Dogs that look more like puppies have an evolutionary advantage

Illustration for article titled Dogs that look more like puppies have an evolutionary advantage

In many ways, dogs appear and behave more like wolf puppies than wolf adults. Scientists have theorized that these "paedomorphic" features are the byproduct of selecting dogs against aggression. But a new study suggests this is no byproduct at all, but rather the result of a human preference for puppy-like facial expressions.


How wolves were first domesticated is still somewhat of a mystery. It's likely they self-domesticated themselves by adjusting to humans and taking advantage of scavenging possibilities. As for their juvenile characteristics, such as floppy and large ears, curly tails, big eyes, rounded forehead, and shortened snout, those came later — likely the result of selecting dogs that were less aggressive; puppy-like physical traits were a side-effect of this preference.

The Inner Brow Raiser

Perhaps. But a new study by Bridget Waller and colleagues now suggests we have been steadily reshaping the faces of dogs owing to our preference for juvenile expressions.

Illustration for article titled Dogs that look more like puppies have an evolutionary advantage

Specifically, we seem to like dogs that exhibit a particular muscular contraction — the inner brow raiser which lifts the medial portion of the brow. This increases the apparent size of a dog's eyes in relation to the face, thus enhancing a feature associated with human infants (i.e. we find big eyes really, really cute). Another theory is that the same contraction in humans indicates sadness, which can be a sign of vulnerability. It also exposes white sclera, which contributes to gaze following abilities; we are more likely to cooperate or behave altruistically when being watched.

Regardless of the reason, we seem to really like this particular feature in dogs.

A Powerful Selective Force in Domestication

The researchers came to this conclusion by running an interesting experiment at a dog re-homing shelter. While tracking each dogs' inner brow movements, the researchers took note of how quickly the dogs were chosen by adoptive owners. Their results showed that juvenile-looking dogs were in fact more preferred.


"This finding further supports the growing evidence that indirect manipulation of human sensory preferences (particularly a preference for juvenile facial characteristics) has been a particularly powerful selective force in domestication, even more so than genuine indicators of temperament," conclude the authors in their study.

What's more, this preference may have also been at work during the early stages of dog domestication.


It's worth noting that tail wagging and close proximity to humans were not strongly associated with the speed of selection by adopters.


Finally, and in the words of the researchers, "it is highly possible that these facial expressions do not correlate with suitability as a pet, but, like superficial morphological traits, are still preferred over more relevant behavioural traits."

Read the entire study at PLoS One: "Paedomorphic Facial Expressions Give Dogs a Selective Advantage."


Top Image: Fotyma/Shutterstock. Inset image Waller et. al. / PloS One.



This study might be some of the biggest hogwash I've heard.

The dog has been manipulated by mainly selective aesetic breeding for the past 300 years. Many dogs recently, not per say in the whole of domestication have been bread smaller and for puppy like physical characteristics. Even go back 100 years and look a pictures of the bulldog then and today- and you can see that this breed has been manipulated so to show certain physical characteristics. The Cavelier King Charles spaniel - almost totally looks like a juvenile dog because when it was introduced it was done because of the growing fad for lap dogs.

Working and hunting dogs were not bread for cuteness, but for strength, durability, and intelligence. It is only since the advent of the lap dog that we have begun to choose these "cute" characteristics.

Domestic dogs who produced a high frequency of facial movement to raise the inner brow (AU101) were adopted more quickly from re-homing shelters. As AU101 enhances a key feature of paedomorphism (eye size and height: [10]) this suggests that dogs have evolved to manipulate the human preference for paedomorphic features using the face

This paper is also lacking in the social and cultural views of people today. Selection in a pet can be influenced in what is currently desirable by what is popular. If dogs that are "puppy" like are what people are interested in or socially desirable they can influence the look of the dog. The breeding industry is rife with over breeding for certain characteristics, especially ones that are in demand.

Differences in dogs - the pictures alone are good. Dog differences -today and yesterday