For as long as both ancient and modern societies have been in place, there have always been dogs present in the lives of humans. The dog-human connection is an intricate web that was formed when humans first started an age old relationship with these canine companions. The evolution of the dog is still disputed as it is still unknown as to why humans developed and domesticated a wild animal into the hundreds of breeds that are still present to this day.
To get a good idea as to what the orgins of a dog are, it is best to start at the beginning. Present day carnivores are descendents from a long evolutionary time line that begins with a creature known as Miacis. This early mammal is thought to be the ancestor of all present day carnivores which also includes felines, bears, hyenas and foxes as it is the first meat-eating mammal to exhibit teeth and other skeletal structures that are similar to modern carnivores. This mammal lived around 50 million years ago and gave rise to subsequent ancestors that continued the line of evolution until about 2 million years ago when all carnivores were fully diverged from each other.
It is theorized that dogs were first domesticated at least 10 thousand years ago. Based on evidence from DNA, most modern dog breeds are very closely related to the European Gray wolf. If given the opportunity, domestic dogs and wolves will interbreed which also suggests their close DNA relationship as they have the same number of chromosomes and both hold a few behavioral traits that make this coupling possible. It is also suggested that jackals and coyotes may have interbred with dogs at some point in the creation of specific breeds. Jackals and coyotes do not share the same traits as wolves do but this suggestion should not be completely ruled out.
The question as to what led to domestication is still a mystery. Wolves are naturally shy of humans and would also be in direct competion over the same prey with humans. It also seems unlikely that early humans would want to befriend a fierce predator. Some theories suggest that humans would find and keep wolf pups and raise them or that wolf packs that lived near human settlements began adapting to living near humans and accepting scraps which would lead to a natural selection towards an animal that would not shy away from humans as most wolves are naturally inclined to do. However it happened, at some point there was a divergence in the wolf lineage where some wolves would evolve into dogs. Whether this divergence was directly or indirectly caused by humans is still unknown.
Thanks to the large amount of genetic mutation and variability, dogs could be bred and selected to look and act different for whatever job they were intended for. This was the foundation of what are known as breeds. The earliest dog breeds have been found as fossils that date back to 4500 B.C. These breeds include mastiff types, spitz types, sheepdog types, sight hound types, and pointer types. Throughout human history, there may have been over one thousand different breeds of dogs. Today, around four hundred remain. This includes very ancient breeds like the Mastiff and Greyhound as well as the more recent breeds such as Cockerpoos and Labradoodles.
Whatever their orgins, dogs have had their place in the homes and hearts of humans for a very long time. They are still considered very important animals and still do specific jobs that humans or other animals cannot perform. It was probably the most pivital point in history when dogs evolved into what they are today. If it had never happened, would there be some other animal that sleeps on the couch all day or visits sick patients in hospitals? It would definitely be hard to imagine a world without dogs.
Sources:
Fogle, Bruce. The Encyclopedia of the Dog. New York, Dorling Kindersley Publishing. Inc: 1995.
Taylor, David. The Ultimate Dog Book. New York, Simon and Schuster: 1990.
http://www.scientificamerican.com/article.cfm?id=the-origin-of-dogs
