Evolution
The wolf, whose scientific name is Canis lupus, evolved from a more generalized ®carnivore¯ that roamed the earth about 100 to 120 million years ago. The hoofed mammals, or ungulates, probably all evolved from a common ancestor that lived a few hundred million years ago. Both types of animals became adapted to swift long-distance ®running¯ on open plains, both developed relatively high intelligence, and both descended from forest-dwelling ancestors. Probably they evolved in long association with one another, since the wolf and its ancestors gradually developed better and better adaptations for ®killing¯ and eating hoofed animals; and at the same time, the hoofed animals became better adapted to defending themselves against wolves.
The primitive group of meat eaters, known as creodonts, originated in the northern hemispere, and it is thought that the dog family itself developed in North America and gradually dispersed from there.
Approximately fifty-five million years ago, a mammal with partly specialized "flesh ®teeth¯," or carnassials, came to be. During the next ten million years a large number and variety of these creatures flourished, and one of them, known as Miacis, was similar to members of the dog family of today. Miacis is a member of the family Miacidae, from which all the present families of meat-eaters eventually arose: the dogs, cats, bears, weasels, raccoons, civets, and hyenas.
Thirty to forty million years ago, Miacis gave rise to types of mammals that can be traced through two series of fossils to the dog and bear families. The predecessor to the dog family, Cynodictis, had the same number of ®teeth¯ as the wolf. It was much smaller than a wolf, however, and its body was long and flexible like that of a weasel; its ®legs¯ were of moderate length. In the next fifteen million years, the raccoon family branched from this group and developed separately.
Later, fifteen to thirty million years ago, a strong trend occurred toward the characteristics of present-day wolves, from Cynodictis through the animals Cynodesmus and Tomarctus. The creature's ®legs¯ became longer, the ®feet¯ longer and more compact, the inner digit became ®vestigial¯ on the hind ®foot¯ and much reduced on the fore ®foot¯, the tail became shorter, and the entire proportions began approaching those of the ®wolves¯ and the ®foxes¯.
From Tomarctus, both the ®wolf¯ and the ®fox¯ arose and began developing separately about fifteen million years ago. Although the ®fox¯ did not change much in size, the ®wolf¯ grew larger and larger. A closely related type, the dire wolf (Canis dirus), also branched off. Some of them were much larger than present-day wolves, but they are now extinct. By one or two million years ago, the wolf was much as it is today.
Wild ®dogs¯ evolved from ®wolves¯ as they began to depend on ®humans¯, probably thousands of years ago, when people lived as wandering hunters. ®Wolves¯ may have followed the roaming bands of hunters so they could eat scraps of food that people left behind. They slowly overcame their fear of ®humans¯ and drew closer to their camps. Gradually, people realized that wild ®dogs¯ could help them. With their superb senses, wolves could lead them to ®prey¯ and warn them whenever danger was near. So people began to take young wolf ®pups¯ from the wild and raise them. Before long, there were enough ®pet wolves¯ to provide a growing number of new ®puppies¯.