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

Turbulent Transition Imperils Tunisia’s Arab Spring Gains

Critics say new anti-terrorism laws worsen Tunisia's situation while others put faith in country’s vibrant civil organizations, women’s movement More

Burundi’s Political Crisis May Become Humanitarian One

United Nations aid agencies issue warning as deadly violence sends tens of thousands fleeing More

Yemenis Adjust to Life Under Houthi Rule

Locals want warring parties to strike deal to stop bloodletting before deciding how country is governed 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.
Seoul Sponsors Korean Unification Fairi
X
Brian Padden
May 29, 2015 1:27 PM
With inter-Korean relations deteriorating over the North’s nuclear program, past military provocations and human rights abuses, many Koreans still hold out hope for eventual peaceful re-unification. VOA’s Brian Padden visited a “unification fair” held this week in Seoul, where border communities promoted the benefits of increased cooperation.
Video

Video Seoul Sponsors Korean Unification Fair

With inter-Korean relations deteriorating over the North’s nuclear program, past military provocations and human rights abuses, many Koreans still hold out hope for eventual peaceful re-unification. VOA’s Brian Padden visited a “unification fair” held this week in Seoul, where border communities promoted the benefits of increased cooperation.
Video

Video Purple Door Coffeeshop: Changing Lives One Cup at a Time

For a quarter of his life, Kevin Persons lived on the street. Today, he is working behind the counter of an espresso bar, serving coffee and working to transition off the streets and into a home. Paul Vargas reports for VOA.
Video

Video Modular Robot Getting Closer to Reality

A robot being developed at Carnegie Mellon University has evolved into a multi-legged modular mechanical snake, able to move over rugged surfaces and explore the surroundings. Scientists say such machines could someday help in search and rescue operations. VOA’s George Putic reports.
Video

Video Shanghai Hosts Big Consumer Electronics Show

Electronic gadgets are a huge success in China, judging by the first Asian Consumer Electronics Show, held this week in Shanghai. Over the course of two days, more than 20,000 visitors watched, tested and played with useful and some less-useful electronic devices exhibited by about 200 manufacturers. VOA’s George Putic has more.
Video

Video Forced to Return Home, Afghan Refugees Face Increased Hardship

Undocumented refugees returning to Afghanistan from Pakistan have no jobs, no support system, and no home return to, and international aid agencies say they and the government are overwhelmed and under-resourced. Ayesha Tanzeem has more from Kabul.
Video

Video Britain Makes Controversial Move to Crack Down on Extremism

Britain is moving to tighten controls on extremist rhetoric, even when it does not incite violence or hatred -- a move that some are concerned might unduly restrict basic freedoms. It is an issue many countries are grappling with as extremist groups gain power in the Middle East, fueled in part by donations and fighters from the West. VOA’s Al Pessin reports from London.
Video

Video 3D Printer Makes Replica of Iconic Sports Car

Cars with parts made by 3D printers are already on the road, but engineers are still learning about this new technology. While testing the possibility of printing an entire car, researchers at the U.S. Department of Energy recently created an electric-powered replica of an iconic sports roadster. VOA’s George Putic has more.
Video

Video Al-Shabab Recruitment Drive Still on In Kenya

The al-Shabab militants that have long battled for control of Somalia also have recruited thousands of young people in Kenya, leaving many families disconsolate. Mohammed Yusuf recently visited the Kenyan town of Isiolo, and met with relatives of those recruited, as well as a many who have helped with the recruiting.
Video

Video A Small Oasis on Kabul's Outskirts Provides Relief From Security Tensions

When people in Kabul want to get away from the city and relax, many choose Qargha Lake, a small resort on the outskirts of Kabul. Ayesha Tanzeem visited and talked with people about the precious oasis.
Video

Video Kenyans Lament Losing Sons to al-Shabab

There is agony, fear and lost hope in the Kenyan town of Isiolo, a key target of a new al-Shabab recruitment drive. VOA's Mohammed Yusuf visits Isiolo to speak with families and at least one man who says he was a recruiter.
Video

Video Scientists Say Plankton More Important Than Previously Thought

Tiny ocean creatures called plankton are mostly thought of as food for whales and other large marine animals, but a four-year global study discovered, among other things, that plankton are a major source of oxygen on our planet. VOA’s George Putic reports.
Video

Video Kenya’s Capital Sees Rise in Shisha Parlors

In Kenya, the smoking of shisha, a type of flavored tobacco, is the latest craze. Patrons are flocking to shisha parlors to smoke and socialize. But the practice can be addictive and harmful, though many dabblers may not realize the dangers, according to a new review. Lenny Ruvaga has more on the story for VOA from Nairobi, Kenya.

VOA Blogs