Despite having taken different evolutionary paths, polar bears and brown bears have continued to interbreed just as happened between Neanderthals and Sapiens: this is demonstrated by the analysis of the DNA of modern bears and an ancient specimen that lived more than 100,000 years ago in Norway.
The study was conducted by an international team led by Charlotte Lindqvist of the University of Buffalo (USA).
The results, published in the journal of the American Academy of Sciences (PNAS), may provide useful insights for predicting the future of the two species, which are geographically closer and closer due to climate change.
To unravel the evolutionary intertwining that has characterized the history of these large mammals, the researchers analyzed the genomes of 64 modern polar and brown bears, including some from Alaska, where both species live.
Their DNA was then compared with that extracted from the tooth of an ancient polar bear that lived in the Norwegian archipelago of Svalbard between 115,000 and 130,000 years ago (its remains are preserved in the Natural History Museum of the University of Oslo).
The study found that the two bear species separated between 1.3 and 1.6 million years ago.
Polar bears would later experience a dramatic decline that reduced their genetic diversity.
Evidence of crosses between the two species prior to the time in which the ancient polar bear lived was found in the DNA.
From these hybridization events there would have been an exchange of genes between the two species, with the most consistent gene flow going from brown to polar bears.