NEW YORK (NYTIMES) - 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 recognised. It sets dogs apart from their wild relatives.
Even the most socialised, 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 behavioural and genetic studies of 16 dogs and eight captive, socialised 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.
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 behaviour.
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.