7.2. “It Is Not The Breed Of Dog, But How It is Raised”
The table that follows is from Page 31 of van den Berg’s paper and shows the heritability estimations of canine aggression-related traits in three studies. The estimates of the influence of genes on the aggression traits are between 6% and 33%, and conversely, the environmental aspects, i.e., how the dogs are raised, are between 94% and 67%.
The results indicate that it is estimated that aggression-related traits are only slightly affected by genes and mostly affected by environment, i.e., how a dog is raised and socialized. This supports the consistent contentions of responsible owners of so-called “Pit Bulls” that how the dog is raised and not the breed is the dominant factor in dog aggression.
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van den Berg attempted to find a genetic basis for aggressive behaviour in Golden Retrievers. On Page 9 of “Genetics of aggressive behaviour in Golden Retriever dogs” by van den Berg it is stated,
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“Golden Retrievers were the most frequently encountered purebred dogs in a group of Dutch dogs diagnosed with fear-motivated aggression Galac and Knol 1997). Although this may in part reflect the high number of Golden Retrievers in the Netherlands (Schellart and den Hertog 1998), it is surprising to encounter many aggressive individuals in a breed that has been selected for friendliness. (Tudor 1980; http://www. goldenretrieverclub.nl/; link accessed August 2005).
On Page 10 of van den Berg’s document, it is stated,
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“We studied the serotonin receptor genes 1A, 1B, and 2A (htr1A, htrl1B, htr2A) and the serotonin transporter gene (slc6A4). In section 3.4, we described the analysis of these genes in related Golden Retrievers. We conclude that the candidate genes are not likely to play a major role in the variations in aggression in the Golden Retrievers.”
On Page 181 of “Genetics of aggressive behaviour in Golden Retriever dogs” by van den Berg it is stated,
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“The aim of the work described in this thesis was to identify genetic variations underlying the variation in aggressive behaviour in Golden Retriever dogs.”
and
“We started our studies of aggression in Golden Retrievers because early observations suggested a strong genetic basis for the behaviour. In other words, we expected that a large part of the phenotypic variation was caused by genetic variation. In retrospect, the evidence for a strong genetic basis was rather weak.”
On Page 183, it is stated,
“Nevertheless, our results suggest that owner-derived information was more suited for phenotyping than our behavioural test. In section 2.2 we concluded that the canine behavioural assessment and research questionnaire (CBARQ) is a promising tool for genetic studies because it is reliable and valid: and behavioural scores derived from it displayed sufficient variation in Golden Retriever families.”
In other words, the people who live with the dogs are the best source of information about how the animals are going to behave.
On Page 184 of “Genetics of aggressive behaviour in Golden Retriever dogs” by van den Berg it is stated,
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“In spite of the progress that we made with phenotyping, one major question remains unanswered: do the aggressive Golden Retrievers have a genetically based lowered threshold for aggressive behaviour in general or for a specific subclass of aggression? Our results are inconclusive with respect to this topic.”
and
“We would expect this correlation to be higher if there is a major aggression gene influencing both traits.”
On Page 185 and 186, it is stated,
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“The results in section 2.3 suggest that a large part of the variation in aggression in our Golden Retriever families can be attributed to genetic variation. However, environmental factors undoubtedly influence the trait as well. Such environmental factors may include prenatal circumstances such as stress in the pregnant bitch (Serpell and Jagoe 1995) and early experiences such as maternal care (Scott and Fuller 1965; Serpell and Jagoe 1995), living conditions at the home of the breeder (Appleby et al. 2002), illness as a puppy (Podberscek and Serpell 1997b; Serpell and Jagoe 1995), and socialization (Appleby et al. 2002; Houpt and Willis 2001; Scott and Fuller 1965). Scott and Fuller (1965) demonstrated that the experience of the puppies during the sensitive period (i.e., approximately 3-12 weeks of age) determine which animals and human beings will become their closest social relatives…Another potential environmental influence is the diet of the dog. The protein content of the diet and the amount of amino acid tryptophan in the diet may influence the behaviour of a dog (DeNapoli et al. 2000; Dodman et al. 1996c; Houpt and Zicker 2003). Aggression can also be caused by pain and some diseases have specifically been reported to be associated with aggressive behaviour, e.g., epilepsy and hypothyroidism (see Reisner 1991 for a review).”
On Page 187 of “Genetics of aggressive behaviour in Golden Retriever dogs” by van den Berg it is stated,
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“Behavioural genetic researchers generally agree that behaviour is produced by intricate neural networks that are developed and maintained under influence of a variety of genes and environmental factors (Hamer 2002; Robinson 2004).”
At http://www.cgejournal.org/content/1/1/7, an article entitled Holding back the genes: limitations of research into canine behavioural genetics by Diane van Rooy, Elizabeth R Arnott, Jonathan B Early, Paul McGreevy and Claire M Wade published on June 10, 2014 in Canine Genetics and Epidemiology it is stated,
“Canine behaviours that are both desirable and undesirable to owners have a demonstrable genetic component. Some behaviours are breed-specific, such as the livestock guarding by maremmas and flank sucking seen in Dobermanns. While the identification of genes responsible for common canine diseases is rapidly advancing, those genes underlying behaviours remain elusive.”
and
“Identification of genes responsible for canine monogenic diseases (caused by one gene) is advancing rapidly, but the genes underlying behaviours remain elusive. This is because canine behaviours are similar to complex diseases such as Hypothyroidism, where there are both environmental and multiple genetic components.”
and
“In the 19th century, extensive record keeping began to trace the lineages of dogs bred for purpose. The domesticated dog became refined into breeds with closed studbooks and written breed standards. As leisure time and wealth increased, the objectives of selection altered from being purpose-driven to fashion-driven. Although some working breeds are still in demand, and some utilise their original working traits in contemporary canine sporting activities such as agility trials, numerous breeds have been selected for purposes unrelated to practical work. In the role of companions, modern dogs may require higher tolerance than their ancestors for the frustration of inactivity, social isolation and unstimulating environments [4]. In this sense, the companion dog may be regarded as an evolutionary work in progress [5], proving highly adaptable and malleable to human needs, but the niche into which dogs must evolve continues to shift.”
and
“Early experiences in the lives of dogs can affect their development and future behaviour. For example, dogs who experienced an illness in the early part of their life were significantly more likely to exhibit owner-defined behavioural problems later in life [17]. These behavioural problems included aggression and fear towards strangers, separation-related barking and inappropriate sexual behaviour. Deprivation of essential nutrients in early life may also have long-lasting effects. For example, a diet deficient in the polyunsaturated fatty acids that are necessary for early brain development may affect associative learning and cognition [18]. Finally, behaviours of offspring may be influenced by epigenetic mechanisms. Maternal behaviours alter the methylation of DNA in the offspring, thereby affecting gene expression in future generations [19].”
and
“This overt variation in behaviour between breeds has been observed in many subsequent studies. When more than 13,000 dogs belonging to 31 breeds were subjected to the Swedish Dog Mentality Assessment, the aggression scores varied significantly between breeds, although there was also high variance within breeds [60]. Aggression subscores also showed significant differences between 33 breeds when C-BARQ was utilised for phenotyping [33]. A higher proportion of dachshunds, Chihuahuas and Jack Russell terriers showed serious aggression to humans, whereas serious aggression towards unfamiliar dogs was reported in more than 20% of the Akitas, Jack Russell terriers and those dogs classified as pit bull terriers.”
On Page 12 of “Behaviour Genetics in the Domestic Dog” by Mia Persson at https://www.ifm.liu.se/biology/zoology/avian/phd-literature-essays/Introuppsats-Mia-Persson.pdf, it is stated,
“There are several different ways in which the genetic contribution to a behavioural trait can be estimated. Heritability, as mentioned earlier, is a parameter estimating how much of the difference measured in a trait that can be accounted genes or environment (Visscher et al., 2008; Wilson et al., 2011). However, this parameter does not tell us anything about the number or the type of genes or environmental factors involved.”
