How old is the oldest polar bear fossil

There have been questions about whether polar bears diverged from brown bears a million years ago or more recently, he says, and "it is great to see such strong data clarifying that the divergence is recent". Yet their history of quick adaptation will do little to help the bears survive global warming. If warming continues at the high rate that we are seeing today and the bears' ice habitat is destroyed, the species is going to be in serious trouble," says Lindqvist.

Lindqvist, C. Natl Acad. USA advance online publication doi Download references. You can also search for this author in PubMed Google Scholar.

Ian Stirling. Charlotte Lindqvist. Polar Bears International. Reprints and Permissions. Kaplan, M. Ancient polar-bear fossil yields genome. Nature Download citation. Published : 01 March Anyone you share the following link with will be able to read this content:.

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Tweets by PolarResearch. Published by the Norwegian Polar Institute. Published in cooperation with Open Academia. Editor-in-Chief: Helle V. Skip to main content Skip to main navigation menu Skip to site footer. Abstract During recent fieldwork in Svalbard, a well preserved subfossil left mandible of a polar bear Ursus maritimus Phipps, was discovered. Organisms that are more closely related are grouped together. In this system, only clades — groups of organisms that contain all the descendents of an ancestor — are named.

When we look at the family tree of bears, we can see that not only are polar bears most closely related to brown bears, but they actually fall within the brown bear clade. There is no clade that includes all the brown bears and excludes the polar bears. From an evolutionary perspective, polar bears are simply a unique and highly specialized sort of brown bear!

The surprise came when the researchers used two different lines of reasoning to learn more about the relationship between the ancestral polar bear and the fossil. First, they used the DNA sequences to extrapolate back to the sequence that the ancestor of polar bears and brown bears would likely have carried. Second, they used molecular clocks to estimate the date of the split between polar bears and brown bears. Molecular clocks are stretches of DNA that evolve at a fairly regular pace can be used as evolutionary tape measures to estimate how long ago different events happened.

The more differences a clock-like stretch of DNA has accumulated since a divergence, the more time has probably passed since that divergence. All this means that the fossil which may be as many as , years old likely represents one of the very earliest members of the polar bear lineage! Just 20, years or so after they diverged from forest-dwelling brown bears, polar bears had already evolved their distinctive marine lifestyle.

This rapid pace of polar bear evolution may have been related to changes in the climate going on at the time. The polar bear and brown bear lineage split during a glacial age. This may have provided the ecological setting for the evolution of the seafood eating, sea ice-loving polar bear lifestyle.

The newly formed polar bear lineage survived one warm interglacial period before being plunged back into another glacial age. Now of course, the planet is warming again — this time due to human actions. Will polar bears survive? The answer is not clear, but the new research does shed some light on the issue. We now know that polar bears have evolved surprisingly quickly in the past. However, today, the Earth is heating up much faster than it ever has before — and the unprecedented pace of that change makes it difficult for slow reproducing organisms like polar bears to evolve to keep up.

One thing is for certain: knowing more about how polar bears have responded to climate change in their evolutionary past can help us figure out how to help them survive into the future. It shows mitochondrial genome sequence variation among different bears. For each sequence, the differences between it and a reference polar bear sequence shown at the bottom are marked with black lines.

Stretches of DNA with different functions are indicated by the color of the reference sequence. The sequence from the polar bear fossil is labeled in red font. How to use Evo in the News with students.