News / Science & Technology

Polar Bear Fossil Traces Origin to Brown Bears

A scientific analysis of a rare polar bear fossil indicates that the large, white-coated mammals evolved in the relatively recent past from common brown bears.  The discovery suggests polar bears' ancestors migrated toward the North Pole in response to global warming thousands of years ago, and adapted quickly to their new Arctic habitat.

Scientists analyzing the rare fossil, found in Norway's northern Svalbard islands in 2004, conclude that polar bears appear to have evolved from brown bears 150,000 years ago  - a mere blink of an eye on the earth's geological  timeline.  
 
The genetic evidence comes from an unusually well-preserved polar bear jawbone with a canine tooth still attached to it - a rare find because most polar bear carcasses are consumed by scavengers or sink to the sea bottom.  The DNA mapped from the jawbone is the earliest mammalian genome ever sequenced.

Researchers have long suspected that the arctic-dwelling animals evolved from brown bears because of their present-day genetic similarities.  But scientists could not confirm an evolutionary timeline.   Estimates of the origins of polar bears have ranged all the way from 150,000 years ago to one million years ago.   But a comparison of the DNA in the polar bear fossil and in a group of modern brown bears living on a group of islands off the Alaskan coast showed the two genomes more closely related than they are today.

The researchers were able to estimate that the polar bears' ancestors branched off from the brown bear population when they headed north and adapted to the Arctic habitat, becoming a separate species about 150,000 years ago.

Charlotte Lindqvist, an evolutionary biologist at the University of Buffalo in New York, led the research.  Lindqvist says the fossil appears to be that of an adult male approximately the same size as modern polar bears.

"We found that it probably had a diet similar to polar bears today.  And from the stratus [sic] [stratum or layers of rock or sediment] from where the fossil was found, we can see that it lived in an environment probably similar as today," she said.  "So, this means that very rapidly polar bears probably adapted to a habitat very similar to what we see today," she added.

Lindqvist and colleagues theorize that one reason for the migration of brown bears to the Arctic may have been to escape the interglacial warming of the late Pleistocene period.

It's possible that Svalbard, where the fossil was found, served as a refuge for bears attempting to survive rising temperatures during this climate change, according to co-researcher Stephan Schuster of the University of Pennsylvania Center for Comparative Genomics.

"It is questionable how they would survive this, and I think the most logical scenario would be that they were following the cold weather," said Schuster.  "And Svalbard would have been this kind of environment, where the polar bears could have gone and survived this warming period," he said.
 
Even today, notes the University of Buffalo's Charlotte Lindqvist, brown bears have been spotted wandering into areas considered to be polar bear habitats in the Canadian Arctic, suggesting that current warming trends may once again be impacting brown bear populations.

Lindqvist and her research team plan further genetic analysis of the polar bear fossil, which should yield clues about the migration routes taken by brown bears to the Arctic and the bears' rapid adaptation to the polar environment.
 
Additional studies could also tell researchers at what point during its evolution the polar bear developed its white coat, which Lindqvist says is actually colorless but looks white against the snowy landscape.

"By recovering more of the genome, we may be able to answer more questions about their evolution and their origin and how they adapted to their current habitats.  And perhaps something about how they may be able to adapt to future changes," said Lindqvist.

An international team of researchers described the polar bear fossil in the Proceedings of the National Academy of Sciences.

You May Like

Photogallery Kyiv: Russian Forces Tightening Grip on East

And new United Nations report documents human rights abuses committed by both sides in conflict More

Locust Swarms Fill Antananarivo Skies

FAO-led control efforts halted plague More

South Africa’s Plan to Move Rhinos May Not Stop Poaching

Experts say international coordination needed to follow the money trail and bring down rhino horn kingpins More

This forum has been closed.
Comments
     
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Ebola Vaccine Trials To Begin Next Weeki
X
August 29, 2014 2:18 AM
The National Institutes of Health says it is launching early stage trials of a vaccine to prevent the Ebola virus, which has infected or killed thousands of people across West Africa. The World Health Organization says Ebola could infect more than 20,000 people across the region by the time the outbreak is over. The epidemic has health experts and governments scrambling to prevent more people from becoming infected. Zlatica Hoke has more.
Video

Video Ebola Vaccine Trials To Begin Next Week

The National Institutes of Health says it is launching early stage trials of a vaccine to prevent the Ebola virus, which has infected or killed thousands of people across West Africa. The World Health Organization says Ebola could infect more than 20,000 people across the region by the time the outbreak is over. The epidemic has health experts and governments scrambling to prevent more people from becoming infected. Zlatica Hoke has more.
Video

Video Asian Bacteria Threatens Florida Orange Trees

Florida's citrus fruit industry is facing a serious threat from a bacteria carried by the Asian insect called psyllid. The widespread infestation again highlights the danger of transferring non-native species to American soil. VOA’s George Putic reports.
Video

Video Aging Will Reduce Economic Growth Worldwide in Coming Decades

The world is getting older, fast. And as more people retire each year, fewer working-age people will be there to replace them. Bond rating agency Moody’s says that will lead to a decline in household savings; reducing global investments - which in turn, will lead to slower economic growth around the world. But experts say it’s not too late to mitigate the economic impact of the world’s aging populations. Mil Arcega has more.
Video

Video Is West Doing Enough to Tackle Islamic State?

U.S. President Barack Obama has ruled out sending ground troops to Iraq to fight militants of the so-called Islamic State, or ISIS, despite officials in Washington describing the extremist group as the biggest threat the United States has faced in years. Henry Ridgwell reports from London on the growing uncertainty over whether the West’s response to ISIS will be enough to defeat the terrorist threat.
Video

Video Pachyderms Play Polo to Raise Money for Elephants

Polo, the ancient team competition typically played on horseback, is known as the “sport of kings.” However, the royal version for one annual event in Thailand swaps the horse for the kingdom’s national symbol - the elephant. VOA Correspondent Steve Herman in Samut Prakan reports that the King’s Cup Elephant Polo tournament is all for a good cause.
Video

Video Coalition to Fight Islamic State Could Reward Assad

The United States along with European and Mideast allies are considering a broader assault against Islamic State fighters who have spread from Syria into Iraq and risk further destabilizing an already troubled region. But as VOA State Department Correspondent Scott Stearns reports, confronting those militants could end up helping the embattled Syrian President Bashar al-Assad.
Video

Video Made in America Socks Get Toehold in Online Fashion Market

Three young entrepreneurs are hoping to revolutionize the high-end sock industry by introducing all-American creations of their own. And they’re doing most of it the old-fashioned way. VOA’s Julie Taboh recently caught up with them to learn what goes into making their one-of-a-kind socks.
Video

Video Americans, Ex-Pats Send Relief Supplies to West Africa

Health organizations from around the world are sending supplies and specialists to the West African countries that are dealing with the worst Ebola outbreak in history. On a smaller scale, ordinary Americans and African expatriates living in the United States are doing the same. VOA's Carol Pearson reports.
Video

Video America's Most Popular Artworks Displayed in Public Places

Public places in cities across America were turned into open-air art galleries in August. Pictures of the nation’s most popular artworks were displayed on billboards, bus shelters, subway platforms and more. The idea behind “Art Everywhere,” a collaborative campaign by five major museums is to allow more people to enjoy art and learn about the country’s culture and history. Faiza Elmasry has more.
Video

Video Chinese Doctors Use 3-D Spinal Implant

A Chinese boy suffering from a debilitating bone disease has become the first patient with a part of his spine created in a three-dimensional printer. Doctors say he will soon regain normal mobility. VOA’s George Putic reports.
Video

Video India’s Leprosy Battle Stymied by Continuing Stigma

Medical advancements in the treatment of leprosy have greatly diminished its impact around the world, largely eliminating the disease from most countries. India made great strides in combating leprosy, but still accounts for a majority of the world’s new cases each year, and the number of newly infected Indians is rising - more than 130,000 recorded last year. Doctors there say the problem has more to do with society than science. Shaikh Azizur Rahman reports from Kolkata.
Video

Video Scientists Unlock Mystery of Bird Flocks

How can flocks of birds, schools of fish or herds of antelope suddenly change direction -- all the individuals adjusting their movement in concert, at seemingly the same time? British researchers now have some insights into this behavior, which has puzzled scientists for a long time. VOA's George Putic has more.

AppleAndroid