What did dogs look like in the early days?

From Chihuahua to Saint-Bernard, passing Borzois greyhounds with their unusually tall skulls, dogs now appear in a remarkable variety of shapes, while all come from the same ancestor, the gray wolf. This high innovation is recent, as it is linked to the intensive selections made over the past 200 years for the production of the 355 varieties now recognized by the Fédération Cynologique Internationale. But what do we know about the appearance of early dogs, in early times? This is the question we answered in our article published this May 18 in the scientific journal Royal Society Procedures B.

Our research has shown, for the first time, that at this very early age dogs already have a variety of head sizes and shapes.

All dogs today are from the same ancestor

All dogs are from the same ancestor: the gray wolf. At least 15,000 years ago in the Upper Paleolithic (the exact date and location of the settlement remains a matter of debate), fearless and aggressive wolves belonging to a now extinct generation would have been attracted to the camps. in humans, likely to take advantage of leftover food. . Prehistoric people then approached these wolves, they brought them help to hunt or to protect their camps against the attacks of other predators. We would have tamed the less wild of them, breeding them and thus nourishing them over time.

This lifestyle is accompanied by many genetic, physiological, behavioral and even physical changes, most of which are unintentional. Among the morphological changes, archaeozoologists (experts in human-animal relations in the past) and paleogeneticists noticed differences in coat color, a decrease in size, less marked differences. between males and females and the preservation of younger traits, resulting in changes in skeletal dimensions with a strongly marked and shortened muzzle and more frequent dental anomalies ( loss or rotation of some teeth) due to lack of space.

In addition, a study conducted since the 1960s in Siberia showed that by selecting the most rare and less aggressive wolves of the generations (thus recreating the hypothetical conditions of the first encounters between men and wolves), the animals became more and more obedient, their The level of stress (valued in the secretion of cortisol) decreased, and that they presented the same morphological differences as observed by archaeozoologists during moving from wolves to dogs. Domestication also changes the anatomy of the facial muscles, to allow for the raising of the eyebrows.

A diversification of dogs from the Neolithic?

Later in the Neolithic period in Western Eurasia, people gradually opted for a sedentary and agriculturally oriented life. These changes in our way of life are likely to affect our dog sidekicks, making them even more different from their wild ancestors. In particular, prehistoric men were able to select morphologies that were adapted to perform certain tasks, such as hunting large games or defending camps and villages.

However, only a few studies have attempted to define the morphology of dogs from bone remains. For example, a Scottish study attempted to change the face from the skull of a dog dated about 4,500 years ago and found in a necropolis in the Cuween Hill region of Scotland’s Orkney archipelago. In reconstructed bones, whose size evokes our modern border collie, silicone and clay are used to rebuild a number of muscles. A skin was then added, the fur was chosen to commemorate the gray wolf of Europe. A similar reconstruction was done recently for an older dog, dated about 7,600 years ago.

Reconstruction of the face of a Neolithic dog about 4,500 years old.

Other studies, unfortunately scattered, have relied on measurements made of bones to describe the shape of these prehistoric dogs. This research emerged against the problem of conserving bone remains (cranial remains are rare and often very fragmented), aimed at small samples and limited the study to certain regions or periods, without intending to have a greater variability in European dogs on a prehistoric scale. In addition, the method used is usually very inefficient and does not make it possible to accurately describe the shape of the bones (preferably we have estimates of the strength or length of the fissures from the measurements. made of tall bones, and of size indications from measurements made of skeletal elements). Thus, to date, there are no studies that have accurately and reliably documented the morphological variability of dogs on the Prehistory and European scale.

In our study, we studied a sample of more than 500 lower jaws (mandibles) of European dogs dated from 11,100 to 5,000 years before our days, i.e. from Mesolithic to the beginning of the Bronze Age, when dogs were well distinguished from. wolves. We base ourselves on the mandible because it is the most frequent and best preserved bone in an archaeological context. In addition, the mandible remains a good indicator of the overall shape of the head and it can be used to provide a practical definition of the differences in the shapes observed. We can therefore estimate whether the masticatory muscles are more or less developed, and which are most active during biting.

We used 3D techniques to accurately describe the shape of these mandibles, i.e. the size and proportion within the bone. To quantify this innovation and compare it to our current dogs, we used a repository consisting of nearly a hundred modern dogs of different breeds or returned to the wild state ( Australian dingoes), as well as some wolves (modern and ancient).

The result of our study

Our study showed, for the first time, that at this very early age dogs already have a variety of head sizes and shapes. Prehistoric European dogs had mandibles that were the same size as some today’s medium-sized dogs such as the husky or golden retriever, or the same size as our beagles today, or even small dogs such as the Pomeranian (also called the dwarf spitz) or the dachshund. In any case, they all have smaller jaws than the smallest modern or archaeological wolves in our sample. We don’t find very large (like the modern Rottweiler or Borzois Greyhound for example) or very small (like Yorkies or Chihuahuas) sizes.

In terms of form, we also don’t recognize a serious form, so there is no equivalent to modified breeds like the Rottweiler, Borzoi Greyhound, French Bulldog, Dachshund or Chihuahua. Most dogs have a typical shape, similar to today’s beagles or other breeds such as the husky, but there are some variations with longer heads (mandibles similar to Sloughi’s or whippet sighthound, or Pomerania).

Morphological variability in European prehistoric dogs, from studies of the lower jaw. Prehistoric dogs showed great changes in the size (left) and shape (right) of the mandible, with shapes unmatched in modern dogs. We modeled the theoretical shape of the skull to correspond to these unique mandible shapes, making it possible to reconstruct the facial profile of these dogs with “missing” morphology. Wolves and dingoes are not represented here.
Armband Hill

If we expected this result and this lower variability in prehistoric dogs compared to modern dogs, we would not expect the next one we show. We emphasize that part of the innovation of prehistoric dogs seems to have no equivalent in our dogs today or among wolves. Which is surprising, since we made sure to include all possible types of morphology by integrating the extremes (small or large dogs with short or long muzzles, dogs with slightly modified cranial morphology such as beagles or dingoes). One might expect that prehistoric dogs would place themselves in a place of this diversity.

It is true that our modern sample was not complete at the time of the study, but since then we have done more analysis by adding stray dogs (with no particular selected morphology), and it appears that they are not enough. forms found in European prehistoric dogs. More than likely by adding dogs to the modern corpus, we have always made this observation. This leads us to wonder if certain forms will not disappear.

In addition, we know the anatomical peculiarities of prehistoric dogs compared to modern dogs, making it possible to identify them with certainty. These discriminatory behaviors can, among other things, illustrate the adaptation of dogs to choosing pressures related to their environment and their way of life. In fact, prehistoric European dogs had strong, arched jaws, suggesting that they used their temporal muscles more. One possible explanation is that they ate harder, harder to chew foods than our kibble-fed dogs. Another assumption is that it would have been useful for them to protect camps and villages or to help catch large game when hunting.

Finally, we show greater flexibility within the mandible in archaeological dogs: in modern dogs, the shape of the front of the jaw is strongly associated with the back of the jaw, due to developmental constraints, while it is less common in the prehistoric. dogs. This greater flexibility may allow dogs to quickly adapt to sudden changes in diet, for example.

In this study, we aimed to describe worldwide the morphological variability of European dogs in prehistory, by comparing them with modern dogs, without attempting to explain this variability or to follow the morphological evolution of dogs over time. in prehistory. . Future work is needed to interpret, with precision, how geographical and cultural differences (affecting the area given to dogs in societies or their diet) may have affected the morphology of our smoke allies in this time.

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