From prehistoric times, there were many different dogs

From Chihuahua to St. Bernard to Barzoi Greyhounds with incredibly elongated skulls, dogs today have an exceptional variety of shapes, while all descend from the same ancestor, the Gray Wolf. This strong variability is not very recent, then it is in the intensive selections meant for the last 200 years for the creation of 355 races today recognized by the Fédération cynologique internationale.

But what do we know about the appearance of the first dogs in prehistory? C’est la question sur où nous suntem penchés in this article published on May 18 in the scientific journal Proceedings of the Royal Society B.

The same ancestor

All dogs come from the same ancestor: the gray wolf. At least 15,000 years ago, in the Upper Paleolithic (the exact date and place of domestication remain debatable), fearless and aggressive wolves belonging to a now extinct lineage would have been dressed by human encampments, probably for profit from leftover food.

Prehistoric humans will then be brought closer to these wolves, who will help them hunt or protect their encampments from attacks by other predators. We would have tamed the less savage of them, making them reproduce and thus domesticating them over time.

At domestication it would have been modified in the anatomy of the facial muscles, to allow to allow the raising of the eyebrows.

This domestication is accompanied by numerous genetic, physiological, behavioral and physical changes, most of which are involuntary. Among the morphological changes, archaeozoologists (experts in human-animal relations in the past) and paleogenetics have noted variations in coat color, a decrease in size, less marked differences between males and females, and the preservation of characters. rather juvenile – which results in changes in the size of the skull with a strongly marked and shortened snout and more frequent dental abnormalities (absence or rotation of some teeth) due to lack of space.

In fact, a study conducted since the 1960s in Siberia showed that by selecting the most curious and least aggressive foxes over the generations (thereby recreating the hypothetical conditions of the first rapprochement between humans and wolves), animals became more and more docile, their stress rate (appreciated by the secretion of cortisol) decreased, and they had the same morphological differences as those observed by archaeozoologists during the passage from wolf to dog. At domestication it would have been modified in the anatomy of the facial muscles, to allow to allow the raising of the eyebrows.

A diversification of dogs since the Neolithic?

Later in the Neolithic, in western Eurasia, humans gradually opted for a sedentary, agricultural-oriented lifestyle. These changes in our lifestyle most likely affected our canine sidekicks, making them even more different from their wild ancestor. Les hommes préhistoriques, in particular, can select morphologies adapted to perform certain tasks, such as chasse au grand gibier or defending campements et des villages.

However, only a few studies have attempted to describe the morphology of dogs from bone remains. For example, a Scottish study attempted a facial reconstruction from a dog’s skull about 4,500 years ago and found in a necropolis in the Cuween Hill area on the Scottish Orkney archipelago. On the reconstituted bones, the size of which evokes our modern border collie, silicone and clay were used to rebuild muscle volume. A skin was then added, the fur being chosen to resemble the European Gray Wolf. A similar reconstruction was recent for an even older dog, dating to about 7,600 years ago.

Other studies, unfortunately scattered, are based on measurements made on the bones to describe the shape of these prehistoric dogs. This research addresses the issue of bone preservation (cranial remains are rare and often highly fragmented), refers to small samples, and is limited to the study of certain regions or periods, without seeking a more holistic approach. of the variability of dogs in Europe on a prehistoric scale.

In addition, the method used is generally very rudimentary and does not accurately describe the shape of the bones (we have the best estimates of strength or height at the withers from measurements made on long bones, etc. indications of size from measurements made on the elements of the skull). Thus, to date, no studies have accurately and reliably documented the morphological variability of dogs across prehistory and Europe.

In our study, we have a sample of more than 500 lower jaws (jaws) of European dogs dating from 11,100 to 5,000 years ago, from the Mesolithic to the very beginning of the Bronze Age, when dogs were already well differentiated. wolves. We are based on the mandible because it is the most common and best preserved bone in an archaeological context.

Most dogs had a medium conformation, similar to current beagles or other breeds such as the husky.

In addition, the mandible remains a good indicator of the general shape of the head and they can be used to give a functional meaning to the variations of shapes observed. It can therefore be estimated whether the masticatory muscles were more or less developed, and this acted most during the bite.

We used 3D methods to accurately write the shape of these mandibles, that is, the size and proportions within the bone. To quantify this variability and compare it to that of our current dogs, we used a repository consisting of a hundred modern dogs of various breeds or returned to the wild (Australian dingos), as well as a few modern wolves. various breeds). elders).

The results of our study

Our study showed, for the first time, that at this very old time dogs already had a wide variety of head sizes and shapes. Prehistoric European dogs have either jaws the size of some of today’s medium-sized dogs such as the husky or the golden retriever, or the size of our current beagles, or even small dogs such as the Pomeranian loulou (also called spitz). dwarf) or dachshund.

In any case, they all had significantly smaller jaws than the smallest of the modern or archeological wolves in our sample. We didn’t find them extremely large (like modern rottweilers or barzo greyhounds, for example) or extremely small (like yorkshire or chihuahua).

In terms of shape, too, we have not identified an extreme form, so no equivalent to the highly modified breeds such as the rottweiler, the greyhound, the French bulldog, the dachshund or the chihuahua. Most dogs had a medium conformation, similar to current beagles or other breeds such as the husky, but there was some variability with longer heads (jaws resembling those of sloughi or whippet greyhounds, or loulous Pomeranian).

Morphological variability of prehistoric European dogs, from the study of the lower jaw. Prehistoric dogs show great variability in mandible size (left) and shape (right), with shapes unmatched among modern dogs. We modeled the theoretical shape of the skull corresponding to these unique mandible shapes, which makes it possible to reconstruct the facial profile of these dogs with the “missing” morphology. Les loups et dingos are not represented here. | Brassard Hills

If we expected this result and the slightest variability of prehistoric dogs in relation to modern dogs, we did not expect what we then demonstrated.

We found that some of the variability in prehistoric dogs did not appear to have an equivalent among our current dogs or wolves. This is surprising, given that we have made sure to include all possible types of morphology by integrating the extremes (small or large dogs with short or long snout, dogs with a slightly altered skull morphology such as beagles or the dingos). So prehistoric dogs could have been expected to position themselves somewhere in this variability.

Prehistoric European dogs have sturdy, arched jaws, suggesting that they used their temporalis muscle more.

It is true that our modern sample was not exhaustive at the time of the study, but we have since performed additional analyzes by adding stray dogs (without particularly selectional morphology), if it turns out that they are not enough. to explain these unique forms observed in prehistoric European dogs. It is more than likely that when adding dogs to the modern corpus, this is always the case. This leads us to wonder if certain forms would not have disappeared.

In addition, we have identified anatomical features in prehistoric dogs compared to modern dogs, which you can certainly recognize. These discriminating traits may, among other things, illustrate the adaptation of dogs to selection pressures related to their environment and lifestyle. Indeed, prehistoric European dogs have sturdy, arched jaws, suggesting that they used their temporalis muscle more.

One possible explanation is that they ate harder, harder to chew food than our croquette-fed dogs. Another hypothesis is that it would have been useful to them to defend the camps and villages or to help catch large game while hunting.

Finally, we have shown greater flexibility within the mandible of archaeological dogs: in modern dogs, the shape of the front of the jaw is strongly related to that of the back of the jaw, due to developmental constraints. , while this is less the case with prehistoric dogs. This increased flexibility could allow dogs to adapt more easily to sudden changes in diet, for example.

In this study, we aimed to describe very globally the morphological variability of European dogs in prehistory, comparing them to current dogs, without seeking to explain this variability or to follow the morphological evolution of dogs in the course of prehistory. . Future work will need to decipher, rigorously, how geographical and cultural differences (affecting the place given to dogs in societies or their diets) may have impacted the morphology of our canine allies at this time.

This article is published by The Conversation under a Creative Commons license. Read the original article.

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