These rare Italian bears have evolved to be surprisingly chill

How centuries of human pressure quietly reshaped a rare brown bear

Bears are one of the big victims of deforestation. As more and more forests get cut down, bears keep retreating to remote corners, keeping their distance from people. In a small stretch of central Italy, however, bears have followed a different path.

A new genetic study suggests that Apennine brown bears have gradually become less aggressive over thousands of years of living alongside people. Rather than retreating entirely from human activity, this isolated population appears to have adapted to it. The research, published in Molecular Biology and Evolution, traces that shift to changes in the bears’ DNA, shaped by long-term human pressure.

Fewer than 60 Apennine brown bears remain today. They are critically endangered and genetically isolated. Yet their survival may depend in part on an unusual trait for a large carnivore: a higher tolerance for humans.

An Ancient Split

The Apennine brown bear, Ursus arctos marsicanus, exists nowhere else on Earth. Genetic evidence shows that this population diverged from other European brown bears around 2,000 to 3,000 years ago, roughly when human land use intensified across central Italy.

Forests were cleared, agriculture spread, and human settlements expanded. Bears were pushed into shrinking mountain refuges and increasingly treated as pests or threats. About 1,500 years ago, the Apennine bears were completely cut off from other bear populations.

“One major cause of decline and isolation was probably forest clearance associated with the spread of agriculture and increasing human population density in central Italy,” said Andrea Benazzo, an evolutionary biologist at the University of Ferrara and a lead author of the study.

This long isolation came with a cost. With their numbers squeezed down to a few dozen individuals, the bears lost much of their genetic diversity. In most species, such a bottleneck increases the risk of extinction.

But the Apennine bears adapted in an unexpected way

Survival of the Friendliest

The researchers propose a blunt evolutionary reason for this. For centuries, humans likely killed the bears that posed the greatest danger. The boldest, most aggressive individuals were the first to be targeted near farms and villages.

The calmer bears survived.

Over many generations, this pressure shifted the population’s behavior. Bears that avoided conflict lived longer, reproduced more, and passed on the genetic variants linked to reduced aggression.

“Human-wildlife interactions are often dangerous for the survival of a species, but may also favor the evolution of traits that reduce conflict,” said Giorgio Bertorelle, a geneticist and co-author of the study.

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This process mirrors patterns seen in other human-dominated landscapes. Wildlife often changes behavior quickly around people, but clear evidence that such changes become embedded in the genome is rare, especially in large carnivores.

The Apennine bears provide one of the clearest examples yet that long-term coexistence with humans can shape evolution itself.

Avoiding Conflict

The findings arrive as Europe grapples with the return of large carnivores. In northern Italy and parts of Greece, brown bear populations have rebounded under conservation laws, sometimes with tragic consequences when bears and people collide.

Apennine bears offer a contrasting case. Despite living close to villages, serious attacks are exceedingly rare. Their reduced aggression may be one reason coexistence has endured.

But the story carries a warning. The same pressures that favored tolerance also caused severe genetic erosion. The bears carry many harmful mutations and remain perilously close to extinction. For conservationists, that poses a dilemma. Introducing bears from elsewhere could boost genetic diversity but risk losing traits that reduce conflict.

As landscapes change, some species vanish, while others adjust in ways that allow them to persist alongside people. In the Apennines, those changes are written into the bears’ DNA, the result of centuries of pressure favoring animals that were better at avoiding conflict.