Pit bulls have been in the news a lot lately. Journalist Bronwen Dickey has written a popular book about them. There are many articles online and in print about them, theorizing about “locking jaws” and “propensity to bite.” There are countervailing articles arguing that we should look at “the deed not the breed.” Several cities have gotten rid of their breed-specific legislation aimed at pit bulls, while one large city, Montreal, recently adopted a pit-bull ban only to have a court put the law on hold.

Denver is one city that has a pit-bull ban. It prohibits: “Any dog that is an American Pit Bull Terrier, American Staffordshire Terrier, Staffordshire Bull Terrier, or any dog displaying the majority of physical traits of any one (1) or more of the above breeds, or any dog exhibiting those distinguishing characteristics which substantially conform to the standards established by the American Kennel Club or United Kennel Club for any of the above breeds.

Denver’s ordinance is more narrowly drawn than some pit-bull bans, but even Denver’s law leaves dog experts scratching their heads as to what dogs it applies to and what ones it doesn’t. The American Kennel Club and United Kennel Club standards for the three breeds named in Denver’s ordinance allow a variation in weight of anywhere from 14 to 60 pounds, and weights can be even higher if they are in proportion to body size. The allowed height range, measured in inches at the shoulder, is anywhere from 14 to 21 inches, and again, the height can be greater if it is in proportion. The three standards, taken together, allow every possible coat color.

Related: What It’s Like To Live Within The Largest Breed Ban In The World

The Denver ordinance bans dogs that have the “distinguishing characteristics” of the three breeds, but the only “distinguishing characteristics” that are consistent in the three breed standards are a broad skull and a short coat. Other physical characteristics like height, weight, and color vary so widely and cover such a broad range that they would probably apply to a majority of dogs in the United States today. But even the “distinguishing characteristics” of short coat and broad head are not very distinguishing. Dalmatians, Basenjis, Beagles, Rat Terriers, and French Bulldogs have short coats, as do many other breeds. The little Japanese Chin has a “large broad head,” and the tiny Pug has a “large, massive” skull, according to their breed standards.

As many people have pointed out, the problem with pit-bull bans is that “pit bull” is not a particular breed but an amalgam of characteristics. That means that anyone trying to define a “pit bull” has to fall back on descriptions of what the dogs look like, since they can’t go by the pedigree. But if you define a dog by what it looks like instead of by its genetic background, you cannot very well say that the dog has inherited characteristics. It is this logical conundrum, combined with the fact that dog-bite statistics don’t support the idea that “pit bull” breeds are disproportionately dangerous in the first place, that have led more and more cities to get rid of pit-bull bans or decline to adopt them.

sleeping pit bull

Each mutt, including this sleeping pit bull mix, is sui generis. Source: FreeImages

Yet many people cling to the idea that dogs who have a physical resemblance to each other must have similar behavior characteristics. We don’t think that way about people, or cats, or rabbits, or ferrets, yet that is how we think about dogs. We would never assume that all people who have blocky heads are vicious, for example, or that all cats with long hair are mean. So why do we make assumptions about dogs based solely on how they look?

The answer may be that dogs, unlike people and cats, have been deliberately inbred to make their appearance and behavior patterns more homogeneous. We are familiar with sheepdog breeds that have an uncanny ability to herd sheep, with “sighthounds” that track game visually, and with certain hunting breeds that instinctively go into a “point” when they detect a game bird. It seems only natural to extend that kind of thinking to expect that dogs who look somewhat like the fighting dogs of the 1800s will be fighters by disposition.

Related: Reading This Redefined How We Think About Pit Bulls

What most people don’t realize is that the “natural” behaviors of the herding dog, the sighthound, and the pointer are not natural at all. Those behaviors, along with the characteristic appearances of those breeds, have been produced by decades of breeding closely related animals to each other (“inbreeding”) to increase the chances that the genes for the desired behavior and appearance will become “fixed” in the bloodline. Dog breeders have used the technique of inbreeding more than the breeders of any other animal. It is common for dog breeders to breed a dog to its granddaughter, or a half-brother to a half-sister, or an uncle to a niece, all in an effort to make the behavior and appearance of the offspring as predictable as possible.

The degree of inbreeding of an individual animal is measured by a value called the “inbreeding coefficient.” Without going into the genetics of inbreeding in detail, it suffices for our purposes to know that many show dogs today have inbreeding coefficients of 6.25% (equivalent to being the offspring of a mating of first cousins) or more. Inbreeding is a double-edge sword. Breeding two closely related dogs that have a desired characteristic — like a narrow head in Collies — can greatly increase the probability that their offspring will have that characteristic. But it will also increase the chances that the offspring will be unhealthy. If the inbreeding coefficient of a litter is too high, some of the puppies may be unhealthy and some may even die. So dog breeders often stick to a range of inbreeding coefficient of 6.25% to 12.5%, trying to balance increased predictability in appearance and behavior against higher odds of genetic disease.

Genetics is very complicated, and this is a simplified summary. Here’s the crucial point for our discussion of the behavior of pit bull mixes, though. When a dog with an inbreeding coefficient that is greater than zero is bred to an unrelated dog, all the offspring will have inbreeding coefficients of zero.

In other words, when we look at mixed-breed dogs, we cannot assume that their physical appearance says anything at all about their behavior, any more than we can with people. Breeding an inbred purebred dog to an unrelated dog “resets” the genome of the puppies. The tight control over appearance and behavior that is represented by a high inbreeding coefficient vanishes. That is why mixed-breed puppies are healthier than inbred purebreds even when the puppies have inbred parents.

purebred dogs

Purebred dogs can show remarkable similarity in appearance and behavior. Source: FreeImages

The great majority of cats have inbreeding coefficients of zero, because the great majority of cats are not purebred. That’s why we have never learned to make the assumption that the appearance of cats correlates with their behavior. The use of inbreeding in dog breeds over the last 100 years and more has given people a false idea that behavior in the dog is reliably predictable from looks. It isn’t — at least not in mixed breed dogs.

So we should never make an assumption about the behavior of any mixed-breed dog based on its appearance. If a mixed breed dog looks kind of like a sheepdog it might possibly want to herd sheep, but it also very possibly won’t. If it looks like a fighting dog from the 1800s, it might be dog-aggressive, but it very possibly won’t.

Related: Fighting Back: What To Ask For Instead Of Breed-Specific Legislation

But what about breeds like the American Staffordshire Terrier that are often included in ordinances like Denver’s? We know the pedigrees of those dogs and a great many of them are inbred, so can’t we predict their behavior from their looks? A corollary of dog breeders seeking to fix type in their dogs by the use of inbreeding is that they can fix good behavior as well as bad. For a long time now, many of the people who breed American Staffordshire Terriers and other so-called “pit” breeds for the show ring have been working very hard to breed away from aggression. They don’t like the stereotype of their breeds as being unpredictable and dangerous. One prominent AmStaff breeder describes their dogs as quiet, obedient, courageous, affectionate, and stable. This is the temperament that they are trying to fix in their dogs, not aggression.

The purebred dog industry is in decline because the old idea that purebred dogs are superior to mixed breeds is dying out. Shelters and rescues are taking more and more market share away from purebred dog breeders. Indeed, as the popularity of pit-bull mixes demonstrates, today it is fashionable to adopt, not shop. As these trends continue, highly inbred dogs will make up a smaller and smaller proportion of the dogs we see. The unnatural phenomenon of dog appearance and behavior being tightly linked by selective breeding will disappear. Legislators will take it for granted that in drafting dangerous-dog ordinances, they must look at “the deed, not the breed.”

We aren’t there yet, as the recent law in Montreal shows, but we are making progress.


PupJournal is proudly hosting National #PitBullWeek, or #NPBW, to celebrate blocky-headed wigglebutts, otherwise known as “pit bulls.” It’s time these pups are able to live their lives free from discrimination and harm. You can find articles, videos, and adoptable dogs on our National Pit Bull Week page and on Facebook. Join us by tagging National #PitBullWeek, or #NPBW!


Header images via Max Schneider / Flickr and Chris / Flickr

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