Important delineations that separate the dog from its wolf ancestors are the behavioral and biological processes that make them unique. Not only are dogs more biologically suited to living in the same environment as humans, their minds have been wired through artificial selection to respond to uniquely human social cues. Thus, before we can understand how the bloodhound evolved as a unique breed with special characteristics, we must evaluate the domesticating building blocks that separated dogs from wolves and made dogs suited for such work. To do so we would have to look back even further, before the timescale of dog domestication, to not tens of thousands, but millions of years at the ancestors of both wolves and dogs in order to explain the great genetic diversity seen in dogs today. How is it that more than 400 distinct breeds, each with unique phenotypic traits and abilities have developed from the singular wolf species? A possible answer lies in the canid genetic material that predates the evolution of the wolf species (Bradshaw). Although it is difficult to separate what traits are uniquely due to mutations and subsequent artificial selection and the possible genetic features that belong to pre-wolf canids , it is clear that dogs and wolves have become clearly distinct entities. The huge variability in social behavior, size, appearance, and instinct in dogs cannot be easily explained. Whether these traits can be traced back to the genetic versatility of a greater Canid ancestor that led to the wildly different social behavior and appearance of Canids such as the coyote, fox, and jackal, or because artificial selection has relaxed the pressures on deleterious traits and mutations, dogs have developed highly specialized traits and behaviors. Such is the case with the bloodhound.
"Since no conscious human choice was made to identify dogs with duplicated amylase genes and select them for breeding (since the characteristic would not be readily observable) this is an example of environmental, or natural selection" -Venema
"but instead of having just one gene, all modern dogs have between 2 and 15 copies of this gene, whereas all wolves have only one. The dog copies sit side-by-side in the dog genome, right next to where the original amylase gene is found in wolves, indicating that the gene copies were duplicated during chromosome replication" -Venema
The abilities of the bloodhound to track have to be traced back to a greater ability to communicate with humans. Domesticated dogs are able to recognize human direction, going so far as to follow the gaze or finger of a directing human, something even chimps and other close relatives of humans cannot do. In order to understand the bloodhound’s ability to track specific targets and its use in human culture, we must first understand the biological implications of dog and human interactions as a whole. Studies have shown highly localized development in the genes governing the prefrontal cortex of dogs that govern complex social behavior, even when compared to wolves. Thus, it is important to recognize what behavioral processes are owed to a greater Canid ancestry and those that are due to rapid coevolution with the human race. Another key biological process that helps to explain the evolution of the dog is its adapted ability to consume complex starches. Whereas wolves are able to digest some starches in nature, dogs possess genes that allow them to produce many times the enzymes necessary to digest and benefit from starches. This seems to coincide with the narrative of the agricultural revolution and as humans moved away from hunting and gathering to a more sedentary lifestyle, so too did our canine companions. But genetic evidence suggests that the interactions that sparked domestication occurred before evidence of the agricultural revolution, an inconsistency in the narrative of how agriculture helped to distinguish the dog from the wolf. Such an example then is important to distinguish between the causes and the results of domestication. Dogs did not diverge from wolves because they started to eat a starch rich diet but dogs developed (were selected for) the ability to digest starch because they were domesticated and living in close proximity with humans. This can then be applied to behavior as well. It is important to distinguish between the affects of natural selection and human agency in the story of domestication and these biological processes help explain how domestication led to the traits we see in dogs today.
Further ReadingsTo look at the specific breeding practices of the bloodhound and their use go to:
To look at the specific processes and methodology for bloodhounds to track people, look at:
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The genomic signature of dog domestication reveals adaptation to a starch-rich diet
(technical paper on scientific research behind starch diets in dogs) Genetics of Dog Breeding (accessible overview of domestication and selection) Evolution Basics: New Genes, A New Diet, and Implications for Dog Origins (A blog worth exploring, details on the processes behind the genetic evolutions of the dog, distinguishes between natural and artificial selection, overall emphasizes the role of evolution in domestication) |