I do not have a dog in the fight about dogs. My dad said that there was a dog in every boy’s life, and so we had some dogs when I was young, and then in my own life, no dogs. I was living a town life, and working, and had neither need nor wish for them. I have nothing against dogs, other than that they should live in the country, not the town, and preferably do something useful. In towns they are captive and, when badly trained, frequently a nuisance. In the country, so long as they are not worrying sheep, they are more agreeable company.
I can see that dogs have very probably evolved with us, in a symbiotic relationship. They know how to flatter us, in return for food and companionship. Parasitism it may be, but it works for many people, and virtually all dogs. Dogs and their owners are reciprocally besotted.
Frankly, I doubted owner’s stories about the intelligence of their pooches. We are creatures of habit, and dogs learn from observation how we are to be handled. So, it was with some initial hesitation that I looked at the research on canine intelligence, and then came to see that, after due allowance for restrictions on which tests which could be used, there was a case for comparing the intelligence of dogs and of dog breeds. The fact that the clever breed were sheep dogs pleased me. We all have to earn our keep.
Here is Rosalind Arden on the intelligence of dogs:
The other thing about dogs, is that they live shorter lives, so their generation pass more quickly, and can be observed as they evolve. Even more important, they can be bred through a selective process into different sorts, for different purposes. Assisted evolution in action. Hence, we can look at these close companions and make judgments about how characteristics and behaviours alter through evolution. We can even tamper so as to breed up dogs for our uses. Guide dogs, for example. Practically, dogs that can detect when we are about to have a fit. Perhaps even dogs that can detect our diseases before any other detection device can do so.
What can we find out from genetic analyses of dog behaviour and dog breeds?
Highly Heritable and Functionally Relevant Breed Differences in Dog Behavior
Authors: Evan L MacLean, Noah Snyder-Mackler, Bridgett M. von Holdt & James A.
Below I show the abstract verbatim, and have selected and abbridged the main points of the paper.
Abstract: Variation across dog breeds presents a unique opportunity for investigating the evolution and biological basis of complex behavioral traits. We integrated behavioral data from more than 17,000 dogs from 101 breeds with breed-averaged genotypic data (N = 5,697 dogs) from over 100,000 loci in the dog genome. Across 14 traits, we found that breed differences in behavior are highly heritable, and that clustering of breeds based on behavior accurately recapitulates genetic relationships. We identify 131 single nucleotide polymorphisms associated with breed differences in behavior, which are found in genes that are highly expressed in the brain and enriched for neurobiological functions and developmental processes. Our results provide insight into the heritability and genetic architecture of complex behavioral traits, and suggest that dogs provide a powerful model for these questions.
Studying aggression, fear, trainability, attachment, and predatory chasing behaviors on 14,020 individual dogs with breed-level genetic identity-by-state estimates from two independent studies we found that a large proportion of variance in dog behavior is attributable to genetic factors. The mean heritability was 0.51 ± 0.12 (SD) across all 14 traits (range: h 2 0.27-0.77), and significantly higher than the null expectation in all cases (permutation tests, p < 0.001).
Interestingly, the traits with the highest heritability were trainability (h 2= 0.73), stranger-directed aggression (h 2 = 0.68), chasing (h 2 = 0.62) and attachment and attention seeking (h 2 = 0.56), which is consistent with the hypothesis that these behaviors have been important targets of selection during the cultivation of modern breeds.
Overall, we identified 131 unique SNPs that were significantly associated with at least one of the 14 behavioral traits (Bonferroni p ≤ 0.05, Fig 2). Forty percent of these SNPs (n= 52) were located within a gene – none of which encoded for changes in the amino acid sequence of the protein. On average, the top SNP explained 15% of variance in the behavioral trait. Thus, while we identify multiple variants with moderately large effects, the variance explained by individual SNPs is far less than that explained by additive variation across the genome (heritability), suggesting that as in humans, behavioral traits in dogs are highly polygenic. However, the variance explained by the top SNPs in our analysis across breeds was, on average, more than 5 times higher than that from within-breed association studies.
Many of the gene-level associations with dog behavioral traits include (i) candidate domestication genes, (ii) genes mapped to phenotypes implicated in domestication, (iii) genes implicated in behavioral differences between foxes bred for tameness or aggression, and (iv) genes that underwent positive selection in both human evolution and dog domestication. For example, PDE7B, which is differentially expressed in the brains of tame and aggressive foxes has been identified as a target of selection during domestication, and is highly expressed in the brain where it functions in dopaminergic pathways. In our analyses, SNPs in this gene were associated with breed differences in aggression, which is consistent with data from experimentally bred foxes, as well as hypotheses that selection against aggression was the primary evolutionary pressure during initial domestication events.
The gene-trait associations identified in our study also align closely with similar associations in human populations. For example, breed differences in aggression are associated with multiple genes that have been linked to aggressive behavior in humans. Molecular associations with breed differences in energy include genes previously linked to resting heart rate, daytime rest, and sleep duration in humans. Lastly, breed differences in fear were associated with genes linked with temperament and startle response in humans, and several of the genes implicated in breed differences in trainability have been previously associated with intelligence and information processing speed in humans.
If the variants in genes identified in our analyses make major contributions to behaviour and cognition, then the associated genes should be (i) involved in biological processes related to nervous system development and function, and (ii) primarily expressed in the brain. Indeed, we found that behavior-associated genes (as identified through meta-analysis) were enriched for numerous nervous system processes. These processes include neurogenesis, neuron migration and differentiation, axon and dendrite development, and regulation of neurotransmitter transport and release.
Breed differences in behavior covary strongly with relatedness between breeds, and for several traits, genotype accounts for more than 50% of behavioral variation across breeds – up to 25x higher than heritability estimates from genetic studies within breeds. Individual SNPs that are associated with behaviors tend to fall in genes that are disproportionately expressed in the brain, and are involved in pathways related to the development and expression of behavior and cognition. In addition, the variants associated with breed differences in behavior are found in genes with sequence or brain-expression differences in foxes artificially bred for tameness or aggression, and are implicated in human behavioral genetics, suggesting that these genes may play important roles in modulating behaviour across species.
You might like to compare these assessments with numbers of humans killed by dogs in the US. As you can see, the rates differ considerably. There are a longer list of breeds at the bottom of the table I have not included for brevity because they all killed one person, but the top killers are shown here.
We are different from dogs, but it appears that some genes in dogs and some genes in humans have the same functions, and affect the brain in the same way. We are closer to our hounds than we imagined. One could say that there is a Great Chain of Being, though this one brings us closer to animals than angels.
Of course, dogs are dogs and not humans. There have been population bottlenecks which simplify their genetic architecture. Dogs do not have a culture in the normal sense of that word, so cannot transfer libraries of knowledge nor be influenced by editorials in the New York Times. However, it is thought-provoking that dog breeds differ in their behaviours in ways that can be traced to their genetics, and as in the case of homo sapiens, those genes express themselves in brain. Some dogs breeds bite us more than others for non-cultural reasons.
The implications are clear: in a species which we can to some extent control, and which partly controls some of us, we see a similar genetic pattern, and a genes based difference in behaviour between breeds.