...human beings are a distinctly pet-loving bunch. In no other species do adults regularly and knowingly rear the young of other species and support them into old age; in our species it is commonplace.Particularly
[they] live with us, eating the food we give them, interrupting our sleep, dictating our schedules, occasionally soiling the carpet, and giving nothing in return but companionship and often desultory affection.
What explains this yen to have animals in our lives?
An anthropologist named Pat Shipman believes she’s found the answer: Animals make us human. She means this not in a metaphorical way — that animals teach us about loyalty or nurturing or the fragility of life or anything like that — but that the unique ability to observe and control the behavior of other animals is what allowed one particular set of Pleistocene era primates to evolve into modern man. The hunting of animals and the processing of their corpses drove the creation of tools, and the need to record and relate information about animals was so important that it gave rise to the creation of language and art. Our bond with nonhuman animals has shaped us at the level of our genes, giving us the ability to drink milk into adulthood and even, Shipman argues, promoting the set of finely honed relational antennae that allowed us to create the complex societies most of us live in today. Our love of pets is an artifact of that evolutionary interdependence.
Though the thesis is that it is our 'exploitation' of other animal species that may have made us human, it is also how we treat animals that make us humane.