An innate ability to “go fetch” without any training may be the reason dogs became man’s best friend, scientists have discovered.
Experts have long assumed that canines’ tendency to pursue an object and bring it back to their master arose as a result of domestication by humans over the last 10,000 to 15,000 years.
But a series of new experiments with wolves - dogs’ evolutionary ancestors - reveals the trait is in-built.
Researchers at Stockholm University threw tennis balls to eight-week-old wolf puppies they had only just met, giving them vocal encouragement to go fetch.
To the scientists' surprise, some of the animals complied.
They say it suggests that rather than being trained and bred into the species as they evolved from wolves to modern-day domestic dogs, the ability was already there and may be why wolves were chosen as companions to humans.
"When I saw the first wolf puppy retrieving the ball I literally got goose bumps," says Christina Hansen Wheat, who led the research.
"It was so unexpected, and I immediately knew that this meant that if variation in human-directed play behavior exists in wolves, this behavior could have been a potential target for early selective pressures exerted during dog domestication."
Ms Hansen Wheat and her team raised wolf and dog puppies from the age of 10 days and put them through various behavioral tests.
In one of those tests, a person the puppy did not know threw a tennis ball across a room and, without the benefit of any prior experience or training, encouraged the puppy to get it and bring it back.
Wolves from the first two litters that were tested did not go for the ball.
However, those from a third litter did go for the ball, responding to social cues given by the human. "I did not expect that - I do not think any of us did," said the zoologist.
"It was especially surprising that the wolves retrieved the ball for a person they had never met before."
She added: “Wolf puppies showing human-directed behavior could have had a selective advantage in early stages of dog domestication."