“Puppy eyes”: 30,000 years of dog and human co-evolution

A dog is a very unusual creature. She never harasses with questions what mood you have, she is not interested in whether you are rich or poor, stupid or smart, a sinner or a saint. You are her friend. This is enough for her.

These words belong to the writer Jerome K. Jerome, whom many of us know from the work “Three in a boat, not counting the dog” and the film adaptation of the same name with Mironov, Shirvindt and Derzhavin.

Dogs have been constant companions of humans for many thousands of years. They are our friends, helpers and sometimes support, without which it is difficult to live (what are guide dogs, rescue dogs, etc.). Such a long joint coexistence has affected not only us and our attitude towards dogs, but also dogs, and not only in a behavioral, but also in an anatomical sense. Today we will get to know a study of the physiognomy of dogs, in which scientists found evidence that our smaller brothers evolved to adapt to us. What specific anatomical changes were discovered, why are they needed, and how do dog emotions differ from wolf emotions in terms of physiognomy? Answers await us in a report by scientists. Go.

Study basis

Many thousands of years ago, not particularly intellectually gifted, wild and not domesticated predators - people walked the earth. In the neighborhood with people lived a great variety of animals and plants. Some representatives of the flora and fauna were later domesticated by humans for their own purposes, as a result of which we now have pets and wheat fields. However, the primary source of the domestication process is still uncertain, especially in the aspect of the connection between man and the wolf (subsequently dogs). Some believe that people began to tame wolves, while others - that wolves themselves began to approach people, due to their close proximity.


Rock carvings of a joint hunt of a man and a dog (Tassilin-Adjer plateau, Algeria)

We cannot say for sure how the relationship between man and dog began, but we know for sure what benefits both sides had from this symbiosis. People of those times, although they could not write a dissertation on quantum physics, they understood very well from their own observations that wolves / dogs possess a number of outstanding characteristics: good hearing, sharp sense of smell, ability to run fast and painfully bite. Therefore, first of all, a man used domesticated dogs for hunting, protecting his home and pastures of domesticated cattle. You can also highlight several other useful "skills" of dogs - they eat and they are warm. It sounds strange, I know, but dogs in human settlements acted as orderlies (like ants in the woods), eating out the remnants of human food. And on cold nights, dogs served people like living radiators.


“The Boar Hunt” (1640, the author of the picture is France Sneijders)

Besides the practical benefits of dogs, there was also a socio-cultural one. Scientists believe that it was thanks to the dogs that some aspects of the behavior of ancient people changed: marking the territory and group hunting.

We can consider our ancestors not the most intelligent, and therefore not the most cultural beings, but this will be an erroneous statement, which is refuted in relation to the dog, among other things. Archaeologists around the world find the burial of man and his dogs. Pets were not killed after the death of their owners, do not worry. The dog died his own death and was buried in the grave of the owner.


Excavations of the burial place of a person and his dog (age from 5000 to 8000 years).

This is only a brief description of the relationship between our ancestors and dogs, but it is already becoming clear that a dog for a person has always been something more than just an animal with fangs, paws and tail. The dog has become the same social element of human society, like any single person.

And what is one of the most important elements of socialization? Of course, the ability and ability to communicate, that is, communicate with each other. It is easier for us humans - we can speak. Dogs do not have such an opportunity, because they use everything that they have in their arsenal, so that we can understand them: wagging their tail, growling or barking and facial expressions, or rather muzzles. And here the fun begins. A person has 43 facial muscles (correct me if this number is wrong). Thanks to this amount, we can express a very wide range of emotions, comparable to the color gradient, in which there are both basic tones and shades. We can say nothing, not move, look at one point, and only a slightly raised eyebrow will already be a sign of a certain emotion. What about emotions in dogs? They have them, we note for starters. How do they express them? They jump, wave their tail, bark, growl, whine and raise their eyebrows. The last point is the merit of man, to some extent. Prehistoric dogs, like modern wolves, do not have specific muscles that allow domestic dogs to make muzzle expressions called "puppy eyes."

This is precisely the essence of the study we are considering today. Now let's take a closer look at its details.

Research results

First of all, scientists note that people have certain subconscious preferences when it comes to faces (I don’t want to use the word “face” somehow) pets, namely pedomorphism - the presence of children's facial features in an adult or animal. In our case, pets also have such features - a high forehead, large eyes, etc. This is due, according to some researchers, to the fact that a child appears to be a harmless creature, but a pet (even a pet) remains an animal whose behavior can not always be predicted.

This theory is very peculiar, but it is confirmed even in cinema, especially in animation.


As you can see, Toothless has very big eyes, and it’s not just like that. Due to this, we subconsciously perceive it with a positive emotional color, despite the fact that we face a dragon. And the dragon didn’t sneeze at you (ask the inhabitants of the Royal Harbor).

In any case, when the subjects were asked to choose the animals that they like best from a number of animal images, the majority chose those pets who had pedomorphic features.

Scientists also believe that such features can be enhanced by the work of certain muscles, that is, they were “artificially” strengthened. Accordingly, some logic is already visible in the raised eyebrows in dogs, explaining why a normal person can not resist such an expression on his face.

There are muscles due to which the inner part of the eyebrow is raised, which makes the dog’s eyes look so big and sad. But do wolves have such muscles? Maybe they simply do not use them, because their communication with a person is very limited. No, wolves do not have such muscles, because they evolved in a different way.

To prove this, scientists conducted a study of the structure of the facial muscles of gray wolves ( Canis lupus , 4 samples) and domestic dogs ( Canis famisis, 6 samples). It is worth noting that all samples for dissection were provided by the Museum of Medicine, that is, the animals died a natural death, and were not killed for research. Also, observations were made on the behavior of wolves (9 individuals) and dogs (27 individuals) during communication with humans, which made it possible to observe first-hand muscle activity on the face, so to speak.


Image No. 1

As can be seen from the schematic comparative image of the facial muscles of the dog (left) and the wolf (right), in both versions the muscles have the same features, except for one detail - the muscles around the eyes.

In dogs, a muscle called levator anguli oculi medialis(LAOM) was fully present and developed, and the wolves had only minor and undeveloped muscle fibers, heavily covered with connective tissue. Quite often, the presence of a tendon was observed in the wolves, which fused with the medial sections of the fibers of the circular muscle of the eye in the place where the LAOM was present in the dogs.


This apparent difference in muscle structure suggests that it is more difficult for wolves to raise the inside of their eyebrows.

In addition, differences in retractor anguli oculi lateralis muscle (RAOL) were also observed. This muscle was present in both dogs and wolves. But in the latter, it was mild and was only an accumulation of muscle fibers.


A comparison table of the structure of the facial muscles of wolves (C. lupus) and dogs (C. familiaris). Designations: P - muscle is present in all samples; V - muscle is present, but not in all samples; A - muscle is present in most samples; * - muscle was absent in one of the wolf samples; †- the muscle of the wolves was not presented as complete, but as a cluster of fibers; ‡ - the muscle was found in all canine specimens, except for the Siberian husky (could not be found during dissection).

The RAOL muscle pulls the lateral angle of the eyelids to the ears. Most domestic dogs possess this muscle, except for the Siberian husky, since this breed is older, that is, it is more closely associated with wolves than other breeds.

These findings of a study on the anatomy of wolves and dogs were confirmed during behavioral tests. From different kennels 27 dogs were brought, to which a stranger approached them in turn and filmed their response to it within 2 minutes. The wolves were brought from two different institutions where they lived with their packs. Each of the wolves (9 individuals) was also approached by a stranger and removed their response within 2 minutes.

Puppy eyes, which scientists gave the more severe code name AU101, were analyzed and classified according to intensity, ranging from low (A) to high (E).

Comparison of the frequency of AU101 between species showed that dogs use this facial expression much more often than wolves (M _dn= 2, Mann-Whitney: U = 36, z = −3.13, P = 0.001).

A comparison of the AU101 intensity between species showed that low intensity (A) occurs with the same frequency in dogs and wolves. Increased intensity (C) occurs in dogs more often, but the maximum intensity (D and E) occurs exclusively in dogs.

Researchers Findings

The results of a study of the muscle structure of dogs and wolves in conjunction with the conducted behavioral observations provided conclusive evidence that mimic muscles were formed in dogs during domestication. Scientists consider this surprising, since this process began not so long ago, 33,000 years ago. The complexity of such studies is that soft tissues (in this case, muscles) can not always be detected in the form of fossils. Therefore, it is necessary to use other research methods. In this work, modern wolves were used, which did not go very far anatomically from their ancestors, in contrast to domestic dogs.

The next conclusion is that the appearance of facial muscles is directly related to the close communication of dogs and humans. Raising the inner part of the eyebrows, the dog makes its eyes larger, thereby causing the person to subconsciously associate with something safe, good and requiring a positive emotional response. This is not so strange considering the importance of eyebrows in communication between a person and a person. The movement and position of the eyebrows plays an important role in placing emphasis during the conversation, as certain emotional markers. People subconsciously follow the eyebrows of the interlocutor with special attention.

For the time being, one thing is unclear - thousands of years ago during the selection, people knew about the mimic muscles of dogs and intentionally tried to derive new breeds that would possess them, or this anatomical feature was not studied by people and was transmitted from one generation to another without any selection in any form? The answer to this question has not yet been found, but scientists do not stop searching.

For a more detailed acquaintance with the nuances of the study, I recommend that you look into the report of scientists .

Epilogue

A dog is a friend of man. Many thousands of years ago, humans and dogs began to live together, caring for each other's good. And even now, in the era of technological progress, when any super-sophisticated robot can do any canine work, we still give preference to our four-legged friends.

Dogs perform many important and complex tasks, ranging from searching for missing after incidents and ending with the help of blind owners. But even if your dog is not a lifesaver and a guide, you still love her and trust her sometimes more than people.

Dogs, like any other pets, are not just live toys in the house, they become members of the family and deserve appropriate respect, care and love. After all, as Jerome K. Jerome said: “... she is not interested in whether you are rich or poor, stupid or smart, a sinner or a saint. You are her friend. That’s enough for her. ”



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