Attachments between non-human animals of different species are surprisingly common in situations involving human agency (e.g., homes, zoos, and wildlife parks). However, cross-species animal friendships analogous to pet-keeping by humans are at least rare and possibly non-existent in nature. Why has pet-keeping evolved only in Homo sapiens? I review theories that explain pet-keeping either as an adaptation or an evolutionary by-product. I suggest that these explanations cannot account for the wide variation in the distribution and forms of pet-keeping across human societies and over historical time. Using fluctuations in the popularity of dog breeds in the United States, I show how shifts in choices of pets follow the rapid changes in preferences that characterize fashion cycles. I argue that while humans possess some innate traits that facilitate attachment to members of other species (e.g., parental urges, attraction to creatures with infantile features), pet-keeping is largely a product of social learning and imitation-based cultural evolution.
Herzog, H. (2014). Biology, culture, and the origins of pet-keeping. Animal Behavior and Cognition, 1(3), 296-308. doi: 10.12966/abc.08.06.2014