The exact origin of the dog is unknown, yet it is an animal that is depicted even in the earliest drawings as a distinct animal. What is known about the dog is that it is the oldest domesticated animal. It seems that almost from the beginning there was a man and a dog and the two formed a relationship. Dogs have had a profound influence on the human race. From helping hunt for food to protecting, dogs have influenced the very evolution of humanity. Today's working dog reflects the amazing diversity of this species and the bond it has established with humankind. From the time humans began to realize the fact that dogs could be very valuable companions, we have bred them for certain tasks. Out of this have come the many breeds we have today. .
It seems likely that man first used dogs to help catch food and protect their caves. Early on, dogs were used to herd sheep and guard the flocks. Humans have long taken advantage of the keen scenting powers of dogs to search for fugitives or lost persons. Sled dogs have been vital to life and survival in many icy parts of North America. Today dogs are still used very widely around the world for a variety of different tasks that assist humans. Many of these duties include: Seeing eye dogs, hearing dogs, therapy dogs, service dogs, air scent dogs, trail and tracking dogs, disaster dogs, avalanche dogs, water dogs, war dogs, evidence dogs, and guard and watch dogs. .
Different types of search-and-rescue dogs are used everyday around the world to perform a wide variety of tasks. Imagine some kind of disaster like a flood, collapsed building, an earthquake, or an Alzheimer's patient who has wandered off. Using the dog's best sense, its nose, the search-and rescue dog has the ability to smell human scents in all types of conditions. Humans constantly shed microscopic flakes of skin. These flakes are carried through the air and land on the ground and in vegetation.