This post gathers scientific papers by geneticists, biologists, genetic behaviorists, behaviorists, and dog breeders comments on the genetic basis for temperament, behavior and personality traits, especially aggression.
These excerpts are not all specifically about pit bulls, but about the genetic basis of breed specific behaviors, temperament, especially aggression, in dogs in general and the differences noted in behavior, temperament, especially aggression, in different breeds of dogs. This collection is necessitated by the current propaganda that "it's all how you raise them" and “there is no evidence that one breed of dog is more aggressive than another.” This could not be farther from the truth.
And, of course, many dogs today are still purpose bred for desirable behavioral and temperament characteristics. Pit bulls are still bred for dogfighting. Dogfighting has never been more popular than today. And purpose bred fighting pit bulls are "rescued" and "rehabilitated" and end up in peoples' homes and then sometimes attack. (find three of those attacks on this list)
Some of these studies find that some personality trait characteristics and behaviors show more breed specific differences than others - and aggression and aggressive behaviors are two of the characteristics that are found to be the most highly heritable and show a great deal of difference between breeds.
Please note the 2016 genetic mapping study below by Zapata in which they successfully predict behaviors and temperament by mapping several dog breeds' genomes. This study directly contradicts the Animal Farm Foundation's slogans that "all dogs are individuals" and "looks (breeds) don't equal behavior".
Genetic mapping of canine fear and aggression, Isain Zapata, BMC Genomics, 2016
On why canines make such good models for human behavioral genetics studies:
“Many major breakthroughs in human genetics have resulted from studying isolated populations and multigenerational families. The advantages of those latter approaches, and others, are dramatically exaggerated in dogs: (i) There are approximately 400 dog breeds, each on the order of 100-fold less genetically-complex than the full population. Thus, compared to humans and their major ethnic groups, dogs are much more similar within breeds and much more different across breeds. (ii) Dogs are often part of a family or working environment and receive high levels of health care. Lastly, iii) dogs have more phenotypic variation than any other land mammal; and much of that variation is the result of “evolutionary” selection under domestication.”
Behavioral differences among breeds of domestic dogs (Canis lupus familiaris): Current status of the science, 2014
We review here scientific findings of breed differences in behavior from a wide range of methodologies with respect to both temperament traits and cognitive abilities to determine whether meaningful differences in behavior between breeds have been established. Although there is convincing scientific evidence for reliable differences between breeds and breed groups with respect to some behaviors (e.g., aggression, reactivity), the majority of studies that have measured breed differences in behavior have reported meaningful within-breed differences has well.Characterization of a Dopamine Transporter Polymorphism and Behavior in Belgian Malinois, Lisa Lit, BMC Genetics, 2013
The Belgian Malinois dog breed (MAL) is frequently used in law enforcement and military environments. Owners have reported seizures and unpredictable behavioral changes including dogs’ eyes “glazing over,” dogs’ lack of response to environmental stimuli, and loss of behavioral inhibition including owner-directed biting behavior. Dogs with severe behavioral changes may be euthanized as they can represent a danger to humans and other dogs.
The single copy allele of DAT-VNTR is associated with owner-reported seizures, loss of responsiveness to environmental stimuli, episodic aggression, and hyper-vigilance in MAL. (NOTE: pit bull owners describe the same kind of behaviors in their pit bulls. Pit bull owners have described this as "going into the red zone", or "the lights going out.")
UC Davis Veterinary Genetics Laboratory now offers a test identify dogs with this potentially dangerous genotype based on this researchCanine Analogs of Human Personality Factors, 2010
Canine and human personality similarities are argued to have their origin in biogenetic factors stemming from common evolutionary sources and from canine breeding for human compatibility and assistance with human tasks.Single-Nucleotide-Polymorphism-Based Association Mapping of Dog Stereotypes, Paul Jones, Genetics, June 2008 vol. 179 no. 2
Phenotypic stereotypes are traits, often polygenic, that have been stringently selected to conform to specific criteria. In dogs, Canis familiaris, stereotypes result from breed standards set for conformation, performance (behaviors), etc. As a consequence, phenotypic values measured on a few individuals are representative of the breed stereotype. We used DNA samples isolated from 148 dog breeds to associate SNP markers with breed stereotypes. Using size as a trait to test the method, we identified six significant quantitative trait loci (QTL) on five chromosomes that include candidate genes appropriate to regulation of size (e.g., IGF1, IGF2BP2 SMAD2, etc.). Analysis of other morphological stereotypes, also under extreme selection, identified many additional significant loci. Less well-documented data for behavioral stereotypes tentatively identified loci for herding, pointing, boldness, and trainability.
Canine Behavioral Genetics: Pointing Out the Phenotypes and Herding up the Genes, 2008, Spady, Tyrone C.
An astonishing amount of behavioral variation is captured within the more than 350 breeds of dog recognized worldwide. Inherent in observations of dog behavior is the notion that much of what is observed is breed specific and will persist, even in the absence of training or motivation. Thus, herding, pointing, tracking, hunting, and so forth are likely to be controlled, at least in part, at the genetic level....The phenotypic radiation of the dog has been the product of restricted gene flow and generations of intense artificial selection....Behavioral variation is...captured within different breeds. A long-stated goal of behaviorists is to identify genes that control behavioral traits. Traits that define specific breeds....Certainly aggression has been considered at length. However, the social and political ramifications of identifying genes that control this complex behavior are not lost...http://1.usa.gov/1M0OTBY
Structure and Variation of Three Canine Genes Involved in Serotonin Binding and Transport, 2005, Journal of Heredity
Aggressive behavior is the most frequently encountered behavioral problem in dogs. Abnormalities in brain serotonin metabolism have been described in aggressive dogs. We studied canine serotonergic genes to investigate genetic factors underlying canine aggression.Temperament traits of 23 breeds, including aggression, related to genes, 2004
Various canine breeds are remarkably different from each other not only in their sizes and shapes but also in behavioral traits,suggesting that some of them are under genetic control... A group of breeds in which the alleles 447b, 498 and 549 were frequent tended toward high scores in aggression-related behavioral traits than that with frequent alleles 435 and 447a."Overview of the International Workshop on Canine Genetics, 1999,
The dog has an amazing repertoire of breed-specific characteristics. The consistent and predictable suite of phenotypes associated with each breed, including for example, coat color, morphological appearance, behavioral characteristics, and, in some cases, breed-specific diseases, attests to the heritability of these traits.Determination of behavioural traits of pure-bred dogs using factor analysis and cluster analysis; a comparison of studies in the USA and UK, 1998
The questionnaire survey of Hart and Hart (1985,Journal of the American Veterinary Medical Association186, 1811–1815) ranked the 56 most popular breeds of dog in the USA on 13 behavioural traits and is compared here with results of a similar survey conducted on the 49 most popular breeds in the UK. Of the 36 breeds in common between the studies, 24 were similar for the traits aggressivity, reactivity and ease of house training between the two countries.A survey of the behavioural characteristics of pure-bred dogs in the United Kingdom, 1996
…factor analysis was used to extract three underlying traits, labelled aggressivity, reactivity and immaturity. On the basis of these traits, eight groups of breeds were derived. Membership of these groups did not correspond exactly with any of the four existing breed classification systems (Mégnin, the Fédération Cynologique International, ancient breeds and Kennel Club of Great Britain), but significant differences between Kennel Club groups were found on all three traits.Selecting pet dogs on the basis of cluster analysis of breed behavior profiles and gender, 1985
Three factors, referred to as reactivity, aggression, and trainability, accounted for 81% of the variance in the 13 behavioral traits. Subsequently, a cluster analysis was performed to generate 7 clusters of dog breeds on the basis of similarity in scores for each of the 3 main factors. The clusters reflected to some degree the conventional groupings of dogs into working, sporting, hound, and terrier breeds.Behavioral profiles of dog breeds, 1985
Breed behavior profiles were obtained by a method that was quantitative and free of personal biases. The profiles concerned 13 traits, eg, excitability, snapping at children, watchdog barking, and affection demand, which are of interest to people wanting dogs as pets. The results indicated that some behavioral traits discriminate between breeds better than others.
JOY TIZ MS, JD, Owner of Wildhaus Kennels GSDs
Yes, it's true. Temperament is a function of genetics. It is inherited, not developed. A dog's core temperament never changes. Some behaviors can be modified through training, but the temperament itself never changes. For example, a high energy dervish of a dog isn't going to learn to be a laid back, low energy dog. But, the dog can be taught to control his energy, to an extent.
Most dog owners absolutely refuse to believe this. If I only had a dollar for every time someone has told me "It's all in how they're raised!" ... No, it's not. It's all in how their DNA came together. A dog with foul temperament will always be a dog with foul temperament, no matter how wonderful the environment. A dog with sound, stable temperament will always be a sound stable dog, even in a lousy environment.
Good early handling, training and socialization will help develop desirable traits in the dog, but those traits have to be there. Ball drive is a good example, since it forms the foundation for so many types of work. Some dogs aren't interested in chasing a ball. If the dog does enjoy ball games, a good trainer can build that up and bring it out to it's highest possible level, but the drive itself is innate. One cannot install a drive.
What then, is the impact of early handling, training and socializing, if temperament is genetic? Why bother? To use a human analogy, why can't all humans become Olympic athletes? Because not all humans have the right genetic equipment. But, if you are blessed with the right stuff, the right training can develop those innate abilities to their highest level.
Behaviorists, Biologists, Geneticists, Veterinarians, Behavioral Geneticists, and other science professionals
Why does My Dog Act That Way?: A complete Guide to Your Dog’s Personality, Stanley Coren, 2006
Fortunately, there is some data to suggest that we can still make predictions of a mixed breed dog’s personality and behavioral predispositions without knowing much about its parentage. John Paul Scott and John L. Fuller carried out a series of selective breeding experiments at the Jackson Laboratories in Bar Harbor, Maine. By a happy chance, their results revealed a simple rule that seems to work. Their general conclusion was that a mixed breed dog is most likely to act like the breed it most looks like.Michael d. Breed, Ph.D, University of Colorado, Dept. of Ecology & Evolutionary Biology
That much of dog behavior has genetic underpinnings is patently obvious. Differences in temperament and ability among breeds are well known. These differences are generally associated with the purposes for which the breed was created.
Virtually all of quotes from the Animal Science Experts On Pit Bulls list references the genetic basis of pit bull aggression