Humans breed dogs with puppy eyes


Of course you are, but don’t blame your puppy. A new study suggests that humans are the culprits behind these irresistibly sweet voyeurs — in fact, we introduced these creepy eyes to today’s domestic dogs about 33,000 years ago.

“What makes dogs unique from other mammals is their reciprocal relationship with humans, as evidenced by mutual staring, which we do not observe between humans and other domesticated mammals such as horses or cats,” Annie Burrows, a professor in the department and lead author of the study, said in a statement.

“Throughout the domestication process, humans may have selectively bred dogs based on facial expressions similar to their own,” Burrows said.

It turns out that dogs’ facial muscles contract faster than their genetic cousins, wolves, Burrows said. This allows dogs to more closely mimic our expressions — or at least look at us in a way that breaks our hearts.

“It is possible that dogs’ muscles may evolve ‘faster’ over time, which will further benefit communication between dogs and humans,” Burrows said.

fast or slow muscle fibers

Fast-twitch fibers are present in every muscle in the body, allowing us to make sudden, more powerful movements, such as stepping out of the starting block during a race. However, fast-twitch muscles tire quickly, so we cannot maintain this strength for long.

As their name suggests, slow-twitch fibers run smoother and quieter, for example, allowing runners to excel in long marathons that require sustained energy.

Tiny “mock” muscles help shape mammalian facial expressions. In humans, these muscles contain a large number of fast-twitch fibers, which allow us to form facial expressions quickly and easily — imagine a smiling face in response to a joke or compliment.

The study, presented Tuesday at the annual meeting of the American Anatomical Society in Philadelphia, examined fibers in facial muscle samples from wolves and domestic dogs.

The results showed that compared to today’s domestic dogs, wolves had a lower percentage of fast-twitch fibers than slow-twitch fibers. According to the researchers, having slow muscles around the eyes and face can help wolves when they howl, while having more fast muscles can help dogs attract the attention of their owners with short barks and quick and varied expressions.

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

Wolves also lack another ability that most dogs have, According to a study prior to 2019There Burrows and his team. The study found that dogs have a muscle called the medial corner of the eye lift, which raises their inner “eyebrows” to make the eyes appear larger and more childish.A sort of 2013 Research Dogs who do this regularly are found to be more likely to be adopted.

“This eyebrow movement creates a ‘puppy-eye’ look similar to the facial expressions humans make when sad, making them irresistible and prompting a nurturing response in humans,” said co-author Madison Rango. Olmsted’s Health, laboratory manager of the University of Essex Schools. Department of Physical Therapy Sciences.

“We also know that we still subconsciously select for these traits in dogs,” Olmsted said, pointing to a 2013 Research This suggests that dogs with more frequent use of these expressions “are repatriated faster than less expressive dogs, reinforcing this evolutionary scenario even today.”

Another muscle, called the retractor lateral angularis, pulls the outer part The corners of the eyelids face toward the ears, which actually produce what humans call an “eye smile.” The 2019 study found that while wolves have some of this muscle fiber, most domestic dogs are more muscular and use it regularly.

The exception to this rule is the Siberian husky, which is more closely related to wolves than many other breeds, the researchers said.

If keeping your dog smiling and looking muscular isn’t enough, looking into the eyes of our “best friend” also seems to trigger an “oxytocin feedback loop” between humans and us. Dogs — like the kind that exist between us, human mothers and their babies, according to researchers.

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