It is by now generally accepted that the dog is a wolf modified through 15,000 or more years of sometimes intensive breeding to live in human society. In Darwin's terms, the dog is a product of artificial selection, or "selection under domestication," while the wild wolf is subject to the laws of natural selection. Much about the origin and early development of the dog — the first domesticated animal — remains a mystery, with scientists still puzzling over how, when, where and why wolves and people first got together. Was it the dog's prowess in the hunt, its alertness as a camp guard, its companionship or a combination of those and other qualities that made it so valuable? Did the dog have religious significance as a guardian and guide for the dead? Did wolf become dog in the Middle East, East China, Europe or all of them? Was it 15,000 or 40,000 or 135,000 years ago that the transformation occurred?
|My dad with schnauzer pups he helped whelp as a kid. |
He is now devoted to Tibetan Terriers.
In recent years, scientists around the world have engaged in spirited debate over these questions, their research aided by sequencing of the dog genome in 2005. That has allowed researchers to examine the evolutionary history of the dog and probe the genetic relationships within and between breeds of dogs. Researchers are also able to use purebred dogs with their array of inherited diseases and extensive pedigrees to search for the genetic roots of diseases common to dogs and humans.
Relying on the most comprehensive and largest survey to date of dogs and wolves, the most recent study by an international group of scientists places the origins of the dog in the Middle East, where cats and livestock were later domesticated and where agriculture began. Led by Bridgett M. vonHoldt and Robert K. Wayne of the University of California, Los Angeles, the international team analyzed 48,000 glitches or single letter changes in long stretches of DNA, called single-nucleotide polymorphisms, SNPs, and pronounced "sn`populations. They looked for matches in those haplotypes, as they are known, indicating genetic relationships.
The survey showed that dogs were closest genetically to Middle Eastern wolves, but that for a short period of time after domestication, dogs apparently were bred to wolves from other areas, perhaps as they migrated with people into previously unoccupied lands where there were no dogs. Without fixing a date for the transformation of wolf to dog, the researchers observed that their findings were consistent with an archaeological record that locates early dogs in Goyet Cave in Belgium, 31,7000 years ago; western Russia, 15,000 years ago; Germany,14,000 years ago; and the Middle East,12,000 years ago.
The researchers also identified genetic sequences shared by dogs within specific breeds that could be used to examine their development through the formation of modern breeds beginning in the late 18th century. To their surprise, breeds with similar phenotypes and functions grouped together, indicating a shared genetic heritage for herding dogs, mastiff-like dogs, sight hounds, scent hounds, small terriers, spaniels, toy dogs, retrievers, working dogs and a group containing ancient and spitz-like dogs.
The survey by Dr. Wayne, Dr. vonHoldt and their collaborators was published just months after a 2009 study suggesting that dog domestication occurred in Eastern China, south of the Yangtze River, less than 16,000 years ago. These dogs were probably initially raised as food, reported Peter Savolainen of the Royal Institute of Technology in Stockholm. He argued that the dog resulted from a single domestication event and then quickly spread with people around the world. Dr. Savolainen and his team studied mitochondrial DNA, inherited only from the mother, while Dr. Wayne's team surveyed the entire genome, a more comprehensive approach because it includes contributions from both parents.
More on dogs from The New York Times soon.