Man has altered dogs since prehistoric times, starting with wolves. Dog breeds such as Bullmastiffs, Labrador Retrievers and St. Bernard’s were bred in order to better meet the needs of man.
Modern Dog explains that after wolves were domesticated by prehistoric man, contemporary man was able to breed traits into dogs such as protectiveness, and a proclivity toward hunting and pulling heavy loads. According to the American Bullmastiff Association, gamekeepers in England bred Bullmastiffs to have traits such as fearlessness, athleticism and loyalty. Labrador Training notes that Labrador Retrievers were bred from a long line of similar breeds known for their swimming and hunting skills, and an eagerness to please their masters. St. Bernard’s were bred for strength and endurance in order to haul large loads through snowy, mountainous terrain.
Today, humans do less arduous work, and dogs are now used more for companionship. However, dogs still have their traits for work. If dogs are not exercised regularly or do not participate in activities indicative to their breed, they lash out in manifold ways. Many times a dog destroys its house, bites its owner or develops psychological disorders because it is not doing the work it was originally designed for.