Following a series of recent news stories about bears wandering into human-inhabited areas, a new genetic analysis of a modern, isolated Italian brown bear species led by scientists from the University of Ferrara has found evidence that bears living near areas with more human villages have evolved into smaller, more tame versions of their ancient ancestors.
The research team said understanding the balance between human activity that adversely affects animal evolution and possible genetic adaptations that contribute to peaceful coexistence with humans could help conserve animal habitats and plan for them, and also guide species restocking efforts, including avoiding ‘selecting out’ the best genetic traits.
How Bears Living Near Humans Are Affected on a Genetic Level
According to a statement detailing the research, scientists have long understood that human activity can shape the local environment, “dramatically affecting” the area’s ecosystems and biodiversity.
The team said habitat change and overuse due to human activity can have the “greatest impacts on wildlife,” including population declines. These changes, along with other pressures from humans living in their local areas, can influence how a species evolves.
To more closely examine the balance between humans and bears, the researchers focused on the Apennine crown bear found only in Central Italy. Evolved from European brown bears around 2,000-3,000 years ago, this species has a long history of close association with human communities and complete isolation from other bear communities, both factors that could have influenced its evolution.
“One major cause of [the Apennine crown bears’] decline and isolation was probably forest clearance associated with the spread of agriculture and increasing human population density in Central Italy,” explained the paper’s lead author, Andrea Benazzo.
Due to these circumstances, an initial observation of the bears revealed what the team termed “significant phenotypic differences” when compared to other brown bear species. For example, their bodies are smaller, their heads and facial features are unique, and they are decidedly less aggressive toward humans than less-evolutionarily impacted European, North American, and Asian brown bear populations.
Genetic Analysis Shows Evidence of Selection Against Aggressive Genes
To determine the extent of human involvement in the genetic differences between these brown bears and less isolated species, the team focused on “recent evolutionary changes” they described as most likely caused by nearby human populations.
First, the team generated a high-quality ‘chromosome-level’ reference table for the Apennine brown bear genome. Next, the team selected re-sequenced whole genomes from a sample of bear individuals.
When the team compared the selected Apennine brown bear sequences with genomes from larger, less tame European brown bears in Slovakia and American brown bear genomes, they found several indications of human-influenced evolution. These changes were most pronounced when comparing the genomic diversity of different bear types.
Specifically, the analysis found that Apennine brown bears exhibited “reduced genomic diversity” compared to their wild counterparts. The team also found higher levels of genetic inbreeding compared to other brown bears.
Co-author of the study, Guilia Fabbri, said that the most interesting discovery came when looking for genes associated with behaviors. According to Fabri, this search revealed that Apennine brown bears possess “selective signatures” at genes previously associated with reduced aggressiveness.
‘Dangerous’ Human-Induced Bear Genome Changes Could Help Reduce Conflict
When detailing their findings, the team said the evidence suggested that genes for more aggressive behavior were selected against in populations living near humans to preserve the community. This selection was most likely driven by humans removing more aggressive bears from their environment, reducing the presence of the aggressive genes in modern populations.
The findings suggest that selection on behavior-related genetic variants, likely driven by human removal of more aggressive bears, led to the emergence of a much less aggressive bear population. Although the encroachment of humans into their natural habitats led to an overall decline in bear numbers and their community’s genetic diversity, the researchers suggest that the same process ultimately unintentionally promotes “the evolution of a less conflictual relationship” between wild brown bears and nearby humans.
“The general implications of our findings are clear,” study co-author Giorgio Bertorelle said, “human-wildlife interactions are often dangerous for the survival of a species, but may also favor the evolution of traits that reduce conflict.”
Bertorelle added that this conclusion means that bear populations that have been heavily and negatively affected by human activities may also retain several evolutionarily driven genetic variants “that should not be diluted, for example, by restocking.”
The paper, “Coexisting with humans: genomic and behavioural consequences in a small and isolated bear population,” was published in Molecular Biology and Evolution.
Christopher Plain is a Science Fiction and Fantasy novelist and Head Science Writer at The Debrief. Follow and connect with him on X, learn about his books at plainfiction.com, or email him directly at christopher@thedebrief.org.