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August 2011

Irish Ancestry for polar bears

Dr Ceiridwen Edwards,Trinity College (now Oxford University), sequenced the mitochondrial DNA of Irish bears from different ages. Mitochondria are parts of cells with their own DNA which are passed on from mother to cub. What she found was that the older Irish bears from between 38,000 and 43,000 years ago before the LGM (Last Glacial Maximum), have a genetic signature that matches bears found today in eastern parts of Europe. The last bears to survive here, from around 3,000 years ago have different sequences, which are like other western European bears of today. However the most intriguing genetic signatures come from those bears from the several millennia (11,000-38,000 years ago) that bracket the LGM. Edwards said: “Surprisingly, when we compared the sequences from these Irish bears from cooler times to the DNA database we discovered that they were the closest yet found to those from in modern polar bears.” This implied that the maternal ancestors of this charismatic and endangered species hailed from this vicinity. However, from bone isotope analysis it is clear that unlike polar bears, the ancient Irish ice age bears did not have a marine diet.

Pete Coxon (Head of Geography) was an author concerned with the Quaternary geological aspects of the paper.

During the maximum extent of the last glaciation some 24,000 to 18,000 years ago Ireland was almost completely covered by ice. Only the highest peaks and those surrounding the glacial outlets that poured ice onto the continental shelf were free of ice. The environment was one that is perfect for polar bears with extensive shelf ice formed by tidewater glaciers around Ireland’s margins –some of this ice stretched 10s of kilometres onto the western shelf and in the Irish Sea such ice reached the Scilly Isles. The ice poured through large glacial troughs that now form Ireland’s western bays (Donegal Bay, Clew Bay, Galway Bay, the Shannon Estuary and Bantry Bay) much as ice exiting the Greenland Ice Cap carves valleys today before breaking up and floating out into the North Atlantic.

Photo caption: An outlet glacier in East Greenland –a modern version of what the west coast of Ireland looked like during the maximum of the last glaciation (photo: P. Coxon)

Other contributors to the study included scientists in other institutions in the USA, United Kingdom, Belgium, Spain, Denmark, Russia and Sweden. The Irish bear DNA research was supported by The Irish Council for Science, Engineering and Technology. Other funding was provided by the European Research Council, The National Evolutionary Synthesis Center (NESCent) and the National Science Foundation.

Last updated 29 September 2017