Thousands of years ago, as humans began to settle in villages, the wolf emerged from the wild and made the startling leap to “man’s best friend.” Once domesticated, dogs would accompany human cultures down through the centuries and to the far corners of the world. The Victorian Age transformed them into the most varied species, and one of the most common pets, on the planet. In the 21st century, dogs are once more changing our world by their use in cutting-edge scientific research and lifesaving medical care.