When Did Humans Come to the Americas?
At the Buttermilk Creek Complex archaeological site north of Austin, Texas, in a layer of earth beneath a known Clovis excavation, researchers led by Waters over the past several years found 15,528 pre-Clovis artifacts—most of them toolmaking chert flakes, but also 56 chert tools. Using optically stimulated luminescence, a technique that analyzes light energy trapped in sediment particles to identify the last time the soil was exposed to sunlight, they found that the oldest artifacts dated to 15,500 years ago—some 2,000 years older than Clovis. The work “confirms the emerging view that people occupied the Americas before Clovis,” the researchers concluded in Science in 2011. In Waters’ view, the people who made the oldest artifacts were experimenting with stone technology that, over time, may have developed further into Clovis-style tools.
Waters recently landed other blows to the Clovis orthodoxy in collaboration with Thomas Stafford, president of the Colorado-based Stafford Research Laboratories. In one series of experiments using accelerator mass spectrometry (AMS), a dating technique that is more precise than earlier radiocarbon measurements, they reanalyzed a mastodon rib from a skeleton previously recovered in Manis, Washington, and found to have a projectile point lodged in it. The original radiocarbon tests had surrounded the discovery in controversy because they showed it to be 13,800 years old—centuries older than Clovis. The new AMS tests confirmed that age estimate date, and DNA analysis showed that the projectile point was mastodon bone.
Deploying AMS technology, Waters and Stafford also retested many known Clovis samples from around the country, some collected decades earlier. The results, Waters said, “blew me away.” Instead of a culture spanning about 700 years, the analysis shrunk the Clovis window to 13,100 to 12,800 years ago. This new time frame required the Siberian hunters to negotiate the ice-free corridor, settle two continents and put the megafauna on the road to extinction within 300 years, an incredible feat. “Not possible,” Waters said. “You’ve got people in South America at the same time as Clovis, and the only way they could have gotten down there that fast is if they transported like ‘Star Trek.’ ”
But Haynes, of the University of Nevada-Reno, disagrees. “Think of a small number of very mobile people covering a lot of ground,” he suggests. “They could have been walking thousands of kilometers per year.”
Goebel, of the Texas A&M Center for the Study of the First Americans, characterizes his attitude toward pre-Clovis finds as “acceptance with reservation.” He said he’s disturbed by “nagging” shortcomings. Each of the older sites appears to be one-of-a-kind, he said, without a “demonstrated pattern across a region.” With Clovis, he adds, it is clear that the original sites were part of something bigger. The absence of a consistent pre-Clovis pattern “is one of the things that has hung up a lot of people, including myself.”
The discovery of numerous artifacts that pre-date Clovis has, over the years, required scholars to come up with different ideas about not only when people arrived in the Americas but how they got here. For instance, if they were already established 14,800 years ago, they must not have used the famed ice-free corridor through North America: Researchers say that it would not appear for another 1,000 years.
Maybe the first Americans didn’t walk here but came in small boats and followed the coastline, some researchers say. That possibility was first suggested in the 1950s with the discovery of Clovis-era human bones—but no artifacts—on Santa Rosa Island in the Santa Barbara Channel off the California coast. Over the past decade, though, a joint University of Oregon-Smithsonian team of archaeologists unearthed dozens of stemmed and barbed projectile points from Santa Rosa and other Channel Islands, along with the remains of fish, shellfish, seabirds and seals. Radiocarbon dates showed much of the organic material was about 12,000 years old, roughly within the Clovis time frame.
The findings do not prove that the continent’s first settlers came by sea, of course. The islands were only about four miles offshore at the time, and could have been visited by people who’d settled on the mainland. Still, the sites establish that these island dwellers were seafarers of a sort and accustomed to a seafood diet.
Jon Erlandson, a University of Oregon archaeologist, and Torben Rick, an anthropologist at the Smithsonian National Museum of Natural History, propose a pre-Clovis “kelp highway” for coast-hugging seamen skirting the southern edge of the Bering land bridge on their way from northeast Asia to the New World. “People came between 15,000 and 16,000 years ago” by sea, and “could eat the same seaweed and seafood as they moved along the coastline in boats,” Erlandson said. “It seems logical.” The notion that ancient people could travel great distances by boat isn’t far-fetched; many anthropologists believe that humans voyaged from the Asian mainland to Australia 45,000 years ago.
Though Erlandson said he’s convinced that the Clovis people were not the first in the Americas, he acknowledged that definitive proof of a pre-Clovis coastal route may never be found: Whatever beach settlements existed in those days of especially low sea level were long ago submerged or swept away by Pacific tides.
Moreover, the Channel Islands projectiles have nothing in common with Clovis points, as Erlandson pointed out. They appear to be related to a different toolmaking approach called the western stemmed tradition; featuring stems of different shapes that attach the projectile points to spears or darts, they were prevalent in the Pacific Northwest and the Great Basin. And they do not have the fluting characteristic of Clovis. Those observations strengthen the view that other tool-making human cultures were present in the Americas at the same time as the Clovis people, and in all likelihood beforehand as well.
The link between the Channel Islands artifacts and the western stemmed tradition recently acquired greater significance: Inside the Paisley Caves in Oregon, scientists excavated similar points that were associated with organic material yielding radiocarbon dates 13,000 years old—contemporary with Clovis.
The University of Oregon’s Dennis L. Jenkins, who led the Paisley excavation, re-examined a site first explored in the 1930s. The earlier documentation (photographs and some film) was insufficient to show a definite association between the bones and artifacts. But soon, he said, “we had artifacts and we had the bones” from the site. To determine if the human artifacts were the same age as the animal remains, the researchers conducted radiocarbon dating tests on human coprolites—petrified feces—extracting carbon residue from the organic material digested long ago. They also analyzed human mitochondrial DNA in the sample, probably shed from the intestinal wall, and determined that it came from a modern human with an apparently Asian genome. The toolmakers had lived 13,000 years ago.
“And there is nothing connecting this to any Clovis site,” Jenkins said. “You have two technologies existing at the same time in North America, and there is no direct immediate relationship.”
To answer critics, Jenkins and his team tested the DNA of project participants, to make sure they had not contaminated the coprolites, and tested the sediments surrounding the coprolites for modern rodent urine and other telltale signs the area had been tainted. They found no evidence of contemporary animal or human DNA.
Jenkins and his colleagues published the final results this year and closed the site: “We’ve gotten to the bottom,” he said. “We’ve convinced the people who are willing to be convinced that the caves are as old as Clovis, if not older.”
Perhaps the most radical scholarly work suggests the Americas were colonized first by immigrants from Europe several thousand years before Clovis. The theory is the brainchild of Dennis Stanford, a curator of North American archaeology at the National Museum of Natural History, and Bruce Bradley, an archaeologist at Britain’s University of Exeter. In their 2012 book Across Atlantic Ice, they suggest that these Europeans reached the New World more than 20,000 years ago, settled in the eastern United States, developed the Clovis technology over several thousand years, then spread across the continent.
This theory is based partly on similarities between Clovis points and finely crafted “laurel leaf” points from Europe’s Solutrean culture, which flourished in southwestern France and northern Spain between 24,000 and 17,000 years ago. Stanford and Bradley argue that artifacts found at Page-Ladson, as well as other pre-Clovis sites, including the Meadowcroft Rock Shelter in western Pennsylvania and the sand dunes of Cactus Hill in southeastern Virginia, have similarities to Solutrean technologies.
The Solutreans, whose territory on the European continent was apparently rather compact, may have been forced by encroaching glaciers and extreme cold to cluster on the Atlantic coast. At some point, Stanford and Bradley say, the stresses of overpopulation may have forced some Solutreans to escape by sea. They headed north and west beneath the Atlantic ice sheet to nudge into North America at the Grand Banks of Newfoundland.
Stanford and Bradley say evidence for the Solutreans’ presence in America includes stone artifacts gathered by archaeologists at several sites on the eastern shore of Chesapeake Bay, all producing dates more than 20,000 years old. Most of the dates were derived from organic material found with the artifacts. The exception was a mastodon tusk with attached bone and teeth netted by a fisherman in 1974, along with a laurel leaf-shaped stone knife. Stanford found the tusk to be 22,760 years old. Among other things, the Solutrean hypothesis provides context not only for the Clovis people, but also for North America’s pre-Clovis sites. And it does not rule out Bering Sea migrations—those could have happened, too.
“Solutrean evolved into Clovis over close to 13,000 years,” Stanford said, and the Clovis hunters began migrating westward when the cold snap brought dry, windy, inhospitable weather to the East Coast.
But the archaeological evidence found so far in support of a European migration more than 20,000 years ago has raised skepticism. And as is the case with the kelp highway, many sites that could prove or disprove the hypothesis are now underwater. Dillehay said he had found the idea of an Atlantic crossing worthy of further investigation, even though “the hard evidence is not yet there.”
Waters, of Texas A&M, is skeptical. “I’m looking for clean evidence,” he said. “We’re past ‘Clovis first,’ and we’re developing a new model. You read the literature and you use your imagination, but then you have to go out and find the empirical evidence to support your hypothesis.”
None of the doubts expressed by critics have stopped Stanford and Bradley, veterans of the Clovis wars, from pushing forward. “Solutrean people became more and more efficient in exploiting the rich sea margin resources,” they write in Across Atlantic Ice. “Eventually their range expansion led them to a whole new world in the west.”
These days Waters says his research focuses on pre-Clovis or likely pre-Clovis sites where more information can be obtained. Unlike many of his colleagues, Waters isn’t captive to peer reviewers at granting agencies; the Center for the Study of the First Americans also has its own funding. “In the past you’d propose something and send it out for review, and the Clovis people would shoot it down,” he said.
It was against the backdrop of renewed enthusiasm for findings predating Clovis settlements that Waters reopened the Page-Ladson site on the Aucilla River. For Waters, the debate about Clovis “is finished,” he said over breakfast one morning in Perry, Florida, before we went out to the Aucilla site. “The objective everywhere we go is to learn more about pre-Clovis by doing good science. I’m investigating the first Americans.” If some folks don’t want to believe it, he added, “that’s up to them.”