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A Drowned Forest
The Northwest Coast exudes more than a whiff of mystery and adventure. Brooding forests line the shores of fjords that slash deep into the mountain fastness. Haunted faces on carved cedar poles preside in silent disdain over abandoned native villages. The hushed secrets of the past beckon, yet remain elusive. Most enigmatic of all, lying hidden beyond the outer beaches and reefs and far below the surface is an entire lost world, a domain of the deep that is evoked in ancient native myth and confirmed by the latest technological wizardry. Invisible to modern eyes, this drowned zone holds clues to ancient seafaring people and how they came to populate our hemisphere.
These forgotten coastal dwellers first came to life for me when I rented a seaside homestead on a small island in British Columbia. The Stone House, as the owner called it, stood in a clearing just behind the beach at the head of an isolated bay fringed with regal Douglas firs and twisted red madrone trees. I liked the house, but what really intrigued me was the spot it stood on, a grassy level platform that spanned a quarter acre and was raised about six feet above the high tide line. As I paced around it with my aged landlord, he told me that this platform was no accident of geology but a human creation. It was an Indian shell midden, or organic native garbage dump, a dense buildup of shells that resulted from thousands of years of seasonal shellfish harvesting. There were similar middens behind nearly every beach along the sheltered "Inside Passage," which runs from Puget Sound in Washington State right up into the panhandle of Alaska.
My landlord had unearthed a crumbling human skull when he dug the house foundations four decades earlier. During my years there I was humbled by the thought of living on native ground hallowed by the centuries. Soon, I planted a vegetable patch on the midden next to the house. Digging in, I discovered that the soil, far from being the mixed sand and clay of ordinary garden dirt, consisted of crushed and broken shell along with humus from fallen leaves and droppings from the island's deer, sheep, and goats. My produce thrived.
One day, I hiked across the island to another bay and came upon a scene that helped me understand how middens were formed. A family from one of the Coast Salish tribes was busy digging clams by the bushel-load at low tide to sell to cash buyers. Their boat was pulled up high and dry on the mud flats. Lined up off to one side were a dozen or more thigh-high gunny sacks full of clams, each almost too heavy to lift. I was amazed at the volume of shellfish that could be taken from a single small beach, and it was easy to see how over scores of centuries shell middens could build up to depths of five to ten feet or more. In these modern times, the succulent bivalves would be taken away and shucked at a processing plant, or sold live in the shell. In the past, though, the Indians simply camped out at spots like this for days or weeks at a time, and were still doing so when the first European settlers arrived. After digging the clams, they smoked or roasted them and skewered them on sticks for storage. Shellfish gathering was a major part of their seasonal harvest cycle and was essential for laying in a supply of food for the winter. The shells were simply left behind above the tide line.
I had majored in anthropology briefly in college before moving on to other things, and living on the midden rekindled a passionate interest. It wasn't long before I was wangling invitations to potlatch ceremonies, going to watch native fisheries, and generally delving into coastal anthropology. Poking around in academic journals published by universities in Seattle and Vancouver, I learned that the leaching of chemicals from the shells helped greatly to preserve the bone and antler artifacts, such as fine harpoon points, that were so important to prehistoric coastal hunting and gathering. Nearly all coastal archaeology, in fact, involved digging in shell middens. This led me to other middens and archaeological sites on the nearby islands.
I quickly discovered that looking at today's shores could only take me back about 5,000 years, at least in my area. Because sea level on the Northwest Coast has changed so drastically and so rapidly since the Ice Age, in most places anything older was under water. Coastal archaeology along the Inside Passage had barely scratched the surface of land and sea, but the implications of ancient sea level change went well beyond creating local difficulties for a handful of anthropology professors.
At the peak of the last glaciation of the Ice Age -- 18,000 to 20,000 years ago -- great ice sheets covered much of northern Europe and Russia. In the southern hemisphere, enormous glaciers mantled the Andes. And in North America, the Laurentide ice sheet, with a central dome as much as three miles thick, extended from eastern Canada almost to the Rockies and down into the United States beyond the Great Lakes. Another ice sheet, the Cordilleran, stretched over the Rockies to the coast of Alaska, British Columbia, and northern Washington State. So much water was locked up in ice that world sea level was 350 to 400 feet lower than it is today.
Entire bodies of water that had existed prior to the glaciation dried up, and the former sea bottom became exposed land. In the best known case, the Bering Strait disappeared and became a broad "land bridge," around a thousand miles wide, connecting Asia and North America. We are all familiar with schoolbook pictures of ancient people, dressed in furs, hunting mammoth elephants and trekking across the land bridge to populate the New World.
There were also many islands, in all the world's oceans, that no longer exist. On maps of the North Pacific, we find no islands between Hawaii and the mainland of Alaska and British Columbia except just off the mainland coast. But in the last glaciation there were several islands well out in the Pacific. These were the tops of submarine mountains coming up from very deep water, just like the volcanic islands of Hawaii. Now they lie a hundred or more feet below the surface and attract vast schools of feeding fish. Oceanographers call them seamounts. Other islands that still exist at today's sea level were simply much larger at that time, and in some cases were connected to the mainland.
Nearly all the world's coastlines lay much farther to seaward than they do now. One respected archaeologist has calculated that the total amount of "extra" land this lowering of sea level created along the coasts of North America was equal to one and one half times the area of Texas. Life on the exposed land was very different from what we can see in modern times. The Northwest Coast today has a mild, wet climate and dense coastal rain forest. At the peak of glaciation, though, there was pack ice along shore and tundralike vegetation on land, much like the present north coast of Alaska.
Then the Ice Age waned. The ice sheets melted and gradually retreated from the coast, and the sea rose worldwide. In some places there were odd local effects. Where shorelines had been pressed down by the weight of the ice, the land rebounded at times even faster than the rise of the world ocean. But overall, between around 17,000 and 10,000 years ago, the rising sea simply drowned these once-extensive coastal lands under hundreds of feet of water.
Any people living along the coast would have been forced to relocate. But of course, there were no cities, probably not even permanent settlements of any size. People lived by hunting, fishing, and gathering, and they were always on the move, in step with their sources of food. And since it took thousands of years for the sea to rise, there was likely little disruption to the lives of those ancient people.
But there is one lingering consequence for us today. The rising sea inundated nearly all traces of Ice Age coastal dwellers throughout the world, making it nearly impossible to find evidence of when, where, and how people lived on those drowned lands. Because underwater searches are difficult, incredibly expensive and even, at times, dangerous, until recently archaeologists have hardly even tried. Instead, they have focused on what they could find, which is invariably at sites well inland from where so many people presumably lived. In this way, the rising sea has severely skewed the archaeological record and given a strong terrestrial bias to our image of the people and lifeways of these late glacial times.
We know, for example, that some late Ice Age people hunted mammoths with spears, because the stone spear points have been found in close association with mammoth bones. But they have been found on terra firma, of course, and far inland from the former ancient shoreline. We hardly know anything about what people were doing on the coasts of the world ten to twenty thousand years ago. Where did they live? What animals did they hunt? What fish did they catch, and how? What critters did they gather in the intertidal zone? What kinds of weapons and tools did they use?
For those of us who live in North America, there are additional questions. When did the first people arrive? From where and by what route? And for a few pioneering scientists of the last decade, that question has led to a more pressing one: Is it conceivable that the coastlines were inhabited before the interior of the continent? And if so, when?
Once I realized how drastically our coastal world had changed, everything I saw took on a slightly different hue. During those years I rebuilt a lovely old wooden cruising sailboat and spent much of each summer exploring the Northwest Coast with friends. While studying the undersea contours on nautical charts, I tried to picture the ancient world with hundreds of feet of water peeled away. The locations of beaches and sandspits, of islands and reefs -- all would have been different. It must have been a rugged land of rubble-strewn moraines and tundra, where towering cliffs of ice fronted on the sea and roiling waves of ice fog drifted out over the continental shelf, a coastal fringe inhabited by polar bears, walruses, and other Arctic species that vanished from the region 10,000 years ago.
On one of my sailing trips north, we anchored for the evening among a maze of heavily wooded and unpopulated islands not far south of Alaska. We had seen only one other boat the entire day and easily imagined ourselves to be moored at the edge of the world. After dinner, my friend and I set out in the dinghy to explore our silent domain. At one island we went ashore and stumbled upon a well-concealed campsite littered with rusting pans and disintegrating plastic. A derelict canoe, cracked and hidden in the bush, was half filled with scummy water and mosquito larvae. Our fantasies ran wild. Was this the lair of a Crusoe-like recluse, or a fugitive from the law? Were there skeletons, literal or figurative, hidden on that island? It was a mystery we never solved.
A nearby island posed a different kind of riddle. Rowing along its shore, we noticed that the tide seemed to be exceptionally high. It was so high, in fact, that the sea was actually lapping at the base of dead trees on the gently sloping shoreline. Looking closer, we realized that all the trees from the high tide line back to at least 40 or 50 feet were gray and bare of foliage, killed off by the salt water. But the trees had not yet fallen over. We realized that this forest could not have become established in the first place if salt water had always soaked the soil in which they grew. The sea must have risen at least several feet within the lifespan of these very modestly sized trees, perhaps one hundred years.
Overall, of course, the Pacific Ocean itself was rising at no such rate, if at all. Rather, the land in this area was rapidly subsiding. The movement of tectonic plates was pinching and prodding and reconfiguring the entire Northwest Coast, dragging the land downward in some places, pushing it up in others. For me this was a graphic lesson that yanked regional sea level change out of the geological time scale of thousands or millions of years. Rising seas could change the location and character of the shoreline within a single lifetime, in what to geologists is the mere blink of an eye. A whole new element in coastal prehistory became real and relevant for me.
This was in the late 1980s, when just a few archaeologists were questioning the prevailing idea of how and when the First Americans arrived. Was it possible that the long-held theory that big-game hunters came from Asia by hiking across a dry land bridge at the Bering Strait just as the Ice Age waned wasn't really viable? Was it possible, instead, that seafaring people with boats came earlier and by way of the lost world that now lies under water along the North Pacific coast? Witnessing drastic and rapid sea level change for myself piqued my interest in this scenario. So I traveled, asked questions, wrote magazine articles on the subject and learned how, in the face of great obstacles, a few small teams of scientists in Alaska, British Columbia, and California were unraveling the mysteries of those flooded shores. The quest continues, but already the results have begun rewriting the prehistory of our continent.
Copyright © 2003 by Tom Koppel
Chapter OneCave of the Bears
"Watch your head," said paleontologist Tim Heaton, ducking as he led the way down into the fissure in the steep rock face, leaving the sunshine and warmth behind. It was cold, damp, and quiet. Underground, away from the droning of the big gasoline generator, there was only the barest murmur of seeping water. But we could see well enough. Thick electrical cables ran into the cave to a few lights that were strung along one side.
We were on Prince of Wales Island, Alaska, in the summer of 1999. The main chamber was tiny and cramped, only about ten feet wide, with a ceiling so low in places that we had to stoop. The rocky floor was wet and uneven, and the farthest nook was only about forty feet back from the entrance. Kneeling on the muddy floor of the chamber and scraping up dirt with a trowel was a slim young guy with a wispy black beard who turned to say hello. Kei Nozaki, from Japan, was one of the student assistants Heaton had brought up from the University of South Dakota for a season of fieldwork. Like us, Nozaki was wearing a caver's helmet and a rain suit over his clothes.
Off to the right, a second and much narrower tunnel sloped away into the shadows. "The cave branches here," said Heaton with the soft western twang of his native Utah. "This is what we call the 'Seal Passage,' because that's where we found so many of the seal bones. And it actually loops around and comes out at another entrance down the hillside a bit. It's got a tight little keyhole shape." I switched on my headlamp and flashlight and stepped down into the passageway to take a look.
Heaton wasn't exaggerating. The dank and constricted little gut had a symmetrical keyhole cross section all the way along the gentle downward grade to where it jogged out of sight maybe fifty feet away. From knee to head height the walls, glistening with moisture, had the shape of a round tube about three feet in diameter. Below that was a sort of lower extension, a slot barely wide enough to put one rubber boot past the other. This telltale keyhole shape resulted, Heaton explained, because initially, when the water table was high, a steady flow of ground water had dissolved the limestone over thousands of years, routing out a subterranean water pipe, a nearly perfect cylinder, what geologists call a "solution tube." At some later time, the water table dropped and water only flowed along the very bottom of the tube. This eroded the rock straight down from the center and carved out the lower part of the keyhole. Much of the limestone on the island, and elsewhere on the southeastern coast of Alaska, was riddled with similar tubes and passages. Some of the caves penetrate entire mountains and have never been fully explored -- a caver's dream.
I figured I would make my way down the length of the seal passage and have a look at the other entrance, but it was so hard to squeeze one foot past the other in the tight slot that I soon had second thoughts. And then I discovered that I couldn't turn around. I was stuck in an awkward crouched position, with cold, slimy stone walls hemming me in on both sides. Being trapped in a mine or buried alive has always been one of my pet phobias. Little fingers of fear crept up my spine, even with Heaton right there, close behind. No, I decided, I did not really need to inspect the other end of that dark, narrow tunnel. I was forced to back my way slowly out and exhaled with relief when I was back in the main chamber.
Heaton chuckled at my discomfort. "I'm used to working under the adverse conditions of caves," he said. "This is my third big excavation on the island." He had done a lot of sport caving as a teenager in Utah -- even meeting his wife Julie at a caving club there -- and still went caving occasionally just for fun. His other hobby was being a ham radio operator. And, at about forty, he was in terrific shape: tall, lanky, and built like a marathon runner.
For Heaton, the difficulty of working in this accessible, relatively level cave was nothing. "There's one cave here on the island where you have to go headfirst down a tight vertical crawlway, which emerges at the top of a 150 foot cliff." Other caves have underground lakes and flowing rivers. There are tight spots where you have to take off your jacket to squeeze through; if you get stuck, nobody can help you. And if the battery-powered headlamp goes out, everything dissolves into stygian blackness. "I do some pretty hefty caving to get at some of the bones. Cave paleontology is a specialty. Even most paleontologists are not used to it. They'd get claustrophobic crawling through these muddy holes," he laughed.
But it's a handy skill to have in his profession. "There's lots of bones in caves." For one thing, animals can find shelter in caves, and those that hibernate, such as bears, use the caves as dens in winter. A big bonus for paleontologists is the excellent preservation of bones, teeth, antlers -- anything made of calcium -- in the alkaline environment of a limestone cave. "Bone doesn't preserve too well outside," said Heaton, pointing to the entrance. "You have the temperature and humidity fluctuations, and the acidity of the forest soil, but as you get inside, the bones become better and better preserved, and more common."
The main chamber where Nozaki was digging was called the "Bear Passage." It was a few bear bones Heaton had discovered years earlier, and the totally unexpected information they provided, that initially made this little cave more interesting to him than the many larger and more physically impressive ones on the island.
But it wasn't bear bones that had brought me here from my home in British Columbia; it was human bones and artifacts.
We went back out into the August sunshine, and Nozaki joined us for a break and to warm up from the chill of the cave's interior. Heaton shut down the generator, and we sat to talk among the fuel drums, buckets, hoses, and other clutter of the work site. We were on a south-facing slope in virgin forest of big hemlock and spruce. Heaton took off his helmet and ran his hand through closely cropped red hair. With the sun in his face, he warmed to the quirky tale of how this remote bear den with the official federal designation 49-PET-408 had become one of the most important ancient archaeological sites in North America.
And he might never have even inspected it if it hadn't been for the weather.
In July 1994 Heaton was back on Prince of Wales Island for the fourth time in as many summers. Its caves were proving to be a fossil gold mine, helping him to unravel the complex story of how and when bears first inhabited the Alaska coast. He was one of two paleontologists, plus geologists, biologists, and enthusiastic amateur cavers, who were exploring and mapping the recently discovered cave system with active sponsorship from the local U.S. Forest Service geologist in charge of the vast Tongass Forest District, Jim Baichtal. Major areas of the huge island, the third largest in the United States, were being logged. In fact, it was the logging that had exposed the entrances to many of the caves. But the Forest Service was willing to postpone the clear-cutting in places where caves were being surveyed, and the Feds provided the Tongass cave project with housing, meals, and transportation.
Heaton's plan that year was to spend only a couple of weeks on the island. His target was a high-elevation site called "Bumper Cave," which ran sixty-five feet back from the entrance in sparse subalpine forest high on the flanks of Calder Mountain, a bald rocky dome that loomed over the island's far north end. I had flown past this stark summit early that very morning in the stolid old Beaver float plane that brought me out from Ketchikan to Port Protection, population fifty. There were no roads connecting the settlement to the rest of the island, and no post office, either. Just a dock, a store, a little lodge, a fish plant, and a scattering of houses, all clinging like limpets to the rocky shore of a tiny sheltered cove.
Jim, a chunky, bearded guy, helped me unload my gear from the plane. Like a few other people who were hanging out on the dock, Jim fished a little for salmon with the small commercial fishing boat that was also his home for the summer. Come winter, he drove a taxi in New York City.
To get from Port Protection to 49-PET-408, I hired a lanky fellow named Bud, who was missing a few teeth and had gray hair that reached halfway down his back. He told me that he had moved up from the Lower Forty-Eight in 1972. He made ends meet mainly by cutting lumber for people with a small, portable sawmill, and collected old stone artifacts off the beaches as a hobby. We had to cruise a few miles around a jutting peninsula in an aluminum skiff with a sputtering outboard. Along the way, Bud took a slight detour to show me his favorite spot for finding ancient adzes and daggers made of a greenish stone, presumably by the Tlingit Indians before they first had contact with the Russians and other Europeans in the 1700s. The tide was low and, sure enough, dozens of sharp flakes of green-gray rock were lying among rounded cobbles near some grounded boom logs that were linked together by massive rusty chains. I was skeptical about some of the pieces of stone that he claimed were artifacts, but Bud just smiled knowingly. "Here," he said. "You're going to the cave. Show these to the archaeologists and see what they say." It turned out that he was right.
Bud dropped me off at a gravel beach that was tucked in behind a tangle of kelp. There was a little cluster of brightly colored tents in a sheltered spot above the beach, and just enough room for me to set up mine. But no one else was around; they were all up at the cave, working. From the beach campsite to the cave was a half hour's trudge through dense forest along a steep, muddy trail that climbed more than 400 feet from sea level. For safety, Heaton and his crew had rigged some of the nearly vertical rock faces with knotted ropes. I was panting and sweating by the time I reached the site. It was a hike that I would make morning and evening for the next five days.
Back in 1994, though, Heaton had no intention of hiking that mile-long trail; in fact, it did not exist yet. He and a colleague had assembled the equipment for their expedition up to Bumper Cave, including camping gear and food for at least ten days. They were even bringing along 1000 feet of fire hose, enabling them to run water from a stream to wash and screen the sediment from the cave for any tiny animal bones they might miss at first glance. Kevin Allred, the Alaska-based leader of the cave project, had discovered and mapped Bumper Cave the previous summer, and had regaled Heaton with the juicy details. It was just littered with bear skeletons, he said, probably seven or eight in all, some of them exquisitely preserved. Millennia-old bones from other caves on the island had already overthrown some long-held assumptions about the Ice Age distribution and migrations of both black bears and grizzlies. Heaton was excited by the prospect that Bumper Cave might round out the new and emerging picture.
But his arrival on the island coincided with the long Fourth of July weekend, which grounded the Forest Service helicopter that was to take him and his gear up the mountainside. Baichtal, the geologist, had arranged for him to stay at a Forest Service camp that was the cave project's home base. With comfortable old wooden bunkhouses and separate buildings for cooking and showers, all overlooking a sheltered arm of the sea, this was not exactly a hardship post. But then the coastal weather closed in, and the helicopter could not fly. Day after rainy and foggy day, Heaton was forced to wait, cooling his heels at the camp, a frustrating thing for a guy who hates to waste a moment.
Waking one morning to see the trees shrouded yet again in mist, he and Allred decided to take a side trip to another cave on the island's extreme northwestern tip that Allred had visited the year before. Allred had heard about it from a Forest Service surveying crew, who first noticed the dark opening in the hillside when they hiked through to plot out future logging roads. The cave's ceiling was so low that the initial designation 49-PET-408 eventually gave way to the moniker "On Your Knees Cave."
Allred and two colleagues had crawled through with their compass, inclinometer, and tape measure back in 1993. Later, they made a scale drawing for the cave project's files, and that might have been the end of it, except that they also noticed some animal bones, in particular the well preserved skeleton of a river otter. When he heard about it from Allred the following summer, Heaton wondered what else the cave might hold.
With the helicopter grounded, Heaton and Allred drove to the end of the main logging road and hiked through the woods out onto a peninsula called "Protection Head." The cave didn't look like much. Inside, it was as Allred had described it. There was the river otter, which was interesting. Gee, imagine an otter coming all this way up from the sea, Heaton said to himself. And there were a few larger bones lying exposed right on the surface. One of them, he thought, was the femur of a grizzly bear. This wasn't a surprise to Heaton. Grizzlies did not inhabit the island in modern times, although black bears did. And though it used to be thought that grizzlies never had, Heaton had been finding the bones of both grizzlies and black bears in many of the caves for years now.
Heaton put the visible bones into plastic bags, labeled them, noted their locations in his notebook, and returned to the Forest Service camp. Eventually the weather cleared, the helicopter took him and his partner up to Bumper Cave, and they collected a wealth of bear bones, which later proved to be from 7,200 to 11,600 years old. It was a highly successful, if short, season. As for On Your Knees Cave, Heaton wrote it off as having much less paleontological interest than many of the other caves on the island. All he had found, after all, were the otter skeleton and a few more bear bones.
His verdict would change drastically a few months later. He had sent off a minute sample of the grizzly bear femur to a specialized laboratory for carbon dating. The lab isolated perhaps a thousandth of a gram of bone protein, called collagen, and sent it on to a nuclear laboratory equipped with a high-energy linear accelerator linked to a mass spectrometer. By what is called accelerator mass spectrometry (or AMS) dating, individual ions of the radioactive carbon isotope, carbon 14, were counted. The results went back to the first lab for analysis.
Back in South Dakota, Heaton eventually received a carbon 14 date of 35,000 years for the bear femur, or three times as old as the oldest bear bone previously found on the island. This placed it well before the peak of the last glaciation. Bones from the other caves already showed that bears had inhabited the island in the final, waning years of the glaciation, around 12,300 years ago. Was it possible that they had survived there right through the most recent advance and retreat of the great ramparts of ice, from about 25,000 to 10,000 years ago? If so, the area was a glacial refuge, a sizable haven of life on the outer edge of what was for many millennia a largely sterile, frigid, and icebound coast.
These findings ran entirely contrary to what biologists and geologists had been saying. Most thought that the entire coast of southeastern Alaska, including the islands like Prince of Wales, had been smothered by ice, leaving no such refuges. In 1965, biologist David Klein undertook a study of mammal distributions in the islands of southeast Alaska and had proclaimed unequivocally: "During the [most recent] glaciation the present land areas of the coastal regions...were virtually completely overridden by ice. The now existing flora and fauna of the region have presumably become established in the 10,000 years since the recession of the ice." For decades, this remained the authoritative view.
Recently, though, a few scientists had begun to wonder. Even Heaton's earlier finds of bears dating to the very end of the Ice Age, from 10,000 to over 12,000 years ago, were a significant clue. Jim Baichtal had told the journal Science, "If bears were living here, then chances are pretty good that we were not overridden by a blanket of ice as the textbooks have been telling us."
And there was other evidence that pointed to the existence of Ice Age refuges. Grizzlies still inhabited islands farther north along the coast of Alaska. Several studies of their DNA by Gerald Shields and his colleagues at the University of Alaska showed that these grizzlies were more closely related to polar bears than to any other currently living bears, including other grizzlies that still inhabited the adjacent mainland of Alaska. And this affinity was despite the fact that the intervening channels were not too wide for the bears to swim across. This suggested that the offshore grizzlies had spent a very long time evolving in genetic isolation. Polar bears, in turn, were thought to have evolved from brown bears, the genus to which grizzlies belong, probably on the Siberian coast. The most likely explanation for this overall pattern was that the offshore Alaska grizzlies had been cut off from contact with other grizzlies during the last glaciation in a coastal refuge, or refugium, as the scientists like to call it. And it would have to be quite large to support a separate breeding population of bears. Now, thought Heaton, the bones from On Your Knees Cave might be telling a similar story.
Heaton had already tossed ideas back and forth with a few geologists and archaeologists who thought there might have been an entire network of such offshore refuges along the North Pacific coast. He realized that the northwestern tip of Prince of Wales Island had not likely been a tiny, isolated pocket of ice-free land. To the west and north of Prince of Wales Island -- and therefore farther away from the mainland coast with its massive ice sheet -- were other very sizable islands. If the tip of Prince of Wales had been beyond the reach of the ice, major parts of those other islands would probably have been ice-free as well.
Although the Cordilleran ice sheet may have been a mile or more thick where it blanketed the higher mountains of the mainland coast, at its outer edges to the west it would have thinned significantly, and as it advanced it would have split into separate glacial flows that followed the paths of least resistance. So it would be wrong to picture a monolithic wall of ice fronting the sea, like the vertical blue cliffs of an ice shelf on the coast of Antarctica. What reached out among today's coastal islands to the then-lower sea level on the continental shelf would have been massive snouts of grimy gray ice, oozing their way downhill under the force of gravity like stiff molasses. Where there were mountains or high ridges on the islands, these frozen rivers, propelled by the weight of ice behind them at higher elevation on the mainland shore, would have followed the deeper channels between the islands to grind opportunistic paths around the obstructions. And, because of lowered Ice Age sea level, there would also have been land beyond those islands that blocked the glacial flow, out on the gently sloping continental shelf. This land is now under water. At the peak of the glaciation, though, it would have been dry and quite habitable.
Tom Ager of the U.S. Geological Survey (USGS) has been systematically tracing the glacial flows through the archipelago of southeast Alaska and pinpointing these formerly exposed areas of land on bathymetric charts. To the west of Dall, Coronation, and Baranof Islands, says Ager, there were a number of distinct glacial refuges, a few of them hundreds of square miles in size.
To Tim Heaton, all of this suggested that along with the bears, people might have lived in the area as well. If these people had camped, fished, and hunted on the shores of an extensive glacial refuge, much of their prime territory would be under water today. But the cave could have acted as a magnet to draw them inland and uphill to hunt the denning bears, so it might offer the best chance to find traces of these early coastal dwellers. If, that is, people were actually on Prince of Wales or neighboring islands back in Ice Age times. Heaton was excited at the prospect of making a discovery that could overturn some of the most strongly held and long-established ideas about North American prehistory. He could hardly wait for the next summer, to get back to On Your Knees Cave and investigate further.
It would be two years before the human story of On Your Knees Cave began to unfold. And when it did, it went a long way to unravel the secrets of the late Ice Age coastal world.
But not all the pieces of the puzzle would come from the efforts of a lone paleontologist gathering bones in an Alaskan cave. Some would be dredged from the sea floor by a research ship in the Queen Charlotte Islands of British Columbia, a few hundred miles to the south. The bones of an extinct mouse species on an island off California would offer mute testimony about when an Ice Age woman died in a swampy canyon. Important information would come from a geologist who determined the length of time that a line of erratic boulders hundreds of miles long had been exposed to the sky. Other pieces of evidence, including razor-sharp microblades of volcanic glass, would be unearthed by young Tlingit and Haida Indians, the likely descendants of the very ancient people who left those artifacts behind.
It was a heady experience for those involved in the search. They knew that what they might find could revolutionize our most fundamental self-image. For we have been accustomed to thinking of ourselves as a species in terrestrial terms: evolving in the savanna of Africa; hunkering in caves in Europe; gradually spreading overland through Asia; and finally trekking dry-shod across a land bridge at the Bering Strait into the Americas while preying upon big Ice Age animals. But if the scientists on the Pacific coast were right, we also became bold seafarers at a very early date, maritime people who built boats and braved the stormy and icebound shores of the North Pacific. And we lived not just from hunting mammoths and huge bison, but also from spearing sea mammals, from fishing, and from gathering shellfish and seaweed. This would be quite a different picture, yet one that is just as heroic and compelling.
Copyright © 2003 by Tom Koppel