Monkey friendships with dogs, deer and even pigs offer clues to the evolutionary origins of pet-keeping

Key Points:

• A new international study led by the University of Oxford reveals that many nonhuman primates engage in friendly interactions such as playing, grooming, and even adopting individuals from other species, suggesting deep evolutionary roots for human-animal companionship.
• The comprehensive review documents 427 cases involving 88 primate species and 127 partner species, showing that juveniles are more likely to play with other species while adult females tend to groom them, with adult males less involved.
• Most interactions occur between closely related species, but some involve distantly related animals like dogs, birds, and reptiles, and are usually initiated by the primates themselves, indicating social curiosity and tolerance beyond practical benefits.
• While many cross-species interactions are positive, some result in harm or death, highlighting that such relationships do not always end well, exemplified by a male baboon reportedly kidnapping a domestic puppy.
• The findings have important implications for conservation and animal welfare, offering insights into the evolution of empathy and social flexibility, and encouraging more systematic recording of these interactions in primate field studies.