When I was a young boy, I used to gaze through the microscope of my father at the insects in amber that he kept in the house. And they were remarkably well preserved, morphologically just phenomenal. And we used to imagine that someday, they would actually come to life and they would crawl out of the resin, and, if they could, they would fly away.
當我還小的時候 常常透過父親房間裡的顯微鏡 觀察琥珀裡的昆蟲 牠們保存得非常完好 其完好程度簡直令人驚奇 而且我們過去常想像 是不是有一天牠們會甦醒 然後會從樹脂裡爬出來 如果牠們能飛的話 牠們是不是會飛走
If you had asked me 10 years ago whether or not we would ever be able to sequence the genome of extinct animals, I would have told you, it's unlikely. If you had asked whether or not we would actually be able to revive an extinct species, I would have said, pipe dream. But I'm actually standing here today, amazingly, to tell you that not only is the sequencing of extinct genomes a possibility, actually a modern-day reality, but the revival of an extinct species is actually within reach, maybe not from the insects in amber -- in fact, this mosquito was actually used for the inspiration for "Jurassic Park" — but from woolly mammoths, the well preserved remains of woolly mammoths in the permafrost.
如果十年前你問我 我們能不能把滅絕動物的基因組排序 我會告訴你,不太可能 如果你問我們能不能 使滅絕的生物復活 我會說,做白日夢吧 吃驚的是,今天我實實在在的站在這兒 告訴大家,絕種動物基因組排序是可能的 事實上這已成為現實 復活滅絕動物的可能性已是能力所及 但可能不是復活琥珀裡的昆蟲 - - 這隻蚊子曾是「侏羅紀公園」的靈感來源 - - - - 這隻蚊子曾是「侏羅紀公園」的靈感來源 - - 而是通過凍土裡保存完好的殘骸 復活長毛象
Woollies are a particularly interesting, quintessential image of the Ice Age. They were large. They were hairy. They had large tusks, and we seem to have a very deep connection with them, like we do with elephants. Maybe it's because elephants share many things in common with us. They bury their dead. They educate the next of kin. They have social knits that are very close. Or maybe it's actually because we're bound by deep time, 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 into Europe and Asia.
長毛象是冰河時期特別有趣、特別典型的象徵 長毛像是冰河時期特別有趣、特別典型的象徵 牠們體型巨大,身披長毛 有很大的長牙 我們好像和牠們關係密切 就像我們和大象一樣 可能因為大象和我們 有許多共同點 比如埋葬死者,教育後代 有很緊密的社交聯繫 或者可能因為我們在遠古時期就有聯繫 因為大象和我們人類一樣 七百多萬年前起源於非洲 隨著棲地和環境變化 我們人類和大象一樣 遷移到歐洲和亞洲
So the first large mammoth that appears on the scene is meridionalis, which was standing four meters tall weighing about 10 tons, and was a woodland-adapted species and spread from Western Europe clear across Central Asia, across the Bering land bridge and into parts of North America. And then, again, as climate changed as it always does, and new habitats opened up, we had the arrival of a steppe-adapted species called trogontherii in Central Asia pushing meridionalis out into Western Europe. And the open grassland savannas of North America opened up, leading to the Columbian mammoth, a large, hairless species in North America. And it was really only about 500,000 years later that we had the arrival of the woolly, the one that we all know and love so much, spreading from an East Beringian point of origin across Central Asia, again pushing the trogontherii out through Central Europe, and over hundreds of thousands of years migrating back and forth across the Bering land bridge during times of glacial peaks and coming into direct contact with the Columbian relatives living in the south, and there they survive over hundreds of thousands of years during traumatic climatic shifts. So there's a highly plastic animal dealing with great transitions in temperature and environment, and doing very, very well. And there they survive on the mainland until about 10,000 years ago, and actually, surprisingly, on the small islands off of Siberia and Alaska until about 3,000 years ago. So Egyptians are building pyramids and woollies are still living on islands.
遠古出現的第一種猛獁象是南方猛獁 身高四米,體重約十噸 適宜在森林中生存 分佈在西歐地區、中亞地區 並跨過白令陸橋 到達北美部分地區 之後,隨著氣候再次變化 新棲地出現 便有了適宜在草原生存的種類 即中亞地區的草原猛獁 牠們把南方猛獁排擠到了西歐地區 北美廣大的稀樹大草原出現後 便有了哥倫比亞猛獁 牠們體型巨大,沒有長毛,分佈在北美 大約在五十萬年之後 我們非常喜愛和了解的長毛猛獁才出現 我們非常喜愛和了解的長毛猛獁才出現 牠們由白令海峽分布至中亞區域 又把草原猛獁排擠到了中歐地區 又把草原猛獁排擠到了中歐地區 在數百萬年過程中 牠們反覆在冰河時期 橫跨白令陸橋 和生活在南方的哥倫比亞猛獁 有了直接聯繫 牠們在那兒生存了數百萬年 忍受嚴峻的氣候突變 所以這種生存能力極強的動物 對溫度和環境的劇烈轉變 適應得非常好 牠們在內陸生活直到一萬年前 出人意料的,約三千年前 在西伯利亞外海的小島上 仍有它們的足跡 當埃及人在建金字塔時 長毛象仍生活在海島上
And then they disappear. Like 99 percent of all the animals that have once lived, they go extinct, likely due to a warming climate and fast-encroaching dense forests that are migrating north, and also, as the late, great Paul Martin once put it, probably Pleistocene overkill, so the large game hunters that took them down.
之後牠們就消失了 正如世界上 99% 動物一樣 牠們也滅絕了 可能是由於氣溫升高 和迅速往北覆蓋的茂密的森林 同樣可能是像已故保羅·馬丁曾說的那樣 由於更新世時的人類獵殺 所以是大型動物捕殺者讓牠們滅絕了
Fortunately, we find millions of their remains strewn across the permafrost buried deep in Siberia and Alaska, and we can actually go up there and actually take them out. And the preservation is, again, like those insects in [amber], phenomenal. So you have teeth, bones with blood which look like blood, you have hair, and you have intact carcasses or heads which still have brains in them.
我們幸運地發現了許多殘骸 深埋在西伯利亞和阿拉斯加的凍土中 我們可以到那些地方去 把它們挖出來 其保存完好程度 像琥珀裡的昆蟲一樣令人驚奇 有牙齒,帶血的骨頭 至少看起來還像血 還有毛髮 而且有完整的屍體和頭顱 頭顱內仍有腦髓
So the preservation and the survival of DNA 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 and how quickly he's buried, the depth of that burial, the constancy of the temperature of that burial environment, will ultimately dictate how long DNA will survive over geologically meaningful time frames. And it's probably surprising to many of you sitting in this room that it's not the time that matters, it's not the length of preservation, it's the consistency of the temperature of that preservation that matters most.
其保存完好程度和 DNA 的存活 取決於很多方面,而我必須承認 其中仍有很多我們不理解 但當生物體死亡時 其被埋葬的速度、深度 埋葬環境的氣溫穩定度 會從根本上決定 DNA 在地質學時間範疇內 存活的時間長短 可能會令在座各位感到意外的是 其實埋葬年代並不重要 保存時間長短也不重要 最重要的是保存環境的氣溫穩定性
So if we were to go deep now within the bones and the teeth that actually survived the fossilization process, the DNA which was once intact, tightly wrapped around histone proteins, is now under attack by the bacteria that lived symbiotically with the mammoth for years during its lifetime. So those bacteria, along with the environmental bacteria, 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 from 10 base pairs to, in the best case scenarios, a few hundred base pairs in length. So most fossils out there in the fossil record are actually completely devoid of all organic signatures. But a few of them actually have DNA fragments that survive for thousands, even a few millions of years in time. And using state-of-the-art clean room technology, we've devised ways that we can actually pull these DNAs away from all the rest of the gunk in there, and it's not surprising to any of you sitting in the room that if I take a mammoth bone or a tooth and I extract its DNA that I'll get mammoth DNA, but I'll also get all the bacteria that once lived with the mammoth, and, more complicated, I'll get all the DNA that survived in that environment with it, so the bacteria, the fungi, and so on and so forth. Not surprising then again that a mammoth preserved in the permafrost will have something on the order of 50 percent of its DNA being mammoth, whereas something like the Columbian mammoth, living in a temperature and buried in a temperate environment over its laying-in will only have 3 to 10 percent endogenous.
如果我們深入研究 在石化過程中倖存的骨頭和牙齒 曾被組織蛋白緊緊包裹著的 DNA 曾被組織蛋白緊緊包裹著的 DNA 現在面臨猛獁體內的共生細菌攻擊 現在面臨猛獁體內的共生細菌攻擊 所以這些細菌、環境中的細菌 游離水和氧氣把 DNA 分裂成細小碎片 游離水和氧氣把 DNA 分裂成細小碎片 這些碎片裡最小的是10 鹼基對 在最好的情況下 可能有長度為幾百鹼基對的碎片 所以化石記錄裡的大多數化石 都完全缺乏有機特徵 但仍有一些 DNA 碎片 存活了上千年 甚至上百萬年 通過最先進的無菌科技 我們已經找出了幾種 可以從殘骸中萃取出 DNA 的方法 而且,在座應沒有人會感到意外 即使我能在猛獁象骨頭或牙齒裡 提取出猛獁象 DNA 也會隨之提取出所有和猛獁共生的細菌 再麻煩的是,我還會提取出 當時環境中所有存活下來的 DNA 像是細菌、真菌等等 所以保存在凍土裡的猛獁象 僅有 50% 屬於猛獁 DNA 同樣不令人意外 而哥倫比亞猛獁 生活及埋葬的環境屬溫帶氣候 這讓其 DNA 只有 3% 到 10% 的內生性
But we've come up with very clever ways 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 re-jig all these small mammoth fragments and place them onto a backbone of an Asian or African elephant chromosome. And so by doing that, we can actually get all the little points that discriminate between a mammoth and an Asian elephant, and what do we know, then, about a mammoth?
但我們已經找到一些巧妙的方法 藉此我們可以捕捉和區分 猛獁 DNA 和非猛獁 DNA 並經由最先進的高通量基因組測序技術 提出這些猛獁 DNA 碎片 利用生物資訊技術 將之重新排列於 亞洲象或非洲象的基因組骨幹上 這樣我們就能得到 所有區分猛獁象和亞洲象的基因變異 所以我們對猛獁象了解多少呢?
Well, the mammoth genome is almost at full completion, and we know that it's actually really big. It's mammoth. So a hominid genome is about three billion base pairs, but an elephant and mammoth genome is about two billion base pairs larger, and most of that is composed of small, repetitive DNAs that make it very difficult to actually re-jig the entire structure of the genome.
猛獁象基因組快趨於完整了 我們知道這個基因組非常巨大 原始人類的基因組大概有 30 億鹼基對 但是大象或猛獁象的鹼基對 比人類基因組多出 20 億鹼基對 大多數是重複的短 DNA 片段 因此重新排列這個基因組結構非常困難
So having this information allows us to answer one of the interesting relationship questions between mammoths and their living relatives, the African and the Asian elephant, all of which shared an ancestor seven million years ago, but the genome of the mammoth shows it to share a most recent common ancestor with Asian elephants about six million years ago, so slightly closer to the Asian elephant.
這些資訊讓我們能夠回答 一個跟猛獁象與其現代近親 非洲象和亞洲象 有關的有趣問題了 七百萬年前,牠們有一個共同的祖先 但是猛獁的基因組顯示 猛獁和亞洲象最近的共同祖先 是在六百萬年前 所以猛獁和亞洲象比較親近
With advances in ancient DNA technology, we can actually now start to begin to sequence the genomes of those other extinct mammoth forms that I mentioned, and I just wanted to talk about two of them, the woolly and the Columbian mammoth, both of which were living very close to each other during glacial peaks, so when the glaciers were massive in North America, the woollies were pushed into these subglacial ecotones, and came into contact with the relatives living to the south, and there they shared refugia, and a little bit more than the refugia, it turns out. It looks like they were interbreeding. And that this is not an uncommon feature in Proboscideans, because it turns out that large savanna male elephants will outcompete the smaller forest elephants for their females. So large, hairless Columbians outcompeting the smaller male woollies. It reminds me a bit of high school, unfortunately.
拜近來純熟的古 DNA 技術之賜 我們現在可以開始排序 那些其他已滅絕猛獁的基因組 我只想說其中兩種 長毛象和哥倫比亞猛獁 這兩種猛獁在冰河時期生活得非常近 這兩種猛獁在冰河時期生活得非常近 當北美的冰河規模非常大時 長毛象被迫遷徙到冰河過渡帶 開始和生活在南方的親戚接觸 共同分享避難處 後來發現,牠們不只分享避難處 牠們並與南方的猛瑪雜交 這對長鼻目動物來說不稀奇 因為後來發現 大型熱帶草原雄象在追求雌象時 會打敗體型較小的叢林象 所以體型巨大且沒毛的哥倫比亞猛獁 打敗了體型較小的雄性長毛象 這讓我想起了我的高中生活
(Laughter)
(笑聲)
So this is not trivial, given the idea that we want to revive extinct species, because it turns out that an African and an Asian elephant can actually interbreed and have live young, and this has actually occurred by accident in a zoo in Chester, U.K., in 1978. So that means that we can actually take Asian elephant chromosomes, modify them into all those positions we've actually now been able to discriminate with the mammoth genome, we can put that into an enucleated cell, differentiate that into a stem cell, subsequently differentiate that maybe into a sperm, artificially inseminate an Asian elephant egg, and over a long and arduous procedure, actually bring back something that looks like this. Now, this wouldn't be an exact replica, because the short DNA fragments that I told you about will prevent us from building the exact structure, but it would make something that looked and felt very much like a woolly mammoth did.
假如我們想要復活滅絕的物種 這就很重要了 因為亞洲象和非洲象 能通過雜交繁衍後代 1978 年在英國切斯特的一個動物園裡 曾意外發生過這種事 這意味著我們可以用亞洲象染色體 並把它於我們發現的基因位置 修改成猛獁基因組 然後放到無核細胞中 讓它分化為幹細胞 可能最後會分化為精子 再人工植入亞洲象卵子 經過漫長艱苦的過程後 就會產生一個這樣的動物 這並不會是一個準確的複製長毛象 因為我剛才提到的 DNA 重複片段 會妨礙我們創造一個精確的複製品 但是看起來和感覺起來 會很像一個真實的長毛象
Now, when I bring up this with my friends, we often talk about, well, where would you put it? Where are you going to house a mammoth? There's no climates or habitats suitable. Well, that's not actually the case. It turns out that there are swaths of habitat in the north of Siberia and Yukon that actually could house a mammoth. Remember, this was a highly plastic animal that lived over tremendous climate variation. So this landscape would be easily able to house it, and I have to admit that there [is] a part of the child in me, the boy in me, that would love to see these majestic creatures walk across the permafrost of the north once again, but I do have to admit that part of the adult in me sometimes wonders whether or not we should.
當我向朋友們討論這個的時候 我們總談到,那你把牠放哪裡啊? 你會讓一頭猛獁象住哪裡? 根本沒有合適的氣候和棲地 其實並非如此 因為在西伯利亞北部和育空地區 有足夠的合適棲地 能夠提供猛獁生活 請記住,猛獁是適應力極強的動物 牠們經歷過驚人的氣候變化 所以這片地區會很適宜牠們生活 我必須承認,我內心中的小男孩 我必須承認,我內心中的小男孩 渴望看到這偉大的生物 再次行走在北方的凍土上 但是我必須承認,成熟的我有時會想 我們到底是不是該把牠們復活
Thank you very much.
謝謝
(Applause)
(掌聲)
Ryan Phelan: Don't go away. You've left us with a question. I'm sure everyone is asking this. When you say, "Should we?" it feels like you're reticent there, and yet you've given us a vision of it being so possible. What's your reticence?
Ryan Phelan: 先別走 你給我們留下了一個疑問 我保證大家都會問這個問題 當你說「該不該」時 我感覺你有所保留 但你已告訴我們復活猛獁的可能性 你在遲疑什麼?
Hendrik Poinar: I don't think it's reticence. I think it's just that we have to think very deeply about the implications, ramifications of our actions, and so as long as we have good, deep discussion like we're having now, I think we can come to a very good solution as to why to do it. But I just want to make sure that we spend time thinking about why we're doing it first.
H. Poinar: 我不認為那是遲疑 我覺得我們必須仔細考慮 我們這個行為的後果和影響 只要我們經過真誠深刻的討論之後 就像我們現在這樣,我覺得 我們就能找到一個解決方案 但是我只是想確定我們得先花時間 考慮我們復活猛瑪的理由
RP: Perfect. Perfect answer. Thank you very much, Hendrik.
RP: 完美的答案 謝謝,Hendrik
HP: Thank you. (Applause)
HP: 謝謝 (掌聲)