Polar bears are 450,000 years older than we thought

Endangered predator may be particularly vulnerable to rapid climate change in Arctic, experts fear

A A A

The polar bear is a much older species than previously thought and probably emerged as the Arctic's top land predator when a cold-adapted bear diverged from an ancestral brown bear about 600,000 years ago, a study has found.

The findings suggest that the evolution of the world's largest land carnivore was a much slower process than originally believed, which indicates that the polar bear may be more vulnerable to rapid climate change in the Arctic than previously suggested.

A year ago, scientists produced DNA evidence to suggest that polar bears evolved from ancient brown bears about 150,000 years ago, which surprised many experts because it was a relatively short time for such a big, specialised mammal to have evolved.

This led some to speculate that the polar bear may be able to adapt to the far faster climate changes now taking place in the Arctic, where the sea ice on which the animals hunt has disappeared at a dramatic rate over the past 40 years. However, this earlier study was based on mitochondrial DNA which accounts for less than 1 per cent of an animal's genetic material and is only inherited through the maternal line.

The latest study, published in the journal Science, is based on the much larger amounts of DNA within the animal's chromosomes, which contains a more complete genetic history of the species.

When scientists compared chromosomal DNA of 19 polar bears to the similar DNA of other bear species, they found a clear relationship with the brown bear, which sometimes has overlapping territories with the polar bear, especially during warmer periods.

The scientists estimate that the last common ancestor of polar bears and brown bears lived between 338,000 and 934,000 years ago. The most likely date, however, was about 600,000 years ago, when coincidentally there was a marked global cooling resulting in one of the most pronounced ice ages, said Frank Hailer of the Biodiversity and Climate Research Centre in Frankfurt.

"It was the first dramatic cooling period of the ice ages. Our data on the polar bear lineage may be coincidental but it fits in with the time period when the climate was very cold," he said.

In recent years there have been several reports of encounters between male polar bears and the smaller brown bear resulting in fertile offspring. One hybrid was the result of a hybrid polar-brown bear mating with a pure-bred polar bear.

Dr Hailer said the earlier study on mitochrondrial DNA could be explained by something similar happening about 150,000 years ago, when female brown bears mated with male polar bears resulting in fertile female offspring that "back-crossed" with pure-bred male polar bears, carrying their mitochondrial DNA with them.

"It shows that polar bears and brown bears hybridised about 150,000 years ago and then backcrossed into the main polar bear population. The mitochondrial DNA of polar bears today stems from this period," Dr Hailer said.

Have you tried new the Independent Digital Edition apps?
Latest stories from i100
Have you tried new the Independent Digital Edition apps?
iJobs Job Widget
iJobs General

Recruitment Genius: Parts Advisor

£16500 - £18500 per annum: Recruitment Genius: One of the leading Mercedes-Ben...

Recruitment Genius: Software Developer

£27500 - £35000 per annum: Recruitment Genius: This is an exciting opportunity...

Recruitment Genius: Telemarketers / Sales - Home Based - OTE £23,500

£19500 - £23500 per annum: Recruitment Genius: Experienced B2B Telemarketer wa...

Recruitment Genius: Showroom Assistant

Negotiable: Recruitment Genius: This global company are looking for two Showro...

Day In a Page

Fifa corruption: The 161-page dossier that exposes the organisation's dark heart

The 161-page dossier that exposes Fifa's dark heart

How did a group of corrupt officials turn football’s governing body into what was, in essence, a criminal enterprise? Chris Green and David Connett reveal all
Mediterranean migrant crisis: 'If Europe thinks bombing boats will stop smuggling, it will not. We will defend ourselves,' says Tripoli PM

Exclusive interview with Tripoli PM Khalifa al-Ghweil

'If Europe thinks bombing boats will stop smuggling, it will not. We will defend ourselves'
Raymond Chandler's Los Angeles: How the author foretold the Californian water crisis

Raymond Chandler's Los Angeles

How the author foretold the Californian water crisis
Chinese artist who posted funny image of President Xi Jinping facing five years in prison as authorities crackdown on dissent in the arts

Art attack

Chinese artist who posted funny image of President Xi Jinping facing five years in prison
Marc Jacobs is putting Cher in the limelight as the face of his latest campaign

Cher is the new face of Marc Jacobs

Alexander Fury explains why designers are turning to august stars to front their lines
Parents of six-year-old who beat leukaemia plan to climb Ben Nevis for cancer charity

'I'm climbing Ben Nevis for my daughter'

Karen Attwood's young daughter Yasmin beat cancer. Now her family is about to take on a new challenge - scaling Ben Nevis to help other children
10 best wedding gift ideas

It's that time of year again... 10 best wedding gift ideas

Forget that fancy toaster, we've gone off-list to find memorable gifts that will last a lifetime
Paul Scholes column: With the Premier League over for another year, here are my end of season awards

Paul Scholes column

With the Premier League over for another year, here are my end of season awards
Heysel disaster 30th anniversary: Liverpool have seen too much tragedy to forget fateful day in Belgium

Liverpool have seen too much tragedy to forget Heysel

Thirty years ago, 39 fans waiting to watch a European Cup final died as a result of a fatal cocktail of circumstances. Ian Herbert looks at how a club dealt with this tragedy
Amir Khan vs Chris Algieri: Khan’s audition for Floyd Mayweather may turn into a no-win situation, says Frank Warren

Khan’s audition for Mayweather may turn into a no-win situation

The Bolton fighter could be damned if he dazzles and damned if he doesn’t against Algieri, the man last seen being decked six times by Pacquiao, says Frank Warren
Blundering Tony Blair quits as Middle East peace envoy – only Israel will miss him

Blundering Blair quits as Middle East peace envoy – only Israel will miss him

For Arabs – and for Britons who lost their loved ones in his shambolic war in Iraq – his appointment was an insult, says Robert Fisk
Fifa corruption arrests: All hail the Feds for riding to football's rescue

Fifa corruption arrests

All hail the Feds for riding to football's rescue, says Ian Herbert
Isis in Syria: The Kurdish enclave still resisting the tyranny of President Assad and militant fighters

The Kurdish enclave still resisting the tyranny of Assad and Isis

In Syrian Kurdish cantons along the Turkish border, the progressive aims of the 2011 uprising are being enacted despite the war. Patrick Cockburn returns to Amuda
How I survived Cambodia's Killing Fields: Acclaimed surgeon SreyRam Kuy celebrates her mother's determination to escape the US

How I survived Cambodia's Killing Fields

Acclaimed surgeon SreyRam Kuy celebrates her mother's determination to escape to the US
Stephen Mangan interview: From posh buffoon to pregnant dad, the actor has quite a range

How Stephen Mangan got his range

Posh buffoon, hapless writer, pregnant dad - Mangan is certainly a versatile actor