🌅 The Evolutionary Origins of Petkeeping

SOURCE

Grueter et al. (2026)

WHAT TO KNOW

• A new study by researchers at the University of Oxford in the U.K. documents 427 cases of monkeys and apes playing with, grooming, holding, carrying, and even adopting other species. The cases involved 88 primate species and 127 partner species, of which 55 were non-primates. The authors say the interactions, which were pulled from previous studies, media reports, and a survey of primatologists spanning the 1970s to 2025, don’t amount to pet-keeping as humans know it, but could represent the evolutionary building blocks from which human-animal companionship eventually emerged.

WHY IT MATTERS

• Scientists have long considered humans unique when it comes to forming close social relationships with other species, and while instances of different animal species hanging out together isn’t a new phenomenon, previous research suggested the partnerships form mostly for practical reasons, like improving predator detection or increasing foraging opportunities. The present study instead documented instances of primates grooming dogs, gently stroking squirrels, and playing with pigs for no apparent benefit, hinting at a sense of social curiosity similar to that of humans. That said, not all partnerships in the study ended well, with 13 cases tipping into rough handling by the primate and killing the partner animal.

CONNECT THE DOTS

• Cross-species friendships are one of several social instincts and activities that monkeys share with humans, including using different facial expressions to communicate and even tickling one another. Other research has found kissing likely evolved in a common human ancestor some 21 million years ago, suggesting smooches are another ancient trait common to large apes and humans that has persisted through the course of evolution.