TEDGlobal 2011
Svante Pääbo: DNA clues to our inner neanderthal
Svante Paabo：人體內之尼安德塔人基因線索
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遺傳學家Svante Paabo分享規模遍及全球的研究成果，並說明早期人類在離開非洲後和尼安德塔人交配的DNA證據（是的，大部份的我們有尼安德塔人的DNA）。他也說明由一塊幼兒指頭小小殘骸如何足以辨識出一個前未發現的新人種。
Svante Pääbo - Geneticist
Svante Pääbo explores human genetic evolution by analyzing DNA extracted from ancient sources, including mummies, an Ice Age hunter and the bone fragments of Neanderthals. Full bio
Svante Pääbo explores human genetic evolution by analyzing DNA extracted from ancient sources, including mummies, an Ice Age hunter and the bone fragments of Neanderthals. Full bio
Double-click the English transcript below to play the video.
00:15
What I want to talk to you about
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我想要談的是
00:18
is what we can learn from studying the genomes
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我們從研究
00:20
of living people
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活著的人
00:22
and extinct humans.
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和滅絕人種的基因組中可以學到什麼。
00:24
But before doing that,
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但在那之前，
00:26
I just briefly want to remind you about what you already know:
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我要提醒你們一些你們已經知道的事：
00:29
that our genomes, our genetic material,
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我們的基因組，我們的基因物質，
00:31
are stored in almost all cells in our bodies in chromosomes
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存在於我們身上幾乎所有細胞內的染色體中，
00:34
in the form of DNA,
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以DNA的形式存在，
00:36
which is this famous double-helical molecule.
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即著名的雙重螺旋分子結構。
00:39
And the genetic information
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而且這些基因資料
00:41
is contained in the form of a sequence
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是以四種簡稱為
00:43
of four bases
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Ａ、Ｔ、Ｃ、Ｇ的鹼基
00:45
abbreviated with the letters A, T, C and G.
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組成的序列。
00:48
And the information is there twice --
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基因資料有兩組──
00:50
one on each strand --
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一股(線)上一組──
00:52
which is important,
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這點很重要，
00:54
because when new cells are formed, these strands come apart,
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因為當新細胞形成時，DNA的雙股會分開，
00:56
new strands are synthesized with the old ones as templates
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單股各自為模板，與(複製出的)新股合成為兩條雙股DNA
00:59
in an almost perfect process.
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這是一個近乎完美的複製過程。
01:02
But nothing, of course, in nature
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當然!自然界沒有任何東西
01:04
is totally perfect,
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是完美無瑕的。
01:06
so sometimes an error is made
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因此有時會出錯而
01:08
and a wrong letter is built in.
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置入錯誤的字母(鹼基)。
01:11
And we can then see the result
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舉例來說，當我們比較
01:13
of such mutations
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演說廳內所有人的DNA序列，
01:15
when we compare DNA sequences
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我們就會看到
01:17
among us here in the room, for example.
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這類突變的結果。
01:20
If we compare my genome to the genome of you,
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拿我的基因組跟你們的比較，
01:23
approximately every 1,200, 1,300 letters
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在我們之中，大約每1,200或1,300個鹼基
01:27
will differ between us.
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就會出現不同之處。
01:29
And these mutations accumulate
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而且這些突變
01:31
approximately as a function of time.
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有大概的週期，隨歲月不斷積累。
01:34
So if we add in a chimpanzee here, we will see more differences.
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所以若加入黑猩猩來比對，差異又更大了。
01:37
Approximately one letter in a hundred
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大約每一百個字母(鹼基)就有一個
01:40
will differ from a chimpanzee.
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跟大猩猩不同。
01:42
And if you're then interested in the history
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而且若你對一段DNA
01:44
of a piece of DNA, or the whole genome,
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或是整個基因組的進化史有興趣的話，
01:46
you can reconstruct the history of the DNA
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可以利用這些觀測到的差異
01:49
with those differences you observe.
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來重現DNA的進化史。
01:51
And generally we depict our ideas about this history
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一般我們以這樣的樹狀圖
01:55
in the form of trees like this.
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來繪製我們對進化史的概念。
01:57
In this case, it's very simple.
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以這個例子來說，就是個簡單的例子。
01:59
The two human DNA sequences
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這兩個人類DNA序列
02:01
go back to a common ancestor quite recently.
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可追溯到最近的同源祖先。
02:04
Farther back is there one shared with chimpanzees.
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時間再往回推，就可推出和黑猩猩有同源祖先。
02:08
And because these mutations
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而且因為這些突變的發生
02:11
happen approximately as a function of time,
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可依時間作大概推算，
02:13
you can transform these differences
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你們可以把這些差異
02:15
to estimates of time,
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轉換成估算的時間，
02:17
where the two humans, typically,
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一般而論，這兩個人類
02:19
will share a common ancestor about half a million years ago,
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可被推算出在大約五十萬年前有同源祖先，
02:23
and with the chimpanzees,
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跟黑猩猩的話，
02:25
it will be in the order of five million years ago.
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推算出的時間是在五百萬年前左右。
02:28
So what has now happened in the last few years
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這麼說吧，這些年來發生的事──
02:30
is that there are account technologies around
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精密科技的問世
02:32
that allow you to see many, many pieces of DNA very quickly.
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讓我們得以非常快速地檢視很多、很多的DNA。
02:36
So we can now, in a matter of hours,
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所以僅僅幾個小時，我們就可以
02:38
determine a whole human genome.
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檢測出全套人類基因組。
02:41
Each of us, of course, contains two human genomes --
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當然人類每個個體都有兩組基因組：
02:44
one from our mothers and one from our fathers.
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一組來自母親，一組來自父親。
02:47
And they are around three billion such letters long.
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而且約三十億字母(鹼基)的長度。
02:51
And we will find that the two genomes in me,
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大家會在我身上找到兩組基因組，
02:53
or one genome of mine we want to use,
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我們拿其中一組基因組來檢驗，
02:55
will have about three million differences
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約有三百萬不同之處
02:58
in the order of that.
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大概是這個數字。
03:00
And what you can then also begin to do
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然後你也可以開始研究
03:02
is to say, "How are these genetic differences
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這些基因的差異
03:04
distributed across the world?"
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在這世界的分佈情形。
03:06
And if you do that,
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而且若這麼做，
03:08
you find a certain amount of genetic variation in Africa.
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你會發現在非洲有某一數量的基因變異(突變)。
03:12
And if you look outside Africa,
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若你研究非洲以外的地區，
03:15
you actually find less genetic variation.
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你觀察到的基因變異較少。
03:18
This is surprising, of course,
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奇怪吧!
03:20
because in the order of six to eight times fewer people
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因為在非洲的人比在非洲外的人
03:23
live in Africa than outside Africa.
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少了約七、八倍。
03:26
Yet the people inside Africa
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然而非洲內的人
03:29
have more genetic variation.
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發生更多的基因變異(突變)
03:32
Moreover, almost all these genetic variants
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況且，我們在非洲外發現
03:34
we see outside Africa
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幾乎所有基因變異
03:36
have closely related DNA sequences
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與在非洲內找到的DNA序列
03:38
that you find inside Africa.
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有密切關係。
03:40
But if you look in Africa,
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但若你們看看非洲內，
03:42
there is a component of the genetic variation
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有處基因變異
03:45
that has no close relatives outside.
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在非洲外完全沒有相近的排列。
03:48
So a model to explain this
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那麼可以解釋這個的模式是
03:51
is that a part of the African variation, but not all of it,
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部分基因變異的非洲人，而非全基因變異人口，
03:54
[has] gone out and colonized the rest of the world.
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移居到地球其他地方。
03:58
And together with the methods to date these genetic differences,
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再加上利用基因差異斷定時間的技術，
04:02
this has led to the insight
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讓我們對現代人類
04:04
that modern humans --
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有這樣的了解：
04:06
humans that are essentially indistinguishable from you and me --
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根本上難分你我的人類
04:09
evolved in Africa, quite recently,
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是最近約十萬至二十萬年前
04:12
between 100 and 200,000 years ago.
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在非洲進化而來的。
04:16
And later, between 100 and 50,000 years ago or so,
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稍後約五萬到十萬年前
04:20
went out of Africa
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離開非洲
04:22
to colonize the rest of the world.
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到世界其他地方殖民。
04:24
So what I often like to say
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所以我常喜歡說
04:26
is that, from a genomic perspective,
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以基因組的觀點來看，
04:28
we are all Africans.
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我們都是非洲人。
04:30
We either live inside Africa today,
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我們不是現今住在非洲內
04:33
or in quite recent exile.
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就是最近出走非洲的那群。
04:35
Another consequence
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另一個現代人類的
04:37
of this recent origin of modern humans
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最近起源的推論是
04:40
is that genetic variants
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基因變異
04:42
are generally distributed widely in the world,
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廣泛地分佈在全球
04:44
in many places,
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各個地方，
04:46
and they tend to vary as gradients,
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而且以全版面的角度來看
04:49
from a bird's-eye perspective at least.
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往往呈梯度變化。
04:53
And since there are many genetic variants,
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由於有很多基因變異，
04:55
and they have different such gradients,
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就有不同的梯度變化，
04:58
this means that if we determine a DNA sequence --
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這意味著若我們可以測出DNA序列──
05:01
a genome from one individual --
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個體的基因組──
05:04
we can quite accurately estimate
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我們可以相當準確地判斷
05:06
where that person comes from,
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這個人是從哪裡來的，
05:08
provided that its parents or grandparents
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若其父母或祖父母
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haven't moved around too much.
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沒有經常四處遷徙。
05:13
But does this then mean,
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但這是不是表示
05:15
as many people tend to think,
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如很多人想的那樣
05:17
that there are huge genetic differences between groups of people --
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不同族群的人，基因差異很大，
05:20
on different continents, for example?
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是不是不同洲的人差異會更大?
05:22
Well we can begin to ask those questions also.
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嗯，我們也可以開始問這樣的問題。
05:25
There is, for example, a project that's underway
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舉個例子，有個計畫在執行中
05:28
to sequence a thousand individuals --
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要為世界不同地方的一千個人
05:30
their genomes -- from different parts of the world.
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排列基因組。
05:33
They've sequenced 185 Africans
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研究人員已經在非洲兩個族群中
05:36
from two populations in Africa.
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完成185個人的DNA序列。
05:39
[They've] sequenced approximately equally [as] many people
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在歐洲和在中國已排出序列的
05:42
in Europe and in China.
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人數也大概同樣多。
05:45
And we can begin to say how much variance do we find,
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那麼我們便可開始指出找到多少基因變異，
05:48
how many letters that vary
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在這些個體DNA排序中，
05:51
in at least one of those individual sequences.
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單一個人的鹼基有多少變化。
05:54
And it's a lot: 38 million variable positions.
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答案是很多：有三千八百萬個變異處。
05:58
But we can then ask: Are there any absolute differences
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但我們也可以問：非洲人和非非洲人
06:01
between Africans and non-Africans?
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有任何完全差異嗎?
06:03
Perhaps the biggest difference
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也許我們大部份的人會想到的
06:05
most of us would imagine existed.
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最大差異曾經存在過。
06:07
And with absolute difference --
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而「完全差異」
06:09
and I mean a difference
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我所指的差異是
06:11
where people inside Africa at a certain position,
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非洲內的人在某個「特定位置」，
06:14
where all individuals -- 100 percent -- have one letter,
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「百分之百」有「相同的字母(鹼基)」，
06:17
and everybody outside Africa has another letter.
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而每個在非洲外的人則有「另一個字母(鹼基)」。
06:21
And the answer to that, among those millions of differences,
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這個問題的答案是，數百萬的差異之中，
06:24
is that there is not a single such position.
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沒有這樣一個「完全差異」的位置。
06:29
This may be surprising.
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這也許出人意料。
06:31
Maybe a single individual is misclassified or so.
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也許有某個人的序列被弄錯了。
06:34
So we can relax the criterion a bit
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所以我們可以稍稍放寬條件來問：
06:36
and say: How many positions do we find
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我們發現有多少位置是
06:38
where 95 percent of people in Africa have
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95%非洲內的人
06:40
one variant,
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有「相同變異」，
06:42
95 percent another variant,
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而在同樣的位置，95%非洲境外人則有「另一變異」，
06:44
and the number of that is 12.
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得到的數字是12。
06:46
So this is very surprising.
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所以很意外吧
06:48
It means that when we look at people
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這意味著當我們看著人群，
06:50
and see a person from Africa
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看到某個來自非洲的人、
06:53
and a person from Europe or Asia,
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看到某個來自歐洲或亞州的人，
06:56
we cannot, for a single position in the genome with 100 percent accuracy,
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我們不能百分之百說中
07:00
predict what the person would carry.
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「某人」基因組之「某處」具有「何種鹼基」。
07:02
And only for 12 positions
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而且只有12個位置
07:04
can we hope to be 95 percent right.
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我們能期望有九成五的正確率。
07:08
This may be surprising,
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這也許令人驚訝。
07:10
because we can, of course, look at these people
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我們當然可以用肉眼盯著這些人
07:12
and quite easily say where they or their ancestors came from.
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並相當容易地分辨他們或其祖先從哪裡來。
07:16
So what this means now
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也就是說
07:18
is that those traits we then look at
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我們看到的這些特徵
07:20
and so readily see --
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是很容易就看得到的──
07:22
facial features, skin color, hair structure --
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相貌特色、髮色質量、皮膚顏色──
07:25
are not determined by single genes with big effects,
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並非由各類單一、重要的基因決定其作用，
07:29
but are determined by many different genetic variants
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而是由很多不同的基因變異決定，
07:32
that seem to vary in frequency
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且這些變異似乎在世界各地
07:34
between different parts of the world.
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發生的頻率(次數)也不同。
07:36
There is another thing with those traits
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另外一件事與我們可以很容易地
07:39
that we so easily observe in each other
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在彼此身上看得到的特徵有關。
07:42
that I think is worthwhile to consider,
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我認為值得想想，
07:44
and that is that, in a very literal sense,
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就字義來說，
07:47
they're really on the surface of our bodies.
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這些特徵的確是在我們身體表面。
07:50
They are what we just said --
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如我剛剛說的
07:52
facial features, hair structure, skin color.
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相貌特色、髮色質量、皮膚顏色。
07:55
There are also a number of features
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然而各洲間還存有諸如此類的不同特色
07:57
that vary between continents like that
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可說是不勝枚舉，
07:59
that have to do with how we metabolize food that we ingest,
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像是我們如何代謝我們吃進去的食物
08:03
or that have to do
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或是
08:05
with how our immune systems deal with microbes
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我們的免疫系統如何應付
08:08
that try to invade our bodies.
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企圖侵犯我們身體的病菌。
08:10
But so those are all parts of our bodies
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然而這些是我們身體的各部
08:12
where we very directly interact with our environment,
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直接與周圍環境互動，
08:15
in a direct confrontation, if you like.
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你也可以說是「正面對峙」。
08:19
It's easy to imagine
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很容易想像
08:21
how particularly those parts of our bodies
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何以身體特定的某些部份
08:23
were quickly influenced by selection from the environment
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一受到「環境淘汰(選擇)」威脅
08:26
and shifted frequencies of genes
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就轉換這些受環境衝擊
08:28
that are involved in them.
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的基因頻率。
08:30
But if we look on other parts of our bodies
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但若我們看身體其他
08:33
where we don't directly interact with the environment --
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不直接與環境互動的部份，
08:35
our kidneys, our livers, our hearts --
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我們的腎臟、肝臟、心臟，
08:38
there is no way to say,
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就很難
08:40
by just looking at these organs,
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憑這些器官
08:42
where in the world they would come from.
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判斷他們來自世界的何處。
08:46
So there's another interesting thing
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所以有這層了解，我們發現
08:48
that comes from this realization
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另一件有趣的事
08:51
that humans have a recent common origin in Africa,
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人類最近共同的起源在非洲，
08:55
and that is that when those humans emerged
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而且當時這些人類出現
08:58
around 100,000 years ago or so,
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距今大約十萬年前，
09:00
they were not alone on the planet.
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他們並不是單獨存在地球上。
09:02
There were other forms of humans around,
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那時候有其他人種存在，
09:05
most famously perhaps, Neanderthals --
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最有名的大概是「尼安德塔人」──
09:08
these robust forms of humans,
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在左邊
09:10
compared to the left here
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較健壯的人型，
09:12
with a modern human skeleton on the right --
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右邊的是現代人類骨骼──
09:16
that existed in Western Asia and Europe
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在幾十萬年前
09:19
since several hundreds of thousands of years.
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就生活在西亞和歐洲。
09:21
So an interesting question is,
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所以有個有趣的問題，
09:23
what happened when we met?
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那時我們相遇，發生了什麼事?
09:25
What happened to the Neanderthals?
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尼安德塔人怎麼了?
09:27
And to begin to answer such questions,
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為了回答這樣的問題，
09:29
my research group -- since over 25 years now --
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我的研究團隊在過去25年來
09:33
works on methods to extract DNA
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研究如何從尼安德塔人
09:35
from remains of Neanderthals
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和絕種動物
09:37
and extinct animals
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的幾萬年遺骸
09:39
that are tens of thousands of years old.
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萃取DNA。
09:42
So this involves a lot of technical issues
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所以這牽涉到許多技術性問題
09:45
in how you extract the DNA,
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像是如何萃取DNA，
09:47
how you convert it to a form you can sequence.
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如何把它轉化成可以排序的形式。
09:50
You have to work very carefully
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操作必須非常小心謹慎
09:52
to avoid contamination of experiments
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以避免自己造成的
09:55
with DNA from yourself.
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實驗污染DNA。
09:58
And this then, in conjunction with these methods
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結合這些可以快速
10:01
that allow very many DNA molecules to be sequenced very rapidly,
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排列出大量DNA分子的方法
10:05
allowed us last year
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讓我們在去年
10:07
to present the first version of the Neanderthal genome,
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得以呈現首版尼安德塔人基因組，
10:10
so that any one of you
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所以你們任何人
10:12
can now look on the Internet, on the Neanderthal genome,
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都可以在網路上找到尼安德塔人基因組，
10:14
or at least on the 55 percent of it
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或至少看得到目前能重現的
10:17
that we've been able to reconstruct so far.
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55%尼安德塔人基因組。
10:20
And you can begin to compare it to the genomes
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你們可以開始將之
10:22
of people who live today.
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與現今活著的人類基因組做比較。
10:25
And one question
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接著你們也許
10:27
that you may then want to ask
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想問一個問題
10:29
is, what happened when we met?
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現代人類和尼安德塔人相遇時，發生什麼事?
10:31
Did we mix or not?
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有沒有混種？
10:33
And the way to ask that question
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提問的科學路徑是
10:35
is to look at the Neanderthal that comes from Southern Europe
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去看南歐出土的尼安德塔人之基因組
10:38
and compare it to genomes
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然後將其基因組
10:40
of people who live today.
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與現今活著的人類作比對。
10:42
So we then look
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所以我們接著
10:44
to do this with pairs of individuals,
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分析一對對的個體
10:46
starting with two Africans,
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以兩個非洲人開始，
10:48
looking at the two African genomes,
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看這兩個非洲人的基因組，
10:50
finding places where they differ from each other,
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找出他們互不相同的地方，
10:53
and in each case ask: What is a Neanderthal like?
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並在每個案例中提問：尼安德塔人是怎麼樣的人?
10:56
Does it match one African or the other African?
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其基因組與這個非洲人吻合或是另一個?
10:59
We would expect there to be no difference,
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研究人員會預期沒有任何差異，
11:02
because Neanderthals were never in Africa.
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因為尼安德塔人從來沒到過非洲。
11:04
They should be equal, have no reason to be closer
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機率應會均等，沒有任何理由
11:07
to one African than another African.
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與兩非洲人的任何一個相近。
11:10
And that's indeed the case.
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分析的結果也的確是這樣。
11:12
Statistically speaking, there is no difference
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依統計數字來說，沒有任何差異
11:14
in how often the Neanderthal matches one African or the other.
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可供說明兩非洲人誰更類似尼安德塔人。
11:18
But this is different
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但我們來看看
11:20
if we now look at the European individual and an African.
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歐洲人的和非洲人的又不同了。
11:24
Then, significantly more often,
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尼安德塔人
11:27
does a Neanderthal match the European
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和歐洲人相似度高
11:29
rather than the African.
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而不似非洲人。
11:31
The same is true if we look at a Chinese individual
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這種結果同樣也出現在
11:34
versus an African,
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中國人相對於非洲人，
11:36
the Neanderthal will match the Chinese individual more often.
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尼安德塔人和中國人的相似度高。
11:40
This may also be surprising
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意外吧
11:42
because the Neanderthals were never in China.
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因為尼安德塔人從未到過中國。
11:44
So the model we've proposed to explain this
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因此，我們有這套構想
11:48
is that when modern humans came out of Africa
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現代人類祖先大約在十萬年前
11:50
sometime after 100,000 years ago,
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離開非洲，
11:53
they met Neanderthals.
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他們遇見了尼安德塔人。
11:55
Presumably, they did so first in the Middle East,
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可能他們在中東首度照面，
11:58
where there were Neanderthals living.
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在當時是尼安得塔人的居住地。
12:00
If they then mixed with each other there,
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接著他們可能在那裡混種，
12:02
then those modern humans
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那麼這些現代人類
12:04
that became the ancestors
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就成了
12:06
of everyone outside Africa
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非洲外所有人類的祖先，
12:08
carried with them this Neanderthal component in their genome
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這些帶有尼安德塔人元素的現代人類
12:11
to the rest of the world.
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遷移到世界各地。
12:13
So that today, the people living outside Africa
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因而今天，在非洲境外的人
12:16
have about two and a half percent of their DNA
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有約2.5%的DNA
12:19
from Neanderthals.
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來自尼安德塔人。
12:21
So having now a Neanderthal genome
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現在有尼安德塔人的基因組在手
12:24
on hand as a reference point
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作為參照，
12:26
and having the technologies
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還有先進的科技技術
12:28
to look at ancient remains
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可檢測古代的殘骸
12:30
and extract the DNA,
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和萃取DNA，
12:32
we can begin to apply them elsewhere in the world.
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我們便應用這些技術資源在世界各地的研究。
12:36
And the first place we've done that is in Southern Siberia
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我們第一個造訪的地方是在南西伯利亞
12:39
in the Altai Mountains
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的阿爾泰山，
12:41
at a place called Denisova,
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一個叫丹尼索瓦(Denisova)的地方，
12:43
a cave site in this mountain here,
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在這座山的洞穴內，
12:45
where archeologists in 2008
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考古學家在2008年
12:48
found a tiny little piece of bone --
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發現一塊極小的骨頭
12:50
this is a copy of it --
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這個是複製品，
12:52
that they realized came from the last phalanx
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他們發現這是屬於
12:56
of a little finger of a pinky of a human.
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人類小指骨。
12:59
And it was well enough preserved
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保存得相當好，
13:01
so we could determine the DNA from this individual,
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所以我們能測出這個人的DNA，
13:04
even to a greater extent
300
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所獲得的資料甚至比測
13:06
than for the Neanderthals actually,
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尼安德塔人的DNA還來得更多，
13:08
and start relating it to the Neanderthal genome
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我們將其與尼安德塔人和現今人類的
13:10
and to people today.
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基因組做比對。
13:13
And we found that this individual
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由這個人的DNA序列發現
13:15
shared a common origin for his DNA sequences
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其與尼安德塔人約在六十四萬年前
13:18
with Neanderthals around 640,000 years ago.
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有共同起源 。
13:22
And further back, 800,000 years ago
307
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而追溯至八十萬年前
13:25
is there a common origin
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才與現今人類
13:27
with present day humans.
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有相同起源。
13:29
So this individual comes from a population
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所以這個人來自於某個
13:31
that shares an origin with Neanderthals,
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與尼安德塔人有相同來源的族群，
13:34
but far back and then have a long independent history.
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但更早且有悠久而獨立的歷史。
13:37
We call this group of humans,
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我們稱這個族群的人類──
13:39
that we then described for the first time
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也就是我們首次
13:41
from this tiny, tiny little piece of bone,
315
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從這塊小小骨頭研究出來的人種──
13:43
the Denisovans,
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「丹尼索瓦人(Denisovans)」，
13:45
after this place where they were first described.
317
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以發現這塊骨頭的地方命名。
13:48
So we can then ask for Denisovans
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所以我們能在丹尼索瓦人(Denisovans)DNA
13:51
the same things as for the Neanderthals:
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尋求同樣的東西如同對尼安德塔人的探索：
13:53
Did they mix with ancestors of present day people?
320
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他們有跟現今人類的祖先混種嗎？
13:57
If we ask that question,
321
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倘若我們這麼問，
13:59
and compare the Denisovan genome
322
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並將丹尼索瓦人的基因組
14:01
to people around the world,
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與世界各地的人做比較。
14:03
we surprisingly find
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我們意外的發現
14:05
no evidence of Denisovan DNA
325
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今日住在西伯利亞一帶的人身上
14:07
in any people living even close to Siberia today.
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5000
沒有任何丹尼索瓦人的DNA血緣。
14:12
But we do find it in Papua New Guinea
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但在巴布亞新幾內亞(Papua New Guinea)及
14:14
and in other islands in Melanesia and the Pacific.
328
839000
4000
美拉尼西亞(Melanesia)和太平洋上的其他島嶼，找到它的「足跡」。
14:18
So this presumably means
329
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所以這可能意味著
14:20
that these Denisovans had been more widespread in the past,
330
845000
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丹尼索瓦人在過去所到之處範圍甚廣，
14:23
since we don't think that the ancestors of Melanesians
331
848000
3000
不過我們認為美拉尼西亞人的祖先
14:26
were ever in Siberia.
332
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未曽到過西伯利亞
14:28
So from studying
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所以研究這些
14:30
these genomes of extinct humans,
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已絕種人類的基因組，
14:33
we're beginning to arrive at a picture of what the world looked like
335
858000
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我們便可得到當時現代人類出走非洲的
14:36
when modern humans started coming out of Africa.
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世界的概況。
14:39
In the West, there were Neanderthals;
337
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3000
西方有尼安德塔人，
14:42
in the East, there were Denisovans --
338
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2000
東方有丹尼索瓦人，
14:44
maybe other forms of humans too
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也許還有其他的人種
14:46
that we've not yet described.
340
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只是我們還未發現。
14:48
We don't know quite where the borders between these people were,
341
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我們不是很確定這些不同人種(族群)的疆界在哪，
14:51
but we know that in Southern Siberia,
342
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2000
但我們知道在南西伯利亞
14:53
there were both Neanderthals and Denisovans
343
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有尼安德塔人和丹尼索瓦人，
14:55
at least at some time in the past.
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3000
至少過去某時曾在那出現。
14:58
Then modern humans emerged somewhere in Africa,
345
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3000
然後現代人類在非洲某處出現，
15:01
came out of Africa, presumably in the Middle East.
346
886000
3000
離開非洲後，可能到中東。
15:04
They meet Neanderthals, mix with them,
347
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他們遇到了尼安德塔人，與他們混種後，
15:07
continue to spread over the world,
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行蹤遍及世界各地，
15:10
and somewhere in Southeast Asia,
349
895000
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並在東南亞的某個地方，
15:13
they meet Denisovans and mix with them
350
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他們碰到丹尼索瓦人和他們混種
15:15
and continue on out into the Pacific.
351
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3000
接著進入到太平洋一帶。
15:18
And then these earlier forms of humans disappear,
352
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然後這些早期的人種消失了，
15:21
but they live on a little bit today
353
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但他們遺留的小小一部分至今
15:24
in some of us --
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仍殘存在某些人體內，
15:26
in that people outside of Africa have two and a half percent of their DNA
355
911000
3000
因為非洲境外人的DNA 有2.5%
15:29
from Neanderthals,
356
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2000
來自尼安德塔人。
15:31
and people in Melanesia
357
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在美拉尼西亞的人
15:33
actually have an additional five percent approximately
358
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3000
事實上有另外約5%的基因
15:36
from the Denisovans.
359
921000
3000
來自丹尼索瓦人。
15:39
Does this then mean that there is after all
360
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那麼就是說
15:41
some absolute difference
361
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畢竟還是有些完全差異
15:43
between people outside Africa and inside Africa
362
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存在非洲境內和境外的人
15:46
in that people outside Africa
363
931000
2000
因為在非洲境外人
15:48
have this old component in their genome
364
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2000
有這種古代元素在他們基因組，
15:50
from these extinct forms of humans,
365
935000
2000
是來自滅絕人種的基因
15:52
whereas Africans do not?
366
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而非州內的人則沒有，是這樣嗎?
15:54
Well I don't think that is the case.
367
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我可不這麼認為。
15:57
Presumably, modern humans
368
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現代人類可能
15:59
emerged somewhere in Africa.
369
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2000
出現在非洲某個地方
16:01
They spread across Africa also, of course,
370
946000
3000
當然他們散佈在非洲各處，
16:04
and there were older, earlier forms of humans there.
371
949000
3000
那時有更早期的人種存在那裡。
16:07
And since we mixed elsewhere,
372
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因為我們在其他地方混種，
16:09
I'm pretty sure that one day,
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我可以肯定有一天，
16:11
when we will perhaps have a genome
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我們或許將有一組基因組
16:13
of also these earlier forms in Africa,
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是屬於非洲內更早期人種的，
16:15
we will find that they have also mixed
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我們會發現這些更早期人種
16:17
with early modern humans in Africa.
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已和早期現代人在非洲混種。
16:21
So to sum up,
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所以結論是
16:23
what have we learned from studying genomes
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我們從研究現今人類
16:25
of present day humans
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和滅絕人種的基因組
16:27
and extinct humans?
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學到了什麼？
16:29
We learn perhaps many things,
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我們可能學到很多事，
16:31
but one thing that I find sort of important to mention
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但我認為最值得一提的是
16:36
is that I think the lesson is that we have always mixed.
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我領悟到「人類一再地融合」。
16:39
We mixed with these earlier forms of humans,
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我們和更早期的人種混種，
16:41
wherever we met them,
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不論我們是在哪裡遇到他們，
16:43
and we mixed with each other ever since.
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自那以後，我們彼此融合。
16:47
Thank you for your attention.
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謝謝你們的參與。
16:49
(Applause)
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（掌聲）
ABOUT THE SPEAKER
Svante Pääbo - GeneticistSvante Pääbo explores human genetic evolution by analyzing DNA extracted from ancient sources, including mummies, an Ice Age hunter and the bone fragments of Neanderthals.
Why you should listen
Svante Pääbo's research on the DNA of human and nonhuman primates has exposed the key genetic changes that transformed our grunting ape-like ancestors into the charming latte-sipping humans we are today. As a director at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, Pääbo and his team developed a technique of isolating and sequencing the DNA of creatures long extinct, using a variety of fragile, ancient source material from Homo sapiens and other human species.
His work shows that all humans trace their ancestry to a small population of Africans who later spread out across the world. We’ve also learned that Neanderthals, the short stocky hunters who disappeared 30,000 years ago, mated with the more modern human species and left their imprint deep within our genome. In 2007, Time named the Swedish biologist one of the 100 Most Influential People in the World for his work.
He says: "Neanderthals are not totally extinct. In some of us they live on, a little bit."
Svante Pääbo | Speaker | TED.com