The Evolution of the Domestic Dog

The precise evolutionary path of the domestic dog has been the source of much debate. With the advent of molecular biology techniques it has become possible to determine ancestry in a more accurate manner though the exact process of domestication still remains unclear. The genus Canidae includes some thirty-eight species of which the dog is the only member which can be considered to be truly domesticated. Extensive studies by many researchers, including Scott and Fuller (1965), Hall and Sharp (1978) and Wayne, et al (1989, 1991), on wide-ranging topics such as behaviour and molecular biology have effectively identified the wolf (Canis lupus) as the true ancestor of the domestic dog. The earliest records of the wolf could date back as far as 400,000 years ago, from remains found at Boxgrove in Kent (UK). Various references have been made to find which may be indicative of a domesticated dog. These include bones which have been found in direct contact with hominid remains. The earliest such find was that of a jaw bone at the site of a Paleolithic grave in Oberkassel (Germany) which dates back around 14,000 years. These finds coincide with a probable change in hunting techniques by early humans (early Neolithic) where there was a transition from hunting with stone axes and other weapons requiring direct contact with prey animals, to the widespread use of arrows. This shift in hunting method would have been facilitated by the use of dogs to retrieve the wounded animals. The Neolithic hominids (literally ‘new’ Stone Age) first appeared at Levant (now Jericho) in roughly 8500 BCE (before Common Era) and developed from the Natufian people. It was the Natufians who provided the most conclusive evidence of a domesticated dog; the discovery of a human buried alongside and touching a young dog (Davis & Valla, 1978). This and other archaeological data have proved that the dog was the first animal to be domesticated and that this occurred towards the end of the last Ice Age. Several theories exist as to the domestication process itself, some of these theories will be examined now.
The study of dog remains from various sites around the World implies that there may have been several different stages of domestication taking place over a variety of different times. All domestic dogs though would seem to have originated from wolves. The first possibility is the hunting, killing and eating of adult wolves by human populations. These kills would also have provided fur for clothing and domestic use. It is possible that any resulting orphan wolf pups would have been captured by the human hunters and tamed, possibly as a future source of meat and fur. Over a number of generations these animals would have become physically different to their ancestors. There is archaeological evidence which supports this element of the theory; changes in diet and environment, combined with breeding within a smaller population meant that physical features such as overall size and the size and shape of the animal’s head, distinguished those ‘domesticated’ animals from their relatives in the wild. Selective pressure would take place in favour of these smaller dogs meaning that they would be more able to survive with less food (Serpell, 1995). The various finds of dog skull fragments at periods throughout history offers irrefutable evidence that there was a difference between the early domesticated wolves and those remaining in the wild. Such finds have been recorded from Ein Mallaha and Hayonim cave in Israel. Unfortunately though they do not offer any clues as to exactly how this process took place and of course there was the disadvantage that any captured pups would have placed a burden upon the associated human populations, because they needed to be fed and sheltered.
Another possible explanation of the domestication process is the gradual move of the weaker, ‘lower-ranked’ wolves from the wild pack to the human encampments. This may have happened while the wolves were foraging for food amongst items discarded by humans. Such animals would have been smaller and less able to fend for themselves or to take part in the hunt with the rest of their pack. Displaced individuals would possibly befriend humans and form part of a symbiotic relationship, where they would aid in hunting and security and would in turn be fed and sheltered. These wolves were already subservient and would therefore have been more likely to have a more docile temperament thus making them easier to handle and tame. In this way the humans were able to train them to assist with tracking and retrieving prey.
The third possible explanation of domestication is the theory that wolf packs became involved with humans when they hunted together. This is more unlikely due to the fact that the wolves would have been too nervous and wary of the humans. This type of relationship may have occurred with the Aborigines and the dingoes in Australia. This, more recent interaction between humans and wild dogs was described in detail by Meggitt in 1965. Dingoes were used as hunting companions and were given affection by the Aborigines. However they were also a source of food, if needed, when meat was scarce.
There is little doubt that the relationship between humans and the domestic dog has origins which have been established over a very long period of time. Early populations have provided evidence that the two have shared shelter and food. Initially there was much debate as to the ancestry of the dog we know today and until the time of Charles Darwin, both wolves and jackals were thought to form part of that heritage. It was not until the more recent advent of molecular biological techniques, in particular comparison studies involving mitochondrial DNA, that it has become possible to pinpoint the exact lineage of the dog (Wayne 1991). Although it is now clear that all domestic dogs share a common wolf ancestor, there remains some debate as to the exact mechanism of the domestication process.