A widely held belief is that dogs evolved from gray wolves, but a new study finds that the common ancestor of dogs and wolves went extinct thousands of years ago.

What's more, the extensive DNA analysis -- published in the latest PLoS Genetics -- found that dogs are more closely related to each other than to wolves, regardless of their geographic origin. The genetic overlap seen today between dogs and wolves is likely then due to interbreeding after dog domestication.

"The common ancestor of dogs and wolves was a large, wolf-like animal that lived between 9,000 and 34,000 years ago," Robert Wayne, co-senior author of the study, told Discovery News. "Based on DNA evidence, it lived in Europe."

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For the study, Wayne, a professor in UCLA's Department of Ecology and Evolutionary Biology, and his colleagues generated genome sequences from three gray wolves: one each from China, Croatia and Israel, representing three regions where dogs are believed to have originated.

The researchers also produced genomes for two dog breeds: a basenji, a breed that originates in central Africa, and a dingo from Australia. Both locations have been historically isolated from modern wolf populations. The scientists, co-led by John Novembre, additionally sequenced the genome of a golden jackal to serve as an example representing earlier divergence.

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Instead of all three dogs being closely related to one of the wolf lineages, or each dog being related to its closest geographic counterpart, the DNA points to the dogs having descended from an unknown wolf-like ancestor.

Wayne explained that many animals went extinct during the late Pleistocene (20,000 to about 12,000 years ago), which experienced a global ice age. Coincidentally -- or maybe not -- modern humans also became more prevalent in Europe at this time. It could be that humans led to the extinction of some animals at that time, but the jury is still out on the issue.

A dog, left, and gray wolf, right, both howling.Baccharus/Wikimedia Commons/UK Wolf Conservation Trust

Dogs clearly were not in that group. Wayne now believes that dog and human interactions went through three primary stages:

1- Hunter gatherers, possibly even Neanderthals, interacted with dogs, probably benefiting from their presence. For example, dogs might have kept other, more dangerous, carnivores out of the way. They could have also helped with hunting.

2- With the emergence of agriculture, dogs lived near humans and adapted to an agricultural diet. Prior studies have found that dogs in such regions possess higher numbers of amylase genes that help to digest starch. Wolves have these genes too, the scientists found, but usually not in such high amounts.

3- In more recent history, humans have selectively bred dogs, which has dramatically changed the appearance, behavior and other attributes of dogs.

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Throughout this overall period of time, interbreeding with wolves occurred, and still happens, further complicating the genetic relationship between wolves and dogs.

Elaine Ostrander, an investigator at the National Human Genome Research Institute, told Discovery News, "This paper is exciting for students of canine history as well as dog owners because it clarifies the events leading up to dog domestication. We now know that it was not a single event, but several, which makes sense when we think about the extraordinary variation that we seen in modern dogs."

She added, "We also know that the critical intermediate -- the dog/wolf -- is not alive on the planet today. However we don't know why. Did is suffer from some infectious disease, a plague of sorts? Was it killed off by other animals? Did it starve?"