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 Molecular systematics indicate that the domestic dog (Canis familiaris) descends from one or more populations of wild wolves (Canis lupus). As reflected in the nomenclature, dogs are a subspecies of wolf and are thus still able to interbreed.
The relationship between man and canine has deep roots. Wolf remains have been found in association with hominid remains dating from 400,000 years ago. Converging archaeological and genetic evidence indicate a time of domestication in the late Upper Paleolithic close to the Pleistocene/Holocene boundary, between 17,000 and 14,000 years ago. Fossil bone morphologies and genetic analysis of current and ancient dog and wolf populations have not yet been able to conclusively determine whether all dogs descend from a single domestication event, or whether dogs were domesticated independently in more than one location. Domesticated dogs may have interbred with local populations of wild wolves on several occasions (so-called introgression).
The earliest dog fossils, two crania from Russia and a mandible from Germany, date from 13,000 to 17,000 years ago. Their likely ancestor is the large northern Holarctic wolf, Canis lupus lupus. Remains of smaller dogs from Mesolithic (Natufian) cave deposits in the Middle East, dated to around 12,000 years ago, have been interpreted as descendants of a lighter Southwest Asian wolf, Canis lupus arabs. Rock art and skeletal remains indicate that by 14,000 years ago, dogs were present from North Africa across Eurasia to North America. Dog burials at the Mesolithic cemetery of Svaerdborg in Denmark suggest that in ancient Europe dogs were valued companions.
Genetic analyses have so far yielded divergent results. Vilà, Savolainen, and colleagues (1997) concluded that dogs split off from wolves between 75,000 and 135,000 years ago, while a subsequent analysis by Savolainen et al. (2002) indicated a "common origin from a single gene pool for all dog populations" between 40,000 and 15,000 years ago in East Asia. Verginelli et al. (2005), however, suggest both sets of dates must be reevaluated in light of recent findings showing that poorly calibrated molecular clocks have systematically overestimated the age of geologically recent events. On balance, and in agreement with the archaeological evidence, 15,000 years ago is the most likely time for the wolf-dog divergence.
Verginelli examined ancient DNA evidence from five prehistoric Italian canids carbon-dated to between 15,000 and 3,000 years old, 341 wolves from several populations worldwide, and 547 purebred dogs. Their results indicate multiple independent origins of dogs and/or of frequent interbreeding between early proto-dogs and wolves throughout a vast geographic range. The detailed history remains unexplored and until further evidence is available, the following section on wolf ancestors must be considered purely speculative.
Wolf ancestors
Although all wolves belong to the species Canis lupus, there are (or were) many subspecies that had developed a distinctive appearance, social structure, and other traits. For example, the Japanese wolf and the Eastern Timber Wolf posses different distinctive colouration, hunting and social structures.
The Indian Wolf is thought to have contributed to the development of more breeds of dogs than other subspecies. Many of today's wild dogs, such as the dingo, the dhole and pariah dogs, are descended from this wolf.
The Indian wolf is also thought to have bred with descendants of the European wolf to create the Mastiffs and eventually leading to the development of such diverse breeds as the Pug, the Saint Bernard, and the Bloodhound. The Tibetan Mastiff is an example of an ancient breed.
The European wolf, in turn, may have contributed many of its attributes to the Spitz dog types, most terriers, and many of today's sheepdogs. The Chinese wolf is probably ancestor to the Pekingese and toy spaniels, although it is also probable that descendants of the Chinese and European wolves encountered each other over the millennia, contributing to many of the oriental toy breeds.
The Eastern Timber Wolf is a direct ancestor to most, if not all, of the North American northern sled dog types. This interbreeding still occurs with dogs living in the Arctic region, where the attributes of the wolf that enable survival in a hostile environment are valued by humans. Additionally, unintentional crossbreeding occurs simply because dogs and wolves live in the same environment. The general reproductive isolation which is required to define dogs and wolves as separate species is purely a result of lack of opportunity, stemming from a general mutual unfamiliarity, suspicion, mistrust, and fear.
The phenotypic characteristic that distinguish a wolf from a dog are tenuous. Wolves typically have a "brush tail" and erect ears. While some dog breeds possess one of these characteristics, they rarely possess both.
Speed of domestication
Current research indicates that domestication, or the attributes of a domesticated animal, can occur much more quickly than previously believed. Domestication of a wild dog may occur within one or two human generations with deliberate selective breeding. It is also now generally believed that initial domestication was not attained solely by human desire intervention but through mutual desire. Wild canines who scavenged around human habitations received more food than their more skittish or fearful counterparts. Canines who attacked people or their children were likely killed or driven away, while those more friendly animals survived. Canines would have been beneficial by chasing away other vermin or scavengers. The relationship is theorized to have developed in this way. |
