Why Are Dogs So Friendly? The Answer According to Science

Why Are Dogs So Friendly? The Answer According to Science

February 09, 2018

Tail-wagging, face-licking, jump-in-your-lap friendliness is what dog lovers adore and cat people scorn. But like it or not, the incredible sociability of many — although not all — dogs is universally recognized. It sets dogs apart from their wild relatives.

Even the most socialized, friendly wolf is cold company compared with a Labrador retriever in full face-licking mode.

But what produces this social exuberance? A team of researchers reported on Wednesday in the journal Science Advances that the friendliness of dogs may share a genetic basis with a human disease called Williams-Beuren syndrome.

Humans with this developmental delay, caused by mutations in a region of genes, show a variety of symptoms that include intense and indiscriminate sociability.

A group of scientists from Princeton, Oregon State University and other institutions combined behavioral and genetic studies of 16 dogs and eight captive, socialized wolves to pin down changes in two genes on a region of one chromosome that were associated with hyperfriendliness in dogs. The two genes, GTF2I and GTF2IRD1, are also associated with Williams-Beuren syndrome in humans, said Bridgett M. vonHoldt, an evolutionary biologist at Princeton University and an author of the study.


Dr. vonHoldt and her colleagues studied a stretch of DNA in dogs that includes about 29 genes. The deletion of part or all of this section seems to cause the human syndrome. They sought out structural changes in the genes, like deletions or transposition of DNA to another location.

The study is a first step in what has proved a difficult area of genetic research: finding the roots of complex behavior. “We struggle a lot with wanting to know genes that are linked to behavior,” Dr. vonHoldt said.

The new results, she added, are a hopeful sign for this area of research.

Adam Boyko, a biologist who studies dog genetics at the Cornell University College of Veterinary Medicine, called the work “truly interesting and important” and said it “may be one of the first studies to ever identify the specific genetic variants that were important for turning wolves into dogs.”

But, he said, it looks at a small number of animals, and although the genes it identifies are good candidates for producing hypersociability, more research on a larger and more diverse group of animals would be needed to confirm the results.

The research was born out of a conversation Dr. vonHoldt had with Monique Udell, an experimental psychologist at Oregon State University who studies the behavior of wolves and dogs. Dr. Udell was interested in behavioral parallels between dogs and people with Williams-Beuren syndrome.

Research in animals on behaviors that are similar to human disorders is common. Scientists have created strains of mice that show behaviors similar to human depression or autism. Similarly, one of the genes found in this study of dogs is related to hypersociability in mice. The assumption behind the research is that humans share so many genes with other animals that understanding a disease in animals may help treat it in humans. The current research is a bit different in that understanding the roots of a disorder in humans may help illuminate the evolution of new behaviors in animals.

People with Williams-Beuren syndrome face many health issues, but Dr. Udell was intrigued by several characteristic behaviors: excessively friendly behavior, sometimes treating strangers as friends, and even a lack of persistence on cognitive tests, which she has observed in experiments with dogs, compared with wolves.

She said the human disorder involves a developmental delay, and dog development is delayed compared with that of wolves: “The very things that make life challenging for a human may make dogs successful.”


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