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First Peoples in a New World
Colonizing Ice Age America
By David J. Meltzer UNIVERSITY OF CALIFORNIA PRESS
Copyright © 2009 the Regents of the University of California
All rights reserved.
ISBN: 978-0-520-94315-5
CHAPTER 1
OVERTURE
It was the final act in the prehistoric settlement of the earth. As we envision it, sometime before 12,500 years ago, a band of hardy Stone Age hunter-gatherers headed east across the vast steppe of northern Asia and Siberia, into the region of what is now the Bering Sea but was then grassy plain. Without realizing they were leaving one hemisphere for another, they slipped across the unmarked border separating the Old World from the New. From there they moved south, skirting past vast glaciers, and one day found themselves in a warmer, greener, and infinitely trackless land no human had ever seen before. It was a world rich in plants and animals that became ever more exotic as they moved south. It was a world where great beasts lumbered past on their way to extinction, where climates were frigidly cold and extraordinarily mild. In this New World, massive ice sheets extended to the far horizons, the Bering Sea was dry land, the Great Lakes had not yet been born, and the ancestral Great Salt Lake was about to die.
They made prehistory, those latter-day Asians who, by jumping continents, became the first Americans. Theirs was a colonization the likes and scale of which was virtually unique in the lifetime of our species, and one that would never be repeated. But they were surely unaware of what they had achieved, at least initially: Alaska looked little different from their Siberian homeland, and there were hardly any barriers separating the two. Even so, that relatively unassuming event, the move eastward from Siberia into Alaska and the turn south that followed, was one of the colonizing triumphs of modern humans, and became one of the great questions and enduring controversies of American archaeology. Those first Americans could little imagine our intense interest in their accomplishment thousands of years later, and would almost certainly be puzzled—if not bemused—at how seemingly inconsequential details of their coming sparked a wide-ranging, bitter, and long-playing controversy, ranking among the greatest in anthropology and entangling many other sciences.
Here are the bare and (mostly) noncontroversial facts of the case. The first Americans came during the Pleistocene or Ice Age, a time when the earth appeared vastly different than it does today. Tilts and wobbles in the earth's spin, axis, and orbit had altered the amount of incoming solar radiation, cooling Northern Hemisphere climates and triggering cycles of worldwide glacial growth. Two immense ice sheets up to three kilometers high, the Laurentide and Cordilleran, expanded to blanket Canada and reach into the northern United States (while smaller glaciers capped the high mountains of western North America).
As the vast ice sheets rose, global sea levels fell approximately 120 meters, since much of the rain and snow that came down over the land froze into glacial ice and failed to return to the oceans. Rivers cut deep to meet seas that were then hundreds of kilometers beyond modern shorelines (Figure 1). Lower ocean levels exposed shallow continental shelf, including that beneath the Bering Sea, thereby forming a land bridge—Beringia—that connected Asia and America (which are today separated by at least ninety kilometers of cold and rough Arctic waters). When Beringia existed, it was possible to walk from Siberia to Alaska. Of course, once people made it to Alaska, those same glaciers presented a formidable barrier to movement further south—depending, that is, on precisely when they arrived in this far corner of the continent.
These ice sheets changed North America's topography, climate, and environment in still more profound ways. It was colder, of course, during the Ice Age, but paradoxically winters across much of the land were warmer. And the jet stream, displaced southward by the continental ice sheets, brought rainfall and freshwater lakes to what is now western desert and plains, while today's Great Lakes were then mere soft spots in bedrock beneath millions of tons of glacial ice grinding slowly overhead.
A whole zoo of giant mammals (megafauna, we call them) soon to become extinct roamed this land. There were multi-ton American elephants—several species of mammoth and the mastodon—ground sloths taller than giraffes and weighing nearly three tons, camels, horses, and two dozen more herbivores including the glyptodont, a slow-moving mammal encased in a turtle-like shell and bearing an uncanny resemblance to a 1966 Volkswagen Beetle—or at least a submersible one with an armored tail. Feeding on these herbivores was a gang of formidable predators: huge lions, saber-toothed cats, and giant bears. All of these mammals were part of richly mixed animal communities of Arctic species that browsed and grazed alongside animals of the forests and plains.
But this was no fixed stage. From 18,000 years ago, at the frigid depths of the most recent glacial episode—the Last Glacial Maximum (LGM) it's called—until 10,000 years ago when the Pleistocene came to an end (and the earth entered the Holocene or Recent geological period), the climate, environment, landscapes, and surrounding seascapes of North America were changing. Many changes happened so slowly as to be imperceptible on a human scale; others possibly were not. Certainly, however, the world of the first Americans was unlike anything experienced by any human being on this continent since.
Once they got to America, these colonists and their descendants lived in utter isolation from their distant kin scattered across the planet. Over the next dozen or so millennia, in both the Old World and the New, agriculture was invented, human populations grew to the millions, cities and empires rose and fell, and yet no humans on either side of the Atlantic or Pacific oceans was aware of the others' existence, let alone knew of their doings.
It would not be until Europeans started venturing west across the Atlantic that humanity's global encircling was finally complete. Peoples of the Old World and the New first encountered one another in a remote corner of northeast Canada around AD 1000. But that initial contact between Norse and American Indians was brief, often violent, and mostly served to thwart the Vikings' colonizing dreams and drive them back to Greenland and Iceland. It had none of the profound, long-term consequences that followed Columbus's splashing ashore on a Caribbean island that October day of 1492.
Europeans, of course, were profoundly puzzled by what they soon realized was far more than a series of islands, but instead a continent and peoples about whom the Bible—then the primary historical source for earth and human history—said absolutely nothing. We can presume Native Americans were just as perplexed by these strange-looking men, but their initial reactions went largely unrecorded by them or contemporary Europeans. Over the next several centuries, Europeans sought to answer questions about who the American Indians were, where they had come from, when they had arrived in the Americas, and by what route. The idea that they must be related to some historically known group—say, the Lost Tribes of Israel—held sway until the mid-nineteenth century, when it became clear that wherever their origins, they had arrived well before any historically recorded moment. The answer would have to be found in the ground in the artifacts, bones, and sites left behind from a far more ancient time.
But how ancient would prove a matter of much dispute. In 1927, and after centuries of speculation and more than fifty years of intense archaeological debate, a discovery at the Folsom site in New Mexico finally demonstrated the first Americans had arrived at least by Ice Age times. The smoking gun?—a distinctive, fluted spear point found embedded between the ribs of an extinct Pleistocene bison. A hunter had killed that Ice Age beast (see Plate 1).
A half-dozen years later, outside the town of Clovis (also in New Mexico), larger, less finely made, and apparently still older fluted spear points than those at Folsom were found—this time alongside the skeletal remains of mammoth. As best matters could then be determined, these were the traces of the most distant ancestors of Native Americans. Paleoindians, they were named, to recognize their great antiquity and their ancestry to American Indians.
But were these the very first Americans, and if so, just when had they arrived? A more precise measure of their antiquity would have to wait on chemist Willard Libby's Nobel Prize-winning development of radiocarbon dating in the 1950s. By the early 1960s, that technique showed that the Folsom occupation was at least 10,800 years old, while Clovis dated to almost 11,500 radiocarbon years before the present (BP). This was relatively new by Old World standards—humans had lived there for millions of years—but it was certainly old by New World standards.
Better still, the Clovis radiocarbon ages apparently affirmed the suspicion this archaeological culture represented the first Americans, for the dates coincided beautifully with the retreat of North America's vast continental glaciers that, it was widely believed, had long obstructed travel to the south and forced any would-be first Americans to cool their heels in Alaska.
As those glaciers retreated, an "ice-free" corridor opened between them (around 12,000 years ago) along the eastern flanks of the Rocky Mountains, forming a passageway for travel into unglaciated, lower-latitude North America. Emerging from the southern end of the corridor onto the northern plains fast on the heels of its opening, the first Americans radiated across the length and breadth of North America with apparently breathtaking speed, spreading Clovis and Clovis-like artifacts across North America within a matter of centuries. Nor did they stop at the border: their descendants evidently continued racing south, arriving in Tierra del Fuego within 1,000 years of leaving Alaska (having developed en route artifacts that were no longer recognizably Clovis). It's an astonishing act of colonization, especially given it took our species more than 100,000 years just to reach the western edge of Beringia.
Indeed, the possibility that Clovis groups traversed North America in what may have been barely 500 years is all the more striking given that North America was then in the midst of geologically rapid climatic and environmental change. Yet, Clovis groups seemingly handled the challenge of adapting to this unfamiliar, ecologically diverse, and changing landscape with ease. Their toolkit, including its signature fluted points, is remarkably uniform across the continent. That lack of variability is taken as testimony to the rapidity of their dispersal (that is, it happened so quickly there was hardly time for new point styles to emerge).
That some of those points were found embedded in the skeletons of mammoth and bison suggested an answer to the question of how Paleoindians had moved so quickly and effortlessly: they were apparently big-game hunters, whose pursuit of now-extinct animals pulled them across the continent. Some took the argument a step further: it was their relentless slaughter that drove the Pleistocene megafauna to extinction.
EARLIER THAN WE THOUGHT?
The idea the first Americans were highly mobile, wide-ranging, big-game hunters, whose arrival was tied to the final rhythms of Pleistocene glaciation, made perfect sense. For a time. But there were always nagging doubts, not least the persistent claims of a pre-Clovis presence in the Americas. As more archaeologists took to the field in the 1960s and 1970s, perhaps driven (more than they might care to admit) by the chance of finding America's oldest site, every field season promised a pre-Clovis contender. Some were heralded with great fanfare: the legendary Louis Leakey, fresh from his triumph at Olduvai Gorge, flew to California to proclaim the Calico site to be middle Pleistocene in age (several hundred thousand years old). Unfortunately, its supposed artifacts—pulled from massive gravel mudflow deposits—proved indistinguishable from the millions of naturally broken stones the site's excavators burrowed through and tossed aside in great piles, still visible on final approach to Los Angeles International airport.
Other pre-Clovis claims were made by lesser mortals, but in all cases the result was the same: a purportedly ancient site burst on the scene with great promise, only to quickly tumble down what I came to call the pre-Clovis credibility decay curve, wherein the more that was learned about a site—for example, that its supposed artifacts were likely naturally flaked stone, or that the dating technique was experimental and unreliable, or that its deposits were so hopelessly mixed that the allegedly ancient artifacts were found alongside discarded beer cans—the fewer the archaeologists there were willing to believe it.
Dozens, even scores of sites failed to withstand critical scrutiny. There were so many false alarms archaeologists grew skeptical, even cynical, about the possibility of pre-Clovis. And we have long memories—it's part of our business, after all. The response may not have been commendable, but it was certainly understandable, particularly in light of the fact that once artifacts are out of the ground, they can never again be seen in their original context. In effect, we "destroy" aspects of our data in the process of recovering it, and because our sites cannot be grown in a petri dish in a lab, replication and confirmation of a controversial claim is no easy task and independent experiments to check results are nigh on impossible (archaeology may not be a 'hard' science, though it can be a difficult one all the same).
Pre-Clovis proponents cried foul, claiming the demands made of their sites and evidence were unfair, their work chronically underfunded, and their task overdemanding. Critics replied with a sneer that those same demands were met easily enough at Africa's and Australia's earliest sites, and perhaps the proponents' eagerness to find pre-Clovis sites marked a basic flaw in the motivational structure of American academia. Bystanders wisely kept their heads down and declared neutrality. Opinion quickly outran and outweighed the meager facts, and in science disagreement moves in quickly to fill the void between fact and opinion. So controversy grew.
All of this was testimony, cynics smirked, that academic battles are so ferocious because the stakes are so low.
The cynics are partly right. Knowing that the first Americans may have arrived 14,250 years ago, as suggested by artifacts deep within Meadowcroft Rockshelter, Pennsylvania, only tells us American prehistory is a couple of thousand years older than we used to think. In the grand scheme of the last 6 million years of human evolutionary history, that hardly matters. People could have arrived in the Americas tens of thousands of years earlier still, and it would not radically alter our understanding of human evolution (though if they came here hundreds of thousands of years ago, the ante is upped considerably—but the odds that happened are vanishingly small).
Nonetheless, there is more here than an academic turf war. Hanging in the balance is an understanding of when, how, how fast, and under what conditions hunter-gatherers can colonize a rich and empty continent; insight into the population and biological history of New World peoples; a gauge of the speed with which the descendants of the first Americans domesticated a cornucopia of plants (some as early as 10,000 years ago) and became the builders of the complex civilizations here when Europeans arrived; a better and more precise calibration of the rates of genetic, linguistic, and skeletal change in populations over that time; and most unexpectedly, a deeper understanding of the often-tragic historical events that unfolded in the wake of the Europeans' arrival on the shores of what they mistakenly, if self-righteously, proclaimed a New World.
As the peopling controversy deepened, support for pre-Clovis got a boost from an unexpected quarter. Starting in the late 1980s, molecular biologists and human geneticists began to piece together histories of modern American Indians from their mitochondrial DNA (which is inherited mother to child) and from DNA in the non-recombining portion of the Y chromosome (inherited father to son). By determining the genetic distance between modern Asians and Native Americans, and assuming that distance marks the time elapsed since they were once part of the same gene pool, geneticists have a molecular clock by which they can reckon the moment the ancestors of these groups split from one another. By some estimates, it was upwards of 40,000 years ago.
(Continues...)
Excerpted from First Peoples in a New World by David J. Meltzer. Copyright © 2009 the Regents of the University of California. Excerpted by permission of UNIVERSITY OF CALIFORNIA PRESS.
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