Instead of being big game hunters, the first Americans may have conquered the New World by boat following a trail of sushi…
THE “first Americans” have long been seen as intrepid ice-age hunters whose appetite for mammoths and other big game led them across the frigid wilds of Siberia and over the Bering land bridge some 13,500 years ago. There, in the New World, bands of early humans trekked down a narrow, ice-free corridor, fanning out south of the ice sheets, crossing raging rivers and steep mountain passes, and adapting to a succession of alien ecosystems – including desert, chaparral, cloud forest, rainforest and pampas – until finally running out of land in Tierra del Fuego. It was a journey of epic proportions. So much so that the famous French archaeologist François Bordes once described it as a feat that would go unrivalled “until man lands on a planet belonging to another star”.
So solid seemed the evidence for this long march that most archaeologists simply refused to entertain any other possibilities. Then, in the 1990s, several discoveries shot large holes through the theory. Today a growing number of experts favour a very different scenario. Rather than trekking on foot to the New World, ice-age Asians may have paddled there in small boats, following a nearly continuous belt of kelp forests in the coastal waters of the Pacific Rim, from Japan to Alaska and southern California. Far from taking an epic leap into the unknown, these pioneers would have had no need to adjust to strange ecosystems or devise brand-new hunting technologies. “I think they were just moving along the coast and exploring,” says archaeologist Jon Erlandson of the University of Oregon. “It was like a kelp highway.”
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“I think they were just moving along the coast, exploring. It was like a kelp highway”
This new theory, which Erlandson and his colleagues will publish in a paper in the next issue of the Journal of Island and Coastal Archaeology, is supported by a wide range of findings, from discoveries of ice-age sea voyages in Japan to studies of ancient human DNA and investigations of prehistoric marine ecosystems. What’s more, all the evidence suggests the New World was colonised earlier than we thought. Now archaeologists are scrambling to extend the time line backwards – a fiendishly difficult proposition. Some 20,000 years ago, North America’s great ice sheets began to melt. Since that time, the sea level has risen more than 100 metres, submerging ancient coastal plains. Today, the campsites of early coastal dwellers lie buried under thick sediment at the bottom of the sea, but the hunt is now on to rediscover them.
It was a speck of ancient pollen that first raised the possibility of ice-age seafarers. In the late 1950s, Calvin Heusser, a graduate student from the University of Oregon, discovered these tiny plant fossils where no one thought they should be – in late ice-age sediments from bogs along the North American coast, from Alaska to Oregon. According to the prevailing theory at the time, a massive ice sheet had shrouded the entire north-west coastline until the last ice age ended 11,500 years ago. Heusser’s pollen suggested otherwise, pointing to pockets of coastal greenery at least 12,000 years ago. Such places, he realised, could have served as outposts for ancient mariners from Asia.
Intrigued, archaeologist Knut Fladmark from Simon Fraser University in British Columbia, Canada, began to reconstruct the ancient ecology of the north-west coast in the 1970s, drawing on oceanographic, climatic and geological data. His results painted the coast, with its rich supplies of shellfish, as a far more hospitable place towards the end of the last ice age than the bleak ice-free land corridor down which the first Americans were supposed to have migrated. But Fladmark’s work was largely dismissed. For a start, there was little evidence that ice-age humans could have navigated the stormy north Pacific at such an early date. What’s more, most archaeologists regarded shellfish as starvation fare. Ancient Americans, they believed, would only have turned to such calorie-poor pickings after they had wiped out mammoths and other megafauna. “The first few times I presented this material,” Fladmark recalls, “I was met with absolute anger by the old guys.”
During the 1990s, however, a series of major discoveries cast serious doubt on the old theory. First came Monte Verde. Located just 50 kilometres from the Pacific coast, the Chilean site revealed that people had dined on game and collected shellfish 14,850 years ago. By 1997, archeologists generally accepted Monte Verde as the oldest site in the New World, pushing back the arrival of humans by more than 1000 years. Then Canadian geologists re-dated the ice-free corridor through western Canada. Their study showed that converging ice sheets probably blocked the proposed land route into the interior until some 13,000 years ago, making it impassable for the earliest Americans. Finally, physical anthropologists published their report on Kennewick Man, a 9000-year-old male discovered along the banks of the Columbia River in Washington state. The detailed comparative study showed that he looked more like the Polynesians, or the Ainu, an aboriginal people of Japan, than the Siberians. It was clearly time to test the theory of coastal migration.
Ancient mariners
At the University of Oregon, Erlandson began searching for evidence of early human seafaring. From his reading, he knew that archaeologists had never unearthed an ice-age boat. Nor had they found any representations of watercraft in Upper Palaeolithic rock art. Nevertheless, he could track the voyages of the ancient mariners by poring through the archaeological literature and compiling the dates when people first appeared on remote islands. Anatomically modern humans, he discovered, had taken to seafaring relatively early on. They had first arrived in the Willandra Lakes region in Sahul – an ancient continent that embraced Australia, New Guinea and Tasmania – some 50,000 years ago. To do so, they had to island-hop from Asia, crossing distances of up to 90 kilometres in boats. “This is now generally seen as the earliest evidence for planned maritime voyaging,” says Erlandson.
Many millennia passed, however, before mariners undertook similar voyages in the northern hemisphere. The earliest evidence he found was from the island of Okinawa, where researchers have excavated the 36,000-year-old bones of a child from a limestone cave. To reach Okinawa from the Asian mainland, the child’s family must have made several sea voyages, the longest stretching 75 kilometres. Further north, the inhabitants of Honshu, one of the main islands of Japan, set out across the North Pacific more than 20,000 years ago to Kozushima, an island 50 kilometres away, to collect obsidian – a type of volcanic glass – to make tools.
How Japan’s Upper Palaeolithic inhabitants navigated the chilly northern waters remains a mystery. “It could have been skin boats,” suggests Erlandson, perhaps like the kayaks of the Inuit. Whatever their watercraft, it appears that explorers from Japan could have made their way in stages to the New World, journeying northward to the Kurile Islands, then the Kamchatka Peninsula, and to the island-studded southern shore of the Bering land bridge and beyond. In all likelihood, this would have been a numbingly cold voyage through sometimes treacherous waters, gravely testing the abilities of ancient mariners. Still, “what was once imponderable now seems entirely conceivable and increasingly likely”, according to Erlandson.
The earliest direct evidence of seafarers in the New World comes from the Channel Islands, off California’s southern coast. Rising sharply out of the Pacific, this area is a playground for adventure tourists today. John Johnson, curator of anthropology at the Santa Barbara Museum of Natural History, is interested in more ancient travellers, however. Almost 50 years ago, his predecessor at the museum chanced upon three human bones eroding out from a canyon wall at on Santa Rosa Island. In 2005, Johnson and his team used ground-penetrating radar to map the ancient landscape, now buried under 9 metres of rock and sediment. They also dated the bones using multiple lines of evidence. “So now we can really corroborate that the age of Arlington Man is between 13,000 and 13,200 years,” Johnson says.
Fishing for clues
Late in the last ice age, Santa Rosa and the other northern Channel Islands formed one large island, Santarosae, 11 kilometres off the mainland. To voyage there, Arlington Man would have needed seafaring savvy and “some form of watercraft”, explains Johnson. There is no doubting the ancient island-dweller’s credentials as a mariner, but his origins and the route that he and his ancestors took to Santarosae remain a mystery. Johnson’s team has tried repeatedly to recover ancient DNA from the badly decomposed bones – but without success.
New research by Brian Kemp, a molecular anthropologist at Vanderbilt University in Nashville, Tennessee, seems to offer a clue to the origins of Arlington Man. He has just recovered DNA from the remains of another ancient coastal dweller, a 10,300-year-old man interred in an Alaskan cave (). It is, to Kemp’s knowledge, the oldest human DNA from the New World, and when he began to sequence it, he discovered something surprising: a rare subtype of haplogroup D. Haplogroup D is a distinctive pattern of groups of genes on the Y chromosome, thought to have evolved about 40,000 years ago and now found most commonly in populations in Tibet and the Japanese archipelago. Fascinated, Kemp searched for the same rare subtype in published genetic sequences from 3286 modern and ancient Native Americans and Asians. He found just one match in Asia – too small a sample to say anything meaningful – but in America he had 47 hits, mostly from native groups living along the west coast of North and South America.
Kemp’s trail of DNA matches may chart the route of an ancient maritime migration all the way from Alaska to Tierra del Fuego. “It is certainly consistent with coastal migration,” he says. “I think it’s very compelling.”
What might have persuaded ice-age mariners from Japan to make this journey? Erlandson thinks he knows. Working with a team of archaeologists and marine biologists, he has spent the past eight years studying kelp forests and mapping their distribution in ancient times. The rich biological diversity of today’s forests – which are found off the coast of every continent except Antarctica – reveals that they are very old. The numerous kelp species along North America’s north-west coast, and the diversity of organisms that feed on them, suggest that they evolved there, probably between 30 and 50 million years ago. Afterwards they spread along the Pacific Rim to Asia, forming a nearly continuous underwater forest. Surprisingly, this kelp highway could have flourished even during the ice age. Studies of ancient sea temperatures suggest ice formed only in winter along the southern coast of the Bering land bridge 18,000 years ago, and seasonal freeze was not sufficient to wipe out the great marine forests. Kelp, as biologists in Alaska have discovered, can live in a kind of suspended animation under winter ice, only to bloom again with spring thaw.
“Today, fishermen make a beeline for kelp forests,” says team member Mike Graham, a kelp expert at Moss Landing Marine Laboratories in California. Kelp thrives close to the shore in cold, nutrient-rich waters. Some species, such as the giant kelp, grow at a rate of nearly a metre a day, reaching 45 metres in length and creating one of the most productive ecosystems on Earth. Many fish species shelter in their fronds, and the particles they continuously shed feed abalone, turban snails and thick beds of mussels. “It’s quite likely that Japan’s ancient inhabitants were familiar with these systems before they came over,” says Graham. “What people saw, as they moved, was familiar species, familiar ways of life, familiar associations.”
“What people saw as they moved was familiar species, familiar ways of life, familiar associations”
Just when the ancient mariners may have followed this kelp highway to the New World remains the big question. A few coastal researchers think such seafarers could have arrived during a period of global warming more than 30,000 years ago. Yet so far archaeologists have not found any widely accepted sites of such antiquity either inland or along the coast in the Americas. As a result, most experts favour a later entry, some time after 16,000 years ago. By then, they say, the massive glaciers had retreated from the outer north-west coast, dwarf willows and other tundra plants had taken root, and the stage was set for humans. The trouble is, if they are correct, rising sea levels mean the crucial evidence is now submerged.
Off the rugged coast of British Columbia’s remote Queen Charlotte Islands, archaeologist from the federal government agency Parks Canada is searching for that evidence. During the late 1990s, he and Heiner Josenhans from the Geological Survey of Canada digitally reconstructed a submerged river delta on the ocean floor at Werner Bay. Fedje and his team then spent two field seasons sampling likely-looking ancient camp sites by repeatedly lowering a bucket dredge more than 50 metres to the bottom and then sifting through heaps of muck and shells. Their prize find was a black basalt tool around 10,000 years old.
Despite this success, Fedje realised he needed to find a site that had suffered less churning from sea currents and that was accessible to divers. At nearby Section Cove he has now discovered a promising site. Thirty metres below the surface is the bed of an ancient stream that once flowed into a lake. Almost certainly, sockeye salmon spawned in the lake towards the end of the last ice age; Fedje and his colleagues have found their bones in a 12,200-year-old site 1 kilometre to the north on land. Early humans would have found the prospect of so many fish irresistible, and Fedje believes that a little terrace overlooking the stream would have served as a superb campsite. On the strength of this, Parks Canada officials have given the go-ahead for a team of underwater archaeologists to begin excavating next year.
It is an audacious project. The site lies close to the depth limit of conventional scuba technology, posing extra risks for the dive team, and Fedje will have to direct operations from a barge. Yet he is optimistic. “We are pretty positive that there will be an archaeological site where we think it should be on that lake shore,” he says. “There’s no reason why people couldn’t have been on these old landscapes 14,000 or more years ago.”
Not so long ago, such a statement would have been heresy, but today archaeologists are keeping an open mind about the idea America was first colonised from the sea. Coastal researchers are finally getting a chance to test the idea and to push back the prehistory of the New World in the process. For Erlandson and the others, it is an era of hope. Until recently, they found it impossible to raise money for underwater work. “But now that people are thinking about coastal migration,” he says, “we have a truly golden opportunity.”
