The bond between humans and dogs is unique, closer than between any other species. This bond is a result of dog breeding, which started to form more than 100 000 years ago with the first domesticated wolf.
Dog Breeding and Evolution
Adjusting to the life within human societies, first dogs started to adapt by their body size, coat color and diet. The biggest role in shaping today’s dog breeds has played human selection itself, the dog breeding, which was based on wanted dog’s temperament and specific skills which dog had shown, such as hunting, shepherding, guarding, work and company. As a result of human artificial selection, the dog is today the most phenotypically diverse mammal species known.
Although it gave us a great number of different dog breeds, each with unique traits, human selection caused severe bottleneck within domesticated dog population, causing a high frequency of inherited disorders among dogs. Most of these inherited disorders are autosomal recessive, meaning two copies of disorder-causing genes are needed for the dog to be affected. When dog possesses one copy of the causative gene, he will not develop symptoms of the disorder, meaning the mutation can be passed on for many generations without being observed. As the domestication of the dog caused the bottleneck, specific disease-causing variants became more frequent and not only inbreeding is the cause of inherited disorders among dogs anymore.
DNA tests developed in order to detect the presence of disease-causing genes became a powerful tool in maintaining healthy dog population and successful breeding program. As many diseases develop later in life, after dog’s sexual maturation, as well as high frequency of dogs possessing one copy of causative genes without developing disease’s symptoms, breeding based on phenotypical selection is not sufficient in obtaining healthy cubs. DNA tests enable molecular selection and are the only method to ensure wanted traits among puppies without unpleasant surprises.
The following video explains the connection between dog evolution and the wide range of dog breeds we know today, as well as growing number of genetic disorders among them.
Marsden CD, Ortega-Del Vecchyo D, O’Brien DP, et al. Bottlenecks and selective sweeps during domestication have increased deleterious genetic variation in dogs. Proceedings of the National Academy of Sciences of the United States of America. 2016;113(1):152-157. doi:10.1073/pnas.1512501113.