PHILADELPHIA, Pa. (StudyFinds.org) — How did dogs get those irresistible puppy eyes? It turns out that it took a lot of effort from our ancestors. Researchers believe humans selectively bred the first domesticated dogs thousands of years ago to get those big, sad eyes that no dog owner can say no to!
Their recent study explains that expressions of adoration and pleading in dogs are actually meant to allow them to make more human faces. The more they pull off this “puppy eye” trick, the more treats they get – and the more humans breed them in order to retain this desirable trait.
The team adds that it likely took thousands of years of selective breeding to achieve this facial expression-forming trait. In the study, the researchers analyzed the anatomy of tiny muscles used to form facial expressions called mimetic muscles.
In humans, these muscles feature mostly “fast-twitch” myosin fibers that contract quickly but also tire quickly. This explains why we can form facial expressions quickly but not retain them for long. Muscle cells with more “slow twitch” fibers are more efficient at long, controlled movements and don’t tire as quickly.
For the study, the researchers compared myosin fibers in facial muscle samples from wolves and domestic dogs. The results revealed that, like humans, dogs and wolves have facial muscles that are primarily fast-twitch fibers, but wolves have a higher percentage of slow-twitch fibers compared to dogs.
Barking and howling use different types of muscles
Having more fast-twitch fibers allows for greater facial mobility and faster muscle movements, allowing for small movements such as a raised eyebrow and the short, powerful muscle contractions involved in barking.
Slow-twitch fibers, on the other hand, are important for prolonged muscle movements such as those wolves use when they howl. Dogs also have an extra muscle that is missing in wolves that contributes to the expression “puppy eye.”
“Dogs are unique from other mammals in their reciprocal bond with humans which can be demonstrated by mutual gaze, something we do not observe between humans and other domesticated mammals such as horses or cats,” says Professor Anne Burrows of Duquesne University in a press release. . “Our preliminary results provide insight into the role that facial expressions play in dog-human interactions and communication.
“These differences suggest that having faster muscle fibers contributes to a dog’s ability to communicate effectively with people,” adds the study author.
“Throughout the process of domestication, humans may have selectively bred dogs based on facial expressions similar to their own, and over time dogs’ muscles may have evolved to become ‘faster’. , which further benefits the communication between dogs and humans.”
The research team presented their findings at the American Association for Anatomy annual meeting during Experimental Biology 2022.
South West News Service writer Joe Morgan contributed to this report.