http://www.npr.org/2013/07/10/200498354/barking-up-the-family-tree-american-dogs-have-surprising-genetic-roots
nprからです。昨今日本ではチワワはペットとして大人気ですね。そしてチワワは純粋なアメリカ種の血統を保っているようです。私も犬と猫を飼うのが往年の夢です。犬は大人しいラブラドールのような大型種、猫は黒い子猫がいい :oops:です。

Barking Up The Family Tree: American Dogs Have Surprising Genetic Roots
by RHITU CHATTERJEE July 10, 2013 5:29 PM

America is as much¹ of a melting pot for dogs as¹ it is for their human friends. Walk through any dog park and you'll find a range of breeds from Europe, Asia, even Australia and mutts and mixes of every kind.

But a few indigenous breeds in North America have a purer pedigree — at least one has genetic roots in the continent that stretch back 1,000 years or more, according to a new study. These modern North American breeds —² including that current urban darling, the Chihuahua —² descended from the continent's original canine inhabitants and have not mixed much with European breeds.

"There is ... archaeological and historical evidence that the native peoples of the Americas had dogs," says Peter Savolainen, an evolutionary geneticist at the KTH-Royal Institute of Technology in Stockholm and an author of the new study³. When humans first came to the Americas from Asia, they're thought to have brought with them dogs, whose descendants populated North and South America for centuries.

But those dogs didn't fare too well once Christopher Columbus got here. "It's known that most of these dogs were eradicated when Europeans arrived in America," says Savolainen. Pathogens the Europeans brought killed humans and dogs alike⁴, he says.

Any canines that survived are thought to have interbred with European dogs over time. Most researchers have assumed that today's dogs would have little⁵ trace of their ancient American ancestry.

To find out if that was indeed the case, Savolainen and his colleagues looked at the mitochondrial DNA of a handful of modern breeds with indigenous origins. Mitochondrial DNA is inherited from the mother and remains relatively unchanged over generations. By looking at the mitochondrial DNA sequence, one can get a peek at the ancient maternal ancestry. "You can go back in time as far as tens of thousands of years," Savolainen says.

He and his colleagues looked in particular at the maternal lineage of the Inuit sled dog, the Alaskan malamute, the Greenland dog, the Chihuahua, the Xoloitzcuintli (Mexican hairless dog), Perro Sín Pelo del Peru (Peruvian hairless dog) and a range of strays from North and South America. The scientists compared the DNA sequences of these dogs with those of hundreds of dogs from Europe and Asia.

Savolainen expected to find a strong European influence on these breeds, but he was surprised.

Except for some of the stray dogs and the Alaskan malamute, "they have very little⁵ influence of European dogs in these breeds," he says. "So they have been kept pretty pure."

When he and his team compared the sequences of the relatively⁶ unchanged breeds with those of 19 ancient dog sequences found across the two American continents, he was even more surprised. One breed — the Chihuahua — had a portion of DNA that was an exact match to that of an ancient dog.

"We have exactly the same unique DNA type in Mexico 1,000 years ago and in modern Chihuahua," Savolainen says. This suggests that at least this particular breed had genetic roots stretching back before the arrival of Europeans.

In addition, most American breeds in the study had a lot in common with present-day dogs from East Asia, he says. This genetic similarity is because the indigenous American breeds descended from the first dogs that traveled from Asia to the Americas.

Maternal ancestry, of course, can't tell the whole story, Savolainen says, and mitochondria trace the genetic lineage only through mothers.

But the evidence does show many modern North American dogs continue to carry a significant genetic signature from their distant past, he says. And that means that, like distinct languages, they're very much the products of the indigenous human cultures that created the breeds.

"These are [a] remaining part of the indigenous cultures — the Indian and Inuit culture — in America," Savolainen says. "And that makes it more important that these populations ... are preserved."

それでは英文の注意点を見ていきましょう。水色のマーカーに数字が附ってある部分がポイントです。下線付きの単語は下に意味を書いておきました。

1. "as much A as B"は「Bと同じくらいの量のA」という比較級の熟語です。比較級の熟語はこの他にも沢山あります。しかも比較級の熟語は同じような単語ばかり出てくるので非常に混同しやすいです。更にその割には実際の長文にはさほどは出てこない :(。一生懸命覚えても苦労があまり報われない。しかし、それはそれ。TOEICで800以上を目指すつもりならしっかり覚えましょう。
2. ここはハイフンを使った挿入句です。挿入句を読むときのコツはハイフン部は無視してその前と後ろで文をつなげて読みましょう。それに意味的にハイフン部分が加わると考えればいいでしょう。この場合なら、"These modern North American breeds descended from the continent's original..."「これらの近代北アメリカ種は大陸のオリジナル種からの系統をひいている...例えば現状の都市犬、可愛いチワワのように...」となるわけです。
3. Peter Savolainenという人をコンマ以下が全部説明しているだけです。論文やニュースなどでは客観性を重視するために人物を紹介した時はかなり長く説明されます。しかし本文内容とはあまり関係ない時が多いので、そういうものだということを知っておきましょう。
4. "Pathogens the Europeans brought killed humans and dogs alike"この文のメインの動詞が分かるでしょうか？
   そう、killedです。pathogens（病原菌）の後ろに関係代名詞whichが隠れています。そしてその関係代名詞節はbroughtで終わってしまっています。後ろには"A and B alike"「AもBも同様に」という熟語があります。よって訳は「ヨーロッパ人が運んできた病原菌は人間と同様に犬も殺した」となります。メインの動詞をしっかりと把握しましょう。
5. aのついていないlittleは「ほとんど～ない」という否定語句です。aのついていないfewも同じです。いつも意識して訳しましょう。
6. このrelativelyは「ひかくてき」です。副詞を知ることは中級以上の英語学習では非常に大切です。副詞はなるべく簡潔に訳すことです。勿論わざと難しい言葉ではったりを噛ましたい...なんてときもあるでしょうが、自分で訳して意味が分からないのでは困ります。例えば
   alternatively ⇒×「二者択一的に」　○「あるいは」
   arguably  ⇒×「議論の余地はあるが」　○「おそらく」
   exclusively  ⇒×「排他的に」　○「もっぱら」
   relatively  ⇒×「相対的に」　○「ひかくてき」
   virtually  ⇒×「仮想現実的に」　○「ほぼ」

barking up the family tree　"bark up the wrong tree"「見当違いをする：猟犬が間違った気を吠えたことから」と懸けてあります。
melting pot　（人種の）るつぼ
breed　種族
mutt　犬っころ
pedigree　血統
darling　可愛い人
descended from　～の血をひく
canine　犬、犬歯
descendant　子孫、末裔
populate　～に生息させる
fare　やっていく
eradicate　全滅させる
pathogen　病原体
interbreed　異種交配する
DNA sequence　DNA配列
as far as　はるか～
tens of thousands　何万も
lineage　血統、血筋
Inuit 　イヌイット
sled dog　そり犬
malamute　マラミュート犬
except for　~以外
in common with　～と共通

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