The origin of the domestic dog is not clear. It is known that the dog was the first domesticated species.   The domestic dog is a member of the genus Canis (canines), which forms part of the wolf-like canids ,  and is the most widely abundant terrestrial carnivore.      The closest living relative of the dog is the gray wolf and there is no evidence of any other canine contributing to its genetic lineage.     The dog and the extant gray wolf form two sister clades ,    with modern wolves not closely related to the wolves that were first domesticated.   The archaeological record shows the first undisputed dog remains buried beside humans 14,700 years ago,  with disputed remains occurring 36,000 years ago.  These dates imply that the earliest dogs arose in the time of human hunter-gatherers and not agriculturists .  
The other offender in causing left side pain in the lower area of the back is the gallbladder. The gallbladder stores bile that is produced by the liver and this helps the body with food digestion. Problems with your gallbladder are fairly common in industrialized societies. The refined and processed food eaten in these cultures takes a heavy toll on the gallbladder. Recent studies show that over a million Americans have gallstones can have gall stones or a diseased gallbladder and the result is almost always the same. Remove the gallbladder and you remove the pain.
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