POLAR BEAR: If researchers can better understand how old the polar bear is as a unique species, they will gain a better understanding of how to help the Arctic bear survive human-induced climate change.
Image: Scott Schliebe/USFWS
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Polar bears may have trod the planet for millions of years, according to a new genetic analysis. That suggests the white-coated, massive bears have weathered previous natural climate changes, and may predate the Arctic ice that is their preferred—and only—habitat today, which is why the species future remains uncertain presently.
"There's no guarantee that they'll survive this time," says geneticist Webb Miller of Pennsylvania State University, an author of the study published July 23 in Proceedings of the National Academy of Sciences. After all, Miller notes, the species currently lacks much genetic diversity to help it adapt to changing conditions as well as facing unprecedented threats such as heavy metal pollution accumulating in the Arctic. By better understanding how old the species is, the scientists hope to better understand what might be done to allow the polar bear to cope with onrushing climate change and other existential challenges.
By analyzing the genomes of 28 bears—polar bears, including a roughly 120,000-year-old specimen from Norway's Svalbard archipelago, as well as modern brown bears and black bears—the scientists in effect read back in time to a common ancestor at least four million years ago. That finding conflicts with a genetic analysis published in Science earlier this year that suggested the species was only 600,000 years old or so, which the team behind the new research suggests may result from misreading past interbreeding events with closely related brown bears.
In fact, the key problem here may be that technically the polar bear may not be a species at all. "If one defines that two species separate as when they cannot produce viable offspring, then perhaps brown bears and polar bears aren't yet separate species," Miller admits.
What makes a polar bear a polar bear? There's the white coat and black skin as well as less visible differences like a thicker layer of subcutaneous fat layers and richer milk. These and other unique features of adaptation to the harsh conditions of Arctic life have convinced biologists that the polar bears represent a unique type of animal—a species of its own. After all, the brown bear that is its closest living relative lacks all of these adaptations, looks different, eats different food and would not fare well in the harsh conditions out on the Arctic ice.
Yet, brown bears and polar bears, when they meet, can mate, as evidenced both by the genetic record and observations in the wild. Because polar bears have been spending more time off the ice in recent years, they appear to have begun to interbreed with adjacent brown bear populations, and some of these hybrids are into their second generations. If the basic definition of a species is a group of organisms capable of mating and producing fertile offspring only within their own group, the polar bear and brown bear fail to qualify.
Such interbreeding between bear species makes genetic analysis that much more difficult. After all, if the species interbreed even once, that single event can appear to determine the point at which the two species diverged if a scientist happens to analyze only the portion of the genome influenced by that mating event. And the mixing of genetic material has been going on for a long time between polar and brown bears, making disentangling their genetic history that much harder.
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19 Comments
Add CommentEndangered? Says who? This years polar bear census published by the Canadian govdrnmnet has them at the highest population since numbers were kept in the early 1960's.
Reply | Report Abuse | Link to thistheir way of life is changing and their behaviours changing--evolution in action--they are perhaps speciating (blending genomes with non-polar bears--as in humans blening genomes with non-human primates, some are moving further north and hunting bigger prey finding new hunting grounds, becominga different bear than we recognize as polar bear today--I guess that is what is meant by endangered.
Reply | Report Abuse | Link to thisBy the scientists who worked on the IPCC fourth assessment report, and the by simple notion that sea ice is require for a polar bear hunt which is disappearing. As for the population numbers, there are more than one way to interpret them.
Reply | Report Abuse | Link to thisFirst, population numbers hide the actual demographics of the population. A population with low numbers of young (than previous generations) will cause the population number to decrease in the following generation. So if there is not enough young polar bears now than there are less adult polar bears in the future. This is what we are seeing in the current polar numbers.
Secondly, numbers can differ in the sampling scheme used which in the case of the 2011 numbers are done by aerial surveys vs the mark and recapture methods that had been used for 40 years. What this means is that the population numbers can't be compared adequately. The question is then why would one change the sampling method that has been used for four decades? This I have no idea.
blah, blah...polar bears are NOT endangered on any list in Canada or Russia where the bulk of the the world's polar bear populatiion exist. Numbers from Churchill, Manitoba to Devon Island to 'wherever' are healthy.
Reply | Report Abuse | Link to this'Endangered' is another misdleading agenda-driven adjective added out of ignorance. Writers get caught up in their own hyperbolae.
Drikus Gissing, Nunavut’s director of wildlife management. “There is no doom and gloom.” He said the media has led people to believe polar bears are endangered. “They are not.” He added that there are about 25,000 polar bears across Canada’s Arctic. “That’s likely the highest [population level] there has ever been.”
Reply | Report Abuse | Link to thisMore ridiculous warmist nonsense in information that actually discredits their claim. Warming has happened in the past, Naturally and polar bears survived it.
Reply | Report Abuse | Link to thisWarmists you are slipping here. You should not be publishing articles suggesting warming has happened before human industry and worse, you actually admitted species can in fact survive a warming period.
Wow, I am amazed as well, a warmist actually admitted there has been interglacial warming periods. Warmist doctrine is this doesnt really happen, because there has never ever been unnatural global warming and its only cause can be human produced CO2.
Warmists, if you are going to continue with your claims of Armageddon and that following your holy computer models is the only way to save the planet, you have to keep on message.
"The question is then why would one change the sampling method that has been used for four decades? This I have no idea."
Reply | Report Abuse | Link to thisPerhaps, because polar bears learned to flatten out and hide whenever a planes engine is heard. Polar bears are very intelligent and would rather eat humans than be poked and prodded by them. GK
Obviously polar bears have survived climate changes in the past, but those changes didn't take place in a matter of decades. Now what is it you blind folded deniers still don't understand? Just about any specie can adapt if given enough time to migrate or adapt through natural evolutionary means. We have mass extinction today because the change is happening too quickly. I realize this is a difficult concept to understand for people who can't see beyond their own reality, but it is not a complicated concept to grasp. I have to wonder if it is a genetic problem for some people to be so intimidated by the changing world we created.
Reply | Report Abuse | Link to thisLife can survive a variation of 10°C in one day between night and day.
Reply | Report Abuse | Link to thisLife can survive a variation of 10°C in one year between winter and summer.
Life can survive a variation of 10°C in 100 000 years between a glacial period and an interglacial.
Life can survive a variation of 10°C in 10,000,000 years between an icehouse and greenhouse.
But what about 2°C in 100 years? I would like to see a proof that life would not survive that.
In fact, if a polar bear wanders 200 miles south... guess what? He just survived a 2 degree average warming. Let's try to stay real. GK
Squid alert. The deniers are squirting ink again. There is no science in their posts.
Reply | Report Abuse | Link to thisKarst is just making up stuff that sounds sort of reasonable to anyone who doesn't understand how polar bears survive. The actual ecology of the polar bear indicates they are in danger, not from a 2 degree change in temperature, but because the Arctic ice necessary for their survival is disappearing more every year.
Karst has said elsewhere that he is so convinced that global warming is false that he would be willing to bet his house, his children, the United States, and civilization itself that he is right. And he is trying to convince everyone else to make the same bet.
Squid alert. The deniers are here to squirt ink into the conversation.
Reply | Report Abuse | Link to thispriddseren says: "Wow, I am amazed as well, a warmist actually admitted there has been interglacial warming periods. Warmist doctrine is this doesnt really happen, because there has never ever been unnatural global warming and its only cause can be human produced CO2."
Priddseren, I know from your long history of ridiculing Global Warming that you really have no understanding of the science at all, but here you seem to be in the odd position of ridiculing people for doing what you want them to do.
You want the scientists who believe GW is happening to acknowledge that there are natural fluctuations in climate, and when they do, you accuse them of not being dogmatic enough. Perhaps the dogmatism is in your own self, dogmatically believing your cartoon picture of what scientists think. You think the scientists researching global warming are somehow following some kind of doctrine, because that is what you are doing. You think they have some kind of obligation to "stay on message" because you have to stay on message. You have certainly not learned anything from all the replies that have attempted to educate you.
Every climate scientist knows that warming has happened before. The problem is that you don't know that they know far more about it than you do, and more than the people who apparently pay you to post this garbage.
"Endangered" ? A myth dreamed up to use "cuddly" images for sob-story fund-raising, that's what. When was it, exactly, "Scientific American" ceased being either ?
Reply | Report Abuse | Link to thisThis to my mind this comment by priddseren "... a warmist actually admitted there has been interglacial warming periods. Warmist doctrine is this doesn't really happen, because there has never ever been unnatural global warming and its only cause can be human produced CO2" displays a total ignorance of science. It has always been known that there are interglacial (warming periods). The precise cause and mechanism of both warming & cooling periods in the past can be debated, but that does not mean that the current warming is not human-caused. There is much evidence to show that it is. And as for whether the polar bear will become endangered as a result of global warming can also be debated, but as the author of the article points out the polar bear is having to cope with the influence of human activity that it did not have to cope with in the past.
Reply | Report Abuse | Link to thisMaybe the polar bear and the brown bear are not two different species at all, but rather the same species and no different then the variety of humans on earth, but in this case, they vary by both fur and skin colour, instead of just skin colour. OK so there are some health differences maybe similar to that of diabetes more prominent in individuals with American Indian and/or African-American genetics, but yet still common in all groups of people. We're all still human though and I propose the polar bear and the brown bear are the same species of bears much like all humans are the same species of apes.
Reply | Report Abuse | Link to thisVidoes of a few bears stuggling in melting icepacks and having to swim 60-miles panicked the eco-weenies and we get stories like this. White bears become brown or black bears and a thousands of years from now they return as white bears. We just likely won't be around, which is probably for the good.
Reply | Report Abuse | Link to thisI'm non-scientist here & am merely following this discussion out of interest. Does pridseren have any scientific credentials or is s/he merely a climate change denier?
Reply | Report Abuse | Link to thisJudging from past posts, priddseren not only does not have any scientific credentials, but does not know enough science to pass a middle school science class. He/she does not understand how ordinary greenhouses work, let alone greenhouse gases.
Reply | Report Abuse | Link to thisYour question is very timely. Just yesterday a DNA analysis was released that showed that polar bears and brown bears diverged perhaps 4-5 million years. A different paper recently found genetic traces of brown bear genes in polar bears, and that indicates that they may have been interbreeding relatively recently, sort of like horses and donkeys. That may be because polar bears are spending more time on dry land instead of ice and come in contact with brown bears more.
Reply | Report Abuse | Link to thisAnother squid, just squirting ink and insults, with no actual science.
Reply | Report Abuse | Link to thisThe actual science says that the ice that polar bears depend on for everything is receding to unprecedented levels, thus endangering their way of life. Maybe they'll adapt to a different way of life in an instant (measured in evolutionary time), and maybe they won't.