The dog has not always been man’s best friend; it was selected and evolved to match the criteria of humans.
Since the domestication of canids, tens of millennia ago, we have had countless proofs that show the very special bond that unites these majestic beasts to the human species. In many ways, this relationship is unique in human history; it is no coincidence that today we speak of “man’s best friend”. And researchers have just discovered one of the driving forces behind this dynamic.
“Dogs are unique in their reciprocal bond with humans“, explains the co-author of the study Anne Burrows. “This is especially noticeable in the exchange of glances; it’s something you don’t see with other domesticated animals“, she insists.
From wolf to dog, millennia of evolution and selection
In an attempt to discover the causes of this privileged relationship, Burrows and his team began by comparing the anatomy of contemporary dogs to that of their ancestors, the wolves. It’s a way to determine which traits have been favored by “natural” selection since the first canids were domesticated more than 15,000 years ago.
Since then, our two species have formed a formidable tandem; while they are no longer as important to our survival as they were at the dawn of humanity, they continue to occupy a considerable place in many cultures. And over the millennia, these species have evolved considerably in contact with humans.
These changes are the result of two parallel factors. First, there is the conscious selection made by humans to select the most desirable traits. These can be behavioral traits like loyalty or the shepherding instinct. Today, aesthetic criteria are also very important for owners.
But there is also another level to take into account: in addition to this human selection, dogs have continued to be subject to a form of selection that one could almost call “natural”, because it is not consciously practiced by humans.
Indeed, since Man actively selects dogs on the basis of these aesthetic criteria, natural selection also tends to favor individuals who satisfy these criteria. By evolving in contact with our species, it turns out that dogs have developed certain traits that are particularly useful for interacting with us.
Facial expressions at the service of social relations
In this case, the muscles of the face are part of these features. To summarize very briefly, in mammals, there are two major categories of muscle fibers; slow twitch fibers and fast twitch fibers.
Slow fibers are short, stout, and highly vascularized; they are what allow you to sustain efforts such as running a marathon or carrying a load. At the opposite end of the spectrum, fast fibers are much more reactive. Some serve in explosive efforts; others are used for fine and delicate movements. It is found, for example, in the fingers or in the muscles of the face which define the expressions.
And it is precisely the latter that have troubled the researchers. They realized that in wolves, the facial musculature is mainly composed of slow fibers (75%). On the other hand, in contemporary domesticated dogs, there are significantly more fast fibers that serve to control expression (66 to 95%).
It is this element that allows them, for example, to use the famous “dog eyes” when asking for a treat. It is therefore a fundamental element in the relationship between our two species. Indeed, numerous studies have already shown that human beings reacts instinctively to the faces of its fellow creatures (see Perception of faces). Sometimes this neurological wiring also pushes us to spot these same expressions in very abstract forms. It also works with animals, as with the famous “smile” of the Shiba Inus.
An evolving Stockholm syndrome
Quite often, the interpretation is totally wrong; in the majority of cases, these “expressions” do not have the same meaning at all from one species to another. But our brain is all the same programmed to recognize them; unconsciously, we therefore selected dogs with more pronounced facial expressionsand so more satisfying for our brain calibrated from human relations.
“During the process of domestication, humans selected dogs based on facial expressions similar to ours“, explains Anne Burrows. “The dogs’ muscles could therefore have evolved in parallel to develop more fast fibers, which further facilitated communication between our two species.”, she specifies.
In other words: humans started a process of artificial selection based on their own criteria, and evolution did the rest. And that owes nothing to chance. Indeed, in the West, there are almost no more real species of wild dogs. The survival of the species therefore depends on their status as domestic animals, and by extension, on their relationship with humans; and by strengthening their arsenal of communication with humans, these species have also greatly improved their chances of survival. A sort of progressive Stockholm syndrome, in short.
Does this mean that evolution will eventually endow them with speech for these same reasons? See you in a few millennia to find out!
The text of the study is available here.