EVOLUTION OF THE DOG
The dog traces its ancestry back to a five-toed, weasellike animal called Miacis, which
lived in the Eocene epoch about 40 million years ago. This animal was the forebear of the
cat, raccoon, bear, hyena, and civet, as well as of the wolf, fox, jackal, and dog. 
Miacis, undoubtedly a tree climber, probably also
lived in a den. Like all den dwellers, it no doubt left its quarters for toilet functions
so that the den would remain clean. The ease of housebreaking a modern dog probably harks
back to this instinct. Next in evolutionary line from Miacis was an Oligocene animal
called Cynodictis, which somewhat resembled the modern dog. Cynodictis lived about
20 million years ago. Its fifth toe, which would eventually become the dewclaw, showed
signs of shortening. Cynodictis had 42 teeth and probably the anal glands that a dog still
has. Cynodictis was also developing feet and toes suited for running. The modern civet--a
"living fossil"--resembles that ancient animal (see Civet). After a few
more intermediate stages the evolution of the dog moved on to the extremely doglike animal
called Tomarctus, which lived about 10 million years ago during the late Miocene
epoch. Tomarctus probably developed the strong social instincts that still prevail in the
dog and most of its close relatives, excluding the fox. The Canidae, the family that
includes the true dog and its close relatives, stemmed directly from Tomarctus. Members of
the genus Canis--which includes the dog, wolf, and jackal--developed into their
present form about a million years ago during the Pleistocene epoch.
Home Page - Anatomy of
the Dog - Life History of the Dog - Breeds
of Dogs - Choosing a Dog - Caring
for a Dog - Canine Pests & Diseases
Training a Dog - The
Partnership of Dog & Human - Dog Terms - Some Noteworthy Dogs in History