Common genetic trait links human and doggy friendliness

We may be more like our dogs than we know.

Scientists studying the genetic basis for dog friendliness have found it comes from a portion of their genome that is similar to the area in the human genome that relates to sociability.

In a study published in Science Advances, researchers from Princeton University and Oregon State University looked into what gene seems to give our furry friends their doggy sociability, which sees them turnto humans for attention, instruction, play and food.

"There's a lot known about the dog genome, but there's not a lot known about the genes that regulate dog behaviour," says Monique Udell, an animal behaviourist and professor at Oregon State University in Corvallis, Ore.

"What this finding does is it illustrates that there are some genes that really directly correspond with behaviours in dogs that have been of interest to scientists for a long time that contribute to domestication and actually lead to their success."

In fact, these common genetic traits may help explain why dogs and humans took up together some 14,000 years ago.

Relating dogs to human genome

The researchers focused on chromosome 6 in both dogs and humans.

In humans, we know the role of this part of the genome from the study of Williams-Beuren syndrome, a genetic disorder that results in hypersociability, such as extreme friendliness and a lack of fear of strangers.

"It was the remarkable similarity between the behavioural presentation of Williams-Beuren syndrome and the friendliness of domesticated dogs that suggested to us that there may be similarities in the genetic architecture of the two phenotypes," said Bridgett vonHoldt, an assistant professor in ecology and evolutionary biology at Princeton and the study's lead co-author.

Princeton's Emily Shuldiner, the study's other lead co-author, first pinpointedthe commonalities in the genetic architecture of Williams-Beuren syndrome and canine tameness back in 2010.

This new study zeroes in further on two gene variations that seem to contribute to sociability in dogs, compared to grey wolves, who would have had a similar canid ancestor.

"Genes can have various variations to them. They can have insertions or deletions and because of that it can change the way a particular gene functions," Udell explained.

"What's unique is we do see that a lot of those genetic regions are altered in dogs and in many cases they're not altered in wolves. It's the alterations, the changes or mutations, that seem to be occurring on those genes that seem to be affecting the hypersocial behaviour."

Individuals with Williams-Beuren syndrome have structural variations on the same part of the genome, showing its importance in regulating social behaviour in humans.

"Sociability is a complex trait, so it's not just a product of one gene. But what we do know is that individuals with Williams-Beuren syndrome, they tend to have deletions in that area," Udell said.

They also developmore slowly in terms of meeting milestones than other children, similar to dogs compared with wolves.

Comparing dog and wolf behaviours

The researchers compared dog DNA to the DNA of grey wolves to isolate the genetic differences, but also tested both dogs and wolves for friendliness, using wolves from the Indiana Wolf Park who have been raised by humans from the age of two weeks.

Udellgave both dogs and wolves the task of getting into a lidded cardboard box that contained a sausage, either in the presence of a human or alone.

Dogs ... tend to be excited at first, they look like they're going to be interested and then they quickly give up. In many cases they don't even try to get it open.- MoniqueUdell,animal behaviourist

When a human was present, domestic dogs spent a significantly greater proportion of the two minutes they were given to complete the task gazing at the human. Wolves were more likely to pay attention to the box and nine out of 10 figured out how to raise the lid, compared to just two of the 18 dogs.

"What we see is that wolves, when we put down this container, they immediately go to the task. They try to break into the container and most are successful," Udell said.

"Dogs ... tend to be excited at first, they look like they're going to be interested and then they quickly give up. In many cases they don't even try to get it open."

The most successful dog in the study was a tiny dachshund, who always got the lid open.

Wolves and dogs were also tested on their sociability, and researchers discovered that the dogs spendmore time than wolves seeking attention, even from unfamiliar humans who did not make eye contact or call out to them.

"Both dogs and wolves are interested in people.They'll run up, greet them and they'll check them out. Wolves spend about as much time as they would greeting another dog and then go back to whatever business was happening in the environment," Udell said.

"Dogs greet, then they greet and they greet for the entire two minutes and they never leave."

Why dogs became our best friends

In puzzling out how dogs and our human ancesters first got together, it was thought that humans were attracted to dogs in part because of their ability to discern gesture and voice.

Now Shuldiner and vonHoldt are advancing a new theory for how dogs came to be man's best friend.

It may be that our human ancestors just chose the friendliest animals as their companions.

"It's a real combination of humans choosing the friendlier dogs and the friendlier dogs choosing humans," Udell said.

• How smart is your dog?
• Genetic analysis reveals origins of dog breeds