We are familiar with the famous saying "dog is a man's best friend," but no one could figure out exactly why this particular animal carries the capability of being so friendly toward humans. According to a study published Wednesday, the reason behind humans and dogs striking a common cord might be because the latter descended from wolves. The study found that hyper-social canines carry variants of the genes GTF2I and GTF2IRD1, the deletion of which, in humans, triggers the Williams-Beuren Syndrome, or more commonly known as the Williams syndrome. Bridgett vonHoldt of Princeton University and her colleagues studied a portion of DNA in dogs that included 29 genes. They noticed that deletion of part or all of this section due to prolonged domestication seemed to cause the overtly friendly nature in dogs.