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" All dogs are predators, but over thousands of generations, we’ve created sporting breeds to be exceptionally focused predators. All dogs like to dig and chase small prey, but terriers are superdriven to dig and find rodents. All dogs love to run, but greyhounds can run up to forty miles an hour, and huskies can run for hours and hours on end. All dogs have the natural ability to fight or wrestle with one another, but the bully breeds have been genetically engineered to fight to the death. The more pure the bloodline, the more that genetic “boost” will probably play a part in your dog’s behavior. That’s why some owners claim that their “mutts” make mellower pets, because, they theorize, their DNA has been somewhat diluted, and their breed-related drives diffused as a result. "
― Cesar Millan , How to Raise the Perfect Dog: Through Puppyhood and Beyond