According to a study published last week in the Proceedings of the National Academy of Sciences, dog domestication may have caused harmful genetic changes.

Domesticating dogs from gray wolves more than 15,000 years ago involved artificial selection and inbreeding, but the effects of these processes on dog genomes have been little-studied.

“Small population size during domestication and strong artificial selection for breed-defining traits has unintentionally increased the numbers of deleterious genetic variants,” said Dr Kirk Lohmueller of the University of California, Los Angeles, who is the senior author on the study.

“Our findings question the overly typological practice of breeding individuals that best fit breed standards, a Victorian legacy. This practice does not allow selection to remove potentially deleterious variation associated with genes responsible for breed-specific traits.”

Dr Lohmueller and his colleagues from Spain and the United States analyzed the complete genome sequences of 19 wolves, 25 wild dogs from 10 different countries, and 46 domesticated dogs from 34 different breeds.

“We assessed genome-wide patterns of deleterious variation in 90 whole-genome sequences from breed dogs, village dogs, and gray wolves,” the scientists said.

They found that domestication may have led to a rise in the number of harmful genetic changes in dogs, likely as a result of temporary reductions in population size known as bottlenecks.

“Population bottlenecks tied to domestication, rather than recent inbreeding, likely led to an increased frequency of deleterious genetic variations in dogs,” Dr Lohmueller said.

“Our research suggests that such variants may have piggybacked onto positively selected regions, which were also enriched in disease-related genes. Thus, the use of small populations artificially bred for desired traits, such as smaller body size or coat color, may have led to an accumulation of harmful genetic variations in dogs,” he said.

“Such variations could potentially lead to a number of different developmental disorders and other health risks.”

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Clare D. Marsden et al. 2016. Bottlenecks and selective sweeps during domestication have increased deleterious genetic variation in dogs. PNAS, vol. 113, no. 1, pp. 152-157; doi: 10.1073/pnas.1512501113