Sunday, November 17, 2013

Wolf to Dog - Scientists Agree on How, but But Where

Now Dr. Wayne and his colleagues are introducing a new line of evidence to the dog debate: ancient DNA. Over the past two decades, scientists have developed increasingly powerful tools to rescue fragments of DNA from fossils, producing “an explosion in the samples,” said Beth Shapiro of the University of California, Santa Cruz, a collaborator with Dr. Wayne.

On Thursday in the journal Science, Dr. Wayne, Dr. Shapiro and their colleagues report on the first large-scale comparison of DNA from both living and fossil dogs and wolves. They managed to extract DNA from 18 fossils found in Europe, Russia and the New World. They compared their genes to those from 49 wolves, 77 dogs and 4 coyotes.

The scientists examined a special kind of DNA found in a structure in the cell called the mitochondrion. Mitochondrial DNA comes only from mothers. Because each cell may have thousands of mitochondria, it is easier to gather enough genetic fragments to reconstruct its DNA.

The scientists did not find that living dogs were closely related to wolves from the Middle East or China. Instead, their closest relatives were ancient dogs and wolves from Europe.

“It’s a simple story, and the story is they were domesticated in Europe,” Dr. Shapiro said.

But Dr. Savolainen said the analysis was flawed. “It’s not a correct scientific study, because it’s geographically biased,” he said.

The study lacks ancient DNA from fossils from East Asia or the Middle East, and so it’s not possible to tell whether the roots of dog evolution are anchored in those regions. “You just need to have samples from everywhere,” Dr. Savolainen said.


- More Here

No comments: