Sitting comfortably on your couch, you watch your dog sleep peacefully next to you. Is he dreaming about his last bowl of croquettes? Or is he perhaps imagining the great Odyssean saga of his ancestors, where he roams the vast steppes of the last ice age in herds in search of the reindeer that would be their next meal?
The story of the ancestral connection between the dog (the first animal to be domesticated) and the wolf is one of the most exciting evolutionary adventures in human history. It not only makes us question the relationship we have with the rest of nature, but it also, by extension, sends us back to the question of everything we are as humans.
Recent advances in genetics are beginning to provide key details that allow us to sketch the related history of our loyal housemates and the proud wild dogs that are gradually repopulating our landscape.
Originally was the wolf
Today, the dog (Canis familiaris) is the most widespread carnivore on the planet. It has been part of our human adventure since the time when we were still nomadic hunter-gatherers, 20,000 or even 30,000 years before the invention of agriculture.
There are almost 350 official dog breeds in the world and today there are almost 7 million in French homes. If its faithful presence by our side has long been taken for granted, the dog is nevertheless a relatively new element in human evolution.
But the history and chronology of the domestication of the dog turns out to be very complex and fuels the scientific debates as much as myths or other beliefs in our society. When asked “what animal does the dog come from?” most adults and children will answer without hesitation: “The wolf, of course!” Yes, but now, which wolf are we talking about here?
The gray wolf (Canis lupus) is an apex predator found throughout the Northern Hemisphere. In other words, the wolf is a species that is at the top of the food chain, that has no real natural predators, and that regulates the balance of its ecosystem through predation. Its origins are nebulous but certainly very ancient, probably dating back about 800,000 years. The Lupidae are genetically very diverse, and almost forty current subspecies have already been described.
Despite habitat and ecological niche limitations created by humans since prehistoric times, wolves are among the only large carnivores to have survived the mass extinction of the late Pleistocene (between 50,000 and 10,000 years ago). And this, especially thanks to their great ecological resilience and the flexibility of their predatory behavior.
Over the last two centuries, the indirect pressure of urbanization as well as the numerous extermination campaigns have led to an almost complete disappearance of its wild forms in Europe. But in recent years, its presence is slowly recovering thanks to conservation programs. The gray wolf is currently reintroduced in our European countries along with three other species of carnivores: the brown bear, the boreal lynx and the wolverine.
Between dog and wolf
The timeline of prehistoric wolf domestication is probably one of the most heated debates in evolutionary science. If paleontology obviously brings important components to this debate, osteomorphological analyzes (the study of the size and morphology of bones), which are able to distinguish proto-dogs, are still difficult to identify.
Since the work of Charles Darwin, we know that a series of phenotypic changes (observable physical characteristics) are observed in animals undergoing a domestication process, at least after many generations of carefully selected traits (often favoring the most docile). Over the millennia, for example, domesticated canines have seen a reduction in the length of their snout and the size of their teeth, but also a reduction in their appendicular skeleton (fore and hind limbs).
On the other hand, the isolated appearance of only one of these features on a specimen cannot prove its domesticity. Therefore, either a series of significant variables must be observed on the same individual, or this new trait must be observed repeatedly on the scale of a given population or context. The problem is that complete skeletons of Paleolithic dogs are extremely rare.
In addition to this purely osteological approach, archeology thus comes into play to strive to gather any information about the first direct relations between humans and dogs. These traces could demonstrate a special connection that began to be woven between these two types of large predators from the Upper Paleolithic (for example, we note the use of canines to make jewelry or its presence in parietal art). But there again it is difficult to understand the real meaning of these meager indications.
Is the wolf really the ancestor of the modern dog?
With the great advances that genetics has seen in recent years, many studies of ancient DNA are now going to lend a hand to paleontologists and archaeologists trying to unravel the mystery of the origin of the “first dog.” Samples of ancient and modern dogs are now taken from all continents and the diversity of their genetic heritage is analyzed.
The main advantage of this method is significant: there is no need for perfectly preserved skeletons to obtain essential information, a simple bone fragment is enough. While the majority of these studies focus on mitochondrial DNA (DNA inherited only from the maternal line, but less prone to degradation), some, more rare, also relate to the complete genome (therefore on the chromosomes inherited from the maternal and the paternal line, but which is preserved much worse during fossilization).
Thanks to these findings, a framework for the global phylogenetic history of canids is beginning to take shape. And not surprisingly, these analyzes reveal a very complex demographic and phylogenetic history of the gray wolf through time. In particular, they reveal that the Paleolithic lupine populations had to adapt both to the changing geography of successive glacial events in Eurasia, but also to the human presence, which constantly changed their habitat.
These environmental and ecological changes during the Quaternary led to cycles of expansion/retraction of their populations, likely significant demographic fluctuations, and various fragmentations of their gene pool.
Far from being divided, the co-evolution of canids has never stopped. Even today, the wolf is the subject of hybridizations with other canids such as the dog or the coyote.
Despite this, the information from these analyzes is extremely exciting. The genetic divergence (i.e., the separation of a population into several different lineages) of modern Eurasian wolves is now estimated to have occurred about 40,000 to 20,000 years ago. This would mean that the population of these Paleolithic wolves was highly fragmented during this period, which also corresponds to the Last Glacial Maximum (in other words, the peak of the Ice Age).
This date is all the more interesting as it coincides with the period when our Homo sapiens ancestors migrated from the East and colonized Western Europe, and when interspecific competition between large carnivores increased sharply.
More interestingly, several studies agree that all modern Eurasian wolves are descended from a single, small ancestral population that probably became isolated in Beringia (between eastern Siberia and Alaska) during the last ice age about 20,000 years ago, mainly to escape the major climatic instabilities prevailing in the rest of Eurasia.
This drastic bottleneck would have given rise to a new genus, which would have then recolonized the rest of the world. This replacement of the lupine population would probably have occurred at the expense of other forms of ancient wolves, then adapted to other forms of environment elsewhere in Eurasia. This is why it seems that all wolves today have a relatively “recent” common ancestor, or at least no older than the beginning of the Upper Paleolithic, about 36,000 years ago.
Origin between Asia and Europe
But the story thickens with the question of the appearance of domestic dogs. The Eurasian gray wolf’s complex history stands in the way of our quest to trace the dog’s exact origins. Nevertheless, studies provide some key answers. A study of complete genome sequences of primitive Asian and African dogs, along with a collection of samples from nineteen different dog breeds from around the world, identified that Asian dogs from the East have a genetic diversity far superior to the others.
This modeling would show that the first dogs appeared in this region, after a divergence between the gray wolf and the domestic dog around 33,000 years ago. But another genetic study argued in 2013 that the focus of domestication would rather have been Europe, somewhere between 32,000 and 19,000 years before the present.
Finally, a third study that reconciles the first two hypotheses suggests that the domestication of the wolf occurred independently in East Asia and in Europe. Before primitive Asian dogs traveled west with human populations, where they would have replaced the native dog population between 14,000 and 6,400 years before the present.
Regardless of the hypothesis, we can remember that when we see the first traces of sedentarization and the first techniques related to agriculture appear around 11,000 years ago, there were already at least five different genera of dogs, which shows that human societies had already changed dogs deep. populations before the end of the Paleolithic.
And far from being divided, the co-evolution of canids has never stopped. Even today, the wolf continues to be the subject of hybridizations with other canids such as dogs, but also the coyote (Canis latrans), with which it is also interfertile.
In conclusion, although the determination of the geographic origin of the domestic dog and the circumstances and chronology of its domestication still remain unresolved, advances in the study of ancient DNA now provide us with the means to follow the traces entangled in these past and present dogs . .
To the question “Do dogs descend from wolves?”, the answer is yes. But genetics today offers us the means to clarify: Modern dogs, as varied as they are, all descend from a now-extinct line of prehistoric wolves. And they would ultimately have only very distant connections with the modern wolf.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
