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HOME > PAST ISSUE > July-August 2009 > Article Detail

MARGINALIA

The Woof at the Door

Dogs may have been man’s best friend for thousands of years longer than we realized

Pat Shipman

Time to Tame

The creation of a domestic, useful, familiar canid by years of selectively breeding wild and terrifying wolves was almost certainly unplanned. The wolf at the beginning of the process of domestication was tamed—made individually docile—but the essential fact is that, over time, the offspring of those initial wolves were genetically inclined to be more tractable.

Domestication was one of the most brilliant accidents in the entire history of humankind. What’s more, we got it right the first time: Dogs were the original trial animal, and successful product, of such an accident—the happy outcome of years of unwitting experiments and dumb luck.

How long does domestication take? Nobody knows. In an experiment, Russian biologists kept a breeding colony of silver foxes and intentionally selected for breeding those with the least fear and the least aggression toward humans. After 10 generations, 18 percent of the foxes sought human contact and showed little fear. After 30 or so generations, a “domesticated fox” had been created.

The catch is that this experiment was deliberate and strictly controlled. The foxes could not breed with wild foxes and dilute the changing gene pool. Human contact was minimized so animals could not be tamed by their handlers. And because of the experiment’s scientific intent, no one could say, “Oh this one is so cute, let’s let it breed even if it is a little aggressive.” So in the case of dogs, without all these controls, the process could have taken much longer.

Another way of estimating the time at which domestic dogs originated is to consider their genetic differences from wolves. One prominent group of researchers, including Robert Wayne, along with Carles Vilà of the Uppsala University in Sweden and their collaborators, initially estimated in 1997 that dogs diverged from gray wolves 100,000 to 135,000 years ago. After more study, they revised their divergence date to between 40,000 and 100,000 years ago. Another group, led by Peter Savolainen of the Royal Institute of Technology in Sweden, favored the Chinese wolf, a subspecies of the gray wolf, as the probable ancestor and estimated in 2002 that it was domesticated between 15,000 and 40,000 years ago.

How do these genetic estimates stack up against the fossil record? Until 2009, the oldest known remains of domestic dogs were two adult skulls dated to between 13,000 and 17,000 years ago, from Eliseevichi, a region in Russia. Both had the relatively broad, short snout typical of dogs, and both were large, heavy animals, nearly the size of great Danes.

Then a team led by Mietje Germonpré of the Royal Belgian Institute of Natural Sciences reported a stunning new finding in the February 2009 issue of Journal of Archaeological Science: a nearly complete fossil dog skull dated to 31,680 + 250 years ago.





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