Are you finding it difficult to resist those appealing eyes when your dog begs for a treat? Dogs and humans share a particular bond. Dog lovers are aware of a dog’s capacity to communicate through its eyes. Researchers have disputed for decades whether dogs learn to communicate by spending time with humans and practicing or if they are born with the ability to interpret this deceptively complicated form of communication. According to scientific evidence, this skill developed over time as canines learned to coexist with humans. Dogs’ eyes, like humans’, can be one of the most appealing features of the creatures renowned as “man’s best friend” in many cultures.
A new study showed that of the big reasons that could explain what makes dogs, in scientific terms, impossibly cute. Thousands of years of selective breeding may have contributed to dogs’ ability to develop facial expressions, according to the findings. The findings were reported at the American Association for Anatomy annual meeting on Tuesday, April 5, 2022, during the Experimental Biology (EB) 2022 meeting.
“Dogs are the only mammals that have a reciprocal bonding with humans,” said Anne Burrows, professor in the physical therapy department at Rangos School of Health Sciences at Duquesne University in Pittsburgh. She is also the study’s senior author. That bonding “may be demonstrated by mutual gazing, which we don’t see between humans and other domesticated mammals like horses and cats.” Our initial reports contribute to a better understanding of dog-human interactions and communication.“
Hence, by merely looking at each other’s faces, dogs and humans can easily capture each other’s attention — and derive deep meaning.
That kind of inter-species communication is quite rare. The study’s researchers had two key concerns. The first concern was to see if young puppies who hadn’t spent much time with humans were attentive to human communication attempts. The second question was whether the puppies’ social intelligence had a genetic basis.
Dogs and wolves
Wolves and dogs have a lot in common. Though the precise date is unknown, biologists believe the two species diverged genetically around 33,000 years ago, when humans started selectively breeding wolves, the first species ever to be domesticated. Scientists in Siberia recently discovered the 18,000 years old remnants of a dog, which could be the world’s dog ever. However, it could be a wolf. Facial musculature differences between wolves and dogs show that facial expressions played a part in dogs’ selective breeding and domestication.
The new research focuses on the architecture of mimetic muscles, which are small muscles that help produce facial expressions. These muscles in humans are dominated by “fast-twitch” myosin fibers, which contract swiftly and exhaust quickly, explaining why we can quickly create but not hold facial emotions. Muscle cells with more “slow-twitch” fibers are more efficient for long, controlled movements and are less likely to exhaust.
For this study, the scientists compared the ratio of fast-twitch and slow-twitch muscle fibers in certain facial muscles samples from wolves and domesticated dogs. The researchers analyzed fibers from two muscles (the zygomaticus major muscle and the orbicularis oris muscle) in gray wolves and many dog breeds. Fast-twitch muscle fibers can contract quickly, but growing tired doesn’t take long. Sprinters have more fast-twitch muscles in their legs than non-sprinters. Slow-twitch muscles aren’t as responsive as fast-twitch muscles, but they’re more efficient and last longer. Marathon runners are more likely to experience this.
The results were stunning. The researcher found the facial structure of both animals was mostly very similar. However, one major difference was discovered above the eyes.
“These differences show that having faster muscle fibers aids a dog’s effective communication skills with people,” Burrows said.
“During the domestication process, people may have selectively bred dogs with facial expressions similar to their own. Dog muscles may have become ‘faster,’ further aiding dog-human communication.”
The research reveals that similar to humans, faster muscle fibers aid a dog’s capacity to communicate effectively with humans. Fast-twitch fibers dominate the face muscles of both wolves and domesticated dogs, while wolves have a higher fraction of slow-twitch fibers than dogs. Fast-twitch fibers made up between 66 to 95 percent of the muscles in the dogs’ faces. For wolves, the percentage was only 25%. On the other hand, dogs had only 10% slow-twitch fibers in their faces, whereas wolves had 29%.
According to Burrows, the findings reveal what humans look for in dogs. “Humans may have selectively bred dogs based on facial expressions similar to their own during the domestication process,” she says. “Over time, dog muscles may have developed to become ‘faster,’ enhancing expressions between humans and canines.”
Moreover, having more swift fibers provides for higher facial mobility and faster muscular movement, allowing for small motions like raising an eyebrow and the short, intense muscle contractions required for barking. Slow-twitch fibers, however, are important for longer muscle motions, such as those used by wolves when howling.
The findings constitute a crucial component of the puzzle
The research isn’t the first evidence that explains how dogs became so darn cute. A few years ago, Burrows and other scientists reported evidence that dogs have a special muscle that enables them to raise their eyebrows in that special puppy-dog way.
They also analyzed canine and wolf behavior, discovering that dogs lift their eyebrows considerably more frequently and intensely than wolves. Those facial expressions make adult dogs seem more like puppies and resemble “an expression that humans produce when sad,” the authors write. “We think that dogs with expressive eyebrows had an advantage in the breeding process and that ‘puppy dog eyes’ are the results of human-driven selects,” they said.