Italian Bears Softened by Centuries of Human Proximity

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AAmong land creatures, brown bears are rather unwelcome to encounter while walking in the woods. But if you’re hiking in the mountains of central Italy, it might not be so bad.

It’s not like you can sit down and have an espresso with a bear, but at least in one small corner of Italy, bears have evolved to become less dangerous than before, according to a study published today in Molecular biology and evolution. And this change may have been caused by humans.

Apennine brown bears (Ursus arctos marsicanus), cousins ​​of grizzly bears (U. arctos horribilis), occur only in the mountains of central Italy. These Italian bears diverged from their European ancestors, the brown bears, around 2,000 to 3,000 years ago. As it became geographically restricted to the Apennines, the central Italian population evolved into a subspecies with distinct characteristics, including tolerance towards humans.

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“One of the main causes of decline and isolation was likely the clearing of forests associated with the expansion of agriculture and the increase in human population density in central Italy,” the paper’s lead author, evolutionary biologist Andrea Benazzo of the University of Ferrara, said in a statement.

Brown bear populations were crushed and persecuted by the spread of agriculture and urbanization beginning in Roman times. About 1,500 years ago, Apennine brown bears were completely isolated from their closest relatives, and their total numbers eventually fell to just 50 individuals. Restricted to a protected area, the Abruzzo, Lazio and Molise National Park, Apennine brown bears are currently classified as critically endangered.

Isolated animal populations generally experience reduced genetic diversity and gene flow. But are these genetic changes responsible for reducing the aggression of these brown bears, or is there another force at play? Italian researchers and colleagues from France, Brazil, Slovakia and the United States compared the genomes of 13 Apennine bears with those of brown bears (U. arctos) in Slovakia and grizzly bears in the United States

As expected, the Apennine brown bear genome showed the reduced diversity that accompanies significant inbreeding, which corroborated that a population bottleneck had occurred when humans forced the bears into a more limited range. Intriguingly, researchers identified distinct genetic variants in the genome of Apennine bears associated with the docile behavior of other species, such as dogs and cats. They hypothesized that humans were unwittingly putting selection pressure on this population of bears by killing the most aggressive ones, thereby leading to an evolutionary shift toward bears displaying greater tolerance toward humans.

“Human-wildlife interactions are often dangerous for the survival of a species, but can also promote the evolution of conflict-reducing traits,” concluded geneticist Giorgio Bertorelle, co-author of the study.

Ironically, by selectively eliminating the most aggressive Apennine bears to make room for farms and settlements, the subspecies could have gained a greater chance of survival. The more docile individuals left behind were more likely to survive, mate and pass on their genes. Despite the loss of genetic variation and increased accumulation of bad mutations, tolerant bears could persist in a human-dominated environment.

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Main image: Bruno D’Amicis/ Molecular biology and evolution

• Devin Reese

  Published on December 15, 2025

  Devin Reese is the editor-in-chief of Natural history and a science writer based in Alexandria, Virginia.