Dogs Domesticated Twice in Two Places
New evidence reveals that dogs were first domesticated in two separate regions and from two different wolf populations.
Dogs were domesticated not just once but twice, and in two different parts of the world, finds new research with implications affecting both the history of dogs and humans.
For years, researchers have been trying to answer the question, "Where do dogs come from?" with some claiming that dogs were domesticated in Europe, while others concluded that dogs were domesticated in Asia. According to the new study, published in the journal Science, both locations are correct.
Lead author Laurent Frantz of the Wellcome Trust Paleogenomics & Bio-Archaeology Research Network at the University of Oxford told Discovery News that "two groups of humans came to the same conclusion that wolves can be domesticated." As a result, "all modern dogs are directly related to two or more wolf populations."
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At the center of the research was a 4,800-year-old inner ear bone from a dog that once lived at Newgrange, Ireland. It is the hardest bone in the body of any mammal. The scientists sequenced the dog's genome via this sturdy bone.
"We have found that this bone is the best preserver of ancient DNA in many studies -- a sort of DNA time capsule -- and, sure enough, this particular animal turned out to be the best preserved of any bone we have encountered in hundreds of experiments," co-senior author Daniel Bradley of Trinity College Dublin told Discovery News.
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The researchers obtained mitochondrial DNA -- a type of DNA that is maternally inherited -- from 59 ancient dogs that lived between 14,000 to 3,000 years ago. They then compared all of the data with the genetic signatures of more than 2500 previously studied modern dogs.
Their analysis uncovered a genetic split between modern dog populations now living in Europe and East Asia. The divide seems to have happened after the earliest archaeological evidence for dogs in Europe.
The new genetic evidence also shows that there was a population turnover in Europe, where a smaller, existing dog population was mostly replaced by another bunch of dogs. The researchers think this happened when large groups of people migrated from Asia to Europe, bringing their dogs with them. Probably because of this influx, most dogs today are a mixture of both Eastern and Western dogs, helping to explain the earlier confusion over where dogs originated.
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A review of the archaeological record additionally shows that early dogs appear in both the East and the West more than 12,000 years ago, but in Central Asia no earlier than 8,000 years ago.
"Dogs were domesticated by hunter gatherers, prior to the advent of agriculture," Frantz said. "Dogs most likely provided multiple services to humans, such as facilitating hunting or providing protection."
The researchers can't yet rule out that Neanderthals or some other ancient human first domesticated dogs. Other research teams have found remains for possible dogs going back to the Neanderthal era.
Frantz said that he and his team are currently studying early dogs and wolves using techniques such as 3D scanning to better analyze their features. He explained, "This will allow us to compare wolves at that time with specimens we think may be dogs and to estimate a more accurate time for domestication."
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As for the two or more wolf populations from which dogs first arose, it is possible that they have since gone extinct. The researchers don't think that these wolves were separate species in the biological sense, but were still genetically distinct because they evolved in different regions.
Today's dogs run the gamut from tiny Chihuahuas to large great danes, but they are all still related to the two or more founding wolf populations, according to the researchers.
Africa has native wolves, such as the African golden wolf and the Ethiopian wolf, but Frantz said, "There is no evidence that native African wolves have been domesticated. They may, however, have played a role in the genetic make-up of modern African dogs through interbreeding."
Given the proposed dual East-West origin for dogs, it appears that domestication of man's best friend was very appealing to early humans.
Peter Savolainen, a geneticist at the Royal Institute of Technology, also told David Grimm of Science that if domestication "happened twice, maybe it wasn't as hard as we thought."
The Greenland sled dog, also sometimes referred to as a sledge dog, is yet another early East Asian breed. The recent DNA analysis conducted by Bogdanowicz and his colleagues "revealed post-divergence gene flow from grey wolves to Greenland sledge dogs," they wrote. This determination reminds that free-breeding dogs can still interbreed with wild canines, such as grey wolves, coyotes and golden jackals. The resulting offspring can be fertile, and conservationists are concerned that we may one day lose the uniqueness of wild canine species due to hybridization.
Basenjis look remarkably like dogs featured in ancient Egyptian art. Drawings found in the tombs of the 2700 B.C. Great Pyramid of Khufu show such dogs seated near the feet of their owners, or under chairs. The cat-loving Egyptians might have taken to the dogs because, like felines, these canines tend to be relatively quiet and wash themselves regularly with their tongues. Most researchers, including Bogdanowicz and his team, still believe that domesticated dogs largely arose in Asia and migrated to other regions. "It is very likely that migrating populations of early farmers were followed by dogs," he said, explaining that these dogs were not feral, but were originally free-breeding. Basenjis possess a very distinctive suite of characteristics, which must have been maintained by human breeders. While the official breed only dates back 60 years, these dogs clearly have been in existence for centuries.
Nearly all DNA studies of dogs find that Arctic breeds, such as the Alaskan malamute, stand apart from modern breeds. An extensive genomic investigation conducted by senior author Robert Wayne from the University of California at Los Angeles and colleagues found that Alaskan malamutes, as well as American Eskimo dogs and Siberian huskies, "are highly divergent from other dog breeds." This means that they have evolved on a slightly different path than other, more modern dogs. Wayne and his team added that "historical information suggests that most have ancient origins, greater than 500 years ago."
"Saluki" is thought to derive from two early Sumerian words meaning "plunge-earth." What that means exactly, in reference to the dogs, remains a mystery, but it is known that Salukis were historically bred in the Fertile Crescent where agriculture is widely believed to have originated. Like Afghan hounds, Salukis tend to have long legs and a thin build. They are known as sight hounds, meaning that they hunt primarily by sight as opposed to by smell or other senses. Today, they are bred with coats in a veritable rainbow of colors ranging from red to tricolor (white, black and tan).
DNA analysis, as well as historical information, is helping to reveal the world's most ancient dog breeds. A new study, published in the journal Proceedings of the Royal Society B, puts the spotlight on East Asia as being a primary origination point for dog domestication. The earliest known dog-like fossils come from Europe, but it is likely that these dogs did not produce large populations that led to distinctive breeds. Genetic research on existing dogs reveal that certain breeds stand apart from others. "Our results show that these breeds represent lineages older than modern European breeds, and in this sense can be considered as ancient," senior author Wiesław Bogdanowicz of the Polish Academy of Science's Museum and Institute of Zoology, told Discovery News. Afghan hounds fall into the ancient group. In fact, they were called "ancient" long before the advent of genomics. In 1925, an article published in "The Dog Fancier" had the declarative title: "The Afghan Hound Is an Ancient Breed." Canine experts at the time even thought that the dogs "entered the ark with Noah" and were the world's first ever dogs. According to the historical record, Afghan hounds date back to the pre-Christian era of northeastern Afghanistan. The original name for the breed, famous for its silken coat and fashion model thin build, was "Tazi."
Wayne and his team found that only two East Asian breeds, the chow chow and Akita, "had higher (genomic) sharing with Chinese wolves" than other breeds. Researchers can therefore see past wolf contributions to the modern dog genome. Other wolf populations noted in the dog DNA studies include those from North America, the Middle East and Europe.
The Samoyed, as a distinctive breed, originated in Siberia, where nomadic reindeer herders bred them as sled dogs and to help with herding. Their historical past is much deeper, however, as these primitive dogs descend from an even earlier, founding population of Russian dogs. According to an American Kennel Club fact sheet, "Of all modern breeds, the Samoyed is most nearly akin to the primitive dog. No admixture of wolf or fox runs in the Samoyed strain."
The genetic analysis of Wayne and his team defined three basic groups of "highly divergent, ancient breeds." They are: *Asian group: dingo, New Guinea singing dog, chow chow, Akita and Chinese Shar Pei *Middle Eastern group: Afghan hound and Saluki *Northern group: Alaskan malamute and Siberian husky All of these dogs were found to be genetically "distinct from modern domestic dogs."
Bogdanowicz and colleagues' study suggests that the Shiba Inu belongs on the ancient dog list. The DNA of this dog shows that it is related to yet another East Asian breed, the Chinese Shar Pei. The American Kennel Club, though, reports that "Shibas are considered the oldest and smallest of Japan's dogs." The AKC only officially recognized this breed in 1992, demonstrating that the actual origin of a breed can happen hundreds of years prior to such designations.
The word "spitz" refers to several different breeds that loosely share common ancestry and traits. They are believed to descend from very ancient dog populations. Bogdanowicz told Discovery News that he and his team "found that spitz-type breeds of European origin -- Keeshond, Elkhound, Finnish Spitz, German spitz and Schipperke -- are genetically distinct from other European dog breeds, suggesting that they may have a distinct origin and possibly may be related to spitz-type breeds from East Asia and the Arctic." A closer look at the friendly dog shown in this photo reveals many wolf-like characteristics, such as a dense and waterproof insulating coat. Dog breeders even categorize spitzes in a unique group that stands apart from the other umbrella terms that they often use to describe dogs: ancient, toy, spaniels, scent hounds, working dogs, mastiff-like breeds, small terriers, retrievers, herding and sight hounds. The spitzes are in a league of their own.