Introduction
The domestic dog is a member of the Canidae family. This is a biologically cohesive group of carnivores and consists of thirty-eight species (Serpell 10). thus far, man has managed to fully domesticate the dog (Canis familiaris) although he has also attempted to breed the raccoon dog (Nyctereutes procyonoides) and the red fox (Vulpes vulpes) in captivity for their fur (Klinghammer and Goodmann 36).
The current paper tries to show the link between the modern domesticated dog and the grey wolf using documented evidence from morphological, molecular, and DNA investigations.
Tracing the origin of the domesticated dog
In 1868, Darwin argued that the various domesticated varieties of the dog could have originated from several wild species or from a single wild species. A number of authors contend that the domesticated dog could have originated from the jackal, the wolf, or other unknown and extinct species (Serpell 10).
Darwin also suggested that it would be almost impossible to ascertain the origin of the domesticated dog. However, the combined results of vocalisation, morphological behavior and molecular biology of the domesticated dog now show that the wolf is the principle ancestor of the dog (Grandin and Johnson 87).
In the 1950s, Konrad Lorenz proposed that certain modern breeds of the dog could have been the descendants of the wolf, while others could have originated from the jackal. However, Lorenz soon realised that the jackal had a characteristic and complicated howling repertoire that is quite different from that of the wolf or dog.
This discovery made Lorenz to rescind his earlier view that the domestic dog could have been a descendant of the jackal (Serpell 11). Another hotly contested idea is the origin of the Australia dingo. Molecular and anatomical investigations indicate that the dingo may be categorized as a feral dog of ancient descent. In addition, these findings reveal close resemblance between the Australian dingo, the wolf, and the pariah dogs in South-east Asia.
What are the ‘precursors of the modern domesticated dog?
Bones belonging to wolves in the Middle Pleistocene period have been found alongside those of early hominida. This association is indicative of an overlapping of the hunting activities and occupation of wolves and humans. Human hunters may also have killed wolves occasionally for their skins which they used as clothing (Serpell 12).
Once in a while, human hunters would be accompanied by a live pup that they ended up eating but occasionally, such a pup would get accustomed to the family group, effectively becoming tamed. The wolf pups that turned out to be less submissive with maturity would undoubtedly be driven away or killed. Others that showed signs of submission were tamed by humans (Savolainen et al 1611).
Such tamed wolves are the precursors of the true domesticated dog, although they are many generations apart. Some remains of these animals that were discovered at late glacial sites reveal slight morphological differences in comparison with the remains of wild wolves.
Wolf skulls believed to belong to the last Ice Age have also been retrieved at Fairbanks, Alaska. This are thought to be approximately 10,000 years old. These wolf skulls are characterized by shortened facial regions and for this reason, they are thought to be the remains of tamed wolves. This information is supported by evidence of humans having crossed into North America via the Bering Straits around this time.
Theories of domestication of dogs from wolves
Although it is still not clear how the actual domestication of the Grey Wolf took place, nonetheless, a number of theories have been proposed on how the domestication process took place.
One such theory has to do with the orphaned wolf-cubs. Several studies have suggested that humans were able to tame and socialize some wolf pups that they took while still young. One study has also endeavoured to show that it is possible to socialize the adult wolves successfully (Koler-Matznick 99). In contrast, other scholars contend that socializing adult wolves can be time consuming especially when pups are more than 21 days old.
Many scientists are convinced that the early humans adopted orphaned wolf cubs and then proceeded to nurse them. Thereafter, the adopted wolves began to breed, in effect bringing forth “wolf-like” domesticated animals. As more generations of these “wolf-like” domesticated animals were born, they bore a lot of resemblance to dogs.
Another theory holds that the early wolves were scavengers and as such, they would often be attracted by the refuse that humans left behind at campsites. Some of these wolves proved quite successful in their ability to interact with humans and as a result, these traits were passed on to future generations.
Ultimately, there emerged a generation of wolves that had a tendency to be domesticated. Humans decided to keep those dogs that showed the least amount of fear and those that demonstrated high level of socialization. Consequently, the early dog developed unique traits that we can now recognize the modern day dog.
One of the behavioural characteristics of the gray wolf that made it easier for humans to domesticate them is what is known as “flight distance”. Flight distance is a measure of the level of closeness that an animal can allow something that it considers dangerous before deciding to run away.
If an animal has a shorter flight distance, it means that it is not scared by the presence of humans even when feeding. Such a behavioural trait might have been passed down to successive generations of the animals and over time it was amplified to the point that the animals felt comfortable in the presence of humans.
Ideally, wolves are believed to have separated into two populations. The first group was made up of a pack of hunters while the second group was made up of village-oriented scavengers. Although there are scanty details as to how the next steps evolved, however, sustaining these two divergent populations must have required the presence of selective pressure.
DNA evidence
Prior to the development of the DNA technology, scientists held two schools of thought regarding the origin of the domesticated dog. Most of the researchers assumed that the early dogs were the descendants of the tamed wolves and through interbreeding and evolving, this had resulted in a domesticated species.
We also have another school of thought that suggests that the modern dog is the distant descendant of the wolf. The same school of thought also believes that the jackal and the coyote could also have been distant relatives of the modern dog.
However, DNA evidence now points at the wolf as the sole ancestor of the domesticated dog. One scientist who has done a lot of DNA work on the ancestors of the domesticated dog is Carles Vila. Through his numerous studies, he has analyzed various types of wolf DNA from some 27 populations across North America, Europe and Asia (Vila et al 1687). He has also compared the results of his studies with DNA of some 67 breeds of modern dogs from various parts of the world.
DNA evidence has revealed the most diverse group of wolves possess similar sequences to the ones found in the most ancient breeds of the domesticated dog, including the dingo of Australia. The German Shepherd Dog was shown to share a close resemblance to wolf sequences, in comparison with the sequences of the main dog group (Vila et al 1688). This is a sign that such breeds may have been produced by crossing wild wolves with dogs.
Conclusion
Over the years, a lot of research has been carried out on the origin of the domesticated dog, with scientists divided into two schools of through. The first and largest school of through believed that dogs could have been the descendants of the gray wolf. Other scientists suggested that the older domesticated dog could have been the descendant of the red fox, or even the raccoon.
However, there is now compelling evidence to suggest that the early humans most likely domesticated the modern dog from the gray wolf. This assertion has been supported by molecular, morphological and DNA evidence that point at a closer relationship between the domesticated dog, and the gray wolf, more than the red fox and the raccoon.
However, because the origins of some of the morphological differences between wolves and dogs are still not clear, there is need to undertake more DNA studies. Such studies also need to be supplemented by a re-evaluation of canidae fossil and archaeological records so that we can resolve the many questions regarding one of man’s ancient domesticated animal.
Works Cited
Grandin, Temple and Catherine, Johnson. Animals in translation, New York, NY: Scriber, 2005. Print.
Klinghammer, Erich and Goodmann, Patricia. “Chapter 2: Socialization and management of wolves in captivity”. In Frank, Harry. Man and Wolf: Advances, Issues, and Problems in Captive Wolf Research. The Hague, The Netherlands: Dr W. Junk Publishers, 1987. Print.
Koler-Matznick, Janice. The origin of the dog revisited. Anthrozoos, 15.2(2002):98–118. Print.
Savolainen, Peter, Zhang, Jing, Luo, Joakim Lundeberg, and Thomas Leitner. “Genetic
Evidence for an East Asian Origin of Domestic Dogs”. Science, 298. 5598(2002): 1610–1613. Print.
Serpell, James. The domestic dog: its evolution, behavior, and interactions with people. Cambridge, Mass: Cambridge University Press, 1995. Print.
Vila, Carles, Peter, Savolainen, Jesus, Maldonado, John, Rice and Rodney, Honeycutt.
Multiple and ancient origins of the domestic dog. Science, 276.5397(1997): 1687-1689. Print.