The more time passes, the more our species steals habitat from bears. It is happening with polar bears and brown bears, but there is a subspecies of the latter that has learned more than the others to coexist with humans. This is the Marsican bear, which lives in what is now the National Park of Abruzzo, Lazio and Molise and of which just 50 specimens survive. Which, as demonstrated by a study published in Molecular Biology and Evolutionand perhaps precisely because of their small numbers, they are more docile and placid than their close relatives – a characteristic that is also found in their DNA.
The DNA of the Abruzzo bear. The Marsican bear has existed as a subspecies for 2 or 3,000 years (the date is not yet certain), when a first population of brown bear broke away from the main one, isolating itself for thousands of years. Since then, the Marsican bear has developed physical characteristics that distinguish it from the brown bear: it is smaller, has some subtle anatomical differences and above all is much more used to living with humans.
Cohabitation. To understand how prolonged coexistence has changed the Marsican bear, a team from the University of Ferrara analyzed the genomes of 12 Marsican specimens, comparing them with those of its relatives living in Europe, as well as a population of American brown bears. The first discovery made thanks to this analysis is also the most predictable: the rate of inbreeding (i.e. mating between relatives) within the Marsican bear population is decidedly higher than that of other brown bears.
How to survive farming. More interesting is the fact that the DNA of the Marsican bear bears clear signs of selection in relation to certain genes linked to the reduction of aggression: in simple words, the Marsican bear is now more docile also genetically. The causes of this selection are easy to explain: around 3,000 years ago, agriculture arrived in central Italy, and with it the cutting of forests and the beginning of the fragmentation and destruction of the Marsican bear’s habitat.
Genetic variant. The bears therefore found themselves having less space available and interbreeding with humans more often: the more aggressive specimens were killed more easily, while the more docile ones were ignored and managed to reproduce and pass on their genes.
This shows that, as explained by Giorgio Bertorelle, one of the authors of the study, if it is true that «human-animal interactions put the survival of a species at risk, they can also favor the emergence of traits that reduce conflict».
According to the authors, it is a genetic variant that must be preserved, and not “diluted”, for example with repopulation operations with other subspecies of brown bear.
