Native Village 
Youth and Education News

October, 2013

When Did Humans Come to the Americas?Recent findings date their arrival earlier than thought, sparking hot debate among archaeologists
http://www.smithsonianmag.com/
Condensed by Native Village

Florida: The slow-moving Aucilla River in northern Florida flows underground, tunneling through bedrock limestone. But here and there it surfaces, and preserved in those inky ponds lie secrets of the first Americans.

For years adventurous divers had hunted fossils and artifacts in Aucilla sinkholes. They found stone arrowheads and the bones of extinct mammals.

Then, in the 1980s, archaeologists from the Florida Museum of Natural History opened a formal excavation in one particular sink. Below undisturbed sediment they found nine stone flakes chipped from a larger stone, most likely from a person making tools and projectile points. They also found a mastodon tusk, scarred by circular cut marks from a knife. The tusk was 14,500 years old.

Suddenly, the Aucilla sinkhole became one of the earliest places in the Americas to show a human presence.   Curiously, most scholars ignored these findings and remained convinced that America’s earliest settlers arrived 13,500 years ago.

But now the sinkhole is getting a fresh look. So are other archaeological sites that show evidence of an earlier -- perhaps much earlier -- human presence in the Americas

Michael Waters is director of the Center for the Study of the First Americans at Texas A&M University. He organized archaeologists and divers to gather more evidence of the sinkhole’s role in prehistory.

“This site is as old as anything in North America,” Waters said. “The context is fine, and the dating is fine, but people just looked at it and said, ‘Hmm, that’s interesting,’ and that was it. It had a lot of potential, but it was in limbo. We’re here to confirm the earlier work, and if we’re lucky, we’ll find some more artifacts.”

Led by underwater archaeologist Jessi Halligan, Waters’s team worked at the Page-Ladson sink. The sink lies 30 feet below the Aucilla's surface which, after heavy rains, turns nearly black from humus from hardwood hammock. Fish, birds, turtles gators live here.  Halligan’s divers were the only human presence.

Underwater archaeological sites were staked out and marked in meter-square quadrants. Divers troweled mud into a small suction dredge which emptied into mesh screens mounted on a skiff. Big pieces—stones, bones, leaves and perhaps human artifacts—collected on the top screen. Small stuff was caught by the sixteenth-inch mesh below.

First the researchers cleared 15 years of detritus that accumulated after the first excavation ended. Then, to reach the most promising level, divers removed a ten-foot layer of clay. The work was tedious—“like diving in dark roast coffee,” said archaeologist James Dunbar, a member of the first Aucilla team. Everything below the sediment was as old as the people who left it there. In the oxygen-deprived mud deposits of the Aucilla River, nothing decays.

The divers unearthed small bone fragments, the vertebra of a large mammal and a shoulder blade -- possibly that of the same mastodon whose tusk bore the cut marks of ancient hunters. Also recovered were pounds of mastodon digesta, the remains of vegetation that the six-ton beast chewed and swallowed.

The researchers' findings validated the original excavation, as did their findings on later expeditions.  Each new discovery generated fresh enthusiasm.

“All we need now,” said Halligan, “are more human artifacts.”

 History

About 100,000 years ago, modern human beings started spreading out from their African homelands to occupy Europe and Asia. They even went to Australia by sea, displacing or absorbing Neanderthals and other archaic hominid species.

That diaspora took about 70,000 years, and when it was completed our ancestors stood triumphant.

The peopling of the Americas, scholars tend to agree, happened sometime in the past 25,000 years. The standard view of events is that a wave of Siberian hunters crossed the Bering Strait to the New World at the end of the last ice age.  At the time, the Bering Strait was a land bridge formed by glaciers and continental ice sheets.

The key question is: when did this migration occur? Researchers suggest that it happened between 25,000 -12,900 years ago.

For decades the most compelling evidence consisted of human-made projectile points found in New Mexico called “Clovis points. ” Radiocarbon dating determined that the Clovis sites were 13,500 years old. The idea that these Clovis people were the first Americans quickly won over the research community.

“The evidence was unequivocal,” said Ted Goebel, from the Center for the Study of the First Americans. Clovis sites, it turned out, were spread across the continent, and “there was a clear association of the fauna with hundreds, if not thousands, of artifacts,” Goebel said. “Again and again it was the full picture.”

Furthermore, the earliest Clovis dates corresponded roughly to the right geological moment.

“It was a very nice package, and that’s what sealed the deal,” Goebel said. “Clovis as the first Americans became the standard, and it’s really a high bar.”

The hunters spread across the U.S. and Mexico, the story goes. They pursued prey until the last cold snap, when too few animals remained to support them. Radiocarbon dates show that most megafauna became extinct around 12,700 years ago. The Clovis points disappeared then as well, perhaps because there were no longer any large animals to hunt.

Over time, the Clovis theory acquired the force of dogma.  Any artifacts or theories that cast doubt on the Clovis-first idea, were ridiculed.

skeptics

Take South America. In the late 1970s, U.S. archaeologist Tom D. Dillehay and his colleagues began excavating an ancient settlement at Monte Verde in Chile.  In a creek bog, excavators found cordage, mastodon remains, stone choppers, augers, plant remains, edible seeds and traces of wild potatoes. Radiocarbon readings showed that the site was 14,800 years old, predating Clovis by more than 1,000 years.

But -- there were no Clovis points. Did Clovis hunters go to South America without their trademark weapons (highly unlikely)? Or, did people settle in South America even before the Clovis people arrived?

There must have been “people somewhere in the Americas 15,000 or 16,000 years ago, or perhaps as long as 18,000 years ago,” said Dillehay, now at Vanderbilt University.

Dillehay was singled out for special criticism. He was all but ostracized by Clovis advocates for years. When he was invited to meetings, speakers denounced Monte Verde. “

It’s not fun when people write to your dean and try to get you fired,” he recalled. “And then your grad students try to get jobs and they can’t get jobs.”

The Monte Verde site gained wider acceptance after well-known archaeologists visited it in 1997 and verified the integrity of Dillehay's work.  Dillehay was pleased, “but it was a small group of people,” he said, meaning others in the profession continued to harbor doubts.

The skepticism lingers. Gary Haynes, a University of Nevada-Reno anthropologist and a Clovis advocate, is not convinced. “There are only a few artifacts, and no flakes,” he said of Monte Verde. “There are a lot of things that have been interpreted as artifacts but don’t look like them. Many of the things may not be the same age, because it is difficult to know exactly where they were found in the site.”

Dillehay rebuffs the criticisms with these arguments: 


More than
1,500 pages were published on Monte Verde -- five times more than were ever written on any other site in the Americas, including Clovis.

All artifacts came from the same surface covered by the peat bog. All made sense in terms of the site’s activities.
 


The great majority of artifacts are flaked pebble tools, typical of South American unifacial technologies.



North Americans impose their evaluations on South America without even knowing the data down south.”
 

“Now the field has moved on, and there are numerous pre-Clovis sites that have come to the forefront,” he said.

NEW EVIDENCE

The Buttermilk Creek archaeological site lies near Austin, Texas. In a layer of earth beneath a Clovis excavation, researchers led by Waters have found 15,528 pre-Clovis artifacts. Most are toolmaking chert flakes, but 56 are actual chert tools. Using luminescence techniques, they found that the oldest artifacts dated to 15,500 years ago -- 2,000 years older than Clovis. The work “confirms the emerging view that people occupied the Americas before Clovis,” the researchers concluded  in 2011. Waters’ believes the people who made the oldest artifacts might have been experimenting with stone technology. Over time, that technology may have developed into Clovis-style tools.

Waters has also collaborated with Thomas Stafford from Stafford Research Laboratories to debunk the Clovis theory. Using accelerator mass spectrometry (AMS), a dating technique more precise than radiocarbon, they reanalyzed a mastodon rib recovered in Manis, Washington that had a projectile point lodged in it. The original radiocarbon tests  showed it to be 13,800 years old—centuries older than Clovis. The new AMS tests confirmed those findings. DNA showed that the projectile point was mastodon bone.

Waters and Stafford also used AMS technlogy to retest many known Clovis samples from around the country. The results, Waters said, “blew me away.” Instead of a culture spanning about 700 years, the results shrunk the Clovis window from 13,100 to 12,800 years ago. This meant Siberian hunters had only 300 years to negotiate the ice-free Bering Strait, settle two continents and put the megafauna on the road to extinction.

“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 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 says his own attitude about pre-Clovis finds is “acceptance with reservation.” He's disturbed by “nagging” shortcomings. He says each older site appears to be one-of-a-kind, without a regional pattern.  With Clovis, original sites were part of something bigger.

This absence of a consistent pre-Clovis pattern “is one of the things that has hung up a lot of people, including myself,” he said.

Boats, Superhighways, Points, and DNA

The discovery of pre-Clovis artifacts requires scholars to come up with new ideas about how and when people first arrived in the Americas. If humans were living here 14,800 years ago, they didn't come use the ice-free Siberian Strait corridor. It did not appear for another 1,000 years.

Maybe the first Americans came in small boats and followed the coastline. That possibility was suggested in the 1950s when Clovis-era human bones—but no artifacts -- were found on Santa Rosa Island off the California coast.

Over the past decade, though, archaeologists have unearthed projectile points from Santa Rosa and other Channel Islands. They also uncovered remains of fish, shellfish, seabirds and seals. Radiocarbon dates show much of the organic material was about 12,000 years old, roughly within the Clovis time frame.

The findings aren't proof that North America's first settlers came by sea. The islands were only four miles offshore at the time and could have been visited by mainland people. Still, the sites prove that these island dwellers were seafarers of a sort and accustomed to a seafood diet.

Jon Erlandson is a University of Oregon archaeologist, and Rick Torbin is an archaeologist from the Smithsonian. They propose a pre-Clovis “kelp highway” for coast-hugging seamen that may have skirted the southern edge of the Bering land bridge 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 idea of ancient people traveling great distances by boat isn’t far-fetched. Many anthropologists believe that humans voyaged from the Asian mainland to Australia 45,000 years ago.

While Erlandson is convinced that the Clovis were not the first people in the Americas, he admits that definitive proof of a kelp superhighway may never be found. Whatever beach settlements existed in those days of low sea levels were submerged or swept away by Pacific tides.

Erlandson also points out that the Channel Islands projectiles have nothing in common with Clovis points. They are related to a different toolmaking approach called the western stemmed tradition. These have different shaped stems that attach projectile points to spears or darts. And while Clovis points are fluted, these are not.  Such points were prevalent in the Pacific Northwest and the Great Basin. This indicates that other tool-making human cultures were in the Americas at the same time as the Clovis people -- perhaps beforehand, as well.

The link between Channel Islands' artifacts and the western stemmed tradition have reached Oregon. There, inside the Paisley Caves, scientists excavated similar points along with organic material that dates 13,000 years old—contemporary with Clovis.

Dennis L. Jenkins from the University of Oregon led the Paisley excavation. The site had first been explored in the 1930s.  The earlier documentation didn't show a definite association between the bones and artifacts found. Jenkens re-examined the area and soon “we had artifacts and we had the bones” from the site.

The researchers used radiocarbon dating tests on petrified human feces. They also analyzed human mitochondrial DNA, probably shed from the intestinal wall. The DNA 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. We’ve convinced the people who are willing to be convinced that the caves are as old as Clovis, if not older.”

radical ideas, overpopulation, and dinosaur tusks

Perhaps the most radical scholarly work is the theory of Dennis Stanford and Bruce Bradley. (Stanford is a curator of North American archaeology at the National Museum of Natural History. Bradley is an archaeologist at Britain’s University of Exeter) They suggest European immigrants colonized the Americas several thousand years before Clovis. 

Their book, Across Atlantic Ice, suggests that Europeans reached the New World more than 20,000 years ago. These Europeans settled in the eastern U.S., developed the Clovis technology over thousand of years, then spread across the continent.

This theory points out similarities between Clovis points and “laurel leaf” points from the Solutrean culture. The Solutreans flourished in southwestern France and northern Spain  24,000 - 17,000 years ago. Artifacts found at several pre-Clovis sites, including Page-Ladson, Meadowcroft Rock Shelter (PA) and the sand dunes of Cactus Hill  (VA) have similarities to Solutrean technologies.

The Solutreans territory on the European continent was apparently compact. Over time, encroaching glaciers and extreme cold may have forced them to cluster on the Atlantic coast. Stanford and Bradley say the stress of overpopulation may have forced some Solutreans to escape by sea. They headed north and west beneath the Atlantic ice sheet and landed in North America at the Grand Banks of Newfoundland.

Evidence for Solutrean presence in America includes stone artifacts found at several sites on Chesapeake Bay. All proved to be more than 20,000 years old. While most dates were taken from organic material, the exception was a mastodon tusk. The tusk, with bone and teeth attached, was netted by a fisherman in 1974. Along with it was 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. Clovis hunters then migrated westward when the cold snap brought dry, windy, inhospitable weather to the East Coast.

But the archaeological evidence supporting a European migration more than 20,000 years ago has raised skepticism. Just like the kelp highway, many sites which could prove or disprove this theory are now underwater.

But the critics won't stop Stanford and Bradley 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.”

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