StoryImage( ‘/Images/Story//Auto-img-117389903125964.jpg’, ‘Photo by Dr. Robert A. Hedeen’, ‘Burt, a purebred boxer, seems to be astounded when told he descended from a wolf.‘);
StoryImage( ‘/Images/Story//Auto-img-117389910513261.jpg’, ‘Photo courtesy of http://img399.imageshack.us‘, ‘Ancestor of our favorite canine petsthe wolf.‘);
To the casual observer, the numerous breeds of domestic dogs would seem to have reached the acme of diversity by a single species. There are about 400 breeds of purebred dogs, though the American Kennel Club recognizes only about 162. Those who watched the recent telecast of the Westminster Clubs dog show from Madison Square Garden in New York City must have been amazed at the great variety of dogs exhibitedfrom the huge Great Dane to the tiny chihuahua. We cant but wonder what some paleontologist in the distant future will think when he digs up the bones of the different dogs man has created.
Yet, we know that all of the different varieties of dogs belong to the same species. This is primarily because they are theoretically capable of mating and producing fertile offspring. Size difference, however, may make the act of mating impossible, as in the case of a Saint Bernard attempting to mate with a Pekinese. Though not characters for differentiating species, it is interesting to note that all dogs have similar basic habits, instincts, and the working of their brains.
The evolutionary history of the dog is lost in the clouded mists of the past, but we do know with a high degree of certainty that the dog was the first animal domesticated by early man. The origin of dogs has perplexed zoologists for ages, and many theories have been put forth as to their ancestry, with none being generally accepted. The one thing, however, that most experts agree upon is that the dogs immediate ancestor is the wolf. In fact, a dog may be backcrossed to a wolf, and hybrids, though usually infertile, may be produced.
A plausible scenario of how this came to be is that an early man found an abandoned wolf pup and took it to his primitive abode, where he nurtured it. Raised in the friendly environment, the pup grew into an adult that was more docile than its parents and eventually became bonded to its surrogate parent. The young wolf proved to be of great value to the hunter in his quest for game and as a guard for his family, and the relationship was sealed.
If the captive wolf reverted to the aggressiveness of its parents, it was killed and another one procured who was less belligerent and was used as a breeder. Thusly, the use of selective inbreeding to produce a desired animal was instigated. And this practice has continued through time and accounts for the great variety of dogs we have today. Charles Darwin considered selective breeding while he was pondering how new species were formed, but rejected the idea. Though there is a plethora of different varieties of dogs, there is only one species, Canis domesticus.
Until recent years, it was generally believed that man had domesticated dogs no more that 10,000 years ago. However, recent DNA and other genetic tests has convinced anthropologist Dr. Colin Groves and others that dogs became associated with man and became domesticated some 100,000 years ago. One hundred thousand years ago is the generally believed time that modern man emerged. If true, Fido has been mans best friend for a considerable time.
The origin of the dogs immediate ancestor the wolf is obscured. Paleontologists have long speculated about how the family Canidae, the family that includes the dog, wolf, hyena, jackal, fox and many other flesh-eating mammals arose. The tree of the evolution of the Canidae is indeed complex and has many branches, one of which leads to the bears. Some of the early canine ancestors lived in trees when the ancestor of the modern horse was about the size of a large dog and had three toes. It took a considerable time for the first wolf to make an appearance on earth, but when man appeared, the dog evolved in a relatively short time.
When you look deeply into the eyes of your pet dog, you may be able to detect a bit of the wolfs presence in your beloved companion.
Dr. Robert Hedeen is a former resident of Marylands eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.
from the March 14-20, 2007, issue