Wolves probably were domesticated by European hunter–gatherers more than 18,000 years ago and slowly grown into dogs that started to be household pets, UCLA life researchers report.
“We found that instead of recent wolves being closest to domestic dogs, ancient European wolves were directly related to them,” stated Robert Wayne, a professor of ecology and evolutionary biology in UCLA’s College of Letters and Science and senior author of the research. “This brings the genetic record into agreement with the archaeological record. Europe is where the oldest dogs are found.”
The UCLA researchers’ genetic study was published yesterday in the journal Science and highlighted on the journal’s cover.
In similar research last May, Wayne and his co-workers revealed at the Biology of Genomes meeting in New York the results of their assessment of the complete nuclear genomes of 3 recent wolf breeds (from the Middle East, East Asia and Europe), 2 ancient dog breeds and the boxer dog breed.
“We analyzed those six genomes with cutting-edge approaches and found that none of those wolf populations seemed to be closest to domestic dogs,” Wayne stated. “We thought one of them would be, because they represent wolves from the three possible centers of dog domestication, but none was. All the wolves formed their own group, and all the dogs formed another group.”
The UCLA biologists as well hypothesized at that conference that a now-extinct population of wolves was more straight associated to dogs.
For the latest study in Science, the scientists analyzed 10 ancient “wolf-like” animals and 8 “dog-like” animals, mainly from Europe. These animals were all more than 1,000 years old, many were thousands of years old, and 2 were more than 30,000 years old.
The biologists examined the mitochondrial DNA of the animals, which is abundant in ancient remains. By comparing this ancient mitochondrial DNA with the modern mitochondrial genomes of 77 domestic dogs, 49 wolves and 4 coyotes, the scientists confirmed that the domestic dogs were genetically assembled with ancient wolves or dogs from Europe — not with wolves located anyplace else in the world or even with modern European wolves. Dogs, they came to the conclusion, derived from ancient wolves that lived in Europe and are now extinct.
Wayne stated that that the domestication of wolves probably took place amongst ancient hunter–gatherer communities instead of as part of humans’ development of sedentary, agricultural-based groups.
“The wolf is the first domesticated species and the only large carnivore humans ever domesticated,” Wayne stated. “This always seemed odd to me. Other wild species were domesticated in association with the development of agriculture and then needed to exist in close proximity to humans. This would be a difficult position for a large, aggressive predator. But if domestication occurred in association with hunter–gatherers, one can imagine wolves first taking advantage of the carcasses that humans left behind — a natural role for any large carnivore — and then over time moving more closely into the human niche through a co-evolutionary process.”
The concept of wolves following hunter–gatherers likewise helps to clarify the eventual genetic divergence that contributed to the appearance of dogs, he said. Wolves following the migratory patterns of these early human communities would have abandoned their territoriality and would have been less likely to multiply with resident territorial wolves. Wayne mentioned that a group of modern wolves shows this process.
“We have an analog of this process today, in the only migratory population of wolves known existing in the tundra and boreal forest of North America,” he stated. “This population follows the barren-ground caribou during their thousand-kilometer migration. When these wolves return from the tundra to the boreal forest during the winter, they do not reproduce with resident wolves there that never migrate. We feel this is a model for domestication and the reproductive divergence of the earliest dogs from wild wolves.”
“We know also that there were distinct wolf populations existing ten of thousands of years ago,” Wayne added. “One such wolf, which we call the megafaunal wolf, preyed on large game such as horses, bison and perhaps very young mammoths. Isotope data show that they ate these species, and the dog may have been derived from a wolf similar to these ancient wolves in the late Pleistocene of Europe.”
In a study released in the journal nature in 2010, Wayne and co-workers revealed that dogs appear to share more genetic likeness with living Middle Eastern gray wolves than with any other wolf population, which suggested a Middle East origin for modern dogs. The fresh genetic data have persuaded him otherwise.
“When we previously found some similarity between Middle Eastern wolves and domestic dogs, that similarity, we are now able to show, likely was the result of interbreeding between dog and wolves during dog history. It does not necessarily suggest an origin in the Middle East,” Wayne said. “This alternative hypothesis, in retrospect, is one that we should have considered more closely. As hunter–gatherers moved around the globe, their dogs trailing behind probably interbred with wolves.”
Wayne views the new genetic data “persuasive” but said they have to be verified with an evaluation of genetic sequences from the nucleus of the cell — a considerably larger sample than that found in mitochondrial DNA (approximately 20,000 base pairs). This is tough due to the fact the nuclear DNA of ancient remains has a tendency to become degraded.
While Wayne plans to go after this followup study, he said he does not expect a nuclear genome analysis to change the central finding. Nevertheless, he stated, it will fill in more of the specifics.
“This is not the end-story in the debate about dog domestication, but I think it is a powerful argument opposing other hypotheses of origin,” he said.
There is a scientific discussion about when dogs were domesticated and regardless of whether it was associated with the growth of agriculture fewer than 10,000 years ago, or whether it took place much earlier. In the new Science research, Wayne and his co-workers estimate that dogs were domesticated between 18,000 and 32,000 years ago.
Roughly 80 percent of dog breeds are modern breeds that evolved in the last few hundred years, Wayne said. However a few dog breeds have ancient histories that go back thousands of years.
Wolves have been in the Old World for hundreds of thousands of years. The oldest dogs from the archaeological record come from Europe and Western Russia. A dog from Belgium dates back approximately 36,000 years, and a group of dogs from Western Russia is approximately 15,000 years old, Wayne said.