Dogs are considered man's best friend because their presence provides many beneficial effects and they form close, loving bonds with their owners. Dogs were also the first domesticated species so they have evolved to have a very close relationship with humans.
Dogs have been domesticated for approximately 15,000 years. Working dogs provide many beneficial services, from helping blind people navigate the streets to rescuing lost hikers. Dogs can even learn to detect conditions such as impending seizures and direct their owners to a safe place. They herd and protect livestock and guard their families as well.
However, pet dogs also provide significant benefits to their owners. They help alleviate loneliness and can give depressed people a reason to keep going. They provide support to people feeling grief or loss and can even help people make new human friends by providing an easy topic of conversation. Research shows that people suffering from Alzheimer's disease are happier and more social when they are around dogs. Studies have shown that interactions between dogs and humans release oxytocin in both parties. Oxytocin is a hormone that facilitates love and bonding.
People who have pet dogs often are healthier. Care of the dog requires them to exercise regularly and go outdoors, which can improve both mental and physical health. Just having a pet dog can significantly increase a person's chances of survival after a heart attack. Studies also show that the presence of a dog can reduce blood pressure and stress.