How the psychology and biology of the world’s most popular pets compare

WORDS SCOTT DUTFIELD

Humankind’s canine companions and feline friends belong to an order of animals called Carnivora. They are both the descendants of the first mammals of the late Paleocene epoch that hungered for the flesh of other animals. Between 65 and 35 million years ago, an order of weasel-like animals called Miacis skulked through the trees of ancient woodlands across Eurasia and North America. These furry mammals were arboreal creatures, meaning they spent their time hunting among the lush vegetation of the Paleocene forest. Although Miacis was one of the earliest carnivorous mammals on Earth, it was by no means the most ferocious.

Following the extinction of the dinosaurs around 66 million years ago, two mammalian hunters rose to the top of the food chain: wolf-like predators called creodonts and the hoof-footed ancestors of marine mammals, called mesonychids. Both of these apex predators met their extinction due to an overlap of resources and competition with other carnivores. Miacis, on the other hand, began a lineage of mammals that resulted in the evolution of prolific predators in the modern world, such as lions, tigers and bears. Around 43 million years ago, the carnivorous descendant of Miacis diverged into two distinct paths – the ‘dog-like’ Caniformia and the ‘cat-like’ Feliformia. Over millions of years, these animals evolved into the array of feline and canine species seen today, including the domestic cat and dog.

The evolutionary road to becoming the cats and dogs we know today didn’t occur through typical means. Unlike the pressures of natural selection that their wild cousins have endured for millennia, cats and dogs owe their current form to their interactions with humans. Dogs were the first to find human companionship around 23,000 years ago. Some of the most recent genetic research suggests that prehistoric grey wolves and humankind evolved in tandem in Siberia in the late Pleistocene. Over thousands of years of benefiting from hanging around one another for food and safety, prehistoric people likely bred the tamest of wolves into domesticated allies.