A fossilised jawbone, thought to belong to a polar bear that lived up to 150,000 years ago, has been discovered. It is possibly the oldest polar bear remains ever found.
Polar bears are thought to have evolved relatively recently. Some scientists think this may only have been around 100,000 years ago.
Understanding more about polar bear evolution is difficult as it is rare to find remains. When a polar bear dies, its carcass is likely to be preyed upon or fall to the bottom of the ocean, leaving no trace.
Prof Ólafur Ingólfsson, from the University of Iceland, uncovered the well-preserved jawbone on Svalbard, which is an archipelago between Norway and the North Pole. He carried out dating tests on the fossil and the results suggest an age of between 80,000 and 150,000 years old.
Andy Currant, mammal fossil expert at the Natural History Museum, welcomed the discovery. 'I look forward to hearing more about it,' he said. 'I am surprised at the suggested great age of the new find, however.'
Previous fossils thought to belong to polar bears have been found as far south as the UK, including one from Kew Bridge in London, thought to be 70,000 years old.
Andy explains, 'Most of these finds have turned out to be the remains of a large form of brown bear Ursus arctos, but a bear on Svalbard is almost certain to be a polar bear.'
Polar bears, Ursus maritimus, live in the Arctic. They are well-suited to living in the cold harsh Arctic environment, and have thick layers of fur and blubber for insulation and a cream-coloured coat for camouflage.
They are the largest living land carnivores, and males can grow up to 2.6m in length. Females, however, are much smaller. The brown bear is its closest relative.
Polar bears are listed as vulnerable in the World Conservation Union's IUCN Red List. The main threats to their survival are over fishing, habitat destruction, pollution and the shrinking of the polar sea ice due to global warming,.
Being highly specialised for life in the Arctic, they reproduce slowly. This means their ability to adapt to climate change is reduced.