TEDGlobal 2011
Svante Pääbo: DNA clues to our inner neanderthal
施温提·柏保: 我们体内的尼安德特人DNA痕迹
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遗传学家施温提·柏保通过介绍了一项大规模的世界范围内的研究，展示了早期人类中走出非洲之后与尼安德特人交配的DNA证据（是的，我们中的不少人拥有穴居人的DNA）。他解释了小小一片小指骨如何足以分辨出一个全新的类人人种。
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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我今天想谈谈
00:18
is what we can learn from studying the genomes
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从研究现代人和古人类
00:20
of living people
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基因组的研究中
00:22
and extinct humans.
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我们能够学到什么
00:24
But before doing that,
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在此之前
00:26
I just briefly want to remind you about what you already know:
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我先简短回顾一下你们已有的知识
00:29
that our genomes, our genetic material,
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我们的基因组 基因物质
00:31
are stored in almost all cells in our bodies in chromosomes
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几乎存在于人体所有细胞的染色体中
00:34
in the form of DNA,
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由脱氧核糖核酸（DNA）构成
00:36
which is this famous double-helical molecule.
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呈双螺旋分子结构
00:39
And the genetic information
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遗传信息
00:41
is contained in the form of a sequence
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存在于四种脱氧核苷酸
00:43
of four bases
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所组成的序列中
00:45
abbreviated with the letters A, T, C and G.
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这四种脱氧核苷酸分别简称为 A T C G
00:48
And the information is there twice --
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信息有两组
00:50
one on each strand --
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每条氢链上各有一组
00:52
which is important,
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这很重要
00:54
because when new cells are formed, these strands come apart,
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因为 每当新细胞形成 这些氢链会展开
00:56
new strands are synthesized with the old ones as templates
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而新的氢链以旧氢链作为模板进行互补配对
00:59
in an almost perfect process.
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这一过程几乎精准无误
01:02
But nothing, of course, in nature
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当然 在自然界中
01:04
is totally perfect,
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事事无绝对
01:06
so sometimes an error is made
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错误总有发生的时候
01:08
and a wrong letter is built in.
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而一旦发生 一个错误的字母就会被编进去
01:11
And we can then see the result
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我们可以等一下会看到
01:13
of such mutations
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这些突变产生的结果
01:15
when we compare DNA sequences
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例如拿在座各位的DNA 序列
01:17
among us here in the room, for example.
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进行比对
01:20
If we compare my genome to the genome of you,
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如果拿我的基因组与你的基因组相比
01:23
approximately every 1,200, 1,300 letters
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每1200到1300个字母
01:27
will differ between us.
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就会出现差异
01:29
And these mutations accumulate
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这些突变像时间一样
01:31
approximately as a function of time.
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不断累积
01:34
So if we add in a chimpanzee here, we will see more differences.
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如果把一只黑猩猩加进来 我们能看到更多差异
01:37
Approximately one letter in a hundred
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大致每100个字母
01:40
will differ from a chimpanzee.
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就会出现差异
01:42
And if you're then interested in the history
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如果你对一段DNA
01:44
of a piece of DNA, or the whole genome,
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或整个基因组的历史感兴趣
01:46
you can reconstruct the history of the DNA
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你可以通过观察到的这些差异
01:49
with those differences you observe.
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对DNA的历史进行重组
01:51
And generally we depict our ideas about this history
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我们可以通过这个树状图
01:55
in the form of trees like this.
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来描述这段历史过程
01:57
In this case, it's very simple.
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在这里 情况非常简单
01:59
The two human DNA sequences
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这两个人类的DNA序列
02:01
go back to a common ancestor quite recently.
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可以追溯到较为近期的一位共同祖先
02:04
Farther back is there one shared with chimpanzees.
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而进一步追溯下去 就找到了他们和黑猩猩的共同祖先
02:08
And because these mutations
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由于这些突变
02:11
happen approximately as a function of time,
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多少起到了时间的作用
02:13
you can transform these differences
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你可以通过这些差异
02:15
to estimates of time,
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来对时间进行预测
02:17
where the two humans, typically,
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这两个人类通常
02:19
will share a common ancestor about half a million years ago,
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在50万年前有共同的祖先
02:23
and with the chimpanzees,
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而与黑猩猩
02:25
it will be in the order of five million years ago.
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则在500晚年前有共同的祖先
02:28
So what has now happened in the last few years
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在过去几年里
02:30
is that there are account technologies around
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由于有了先进的技术
02:32
that allow you to see many, many pieces of DNA very quickly.
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你们能够很快地查看许许多多DNA片段
02:36
So we can now, in a matter of hours,
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我们现在能够在短短几个小时里
02:38
determine a whole human genome.
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鉴别出一整个人类基因组
02:41
Each of us, of course, contains two human genomes --
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当然 我们每个人都有两个基因组
02:44
one from our mothers and one from our fathers.
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一个来自母亲 而另一个来自父亲
02:47
And they are around three billion such letters long.
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长度约为30亿个字母
02:51
And we will find that the two genomes in me,
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我们会发现 我的两个基因组
02:53
or one genome of mine we want to use,
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或者一个基因组
02:55
will have about three million differences
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在这样的排列中
02:58
in the order of that.
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有300万个差异
03:00
And what you can then also begin to do
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现在你可以开始
03:02
is to say, "How are these genetic differences
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分析这些基因差异
03:04
distributed across the world?"
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如何分布在世界各地
03:06
And if you do that,
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如果你这么做
03:08
you find a certain amount of genetic variation in Africa.
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你会发现一定数量的基因变异发生在非洲
03:12
And if you look outside Africa,
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如果你看非洲以外
03:15
you actually find less genetic variation.
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你找到相对较少的基因变异
03:18
This is surprising, of course,
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这让人大吃一惊
03:20
because in the order of six to eight times fewer people
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这是因为非洲以外的人口数量
03:23
live in Africa than outside Africa.
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比非洲的人口多了6至8倍
03:26
Yet the people inside Africa
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但是非洲人
03:29
have more genetic variation.
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拥有更多的基因变异
03:32
Moreover, almost all these genetic variants
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更值得注意的是 几乎所有非洲以外的
03:34
we see outside Africa
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基因变异
03:36
have closely related DNA sequences
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都与非洲境内的DNA序列
03:38
that you find inside Africa.
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关系非常密切
03:40
But if you look in Africa,
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但如果你看非洲境内
03:42
there is a component of the genetic variation
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基因变异的组成
03:45
that has no close relatives outside.
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在非洲以外并没有近亲
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So a model to explain this
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所以这个模式说明
03:51
is that a part of the African variation, but not all of it,
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来自非洲的一部分变异
03:54
[has] gone out and colonized the rest of the world.
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走出了非洲 走向了世界
03:58
And together with the methods to date these genetic differences,
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再通过使用追溯这些基因差异的手段
04:02
this has led to the insight
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我们得到这样一个结论
04:04
that modern humans --
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即现代人
04:06
humans that are essentially indistinguishable from you and me --
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本质上基本相同的你和我
04:09
evolved in Africa, quite recently,
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都是在10万至20万年前
04:12
between 100 and 200,000 years ago.
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在非洲出现并演进的
04:16
And later, between 100 and 50,000 years ago or so,
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之后 在大约10万到5万年前
04:20
went out of Africa
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他们走出了非洲
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to colonize the rest of the world.
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走向了世界
04:24
So what I often like to say
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我常说
04:26
is that, from a genomic perspective,
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从基因组的层面上看
04:28
we are all Africans.
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我们都是非洲人
04:30
We either live inside Africa today,
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现代人要么生活在非洲
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or in quite recent exile.
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要么就是以前从非洲走出来的
04:35
Another consequence
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现代人近期起源的
04:37
of this recent origin of modern humans
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另一个结果
04:40
is that genetic variants
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是基因变异
04:42
are generally distributed widely in the world,
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在世界上广泛分布
04:44
in many places,
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到很多地方
04:46
and they tend to vary as gradients,
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至少从总体上看
04:49
from a bird's-eye perspective at least.
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基因变异的走势成斜线状
04:53
And since there are many genetic variants,
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既然存在如此多的基因变异
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and they have different such gradients,
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它们的变化率也不同
04:58
this means that if we determine a DNA sequence --
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这意味着如果我们鉴别出一个DNA序列
05:01
a genome from one individual --
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即某个人的基因组
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we can quite accurately estimate
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我们就可以非常准确地推算出
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where that person comes from,
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这个人来自何方
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provided that its parents or grandparents
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假设这个人的父母或祖父母
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haven't moved around too much.
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基本都留在一个地方
05:13
But does this then mean,
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但是这就意味着
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as many people tend to think,
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比如说 许多人认为
05:17
that there are huge genetic differences between groups of people --
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不同大洲的人
05:20
on different continents, for example?
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其基因存在巨大差异吗？
05:22
Well we can begin to ask those questions also.
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我们也在问这些问题
05:25
There is, for example, a project that's underway
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有一个正在进行的项目
05:28
to sequence a thousand individuals --
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在为一千个人的基因组排序
05:30
their genomes -- from different parts of the world.
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这些人来自世界各地
05:33
They've sequenced 185 Africans
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他们为来自非洲的两个种群的
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from two populations in Africa.
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185人进行了基因组排序
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[They've] sequenced approximately equally [as] many people
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他们也在欧洲和中国也找了同样多的人
05:42
in Europe and in China.
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对其基因组进行排序
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And we can begin to say how much variance do we find,
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现在可以说我们找到了多少差异了
05:48
how many letters that vary
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也就是其中一个序列
05:51
in at least one of those individual sequences.
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有多少字母是不同的
05:54
And it's a lot: 38 million variable positions.
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这个数字很大 3千8百万个差异
05:58
But we can then ask: Are there any absolute differences
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我们会为 非洲人和非非洲人种
06:01
between Africans and non-Africans?
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是否存在绝对的差异
06:03
Perhaps the biggest difference
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也许我们许多人所认为的
06:05
most of us would imagine existed.
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最大差异曾经存在过
06:07
And with absolute difference --
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我所谓的
06:09
and I mean a difference
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绝对差异是指
06:11
where people inside Africa at a certain position,
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当所有非洲人 在基因序列中
06:14
where all individuals -- 100 percent -- have one letter,
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某个特定位置上都有同样一个字母
06:17
and everybody outside Africa has another letter.
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而所有非非洲人种 在这个位置上都有另一个字母
06:21
And the answer to that, among those millions of differences,
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而在这几百万个差异中
06:24
is that there is not a single such position.
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没有任何一个位置有这种情况
06:29
This may be surprising.
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这听起来不可思议
06:31
Maybe a single individual is misclassified or so.
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也许这是因为个别人被分错组了
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So we can relax the criterion a bit
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那我们就把标准放松一些
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and say: How many positions do we find
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看看我们在95%的非洲人样本中
06:38
where 95 percent of people in Africa have
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能够找到多少个这样的位置
06:40
one variant,
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一个变量是
06:42
95 percent another variant,
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95% 另一个变量
06:44
and the number of that is 12.
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我们得到的数字是12
06:46
So this is very surprising.
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这真的很神奇
06:48
It means that when we look at people
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这意味着我们看到
06:50
and see a person from Africa
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一个来自非洲的人
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and a person from Europe or Asia,
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和一个来自欧洲或亚洲的人
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we cannot, for a single position in the genome with 100 percent accuracy,
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从单个序列位置来看 我们无法
07:00
predict what the person would carry.
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100%准确判断这个人携带的基因组的序列
07:02
And only for 12 positions
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而通过12个序列位置判断
07:04
can we hope to be 95 percent right.
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我们也只能期望95%的准确率
07:08
This may be surprising,
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这令人意外
07:10
because we can, of course, look at these people
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我们从外表上看
07:12
and quite easily say where they or their ancestors came from.
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很容易就知道他们或其祖先从哪里来
07:16
So what this means now
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这意味着
07:18
is that those traits we then look at
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那些显而易见的特征
07:20
and so readily see --
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包括
07:22
facial features, skin color, hair structure --
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面部特征 肤色 毛发结构
07:25
are not determined by single genes with big effects,
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都不是由单个其重大作用的基因决定的
07:29
but are determined by many different genetic variants
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而是许多不同基因变体共同作用的结果
07:32
that seem to vary in frequency
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而在世界不同的地方
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between different parts of the world.
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这些变体变化呈现不同频率
07:36
There is another thing with those traits
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关于这些特征的另外一点
07:39
that we so easily observe in each other
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我们能够不费吹灰之力就能分辨彼此
07:42
that I think is worthwhile to consider,
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我认为这点非常值得思考
07:44
and that is that, in a very literal sense,
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那就是
07:47
they're really on the surface of our bodies.
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这些特征都体现在我们体表
07:50
They are what we just said --
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这些都是
07:52
facial features, hair structure, skin color.
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面部特征 毛发结构 肤色
07:55
There are also a number of features
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在食物的新陈代谢方面
07:57
that vary between continents like that
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以及对抗病菌的
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that have to do with how we metabolize food that we ingest,
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免疫系统方面
08:03
or that have to do
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不同人种的
08:05
with how our immune systems deal with microbes
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相关特征
08:08
that try to invade our bodies.
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也有不同
08:10
But so those are all parts of our bodies
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但这些都属于身体特征
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where we very directly interact with our environment,
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直接与环境互动
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in a direct confrontation, if you like.
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也可以说是与自然亲密接触
08:19
It's easy to imagine
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不难想象
08:21
how particularly those parts of our bodies
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身体这些部位
08:23
were quickly influenced by selection from the environment
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能够很快被自然选择所影响
08:26
and shifted frequencies of genes
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并改变相关的
08:28
that are involved in them.
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基因频率
08:30
But if we look on other parts of our bodies
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如果我们看看那些
08:33
where we don't directly interact with the environment --
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不直接接触外界环境的部位
08:35
our kidneys, our livers, our hearts --
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如肾脏 肝脏 心脏
08:38
there is no way to say,
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就完全不可能
08:40
by just looking at these organs,
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通过观察这些器官
08:42
where in the world they would come from.
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来判断人种
08:46
So there's another interesting thing
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由此可推断出
08:48
that comes from this realization
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另外一个有趣的观点
08:51
that humans have a recent common origin in Africa,
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那就是人类的共同祖先来自非洲
08:55
and that is that when those humans emerged
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他们出现在
08:58
around 100,000 years ago or so,
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距今10年以前
09:00
they were not alone on the planet.
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但他们不是唯一的人类种群
09:02
There were other forms of humans around,
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当时还有其他人类种群
09:05
most famously perhaps, Neanderthals --
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最著名的要数尼安德特人
09:08
these robust forms of humans,
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这些体魄强健的人类
09:10
compared to the left here
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在左边
09:12
with a modern human skeleton on the right --
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与右边的现代人骨架相对比
09:16
that existed in Western Asia and Europe
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他们自千百年前就一直生活在
09:19
since several hundreds of thousands of years.
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西亚和欧洲地区
09:21
So an interesting question is,
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这里有个问题很有意思
09:23
what happened when we met?
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我们两种人相遇的时候 发生了什么
09:25
What happened to the Neanderthals?
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尼安德特人后来怎么了
09:27
And to begin to answer such questions,
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为了回答这些问题
09:29
my research group -- since over 25 years now --
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我的研究组 从25年前
09:33
works on methods to extract DNA
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就一直在对从生活在几万年前的
09:35
from remains of Neanderthals
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穴居人以及古生物的
09:37
and extinct animals
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遗骸中提取其DNA的方法
09:39
that are tens of thousands of years old.
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进行研究
09:42
So this involves a lot of technical issues
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提取DNA
09:45
in how you extract the DNA,
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并将它转换成可以进行排序的形式
09:47
how you convert it to a form you can sequence.
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需要用到纷繁复杂的技术
09:50
You have to work very carefully
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工作的时候要高度谨慎
09:52
to avoid contamination of experiments
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以免把你的DNA
09:55
with DNA from yourself.
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与试验中的DNA混在一起
09:58
And this then, in conjunction with these methods
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通过使用这些方法
10:01
that allow very many DNA molecules to be sequenced very rapidly,
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我们能够在很短的时间里将许多DNA分子排序
10:05
allowed us last year
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我们在去年
10:07
to present the first version of the Neanderthal genome,
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成功将首个尼安德特人基因组排序
10:10
so that any one of you
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所有人
10:12
can now look on the Internet, on the Neanderthal genome,
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现在都能在网络上看到
10:14
or at least on the 55 percent of it
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我们到目前为止重建的
10:17
that we've been able to reconstruct so far.
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尼安德特人55%的基因组
10:20
And you can begin to compare it to the genomes
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你可以开始把它
10:22
of people who live today.
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和现代人类的基因组作对比
10:25
And one question
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有一个问题
10:27
that you may then want to ask
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你可能会问到
10:29
is, what happened when we met?
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那就是 我们碰面时 发生了什么
10:31
Did we mix or not?
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我们交汇过吗
10:33
And the way to ask that question
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研究这个问题
10:35
is to look at the Neanderthal that comes from Southern Europe
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就要把来自南欧的尼安德特人基因组
10:38
and compare it to genomes
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与现代人的基因组
10:40
of people who live today.
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相比对
10:42
So we then look
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接下来
10:44
to do this with pairs of individuals,
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我们一对对地进行比对
10:46
starting with two Africans,
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先比对两个非洲人
10:48
looking at the two African genomes,
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观察这两个非洲人的基因组
10:50
finding places where they differ from each other,
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找出它们的差异
10:53
and in each case ask: What is a Neanderthal like?
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每次比对都要问 尼安德特人的情况呢
10:56
Does it match one African or the other African?
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它是否与其中一个非洲人相匹配
10:59
We would expect there to be no difference,
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我们认为这两个非洲人之间没有差异
11:02
because Neanderthals were never in Africa.
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因为尼安德特人从未去过非洲
11:04
They should be equal, have no reason to be closer
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他们应该是一样的 其中一个非洲人
11:07
to one African than another African.
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不会比另一个非洲人与尼安德特人更相近
11:10
And that's indeed the case.
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而事实正是如此
11:12
Statistically speaking, there is no difference
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数据说明
11:14
in how often the Neanderthal matches one African or the other.
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尼安德特人和两个非洲人的差距是一样的
11:18
But this is different
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但是这又不同了
11:20
if we now look at the European individual and an African.
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这次我们比对的是欧洲人和非洲人
11:24
Then, significantly more often,
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尼安德特人与欧洲人
11:27
does a Neanderthal match the European
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相匹配的情况
11:29
rather than the African.
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远胜于与非洲人的匹配
11:31
The same is true if we look at a Chinese individual
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我们在比对中国人和非洲人的时候
11:34
versus an African,
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情况也是这样的
11:36
the Neanderthal will match the Chinese individual more often.
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尼安德特人与中国人匹配的程度更高
11:40
This may also be surprising
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这也让人惊奇
11:42
because the Neanderthals were never in China.
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因为 尼安德特人从来没有去过中国
11:44
So the model we've proposed to explain this
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我们提出的解释是
11:48
is that when modern humans came out of Africa
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当现代人在10万年前
11:50
sometime after 100,000 years ago,
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走出非洲时
11:53
they met Neanderthals.
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他们碰上了尼安德特人
11:55
Presumably, they did so first in the Middle East,
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他们可能首先到了中东
11:58
where there were Neanderthals living.
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那里正是穴居人生活的地方
12:00
If they then mixed with each other there,
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如果他们曾在那里交汇过
12:02
then those modern humans
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那么那些现代人
12:04
that became the ancestors
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后来成为了非洲以外
12:06
of everyone outside Africa
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人类的祖先
12:08
carried with them this Neanderthal component in their genome
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就携带了尼安德特人的基因
12:11
to the rest of the world.
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并把它传播到了世界各地
12:13
So that today, the people living outside Africa
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于是 今天 生活在非洲以外的人们
12:16
have about two and a half percent of their DNA
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有2.5%的DNA
12:19
from Neanderthals.
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来自穴居人
12:21
So having now a Neanderthal genome
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我们现在有了一个穴居人基因组
12:24
on hand as a reference point
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作为一个参照点
12:26
and having the technologies
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又有了研究古代遗骸
12:28
to look at ancient remains
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并从中提取DNA的
12:30
and extract the DNA,
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技术
12:32
we can begin to apply them elsewhere in the world.
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我们可以在世界其它地区采用这些技术
12:36
And the first place we've done that is in Southern Siberia
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我们首先在南西伯利亚
12:39
in the Altai Mountains
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阿尔泰山
12:41
at a place called Denisova,
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一个叫做德尼柔娃（Denisova）的地方
12:43
a cave site in this mountain here,
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这是一个溶洞
12:45
where archeologists in 2008
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考古学家在2008年
12:48
found a tiny little piece of bone --
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发现了一小片骨头
12:50
this is a copy of it --
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这是骨头的复制品
12:52
that they realized came from the last phalanx
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他们发现这是
12:56
of a little finger of a pinky of a human.
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人类小手指的趾骨
12:59
And it was well enough preserved
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它的保存状态很好
13:01
so we could determine the DNA from this individual,
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让我们能够从中鉴别出这个人的DNA
13:04
even to a greater extent
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其序列长度比先前
13:06
than for the Neanderthals actually,
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尼安德特人的DNA还要长
13:08
and start relating it to the Neanderthal genome
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并将它与尼安德特人的基因组
13:10
and to people today.
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和现代人的基因组相联系
13:13
And we found that this individual
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我们发现
13:15
shared a common origin for his DNA sequences
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这个人的DNA序列
13:18
with Neanderthals around 640,000 years ago.
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源自64万年前的尼安德特人
13:22
And further back, 800,000 years ago
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进一步追溯下去 到了80万年前
13:25
is there a common origin
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这个人和现代人
13:27
with present day humans.
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有共同的祖先
13:29
So this individual comes from a population
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这个人来自一个
13:31
that shares an origin with Neanderthals,
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与尼安德特人拥有共同祖先的种群
13:34
but far back and then have a long independent history.
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而在更久以前 他们有很长的独立历史
13:37
We call this group of humans,
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从这小小一片的骨头
13:39
that we then described for the first time
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通过这小小一片骨头
13:41
from this tiny, tiny little piece of bone,
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我们首次发现这个人种
13:43
the Denisovans,
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于是我们用发现地点的名字
13:45
after this place where they were first described.
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将他们命名为德尼柔娃人
13:48
So we can then ask for Denisovans
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对于德尼柔娃人
13:51
the same things as for the Neanderthals:
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我们也问了同样的问题
13:53
Did they mix with ancestors of present day people?
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他们与现代人的祖先何时进行交汇的？
13:57
If we ask that question,
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如果我们问这个问题
13:59
and compare the Denisovan genome
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并把德尼柔娃人的基因组
14:01
to people around the world,
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如世界各地人们的基因组相比
14:03
we surprisingly find
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我们惊奇地发现
14:05
no evidence of Denisovan DNA
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没有证据证明德尼柔娃人的DNA
14:07
in any people living even close to Siberia today.
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与现在生活在西伯利亚的人有关系
14:12
But we do find it in Papua New Guinea
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但是 我们在巴布亚新几内亚
14:14
and in other islands in Melanesia and the Pacific.
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和一些美拉尼西亚和太平洋岛屿上找到了证据
14:18
So this presumably means
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由于我们认定
14:20
that these Denisovans had been more widespread in the past,
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美拉尼西亚人的祖先从未到过西伯利亚
14:23
since we don't think that the ancestors of Melanesians
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所以我们推测
14:26
were ever in Siberia.
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德尼柔娃人在过去分布的地区更广
14:28
So from studying
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通过研究
14:30
these genomes of extinct humans,
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这些消亡了的人类种群的基因组
14:33
we're beginning to arrive at a picture of what the world looked like
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我们对现代人祖先走出非洲时的世界
14:36
when modern humans started coming out of Africa.
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有了逐步的认识
14:39
In the West, there were Neanderthals;
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西有尼安德特人
14:42
in the East, there were Denisovans --
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东有德尼柔娃人
14:44
maybe other forms of humans too
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也许还有其他
14:46
that we've not yet described.
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我们尚未发现的人种
14:48
We don't know quite where the borders between these people were,
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我们并不确定这些人种的分界在哪里
14:51
but we know that in Southern Siberia,
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但我们知道尼安德特人
14:53
there were both Neanderthals and Denisovans
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和德尼柔娃人都曾在南西伯利亚生活过
14:55
at least at some time in the past.
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他们至少曾经一度共同生活在那里
14:58
Then modern humans emerged somewhere in Africa,
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现代人随后在非洲出现
15:01
came out of Africa, presumably in the Middle East.
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3000
走出了非洲 我们认为他们去到了中东
15:04
They meet Neanderthals, mix with them,
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他们和尼安德特人交汇
15:07
continue to spread over the world,
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接着继续分散到世界各地
15:10
and somewhere in Southeast Asia,
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到了东南亚
15:13
they meet Denisovans and mix with them
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他们又和德尼柔娃人尼安德特人交汇
15:15
and continue on out into the Pacific.
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接着去到太平洋岛屿
15:18
And then these earlier forms of humans disappear,
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后来 这些早期人类都消亡了
15:21
but they live on a little bit today
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但是今天
15:24
in some of us --
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在我们某些人
15:26
in that people outside of Africa have two and a half percent of their DNA
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也就是那些后来走出非洲的人仍然有2.5%的DNA
15:29
from Neanderthals,
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来自尼安德特人
15:31
and people in Melanesia
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而生活在美拉尼西亚的人们
15:33
actually have an additional five percent approximately
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另有5%的DNA
15:36
from the Denisovans.
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来自德尼柔娃人
15:39
Does this then mean that there is after all
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这是否意味着
15:41
some absolute difference
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非洲以外的人
15:43
between people outside Africa and inside Africa
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与非洲人之间存在绝对的差异
15:46
in that people outside Africa
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非洲以外的人们
15:48
have this old component in their genome
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拥有已消亡
15:50
from these extinct forms of humans,
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古人类的基因
15:52
whereas Africans do not?
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而非洲人却没有
15:54
Well I don't think that is the case.
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我不这么认为
15:57
Presumably, modern humans
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现代人被认为
15:59
emerged somewhere in Africa.
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最早出现在非洲
16:01
They spread across Africa also, of course,
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他们当然也遍布整个非洲
16:04
and there were older, earlier forms of humans there.
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那里有更古老的人类种群
16:07
And since we mixed elsewhere,
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既然我们曾经与其他种群杂居
16:09
I'm pretty sure that one day,
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我敢肯定
16:11
when we will perhaps have a genome
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当我们找到一个
16:13
of also these earlier forms in Africa,
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更早期人类的基因组
16:15
we will find that they have also mixed
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我们可能会发现
16:17
with early modern humans in Africa.
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他们曾与早期现代人在非洲交汇
16:21
So to sum up,
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总结一下
16:23
what have we learned from studying genomes
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从比对现今人类
16:25
of present day humans
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与已消亡的古人类的基因组研究
16:27
and extinct humans?
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我们学到了什么
16:29
We learn perhaps many things,
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我们也许学到了很多东西
16:31
but one thing that I find sort of important to mention
383
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我认为最重要的是
16:36
is that I think the lesson is that we have always mixed.
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我们的基因交汇在了一起
16:39
We mixed with these earlier forms of humans,
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我们拥有这些古人类的基因
16:41
wherever we met them,
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不管现代人曾在哪里与他们相遇
16:43
and we mixed with each other ever since.
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从那以后 我们的基因就交汇在了一起
16:47
Thank you for your attention.
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非常感谢
16:49
(Applause)
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（众人鼓掌）
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