Puppy dog eyes

We've sequenced the genome of Bruce the black lab puppy, but we couldn't find a gene for cuteness. Which he has in spades. Well, there might not be a cuteness gene, but zoology correspondent Lucy Cole has the story of the next-best thing.

Lucy - Have you ever thought that your dog is able to make the most adorable puppy dog eyes at exactly the right moment? Well, British and American researchers have found that dogs have in fact evolved a particular muscle in their face to allow them to do just this. It’s just above the eyebrow and it’s called the levator anguli oculi medialis. It allows dogs to lift the inner corners of their eyebrows to create those unmistakable puppy dog eyes.

In this study, the researchers dissected both dogs and wolves to compare them. It turns out that wolves don’t have this extra muscle, so it seems that dogs have developed it since being domesticated around 33,000 years ago. In fact, the team found that the Siberian husky, an ancient breed of dog more closely related to the wolf, is the only species which doesn’t have it. This means that it has taken just a few tens of thousands of years for this to evolve which, in evolutionary terms, is really quick!

We don’t yet know what genes are behind the levator anguli oculi medialis, but muscles are complex structures, and evolving a new one would probably need some big genetic changes. Why would this have happened? That’s what the next part of the study was investigating. The researchers tested how live dogs and wolves reacted when a stranger approached them. Dogs raised their eyebrows more commonly than wolves, and in a far more exaggerated way.

The theory is that using this muscle to raise their eyebrows actually helps dogs form social connections with us, and makes us want to care for them. Raising their eyebrows makes their eyes bigger and more like human children’s eyes, which elicits a caring response in us. Perhaps 33,000 years ago our ancestors were more likely to bring a dog in from the cold and protect it, if it could lift its eyebrows to look more like a human baby.

In fact, in a previous study, the same researchers found that dogs who raise their eyebrows get adopted from re-homing centres more quickly. So if being adopted gives a dog’s genes a better chance of survival, it seems that even today, dogs with more puppy-like features could have a selective advantage.

So next time you find yourself looking into those puppy dog eyes and forgiving your dog for misbehaving, just remember that it’s entirely our fault.