The Yorkie shares its ancient with all dog breeds, back to a creature that looked like a cross between a weasel and a fox, called Hesperocyonines. This primitive animal evolved in North America about 40 million years ago. Hesperocyonines gave to many canine species before it became 15 million years ago. Over the several million years that followed, prehistoric canids eventually developed into the first wild dogs, and later, some differentiated terrier types. At the time of the Roman invasion of England in 54 BCE, Julius Caesar’s legions observed small terriers used by hunters to chase into underground dens and and remain underground to fight and kill their quarry. This instinctive terrier behaviour is called “going to earth” or “going to ground”. The word terrier comes from the Latin word terra, meaning “earth”. Terrier-type dogs developed into different strains and were highly prized by their owners – and for good reason.