Genetic reason we think dog puppies are irresistible

(ORDO NEWS) — With just the power of one pleading look with big eyes, dogs can hug us with their perfect little paws. As it turns out, this ability is, at least in part, our own work.

Recently, a team of researchers found that the “eyebrow” muscles that give dogs’ muzzles that charming, pleading expression are not commonly found in wolves, suggesting they evolved after we humans domesticated Canis familiaris.

“The raised inner brow in dogs is controlled by a muscle that does not exist in their closest relative, the wolf,” Ducane University anatomist Ann Burroughs said at the time.

“This movement makes a dog’s eyes appear larger, giving them a childish look. It can also mimic the facial movement humans make when they are sad,” adds evolutionary psychologist Bridget Waller from the University of Portsmouth, UK.

But the way we’ve changed our smart canine friends isn’t just limited to skin.

Burroughs and his colleagues continued their study of the eyebrows, finding that not only did dogs have different muscles from wolves, but so did the structure of their facial muscles. Even the internal composition of the facial muscles of dogs has changed and become remarkably similar to our own.

The stained muscle patterns around the mouth (orbicularis oris) below show that both dogs and humans have more fast twitch muscle fibers (dark spots) compared to slow twitch fibers (light spots), while wolves have all vice versa.

As implied, fast twitch fibers respond quickly – ideal for raising eyebrows or barking – but they also fatigue faster. Slow-twitch muscles maintain steady movements longer, as is required for wolf howls.

“These differences suggest that having faster muscle fibers contributes to a dog’s ability to communicate effectively with humans,” says Burroughs.

“During the process of domestication, humans could select dogs based on facial expressions that were similar to their own, and over time, the dogs’ muscles could evolve to become ‘faster’, further facilitating communication between dogs and humans.”

When our association with these animals was in its infancy, in the days of hunter-gatherers up to 40,000 years ago, it is clear that rapid interspecies communication provided a survival advantage against predators.

With so much pressure to communicate better with humans, natural selection has also honed the ability of dogs to understand us; in some ways, perhaps even better than we can understand each other. For starters, our canine companions can detect when we’re lying and instinctively sense and react to our moods.

“Dogs are unique among other mammals in their mutual bond with humans, which is manifested in mutual gaze, which we don’t see between humans and other domesticated mammals like horses or cats,” says Burroughs.

Our long history together with these animals has created a partnership unlike any other that has evolved and flourished through millennia of change to provide us with numerous benefits today. “During this time, dogs have also influenced our evolution – our connection is recorded in our genes.

It is well known that people, even at a young age, are innately gravitated towards a childlike appearance – a set of traits known as the “baby schema”. These traits include a comparatively large head relative to body size, large eyes, and a small nose, traits shared by many baby animals, including dogs and ourselves.

Brain scans have shown that children’s faces – no matter how related they are to us – affect our neurophysiology. They include our educational behavior. Data from animal shelters suggests this is true for dogs as well: those with child-enhanced facial features are more likely to be adopted.

Unfortunately, our innate propensity for human-childish cuteness has also led to great suffering among our beloved pets. By gradually deforming some breeds to suit our whims, over generations, we inadvertently leave them with serious medical problems.

Breeding for smaller dogs (big heads) has also made certain breeds more prone to heart disease. Selection for flatter, baby-like faces has resulted in other breeds such as pugs and bulldogs having difficulty performing the most basic daily function, breathing.

Here you can see how badly we have spoiled some breeds in over 100 years. The good news is that now that we understand how much we can influence their evolution, we can make better choices for them. At least we are indebted to the dogs.


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