Canada

Mammoth Discoveries

FOOTPRINTS LEFT 13,000 YEARS AGO ARE LEADING THE WAY TO A NEW VIEW OF ANCIENT HISTORY

BRIAN BERGMAN July 16 2001
Canada

Mammoth Discoveries

FOOTPRINTS LEFT 13,000 YEARS AGO ARE LEADING THE WAY TO A NEW VIEW OF ANCIENT HISTORY

BRIAN BERGMAN July 16 2001

Mammoth Discoveries

Canada

BRIAN BERGMAN

near the Alberta-Montana border

Brian Kooyman smiles and shakes his head in amazement. The University of Calgary archeologist has just pointed out two sets of woolly mammoth tracks perfectly preserved in the sands of St. Mary Reservoir, here in a remote corner of southwestern Alberta. One set of manhole-sized footprints indicates an adult mammoth, with a smaller set beside it suggesting an offspring in tow. The tracks are heading southwest towards Montana’s snow-tipped Rockies, which loom in the distance just as they would have when these footprints were first made, 13,000 calendar years ago. “It’s incredible, isn’t it?” says the affable Kooyman, who exudes a child’s enthusiasm wrapped in

a middle-aged man’s lanky frame. “It’s like I can see these animals lumbering along.”

Kooyman is part of one of the most intriguing archeological digs now under way in North America. The mammoth tracks— along with similar footprints left by ancient camels, horses, bison and caribou—are providing scientists with some of the best visual information yet on how such animals interacted on the western plains at the twilight of the last ice age. Skeletal remains of pony-sized horses and hunting artifacts recovered at the site are also revealing new clues as to the role man may have played in the extinction of the various species. Finally, the cumulative evidence being gathered from this windswept terrain promises to add to the growing consensus among scientists that early humans entered the New World by a different route-—and perhaps much earlier—than previously thought.

But beyond all that, perhaps the most fasci-

FOOTPRINTS LEFT 13,000 YEARS AGO ARE LEADING THE WAY TO A NEW VIEW OF ANCIENT HISTORY

nating aspect of the Alberta digs is the unusual set of circumstances that led to these animals’ massive footprints being made, preserved and ultimately exposed. Though barren now, the area Kooyman and his colleagues—veteran geologist Len Hills and University of Calgary graduate students Paul McNeil and Shayne Tolman—are exploring would have boasted rich grasslands when the animals roamed here. Most of the surviving tracks were made near a broad floodplain of what is now the St. Mary River, where the soil was more exposed and wet. The animals’ feet compacted the ground they stepped on, making the tracks more resistant to erosion. Still, in the normal course of events, the tracks would have disappeared in a matter of days as the area dried up. Instead, the region’s high winds—-which have been clocked at up to 170 km/h—blew sand and silt off the floodplain, which quickly accumulated over the footprints at levels of up to 50 cm, protecting the tracks from any further erosion.

Fast-forward 13 millennia. During that time, the soil covering the tracks gradually built up by about two metres, topped by a layer of vegetation. Then, in 1950, the Alberta government dammed the river near this spot, creating a reservoir to provide irrigation for local farmers. Filling the reservoir killed the vegetation, removing the protective mat that helped preserve the footprints. Periodically, as the reservoir was drained, for irrigation purposes, the surface area became vulnerable again to the high winds, which, over time, stripped away layer after layer of sediment. In the mid-1990s, the erosion accelerated as the province drained the reservoir to construct a new spillway. Eventually, enough of the sediment was removed to make the tracks visible to the human eye.

Enter Shayne Tolman. An elementary schoolteacher from nearby Cardston, Alta., and a longtime prehistory buff, Tolman was taking his young sons for a walk along the

drained-out reservoir site on the May long weekend of 1996 when he came upon what appeared to be an ancient native spearpoint. On subsequent visits, he found other points, as well as what looked like a chunk of an animals skull (it turned out to be an ancient bison). Through a friend, Tolman made contact with Hills and Kooyman and, together, they later discovered the animal tracks.

Hills contacted McNeil, a student of his who was then working on a PhD thesis in paleontology. “He told me he thought he had mammoth tracks,” recalled McNeil one recent afternoon at the reservoir site as he carefully dug around a set of horse and bison tracks he planned to take back to Calgary in a plaster jacket for further study. “I was very skeptical. He said, ‘I took some pictures but they didn’t turn out,’ which is, of course, the oldest story in the book. So I came down to look and I saw these massive footprints. It took me about two seconds to say, ‘Wow, you’ve got mammoth tracks.’ I didn’t remain a skeptic for very long.”

Once the scientists trained their eyes to see the footprints, they found thousands of them, including those made by other animals, such as camels and small horses, all of which had gone extinct in North America by 11,000 years ago. While several archeological sites have yielded physical remains of these animals, here were the first visual clues to how they might have moved and interacted.

Many of the individual adult mammoth tracks, for example, are set up to three metres apart, indicative of the creature’s majestic stride. At other spots, overstepping tracks of mammoths, camels, horses and bison suggest they coexisted at the same place and time. “It’s exciting to imagine what it must have looked like here,” says McNeil. “I think it might have been something like you would see out on Africa’s Serengeti Plain today.”

Scientists have long believed that one of the major factors in why certain animals disappeared from North America was climate changes that occurred at the end of the last ice age. As the glaciers receded northward, much of the cold-adapted vegetation the animals fed upon became more scarce. New plants appeared, but the di-

gestive systems of many animals failed to adapt and they grew progressively weaker.

But scientists have also long speculated about what role hunting played in the animals’ demise (Spanish conquistadors reintroduced horses to the Americas in the 16th century). In the case of the horses, the digs at the St. Mary Reservoir are providing some of the first solid evidence that hunting was at least a contributing factor. Team members unearthed a horse skeleton with several of its vertebrae smashed and what appeared to be butcher marks on a number of its bones. Not far away, they found some 13,200-year-old Clovis spearheads; foren-

sic tests later confirmed horse protein residues on two of the weapons. “So all of the pieces,” says Kooyman, “are falling together.”

In fact, the Alberta discoveries appear to dovetail with research published last month in the journal Science, by John Alroy, a University of California evolutionary biologist. Alroy has developed a computer model that attempts to simulate the impact early man’s arrival had on the animals. No matter how he crunches the numbers, Alroy finds that shordy after humans appear, giant herbivores like the mammoth are driven to extinction. Kooyman says that appears consistent with his team’s findings. But he cautions against seeing hunting as the sole factor in the animals’ demise. “Humans contributed to the stresses the ani-

mals were under,” he says. “But there’s no way a small group of hunters could have been primarily responsible for extinction.” The St. Mary digs also promise to contribute to the ongoing debate over exacdy when—and how—early humans came to the New World. Until recendy, the conventional wisdom said that, about 14,000 years ago, big-game hunters from Siberia followed mammoth and caribou on a land bridge across what is now the Bering Sea to Alaska, then continued southward along a corridor opening between the glaciers. But there is now a growing consensus that humans travelled by foot or boat down the west coast of the Americas about 13,000 years ago and worked their way inland. Kooyman says the early evidence from the reservoir site is suggestive of humans moving northward to hunt animals they were familiar with from south of the ice sheets—a migration pattern that would seem to support the west-coast-route theory of how humans first arrived.

There will be plenty of time to sort out such puzzles. The St. Mary digs, which began in 1998, promise to go on for many years yet. Because of the seasonal filling of the reservoir, excavation work is confined mostly to the winter and spring months. It is also hampered by winds that whip up sandstorms so severe team members standing a metre apart cannot see each other. But already, the project has had a profound effect on those involved. Hills took early retirement from the University of Calgary in 1996, intending to catalogue work from some 15 summers he spent at digs in the Canadian Arctic. That has now taken a backseat to the reservoir discoveries. McNeil has switched his PhD thesis from dinosaur locomotion to ancient mammoths and horses. Tolman took a sabbatical from his teaching job to indulge his first love—fossil hunting—and is pursuing a master’s of science degree.

And Kooyman? The bearded, quicksmiling archeologist is simply happy to be following in the footsteps of the ancients right in his own backyard. “Opportunities like this don’t come around very often,” he enthuses. “I feel I’m a very lucky man.”

THE SITE PROVIDES THE FIRST CLUES TO HOW ANCIENT ANIMALS INTERACTED