Tracking Ursus arctos

[Jacques Cinq-Mars]

All,

Nothing particularly palaeoanthropological about the following note, that is, unless one is capable of reading human tracks alongside those of the interpleniglacial migrating bears. Needless to say, I am eagerly waiting for my copy of the paper.

Ancient bear made early migration

BBC NEWS --Friday, 12 November, 2004, 12:54 GMT

Brown bears migrated south through Canada much earlier than first thought, Science magazine has reported.

The bears reached Alaska about 50,000 to 100,000 years ago, after crossing a land bridge from Asia.

But, according to traditional wisdom, thick ice blocked their route into Canada until roughly 13,000 years ago.

Now new fossil evidence suggests brown bears actually made their way through Canada more than 25,000 years ago, well before ice sealed their path.

Fossilised brown bear fragments dating back about 25,000 years have been uncovered in Alberta, Canada, for the first time.

The remains prove that brown bears must have made it through into mainland Canada before heavy ice closed the corridor from Beringia about 23,000 years ago.

Beringia is the name given to a land bridge that emerged periodically to connect Asia and America.

"This is the first fossil to be found in the region that is older than 13,000 years old

The find is particularly important because it clears up some niggling inconsistencies in the history of brown bears.

Frustrating task

Unravelling their past movements has been a frustrating task for researchers. Until now, it has been a tale that just did not add up.

There is clear evidence that bears crossed between Asia and North America on a temporary corridor of land called Beringia. They continued to live in the region of Beringia until about 35,000 years ago.

Bears reached North America about 50,000 to 100,000 years ago
But, until now, the fossil record suggested they did not venture any further south for thousands of years. Palaeontologists hunting for bear fossils in Canada and the USA came up with nothing older than 13,000 years old.

"Because people did not find any fossil remains older than 13,000 years old, they assumed that the bears had not migrated south," explained Dr Weinstock.

But the theory that the bears stayed in Beringia was never completely satisfactory.

Firstly, ice did not clog up the route until about 23,000 years ago, so they had a clear passageway south for many thousand years.

Secondly, the genetics of modern brown (grizzly) bears living in southern Canada make the traditional theory particularly unconvincing.

Puzzle

These grizzlies are apparently all descended from a particular clade of brown bears, called clade four.

Mitochondrial evidence shows that clade four bears were present in Beringia before 35,000 years ago. But then they disappeared from the region, along with all other clades of brown bear.

When the bears recolonized Beringia from Asia about 21,000 years ago, clade four was not among them. So the bears pushing south from the region when the ice cleared 13,000 years ago, did not contain the ancestors of modern bears living in southern Canada.

If this was indeed the first major migration south, scientists found it very hard to explain how all modern grizzlies in southern Canada could have been descended from clade four.

The new evidence clears up the problem, because it suggests clade four bears were already in Canada when the ice closed the access route 23,000 years ago.

However, they apparently did not venture very far south for a long time, which explains why the early fossil record is thin.

"Once they arrived in Canada they did not migrate further south for some reason," said Dr Weinstock. "They lived just south of the ice in what was probably quite a small population.

"Nobody quite knows why they did not move south. It could be that food was not available, but we just don't know. It is very strange."

For the original text with some pretty bears (bones), click HERE

Also, note that the downloadable “SUPPORTING ONLINE MATERIAL”, does contain interesting information. It can be accessed by clicking HERE

Jacques Cinq-Mars

[Jacques Cinq-Mars]

All,

For your information/records, here is the initial University of Alaska – Fairbanks release on the recent Science “brown bears” paper.

Jacques Cinq-Mars

Ancient fossil offers new clues to brown bears past.

Submitted by Carla Browning
11/11/04
Phone: (907) 474-7778

While nosing around the Quaternary mammal collection at the Provincial Museum of Alberta two years ago, Paul Matheus, a paleontologist with the Alaska Quaternary Center, came across a brown bear fossil that seemed out of place. The fossil had been collected by Jim Burns, curator of Quaternary mammals at the PMA a few years earlier near Edmonton, Alberta, in gravels that date to before the last ice age (older than 24,000 years). If this was true, Matheus thought, it could be a very important find. Burns loaned the specimen to Matheus so he could take it back to the University of Alaska Fairbanks to confirm its age using radiocarbon dating methods. Results showed the bear was indeed about 26,000 years old, and the two researchers realized the fossil's signficance-the history of brown bears in North America would have to be rewritten.

The ancestors of modern brown bears in North America are believed to have migrated from Asia to Alaska and Yukon (then a part of Beringia) between 50,000 and 100,000 years ago, and old brown bear fossils are not particularly uncommon in Beringia. Between roughly 13,000-23,000 years ago, the route from Beringia to areas of the continent further south was blocked by continental glaciers, so brown bears were more or less bottled up in Beringia. The oldest brown bear fossils south of Beringia, in areas like southern Canada and the northern U.S., are about 12,000-13,000 years old, so paleontologists concluded that's when they first arrived.

"It's always been a mystery, though, why brown bears didn't migrate farther south if they were in Beringia as early as 100,000 years ago and the passage south wasn't blocked by glaciers until about 23,000 years ago," said Matheus. "The discovery of the Edmonton specimen indicates that brown bears migrated south much earlier than previously thought."

The recent findings and their implications, are the subject of an article in the Nov. 12 issue of the journal Science titled Pleistocene Brown Bears in the Mid-Continent of North America.

In order to really nail the significance of the find, Matheus and Burns needed one more piece of important information-they needed to know something about the fossil brown bear's genetic identity. So, they brought in colleagues from the University of Oxford and the Max Planck Institute in Germany to sequence mitochondrial DNA from the specimen and assign the bear to one of the known genetic populations of modern and ancient brown bears. This was possible because of a previous collaborative study by Matheus and the Oxford lab using ancient DNA to uncover the population structure of ancient brown bears in Beringia.

"One thing that earlier study could not explain was the ancestry of modern brown bears in the southern part of their range, in places like southern Alberta, British Columbia, Montana, and Idaho," said Matheus. "Those bears belong to a genetic population thought to be extinct in North America for as much as 35,000 years."

Consequently, paleontologists and geneticists have found it difficult to explain where the ancestors of southern brown bears came from when ice sheets retreated about 13,000 years ago-their genetic type did not exist in Beringia at that time. DNA results in the current study show that the new Edmonton specimen belongs to the same genetic group as modern southern brown bears.

The age and genetic identity of this bear mean that brown bears not only made it far south sooner than previously thought, but that those bears in the Edmonton area about 26,000 years ago were very close relatives of southern bears we see today.

"Its like finding a missing piece of a puzzle, or even a proverbial missing link," said Matheus. "Their ancestors must have been stuck south of the ice sheets at the peak of the last ice age, 13,000-23,000 years ago because Edmonton was covered with ice most of that time. That represents a real shift in ideas about brown bear evolution in North America."

Matheus is a research scientist at the Alaska Quaternary Center and a research associate at the Institute of Arctic Biology. Both are located on the University of Alaska Fairbanks campus.

CONTACT: Paul Matheus, at (867) 456-7551, or e-mail ffpem@uaf.edu or contact Carla Browning at (907) 474-7778 or carla.browning@uaf.edu for additional contact information.

[Jacques Cinq-Mars]

All,

And then, there is this National Geographic News piece which ends with a brief allusion to the possible implication(s) this interpleniglacial “brown bear” story might have with regards to our understanding of the timing of early human dispersal(s) in the New World.

Jacques

Brown Bears Moved South Before Ice Age, Study Says

Stefan Lovgren
for National Geographic News
November 11, 2004

A fragment of a bear skull housed for several years in a Canadian museum may be rewriting the history of North America's brown bears.

Scientists say the skull, which was retrieved from a gravel pit in central Alberta in 1997, is at least 25,000 years old.

The finding suggests that brown bears, having crossed the Bering Strait from Asia, must have ventured south, deep into North America, far earlier than previously thought.

The discovery also sheds light on the ancestry of modern brown bears. A genetic analysis of the skull fragment indicates its owner was closely related to the brown bears that inhabit southern Canada and the northern United States today.

"It's like finding a missing piece of a puzzle," said Paul Matheus, a paleontologist at the Alaska Quaternary Center at the University of Alaska in Fairbanks. Matheus is the lead author of the report, which is described in this week's issue of the journal Science.

Ice-Free Corridor

Based on the fossil record, researchers say brown bears migrated from Asia to the edge of North America between 50,000 and 100,000 years ago. However, ice sheets were believed to have prevented the predators from moving beyond Alaska and Yukon, then a part of Beringia. (A land bridge formed during the last ice age, Beringia joined Asia to Alaska and northwestern Canada.)

About 13,000 years ago, an ice-free corridor opened up, allowing brown bears to travel south. Until now, the oldest brown bear fossils in southern Canada and the northern United States were about 13,000 years old, an age paleontologists equated with the bears' arrival.

However, continental glaciers only blocked the route south between roughly 23,000 and 13,000 years ago.

"This has always been a mystery," Matheus said. "If brown bears came over to eastern Beringia at least 50,000 years ago, why didn't they go all the way down if there was no ice blocking their way?"

The new skull discovery suggests that brown bears actually did make that journey before the ice sheets arose.

Genetic Testing

Matheus found the specimen by chance two years ago while nosing around the Provincial Museum of Alberta in Edmonton. It was one of many fossils collected from gravel pits in the area by Jim Burns, a curator at the museum.

"I looked at a collection of bones older than 23,000 years and found the brown bear fossil," Matheus said. "I wondered, What is that doing in here? It shouldn't be here."

Radiocarbon dating indicated the bear was about 26,000 years old. "We had brown bears much further south much earlier than they should be," the paleontologist said.

One thing Matheus and his colleagues at England's Oxford University were unable to explain very well during an earlier study was the ancestry of modern brown bears in southern Canada and the northern United States. This discovery appears to solve that problem.

Genetic testing by scientists at Oxford and the Max Planck Institute in Germany showed that the Edmonton skull fossil belongs to the same genetic group as modern southern brown bears.

"It's a nice finding, because it filled in a gap in the records that was kind of puzzling," said Blaire Van Valkenburgh, a paleobiologist at the University of California at Los Angeles. "It makes more sense that the brown bears would have been south of the ice [25,000 years ago]."

"The results also indicate that the southern bears are very distinct from Alaskan bears," she added.

Human Migration

The new findings may also raise new questions about when—and how—the first humans migrated into the New World.

For decades many archaeologists have argued that humans migrated south of Beringia via an ice-free corridor about 13,000 years ago, when the ice sheets began to recede.

These scientists used the first appearance of certain animals, such as the brown bears, as a proxy indicator for when this corridor may have been available to humans.

"But our results show that brown bears were down further south much earlier, and that we just hadn't found the oldest fossils yet," Matheus said. "Archaeologists can no longer use brown bears as a test for when the first humans came south."