And in the last 15, to 20, years, sea levels have risen some feet. But Fedje and his colleagues have developed elaborate techniques to find ancient shorelines that were not drowned by rising seas.
Their success has hinged on solving a geological puzzle dating back to the end of the last ice age. As the world warmed, the vast ice sheets that covered much of North America—to a depth of two miles in some places—began to melt.
This thawing, coupled with the melting of glaciers and ice sheets worldwide, sent global sea levels surging upwards. In some places, Fedje says, the coast of British Columbia rebounded more than feet in a few thousand years. The changes were happening so rapidly that they would have been noticeable on an almost year-to-year basis. But this is a very dynamic landscape. In order to track ancient shorelines, Fedje and his colleagues took hundreds of samples of sediment cores from freshwater lakes, wetlands and intertidal zones.
Microscopic plant and animal remains showed them which areas had been under the ocean, on dry land and in between. They commissioned flyovers with laser-based lidar imaging, which essentially strips the trees off the landscape and reveals the features—such as the terraces of old creek beds—that might have been attractive to ancient hunter-gatherers.
These techniques enabled the archaeologists to locate, with surprising accuracy, sites such as the one on Quadra Island. Arriving at a cove there, Fedje recalled, they found numerous Stone Age artifacts on the cobble beach. In and , a Hakai Institute team led by archaeologist Duncan McLaren excavated a site on Triquet Island containing obsidian cutting tools, fishhooks, a wooden implement to start friction fires and charcoal dating from 13, to 14, years ago.
On nearby Calvert Island, they found 29 footprints belonging to two adults and one child, stamped into a layer of clay-rich soil buried under the sand in an intertidal zone. Wood found in the footprints dated back roughly 13, years. Other scientists are conducting similar searches.
Loren Davis, an archaeologist at Oregon State University, has cruised from San Diego to Oregon using imaging and sediment cores to identify possible settlement sites drowned by rising seas, such as ancient estuaries. That find, announced in August , meshes nicely with the theory of an early coastal migration into North America. The settlement is at least years older than the site that had long been viewed as the oldest confirmed archaeological site in the Americas—Swan Point, Alaska.
An axiom in archaeology is that the earliest discovered site is almost certainly not the first place of human habitation, just the oldest one archaeologists have found so far.
And if the work of a host of evolutionary geneticists is correct, humans may already have been on the North American side of the Bering Land Bridge about 20, years ago. Eske Willerslev, who directs the Center for GeoGenetics at the Globe Institute at the University of Copenhagen and holds the Prince Philip chair of ecology and evolution at the University of Cambridge, sequenced the first ancient human genome in According to Willerslev, sophisticated genomic analyses of ancient human remains—which can determine when populations merged, split or were isolated—show that the forebears of Native Americans became isolated from other Asian groups around 23, years ago.
New York has always been the gateway state, the state that absorbs the greatest diversity of newcomers from abroad. In when for the first time the US census recorded birthplaces, the leading birthplaces for residents not born in New York were in order: Ireland, Germany, England, Connecticut, Massachusetts, Vermont, New Jersey, and Canada, with a dozen other countries further down the list. Texas has been a migration magnet throughout its history, which helps explain the record of growth that now makes it the second most populous state following California.
Migration, most of it illegal, from Tennessee, Alabama, and Mississippi fueled the rebellion that wrestled the province from Mexico in In the decades that followed an enormous number of southerners moved west to expand the cotton belt, many of them enslaved. Washington remains today a state where most residents came from somewhere else, another state or another country.
Occupied by Americans since the s, it's population grew slowly until statehood in , then surged after the discovery of gold in Alaska and the Yukon in Farming, timber, and fishing attracted newcomers from the upper Midwest and from northern Europe, along with smaller numbers of Chinese and Japanese. Arizona remains today a state where most residents came from somewhere else, either another state or another country.
The United States seized the area in the war against Mexico in , but few Americans found reason to settle there until silver and cooper deposits brought miners starting in the late s. An population of less than 10, grew to , by Whites comprised less than half of the turn-of-the-century population.
One third were ethnic Mexicans, born either in the Southwest or Mexico. Native peoples accounted for more than 20 percent of persons enumerated in the census.
Colorado remains today a state where most residents came from somewhere else, either another state or another country. Cheyenne, Shoshone, Arapahoe, Ute, and other native nations commanded the area until when the United States seized it in its war against Mexico.
The discovery of gold near Pike's Peak in set up the first significant influx of newcomers, mostly whites from Midwestern and Northeastern states. So, it looks like people were crossing the Atlantic, hunting along the ice packs—following ice flows—with skin boats, and arriving in Maryland and Virginia. The first people there came out of the ground. These are stories related to origin and creation stories all over the Americas. Native tribes have clear stories about how they got here, coming out of caves or up through springs and underground sources.
The idea of coming from somewhere else might threaten the notion that they have primacy on the lands. But, they obviously do because they are coming from these much older stories than anybody else.
The landscape people walked into was substantially different. The animals were much larger. You have mammoths, dire wolves , and sabre tooth cats. Everything is very big and very woolly, and in some places armoured. But there were many places that looked the same. Other parts, including most of Canada, were completely covered with ice.
There are a number of sites in Alaska, like Swan Point , where you can see signs of mammoth hunting. Early people were eating salmon, seaweed, deer, and rabbit. The mammoth hunts were probably culturally important, much like the northern whale hunts. Hunting whales in the north out of skin boats is also a dangerous endeavour, and people have often been killed.
I imagine the same thing happened while hunting mammoths. You would have these stories of epic mammoth hunts, who died and who lived, and these stories would have been passed down for thousands of years.
No, I decided that if I dressed up in furs and carried a spear, I would have probably died. Once we got up there, we clicked in the skis, put our gear on a sled, and headed across the ice. In one sense, it told me that this is the worst way to do it. Humans have often done ridiculous things!
Being out there on the ice I thought this is maybe where the crazy people went, the ones who were looking to fall off the edge of the Earth. This evidence confirmed what most archaeologists suspected about the location of this homeland. It also strongly suggested that the timing proposed in the Clovis First scenario was wrong. Geneticists now calculate, based on mutation rates in human DNA, that the ancestors of the Native Americans parted from their kin in their East Asian homeland sometime between 25, and 15, years ago—a difficult time for a great northern migration.
Huge glaciers capped the mountain valleys of northeastern Asia, at the same time massive ice sheets mantled most of Canada, New England and several northern states. Indeed, reconstructions of past climate based on data preserved in ice cores from Greenland and on measurements of past global sea levels show that these ice sheets reached their maximum extent in the last glacial period between at least 22, and 19, years ago.
They had a toolbox of tactics and strategies. Dressed in warm, tailored hide garments stitched together with sinew and bone needles and armed with an expert knowledge of nature, the ancestors of the Paleo-Americans entered an Arctic world without parallel today. The ice sheets in northern Europe and North America had locked up vast quantities of water, lowering sea level by more than meters and exposing the continental shelves of northeastern Asia and Alaska. These newly revealed lands, together with adjacent regions in Siberia, Alaska and northern Canada, formed a landmass that joined the Old World seamlessly to the New.
Known today as Beringia, this landmass would have made a welcoming way station for pre-Clovis migrants. The air masses that swept over it were so dry they brought little snowfall, preventing the growth of ice sheets. As a result, grasses, sedges and other cold-adapted plants thrived there, as shown by plant remains found preserved under a layer of volcanic ash in northwestern Alaska and in the frozen intestines of large herbivores that once grazed in Beringia.
These plants formed an arid tundra-grassland, and there woolly mammoths weighing as much as nine tons grazed, as did giant ground sloths, steppe bison, musk ox and caribou. Genetic studies of modern Steller's sea lion populations suggest that this sea mammal likely hauled out on the rocks along Beringia's island-studded south shore. So the migrants may have had their pick not only of terrestrial mammals but also of seafaring ones. Received wisdom holds that the trailblazers hurried across Beringia to reach warmer, more hospitable lands.
Some researchers, however, think the journey could have been a more leisurely affair. The major genetic lineages of Native Americans possess many widespread founding haplotypes—combinations of closely linked DNA sequences on individual chromosomes that are often inherited together—that their closest Asian kin lack.
This suggests the earliest Americans paused somewhere en route to the New World, evolving in isolation for thousands of years before entering the Americas. The most likely spot for this genetic incubator is Beringia. There the migrants could conceivably have been cut off from their Asian kin as the climate cooled some 22, years ago, forcing Siberian bands to retreat south. Whether the migrants cooled their heels in Beringia, however, or somewhere else in northeastern Asia, people eventually began striking off farther east and south.
A warming trend began slowly shrinking North America's ice sheets some 19, years ago, gradually creating two passable routes to the south and opening the possibility of multiple early migrations. According to several studies conducted over the past decade on the geographical distribution of genetic diversity in modern indigenous Americans, the earliest of these migrants started colonizing the New World between 18, and 15, years ago—a date that fits well with emerging archaeological evidence of pre-Clovis colonists.
Archaeologists take up the tale of the earliest Americans as these travelers pushed southward, exploring a wilderness untouched by humans. In an office decorated with prints and pictures of sharks and a poster of a traditional Chumash wood canoe, Jon M.
Erlandson, an archaeologist at the University of Oregon, mulls over new evidence of their journey. Reed-thin, tousled and in his mid-fifties, Erlandson has spent much of his career digging at sites along the coast of California, becoming one of the foremost proponents of what is often called the coastal route theory.
Whereas supporters of the Clovis First model envisioned humans reaching the Americas by trekking overland, Erlandson thinks the earliest travelers arrived by sea, paddling small boats from East Asia to southern Beringia and down the western coast of the Americas. Now he and his colleague Todd J. Braje of San Diego State University have uncovered key new evidence of ancient mariners who set out in East Asia and ended their journey in Chile.
Scientists first began thinking about this coastal route in the late s, when archaeologist Knut Fladmark, now a professor emeritus at Simon Fraser University in British Columbia, started examining geologic and pollen records to reconstruct ancient environments along Canada's western coast.
At the time, most experts believed that the entire northwestern coast lay under thick ice until the end of the last glacial period. Analyses published in the s and s of ancient pollen from coastal bogs, however, showed that a coniferous forest thrived on Washington's Olympic Peninsula 13, years ago and that other green refugia dotted the coast.
Early humans camping in these spots, Fladmark concluded, could have fueled up on seafood, from shellfish to migrating pink salmon. They may also have hunted waterfowl migrating along the Pacific flyway, as well as caribou and other hardy land animals grazing in the larger refugia. Archaeologists now know that much of the British Columbian coast was free of ice at least 16, years ago. Although they have yet to find any preserved boats in early American coastal sites, many researchers think such watercraft were probably available to these wayfarers: at least 45, years ago humans voyaged and island-hopped all the way from Asia to Australia.
Traveling by water down the western coast of the New World would have been easier in many respects than trekking overland. Still, finding campsites of early mariners has proved a tall order for scientists.
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