狗类可能起源于中东地区

Dogs likely originated in the Middle East, not Asia or Europe, according to a new genetic analysis by an international team of scientists led by UCLA biologists. The research, funded by the National Science Foundation and the Searle Scholars Program, appears March 17 in the advance online edition of the journal Nature. "Dogs seem to share more genetic similarity with Middle Eastern gray wolves than with any other wolf population worldwide," said Robert Wayne, UCLA professor of ecology（生态学） and evolutionary biology and senior author of the Nature paper. "Genome-wide analysis now directly suggests a Middle East origin for modern dogs. We have found that a dominant（支配的，统治的） proportion of modern dogs' ancestry derives from（源自，来自） Middle Eastern wolves, and this finding is consistent with（与……一致） the hypothesis that dogs originated in the Middle East.

"This is the same area where domestic cats and many of our livestock（家畜，牲畜） originated and where agriculture first developed," Wayne noted.

Previous genetic research suggested an East Asian origin for dogs, "which was unexpected," Wayne said, "because there was never a hint in the archaeological record that dogs evolved there."

"We were able to study a broader sampling of wolves globally than has ever been done before, including Middle Eastern wolves," said the paper's lead author, Bridgett vonHoldt, a UCLA graduate student of ecology and evolutionary biology in Wayne's laboratory who studies the genetics of dog domestication（驯养，教化） . "In our analysis of the entire genome, we found that dogs share more unique markers with Middle Eastern wolves than with East Asian wolves. We used a genome-wide approach, which avoids the bias of single genome region."

The biologists report genetic data from more than 900 dogs from 85 breeds (including all the major ones) and more than 200 wild gray wolves (the ancestor of domestic dogs) worldwide, including populations from North America, Europe, the Middle East and East Asia. They used molecular（分子的） genetic techniques to analyze more than 48,000 genetic markers. No previous study has ever analyzed anywhere near that many markers.

The biologists have samples from Israel, Saudi Arabia and Iran — but they have not pinpointed（准确地找到） a specific location in the Middle East where dogs originated.

"This study is unique in using a particular technology called a single nucleotide（核苷酸） polymorphism（多态性） , or SNP, genotyping chip（检测基因分型芯片） ; these chips interrogate（审问，询问） the nucleotides at 48,000 locations in the genome," said John Novembre, UCLA assistant professor of ecology and evolutionary biology and a member of UCLA's Interdepartmental（不同学科间的） Program in Bioinformatics. "We are able to compare dogs looking at not just one small part of the genome, but at 48,000 different locations. That gives us the fine-scale resolution to analyze how these breeds are related to one another and how they are related to wolves."

Previous genetic research had suggested an East Asian origin based on the higher diversity of mitochondrial（线粒体的） sequences in East Asia and China than anywhere else in the world. (Mitochondria are tiny cellular structures outside the nucleus that produce energy and have their own small genome.) However, that research was based on only one sequence, a small part of the mitochondrial genome, Wayne noted.

"That research made extrapolations（推断） about how the domestic dog has evolved from examination of one region in the mitochondrial genome," Wayne said. "This new Nature paper is a much more comprehensive analysis because we have analyzed 48,000 markers distributed throughout the nuclear genome to try to conclude where the most likely ancestral（祖先的，祖传的） population is.

"What we found is much more consistent with the archaeological record," he said. "We found strong kinship（亲属关系） to Middle Eastern gray wolves and, to some extent, European gray wolves — but much less so to any wolves from East Asia. Our findings strongly contradict the conclusions based on earlier mitochondrial DNA sequence data."