Paleontologists (An individual that studies the history of life) know that one of the the earliest dogs was the Hesperocyon, and the animal was about the size of a domestic cat. Its body proportions resemble those of a genet more than those of any dog. It had short forelimbs, long hind limbs and a long back and tail, proportions that suggest an agile animal well able to move quickly in the forest floor, jumping and veering around obstacles and climbing when necessary as a result of their arboreal ancestors. However, you wolf grow larger and faster.