves) in the La Brea tar pits.
At bottom, this study is an argument against human overkill or climate change decreasing predator opportunities in southern California during the Late Pleistocene—because there is no evidence of increased “carcass utilization” by the big cats at La Brea. Another explanation is that, with so many dire wolves and a few short-faced bears around, these cats never had a chance to finish off the carcass of their prey. Modern wolf packs and grizzly bears routinely drive mountain lions from their deer and elk kills before the cougar finishes its meal. No sabertoothed cat, which most believe to have been a lonely hunter, could stand up to a short-faced bear or a pack of dire wolves. The American lion was a relatively rare visitor to the tar pits and the sex-structure (2/3 male) might indicate these were wandering, solitary animals. Increased carcass utilization might have been impossible due to competition with those scavengers. La Brea is a spectacular and perhaps unique death trap.
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In conclusion, the question of the Late Pleistocene extinction of the megafauna begs the entire quandary of the peopling of the Americas.
Climate certainly paves the way for the two-legged creatures (we assume Asian origins). The hardest evidence points to virtually no humans getting south into the lower-48 until the global warming of about 15,000 years ago. Northwest glaciers begin to melt and a coastal route using boats opens along the Pacific. At about the same time, the earliest credible American sites show up. Those few humans, the pre-Clovis people, made little discernible impact on the land or its wildlife: These dozen or so scattered sites indicate a transient people using a nondescript tool kit of small artifacts. There is no evidence they thrived as a culture or population. The climate continues to warm between 14,700 and 12,900 years ago. The impact on the flora and fauna is unknown but shifts in vegetation distribution and habitat fragmentation are expected. Likely the megafauna, those herds of herbivores, migrated widely throughout the changing landscape, their predators close behind. Food stress might be a factor.
The continental ice sheets continue to recede opening a corridor through the ice from eastern Beringia southward to the Rocky Mountain Front of Alberta and northern Montana. By 13,300 years ago, the ice-free corridor is sufficiently revegetated to allow elk to come down from Alaska. Humans, with their dogs, pemmican and waterfowl hunting skills, could have used the same passage earlier than the elk. But there is no sign of such a migration until the time of Clovis, about 13,100 years ago. Why the delay in using the corridor and what kept the earlier pre-Clovis people from flourishing? The presence and abundance of Late Pleistocene predators and carnivores, especially the short-faced bear, are worthy suspects.
Suddenly, Clovis people pop up. Probably out of the corridor but perhaps from elsewhere else. Someone invents or imports the massive, deadly Clovis projectile point and all hunting hell breaks loose. Mammoth show up on the menu. If Clovis people came down through the ice-free corridor, they first encountered mammoth in southern Alberta and probably invented the Clovis point at one of the lithic quarries south of the Missouri River in Montana. A few authorities believe that a separate non-Clovis big-game hunting kit was developed at the same time in the far West. The killing of megafauna begins (some think merely continues) and within two-hundred years the feared Clovis points are found south of the ice at the far corners of North America, some of these fluted blades scattered among or imbedded in the bones of extinct mammals.
About thirty-five genera of mammals disappear from America, about half of them in a brief window of 500 years, 13,200 to 12,700 years ago, with Clovis hunters occupying the core of that time period. A sudden cooling, the Younger Dryas, descends on the Earth by 12,880 years ago, marking the terminal appearance of many of these animals. Suspected causes of the YD are still contentious. But it signals the end of Clovis and much of the megafauna. Thirteen hundred years later, it warms, the Holocene begins and the world is changed. Agriculture sprouts and for the next 12,000 years we coast along the stable climatic highway that brings us all the way to the towering fiery crisis of today.
Though the jury is still out, the rap doesn’t look good for Homo sapiens. Certainly, a chain of ecological events could have been set off by climate change and by early Americans killing off a few mammoth or sloth, which in turn started a cascading series of destructive habitat changes, even ecosystem collapse, that led to the decline of the megafauna. If hunters remove just 4 or 5% of a population of slow-reproducing wildlife, those animals are on a road headed toward extinction. But, if the causative conditions of gradual decline existed, they’re hard to document. It doesn’t seem to matter if the extinct animals were browsers, grazers or carnivores (the extinction of predators dependent on declining prey is a simple relationship); they all went down. Some evidence indicates that mammoth herds were expanding their range during this time. This time frame suggests that Clovis hunters had the most blood on their hands. There is little evidence that the small population of pre-Clovis people hunted big animals.
I wish I could find a more satisfying explanation. When I began this book, I thought the evidence leaned towards climate change as the primary cause of the extinction of these magnificent animals, with humans—still a necessary component—merely delivering the coup-de-grace. Hunters certainly didn’t knock off all the megafauna animal by animal. And the Younger Dryas is troublesome and suspect: At sites in Arizona, sloth, tapirs, mammoth, horses, mastodons, camels, dire wolves, lions and short-faced bears disappear at the black-mat boundary. Elsewhere in North America, the moment of extinction is less precise. But 17 genera of wildlife get rubbed out in the last days of the Pleistocene, most all in that lethal moment 13,000 to 12,700 years ago. Extinction dates that fit this cluster are still coming in.
The one unmistakable lesson of Late Pleistocene extinction is that human activity combined with global warming is a potential, ageless, deadly blueprint for ecological disaster.
These two phenomena are again at our doorstep today. What will we do? Will we recognize the ancient shadow of that sabertoothed cat in our modern shrubbery and forge a brand new line of defense?
A curious and perhaps unproductive observation is that the amount of time the Clovis people impacted the Earth spanned about 250 years. European colonialists achieved a firm toehold across North America somewhere between two and three centuries ago.
That iconic Clovis projectile point—simple, luminous, so skillfully sculpted that some think it was intended for totemic exchanges in religious ceremonies—was the first in a long line of cold, deadly American weapons, as sleek and beautiful as a Patriot missile.
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Today, we face change in a magnitude of global warming that will make the extinctions of the Late Pleistocene seem like small potatoes. Not even the grizzly bear will survive the worst-case scenario for today’s human-induced climate changes. The fate of the two-legged omnivore in the 22nd century is itself up for grabs. Our perception of what urgently lies in our own vital interests for human survival is barely coming into focus. And it appears to be very late in the climate-change game: Scientists believe we are reaching the “tipping” point in global warming (the polar ice caps melt, then the Amazonian rainforest collapses, which leads to a Siberian permafrost thaw, releasing methane that gives us an increased 6 degree Celsius, etc.), where natural systems experience sudden, rapid and irreversible change.
Scientists are constantly playing catch-up when it comes to underestimating the magnitude and consequences of a warming climate; it’s not surprising the public doesn’t seem to get it. Governments have no such excuse: They mandate use of Styrofoam cups not reduction of greenhouse gas emissions. And even if they did act, it may be too late for governmental bailouts and technological fixes. The problem is not simply greenhouse gas concentrations; it’s a way of life whose time is over. Endless growth is impossible in a world of finite resources.
The hardest truth from the hardest thinkers is that we must walk away from 12,000 years of stable climate and 10,000 years of civilization to find a new way of living. Our version of human life on earth is ending and it’s useless to pretend we can hang on to our current lifestyle. We’ll have to give up much of what we consider central to our usual daily lives; I’m not looking forward to it and mostly see severe, global cutting-back as a painful and sometimes ugly process. There are no benign economic solutions and corporations, driven by the myth of continual growth, are unlikely to arrive on the doorstep of social responsibility.
Technology is what has empowered us to bring on devastating climatic changes within a mere 250 years, which under natural cycles would have taken hundreds of thousands of years. (Might we make a similar but much smaller claim for the iconic Clovis projectile point contributing to the demise of the megafauna on an identical timetable?) Despite misplaced hope for global sunshades and other temporary fixes to buy some time, high technology will not bail us out of this one.
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Will we be left with James Lovelock’s predictions? What would be your emotional capacity to endure if you were the only survivor of a family of seven? Six-billion people, Lovelock says, may die off by the end of this century (it could be earlier), the agricultural lands of Africa, Asia and Europe dry up, urban survivors flee the starving, flooded cities and head northward into the new population centers of the Arctic ruled by brutal warlords. The thugs deny them entry and they head out again, leading their bleating camels through the unbearable heat toward the next hot oasis.
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We may have heard this speech before: “Growth for the sake of growth is the ideology of a cancer cell.”
I thought I buried that kind of talk when three friends and myself tossed Edward Abbey into a beautiful desert grave some 23 years ago, in accordance with his last wishes—illegally of course. Abbey, one of the closest and most influential friends of my life, started telling me this story back in 1968, the year we met, the same year he published his masterpiece, Desert Solitaire.
The beasts stalking the edges of our human world today—nuclear warfare and global warming—were already taking shape in the landscape of Desert Solitaire. Abbey tells a story wrapped around human rapaciousness for uranium mines. At the end of the tale, a child experiences a beautiful hallucination of the living earth, then dies of massive overexposure to radiation—from atomic rays or rays from the sun, a parable of apocalyptic war or approaching climate change? Abbey provides no easy answers, but this much is evident: Just as we grasp our absolute need for the wild beauty of the world, we are losing it. And it is the children who will pay the price.
Ed is clear about what drives this madness: human greed exemplified by too many people living too high on the hog. “The ever-growing economy,” he wrote, “is based on the superstition that we can steal from our children. And without getting caught.” Abbey foretells the collapse of industrial civilization, warning us that we must reduce our industrial footprint before catastrophe does it for us. Time and wind will bury the polluted cities of the Southwest, he warns, “growth for the sake of growth is a cancerous madness.” Out of this wasteland, the boldest of survivors will wander a new wilderness and perhaps get it right the second time.
That was 1968.
Abbey pops up at the end of this book because I made him a promise fifteen years ago (the fact that he was dead does not relieve me of that obligation). Ed’s statement that “wilderness, in America or anywhere else, is the only thing left that is worth saving” parallels this book’s contention that the preservation of wild habitats will be central to our own struggle to survive the climatic upheavals of the 21st century. Abbey’s predictions are now upon us. Ed might suggest we gather up a like-minded tribe of friends and figure out how to live locally and sustainably (a word Abbey would never use): Stash some beans, hide some peanut butter, and bury lots of ammo and a good deer rifle. Maybe several. Above all, we would have to re-learn the skills of our hunter-gatherer ancestors who managed to survive for a couple of hundred thousand years without agricultural and industrial technology.
Most importantly, Ed would tell us to fight like hell, here, right now: It is a patriot’s duty to defend his planet against the corporations and the governments that work for them, who are poisoning the health of this precious, fragile blue orb we live on. For now, get active, eat low on the food chain, walk don’t drive, stay home, get green, unplug—do the small things. And always, fight to protect the wild; wilderness will buy us the kind of time geo-engineering never could or will. But it might be very late in the climate game to plan for transition. The physics of climate change will shrink our options and close many doors to us. And then it will be time for the survivors to re-enter the remnants of wild landscapes from whence we came, that original homeland that carved the human mind at the beginning of our kind’s time, when living was beautiful, vivid and wondrous, dangerous animals riveted our attention.
It’s time to confront our own sabertoothed cat. What will we do? Will we be bold, adaptive, sufficiently opportunistic and adventurous to successfully face the great climatic shifts of the 21st century? The question may appear less argument than allegory but it is far less esoteric than it sounds. Those ancient mammoth hunters found a way to carry on. If only for a while. May we be half as lucky?