狗從哪裏來 基因研究揭曉答案

Where do dogs come from?

狗是從哪裏來的？

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。在這件事上，科學家們的意見相當一致。研究人員認爲，狗的起源可以追溯到歐洲、近東、西伯利亞和中國南方。

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

對世界各地犬隻進行的一項大型研究最新顯示，狗最有可能的起源地是中亞。

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.

康奈爾大學(Cornell University)的勞拉·M·莎倫(Laura M. Shannon)和亞當·R·博伊科(Adam R. Boyko)與其他科學家一起，組成了一個國際研究小組。該小組不只調查純種犬，也包括街上或鄉村裏的狗——全球共有十億隻狗，其中大約75%是自由來去的流浪狗。

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.

莎倫博士分析了三種不同類型的DNA，博伊科博士說，這是第一次對如此衆多、如此多樣化的犬隻進行研究，包括了161個品種的逾4500只狗，以及來自38個國家的549只鄉村狗。因此研究人員能夠分析出哪些現代犬隻的地理羣落在基因上最接近其祖先羣體。基因研究確定了現代人類起源於東非，而他們也採用大致一樣的方式，確定了犬類的起源地是中亞。

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.

博伊科博士說，分析顯示，包括蒙古和尼泊爾在內的中亞地區是“目前所有尚存的犬種”的來源地。他說這些數據不足以對起源進行精確測年，但從中可以看到是在至少1.5萬年前。本週一，他們的報告發表在《美國國家科學院院刊》(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.

牛津大學的格雷格·拉爾森(Greger Larson)是一個大型國際項目的領導者，主持對骨化石中古代DNA的分析工作。拉爾森說這項犬隻研究的規模給他留下了深刻的印象。“該研究涵蓋的流浪狗數目，以及採樣犬隻所涉及的地域廣度和邊遠地區的數量，讓人覺得很了不起，”他在一封電郵中說。他還稱讚了對不同種類DNA進行採樣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.

但在犬類研究領域，很少有研究是確定的。博伊科博士表示，現存犬種的最近共祖生活在中亞地區，但他無法排除一些犬隻可能在其他地方受到馴化並滅絕的可能性。他表示，或者在其他地方經過馴化的犬隻從別的地方來到中亞，然後經過多樣化發展，演化成現存的所有犬種。

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.

沒有參與這項研究的拉爾森表示，他認爲起源於中亞的結果需要進一步的檢驗。他認爲現代犬隻的起源“非常混亂”，即使對再多的現存犬隻取樣也無法確定。他表示，需要把對現代及古代DNA的研究結合起來。

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純種狗和鄉村狗的三種DNA。該團隊分析了細胞核的所有染色體、只有公犬攜帶的Y染色體及線粒體的DNA，線粒體是位於遺傳自母體的細胞核外的細胞能量製造結構。

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.”

博伊科博士走訪了很多鄉村狗的採血點。他表示，“與狗一起工作最棒的一點就是，如果你拿着食物，徵召狗作爲實驗對象通常不會遇到困難。通常是這樣。”

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.”

他還表示，“我們去了波多黎各的一個漁村，那裏的狗過來嗅烤牛肉三明治。它們通常吃魚內臟。”