Companion animals support human wellbeing and health: evolutionary, behavioral and physiological contexts.

This review deals with the questions why humans want to live with other animals and how this is at all possible. In fact, it has become common sense that living and working with companion animals entails major benefits for human wellbeing and health, albeit with the caveat that the positive experience of private keepers and practitioners in pedagogy and therapy is not always backed by scientific scrutiny. The present focus is on relevant aspects of the "Darwinian continuum," which provides humans and other animals with a shared social toolbox, including brain, physiology and behavioral organization. It is discussed why domesticated animals are particularly suitable companions, why dogs are a special case, and why anthropomorphizing other animals may be as much an asset as a burden. In fact, living with companion animals is a human universal, which seems basically motivated by biophilia (the human-typical interest in nature and animals), and by striving for social homoeostasis (for social contexts supporting wellbeing and health). Between-species socializing is possible because of common phylogeny and functional convergence, resulting in matching social mindsets and behavioral systems. It is based on shared principles of behavioral organization, of thinking and decision making, on shared neuronal, physiological and psychological mechanisms, on virtually identical basic affects, and on the shared stress and calming systems. Finally, the social toolbox shared between humans and other animals also suggests a relatively moderate socio-cognitive gap between humans and other animals.