Whether you like dogs or not, you have to admit that sometimes they look irresistible, especially when they have something to forgive or require a little attention from their owner. It is curious that other animals of the Canidae family, such as wolves or foxes, do not generate such enthusiasm. Of course, unlike dogs, they are not domesticated and therefore have little to do with the human race. But other domesticated mammals (cats, horses) do not cause such reactions. Today’s research reveals the science behind the famous “Coker’s view.”
Eye contact, a key element of human-dog communication
This study was led by Ann Burroughs, a biological anthropologist in the Department of Physical Therapy at Duken University in Pittsburgh, who has long been interested in the relationship between humans and dogs. ” Dogs are distinguished from other mammals by their mutual bond with humans, which can be demonstrated by a mutual gaze that we do not see between humans and other domesticated mammals. Indeed, there is evidence that dogs are motivated to make eye contact with humans from an early age; for example, they make eye contact when they cannot solve a problem on their own.
This characteristic is not the result of chance: the dog’s appearance has evolved over time to communicate better with humans. ” Dogs were formed in the process of domestication both in behavior and in anatomical features. ‘, the authors of the study conclude. Proceedings of the National Academy of Sciences. This study is the first detailed analysis comparing the facial anatomy of dogs and wolves.
A wild gray wolf (left) and a domesticated Bernese mountain dog (right) have some differences in facial features. Most domestic dog breeds have short muzzles, flat ears, and a variety of fur patterns and colors. Red arrows point to the levator ocular muscle, which is absent in the gray wolf. Credits: Wildlife Defenders, Washington DC/Anne Burrows, Duquesne University.
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Dogs and wolves are closely related. While the exact time is not known, scientists believe that the two species diverged genetically around 33,000 years ago when humans started domesticating some wolves. However, this domestication appears to have caused an anatomical modification of the facial muscles of these animals, which facilitated their communication with humans.
In humans, the muscles that control facial expression (called facial muscles) are primarily composed of so-called “rapid twitch” myosin fibers; these muscles are able to contract quickly, but also quickly get tired – that’s why we can’t keep facial expressions for a long time.
Comparing facial muscle samples from wolves and dogs, the researchers found that, like humans, both had fast-twitch fibers; however, the wolf had a higher proportion of slow twitch fibers that are used for long facial movements such as those performed during howls. ” These differences suggest that having faster muscle fibers contributes to a dog’s ability to communicate effectively with humans. Burroughs said.
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Evolution based on human preferences
The researchers also found that medial muscle that lifts the corner of the eye (LAOM), the muscle responsible for raising the inner eyebrow, is usually present in dogs but not in wolves. The only dog species in the study that did not have this muscle was the Siberian Husky, which is one of the oldest breeds (thus most closely related to the wolf). Behavioral data also showed that dogs produce this brow movement much more frequently and with greater intensity than wolves, with the most intense movements produced exclusively by dogs, the team notes. This muscle supports all visual communication between dogs and humans.
Facial musculature in dogs (C. familiaris) and wolves (C. lupus); anatomical differences are shown in red. Credit: Tim D. Smith/Cambridge University Press.
Another interesting fact noted in this study is that this raising of the eyebrows increases paedomorphism, that is, the preservation of youthful features into adulthood; thus, their eyes appear larger, reminiscent of a puppy’s eyes, and above all create an expression similar to that shown by humans when they are sad. Therefore, this expression in dogs may cause humans to want to comfort and/or provide pleasure (eg, food rewards).
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The authors of the study suggest that this unique ability in dogs is the result of a selection process based (consciously or unconsciously) on human preferences. ” Throughout the process of domestication, humans have been able to selectively crossbreed dogs based on facial expressions similar to their own. “, – explains the specialist. This choice can also be based on the fact that people have a preference for individuals that show the whites of the eyes (raising the eyebrow exposes the white part of the dog’s eyes).
Thus, these muscle changes will be directly related to the increased social interaction of dogs with humans. Further studies are needed to confirm these findings. The use of dyes to distinguish other types of muscle fibers may, in particular, reveal additional anatomical differences between dogs and wolves, revealing other mechanisms underlying domestication.