THE CLOVIS CONSENSUS
Early in 1929, the Smithsonian received a letter from Ridgely Whiteman, a nineteen-year-old in the village of Clovis, New Mexico, near the state border with Texas. Whiteman had graduated from high school the previous summer and planned to make his living as a carpenter and, he hoped, as an artist. Wandering in the basins south of Clovis, he observed what looked like immense bones protruding from the dry, blue-gray clay. Whiteman, who was part Indian, was fascinated by Indian lore and had been following the archaeological excitement in Folsom, two hundred miles to the north. He sent a letter to the Smithsonian, informing the staff that he, too, had found “extinct elephant bones” and that someone there should take a look. Surprisingly, the museum responded. Paleontologist Charles Gilmore took the train to Clovis that summer.
Clovis is at the southern end of the Llano Estacado (the “Staked Plain”), fifty thousand square miles of flat, almost featureless sand and scrub. Whiteman’s bones were in Blackwater Draw, which during the Pleistocene served as a wide, shallow regional drainage channel, a kind of long, slow-moving lake. As the Ice Ages ended, Blackwater Draw slowly dried up. The continuous flow of water turned into isolated ponds. Game animals congregated around the water, and hunters followed them there. By the time of Gilmore’s visit, Blackwater Draw was an arid, almost vegetation-free jumble of sandy drifts and faces of fractured caliche. In one of archaeology’s great missed opportunities, Gilmore walked around the area for an hour, decided that it was of no interest, and took the train back to Washington.
The thumbs-down response stupefied Whiteman, who had already turned up dozens of fossils and artifacts there. On and off, he continued his efforts to attract scholarly interest. In the summer of 1932 a local newspaper reporter put him into contact with Edgar B. Howard, a graduate student at the University of Pennsylvania, who had, one of his assistants later wrote, a “driving mania” to discover a Folsom-like site of his own. Howard had already spent three years combing the Southwest for ancient bones, crawling into rattlesnake caves and taking a pickax to rock faces. Intrigued by Whiteman’s curios, he asked if he could examine them that winter during his down time. Howard took them back to Philadelphia but had no chance to inspect them. A few weeks after his return a construction project near Clovis unearthed more huge bones. Locals gleefully took them away—one bowling-ball-size mammoth molar ended up as a doorstop. After hearing the news, Howard raced back to see what he could salvage. He telegrammed his supervisors on November 16:
EXTENSIVE BONE DEPOSIT AT NEW SITE. MOSTLY BISON, ALSO HORSE & MAMMOTH. SOME EVIDENCE OF HEARTHS ALONG EDGES. WILL TIE UP PERMISSIONS FOR FUTURE WORK.
Howard returned to Clovis in the summer of 1933 and systematically surveyed Blackwater Draw, looking for areas in which, like Folsom, human artifacts and extinct species were mixed together. He quickly found several and set to digging. Once again, the telegrams went out. A parade of dignitaries from the East trooped out to inspect the excavations. Howard worked at Clovis for four years, each time staffing the field crews with a mix of sunburned locals in boots and jeans and well-tailored Ivy League college students on vacation. “One greenhorn was heard upbraiding his Massachusetts friend for not having perceived at once, as did he,” Howard’s chief assistant later recalled, “that the purpose of a [local farmer’s] windmill was for fanning heat-exhausted cattle.” Windmills were not the only surprise in store for the students. The temperature in the digging pits sometimes hit 130°F.
Slowly peeling away the geological layers, Howard’s workers revealed that Blackwater Draw had hosted not one, but two ancient societies. One had left relics just like those at Folsom. Below the dirt strata with these objects, though, was a layer of quite different artifacts: bigger, thicker, and not as beautifully made. This second, earlier culture became known as the Clovis culture.
Because Clovis was so dry, its stratigraphy—the sequence of geological layers—had not been jumbled up by later waterflow, a common archaeological hazard. Because of this unusual clarity and because Howard meticulously documented his work there, even the most skeptical archaeologists quickly accepted the existence and antiquity of the Clovis culture. To trumpet his findings, Howard arranged for the Academy of Natural Sciences, in Philadelphia, to sponsor an international symposium on Early Man. More than four hundred scientists migrated to Philadelphia from Europe, Asia, Africa, and Australia. The symposium featured a full-scale reproduction, fifteen feet wide and thirty-four feet long, complete with actual artifacts and bones, of a particularly profitable section of Howard’s excavation. (Whiteman was not invited; he died in Clovis in 2003 at the age of ninety-one.)
The most prominent speaker in Philadelphia was Aleš Hrdli
ka, then sixty-eight. Hrdlika gave Clovis the ultimate accolade: silence. Before one of the biggest archaeological audiences in history, Hrdlika chose to discuss the skeletal evidence for Indians’ early arrival in the Americas. He listed every new find of old bones in the last two decades, and scoffed at them all. “So far as human skeletal remains are concerned,” he concluded, “there is to this moment no evidence that would justify the assumption of any great, i.e., geological antiquity” for American Indians. Every word Hrdlika said was true—but irrelevant. By focusing on skeletons, he was able to avoid discussing Clovis, the focus of the conference, because Howard had found no skeletons there. *16
Clovis culture had a distinctive set of tools: scrapers, spear-straighteners, hatchetlike choppers, crescent-moon-shaped objects whose function remains unknown. Its hallmark was the “Clovis point,” a four-inch spearhead with a slightly cut-in, concave tail; in silhouette, the points somewhat resemble those goldfish-shaped cocktail crackers. Folsom points, by contrast, are smaller and finer—perhaps two inches long and an eighth of an inch thick—and usually have a less prominent tail. Both types have wide, shallow grooves or channels called “flutes” cut into the two faces of the head. The user apparently laid the tip of the spear shaft in the flute and twisted hide or sinew repeatedly around the assembly to hold it together. When the point broke, inevitable with stone tools, the head could be loosened and slid forward on the shaft, letting the user chip a new point. A paleo-Indian innovation, this type of fluting exists only in the Americas.
Clovis (left) and Folsom points (shown to scale; fluting at bases)
With Blackwater Draw as a pattern, scientists knew exactly what to look for. During the next few decades, they discovered more than eighty large paleo-Indian sites throughout the United States, Mexico, and southern Canada. All of them had either Folsom or Clovis points, which convinced many archaeologists that the Clovis people, the earlier of the two, must have been the original Americans.
Nobody really knew how old the Clovis people were, though, because geological strata can’t be dated precisely. Figgins surmised that Folsom had been inhabited fifteen to twenty thousand years ago, which meant that Clovis must be a little before that. More precise dates did not come in until the 1950s, when Willard F. Libby, a chemist at the University of Chicago, invented carbon dating.
Libby’s research began in the global scientific race during the 1930s and 1940s to understand cosmic rays, the mysterious, ultrahigh-velocity subatomic particles that continually rain onto the earth from outer space. Like so many bullets, the particles slam into air molecules in the upper atmosphere, knocking off fragments that in turn strike other air molecules. Along the way, Libby realized, the cascade of interactions creates a trickle of carbon-14 (C14), a mildly radioactive form of carbon that over time disintegrates—decays, as scientists say—back into a form of nitrogen. Libby determined that the rate at which cosmic rays create C14 is roughly equal to the rate at which it decays. As a result, a small but steady percentage of the carbon in air, sea, and land consists of C14. Plants take in C14 through photosynthesis, herbivores take it in from the plants, and carnivores take it in from them. In consequence, every living cell has a consistent, low level of C14—they are all very slightly radioactive, a phenomenon that Libby first observed empirically.
When people, plants, and animals die, they stop assimilating C14. The C14 already inside their bodies continues to decay, and as a result the percentage of C14 in the dead steadily drops. The rate of decline is known precisely; every 5,730 years, half of the C14 atoms in nonliving substances become regular carbon atoms. By comparing the C14 level in bones and wooden implements to the normal level in living tissues, Libby reasoned, scientists should be able to determine the age of these objects with unheard-of precision. It was as if every living creature had an invisible radioactive clock in its cells.
In 1949 Libby and a collaborator ascertained the C14 level in, among other things, a mummy coffin, a piece of Hittite floor, an Egyptian pharaoh’s funerary boat, and the tomb of Sneferu of Meydum, the first Fourth Dynasty pharaoh. Archaeologists already knew their dates of construction, usually from written records; the scientists wanted to compare their estimates to the known dates. Even though Libby and his collaborator were still learning how to measure C14, their estimates were rarely more than a century off—a level of agreement, they wrote dryly, that was “seen to be satisfactory.”
Libby won a well-deserved Nobel Prize in 1960. By that time, carbon dating was already revolutionizing archaeology. “You read books and find statements that such and such a society or archaeological site is 20,000 years old,” he remarked. “We learned rather abruptly that these numbers, these ancient ages, are not known.” Archaeologists had been making inferences from limited, indirect data. With radiocarbon, these numbers, these ancient ages, could be known, and with ever-increasing accuracy.
One of the first tasks assigned to the new technique was determining the age of the Clovis culture. Much of the work occurred at the University of Arizona, in Tucson, which in 1958 established the world’s first major archaeological carbon-dating laboratory. At the new lab was a doctoral student named C. Vance Haynes. Haynes was a mining engineer who became fascinated by archaeology during a stint in the air force. While serving at a base in the Southwest, he began collecting arrowheads, a hobby that ultimately led to his abandoning geology and coming to the University of Arizona as a graduate student in archaeology. As the Clovis-culture dates crossed his lab bench, Haynes was struck by their consistency. No matter what the location of a site, carbon dating showed that it was occupied between 13,500 and 12,900 years ago. *17 To Haynes, with his geologist’s training, the dates were auspicious. The Clovis culture arose just after the only time period in which migration from Siberia seemed to have been possible.
During the Ice Ages so much of the world’s water was frozen into glaciers that sea levels fell as much as four hundred feet. The strait between Siberia’s Chukotsky Peninsula and Alaska’s Seward Peninsula is now only 56 miles wide and about 120 feet deep, shallower than many lakes. The decline in sea levels let the two peninsulas join up. What had been a frigid expanse of whale habitat became a flat stretch of countryside more than a thousand miles wide. Beringia, as this land is called, was surprisingly temperate, sometimes even warmer than it is today; masses of low flowers covered it every spring. The relative salubriousness of the climate may seem incredible, given that Beringia is on the Arctic Circle and the world was still in the throes of the Ice Ages, but many lines of evidence suggest that it is true. In Siberia and Alaska, for instance, paleoentomologists—scientists who study ancient insects—have discovered in late-Pleistocene sediments fossil beetles and weevils of species that live only in places where summer temperatures reach the fifties.
C. Vance Haynes
Beringia was easily traversable. Western Canada was not, because it was buried beneath two massive, conjoined ice sheets, each thousands of feet deep and two thousand miles long. Even today, crossing a vast, splintered wilderness of ice would be a risky task requiring special vehicles and a big support staff. For whole bands to walk across it with backpacks full of supplies would be effectively impossible. (In any case, why would they want to do it?
There was a short period, though, when the barrier could be avoided—or at least some scientists so believed. The Ice Ages drew to a close about fifteen thousand years ago. As the climate warmed, the glaciers slowly melted and sea levels rose; within three thousand years, Beringia had again disappeared beneath the waves. In the 1950s some geologists concluded that between the beginning of the temperature rise and the resubmergence of the land bridge the inland edges of the two great ice sheets in western Canada shrank, forming a comparatively hospitable pathway between them. This ice-free corridor ran down the Yukon River Valley and along the eastern side of the Canadian Rockies. Even as the Pacific advanced upon Beringia, these geologists said, plant and animal life recolonized the ice-free corridor. And it did so just in time to let paleo-Indians through.
In a crisply argued paper in Science in 1964, Haynes drew attention to the correlation between the birth of “an ice-free, trans-Canadian corridor” and the “abrupt appearance of Clovis artifacts some 700 years later.” Thirteen thousand to fourteen thousand years ago, he suggested, a window in time opened. During this interval—and, for all practical purposes, only during this interval—paleo-Indians could have crossed Beringia, slipped through the ice-free corridor, and descended into southern Alberta, from where they would have been able to spread throughout North America. The implication was that every Indian society in the hemisphere was descended from Clovis. The people at Blackwater Draw were the ancestral culture of the Americas.
Haynes was the first to put together this picture. The reaction, he told me, was “pretty gratifying.” The fractious archaeological community embraced his ideas with rare unanimity; they rapidly became the standard model for the peopling of the Americas. On the popular level, Haynes’s scenario made so much intuitive sense that it rapidly leapt from the pages of Science to high school history textbooks, mine among them. Three years later, in 1967, the picture was augmented with overkill.
If time travelers from today were to visit North America in the late Pleistocene, they would see in the forests and plains an impossible bestiary of lumbering mastodon, armored rhinos, great dire wolves, sabertooth cats, and ten-foot-long glyptodonts like enormous armadillos. Beavers the size of armchairs; turtles that weighed almost as much as cars; sloths able to reach tree branches twenty feet high; huge, flightless, predatory birds like rapacious ostriches—the tally of Pleistocene monsters is long and alluring.
At about the time of Clovis almost every one of these species vanished. So complete was the disaster that most of today’s big American mammals, such as caribou, moose, and brown bear, are immigrants from Asia. The die-off happened amazingly fast, much of it in the few centuries between 11,500 and 10,900 B.C. And when it was complete, naturalist Alfred Russell Wallace wrote, the Americas had become “a zoologically impoverished world, from which all of the hugest, and fiercest, and strangest forms [had] recently disappeared.”
The extinctions permanently changed American landscapes and American history. Before the Pleistocene, the Americas had three species of horse and at least two camels that might have been ridden; other mammals could have been domesticated for meat and milk. Had they survived, the consequences would have been huge. Not only would domesticated animals have changed Indian societies, they might have created new zoonotic diseases. Absent the extinctions, the encounter between Europe and the Americas might have been equally deadly for both sides—a world in whichboth hemispheres experienced catastrophic depopulation.
PALEO-INDIAN MIGRATION ROUTES
North America, 10,000 B.C.
Researchers had previously noted the temporal coincidence between the paleo-Indians’ arrival and the mass extinction, but they didn’t believe that small bands of hunters could wreak such ecological havoc. Paul Martin, a paleontologist who was one of Haynes’s Arizona colleagues, thought otherwise. Extinction, he claimed, was the nigh-inevitable outcome when beasts with no exposure to Homo sapiens suddenly encountered “a new and thoroughly superior predator, a hunter who preferred killing and persisted in killing animals as long as they were available.”
Imagine, Martin said, that an original group of a hundred hunters crossed over Beringia and down the ice-free corridor. Historical records show that frontier populations can increase at astonishing rates; in the early nineteenth century, the annual U.S. birthrate climbed as high as 5 percent. If the first paleo-Indians doubled in number every 20 years (a birthrate of 3.4 percent), the population would hit 10 million in only 340 years, a blink of an eye in geological terms. A million paleo-Indians, Martin argued, could easily form a wave of hunters that would radiate out from the southern end of the ice-free corridor, turning the continent into an abattoir. Even with conservative assumptions about the rate of paleo-Indian expansion, the destructive front would reach the Gulf of Mexico in three to five centuries. Within a thousand years it would strike Tierra del Fuego. In the archaeological record, Martin pointed out, this hurricane of slaughter would be visible only as the near-simultaneous appearance of Clovis artifacts throughout North America—and “the swift extermination of the more conspicuous native American large mammals.” Which, in fact, is exactly what one sees.
Not everyone was convinced by Martin’s model. Paleontologists noted that many non-game species vanished, too, which in their view suggests that the extinction wave was more likely due to the abrupt climatic changes at the end of the Pleistocene; Martin pointed out that previous millennia had experienced equally wild shifts with no extinction spasm. In addition, similar extinctions occurred when human beings first invaded Madagascar, Australia, New Zealand, and the Polynesian Islands.
Despite overkill’s failure to enjoy full acceptance, it helped set in stone what became the paradigmatic image of the first Americans. Highly mobile, scattered in small bands, carnivorous to a fault, the paleo-Indians conjured by archaeologists were, above all, “stout-hearted, daring, and voracious big-game hunters,” in the skeptical summary of Norman Easton, an anthropologist at Yukon College, in Whitehorse. Clovis people were thought to have a special yen for mammoth: great ambulatory meat lockers. Sometimes they herded the hairy creatures en masse into gullies or entangling bogs, driving the animals to their doom with shouts, dogs, torches, and, possibly, shamanic incantations. More often, though, hunters stalked individual beasts until they were close enough to throw a spear in the gut. “Then you just follow them around for a day or two until they keel over from blood loss or infection,” Charles Kay, an ecological archaeologist at Utah State University, told me. “It’s not what we think of as sporting, but it’s very effective and a hell of a lot safer than hand-to-hand combat with a mammoth.”
Shifting location to follow game, the Clovis people prowled roughly circular territories that could have been two hundred miles in diameter (the size would vary depending on the environmental setting). With any luck, the territory would contain flint, jasper, or chalcedony, the raw material for spear points, meat scrapers, and other hunting tools. Bands may have had as many as fifty members, with girls going outside the group to marry. At camp, women and girls made clothes, gathered food—wild plums, blackberries, grapes—and tended babies. Men and boys went hunting, possibly as a group of fathers and sons, probably for days at a time.
As the extinctions proceeded, the Clovis people switched from mammoths to the smaller, more numerous bison. The spear points grew smaller, the hunting more systematic (with prey becoming scarcer, it needed to be). Bands camped on ridges overlooking ponds—the men wanted to spot herds when they came to drink. When the animals plunged their muzzles into the water, hunting parties attacked, forcing the startled bison to flee into a dead-end gully. The beasts bellowed in confusion and pain as the paleo-Indians moved in with jabbing spears. Sometimes they slaughtered a dozen or more at once. Each hunter may have gobbled down as much as ten pounds of bison flesh a day. They came back staggering under the load of meat. Life in this vision of early America was hard but pleasant; in most ways, archaeologists said, it was not that different from life elsewhere on the planet at the time.
Except that it may not have been like that at all.