Ancient Dog Skull Shows Early Pet Domestication
33,000-year-old fossil suggests dogs arose in multiple places, study says.
The skull of the fossil dog found in Siberia.
Photograph courtesy Yaroslav Kuzmin, PLoS ONE
by Christine Dell'Amore
National Geographic News
Published August 19, 2011
It took 33,000 years, but one Russian dog is finally having its day.
The fossilized remains of a canine found in the 1970s in southern Siberia's Altay Mountains (see map) is the earliest well-preserved pet dog, new research shows.
Dogs—the oldest domesticated animals—are common in the fossil record up to 14,000 years ago. But specimens from before about 26,500 years ago are very rare. This is likely due to the onset of the last glacial maximum, when the ice sheets are at their farthest extent during an ice age.
With such a sparse historical record, scientists have been mostly in the dark as to how and when wolves evolved into dogs, a process that could have happened in about 50 to a hundred years.
"That's why our find is very important—we have a very lucky case," said study co-author Yaroslav Kuzmin, a scientist at the Russian Academy of Sciences in Novosibirsk.
In the case of the Russian specimen, the animal was just on the cusp of becoming a fully domesticated dog when its breed died out.
(See dog-evolution pictures.)
Dogs Arose at Multiple Sites?
Kuzmin and colleagues recently used radiocarbon dating to examine the skull and jaw of the Russian dog in three independent laboratories. Each lab confirmed the fossil's age at around 33,000 years old.
Burnt twigs also found at the site, known as Razboinichya Cave, suggest that hunter-gatherers used the space for something, and it's likely the dog was their pet before its death from unknown causes, Kuzmin said.
Cold temperatures and nonacidic soil in the cave likely kept the dog's remains from completely decaying, he added.
The team compared the Russian dog fossils with the bones of wild wolves, modern wolves, domesticated dogs, and early doglike canids that lived before 26,500 years ago.
The results showed that the dog—which probably looked like a modern-day Samoyed—most closely resembled fully domesticated dogs from Greenland in size and shape. That's not to say the two dog types are related, though, since the new study didn't run DNA analysis.
(See "Dogs' Brains Reorganized by Breeding.")
Because it wasn't fully domesticated, the Russian dog retained some traits from its ancestors—namely wolf-like teeth. But the animal bore no other resemblance to ancient or modern wolves or to dog breeds from elsewhere in Russia, Kuzmin and colleagues found.
The discovery suggests that this dog began its association with humans independently from other breeds, which would mean that dog domestication didn't have a single place of origin—contrary to some DNA evidence, the study said.
(See "Where Did Dogs Become Our 'Best Friends?'")*
Curious Wolves Went to the Dogs
In general, dogs likely became domesticated when curious wolves began to hang around Stone Age people, who left butchered food remnants littering their camps, according to study co-author Susan Crockford, an anthropologist and zooarchaeologist at the University of Victoria in Canada.
This phenomenon occurred in Europe, the Middle East, and China, according to the study, published July 28 in the journal PLoS ONE.
(Also see "Oldest Domesticated Dog in Americas Found—Was Human Food.")
Animals that were more comfortable around humans underwent changes in their growth rates—probably regulated by hormones—that eventually changed their reproductive patterns, sizes, and shapes, turning them into dogs, Crockford said by email.
For example, dogs became smaller, developed wider skulls, and gave birth to bigger litters than wolves, she said.
"The somewhat curious and less fearful 'first founders' became even more so as they interbred amongst themselves," Crockford said.
(Read more about dogs in National Geographic magazine.)
Dog Domestication a Chaotic Process
Yet the process of dog domestication in Europe and Asia was chaotic, with many new breeds evolving and then dying out, study co-author Kuzmin noted.
The Russian dog was lost, for example, possibly because the advancing glacial age made hunter-gatherers even more mobile, since they had to range farther to find food.
Some experts have theorized that wolves have to stay in the same place for several decades before they evolve into fully domesticated dogs, Kuzmin said.
Indeed, "domestication is a process as opposed to an event," R. Lee Lyman, an anthropologist at the University of Missouri, Columbia, said by email. "It takes time for sufficient genetic change to occur for a population to evolve from a wild ancestral species into a descendant domestic species."
(See National Geographic fans' dog pictures.)
What's more, "not every evolutionary change is successful in the sense of [a] daughter population diverging from its ancestral lineage and producing a new, distinct lineage or species, domestic or not."
The study, Lyman said, "underscores [these] two important facts that archaeologists sometimes fail to appreciate."
* Where Did Dogs Become Our "Best Friends"?
for National Geographic News
August 3, 2009 DNA from scrappy dogs in African villages is raising doubts about a theory that dogs first became "man's best friend" in East Asia. Based on DNA evidence, [some] scientists believe that domestic dogs originated from Eurasian gray wolves sometime between 15,000 and 40,000 years ago.
(Related: "Dog Genome Mapped, Shows Similarities to Humans.")
The history of how dogs became human companions, however, remains muddy.
In 2002 researchers had examined DNA from hundreds of dogs around the world and found that East Asian dogs are the most genetically diverse.
Since the highest diversity should exist in the region where dogs first went from wolf to woof, the study seemed to suggest that the dog-human bond was forged in East Asia.
That study included almost equal numbers of East Asian "breed" dogs and "village" dogs, said study co-author Adam Boyko, a biologist at Cornell University in Ithaca, New York.
Breed dogs include purebred and mixed-breed animals. Village dogs are those that are indigenous to a specific region and "were not subject to the same degree of intense artificial selection and closed breeding practices that characterize modern breed dogs," the study authors write.
For the new survey, Boyko and colleagues examined DNA from village and breed dogs living across Africa, plus Puerto Rican street dogs and mixed-breed dogs in the U.S.
The team found that the African village dogs' genetic diversity matches that of East Asian village dogs.
The authors note that this does not mean domestic dogs might have originated in Africa.
"We know Africa cannot be where dogs were domesticated, because there are no gray wolves there," Boyko said. But the findings call into question the previous proof that dogs were first domesticated in East Asia.
"What we think we are picking up on is actually the signal of village dogs have more genetic diversity than breed dogs do, … ," he said.
That's not to say East Asia is out of the running. But to definitively solve the riddle, scientists should obtain genetic samples from village dogs throughout Europe, the Middle East, and East Asia, Boyko said.
Once the timing and location of domestication is resolved, he added, doggie DNA could help unravel mysteries about early human-migration patterns and population histories.
For example, he noted, "there's pretty good evidence that they followed humans into the New World, and they certainly followed along the Polynesians in their exploring."
Findings appear this week in the Proceedings of the National Academy of Sciences
--Please refer to the earlier postings here considering the idea that certain East African (Ethiopian) "Jackals" are actually genetically "Wolves" and are more likely to be the ancestors of all domesticated dogs from an origin back before One Hundred Thousand years ago. The date is no joke and comes from good research and previously-published genetic studies. My conclusion is that the first dogs went Out of Africa alongside their human masters, already about the same thing as the Dingoes that first appeared in Australia.
Best Wishes, Dale D.