TEDGlobal 2007
Spencer Wells: A family tree for humanity
Spencer Well 建立整个人类的家谱
Filmed:
Readability: 4.5
824,434 views
所有的人类分享着一些共同的DNA。这些DNA从我们共同的非洲祖先代代相传下来。遗传学家 Spencer Well 讲述了他领导的基因地理项目如何用这些共享的DNA来解决我们人类 — 所有不同种族国籍 — 是怎么相互联系的问题。
Spencer Wells - Genographer
Spencer Wells studies human diversity -- the process by which humanity, which springs from a single common source, has become so astonishingly diverse and widespread. Full bio
Spencer Wells studies human diversity -- the process by which humanity, which springs from a single common source, has become so astonishingly diverse and widespread. Full bio
Double-click the English transcript below to play the video.
00:18
Jambo, bonjour, zdravstvujtye, dayo: these are a few of the languages
0
0
9000
Jambo, bonjour, zdraveite, trayo。这些是几种不同的语言，
00:27
that I've spoken little bits of over the course of the last six weeks,
1
9000
4000
我在过去六周里多多少少用到了它们。
00:31
as I've been to 17 countries I think I'm up to, on this crazy tour I've been doing,
2
13000
5000
我在进行一个非常疯狂的旅行，总共要跑十七个国家，
00:36
checking out various aspects of the project that we're doing.
3
18000
3000
去为我们正在做的项目做各种各样的事。
00:39
And I'm going to tell you a little bit about later on.
4
21000
2000
我现在就要向你们介绍这个项目。
00:41
And visiting some pretty incredible places,
5
23000
3000
我也见到了各种绝妙的风土人情。
00:44
places like Mongolia, Cambodia, New Guinea, South Africa, Tanzania twice --
6
26000
6000
像是蒙古，柬埔寨，新几内亚，南非，我还来过两次坦桑尼亚。
00:50
I was here a month ago.
7
32000
2000
一个月前来过一次。
00:52
And the opportunity to make a whirlwind tour of the world like that
8
34000
5000
这种旋风式的全球旅行的机会
00:57
is utterly amazing, for lots of reasons.
9
39000
3000
是绝妙十足的，原因很多，
01:00
You see some incredible stuff.
10
42000
2000
（首先）你能长不少见识，
01:02
And you get to make these spot comparisons
11
44000
2000
同时你还能比较不同的地区，
01:04
between people all around the globe.
12
46000
2000
比较全球的人种。
01:06
And the thing that you really take away from that,
13
48000
2000
最重要的是你意识到，
01:08
the kind of surface thing that you take away from it,
14
50000
3000
那种最明显的感觉就是，
01:11
is not that we're all one, although I'm going to tell you about that,
15
53000
4000
并不是我们又多么像一个整体，尽管我想和你们讨论这方面。
01:15
but rather how different we are.
16
57000
2000
而是我们彼此有多么的不同。
01:17
There is so much diversity around the globe.
17
59000
3000
放眼全球多种多样的人，
01:20
6,000 different languages spoken by six and a half billion people,
18
62000
3000
六十五亿人口，不同肤色，不同高矮胖瘦，
01:23
all different colors, shapes, sizes.
19
65000
3000
讲着六千种不同的语言。
01:26
You walk down the street in any big city, you travel like that,
20
68000
3000
当你做这样的旅行，当你在任何大城市的大街上漫步，
01:29
and you are amazed at the diversity in the human species.
21
71000
4000
你会被人类的多样性所惊服。
01:33
How do we explain that diversity?
22
75000
3000
怎样解释这种多样性呢？
01:36
Well, that's what I'm going to talk about today,
23
78000
2000
这正是我今天要讲的。
01:38
is how we're using the tools of genetics,
24
80000
2000
就是我们怎样用遗传学的方法，
01:40
population genetics in particular, to tell us how we generated this diversity,
25
82000
6000
特别是人口遗传学，来说明我们是怎么进化出多样性的，
01:46
and how long it took.
26
88000
2000
还有花了多长时间产生多样性的。
01:48
Now, the problem of human diversity,
27
90000
2000
现在，人类多样性的问题，
01:50
like all big scientific questions --
28
92000
2000
就像是所有那些重要的科学问题，
01:52
how do you explain something like that --
29
94000
2000
很难一下子说清楚。
01:54
can be broken down into sub-questions.
30
96000
2000
我们可以把这个大问题分解成一些小问题，
01:56
And you can ferret away at those little sub-questions.
31
98000
3000
然后你就能一个个地解决。
01:59
First one is really a question of origins.
32
101000
2000
第一个小问题其实是关于人类的起源。
02:01
Do we all share a common origin, in fact?
33
103000
2000
我们到底是不是从同一个起点来的？
02:03
And given that we do -- and that's the assumption
34
105000
3000
如果是的话，这也是每个人都赞同的假说，
02:06
everybody, I think, in this room would make -- when was that?
35
108000
3000
又是在什么时候？
02:09
When did we originate as a species?
36
111000
2000
从什么时候我们作为一个物种开始存在？
02:11
How long have we been divergent from each other?
37
113000
2000
我们已经（从一个起源）开始分支了多长时间？
02:13
And the second question is related, but slightly different.
38
115000
4000
第二个小问题和这个有关，但是很不一样。
02:17
If we do spring from a common source,
39
119000
2000
那就是如果我们都是从一个起点来的，
02:19
how did we come to occupy every corner of the globe,
40
121000
2000
又是怎样散布到世界的各个角落，
02:21
and in the process generate all of this diversity,
41
123000
2000
怎样一步步产生不同的人种，
02:23
the different ways of life, the different appearances,
42
125000
3000
不同的生活方式，不同的样貌，
02:26
the different languages around the world?
43
128000
2000
不同的语言的呢？
02:28
Well, the question of origins, as with so many other questions in biology,
44
130000
3000
关于起源的问题，就像很多其他生物学上的问题一样，
02:31
seems to have been answered by Darwin over a century ago.
45
133000
2000
看起来已经被达尔文在一百年前就回答了。
02:33
In "The Descent of Man," he wrote,
46
135000
2000
在他的书“人类的起源”中，他写道：
02:35
"In each great region of the world, the living mammals
47
137000
2000
“在世界的每个区域，现存的哺乳动物
02:37
are closely related to the extinct species of the same region.
48
139000
3000
都和同一区域灭绝的物种紧密相连。
02:40
It's therefore probable that Africa was formerly inhabited by extinct apes
49
142000
3000
因此很有可能非洲从前有类人猿，现在灭绝了，
02:43
closely allied to the gorilla and chimpanzee,
50
145000
3000
而它们和大猩猩以及黑猩猩相关。
02:46
and as these two species are now man's nearest allies,
51
148000
3000
这两个物种是现今人类的最接近的物种，
02:49
it's somewhat more probable that our early progenitors
52
151000
2000
由此可见，人类的早期祖先
02:51
lived on the African continent than elsewhere."
53
153000
2000
最有可能生活在非洲大陆上，而不是别处。”
02:53
So we're done, we can go home -- finished the origin question.
54
155000
4000
这样问题就解决了，我们可以回家了，我们回答了起源的问题。
02:57
Well, not quite. Because Darwin was talking about our distant ancestry,
55
159000
4000
等等，并没有完全回答。因为达尔文讲的是我们的远祖，
03:01
our common ancestry with apes.
56
163000
2000
我们和猿类共享的始祖。
03:03
And it is quite clear that apes originated on the African continent.
57
165000
4000
很明显猿类是从非洲大陆来的。
03:07
Around 23 million years ago, they appear in the fossil record.
58
169000
3000
根据化石记载它们是在两百三十万年前出现的。
03:10
Africa was actually disconnected from the other landmasses at that time,
59
172000
3000
非洲已经和其他大陆分隔开了。
03:13
due to the vagaries of plate tectonics, floating around the Indian Ocean.
60
175000
4000
由于捉摸不定的的板块构造，非洲在印度洋上漂浮，
03:17
Bumped into Eurasia around 16 million years ago,
61
179000
2000
大约一百六十万年前，撞到欧亚板块上，
03:19
and then we had the first African exodus, as we call it.
62
181000
3000
我们就有了第一次的所谓的“非洲物种外流”。
03:22
The apes that left at that time ended up in Southeast Asia,
63
184000
2000
那时候离开非洲的猿类到达了东南亚，
03:24
became the gibbons and the orangutans.
64
186000
2000
演变成了长臂猿和猩猩。
03:26
And the ones that stayed on in Africa
65
188000
2000
那些留在非洲的猿类
03:28
evolved into the gorillas, the chimpanzees and us.
66
190000
2000
演变成了大猩猩，黑猩猩，和我们人类。
03:30
So, yes, if you're talking about our common ancestry with apes,
67
192000
3000
所以，如果你指的是我们和猿类的共同祖先，
03:33
it's very clear, by looking at the fossil record, we started off here.
68
195000
4000
只要看化石纪录，毫无疑义地，我们是从非洲来的。
03:37
But that's not really the question I'm asking.
69
199000
2000
但是这并不是我想知道的问题。
03:39
I'm asking about our human ancestry,
70
201000
2000
我指的是原始人类，
03:41
things that we would recognize as being like us
71
203000
3000
从它们变成为人类开始算，
03:44
if they were sitting here in the room.
72
206000
2000
就好像是原始人类现在就在这个房间，
03:46
If they were peering over your shoulder,
73
208000
2000
如果它们就在你边上，
03:48
you wouldn't leap back, like that. What about our human ancestry?
74
210000
3000
你不会吓得往后退。什么是原始人类？
03:51
Because if we go far enough back,
75
213000
2000
如果我们追溯起源。
03:53
we share a common ancestry with every living thing on Earth.
76
215000
3000
我们能够找到和世界上所有生命的共同起源。
03:56
DNA ties us all together, so we share ancestry with barracuda
77
218000
3000
DNA把我们联系起来，我们甚至和梭鱼，
03:59
and bacteria and mushrooms, if you go far enough back -- over a billion years.
78
221000
5000
细菌，蘑菇，都有共同祖先，如果你真的是往回找上十亿年的话。
04:04
What we're asking about though is human ancestry.
79
226000
2000
我们这里讲的是原始的人类祖先。
04:06
How do we study that?
80
228000
2000
怎么研究呢？
04:08
Well, historically, it has been studied using the science of paleoanthropology.
81
230000
4000
古生人类学已经研究了很多年了，
04:12
Digging things up out of the ground,
82
234000
2000
他们挖掘古生物遗迹，
04:14
and largely on the basis of morphology --
83
236000
2000
大部分的分类是根据样貌，
04:16
the way things are shaped, often skull shape -- saying,
84
238000
3000
古生物是什么样子的，多数是根据头骨的样子，好比说
04:19
"This looks a little bit more like us than that, so this must be my ancestor.
85
241000
4000
“这个比那个看起来更像我们一点点，那么这个想必是我的祖先。
04:23
This must be who I'm directly descended from."
86
245000
3000
我想必是从这个起源演化来的。”
04:26
The field of paleoanthropology, I'll argue,
87
248000
3000
我得说，古生人类学
04:29
gives us lots of fascinating possibilities about our ancestry,
88
251000
3000
向我们提供了很多非常有价值的可能性，
04:32
but it doesn't give us the probabilities that we really want as scientists.
89
254000
3000
但是没有给我们提供每种可能性的概率，那才是科学家们真正需要的。
04:35
What do I mean by that?
90
257000
2000
怎么说呢？
04:37
You're looking at a great example here.
91
259000
2000
这里是个很好的例子：
04:39
These are three extinct species of hominids,
92
261000
2000
三个灭绝了的原始人种，
04:41
potential human ancestors.
93
263000
2000
每个都可能是人类的祖先。
04:43
All dug up just west of here in Olduvai Gorge, by the Leakey family.
94
265000
3000
它们都是在 Olduvai Gorge 以西被 Leakey 家族发掘的。
04:46
And they're all dating to roughly the same time.
95
268000
2000
它们也都是从差不多同一个时期来的。
04:48
From left to right, we've got Homo erectus, Homo habilis,
96
270000
2000
从左到右，我们有直立人，能人
04:50
and Australopithecus -- now called Paranthropus boisei,
97
272000
3000
和南方古猿 — 现在叫做鲍氏傍人的，
04:53
the robust australopithecine. Three extinct species, same place, same time.
98
275000
5000
也就是更新世灵长类动物。三个已经灭绝的物种，存在于同一个空间，同一个时间。
04:58
That means that not all three could be my direct ancestor.
99
280000
3000
这说明不可能每一个都是我们的祖先。
05:01
Which one of these guys am I actually related to?
100
283000
3000
到底哪一个是呢？
05:04
Possibilities about our ancestry, but not the probabilities that we're really looking for.
101
286000
5000
都有可能性，但是我们要看的是哪个机率更大。
05:10
Well, a different approach has been to look at morphology in humans
102
292000
4000
另一个方法是看人体形态
05:14
using the only data that people really had at hand until quite recently --
103
296000
3000
这也是最近才有的方法 —
05:17
again, largely skull shape.
104
299000
2000
大部分是靠头骨的形状。
05:19
The first person to do this systematically was Linnaeus,
105
301000
4000
第一个系统地做这件事的人叫 Linnaeus，
05:23
Carl von Linne, a Swedish botanist,
106
305000
2000
Carl von Linne， 是个瑞士植物学家，
05:25
who in the eighteenth century took it upon himself
107
307000
2000
十八世纪的人，自己一个人
05:27
to categorize every living organism on the planet.
108
309000
2000
把地球上所有存在的生物分了类。
05:29
You think you've got a tough job?
109
311000
2000
你还抱怨你的工作难做么？
05:31
And he did a pretty good job.
110
313000
2000
他还做得很不错。
05:33
He categorized about 12,000 species in "Systema Naturae."
111
315000
4000
他把大约一万两千种不同的物种分了类。
05:37
He actually coined the term Homo sapiens -- it means wise man in Latin.
112
319000
3000
还创造了“智人”这个名词 — 拉丁文中的意思是“有智慧的人”。
05:40
But looking around the world at the diversity of humans, he said,
113
322000
4000
但是看看世界上那么多不同的人种，他说：
05:44
"Well, you know, we seem to come in discreet sub-species or categories."
114
326000
4000
“你知道，我们看起来是差别细微的亚种，或者只是不同类的智人。”
05:48
And he talked about Africans and Americans and Asians and Europeans,
115
330000
4000
他提到了非洲人，美洲人，亚洲人和欧洲人，
05:52
and a blatantly racist category he termed "Monstrosus,"
116
334000
3000
也公然地把所有他不喜欢的人种
05:55
which basically included all the people he didn't like,
117
337000
3000
一古脑儿归类成 “monstrosus”，
05:58
including imaginary folk like elves.
118
340000
3000
其中还包括了想象中的人物，比如精灵。
06:02
It's easy to dismiss this as the perhaps well-intentioned
119
344000
5000
我们很容易对这个结果嗤之以鼻，
06:07
but ultimately benighted musings of an eighteenth century scientist
120
349000
3000
虽然这个研究的意图是好的，
06:10
working in the pre-Darwinian era.
121
352000
2000
毕竟这是达尔文出现前十八世纪的比较愚昧的研究。
06:12
Except, if you had taken physical anthropology
122
354000
2000
不过，如果你去上人类学的课，
06:14
as recently as 20 or 30 years ago, in many cases you would have learned
123
356000
4000
大概二三十年前，
06:18
basically that same classification of humanity.
124
360000
2000
很多时候你还是学的同样的人类分类法呢。
06:20
Human races that according to physical anthropologists of 30, 40 years ago --
125
362000
5000
人类种族，在三四十年前的人类学家来看 —
06:25
Carlton Coon is the best example --
126
367000
2000
Carlton Coon 是最好的例子 —
06:27
had been diverging from each other -- this was in the post-Darwinian era --
127
369000
4000
从直立人时代以来，已经相互分离了 — 这已经是后达尔文时代了 —
06:31
for over a million years, since the time of Homo erectus.
128
373000
3000
一百万年还不止。
06:34
But based on what data?
129
376000
2000
但是有什么证据呢？
06:36
Very little. Very little. Morphology and a lot of guesswork.
130
378000
4000
很少，几乎没有。形态学和很多猜想而已。
06:40
Well, what I'm going to talk about today,
131
382000
2000
我今天要介绍给大家的。
06:42
what I'm going to talk about now is a new approach to this problem.
132
384000
3000
现在要讲的，是一个全新的研究方法。
06:45
Instead of going out and guessing about our ancestry,
133
387000
3000
不是光靠出去满处挖掘，
06:48
digging things up out of the ground, possible ancestors,
134
390000
2000
猜想谁是你可能的祖先，
06:50
and saying it on the basis of morphology --
135
392000
2000
就靠着谁长得像，
06:52
which we still don't completely understand,
136
394000
2000
更别提我们还不太明白怎么确定谁长得像呢。
06:54
we don't know the genetic causes underlying this morphological variation --
137
396000
4000
因为我们并不完全理解基因变异怎么导致了形态的改变。
06:58
what we need to do is turn the problem on its head.
138
400000
2000
我们要做的是变被动为主动，
07:00
Because what we're really asking is a genealogical problem,
139
402000
4000
因为说到底这是一个家谱的研究。
07:04
or a genealogical question.
140
406000
2000
或者说是家谱问题。
07:06
What we're trying to do is construct a family tree for everybody alive today.
141
408000
5000
我们试图做的是给每个人画一个家谱，
07:11
And as any genealogist will tell you --
142
413000
2000
就像家谱学家对你说的 —
07:13
anybody have a member of the family, or maybe you
143
415000
2000
有没有谁家族里有人，或者就是你自己，
07:15
have tried to construct a family tree, trace back in time?
144
417000
3000
试图追根溯源，画出家谱的？
07:18
You start in the present, with relationships you're certain about.
145
420000
2000
你从确信对的亲属关系开始，
07:20
You and your siblings, you have a parent in common.
146
422000
2000
你和你的兄弟姐妹，同样的父母，
07:22
You and your cousins share a grandparent in common.
147
424000
2000
然后加上你的表亲，你们的祖父母是相同的。
07:24
You gradually trace further and further back into the past,
148
426000
3000
你渐渐回溯到越来越早，
07:27
adding these ever more distant relationships.
149
429000
2000
加上更多的远亲。
07:29
But eventually, no matter how good you are at digging up the church records,
150
431000
4000
但是最终，不管你有多么能干，发掘了教堂的记载，
07:33
and all that stuff, you hit what the genealogists call a brick wall.
151
435000
4000
所有的来源，你还是会遇到一个家谱学家所说的“碰壁”。
07:37
A point beyond which you don't know anything else about your ancestors,
152
439000
3000
也就是你实在找不出更多的信息了。
07:40
and you enter this dark and mysterious realm we call history
153
442000
4000
你会陷入历史的迷雾，
07:44
that we have to feel our way through with whispered guidance.
154
446000
3000
只能靠着细小的声音找寻出路。
07:47
Who were these people who came before?
155
449000
2000
这些人是谁？谁先谁后？
07:49
We have no written record. Well, actually, we do.
156
451000
3000
我们没有纸上记载。事实上，我们有记录保存下来。
07:52
Written in our DNA, in our genetic code --
157
454000
3000
信息都记在我们的DNA里，在我们的基因书中。
07:55
we have a historical document that takes us back in time
158
457000
2000
就像一本历史长卷，把我们带回过去，
07:57
to the very earliest days of our species. And that's what we study.
159
459000
4000
带到我们人种最早的年代去。这就是我们要研究的。
08:01
Now, a quick primer on DNA.
160
463000
2000
现在，简单介绍一下DNA。
08:03
I suspect that not everybody in the audience is a geneticist.
161
465000
3000
我猜不是每个听众都是遗传学家。
08:06
It is a very long, linear molecule, a coded version
162
468000
4000
DNA是个非常长的线状物，一个如何复制你自己的密码书，
08:10
of how to make another copy of you. It's your blueprint.
163
472000
3000
也是你的蓝图。
08:13
It's composed of four subunits: A, C, G and T, we call them.
164
475000
3000
DNA有四个成分组成：A，C，G和T。
08:16
And it's the sequence of those subunits that defines that blueprint.
165
478000
4000
这四个成分的组合顺序决定了蓝图，
08:20
How long is it? Well, it's billions of these subunits in length.
166
482000
3000
DNA有多长？有上百亿个成分组成。
08:23
A haploid genome -- we actually have two copies of all of our chromosomes --
167
485000
3000
我们的基因是双份的，我们的染色体有一式两份，
08:26
a haploid genome is around 3.2 billion nucleotides in length.
168
488000
4000
每份基因有三十二亿核酸那么长，
08:30
And the whole thing, if you add it all together,
169
492000
2000
如果你把所有的染色体连起来，
08:32
is over six billion nucleotides long.
170
494000
2000
就有多于六十亿核酸长。
08:34
If you take all the DNA out of one cell in your body,
171
496000
3000
如果你把你体内一个细胞的DNA拿出来，
08:37
and stretch it end to end, it's around two meters long.
172
499000
4000
头尾相连，大概是两米长。
08:41
If you take all the DNA out of every cell in your body,
173
503000
2000
如果你把你体内每一个细胞的DNA都拿出来，
08:43
and you stretch it end to end, it would reach from here to the moon and back,
174
505000
4000
头尾相连，可以从地球到月球再回来，
08:47
thousands of times. It's a lot of information.
175
509000
3000
往返成千上万次。这里包含了很多的信息。
08:50
And so when you're copying this DNA molecule to pass it on, it's a pretty tough job.
176
512000
6000
当你复制这些DNA时，试图把信息传到下一代时，是个很难的工作。
08:56
Imagine the longest book you can think of, "War and Peace."
177
518000
4000
想象你知道得最长的书，比如战争与和平，
09:00
Now multiply it by 100.
178
522000
2000
乘上一百倍，
09:02
And imagine copying that by hand.
179
524000
2000
然后想象你手抄这些书，
09:04
And you're working away until late at night,
180
526000
2000
直到深夜，
09:06
and you're very, very careful, and you're drinking coffee
181
528000
2000
你非常非常小心，喝咖啡保持清醒，
09:08
and you're paying attention, but, occasionally,
182
530000
2000
你注意力高度集中，但是时不时地，
09:10
when you're copying this by hand,
183
532000
2000
当你手抄的时候，
09:12
you're going to make a little typo, a spelling mistake --
184
534000
2000
还是会出错 — 抄错字母。
09:14
substitute an I for an E, or a C for a T.
185
536000
4000
本来是 I 写成了 E，本来是 C 写成了 T。
09:18
Same thing happens to our DNA as it's being passed on through the generations.
186
540000
4000
这种事情在DNA复制的时候也会发生。
09:22
It doesn't happen very often. We have a proofreading mechanism built in.
187
544000
3000
不常发生，因为我们有查错和纠错的系统，
09:25
But when it does happen, and these changes get transmitted down
188
547000
2000
但是一旦发生了，这些改变会传到下一代，
09:27
through the generations, they become markers of descent.
189
549000
3000
刚好变成了世代相传的标签。
09:30
If you share a marker with someone,
190
552000
2000
如果你和别人有一个相同标签，
09:32
it means you share an ancestor at some point in the past,
191
554000
3000
这说明你们血脉相连。
09:35
the person who first had that change in their DNA.
192
557000
2000
都能连回到那个第一次产生这个标签的人。
09:37
And it's by looking at the pattern of genetic variation,
193
559000
3000
通过观察基因变异的类型，
09:40
the pattern of these markers in people all over the world,
194
562000
3000
全世界人们携带的标签的类型，
09:43
and assessing the relative ages when they occurred throughout our history,
195
565000
4000
来分析标签产生的年代，
09:47
that we've been able to construct a family tree for everybody alive today.
196
569000
3000
正是我们用来给每个人创造家谱的方法。
09:50
These are two pieces of DNA that we use quite widely in our work.
197
572000
3000
这里有两个DNA片断，我们用的很多，
09:53
Mitochondrial DNA, tracing a purely maternal line of descent.
198
575000
3000
一个是线粒体DNA，总是从母亲那里来，
09:56
You get your mtDNA from your mother, and your mother's mother,
199
578000
3000
你从你妈妈那里得到线粒体DNA，你妈妈从她的妈妈那里得到，
09:59
all the way back to the very first woman.
200
581000
2000
一直追回到第一个人类女性。
10:01
The Y chromosome, the piece of DNA that makes men men,
201
583000
3000
还有就是Y染色体，雄性染色体，
10:04
traces a purely paternal line of descent.
202
586000
3000
能够追溯父系信息。
10:07
Everybody in this room, everybody in the world,
203
589000
4000
这屋里的每个人，这世界上的每个人，
10:11
falls into a lineage somewhere on these trees.
204
593000
4000
都能在这些家谱里找到位置。
10:15
Now, even though these are simplified versions of the real trees,
205
597000
3000
现在，即使这些是简化了的家谱，
10:18
they're still kind of complicated, so let's simplify them.
206
600000
2000
它们还是很复杂，让我们用更简单的方法看，
10:20
Turn them on their sides, combine them so that they look like a tree
207
602000
2000
把它们侧过来，汇总变成一棵树的样子，
10:22
with the root at the bottom and the branches going up.
208
604000
3000
下面有根上面有树枝。
10:25
What's the take-home message?
209
607000
2000
到底说明什么？
10:27
Well, the thing that jumps out at you first
210
609000
2000
你最先注意到的
10:29
is that the deepest lineages in our family trees
211
611000
3000
是最深的世代，
10:32
are found within Africa, among Africans.
212
614000
5000
是从非洲来的，非洲人。
10:37
That means that Africans have been accumulating
213
619000
3000
这说明非洲人集聚了最长时间的
10:40
this mutational diversity for longer.
214
622000
3000
基因变异，
10:43
And what that means is that we originated in Africa. It's written in our DNA.
215
625000
4000
这说明了我们都是从非洲起源的。这是写在DNA里的。
10:47
Every piece of DNA we look at has greater diversity within Africa than outside of Africa.
216
629000
5000
每一个我们研究的DNA片断都在非洲内有更深的多样性。
10:52
And at some point in the past, a sub-group of Africans
217
634000
3000
过去的每个时期，一部分非洲人，
10:55
left the African continent to go out and populate the rest of the world.
218
637000
4000
离开了非洲大陆，在世界的其他地方定居了。
10:59
Now, how recently do we share this ancestry?
219
641000
2000
现在的问题是，这发生在多久以前？
11:01
Was it millions of years ago, which we might suspect
220
643000
4000
是在几百万年前么？如我们
11:05
by looking at all this incredible variation around the world?
221
647000
3000
从全世界这么多不同的人种来猜想的一样?
11:08
No, the DNA tells a story that's very clear.
222
650000
3000
不是的。DNA把历史弄得很清楚，
11:11
Within the last 200,000 years, we all share an ancestor, a single person --
223
653000
5000
在过去的二十万年中，我们有共同的祖先，同一个人，
11:16
Mitochondrial Eve, you might have heard about her -- in Africa,
224
658000
4000
线粒体 Eve — 你可能听说过她 — 在非洲。
11:20
an African woman who gave rise to all the mitochondrial diversity in the world today.
225
662000
3000
这一个非洲女性，就是现今全世界多种多样的线粒体的起源。
11:23
But what's even more amazing
226
665000
2000
更令人惊奇的是，
11:25
is that if you look at the Y-chromosome side,
227
667000
2000
如果你看 Y 染色体，
11:27
the male side of the story, the Y-chromosome Adam
228
669000
4000
男性这边， Y 染色体亚当，
11:31
only lived around 60,000 years ago.
229
673000
2000
存在于六万年前。
11:33
That's only about 2,000 human generations,
230
675000
3000
从他数来只不过两千代的人类历史。
11:36
the blink of an eye in an evolutionary sense.
231
678000
3000
对于进化史来说，这不过是一眨眼间的事。
11:40
That tells us we were all still living in Africa at that time.
232
682000
3000
这告诉我们六万年前我们还都生活在非洲，
11:43
This was an African man who gave rise
233
685000
2000
一个非洲男性
11:45
to all the Y chromosome diversity around the world.
234
687000
2000
把 Y 染色体传给了全世界。
11:47
It's only within the last 60,000 years
235
689000
2000
仅仅是过去的六万年里，
11:49
that we have started to generate this incredible diversity we see around the world.
236
691000
4000
我们人类产生了这个令人难以置信的多样性。
11:53
Such an amazing story.
237
695000
2000
多么令人惊叹。
11:55
We're all effectively part of an extended African family.
238
697000
3000
我们都是这个非洲大家族的一部分。
11:59
Now, that seems so recent. Why didn't we start to leave earlier?
239
701000
3000
看起来这并不是很久以前，为什么我们早没有离开非洲大陆呢？
12:02
Why didn't Homo erectus evolve into separate species,
240
704000
4000
为什么直立人没有发展成不同的人种，
12:06
or sub-species rather, human races around the world?
241
708000
2000
或者亚种，而是变成了现在世界上的种族？
12:08
Why was it that we seem to have come out of Africa so recently?
242
710000
4000
为什么我们这么晚才从非洲出来？
12:12
Well, that's a big question. These "why" questions,
243
714000
2000
这是个很重要的问题。这些“为什么”的问题。
12:14
particularly in genetics and the study of history in general, are always the big ones,
244
716000
5000
尤其是对遗传学和人类史学来说，都一直是很重要的问题。
12:19
the ones that are tough to answer.
245
721000
2000
这些问题很难回答。
12:21
And so when all else fails, talk about the weather.
246
723000
3000
所以我们把注意力转到气候的变化上。
12:24
What was going on to the world's weather around 60,000 years ago?
247
726000
3000
六万年前，世界的气候是什么样的？
12:27
Well, we were going into the worst part of the last ice age.
248
729000
3000
那时候是最后一个冰河时期的最糟糕的一个时候。
12:30
The last ice age started roughly 120,000 years ago.
249
732000
3000
最后的一个冰河时期始于十二万年前，
12:33
It went up and down, and it really started to accelerate around 70,000 years ago.
250
735000
4000
开始不稳定，后来在七万年前加速，
12:37
Lots of evidence from sediment cores
251
739000
2000
从沉积物，
12:39
and the pollen types, oxygen isotopes and so on.
252
741000
3000
花粉类型，和氧同位素研究方面有很多证据。
12:42
We hit the last glacial maximum around 16,000 years ago,
253
744000
3000
在一万六千年前我们到达了最后的冰河时代，
12:45
but basically, from 70,000 years on, things were getting really tough,
254
747000
4000
但基本上从七万年前开始，气候变得很严酷。
12:49
getting very cold. The Northern Hemisphere had massive growing ice sheets.
255
751000
5000
变得很冷。北半球全是冰层，
12:54
New York City, Chicago, Seattle, all under a sheet of ice.
256
756000
4000
纽约，芝加哥，西雅图，这些地区全在冰下。
12:58
Most of Britain, all of Scandinavia, covered by ice several kilometers thick.
257
760000
5000
英国大部分，整个斯堪的那维亚半岛，全被数千米的冰层覆盖。
13:03
Now, Africa is the most tropical continent on the planet --
258
765000
3000
那时，非洲是整个星球上最热带的大陆 —
13:06
about 85 percent of it lies between Cancer and Capricorn --
259
768000
4000
大约百分之八十五处在巨蟹和摩羯座之间，
13:10
and there aren't a lot of glaciers here,
260
772000
2000
也没有什么冰河，
13:12
except on the high mountains here in East Africa.
261
774000
2000
除了在东非的一些高山上。
13:14
So what was going on here? We weren't covered in ice in Africa.
262
776000
3000
那里发生了什么呢？我们没有被盖在冰下，
13:17
Rather, Africa was drying out at that time.
263
779000
3000
但是，非洲变得非常干燥。
13:20
This is a paleo-climatological map
264
782000
2000
这是个古气候图，
13:22
of what Africa looked like between 60,000 and 70,000 years ago,
265
784000
3000
显示了七万年前到六万年前非洲的样子，
13:25
reconstructed from all these pieces of evidence that I mentioned before.
266
787000
4000
这是从所有我之前提到的证据拼起来的。
13:29
The reason for that is that ice actually sucks moisture out of the atmosphere.
267
791000
4000
气候干燥的原因是冰层事实上从大气中吸收水分。
13:33
If you think about Antarctica, it's technically a desert, it gets so little precipitation.
268
795000
4000
试着想象一下南极洲，简直就是个沙漠，没什么降水。
13:37
So the whole world was drying out.
269
799000
2000
所以当时整个世界都变得干燥了。
13:39
The sea levels were dropping. And Africa was turning to desert.
270
801000
4000
海平面下降，非洲变成了沙漠。
13:43
The Sahara was much bigger then than it is now.
271
805000
3000
当时的撒哈拉沙漠比现在的大很多，
13:46
And the human habitat was reduced to just a few small pockets,
272
808000
3000
人类的居住地变成了很小的一块块，
13:49
compared to what we have today.
273
811000
2000
和我们今天的活动范围相比。
13:51
The evidence from genetic data
274
813000
2000
遗传学的证据表明，
13:53
is that the human population around this time, roughly 70,000 years ago,
275
815000
3000
这时候的人类数量，大约七万年前，
13:56
crashed to fewer than 2,000 individuals.
276
818000
3000
掉到少于两千人。
13:59
We nearly went extinct. We were hanging on by our fingernails.
277
821000
4000
我们差一点就灭绝了。我们就差一点点就完了。
14:03
And then something happened. A great illustration of it.
278
825000
3000
接着分支才发生的。这里有个很好的图解，
14:06
Look at some stone tools.
279
828000
2000
看到这些石器了么，
14:08
The ones on the left are from Africa, from around a million years ago.
280
830000
4000
左边的这些是从非洲发掘的，来自大概一百万年前，
14:12
The ones on the right were made by Neanderthals, our distant cousins,
281
834000
3000
右边的这些是尼安德特人作的，他们是我们的远祖表亲，
14:15
not our direct ancestors, living in Europe,
282
837000
2000
并不是直系祖先，他们生活在欧洲。
14:17
and they date from around 50,000 or 60,000 years ago.
283
839000
4000
他们在五万年六万年前灭绝了。
14:21
Now, at the risk of offending any paleoanthropologists
284
843000
3000
现在，冒着对观众中的
14:24
or physical anthropologists in the audience,
285
846000
3000
古人类学家以及人类学家不敬的危险，
14:27
basically there's not a lot of change between these two stone tool groups.
286
849000
5000
这两种石器间基本上没什么进化。
14:32
The ones on the left are pretty similar to the ones on the right.
287
854000
3000
左边的看起来和右边得很像。
14:35
We are in a period of long cultural stasis from a million years ago
288
857000
4000
我们处在进化休止期，始于一百万年前，
14:39
until around 60,000 to 70,000 years ago.
289
861000
2000
直到七万年前到六万年前左右。
14:41
The tool styles don't change that much.
290
863000
2000
这些工具没有怎么进化。
14:43
The evidence is that the human way of life
291
865000
2000
这个证据表明，人类的生活方式
14:45
didn't change that much during that period.
292
867000
2000
在那段时间没有什么变化。
14:47
But then 50, 60, 70 thousand years ago, somewhere in that region,
293
869000
5000
但是五万年，六万年，或者七万年前，非洲的一些地方，
14:52
all hell breaks loose. Art makes its appearance.
294
874000
3000
开始产生变化了。艺术开始出现，
14:55
The stone tools become much more finely crafted.
295
877000
3000
石器工具做得精细了。
14:58
The evidence is that humans begin to specialize in particular prey species,
296
880000
2000
这些证据说明人类开始在一年中的某个时期，
15:01
at particular times of the year.
297
883000
2000
捕食特定的生物。
15:03
The population size started to expand.
298
885000
3000
人类的数量开始增长，
15:06
Probably, according to what many linguists believe,
299
888000
2000
很有可能，根据很多语言学家所说，
15:08
fully modern language, syntactic language -- subject, verb, object --
300
890000
4000
完整的现代语言，句法语言 — 有主语，动词，宾语的 —
15:12
that we use to convey complex ideas, like I'm doing now, appeared around that time.
301
894000
4000
就像我现在用来的传达复杂信息的语言，也是这时候开始出现的。
15:16
We became much more social. The social networks expanded.
302
898000
4000
我们变得更社会性了，社交网络开始变大，
15:20
This change in behavior allowed us to survive these worsening conditions in Africa,
303
902000
5000
这种行为上的进化帮助我们在非洲气候变坏的时候存活下来，
15:25
and they allowed us to start to expand around the world.
304
907000
4000
也帮助我们开始迁移到全世界。
15:30
We've been talking at this conference about African success stories.
305
912000
3000
在这个会上我们讨论了很多非洲的成功之处，
15:33
Well, you want the ultimate African success story?
306
915000
3000
这里，你想要听一个最基本的非洲成功的故事么？
15:36
Look in the mirror. You're it. The reason you're alive today
307
918000
3000
照照镜子，你就是。今天你能够在这里存活，
15:39
is because of those changes in our brains that took place in Africa --
308
921000
4000
是因为那时候在非洲人类脑子里的变化。
15:43
probably somewhere in the region where we're sitting right now,
309
925000
3000
恐怕就发生在我们现在坐的地方，
15:46
around 60, 70 thousand years ago --
310
928000
3000
六万或者七万年前。
15:49
allowing us not only to survive in Africa, but to expand out of Africa.
311
931000
3000
这些变化让我们不光是在非洲存活，也迁移到了非洲之外。
15:52
An early coastal migration along the south coast of Asia,
312
934000
3000
早期的海岸线迁移，顺着非洲南海岸，
15:55
leaving Africa around 60,000 years ago,
313
937000
2000
在六万年前离开非洲大陆，
15:57
reaching Australia very rapidly, by 50,000 years ago.
314
939000
4000
五万年前抵达了澳洲。
16:01
A slightly later migration up into the Middle East.
315
943000
2000
稍晚一点，另一部分人迁移到了中东，
16:03
These would have been savannah hunters.
316
945000
2000
这些是所谓的草原猎手。
16:05
So those of you who are going on one of the post-conference tours,
317
947000
2000
你们有谁在开会后作旅行的，
16:07
you'll get to see what a real savannah is like.
318
949000
2000
你会看到真正的草原猎手是什么样子的。
16:09
And it's basically a meat locker.
319
951000
2000
他们基本上是嗜肉的，
16:11
People who would have specialized in killing the animals,
320
953000
3000
进化成为特级的捕杀动物的人，
16:14
hunting the animals on those meat locker savannahs, moving up,
321
956000
3000
这些草原猎人猎杀动物，向北迁移，
16:17
following the grasslands into the Middle East around 45,000 years ago,
322
959000
4000
在四万五千年前沿着草原进入中东。
16:21
during one of the rare wet phases in the Sahara.
323
963000
2000
那时撒哈拉有一个少见的湿润期。
16:23
Migrating eastward, following the grasslands,
324
965000
3000
接着他们向东迁移，还是沿着草原，
16:26
because that's what they were adapted to live on.
325
968000
2000
因为这是适合他们生活的气候，
16:28
And when they reached Central Asia,
326
970000
2000
接着他们到了亚洲中部
16:30
they reached what was effectively a steppe super-highway,
327
972000
3000
沿着这个草原高速路，
16:33
a grassland super-highway.
328
975000
2000
草原高速通道。
16:35
The grasslands at that time -- this was during the last ice age --
329
977000
2000
那时的草原，还是最后的冰河时期，
16:37
stretched basically from Germany all the way over to Korea,
330
979000
3000
从德国一直延伸到韩国，
16:40
and the entire continent was open to them.
331
982000
2000
整个亚洲大陆都是草原。
16:42
Entering Europe around 35,000 years ago,
332
984000
2000
人类在三万五千年前进入欧洲，
16:44
and finally, a small group migrating up
333
986000
2000
最后，一小部分跨越最严酷的气候，
16:46
through the worst weather imaginable, Siberia,
334
988000
4000
来到了西伯利亚，
16:50
inside the Arctic Circle, during the last ice age --
335
992000
2000
进入北极圈，还是在最后的冰河时期。
16:52
temperature was at -70, -80, even -100, perhaps --
336
994000
4000
这时候气温是大约负七十华氏，或者负八十，甚至负一百。
16:56
migrating into the Americas, ultimately reaching that final frontier.
337
998000
4000
他们到了美洲，基本上是最后的前沿。
17:00
An amazing story, and it happened first in Africa.
338
1002000
4000
这个是很动人的故事，最先起源是非洲。
17:04
The changes that allowed us to do that,
339
1006000
2000
这些变化给了我们机会，
17:06
the evolution of this highly adaptable brain that we all carry around with us,
340
1008000
3000
进化出这个高度适应性的大脑，我们能带着走，
17:09
allowing us to create novel cultures,
341
1011000
2000
使我们有机会创造新的文化，
17:11
allowing us to develop the diversity
342
1013000
3000
使我们有机会变得多种多样，
17:14
that we see on a whirlwind trip like the one I've just been on.
343
1016000
3000
就像我在之前的旅行中看到的一样。
17:18
Now, that story I just told you is literally a whirlwind tour
344
1020000
4000
我给你讲的这个人类进化的故事，就像一个旋风式的旅行
17:22
of how we populated the world, the great Paleolithic wanderings of our species.
345
1024000
5000
一个人类如何迁移到整个世界的旅行，旧石器时代的奇迹。
17:27
And that's the story that I told a couple of years ago
346
1029000
2000
这也是我在几年前
17:29
in my book, "The Journey of Man," and a film that we made with the same title.
347
1031000
4000
发表的书中讲的故事。“人类的旅程”，以及我们制作的同名电影中讲的故事。
17:33
And as we were finishing up that film --
348
1035000
3000
当我们完成这部电影的时候 —
17:36
it was co-produced with National Geographic --
349
1038000
2000
这部电影是和国家地理杂志合作的 —
17:38
I started talking to the folks at NG about this work.
350
1040000
3000
我开始和国家地理杂志的同事们谈起我的研究。
17:41
And they got really excited about it. They liked the film, but they said,
351
1043000
4000
他们觉得很激动，他们喜欢这部电影，但是他们问：
17:45
"You know, we really see this as kind of
352
1047000
2000
“你知道，我们真的觉得
17:47
the next wave in the study of human origins, where we all came from,
353
1049000
4000
这时研究人类起源，研究我们从哪里来的的新潮流。
17:51
using the tools of DNA to map the migrations around the world.
354
1053000
5000
用这些DNA工具来做一个人类迁移的地图。
17:56
You know, the study of human origins is kind of in our DNA,
355
1058000
2000
既然这个人类起源的研究都在我们的DNA中，
17:58
and we want to take it to the next level.
356
1060000
2000
我们想进一步做这个故事。
18:00
What do you want to do next?"
357
1062000
2000
你下一步的计划是什么？”
18:02
Which is a great question to be asked by National Geographic.
358
1064000
2000
国家地理杂志问了个很好的问题。
18:04
And I said, "Well, you know, what I've sketched out here is just that.
359
1066000
4000
我说，你知道，我画的这个图只是
18:08
It is a very coarse sketch of how we migrated around the planet.
360
1070000
4000
非常粗糙的，给你看我们在整个地球上是怎么迁移的。
18:12
And it's based on a few thousand people we've sampled from,
361
1074000
3000
这些数据只是从我们采样的几千个人中来的
18:15
you know, a handful of populations around the world.
362
1077000
2000
只是世界各地很少的一点数据
18:17
Studied a few genetic markers, and there are lots of gaps on this map.
363
1079000
4000
我们只研究了几个基因标记，这个地图上还有很多的间隙。
18:21
We've just connected the dots. What we need to do
364
1083000
2000
我们只是连起了几个点而已。我们现在要做的，
18:23
is increase our sample size by an order of magnitude or more --
365
1085000
4000
是增加我们采样的人数，至少十倍，
18:27
hundreds of thousands of DNA samples from people all over the world."
366
1089000
4000
我们需要成千上万世界各地的人的DNA样本。
18:31
And that was the genesis of the Genographic Project.
367
1093000
3000
这才是刚刚是基因地理学的开始。
18:34
The project launched in April 2005.
368
1096000
3000
这个项目始于2005年四月，
18:37
It has three core components. Obviously, science is a big part of it.
369
1099000
4000
包括三个核心项目，当然科学方面是一个。
18:41
The field research that we're doing around the world with indigenous peoples.
370
1103000
3000
另一个是实地考察，我们和世界各地的土著们做的
18:44
People who have lived in the same location for a long period of time
371
1106000
3000
所谓土著是指在同一个地方生活了很长时间的人，
18:47
retain a connection to the place where they live
372
1109000
2000
我们能够通过他们生活的地方建立地图的联系，
18:49
that many of the rest of us have lost.
373
1111000
2000
这是在我们大多数人身上做不到的。
18:52
So my ancestors come from all over northern Europe.
374
1114000
2000
比如我的祖先是从欧洲各地来的，
18:54
I live in the Eastern Seaboard of North America when I'm not traveling.
375
1116000
3000
我本人定居在北美东海岸，
18:57
Where am I indigenous to? Nowhere really. My genes are all jumbled up.
376
1119000
3000
我的家乡是哪里呢？哪儿也不是。我的基因在地图上跳来跳去地混乱了。
19:00
But there are people who retain that link to their ancestors
377
1122000
3000
但是有的土著们还能够追随到很远的祖先，
19:03
that allows us to contextualize the DNA results.
378
1125000
3000
这给我们提供了机会把DNA结果联系起来。
19:06
That's the focus of the field research,
379
1128000
2000
这就是这个研究项目的重点。
19:08
the centers that we've set up all over the world --
380
1130000
2000
我们在世界各地设了点，
19:10
10 of them, top population geneticists.
381
1132000
3000
十个点，都是顶尖的遗传学家。
19:13
But, in addition, we wanted to open up this study to anybody around the world.
382
1135000
3000
更进一步，我们希望把这个科学研究向全世界所有人开放。
19:16
How often do you get to participate in a big scientific project?
383
1138000
4000
你多久一次能有机会参加一个大型科研项目？
19:20
The Human Genome Project, or a Mars Rover mission.
384
1142000
2000
就像是人类基因组计划，或者火星探索？
19:22
In this case, you actually can.
385
1144000
2000
这次你有机会了。
19:24
You can go onto our website, Nationalgeographic.com/genographic.
386
1146000
4000
你可以上我们的网站，Nationalgeographic.com/genographic
19:28
You can order a kit. You can test your own DNA.
387
1150000
3000
定一个匣子，用里面的东西你能测试自己的DNA。
19:31
And you can actually submit those results to the database,
388
1153000
3000
你还能把结果提交给我们的数据库，
19:34
and tell us a little about your genealogical background,
389
1156000
2000
再告诉我们一些你的家庭历史
19:36
have the data analyzed as part of the scientific effort.
390
1158000
4000
我们就会分析你的DNA数据，当作是这个科研的一部分。
19:40
Now, this is all a nonprofit enterprise, and so the money that we raise,
391
1162000
4000
这都不是为了赚钱的。所有的所得，
19:44
after we cover the cost of doing the testing and making the kit components,
392
1166000
3000
除去我们做测试和准备这个匣子的费用，
19:47
gets plowed back into the project.
393
1169000
2000
都用来支持这个计划。
19:49
The majority going to something we call the Legacy Fund.
394
1171000
2000
大部分会用来当作保留费用，
19:51
It's a charitable entity, basically a grant-giving entity
395
1173000
4000
这是用来做慈善事业的钱，本质上是一个给出经费的机构，
19:55
that gives money back to indigenous groups around the world
396
1177000
2000
把钱给世界各地的土著们，
19:57
for educational, cultural projects initiated by them.
397
1179000
4000
用来发展教育，文化。
20:01
They apply to this fund in order to do various projects,
398
1183000
2000
他们订计划我们经费支持，他们把经费用在各种项目上。
20:03
and I'll show you a couple of examples.
399
1185000
2000
让我给你们几个例子。
20:05
So how are we doing on the project? We've got about 25,000 samples
400
1187000
3000
现在这个项目在做什么呢？我们已经得到了两万五千个样本，
20:08
collected from indigenous people around the world.
401
1190000
2000
从全世界各地的人种上得到的。
20:10
The most amazing thing has been the interest on the part of the public;
402
1192000
3000
最令人惊奇的公众的兴趣。
20:13
210,000 people have ordered these participation kits
403
1195000
3000
两年来二十一万人
20:16
since we launched two years ago,
404
1198000
2000
购买了我们的匣子。
20:18
which has raised around five million dollars,
405
1200000
3000
我们赚了五百万。
20:21
the majority of which, at least half, is going back into the Legacy Fund.
406
1203000
3000
绝大部分的钱，回流注入了这个保留基金。
20:24
We've just awarded the first Legacy Grants totaling around 500,000 dollars.
407
1206000
4000
我们刚刚给了第一个基金会五十万。
20:28
Projects around the world -- documenting oral poetry in Sierra Leone,
408
1210000
3000
用于全球范围的文化项目，比如在塞拉利昂记录保存口头流传的诗歌，
20:31
preserving traditional weaving patterns in Gaza,
409
1213000
3000
在加沙保存传统的编织式样，
20:34
language revitalization in Tajikistan, etc., etc.
410
1216000
3000
在塔克亚复兴当地语言，等等，等等。
20:37
So the project is going very, very well,
411
1219000
3000
这个项目进行得非常非常顺利。
20:40
and I urge you to check out the website and watch this space.
412
1222000
4000
而我在这里，鼓励大家都去访问我们的网页，关注我们的进展。
20:44
Thank you very much.
413
1226000
2000
谢谢大家。
20:46
(Applause)
414
1228000
2000
（掌声）
ABOUT THE SPEAKER
Spencer Wells - GenographerSpencer Wells studies human diversity -- the process by which humanity, which springs from a single common source, has become so astonishingly diverse and widespread.
Why you should listen
By analyzing DNA from people in all regions of the world, Spencer Wells has concluded that all humans alive today are descended
from a single man who lived in Africa around 60,000 to 90,000 years ago. Now, Wells is working on the follow-up question: How did this man, sometimes called "Ychromosomal Adam," become the multicultural, globe-spanning body of life known as humanity?
Wells was recently named project director of the National Geographic Society's multiyear Genographic Project, which uses DNA samples to trace human migration out of Africa. In his 2002 book The Journey of Man: A Genetic Odyssey, he shows how genetic data can trace human migrations over the past 50,000 years, as our ancestors wandered out of Africa to fill up the continents of the globe.
Spencer Wells | Speaker | TED.com