Read the article and select the best answer. Article: Researchers at Sweden's KTH Royal Institute of Technology say they have found further proof that the wolf ancestors of today's dogs can be from southern East Asia -- findings that are contrary to theories placing the birth place in the Middle East. Dr Peter Savolainen, KTH researcher in evolutionary genetics, says a new study released Nov. 23 confirms that an Asian region south of the Yangtze River was the principal and probably the only region where wolves were domesticated by humans. Research data show clearly that dogs are descended from wolves, but there's never been scientific agreement on where in the world the domestication process began. "Our analysis of Y-chromosomal DNA now confirms that wolves were first domesticated in Asia south of Yangtze River -- we call it the ASY region -- in southern China or Southeast Asia," Savolainen says. The Y data supports previous evidence from mitochondrial DNA. "Taken together, the two studies provide very strong evidence that dogs appeared first in the ASY region," Savolainen says. Archaeological data and a genetic study recently published in Nature suggest that dogs originate from the Middle East. But Savolainen rejects that view. "Because none of these studies included samples from the ASY region, evidence from ASY has been overlooked," he says. Peter Savolainen and PhD student Mattias Oskarsson worked with Chinese colleagues to analyse DNA from male dogs around the world. Their study was published in the scientific journal Heredity. Approximately half of the gene pool was universally shared everywhere in the world, while only the ASY region had the entire range of genetic diversity. "This shows that gene pools in all other regions of the world most probably originate from the ASY region," Savolainen says. "Our results confirm that Asia south of the Yangtze River was the most important -- and probably the only -- region for wolf domestication, and that a large number of wolves were domesticated," says Savolainen. In separate research published recently in Ecology... Question: What is special about mitochondrial DNA? Options: A: It is only used in studying evolutionary relationships. B: It alone can provide hard evidence for Savolainen's research. C: It is the most useful in finding out the birth place of dogs. D: It comes from the mother of most animals and plants.
A:
D