In Italy, Bears Isolated Since Antiquity Have Changed Their Behavior and Become Less Aggressive Toward Humans

As human activity shapes landscapes, some animal species adapt or disappear. In central Italy, a population of brown bears, isolated since Antiquity, has seen its behavior evolve in constant contact with surrounding villages. These Apennine bears, now smaller and less aggressive than their cousins ​​from Europe or America, embody a rare case of behavioral evolution influenced by human proximity.

A study carried out by researchers from the University of Ferrara and published in the journal Molecular Biology and Evolution reveals the genetic mechanisms at work in this transformation. By analyzing the complete genome of several individuals, scientists have highlighted signatures of selection linked to docility. This discovery raises major questions about how interaction with humans can modify the evolution of a species, even in the context of demographic decline and the threat of extinction.

Ancient cohabitation between man and the Apennine brown bear

In the Apennines, in central Italy, a small population of brown bears (Ursus arctos marsicanus) has lived for centuries as close as possible to human activities. This population is estimated at around 60 individuals today. It has been genetically isolated for around 2,000 to 3,000 years, according to analyzes by researchers at the University of Ferrara. Andrea Benazzo, co-author of the study, recalls that this isolation dates back to the time of the Roman Empire. Time when agricultural expansion and massive land clearing fragmented the country's forest habitats.

Unlike bears found in other regions of Europe, this subspecies does not occupy a remote wild territory. On the contrary, it shares its environment with numerous villages, roads and human infrastructure. This cohabitation, unique in its duration and intensity, exposed the bears to continuous selective pressure. Not through intentional domestication efforts, but through an indirect process. The historical culling of the most aggressive individuals, combined with natural selection favoring traits most compatible with human proximity, has modified the behavioral profile of the species.

This phenomenon goes beyond simple ecological adjustment. It constitutes a rare example of a potentially genetic behavioral adaptation, influenced by human social dynamics. It is not a question of taming, but of an evolution of traits favoring tolerance towards humans in a context of long interaction. This unique situation motivated a team to analyze the genomic, behavioral and evolutionary consequences on this population.

A genetically isolated and highly depleted population

The Apennine brown bear is not only distinguished by its behavior, but also by its unique genetic profile. The researchers established a reference genome at the chromosomal level for this population. An essential step to understand the particularities of this lineage. The data was compared to brown bears from Slovakia and other North American bear genomes.

The results confirm a high level of endogamy and very reduced genetic diversity. Consequences of isolation and small population size. These factors increase the risk of extinction in the medium term, by limiting adaptive capacity in the face of environmental changes or the appearance of diseases. Professor Giorgio Bertorelle emphasizes that this genetic weakness is worrying. However, it should not obscure the evolutionary specificities developed by these bears.

Among these specificities, scientists have identified signatures of selection affecting genes involved in behavior. So it's not just genetic drift due to isolation. But indeed a selective process acting on behavioral traits. This detection of a selection signal on variants associated with the reduction of aggressiveness clearly distinguishes this population from other larger lineages.

Behavioral evolution shaped by human pressures

The brown bears of the Apennines today exhibit very different behavior from their counterparts in Central Europe or North America. They are less aggressive, less fearful. Additionally, they developed distinct morphological traits, such as smaller size and a specific cranial shape. This profile results from selective pressure exerted over time by human activities, as mentioned previously.

Giulia Fabbri, co-author of the study, specifies that the genes identified are linked to neurobehavioral functions, notably involving the regulation of stress, aggression and sociability. This means that bears more likely to avoid conflict or remain discreet were more likely to survive in an anthropized environment. Over time, this unintentional selection favored individuals carrying genes associated with behaviors more compatible with human cohabitation.

The researchers insist that this behavioral evolution represents a side effect of prolonged human interactions. This is not a managed conservation strategy. The exclusion – often lethal – of individuals perceived as dangerous has gradually shaped the behavior of the remaining population. It is therefore a behavioral filter operated by humans, consciously or not.

This type of genetic behavioral adaptation remains rare among large carnivores. It recalls certain processes of domestication, without following their complete trajectory. Here, humans did not try to tame the bear. However, through its mere presence and practices, it has modified the evolutionary trajectory of a wild species.

A crucial issue for conservation policies

The results of this study pose an essential question for conservation strategies. Should we preserve a population as it is or strengthen it at the risk of losing its adaptive characteristics? Until now, policies to preserve biodiversity often emphasize increasing the number of individuals and genetic diversity. For example, through reintroduction programs. But in the case of the Apennine bears, these objectives could come into contradiction, as Giorgio Bertorelle explains.

Indeed, introducing individuals from other populations could dilute the behavioral traits acquired through this unique cohabitation with humans. However, these traits – although coming from a history marked by human pressures – could facilitate the survival of bears in anthropized environments on a global scale. The case of the Marsican bear therefore becomes a natural laboratory for rethinking conservation.

Protecting this population then involves a delicate balance: avoiding genetic collapse without erasing valuable adaptation signatures. This requires rigorous monitoring, strict habitat protection, and consideration of behavioral aspects in management decisions. It is not only a question of saving a species, but also of preserving a rare evolutionary heritage.

At a time when interactions between wildlife and human societies are increasing, this type of study sheds light on new issues. It is no longer enough to count species, we must also understand how they change upon contact with us. The Apennine bear embodies this silent and complex evolution, revealed today by genomics.

Source: Giulia Fabbri et al., “Coexisting with humans: genomic and behavioral consequences in a small and isolated bear population”. Molecular Biology and Evolution (2025).