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  • Translator: Joseph Geni Reviewer: Morton Bast


  • When I was a young boy,


  • I used to gaze through the microscope of my father

    琥珀に閉じ込められた 昆虫を観察しました

  • at the insects in amber that he kept in the house.

    昆虫は驚くほど よく保存され

  • And they were remarkably well preserved,


  • morphologically just phenomenal.

    父と私は いつの日か

  • And we used to imagine that someday,

    昆虫たちが よみがえり

  • they would actually come to life

    琥珀の中から 這い出てきて

  • and they would crawl out of the resin,

    飛び立っていく姿を 想像しました

  • and, if they could, they would fly away.

    絶滅した動物の ゲノム配列について

  • If you had asked me 10 years ago whether or not

    解読できるかと 10年前に問われたなら

  • we would ever be able to actually sequence the genome of extinct animals,

    おそらく 「無理だ」 と答えたでしょう

  • I would have told you, it's unlikely.

    絶滅した動物を よみがえらせることが

  • If you had asked whether or not we would actually be able


  • to revive an extinct species,

    「夢物語さ」 と答えたでしょう

  • I would have said, pipe dream.

    しかし今日ここで 意外にも お伝えしたいのは

  • But I'm actually standing here today, amazingly,

    絶滅種のDNA配列の 再現が「可能性」ではなく

  • to tell you that not only is the sequencing

    現実のものとなったこと それに加えて

  • of extinct genomes a possibility, actually a modern-day reality,

    絶滅種の復活にも 手が届くようになったことです

  • but the revival of an extinct species is actually within reach,

    琥珀の中の 昆虫からではなく ―

  • maybe not from the insects in amber --

    そういえば 蚊は

  • in fact, this mosquito was actually used

    『ジュラシック・パーク』の ヒントになりましたね

  • for the inspiration for "Jurassic Park" —

    永久凍土の中で 良好な状況で保存された

  • but from woolly mammoths, the well preserved remains


  • of woolly mammoths in the permafrost.


  • Woollies are a particularly interesting,


  • quintessential image of the Ice Age.

    巨大で 毛むくじゃらで

  • They were large. They were hairy.

    大きな牙を持っています 私たちは象と同様の親近感を

  • They had large tusks, and we seem to have


  • a very deep connection with them, like we do with elephants.

    その理由は 象と私たちには

  • Maybe it's because elephants share


  • many things in common with us.

    死者を葬り 子供を教育します

  • They bury their dead. They educate the next of kin.


  • They have social knits that are very close.

    親近感は太古からの ものかもしれません

  • Or maybe it's actually because we're bound by deep time,

    というのは 象は私たちと同様に 約700万年前に

  • because elephants, like us, share their origins in Africa


  • some seven million years ago,


  • and as habitats changed and environments changed,


  • we actually, like the elephants, migrated out

    ヨーロッパからアジアへと 移住しました

  • into Europe and Asia.


  • So the first large mammoth that appears on the scene

    メリディオナリスマンモスで肩高は 4メートルもありました

  • is meridionalis, which was standing four meters tall

    体重は10トン 森林地帯に適応した種で

  • weighing about 10 tons, and was a woodland-adapted species

    西ヨーロッパから 中央アジアに広がり

  • and spread from Western Europe clear across Central Asia,

    さらに当時の ベーリング地峡を渡り

  • across the Bering land bridge


  • and into parts of North America.

    すると また気候変動が起こり

  • And then, again, as climate changed as it always does,


  • and new habitats opened up,

    中央アジアに トロゴンテリマンモスという

  • we had the arrival of a steppe-adapted species

    草原帯に適応した 種が生まれ

  • called trogontherii in Central Asia

    メリディオナリスマンモスを 西ヨーロッパに追いやりました

  • pushing meridionalis out into Western Europe.

    ついで北アメリカに 開けたサバンナ地帯ができ

  • And the open grassland savannas of North America

    北アメリカ固有の 巨大な短毛種である

  • opened up, leading to the Columbian mammoth,

    コロンビアマンモスが 生まれたのです

  • a large, hairless species in North America.

    その約50万年後に 長毛種のマンモスが

  • And it was really only about 500,000 years later


  • that we had the arrival of the woolly,

    私たちに とても馴染み深い種ですね

  • the one that we all know and love so much,

    東ベーリング地方から 生息地を広げ

  • spreading from an East Beringian point of origin

    中央アジアを抜け トロゴンテリマンモスを

  • across Central Asia, again pushing the trogontherii

    中央ヨーロッパから 追い払って

  • out through Central Europe,


  • and over hundreds of thousands of years

    ベーリング地峡との 間を往復していました

  • migrating back and forth across the Bering land bridge


  • during times of glacial peaks


  • and coming into direct contact

    コロンビアマンモスと 直接 接触し

  • with the Columbian relatives living in the south,

    この2種が過酷な 気候変動のもと

  • and there they survive over hundreds of thousands of years


  • during traumatic climatic shifts.

    マンモスは気温と環境の 激しい変化に耐えて

  • So there's a highly plastic animal dealing with great transitions

    見事に生き抜く 適応力に 優れた動物です

  • in temperature and environment, and doing very, very well.

    そして大陸では1万年ほど 前まで生きました

  • And there they survive on the mainland until about 10,000 years ago,

    驚くべきことにシベリアと アラスカ沖の

  • and actually, surprisingly, on the small islands off of Siberia

    小さな島々では3千年ほど 前まで生きていたのです

  • and Alaska until about 3,000 years ago.

    エジプトでピラミッドが 建設されていたころ

  • So Egyptians are building pyramids

    これらの島々ではまだ マンモスが生き残っていました

  • and woollies are still living on islands.


  • And then they disappear.

    かつて生きていた動物の 99%のように

  • Like 99 percent of all the animals that have once lived,

    マンモスも絶滅しました 原因は温暖化と

  • they go extinct, likely due to a warming climate


  • and fast-encroaching dense forests


  • that are migrating north,

    かの偉大なポール・マーティンが 提唱したように

  • and also, as the late, great Paul Martin once put it,

    更新世時代に 大型動物を狩猟した人類に

  • probably Pleistocene overkill,

    過剰に殺戮された せいかもしれません

  • so the large game hunters that took them down.

    幸運なことに 現在 数百万の死骸が

  • Fortunately, we find millions of their remains

    シベリアやアラスカの 永久凍土深く

  • strewn across the permafrost buried deep

    至るところに見つかるので 現地に出かけて

  • in Siberia and Alaska, and we can actually go up there


  • and actually take them out.


  • And the preservation is, again,

    琥珀の中の昆虫同様 驚異的です

  • like those insects in [amber], phenomenal.

    歯 血のついた骨

  • So you have teeth, bones with blood

    血は その色までも残しています

  • which look like blood, you have hair,

    体毛 さらには無傷の体や

  • and you have intact carcasses or heads

    脳が入ったままの 頭部も発見されています

  • which still have brains in them.

    DNAの保存状況と 残存状態は

  • So the preservation and the survival of DNA

    多くの要因に依存します 要因の詳細は

  • depends on many factors, and I have to admit,


  • most of which we still don't quite understand,


  • but depending upon when an organism dies

    すぐに土に埋もれたか どのくらい深く埋もれたか

  • and how quickly he's buried, the depth of that burial,

    埋もれた環境の 温度が一定かどうか

  • the constancy of the temperature of that burial environment,

    それらの要因が 地質学的な時間枠の中で

  • will ultimately dictate how long DNA will survive


  • over geologically meaningful time frames.


  • And it's probably surprising to many of you

    重要なのは時間では ありません

  • sitting in this room that it's not the time that matters,

    保存されていた期間でも ありません

  • it's not the length of preservation,

    保存中の温度の安定が 最も重要なのです

  • it's the consistency of the temperature of that preservation that matters most.


  • So if we were to go deep now within the bones


  • and the teeth that actually survived the fossilization process,

    かつては無傷で ヒストンタンパク質に

  • the DNA which was once intact, tightly wrapped


  • around histone proteins, is now under attack

    マンモスが生きていた頃に 共棲していた

  • by the bacteria that lived symbiotically with the mammoth

    バクテリアに 攻撃されています

  • for years during its lifetime.

    これらのバクテリアは 環境中のバクテリアと共に

  • So those bacteria, along with the environmental bacteria,

    水と酸素を奪い DNAを より小さなDNAの破片へと

  • free water and oxygen, actually break apart the DNA


  • into smaller and smaller and smaller DNA fragments,


  • until all you have are fragments that range

    10個の塩基対か 最大でも

  • from 10 base pairs to, in the best case scenarios,


  • a few hundred base pairs in length.

    記録されている 化石の大部分は

  • So most fossils out there in the fossil record

    有機物の痕跡を とどめていません

  • are actually completely devoid of all organic signatures.

    わずかな化石だけが DNAの断片を

  • But a few of them actually have DNA fragments

    数千年 数百万年の

  • that survive for thousands,

    時を隔てて とどめています

  • even a few millions of years in time.

    最先端の クリーンルーム技術を使って

  • And using state-of-the-art clean room technology,

    DNAの断片を 汚れた組織の中から

  • we've devised ways that we can actually pull these DNAs

    取り出す方法を 編み出しました

  • away from all the rest of the gunk in there,

    こんな具合ですから マンモスの骨や歯から

  • and it's not surprising to any of you sitting in the room


  • that if I take a mammoth bone or a tooth

    その時代に共棲していた バクテリアのDNAも混ざっている

  • and I extract its DNA that I'll get mammoth DNA,

    と言っても 皆さんは 驚かれないでしょう

  • but I'll also get all the bacteria that once lived with the mammoth,


  • and, more complicated, I'll get all the DNA

    一緒に生き残った バクテリアや菌類などの

  • that survived in that environment with it,

    不要なDNAを すべて抽出してしまうことです

  • so the bacteria, the fungi, and so on and so forth.

    また永久凍土に保存された マンモスならば

  • Not surprising then again that a mammoth


  • preserved in the permafrost will have something

    マンモスのものですが より温暖な気候に生息し

  • on the order of 50 percent of its DNA being mammoth,


  • whereas something like the Columbian mammoth,

    コロンビアマンモスの場合には DNAの わずか3%から

  • living in a temperature and buried in a temperate environment

    10%だけが マンモス由来のものです

  • over its laying-in will only have 3 to 10 percent endogenous.

    ですが 私たちはマンモスと その他のDNAを

  • But we've come up with very clever ways

    識別し 取り出すという

  • that we can actually discriminate, capture and discriminate,


  • the mammoth from the non-mammoth DNA,


  • and with the advances in high-throughput sequencing,


  • we can actually pull out and bioinformatically

    マンモスDNAの小さな破片を 再編して

  • re-jig all these small mammoth fragments

    アジアゾウやアフリカゾウの 染色体の構造に

  • and place them onto a backbone

    重ねることが できるようになりました

  • of an Asian or African elephant chromosome.

    この方法で マンモスとアジアゾウを

  • And so by doing that, we can actually get all the little points

    区別する点をすべて 把握することができました

  • that discriminate between a mammoth and an Asian elephant,

    ではマンモスについて 何がわかったのでしょうか?

  • and what do we know, then, about a mammoth?

    マンモスのゲノムは ほぼすべて解読されました

  • Well, the mammoth genome is almost at full completion,


  • and we know that it's actually really big. It's mammoth.

    ヒト科のゲノムは 約30億塩基対ですが

  • So a hominid genome is about three billion base pairs,


  • but an elephant and mammoth genome

    さらに20億の 塩基対ぶん大きく

  • is about two billion base pairs larger, and most of that

    その多くが小さな反復配列 DNAで構成されていて

  • is composed of small, repetitive DNAs

    これがゲノム全体の 再構築を難しくしています

  • that make it very difficult to actually re-jig the entire structure of the genome.


  • So having this information allows us to answer

    マンモスと 現存する アジアゾウと

  • one of the interesting relationship questions

    アフリカゾウの 縁戚関係に関する

  • between mammoths and their living relatives,

    興味深い疑問に 答えることができました

  • the African and the Asian elephant,

    3種は約700万年前に 共通の祖先を持っていました

  • all of which shared an ancestor seven million years ago,

    さらに約600万年前までは アジアゾウと

  • but the genome of the mammoth shows it to share

    祖先を共通していたことが マンモスのゲノムから

  • a most recent common ancestor with Asian elephants


  • about six million years ago,

    マンモスはアジアゾウと より近縁です

  • so slightly closer to the Asian elephant.

    古代のDNAの 解析技術の進歩により

  • With advances in ancient DNA technology,

    他のマンモスたちの ゲノムの配列も

  • we can actually now start to begin to sequence


  • the genomes of those other extinct mammoth forms that I mentioned,

    そのうちの2つについて お話しします

  • and I just wanted to talk about two of them,

    毛長マンモスと コロンビアマンモスです

  • the woolly and the Columbian mammoth,

    この2種は氷河期の 最寒期に

  • both of which were living very close to each other

    ごく近接して 生息していました