No one knows exactly how many dogs exist but it is estimated that there are around 172,000,000 dogs in the world today, probably most residing in the United States. Some of the names people give to these canine mammals are bow wow, cur, doggy, Fido, flea bag, hound, man's best friend, mongrel, mutt, pooch, pup, puppy, stray, tail-wagger and little tyke. Amazing differeces in sizes and shapes of dogs have come out of the genetic structure of the Grey Wolf.
It's a fact that dogs are direct descendent's of grey wolves, an evolution that began over 30,000 years ago. The grey wolf resembles a German shepherd but closer examination reveals the wolves head is larger, the chest is narrower, paws are bigger and the legs are longer. Also the German Shepard's tail curls upward and the wolves tail is fairly straight.
The secret for this variety in breeds is because the DNA of dogs has so many changeable markers which makes the combinations are endless. Other animals, like cats, for instance, do not have so many changeable markers so we see very little change in their appearance between pedigrees.