If you go back far enough, roughly 45 million years ago, the world was devoid of dogs and cats. In their place was a burgeoning group of mammals whose members were largely nocturnal and looked a lot like weasels. From these small, humble beginnings emerged two lineages that would eventually give rise to our closest animal companions.<\/p>\n
When did the first dogs and cats evolve?<\/p>\n
As a group, dogs emerged 12 million years before cats, some time in the Late Eocene approximately 42.5 million years ago. They also evolved in North America, while cats first appeared in Eurasia before migrating to the New World a few million years later.<\/p>\n
The first \u2018true\u2019 dog is known as\u00a0Hesperocyon<\/a>, or \u2018western dog\u2019. It looked a bit like a cat and was about the same size as today\u2019s smaller, domesticated breeds. Like many living and extinct cats,\u00a0Hesperocyon\u00a0was also partially arboreal, spending a lot of its time in trees.<\/p>\n However, there\u2019s no mistaking\u00a0Hesperocyon\u2019s identity as a dog. Its skull and teeth are undeniably dog-like. In fact, it\u2019s these distinctive features that helped the palaeontologists who first discovered\u00a0Hesperocyon\u00a0identify it as a dog, rather than a cat.<\/p>\n Proailurus<\/a>, the first \u2018true\u2019 cat<\/a>, doesn\u2019t look too dissimilar to\u00a0Hesperocyon. It lived a lot later, approximately 30 million years ago in the Late Oligocene, but it too had a similar bodyplan, with an extended, low-slung body, relatively short limbs, and a long, flexible tail.<\/p>\n Both\u00a0Hesperocyon\u00a0and\u00a0Proailurus\u00a0were likely omnivores, based on the fact they had premolars designed for grinding up tough foods like plants – in addition to their sharper canines that effortlessly sliced through meat.<\/p>\n These robust back teeth are thought to be evolutionary leftovers from their shared ancestors, which had more varied diets than their largely carnivorous descendants.\u00a0<\/p>\n What was the last common ancestor of dogs and cats?<\/p>\n Canidae (dogs) and Felidae (cats) belong to an order of placental mammals known as Carnivora. This large and diverse group includes many different mammals, from\u00a0dogs<\/a>\u00a0and cats, to\u00a0bears<\/a>,\u00a0mustelids<\/a>,\u00a0hyenas<\/a>, and even\u00a0sea lions<\/a>,\u00a0seals<\/a>, and\u00a0walruses<\/a>!<\/p>\n The first carnivoran-like animals lived shortly after the\u00a0asteroid impact that wiped out the dinosaurs<\/a>, approximately 65 million years ago. These enigmatic mammals are known as miacids and they\u2019re thought to be the ancestors of carnivorans. This makes them the last common ancestors of dogs and cats.<\/p>\n There are many known species of miacids, but the majority of them were small – the size of weasels or ferrets – with long, flexible bodies and long tails. Some were arboreal, while others lived exclusively on the ground.<\/p>\n The miacids lived for more than 30 million years (65 to 34 million years ago), meaning they overlapped with early dogs like\u00a0Hesperocyon, as well as other dog-like carnivorans such as\u00a0Parictis\u00a0and\u00a0Allocyon\u00a0– the first bears.<\/p>\n Are we more closely related to dogs or cats?<\/p>\n Whether you\u2019re a \u2018dog person\u2019 or a \u2018cat person\u2019, evolution doesn\u2019t take sides – we\u2019re equally related to both.<\/p>\n While dogs, cats, and humans are all mammals, we belong to different orders: carnivora in the case of dogs and cats and Primates in the case of humans. These two groups split from a common ancestor more than 90 million years ago, during a time when\u00a0dinosaurs<\/a>\u00a0still roamed the Earth.<\/p>\n In a way, we can look at dogs and cats as cousins from one side of the family tree – we\u2019re no more closely related to one than the other.<\/p>\n However, tackling this question from a genetic perspective reveals a slightly different answer. According to geneticists, the ancestors of modern dogs went through extensive chromosome rearrangements over the course of their evolutionary history. In contrast, cats retained a genome organisation closer to ours.\u00a0<\/p>\n