Despite the many kinds and sizes, all today's dog breeds are descended from the Grey Wolf. The domestication began more than 12,000 years ago in the Northern Hemisphere. Archaeological finds have proved that the real differentiations in the sizes of domestic dog can be dated to 7000 BC. This trend was improved in the Roman Era, when the characteristics of many current breeds were defined. The Infographic follows the InternationalKennel Club classification standards, while the identification method is inspired by David Alderton's Eyewitness handbook of dogs.