Study: Dogs evolved ‘sad puppy eyes’ to appeal to humans

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(AP) – A dog’s sad “puppy dog” eyes are hard to resist, and people may be partly to blame for them, a new study suggests.

Pooches can make these babylike eyes because they have a muscle to raise their eyebrows. But that muscle is virtually absent in their ancestors, the wolves. So what happened?

The new study suggests that over thousands of years of dog domestication, people preferred dogs that could pull off that appealing look. And that encouraged the evolution of the facial muscle behind it.

Unlike wolves, dogs rely on human eye contact, whether to know when someone’s talking to them or when they can’t solve a problem.

Burrows and her colleagues compared dogs and wolves by surgically peeling back fur on dog and wolf cadavers to look at their eye muscles.

They found dogs have a meaty eye muscle to lift their eyebrows and create sad “puppy dog” eyes. But in wolves, the same muscle was stringy or missing.

The scientists saw the difference that makes when they recorded dogs and wolves staring at a person.

Pet pooches frequently and intensely pulled back their eyebrows to make their sad faces, whereas wolves rarely made these faces, and never with great intensity.

The researchers believe dogs, over their relatively short 33,000 years of domestication, evolved to use this eye muscle as a way to communicate with humans, possibly goading people to fee or care for them — or at least take them out play.

Dog experts not involved with the study were impressed.

Wynne said the study is clever, but it has a few snags.

Although there are more than 300 dog breeds, the study looked at only five of these varieties for dissections and video recorded mainly one, the Staffordshire bull terrier.

The case was similar for wolves, of which scientists recognize more than two dozen closely related types. The researchers examined only two.

But Wynne was particularly concerned by the lack of background information for each animal. It’s unclear, for example, if the observed wolves were raised by humans or used to people approaching them, details that could muddy the study’s findings. And most of the observed dogs came from animal shelters, which could also bias the results.

Burrows said she has already planned follow-up studies to address these shortcomings.

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(This story was originally published on June 17, 2019)

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