Pit bull mix origin: where this mixed breed really comes from

Part 1

What counts as a pit bull mix

Researchers studying shelter dogs grouped the American Pit Bull Terrier, the American Staffordshire Terrier, and the Staffordshire Bull Terrier together as 'pit bull types,' along with any dog that looked like a mix of them. Some breeders of the American Pit Bull Terrier argue that their breed alone deserves the name 'pit bull,' even though the term is used far more broadly in everyday language and in law.

Part 2

The origin of the bulldog and terrier lines behind the mix

To understand your dog's roots, it helps to go back to 19th century England. Old English Bulldogs were bred for bull-baiting, a blood sport that used the dogs' strength and grip against tethered bulls. Britain banned bull-baiting and similar blood sports in 1835 under new animal welfare law. Breeders then crossed these bulldogs with terriers, aiming to combine the bulldog's strength and athleticism with the terrier's gameness and agility, producing what became known as the bull and terrier. That cross also suited dog fighting and ratting, which moved into hidden pits once bull-baiting itself was outlawed.

These bull and terrier dogs then crossed the Atlantic with immigrants from the British Isles, arriving in the United States roughly between 1845 and 1860. Once in America, the dogs took on new jobs beyond fighting, including work as catch dogs for semi-wild cattle and hogs on farms and ranches. Breeders also selected against dogs that turned on handlers during matches, culling any dog that bit a person.

Part 3

How pit bull mixes became common in the US

If you look back far enough, you find widespread crossbreeding rather than tight breed clubs, since fanciers bred for fighting ability more than for pedigree. Fanciers of the time cared more about which dogs were game and could fight well than about a fixed pedigree, so they bred accordingly, regardless of ancestry. The United Kennel Club began registering the American Pit Bull Terrier in 1898. Visual identification of pit bull type dogs matched DNA results only 33 to 75 percent of the time in one study.

Part 4

What a pit bull mix actually looks like genetically

If your dog has been labeled a pit bull mix by a shelter, it is worth knowing how unreliable that visual call can be. In a study at four Florida shelters, staff and veterinarians who visually identified dogs as pit bull type matched DNA results only 33 to 75 percent of the time, depending on the assessor. Dogs that had no DNA evidence of pit bull-type breeds were still labeled pit bulls by at least one staff member 0 to 48 percent of the time. Overall, about one in five dogs with pit bull heritage in their DNA were missed, and about one in three dogs without that DNA were labeled pit bulls anyway. As the study authors put it, mixing breeds is not like mixing paint, because dogs carry many genetic traits that do not blend into one predictable look.

Part 5

Common pairings seen in pit bull mixes today

Studies have found that even shelter staff and veterinarians often disagree with each other and with DNA results when they try to identify a dog as a pit bull type by sight.