The DNA History of Dogs
In researching the DNA history of dogs it should be noted that any study of a specific ‘pure breed’ or pedigree is complicated by the fact that its historic lineage is characterised by periods of crossbred admixture followed by strict, closed-book breeding.
Expansion of genetic diversity occurs when heritable sequences of DNA, (genes), are mixed across breeds. For most of their long history it has been left to dogs themselves to do this mixing. A dog’s genome is its complete set of DNA including all of its genes. Results from many studies of canine genomes across various breeds show a large number of shared genomic regions associated with the collection of traits that make up a ‘dog’ – any dog, (Serpell J. 2017). The widely varying and complex morphologies seen in dogs, (their size, propoprtions etc.) however, are caused by a comparatively small number of their genes.
Parker DNA Comparison Report 2017
Research published in 2017, the largest genetic analysis at the time, compared DNA samples from 161 breeds from around the world, (representing a little under half of all dog breeds). The study was able to divide dogs into 23 genetically defined clades. These genetic clades coincide with particular dog traits: dogs built for strength fell into one clade, herders into another and so on. It was possible to create a DNA based bootstrapped cladogram showing canine common ancestries, (Parker H. G. et al. 2017).
The 2017 DNA comparison study confirms a two step process in the development of modern breeds. Early breeders bred for specific purposes. Then, in the nineteenth century those larger groups were divided into our modern breeds.
One remarkable result from his study of the DNA history of dogs finds the DNA of a pug appearing in many of the small and toy European breeds. Parker suggests that this was the result of a pug-type dog arriving in Europe from China in the 1500s.
The cladogram shows some breeds with ancient lineages and, so far (the study is ongoing), little or no DNA mixing. Examples are some of the Nordic breeds: Elkhound, Samoyed and Finnish Spitz. The Basenji and Tibetan Terrier are also shown by the study to be quite strongly ancient or ‘pure bred’.
Parker H. G. et al. [25 April] 2017, Science, Elizabeth Pennisi, Where did your dog come from? New tree of breeds may hold the answer (link checked Mar 2019)
Serpell J. 2017, The Domestic Dog, vonHoldt B. M. & Driscoll C. A., 3.8
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