Dogs and Humans Bonded Earlier Than Thought
Two modern dog breeds share DNA with a prehistoric Siberian wolf, suggesting that the ancestry of today’s dogs runs much deeper than previously thought.
New DNA evidence from a wolf bone suggests humans and dogs were companions for much longer than previously thought.
Modern Siberian huskies and Greenland dogs turn out to share an unusually large number of genes with a wolf that lived 35,000 years ago -- a time when our species was just beginning to populate Europe and Asia, reports the Current Biology study.
This animal, the Taimyr wolf of Siberia, is the most recent common ancestor of modern wolves and dogs.
"We find that the ancestors of domestic dogs must have separated from the ancestors of wolves at least 27,000 years ago," lead author Pontus Skoglund, a Harvard University geneticist, told Discovery News.
"As for the genetic link between the 35,000-year-old wolf and Husky-type dogs, the most natural explanation is that these dog breeds absorbed local wolf ancestry that still lived on in Siberia when they followed early human groups to this region," he said. "This is the first direct evidence we have that the diversity in common dog breeds today has such deep roots."
It's likely that many other dog breeds today are also related to prehistoric regional gray wolf populations, helping to explain why there is such incredible diversity among dogs, from Golden retrievers to poodles, due to factors beyond humans selecting for certain traits.
Skoglund and his colleagues made the discoveries after analyzing a small bone picked up during an expedition to the Taimyr Peninsula in Siberia. DNA tests revealed that the bone belonged to the prehistoric Taimyr wolf.
The direct dating of the wolf bone, combined with further genetic analysis, enabled the researchers to recalibrate the molecular timescale of wolves and dogs. This found that the mutation rate between the two is substantially slower than assumed by most prior studies, suggesting that the ancestors of dogs were separated from present-day wolves around 27,000 years ago.
Senior author Love Dalén of the Swedish Museum of Natural History told Discovery News that some of the debate over when dogs were "domesticated" hinges on the precise meaning of that word. If it is taken to mean a fully tame dog that doesn't look much like a wolf, then that happened much later.
"But if 'being domesticated' means an animal population that is held and breeds in captivity, then our results are consistent with dogs being domesticated at least 27,000 years ago," Dalén said.
Based on the new findings, the researchers propose that this kind of domestication happened just once, and probably from "a population of wolf that roamed the tundra steppe of the last Ice Age," Dalén shared.
As for what triggered the event, he and her colleagues suspect that "dogs may have originated through capture of wolf cubs or through self-domestication via attraction to food scraps," such as the meat and bones left behind by hunter-gatherers.
This is significant, because other research groups have tied dog domestication to farming, when humans first settled down to grow crops. That happened long after 27,000 years ago, however, so Skoglund and his team do not think farming led to dog domestication.
After domestication occurred, the researchers believe that as the wolf-resembling dogs traveled with humans, they interbred with multiple regional wolf populations, such as the one for the Taimyr wolf in Siberia.
Greger Larson, director of the Palaeogenomics & Bio-Archaeology Research Network at the University of Oxford, told Discovery News that the new study "is a significant step forward in the long winding road toward a satisfying understanding of how, when and where dogs were domesticated."
Larson said that the two major findings of the new paper are the recalibration of the molecular rate of evolution between dogs and wolves, and the demonstration that some modern dog breeds may share genes with certain early regional wolves.
This "suggests," he said, "that regardless of where dogs were domesticated, they often acquired a portion of their genomes from local wolf populations. This has been suspected, but never quite demonstrated like this."
In terms of precisely when and where the very first dogs emerged, he said that it's too early to close the book on the still heated debate.
Shown is a reproduction of a wolf painting from Font-de-Gaume cave in south-west France. The paintings in the cave date from around 17,000 BC.
A pointer named “Major” is identified as the first known example of a modern dog. A description of the dog was found in a now-obscure 1865 edition of a Victorian journal called The Field. It marks the earliest reported dog breed based on physical form and pedigree. “The invention of ‘breed,’ physically and imaginatively, still shapes how we see and think about dogs today,” Michael Worboys, Director of the University of Manchester’s Centre for the History of Science, Technology and Medicine, told Discovery News. Worboys and his team found the information concerning “Major” while preparing a new museum exhibit on dogs.
The first domestication of dogs was thought to have taken place 31,680 years ago -- but new research suggests the skull in question likely belong to a wolf. This particular specimen was found with a still-visible mammoth bone in its mouth.
The paleolithic dog remains resembled a modern Siberian husky, but suggest an animals that was significantly larger. Today, the Siberian husky, Samoyed and Alaskan malamute breeds are all closely related. "The most remarkable difference between these dogs and recent dog breeds is the size of the teeth,” paleontologist Mietje Germonpré said. Other early dog breeds, with a focus on the U.K., are featured in the museum exhibit curated by Worboys and his team. Entitled “Breed: The British and Their Dogs,” the exhibit runs at the University of Manchester museum through April 14.
Another team of researchers, led by Heidi Parker of the National Human Genome Research Institute, used DNA analysis to determine the genetic relationships of numerous dog breeds. One such ancient breed is the Afghan hound. As its name suggests, it's native to the Middle East. It’s one of the oldest dog breeds in existence, and was originally used for hunting hares and gazelles.
Parker and her team found that Akitas are yet another ancient breed. These dogs originated in Asia and are genetically similar to chow chows. The breed was not included in the first dog show. “The first dog show was in 1859 when only two varieties were shown: pointers and setters,” Worboys said. It had nothing to do with the handsome Akita’s looks, as he explained that the first dog show was “for gun dogs only.”
The sleek-bodied saluki comes from Iran, where its distant ancestors might have once lived near the earliest farmers from the Fertile Crescent. Dogs in this region evolved the ability to eat a starch-rich diet around 12,000 years ago. “Our findings show that it was crucial to early dogs to be able to thrive on a diet rich in starch,” Uppsala University’s Erik Axelsson, who led a related study, told Discovery News. “That indicates that dog domestication may be linked to the development of agriculture. It is possible that dogs may have been domesticated independently at locations where agriculture developed early, such as the Fertile Crescent and China.”
One of the most ancient dog breeds native to the United States is the Alaskan malamute. The DNA study found that they are genetically similar to Siberian huskies. This large, muscular dog was used -- and still is -- for pulling sleds, hauling freight by other means, and for additional work tasks.
The basenji is “an ancient African breed,” according to Parker and her colleagues. While “Major” the pointer is the first documented modern breed of dog, the basenji is arguably the first dog to be heavily bred by humans. Although this dog hails from central Africa, paleontologists believe its wolf ancestors originally came from eastern Asia.
In China, the chow chow is affectionately referred to as Songshi Quan, meaning “puffy-lion dog.” It is genetically close to the Akita, also from Asia. It represents yet another early breed.
Of the four most ancient known Asian dog breeds, the shar-pei was the first to diverge from a wolf ancestor, suggesting it is the oldest known Asian breed. This dog is famous for its deep wrinkles and blue-black tongue. Mutations of the same gene that causes wrinkles in these dogs can also cause wrinkling of human skin.