There’s no denying that a pup’s “pitying” look can soften any owner’s heart. But why do the characteristics of these animals confuse people so much? A study from Duquesne University in the United States reveals anatomical features in dogs that could explain this link between the two species.
In the study, researchers report that the “eyebrow” muscles that contort canine faces into such cute expressions are absent in wolves, their closest relatives. 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 is not consistently present in its closest living relative, the wolf,” said Anne Burrows, an anatomist at the University of Duquesne.
“This movement makes a dog’s eyes appear larger and gives them a childlike look. They can also mimic the facial movements humans make when they’re sad,” added evolutionary psychologist Bridget Waller of the University of Portsmouth, UK.
But according to the study, this change in “expression” was nothing superficial and can be explained genetically. Not only do dogs have different muscles than wolves, the structures of these muscles are also different. The inner composition of the dog’s facial muscles 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 fasttwitch muscle fibers compared to slowtwitch fibers, while wolves have more slowtwitch fibers.
Fast ones are perfect for immediate reactions like raising an eyebrow or barking, but they tire more quickly. Slower movements last longer, such as those needed for a wolf howling.
“Throughout the domestication process, humans may have selectively bred dogs based on facial expressions that resembled their own, and over time, dogs’ muscles may have evolved to be ‘faster,’ furthering dogtodog communication.” benefits,” said Burrows.
40,000 years of evolution
When humans began to bond with these animals about 40,000 years ago, rapid communication between species offered a survival advantage over each other’s predators.
“Dogs are unique among mammals in their mutual bonding with humans, which can be demonstrated through mutual gazes, something we don’t see between humans and other domesticated mammals like horses or cats,” Burrows added.
The long history of humans and dogs has created a unique partnership that has evolved and thrived through millennia of change. During this time, dogs also influenced human evolution.
It has already been proven that people are attracted to a childlike facial expression a set of childlike traits known as the “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 shows that babies’ faces (regardless of kinship) directly target neurophysiology, activating our caring and protective behaviors. Data from animal shelters suggests the same is true for dogs: those that display enhanced Baby Schema facial features are more likely to be adopted first.
Preliminary muscle structure results were presented at the American Anatomy Association annual meeting.