Although it is not known exactly when and where humans began to domesticate dogs, most scientists agree that early genetic differences from wolves, the animals from which they descend, must be placed around 33 thousand years ago. The fact that dogs today know how to beat food or caress with one look at their owners is not a coincidence: study He points out that these animals began to develop their facial muscles in a way that they communicate better with and like humans more, a process in which domestication plays an important role.
The research was conducted by Ann Burroughs, professor of biological anthropology at Duquesne University in Pittsburgh (Pennsylvania) and she was Foot April 5 at a meeting of the American Society of Anatomy in Philadelphia. It relies in particular on the anatomical study of muscles that allow animals – including humans – to change facial expressions, that is, mimic facial muscles.
To simplify, most of these muscles in humans feature fibers that contract quickly and easily (and tire just as quickly), allowing you to automatically smile in response to a compliment or an eyebrow raise. Then there are mimic muscles with slower-contracting fibers, which are instead used in prolonged movements over time. Burroughs’ research and colleague Kayleigh Madison Omstead, head of his university’s Laboratory of Biological Research, focused on fast-twitching fibers found in the facial muscles of domesticated wolves and dogs.
According to the results of the study, the proportion of fibers of this type found in the facial muscles of dogs ranges between 66 and 95 percent, while it stops in wolves at 25 percent. In contrast, a much higher proportion of type II fibers were found in the wolves’ facial muscles – 29 percent compared to about 10 percent in dogs. From an evolution point of view, researchers hypothesize that the presence of fibers that contract more slowly may have facilitated wolves in long, controlled movements, such as howls; However, in dogs, those that contract faster may have evolved to get humans’ attention through eye expression or shorter barks.
The researchers’ hypothesis is that during the domestication process, humans selected and bred dogs to some extent based on facial expressions they found to be very similar to theirs, at the same time the dogs’ muscle fibers evolved in a way to improve the animals’ communication with their owners.
As another already pointed out study From 2019 also conducted by Burrows, with evolution dogs, they have also developed a specific muscle that allows them to raise the arch of the eyebrow, making their eyes appear larger and making them more human-like, so to speak: this expression evokes the expression of people when they are sad, and thus stimulates the owners to want to be cared them, Note Omstead. Another muscle that is always developing in dogs and also found in wolves, but is less used, instead allows the outer ends of their eyes to be extended toward the ears, producing an expression that humans can remember about “smiling” eyes.
“Dogs are really unique compared to all other pets because their relationship to humans is shown by staring at each other, something not observed in other domesticated mammals, such as horses or cats,” Burroughs commented. Amstead noted that the study’s findings suggest that humans may have “intentionally or not” bred dogs with facial expressions similar to theirs, and added, “We also know that we are still unconsciously looking for these traits in dogs.”
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