Modern-day pooches most closely related to European canines, study says


A lateral view of a 26,000-year-old Pleistocene wolf from the Trou des Nutons cave in Belgium. This wolf species was particularly large. (Courtesy of Royal Belgian Institute of Natural Sciences)
November 14, 2013

Amid the harsh, icy lands of ancient Europe, early man found an unexpected companion — the snarling, carnivorous wolf — that eventually would become his modern-day counterpart’s best furry friend.

New genetic analysis of 148 prehistoric and modern animals has revealed that our present-day pooches, from dingos to Saint Bernards, are most closely related to either ancient or modern European canines. The comprehensive study points to places such as Germany and Switzerland as to where domestication of dogs probably began, and to free-roaming wolves evolving into the Rovers and Spots we know and love today.

The study was published online Thursday in the journal Science.

“The first dogs looked like wolves,” said study author and evolutionary biologist Robert Wayne of the University of California at Los Angeles. “It took some time before these proto-dogs started to look different.”

Wayne and his colleagues estimate that domestication occurred around 18,800 to 32,100 years ago, when ice sheets extended over much of Europe’s northern lands. Hunter-gatherers feasted on huge kills, such as mammoths. But at the same time, early men looked over their shoulders for predatory cave bears and lions.

So when a few of the friendlier wolves started to hang around for leftover mammoth, perhaps the humans didn’t mind because they provided a little extra protection. They began the first step toward domestication by co-existing with wolves in a mutually beneficial relationship, the scientists speculate.

The docile wolves bred and stuck with their new human friends. They stopped intermingling as much with the wild wolves. After generations upon generations of selective breeding, wolves slowly became more like the dogs of today — still the only large carnivore ever domesticated, Wayne said. They even adapted to a high-starch diet, leaving them in better shape during human society’s later forays into agriculture.

Although there was no question that modern dogs descended from wolves, recent research findings clashed over where and when domestication originated.

Archeologists dug up the oldest dog-like fossils dating back 36,000 years ago in Western Europe and Siberia, but it wasn’t certain whether they truly were the bones of early dogs or some other creature. Curiously, the latest genetic studies traced the family tree of modern dogs and wolves to canine origins in the Middle East or East Asia — tens of thousands of years after those first fossils.

“The fossils spoke for Europe, but the genetics spoke for Asia,” said Olaf Thalmann, study author and population geneticist at Finland’s University of Turku. “At some point, you have to combine the two stories.”

So that’s exactly what Thalmann and his colleagues set out to do. The team gathered genetic data from 18 prehistoric dog-like fossils from Eurasia and the New World, along with a slew from present-day dogs and wolves.

They nabbed insight on how to best work with old, battered DNA from the groundbreaking sequencing of the Neanderthal genome in 2010.

“Ancient DNA is shattered into many, many small pieces,” said Elaine Ostrander, a geneticist at the National Institutes of Health who was not involved in the study. “When you have an ancient sample, sequencing the mitochondrial DNA is the right first thing to do.”

Mitochondria are mini-organs inside cells that contain a bit of DNA, like the nucleus. But the DNA in the nucleus has only two copies, compared with as many as 1,000 copies of mitochondrial DNA in a single cell. When it comes to extracting prehistoric DNA, the more backup copies, the better.

The team input 148 complete and partial mitochondrial sequences into a model that spit out an evolutionary tree. To the researchers’ surprise, all four of the living groupings of modern dogs had their closest ancestors in Europe, not Asia.

One group that included a Siberian husky and a Great Dane had sequences most closely related to that of an ancient wolf from Switzerland. Ancestors for a second set of present-day dogs containing a pit bull terrier and a cocker spaniel included two ancient dogs found in Germany.

Also, two of the oldest fossils, including one from Siberia, were from creatures not directly related to today’s pooches. Thalmann thinks these may have been unsuccessful domestication efforts, where these wolves became partly dog-like, but the branch of evolution got cut short somehow.

“There is not a single proto-dog — Eve, or Spot, they would call that dog — from which modern dog breeds descended,” Ostrander said. Today, more than 300 breeds exist with humans continuing to select for fancier or odder traits. The majority of these are only a few hundred years old.

Ostrander, who has done research on dog genetics for more than 20 years, finds the results plausible given human trade routes and population migrations.

“Using state-of-the-art genome technologies, they have come up with very clear answers about what is likely to be the location of major dog domestication events,” she said. “All the pieces fit together very nicely.”

Kim is a freelance science journalist based in Philadelphia.

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