There’s no denying that a puppy’s “pity” look is capable of softening any owner’s heart. But why do the features of these animals mess with humans so much? A study by Duquesne University, in the United States, reveals anatomical characteristics present in dogs that may explain this link between the two species.
In the study, researchers report finding that the “eyebrow” muscles that contort canine faces into such cute expressions are not present in wolves, their closest relative. This leads researchers to believe that this musculature arose in dogs after they were domesticated by humans.
“The internal movement of the raised eyebrow in dogs is driven by a muscle that does not consistently exist in its closest living relative, the wolf,” said University of Duquesne anatomist Anne Burrows.
“This movement makes a dog’s eyes appear larger, giving them a childlike appearance. They can also mimic the facial movement humans make when they are sad,” added evolutionary psychologist Bridget Waller of the University of Portsmouth, UK.
But, according to the study, this change in “expression” was not superficial and can be explained by genetics. Dogs not only have different musculature than wolves, but even the structures of these muscles are also different. The internal composition of the dog’s facial musculature changed and became quite similar to that of humans.
Samples of the muscle around the mouth (orbicularis oris) show that dogs and humans have more fast-twitch muscle fibers compared to slow-twitch fibers, while wolves have more slow-twitch fibers.
Fast ones are perfect for immediate reactions like raising eyebrows or barking, but they tire more quickly. Slow ones maintain movements longer, like those needed for a wolf’s howl, for example.
“Throughout the domestication process, humans may have selectively bred dogs based on facial expressions similar to their own, and over time the dogs’ muscles may have evolved to become ‘faster’, further benefiting dog-to-dog communication. and humans,” Burrows said.
40 thousand years of evolution
When humans’ bond with these animals began around 40,000 years ago, rapid communication between species provided a survival advantage against mutual predators.
“Dogs are unique among mammals in their reciprocal bonding with humans, which can be demonstrated through mutual gaze, something we don’t see between humans and other domesticated mammals such as horses or cats,” Burrows added. .
The long history of man and dogs has created a partnership unlike any other that has developed and thrived through millennia of change. Over that time, dogs have also influenced human evolution.
Humans are already proven to be attracted to a childlike facial appearance – a set of childlike traits known as ‘baby schema’. These traits include a large head compared to their body size, large eyes, and a small nose – traits shared by many puppies, including dogs and ours.
The human brain reveals that babies’ faces (regardless of kinship) directly target neurophysiology and activate our nurturing and protective behavior. Data from animal shelters suggests this also applies to dogs: those who have enhanced baby schema facial features are more likely to be adopted first.
Preliminary muscle structure results were presented at the annual meeting of the American Anatomy Association.