A dog is considered as man's best friend. Dogs became a part of our lives and keep us company especially when we're down. The question is when did this relationship start? Some studies record that man-dog relationship started about 30,000 years ago and the first ever transcribed evidence of a working relationship between the two was 14,000 years ago.

There are also reports that indicate that symbiotic relationship between humans and wolves started thousands of years ago. Symbiotic relationship can be defined as a kind of relationship where both organisms benefit from one another. This kind of relationship can be seen between man and dog. One good example is that humans give dogs food while dogs warn humans of impending danger.