The Rottweiler's ancestors were the drover's dogs accompanying the herds the Romans brought with them when invading Europe. The controllable herding and guarding instincts were recognized by the Germans, and dogs were selectively bred for these traits. As need for its services diminished, the Rottweiler almost fell into extinction. In the early 1900s, a newly formed club established a breed standard. The breed has not appreciably changed since that time.  (Source: American Kennel Club)