Although it is not known exactly when and where dogs were domesticated by humans, most scientists agree that the earliest genetic differences from wolves, the animals from which they descended, can be found around 33,000 years ago. The fact that dogs today know how to conquer food or cuddles with a single glance at their owner is no coincidence: a recent study shows that these animals have begun to develop facial muscles to better communicate with humans and him to like more. a process in which domestication would play an important role.
The research, conducted by Anne Burrows, professor of biological anthropology at Duquesne University in Pittsburgh, Pennsylvania, was presented April 5 during a meeting of the American Association for Anatomy in Philadelphia. In particular, it is based on the anatomical study of the muscles that allow animals including humans to change facial expression, i.e. the mimic facial muscles.
Put simply, most of these muscles in humans are characterized by fibers that contract very quickly and easily (and tire just as quickly), allowing you to smile spontaneously in response to a compliment or a raised eyebrow. then there are mimic muscles with fibers that contract more slowly that are instead used for longer actions over time. The fasttwitch fibers in the facial muscles of wolves and domestic dogs have been the focus of research by Burrows and his colleague Kailey Madisen Omstead, director of his own university’s biological research laboratory.
According to the results of the study, the proportion of such fibers in the facial muscles of dogs varies between 66 and 95 percent, in wolves it is 25 percent. In contrast, a much higher proportion of fibers of the second type were found in the facial muscles of wolves 29 percent compared to about 10 percent in dogs. From an evolutionary perspective, the researchers hypothesize that the presence of fibers that contract more slowly may have aided wolves in long and controlled movements such as howling; however, in dogs, those have evolved that contract faster to attract human attention through the expressiveness of the eyes or with shorter barks.
The researchers hypothesize that during the domestication process, humans selected and raised dogs in part based on facial expressions they found most similar to their own, and that at the same time, the dogs’ muscle fibers were developing in a way that is said to improve the animals’ communication with owners .
As another 2019 study by Burrows pointed out, dogs also evolved a specific muscle that allows them to raise the arch of their eyebrows, making their eyes appear larger and more pleasing to humans, so to speak: that expression reminds people when they’re sad, and therefore encourages owners to care for them, Omstead noted. Another muscle, always developed in dogs and also present in wolves but used much less, allows the outer ends of their eyes to extend towards their ears instead, creating an expression that humans tend to latch on to that of the “smiling” eyes.
“Dogs are truly unique compared to all other domesticated animals because their bond with humans is demonstrated through mutual gazes, something not seen in other domesticated mammals like horses or cats,” Burrows commented. The study’s results suggest that people may have “intentionally or not” bred dogs that more closely resembled their own facial expressions, Omstead added. “We also know that we’re still subconsciously looking for these traits in dogs,” concludes he.
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