We didn't go to the dogs - canines went to the people
Submitted by coldrum on Wednesday, 25 April 2007 Page Views: 1921
TV and RadioThat dogs descended from wolves is commonly accepted. So is the theory that this evolution took about 14,000 years.Or did it? Evolutionary biologist, Susan Crockford suggests the metamorphosis could have taken place over the span of a single human life -- between 20 and 40 years.
Susan Crockford hunts through a large, shallow drawer, from which she pulls a tray of spinal bones. She has found Sheukh, her old pet Malamute. Stacks of wide specimen drawers line the walls of this 400-square-foot room at the University of Victoria's anthropology department, where Crockford, an evolutionary biologist, teaches as an adjunct professor.
Crockford has formulated a theory that thyroid hormones interacted with genes in the evolution of canids, that is, the transformation of wolves into dogs. Crockford discusses her theory on the upcoming PBS two-part special Dogs That Changed the World, narrated by Academy Award-winning actor F. Murray Abraham.
Crockford points to a 40-year experiment by geneticist Dmitry K. Belyaev and his Siberian research group at the Institute of Cytology and Genetics, where silver foxes were selectively bred for gentleness.
As expected, each succeeding generation was more docile than the last.
What was not expected was that within 20 generations, changes in appearance emerged among the litters. Some pups displayed piebald markings, curled tails and drooping ears. Some also developed another distinctive dog behaviour: They barked.
Foxes breed annually, wolves every two years, so if a similar progression occurred on wolves' journey toward domestication, it could have taken place over 40 years, still within a single human lifespan.
That, says Crockford, would explain a number of archeological findings from sites dating back between 4,000 and 14,000 years. At these sites, most of which are in the Americas, canines were buried atop humans, the dogs set in curled postures, as though asleep.
For more, including the proposed mechanism for the genetic effects of natural selection and how dogs changed the lifestyle of their human companions, see the news item linked here.
Note: The episode of PBS's "Nature" is now rerunning. Check local listings in the United States and Canada.
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