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Ericwd9's thread sent me back to the internet to try to find some articles I'd run across in previous searches for genetic studies of dogs, Still no luck with those but I've found some interesting new information.
Keep in mind that I'm writing all this from my layman's POV, which is why I always try to provide links to the sources.
Briefly on Pits:
"Pit Bulls are not one specific breed, but rather a classification of several breeds (Staffordshire Terriers, American Pit Bull Terriers, American Bullies, American Staffordshire Terriers, and sometimes American Bulldogs and Bull Terriers).
These were originally bred from Old English Bulldogs, who gained popularity in the 1800s on the British Isles in a blood sport known as “bull baiting” (tying a bull to an iron stake that gave him approximately 30 feet to move, and then setting dogs on it in an attempt to immobilize the bull for public entertainment). Bloodsports were outlawed in 1835 in the UK, so “rat-baiting” and dogfighting – which were easier to hide from police – became the new sports of popularity. Bulldogs were crossed with Terriers and then released into a “pit” to chase and kill rats or fight one another, thus beginning the “Pit Bull” type of dog.
In the early stages of America, many immigrants brought their treasured Pit Bull dogs over as part of their families. Though the dogs were bred for fighting sports, they were also incredibly intelligent and friendly. They were used for a variety of jobs that included farming, protecting the family from predators, watching the children, and providing companionship. As the popularity of newspapers and media grew throughout the years, many of these dogs were brought to attention for the number of exemplary deeds they performed.
How, you might ask, could a dog that was bred to fight aggressively also be kind to humans? The answer is actually in their breeding. Pit Bulls that bit handlers were put down and of no use to the owners, so they were bred and trained to be gentle with humans — a trait that most are still well-known for to this day."
https://barkpost.com/good/pit-bulls-history-of-americas-dog/
-------------
With the exception of the last paragraph, I've read this brief history in several sources, so I'm accepting it as probable truth. The last paragraph makes sense if you understand that they were inadvertently selecting certain non-aggressive genetic tendencies to owner/handler. I'd guess that the fighting dogs were selectively bred for their unprovoked aggressive tendencies, to go after the bulls. The studies I've been trying to find wrote of a divergence in the breed with a surviving population segment "lacking" certain dangerous tendencies. There's a second separate suggestion that the aggressive tendencies usually appear in dogs under 2 years old.
---------------
And then:
"In the 1960s, ’70s, and particularly ’80s, dogfighting began to see a resurgence. As people saw more of these large dogs in spiked collars on street corners, a natural fear evolved. In conjunction with fighting, it was not uncommon for owners of these dogs to be abusive and encouraged aggressive behaviors to boost their intimidating image. They also took to breeding their own dogs outside of American Kennel Club and American Dog Breeding Association regulations, leading to an overpopulation of Pit Bull types. These things still take place today, despite the outlawing of all dog fighting in 1978, and continue to contribute to the negative image of the Pit Bull."
https://barkpost.com/good/pit-bulls-history-of-americas-dog/
-----------------
Irresponsible breeding for negative behaviors came back with a vengeance. If the studies I can't find are valid then it may simply be luck of the draw, Good Pit or Bad Pit. I prefer to avoid them all since they aren't wearing badges.
----------------
Now for the current studies
"With the availability of affordable DNA analysis that can provide information about hundreds of thousands - or even millions - of markers, we have started to look for the genetic basis of behavior at the level of the gene. A few genes have been identified that are associated with specific behavioral traits in dogs, like xxxxxxxx (Bridgett). There is also a growing number of studies that looked for the genetic basis of behavioral differences in dog. But as I explained in an earlier post, the associations of behavior with genes have been generally weak and not especially useful for identifying genes of major effect or improving traits through genomic selection.
A new study, however, is a game-changer (MacLean et al 2019). It has been made available before submission for publication, so it has not been subject to peer review and you should keep that in mind. But what it offers is a tantalizing first look at links between genes and behavior in dogs.
Previous studies have looked for variation in genes that could account for differences in behavior in a group of dogs. The strength of the association between genetics and a trait is indicated by a statistic called "heritability", and in most studies of behavioral traits in dogs of a particular breed, the heritability was found to be low; i.e., variations in behavior were not associated with genetics.
Instead of focusing on a particular breed, the new study looked for major differences in behavior and genetics across many breeds. And here, they were successful.
In this study, a large set of behavioral assessments from CBARQ testing of > 17,000 dogs was paired with DNA genotyping data for > 5,600 dogs of 141 breeds by combining information from two separate studies (Hayward et al. and Parker et al.) that used the current gold-standard analysis platform (high density SNP markers; > 100,000). They identified 14 behavioral traits of interest and looked for differences in the behavior of breeds that appeared to be associated with differences in the DNA, which would tell them the heritability of these specific traits.
What they found was fascinating.
In this graph, the behaviors they looked at are indicated down the y-axis, and the strength of the association between genetics and the trait, i.e., heritability, is on the x-axis. The stronger the association, the higher the heritability. The grey dogs are measurements of heritability made on dogs of the same breed. The green and yellow dogs display heritability of those same traits when the associations are made looking across breeds.
![maclean-2019_1.png]()
You can see here that heritabilities determined from dogs of the same breed are generally low, less than about 0.3, which means that 30% or less of the variations in behavior can be attributed to variations in genotype.
But when you compare across breeds, the average heritabilities are high, from about 0.4 (40% of variation explained) to more than 0.7 (70% of variation explained.
This is very exciting, because it's the first time we have been able to detect strong links between genes and behavior.
This is a game-changer. Our understanding of the genetic basis of behavior in dogs has gone molecular.
We now have large databases for both behavior and genotype, and these will continue to grow in size because the methodology for both is standardized (CBARQ for behavior and high-density SNP for genotype).
These allow us to do analyses like the one below, which is a "heat map" that depicts the behavioral scores by breed displayed along with the dendrogram displaying their genetic relatedness. You can easily find the sporting dogs because they are high in trainability, and the small breeds like the chihuahua, rat terrier, and miniature pinscher stand out for scoring high in traits that we might describe as reactive or "fiesty" (e.g., aggression, fear). The herding breeds score high in trainability while the hounds are low. And now we are finally able to explore the genetic basis for major breed-specific differences in behavioral traits among dog breeds.*
![maclean-2019-1 heatmap.jpg]()
https://www.instituteofcaninebiology.org/blog/the-genetics-of-canine-behavior-goes-molecular
--------------------
When you look at the "heat map" you see some surprises.
Below are links to an interview with two of the papers authors,
"Heritability, in the narrow sense, means the proportion of variation in a specific trait that is explained by genetic similarity among individuals that you measured."
"…heritability is just a measure of how much genetic factors explain phenotypic variation. In cases of extremely strong selection, traits can become fixed, in which case there is no heritability (because there is no variance to explain). This is a distinction between heritability and heredity. For example, humans have two legs, which is an entirely hereditary trait, but there is no heritability to speak of because there is no variation to explain. So, if a trait has a genetic basis, and there is relaxed selection allowing for phenotypic variance, we actually have a very good shot at detecting its heritable nature under these conditions!"
https://winter2019.iaabcjournal.org/heritable-breed-behavior/
and to the original study,
https://www.biorxiv.org/content/10.1101/509315v1.full?versioned=true
If you scan thru this paper, you'll eventually get to the tendencies that group together
https://bmcgenomics.biomedcentral.com/articles/10.1186/s12864-016-2936-3
"Our PCA of breed genotypes and phenotypes indicates that some types of fear and aggression are related to each other (stranger-oriented fear and dog-/stranger-directed aggression), but are distinct from others such as owner-directed aggression. This pattern was mirrored by the results of our behavioral GWAS’s which identified two genome loci associated with the former (also shared with dog-oriented fear) and another two associated with the latter (also shared with dog rivalry). Notably, owner-directed aggression and dog rivalry are associated with the same variation in IGF1 that is known to have the greatest contribution to small-size across dog breeds (the former trait is also associated with the small-size variant at the IGF1 receptor gene). This finding is consistent with previous reports that i) there is a highly-significant correlation between the behaviors of owner-directed aggression and dog rivalry, ii) this correlation is independent of dog- and stranger-directed aggression, and iii) these behaviors are associated with breeds of small to medium size [54–56]. As owner personality does not necessarily predispose to owner-directed aggression, it is thus an apparent dog trait [57]. Some of those studies also showed a correlation between small size and stranger-oriented fear and aggression, dog-oriented fear, separation anxiety, and touch sensitivity [56]. That is supported by our finding in the confirmation GWAS’s that the same small-dog IGF1 allele is associated with the latter three traits. It is unclear whether the behavioral associations with small-size gene variants are due to developmental, physiological or psychological effects; all seem probable."
--------------
![maclean-2019_1.png]()
Single Breed vs Multiple Breeds
![maclean-2019-1 heatmap.jpg]()
On the left is the dendogram displaying genetic relatedness. On the right is the behavioral CBARQ scores by breed.
Keep in mind that I'm writing all this from my layman's POV, which is why I always try to provide links to the sources.
Briefly on Pits:
"Pit Bulls are not one specific breed, but rather a classification of several breeds (Staffordshire Terriers, American Pit Bull Terriers, American Bullies, American Staffordshire Terriers, and sometimes American Bulldogs and Bull Terriers).
These were originally bred from Old English Bulldogs, who gained popularity in the 1800s on the British Isles in a blood sport known as “bull baiting” (tying a bull to an iron stake that gave him approximately 30 feet to move, and then setting dogs on it in an attempt to immobilize the bull for public entertainment). Bloodsports were outlawed in 1835 in the UK, so “rat-baiting” and dogfighting – which were easier to hide from police – became the new sports of popularity. Bulldogs were crossed with Terriers and then released into a “pit” to chase and kill rats or fight one another, thus beginning the “Pit Bull” type of dog.
In the early stages of America, many immigrants brought their treasured Pit Bull dogs over as part of their families. Though the dogs were bred for fighting sports, they were also incredibly intelligent and friendly. They were used for a variety of jobs that included farming, protecting the family from predators, watching the children, and providing companionship. As the popularity of newspapers and media grew throughout the years, many of these dogs were brought to attention for the number of exemplary deeds they performed.
How, you might ask, could a dog that was bred to fight aggressively also be kind to humans? The answer is actually in their breeding. Pit Bulls that bit handlers were put down and of no use to the owners, so they were bred and trained to be gentle with humans — a trait that most are still well-known for to this day."
https://barkpost.com/good/pit-bulls-history-of-americas-dog/
-------------
With the exception of the last paragraph, I've read this brief history in several sources, so I'm accepting it as probable truth. The last paragraph makes sense if you understand that they were inadvertently selecting certain non-aggressive genetic tendencies to owner/handler. I'd guess that the fighting dogs were selectively bred for their unprovoked aggressive tendencies, to go after the bulls. The studies I've been trying to find wrote of a divergence in the breed with a surviving population segment "lacking" certain dangerous tendencies. There's a second separate suggestion that the aggressive tendencies usually appear in dogs under 2 years old.
---------------
And then:
"In the 1960s, ’70s, and particularly ’80s, dogfighting began to see a resurgence. As people saw more of these large dogs in spiked collars on street corners, a natural fear evolved. In conjunction with fighting, it was not uncommon for owners of these dogs to be abusive and encouraged aggressive behaviors to boost their intimidating image. They also took to breeding their own dogs outside of American Kennel Club and American Dog Breeding Association regulations, leading to an overpopulation of Pit Bull types. These things still take place today, despite the outlawing of all dog fighting in 1978, and continue to contribute to the negative image of the Pit Bull."
https://barkpost.com/good/pit-bulls-history-of-americas-dog/
-----------------
Irresponsible breeding for negative behaviors came back with a vengeance. If the studies I can't find are valid then it may simply be luck of the draw, Good Pit or Bad Pit. I prefer to avoid them all since they aren't wearing badges.
----------------
Now for the current studies
"With the availability of affordable DNA analysis that can provide information about hundreds of thousands - or even millions - of markers, we have started to look for the genetic basis of behavior at the level of the gene. A few genes have been identified that are associated with specific behavioral traits in dogs, like xxxxxxxx (Bridgett). There is also a growing number of studies that looked for the genetic basis of behavioral differences in dog. But as I explained in an earlier post, the associations of behavior with genes have been generally weak and not especially useful for identifying genes of major effect or improving traits through genomic selection.
A new study, however, is a game-changer (MacLean et al 2019). It has been made available before submission for publication, so it has not been subject to peer review and you should keep that in mind. But what it offers is a tantalizing first look at links between genes and behavior in dogs.
Previous studies have looked for variation in genes that could account for differences in behavior in a group of dogs. The strength of the association between genetics and a trait is indicated by a statistic called "heritability", and in most studies of behavioral traits in dogs of a particular breed, the heritability was found to be low; i.e., variations in behavior were not associated with genetics.
Instead of focusing on a particular breed, the new study looked for major differences in behavior and genetics across many breeds. And here, they were successful.
In this study, a large set of behavioral assessments from CBARQ testing of > 17,000 dogs was paired with DNA genotyping data for > 5,600 dogs of 141 breeds by combining information from two separate studies (Hayward et al. and Parker et al.) that used the current gold-standard analysis platform (high density SNP markers; > 100,000). They identified 14 behavioral traits of interest and looked for differences in the behavior of breeds that appeared to be associated with differences in the DNA, which would tell them the heritability of these specific traits.
What they found was fascinating.
In this graph, the behaviors they looked at are indicated down the y-axis, and the strength of the association between genetics and the trait, i.e., heritability, is on the x-axis. The stronger the association, the higher the heritability. The grey dogs are measurements of heritability made on dogs of the same breed. The green and yellow dogs display heritability of those same traits when the associations are made looking across breeds.
You can see here that heritabilities determined from dogs of the same breed are generally low, less than about 0.3, which means that 30% or less of the variations in behavior can be attributed to variations in genotype.
But when you compare across breeds, the average heritabilities are high, from about 0.4 (40% of variation explained) to more than 0.7 (70% of variation explained.
This is very exciting, because it's the first time we have been able to detect strong links between genes and behavior.
This is a game-changer. Our understanding of the genetic basis of behavior in dogs has gone molecular.
We now have large databases for both behavior and genotype, and these will continue to grow in size because the methodology for both is standardized (CBARQ for behavior and high-density SNP for genotype).
These allow us to do analyses like the one below, which is a "heat map" that depicts the behavioral scores by breed displayed along with the dendrogram displaying their genetic relatedness. You can easily find the sporting dogs because they are high in trainability, and the small breeds like the chihuahua, rat terrier, and miniature pinscher stand out for scoring high in traits that we might describe as reactive or "fiesty" (e.g., aggression, fear). The herding breeds score high in trainability while the hounds are low. And now we are finally able to explore the genetic basis for major breed-specific differences in behavioral traits among dog breeds.*
https://www.instituteofcaninebiology.org/blog/the-genetics-of-canine-behavior-goes-molecular
--------------------
When you look at the "heat map" you see some surprises.
Below are links to an interview with two of the papers authors,
"Heritability, in the narrow sense, means the proportion of variation in a specific trait that is explained by genetic similarity among individuals that you measured."
"…heritability is just a measure of how much genetic factors explain phenotypic variation. In cases of extremely strong selection, traits can become fixed, in which case there is no heritability (because there is no variance to explain). This is a distinction between heritability and heredity. For example, humans have two legs, which is an entirely hereditary trait, but there is no heritability to speak of because there is no variation to explain. So, if a trait has a genetic basis, and there is relaxed selection allowing for phenotypic variance, we actually have a very good shot at detecting its heritable nature under these conditions!"
https://winter2019.iaabcjournal.org/heritable-breed-behavior/
and to the original study,
https://www.biorxiv.org/content/10.1101/509315v1.full?versioned=true
If you scan thru this paper, you'll eventually get to the tendencies that group together
https://bmcgenomics.biomedcentral.com/articles/10.1186/s12864-016-2936-3
"Our PCA of breed genotypes and phenotypes indicates that some types of fear and aggression are related to each other (stranger-oriented fear and dog-/stranger-directed aggression), but are distinct from others such as owner-directed aggression. This pattern was mirrored by the results of our behavioral GWAS’s which identified two genome loci associated with the former (also shared with dog-oriented fear) and another two associated with the latter (also shared with dog rivalry). Notably, owner-directed aggression and dog rivalry are associated with the same variation in IGF1 that is known to have the greatest contribution to small-size across dog breeds (the former trait is also associated with the small-size variant at the IGF1 receptor gene). This finding is consistent with previous reports that i) there is a highly-significant correlation between the behaviors of owner-directed aggression and dog rivalry, ii) this correlation is independent of dog- and stranger-directed aggression, and iii) these behaviors are associated with breeds of small to medium size [54–56]. As owner personality does not necessarily predispose to owner-directed aggression, it is thus an apparent dog trait [57]. Some of those studies also showed a correlation between small size and stranger-oriented fear and aggression, dog-oriented fear, separation anxiety, and touch sensitivity [56]. That is supported by our finding in the confirmation GWAS’s that the same small-dog IGF1 allele is associated with the latter three traits. It is unclear whether the behavioral associations with small-size gene variants are due to developmental, physiological or psychological effects; all seem probable."
--------------
