The Dog's Eye - Evolutionary Advantage

16. July 2022 — von Ramona Koppensteiner

The dog is not only a loyal companion, but also man's best friend. But how did this intimate friendship between dog and human come about? We can hardly resist the dog's gaze in particular - it could be an evolutionary advantage for the dog.

From wolf to family member

About 15,000 years ago, humans began to domesticate the wolf, making it our first pet and faithful companion. At the time of domestication, there was an ice age and the winters were cold. It is possible that the diet, which was specially adapted to the cold winter months, contributed to the fact that humans did not compete with wolves for food and that the wolves thus became closer to humans.
Our hunting ancestors often left parts of their prey as waste, because they needed above all sufficient carbohydrates and fats. It was precisely this leftover, lean and protein-rich portion that was an optimal food for the carnivorous wolves. Therefore, it is assumed that the wild relative of our present-day dogs sought out the vicinity of the campsites during this difficult time. In return, the people received protection from the pack staying near them. Despite all the theories, it is still not completely clear today how exactly the dog became our companion.

In contrast to the wolf, which lives as a social hunter in the wild, the dog as we know it today seems to be perfectly adapted to life with us humans. In direct comparison, the amazing variety of shapes of the dog breeds is striking.
This great variability in colouration, coat and shape, caused by breeding, is actually only found in domestic dogs. The wolf differs in shape and size from the domestic dogs we know today, and there are also differences in the reproduction rate - while the wolf has offspring once a year at the most, the dogs can have offspring up to twice.

The wolf also differs anatomically from the dog. For example, the wolf's dentition is larger in comparison to its body weight and the brain areas associated with eyes, nose and ears are particularly pronounced. It is therefore assumed that the wolf can see, smell and hear better than its domesticated relatives.
Another evolutionary adaptation is a special facial muscle (Musculus levator anguli oculi med.), which enables the lifting of the inner eyebrows - this is much more pronounced in the dog. In the wolf, there are only sparse muscle fibres and connective tissue in this region. This stronger development of the muscle probably occurred because it enables better mimic communication with us humans.

The "dog eye" - an evolved ability

In the pack animal wolf, communication among each other must run smoothly in order to guarantee a peaceful and common coexistence. If serious disputes arise, it is important to get along again as quickly as possible so as not to endanger coexistence. Wolves are therefore highly social animals.

By living closely together with us humans, dogs have learned over time to read our facial expressions as well - so life in a group can be kept harmonious even with humans. In a scientific study, the reactions of wolves were compared with those of dogs. For this purpose, a piece of meat was placed in a locked cage, the wolf as well as the dog was placed in front of the cage. A caregiver stood behind each animal, but in such a way that no direct eye contact could be made. The wolf tried its luck for a long time in vain and gave up in the end, whereas the dog immediately sought eye contact with its caregiver after brief attempts.
In this behavioural research, it became clear that the dog wanted to make direct eye contact with its caregiver, the so-called "dog-eye", in order to find a solution to the problem together.

In the course of living together with us humans, the dog has adapted to us in its mimic behaviour, whereby eye contact became decisive for the joint interaction of humans and dogs. Particularly important here is the development of the special muscle that allows dogs to raise their inner eyebrows - the so-called "dog look" develops. Basically, dogs use this look to get in contact with us, because we might have the right solution at hand. Over the years, dog and human have become a well-rehearsed team.
What we can say with certainty is that we humans react very intelligently to such looks. We all know exactly what to do when the dog sits next to us at the breakfast table and his gaze wanders back and forth between his food bowl and us. Or when he runs towards us with his favourite toy, tail wagging, puts it on the floor in front of us and looks at us expectantly.

But how did the dog's eye develop? Presumably, individual wolves/dogs that happened to have a higher mimic adaptation to us humans gained an advantage over time.