They sleep on our beds, steal our food, and generally rule the house. Between them, cats and dogs make up two-thirds of pet ownership worldwide. But which of the two companion animals are we more closely related to? The answer depends on how you look at the question. Cats , dogs and humans are all mammals. In the mammalian family tree, which maps out how different mammal species are related to one another, both cats and dogs belong to the order Carnivora, while humans are primates. These two groups split from a common ancestor about 90 million to 95 million years ago, Springer said. Meanwhile, cats and dogs split from each other much later, around 55 million years ago. In terms of common ancestry, "dogs and cats are more closely related to mammals such as pangolins, horses, cows, whales, bats, shrews and moles than they are to humans," Springer said.…