Where do dogs come from?

狗是从哪里来的？

Gray wolves are their ancestors. Scientists are pretty consistent about that. And researchers have suggested that dogs’ origins can be traced to Europe, the Near East, Siberia and South China.

灰狼是狗的祖先。在这件事上，科学家们的意见相当一致。研究人员认为，狗的起源可以追溯到欧洲、近东、西伯利亚和中国南方。

Central Asia is the newest and best candidate, according to a large study of dogs from around the world.

对世界各地犬只进行的一项大型研究最新显示，狗最有可能的起源地是中亚。

Laura M. Shannon and Adam R. Boyko at Cornell University, and an international group of other scientists, studied not only purebred dogs, but also street or village dogs — the free-ranging scavengers that make up about 75 percent of the planet’s one billion dogs.

康奈尔大学(Cornell University)的劳拉·M·莎伦(Laura M. Shannon)和亚当·R·博伊科(Adam R. Boyko)与其他科学家一起，组成了一个国际研究小组。该小组不只调查纯种犬，也包括街上或乡村里的狗——全球共有十亿只狗，其中大约75%是自由来去的流浪狗。

Dr. Shannon analyzed three different kinds of DNA, Dr. Boyko said, the first time this has been done for such a large and diverse group of dogs, more than 4,500 dogs of 161 breeds and 549 village dogs from 38 countries. That allowed the researchers to determine which geographic groups of modern dogs were closest to ancestral populations genetically. And that led them to Central Asia as the place of origin for dogs in much the same way that genetic studies have located the origin of modern humans in East Africa.

莎伦博士分析了三种不同类型的DNA，博伊科博士说，这是第一次对如此众多、如此多样化的犬只进行研究，包括了161个品种的逾4500只狗，以及来自38个国家的549只乡村狗。因此研究人员能够分析出哪些现代犬只的地理群落在基因上最接近其祖先群体。基因研究确定了现代人类起源于东非，而他们也采用大致一样的方式，确定了犬类的起源地是中亚。

The analysis, Dr. Boyko said, pointed to Central Asia, including Mongolia and Nepal, as the place where “all the dogs alive today” come from. The data did not allow precise dating of the origin, he said, but showed it occurred at least 15,000 years ago. They reported their findings Monday in Proceedings of the National Academy of Sciences.

博伊科博士说，分析显示，包括蒙古和尼泊尔在内的中亚地区是“目前所有尚存的犬种”的来源地。他说这些数据不足以对起源进行精确测年，但从中可以看到是在至少1.5万年前。本周一，他们的报告发表在《美国国家科学院院刊》(Proceedings of the National Academy of Sciences)上。

Greger Larson of Oxford University, who is leading a large international effort to analyze ancient DNA from fossilized bones, said he was impressed by the scope of the study. “It’s really great to see not just the sheer number of street dogs, but also the geographic breadth and the number of remote locations where the dogs were sampled,” he said in an email. He also praised the sampling of different kinds of DNA and the analytic methods.

牛津大学的格雷格·拉尔森(Greger Larson)是一个大型国际项目的领导者，主持对骨化石中古代DNA的分析工作。拉尔森说这项犬只研究的规模给他留下了深刻的印象。“该研究涵盖的流浪狗数目，以及采样犬只所涉及的地域广度和边远地区的数量，让人觉得很了不起，”他在一封电邮中说。他还称赞了对不同种类DNA进行采样的做法以及分析方法。

But in the world of dog studies, very little is definitive. The most recent common ancestor of today’s dogs lived in Central Asia, Dr. Boyko said, although he cannot rule out the possibility that some dogs could have been domesticated elsewhere and died out. Or dogs domesticated elsewhere could have gone to Central Asia from somewhere else and then diversified into all the canines alive today, he said.

但在犬类研究领域，很少有研究是确定的。博伊科博士表示，现存犬种的最近共祖生活在中亚地区，但他无法排除一些犬只可能在其他地方受到驯化并灭绝的可能性。他表示，或者在其他地方经过驯化的犬只从别的地方来到中亚，然后经过多样化发展，演化成现存的所有犬种。

Dr. Larson, who was not involved with the study, said he thought the Central Asia finding required further testing. He said he suspected that the origins of modern dogs were “extremely messy” and that no amount of sampling of living populations will be definitive. He said a combination of studies of modern and ancient DNA is necessary.

没有参与这项研究的拉尔森表示，他认为起源于中亚的结果需要进一步的检验。他认为现代犬只的起源“非常混乱”，即使对再多的现存犬只取样也无法确定。他表示，需要把对现代及古代DNA的研究结合起来。

Dr. Boyko said the new research for the first time analyzed three sources of DNA from both purebred and village dogs worldwide. The team analyzed DNA from all the chromosomes in the cell nucleus, from the Y chromosome specifically, found only in males, and from mitochondria, cellular energy machines outside the nucleus that are inherited from the mother.

博伊科博士表示，新研究首次分析了世界各地的纯种狗和乡村狗的三种DNA。该团队分析了细胞核的所有染色体、只有公犬携带的Y染色体及线粒体的DNA，线粒体是位于遗传自母体的细胞核外的细胞能量制造结构。

Dr. Boyko traveled to a number of the locations where blood was drawn from village dogs. He said, “The great thing about working with dogs is that if you show up with food you don’t usually have trouble recruiting subjects. Usually.”

博伊科博士走访了很多乡村狗的采血点。他表示，“与狗一起工作最棒的一点就是，如果你拿着食物，征召狗作为实验对象通常不会遇到困难。通常是这样。”

He added: “We showed up in Puerto Rico at a fishing village and the dogs turned up their noses at roast beef sandwiches. They were used to eating fish entrails.”

他还表示，“我们去了波多黎各的一个渔村，那里的狗过来嗅烤牛肉三明治。它们通常吃鱼内脏。”