A recent study appearing in the current issue of the journal Science reveals that polar bears evolved as early as some 600,000 years ago. An international team led by DNA researchers from the German Biodiversity and Climate Research Centre (BiK‐F) shows the largest arctic carnivore to be five times older than previously recognized. The new findings on the evolutionary history of polar bears are the result of an analysis of information from the nuclear genome of polar and brown bears, and shed new light on conservation issues regarding this endangered arctic specialist.
Polar bears are uniquely specialized for life in the arctic.
This fact is undisputed, and supported by a range of morphological, physiological and behavioural evidence.
However, conducting research on the evolutionary history of polar bears is difficult.
The arctic giant spends most of its life on sea ice, and typically also dies there. Its remains sink to the sea floor, where they get ground up by glaciers, or remain undiscovered. Fossil remains of polar bears are therefore scarce.
Because the genetic information contained in each organism carries a lot of information about the past, researchers can study the history of the species by looking at the genes of today’s polar bears.
Recent studies had suggested that the ancestor of polar bears was a brown bear that lived some 150,000 years ago, in the late Pleistocene. That research was based on DNA from the mitochondria ‐ organelles often called the ‘powerhouses of the cell’. Researchers from the German Biodiversity and Climate Research Centre (BiK‐F), together with scientists from Spain, Sweden and the USA, now took an in‐depth look at the genetic information contained in the cell nucleus.
Frank Hailer, BiK‐F, lead author of the study explains: “Instead of the traditional approach of looking at mitochondrial DNA we studied many pieces of nuclear DNA that are each independently inherited. We characterized those pieces, or genetic markers, in multiple polar and brown bear individuals.”