TEDxSydney
Tara Djokic: This ancient rock is changing our theory on the origin of life
塔拉·德约基奇: 这块古老的岩石正在改变生命起源理论
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地球生命究竟从何时何地起源？长期以来，科学家一直认为生命是 30 亿年前在海洋中出现的——直到天体生物学家塔拉·德约基奇（Tara Djokic）和她的团队在澳大利亚西部沙漠中的意外发现。来了解一下热火山池附近发现的古老岩石如何改变我们对生命起源之谜的理解。
Tara Djokic - Astrobiologist
Tara Djokic discovered direct evidence that indicates some of Earth's oldest life once thrived in hot springs on land. Full bio
Tara Djokic discovered direct evidence that indicates some of Earth's oldest life once thrived in hot springs on land. Full bio
Double-click the English transcript below to play the video.
00:13
The Earth is 4.6 billion years old,
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地球的寿命有46亿年，
但人类的寿命还不到100年。
00:17
but a human lifetime often lasts
for less than 100 years.
for less than 100 years.
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00:23
So why care about
the history of our planet
the history of our planet
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那我们为什么要关心地球历史呢，
它那么遥远，好像
与我们的生活完全无关。
与我们的生活完全无关。
00:26
when the distant past seems
so inconsequential to everyday life?
so inconsequential to everyday life?
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00:32
You see, as far as we can tell,
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就我们所知，
在太阳系里，只有地球
00:34
Earth is the only planet
in our solar system
in our solar system
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拥有灿烂的生命，
00:38
known to have sparked life,
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也只有地球能提供
让人类存活的环境。
让人类存活的环境。
00:40
and the only system able to provide
life support for human beings.
life support for human beings.
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00:46
So why Earth?
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为什么偏偏是地球？
00:48
We know Earth is unique
for having plate tectonics,
for having plate tectonics,
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我们知道地球是独一无二的，
它有板块构造、
它有板块构造、
表面有液体水、
00:52
liquid water on its surface
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还有富含氧气的大气层。
00:53
and an oxygen-rich atmosphere.
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00:56
But this has not always been the case,
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但并不是一直这样，
因为古岩石记录了地球演化过程中
00:58
and we know this because ancient rocks
have recorded the pivotal moments
have recorded the pivotal moments
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的每个关键时刻。
01:03
in Earth's planetary evolution.
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01:07
And one of the best places
to observe those ancient rocks
to observe those ancient rocks
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观察古岩石的最佳去处之一，
是澳大利亚西部的皮尔布拉。
01:10
is in the Pilbara of Western Australia.
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01:15
The rocks here are 3.5 billion years old,
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这里的岩石存在了 35 亿年之久，
其中藏着地球上
最早期生命的证据。
最早期生命的证据。
01:20
and they contain some of the oldest
evidence for life on the planet.
evidence for life on the planet.
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01:25
Now, often when we think of early life,
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通常，说起古生命时，
我们想到的是剑龙，
01:27
we might imagine a stegosaurus
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或者一种鱼爬到了陆地上。
01:30
or maybe a fish crawling onto land.
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01:35
But the early life that I'm talking about
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但我说的古生命，
是简单微生物，比如细菌。
01:37
is simple microscopic life, like bacteria.
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01:41
And their fossils are often preserved
as layered rock structures,
as layered rock structures,
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它们的化石通常是层叠的岩石结构，
称为叠层石。
01:45
called stromatolites.
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01:48
This simple form of life
is almost all we see in the fossil record
is almost all we see in the fossil record
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地球出现生命的前 30 亿年里，
化石记录中几乎只能见到
这种简单的生命形式。
这种简单的生命形式。
01:53
for the first three billion years
of life on Earth.
of life on Earth.
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01:58
Our species can only be traced
back in the fossil record
back in the fossil record
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在化石记录中寻找人类的踪迹，
只能追踪到几万年前。
02:01
to a few hundred thousand years ago.
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从化石记录中我们了解到，
02:04
We know from the fossil record,
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细菌生命开始得很早，
02:06
bacteria life had grabbed
a strong foothold
a strong foothold
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大约 35 至 40 亿年前就存在了。
02:10
by about 3.5 to four billion years ago.
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02:14
The rocks older than this
have been either destroyed
have been either destroyed
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而比这个时间更久的岩石，
要么被破坏了，
要么随板块运动过度变形。
要么随板块运动过度变形。
02:17
or highly deformed
through plate tectonics.
through plate tectonics.
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02:21
So what remains a missing
piece of the puzzle
piece of the puzzle
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所以遗留下来一个
待解决的难题就是，
待解决的难题就是，
地球上的生命到底是
什么时间开始的。
什么时间开始的。
02:24
is exactly when and how
life on Earth began.
life on Earth began.
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02:31
Here again is that ancient
volcanic landscape in the Pilbara.
volcanic landscape in the Pilbara.
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回到皮尔布拉的古火山地貌。
02:35
Little did I know that our research here
would provide another clue
would provide another clue
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我当时完全不知道，我们在这里
的研究会给生命起源之谜
的研究会给生命起源之谜
提供另一个线索。
02:39
to that origin-of-life puzzle.
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02:42
It was on my first field trip here,
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那是我第一次到这里实地考察，
在整整一周的地图绘制项目
快要结束时，
快要结束时，
02:45
toward the end of a full,
long week mapping project,
long week mapping project,
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我发现了一件不寻常的东西。
02:49
that I came across something
rather special.
rather special.
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02:53
Now, what probably looks like
a bunch of wrinkly old rocks
a bunch of wrinkly old rocks
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这一堆纹路横生的石头，
其实是叠层石。
02:56
are actually stromatolites.
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在这一堆的中间，是一块
小小的罕见的岩石，
小小的罕见的岩石，
02:58
And at the center of this mound
was a small, peculiar rock
was a small, peculiar rock
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像小孩的手那么大。
03:02
about the size of a child's hand.
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03:06
It took six months before we inspected
this rock under a microscope,
this rock under a microscope,
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我们花了六个月才得以
在显微镜下观察它，
在显微镜下观察它，
当时我的一位老师，
马尔科姆·沃尔特，
马尔科姆·沃尔特，
03:11
when one of my mentors
at the time, Malcolm Walter,
at the time, Malcolm Walter,
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提出这石头像硅华。
03:13
suggested the rock resembled geyserite.
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03:18
Geyserite is a rock type that only forms
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硅华是一种岩石类型，它的形成地
只在热泉池里面和边缘周围。
03:21
in and around the edges
of hot spring pools.
of hot spring pools.
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03:26
Now, in order for you to understand
the significance of geyserite,
the significance of geyserite,
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为了让各位理解硅华的重要，
我要带大家回到十九世纪。
03:29
I need to take you back
a couple of centuries.
a couple of centuries.
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03:35
In 1871, in a letter
to his friend Joseph Hooker,
to his friend Joseph Hooker,
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1871年，查尔斯·达尔文在信中
对他的朋友约瑟夫·虎克说：
03:39
Charles Darwin suggested:
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03:42
"What if life started
in some warm little pond
in some warm little pond
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“如果生命是在一些
温暖的小池塘里诞生呢——
温暖的小池塘里诞生呢——
池塘里有各种化学物质，
03:45
with all sort of chemicals
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已准备好进行更复杂的进化呢？”
03:48
still ready to undergo
more complex changes?"
more complex changes?"
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03:52
Well, we know of warm little ponds.
We call them "hot springs."
We call them "hot springs."
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我们知道这些温暖
的小池塘指的是“温泉”。
的小池塘指的是“温泉”。
在这类环境中，有热水，
03:55
In these environments, you have hot water
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从底下的岩石里溶解出矿物质。
03:58
dissolving minerals
from the underlying rocks.
from the underlying rocks.
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04:02
This solution mixes with organic compounds
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这种液体与有机化合物混合，
形成了某种化学环境，
04:07
and results in a kind of chemical factory,
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而研究人员已证明这种化学环境
可以产生简单的细胞结构，
可以产生简单的细胞结构，
04:10
which researchers have shown
can manufacture simple cellular structures
can manufacture simple cellular structures
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这种细胞结构就是
迈向生命起源的第一步。
迈向生命起源的第一步。
04:16
that are the first steps toward life.
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但达尔文写出这封信
之后的一百年，
之后的一百年，
04:19
But 100 years after Darwin's letter,
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海洋里发现了
深海热液喷口，即热泉。
深海热液喷口，即热泉。
04:21
deep-sea hydrothermal vents, or hot vents,
were discovered in the ocean.
were discovered in the ocean.
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这些也是化学环境。
04:25
And these are also chemical factories.
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这一个位于太平洋海平面以下
04:28
This one is located along
the Tonga volcanic arc,
the Tonga volcanic arc,
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1100 米的汤加火山弧。
04:31
1,100 meters below sea level
in the Pacific Ocean.
in the Pacific Ocean.
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04:37
The black smoke that you see billowing
out of these chimneylike structures
out of these chimneylike structures
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从这些烟囱一样的结构里
飘出的“黑烟”，
飘出的“黑烟”，
也是富含矿物质的液体，
04:41
is also mineral-rich fluid,
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是细菌的食物来源。
04:43
which is being fed off by bacteria.
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04:46
And since the discovery
of these deep-sea vents,
of these deep-sea vents,
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自从发现了这些深海热泉，
生命起源地的说法就聚焦在海洋。
04:49
the favored scenario for an origin of life
has been in the ocean.
has been in the ocean.
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04:54
And this is for good reason:
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这是很合理的：
04:57
deep-sea vents are well-known
in the ancient rock record,
in the ancient rock record,
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深海热泉在古岩石记录中很常见，
通常认为地球早期
整体被海洋覆盖，
整体被海洋覆盖，
05:00
and it's thought that the early Earth
had a global ocean
had a global ocean
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陆地表面极少。
05:03
and very little land surface.
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所以，地球最初拥有大量深海热泉，
05:06
So the probability that deep-sea vents
were abundant on the very early Earth
were abundant on the very early Earth
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与之非常符合的情况是
05:11
fits well with an origin of life
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生命在海洋里起源。
05:13
in the ocean.
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05:16
However ...
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但是——
05:18
our research in the Pilbara
provides and supports
provides and supports
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我们在皮尔巴拉的研究给出了
另一种视角和证据。
05:22
an alternative perspective.
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05:25
After three years, finally, we were
able to show that, in fact,
able to show that, in fact,
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三年后，我们终于能证明，实际上，
这块小石头就是硅华。
05:31
our little rock was geyserite.
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这个结论说明，
不仅皮尔巴拉有 35 亿年历史
不仅皮尔巴拉有 35 亿年历史
05:34
So this conclusion suggested
not only did hot springs exist
not only did hot springs exist
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的火山里有温泉，
05:39
in our 3.5 billion-year-old
volcano in the Pilbara,
volcano in the Pilbara,
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而且意味着，在地球的地质记录中，
05:43
but it pushed back evidence for life
living on land in hot springs
living on land in hot springs
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生命在陆地的热泉中存活的证据，
05:49
in the geological record of Earth
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向前推了 30 亿年。
05:51
by three billion years.
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05:56
And so, from a geological perspective,
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所以，从地质角度来看，
达尔文说的小池塘
是合理的生命起源地。
是合理的生命起源地。
06:00
Darwin's warm little pond
is a reasonable origin-of-life candidate.
is a reasonable origin-of-life candidate.
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06:09
Of course, it's still debatable
how life began on Earth,
how life began on Earth,
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当然，地球生命起源
的方式仍有待探讨，
的方式仍有待探讨，
也许可以永远争论下去。
06:12
and it probably always will be.
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但有一点很清楚，
生命已经蓬勃发展起来；
生命已经蓬勃发展起来；
06:15
But it is clear that it's flourished;
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它变得多样了，
06:17
it has diversified,
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还越来越复杂。
06:19
and it has become ever more complex.
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最终，到达了人类的时代，
06:21
Eventually, it reached
the age of the human,
the age of the human,
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人类这个物种开始质疑自身的存在，
06:25
a species that has begun
to question its own existence
to question its own existence
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也质疑外星球生命的存在：
06:28
and the existence of life elsewhere:
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06:32
Is there a cosmic community
waiting to connect with us,
waiting to connect with us,
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有宇宙联盟要与我们联系吗，
还是宇宙只有人类孤单存在？
06:35
or are we all there is?
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06:38
A clue to this puzzle again
comes from the ancient rock record.
comes from the ancient rock record.
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关于这个问题的线索
再次出现在古岩石记录中。
再次出现在古岩石记录中。
06:44
At about 2.5 billion years ago,
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大约 25 亿年前，
有证据表明，
细菌已经开始产生氧气，
细菌已经开始产生氧气，
06:46
there is evidence that bacteria
had begun to produce oxygen,
had begun to produce oxygen,
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有点像现在的植物产生氧气。
06:51
kind of like plants do today.
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地质学家把随后的那段时期
06:53
Geologists refer to
the period that followed
the period that followed
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称为“大氧化事件”。
06:56
as the Great Oxidation Event.
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06:59
It is implied from rocks
called banded iron formations,
called banded iron formations,
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这一推测是从称为
带状铁形成区的岩石里得出的，
带状铁形成区的岩石里得出的，
这种层层堆叠的岩石大多几百米厚，
07:04
many of which can be observed as
hundreds-of-meter-thick packages of rock
hundreds-of-meter-thick packages of rock
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位于澳大利亚西部，
07:09
which are exposed in gorges
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在横穿卡瑞吉尼国家公园的
07:11
that carve their way through
the Karijini National Park
the Karijini National Park
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峡谷里可以看到。
07:14
in Western Australia.
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07:17
The arrival of free oxygen allowed
two major changes to occur on our planet.
two major changes to occur on our planet.
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游离氧的到来让我们的星球
发生了两个重大变化。
发生了两个重大变化。
首先，氧气让复杂生命得以进化。
07:21
First, it allowed complex life to evolve.
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生命需要氧气来变大、变复杂。
07:25
You see, life needs oxygen
to get big and complex.
to get big and complex.
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07:29
And it produced the ozone layer,
which protects modern life
which protects modern life
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氧气还制造了臭氧层，
它保护现代生命
它保护现代生命
不受阳光中波紫外线辐射的伤害。
07:32
from the harmful effects
of the sun's UVB radiation.
of the sun's UVB radiation.
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07:36
So in an ironic twist, microbial life
made way for complex life,
made way for complex life,
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讽刺的是，微生物
艰难进化成复杂生命，
艰难进化成复杂生命，
在这颗星球上耗费了
07:41
and in essence, relinquished
its three-billion-year reign
its three-billion-year reign
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30 亿年的时光。
07:45
over the planet.
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07:47
Today, we humans dig up
fossilized complex life
fossilized complex life
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今天，我们人类把变成化石的
复杂生命挖出来，
复杂生命挖出来，
把它们当燃料烧掉。
07:50
and burn it for fuel.
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07:53
This practice pumps vast amounts
of carbon dioxide into the atmosphere,
of carbon dioxide into the atmosphere,
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这种行为会释放出
大量二氧化碳到大气，
大量二氧化碳到大气，
就像我们的微生物祖先一样，
07:57
and like our microbial predecessors,
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我们已经开始让这颗星球
发生了重大变化。
发生了重大变化。
08:00
we have begun to make
substantial changes to our planet.
substantial changes to our planet.
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08:04
And the effects of those
are encompassed by global warming.
are encompassed by global warming.
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这些改变的结果包括全球变暖。
08:10
Unfortunately, the ironic twist here
could see the demise of humanity.
could see the demise of humanity.
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不幸的是，这个讽刺
会指向人类的终结。
会指向人类的终结。
08:16
And so maybe the reason
we aren't connecting with life elsewhere,
we aren't connecting with life elsewhere,
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也许我们联系不到外星生物、
联系不到外星智慧生物的原因，
08:20
intelligent life elsewhere,
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是一旦智慧生物进化了，
08:22
is that once it evolves,
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就会很快自取灭亡。
08:24
it extinguishes itself quickly.
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08:28
If the rocks could talk,
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如果岩石能说话，
我感觉它们会说：
08:30
I suspect they might say this:
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08:34
life on Earth is precious.
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地球上的生命是宝贵的。
08:38
It is the product of
four or so billion years
four or so billion years
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它的诞生用了大约 40 亿年，
经历了生命与地球之间
08:43
of a delicate and complex co-evolution
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精细复杂的共同进化，
08:47
between life and Earth,
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而人类只在这 40 亿年
的最后一瞬间存在过。
的最后一瞬间存在过。
08:50
of which humans only represent
the very last speck of time.
the very last speck of time.
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08:57
You can use this information
as a guide or a forecast --
as a guide or a forecast --
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这些信息可以为你
提供指引或预测——
提供指引或预测——
或者说是解释，为什么
银河系的地球如此孤单。
银河系的地球如此孤单。
09:01
or an explanation as to why it seems
so lonely in this part of the galaxy.
so lonely in this part of the galaxy.
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09:08
But use it to gain some perspective
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但是，通过这些信息多想想吧，
09:13
about the legacy that you
want to leave behind
want to leave behind
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在这个我们称为家园的星球上，
人类要留下些什么。
09:17
on the planet that you call home.
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09:24
Thank you.
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谢谢你们。
（掌声）
09:25
(Applause)
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Translated by Yan Gao
ABOUT THE SPEAKER
Tara Djokic - AstrobiologistTara Djokic discovered direct evidence that indicates some of Earth's oldest life once thrived in hot springs on land.
Why you should listen
Tara Djokic observes the world through the lens of geology and astrobiology. During her studies as a geology graduate student, she discovered direct evidence that indicates some of Earth's oldest life once thrived in hot springs on land -- pushing back the record of land-based hot springs on Earth by approximately three billion years and supporting Darwin's theory that life may have started in some "warm little pond." Djokic's discoveries have also been used to help guide the search for life elsewhere in our solar system. She was involved in the third and fourth "Site Selection Workshops" for the NASA Mars2020 Rover, which is due to launch in July-August, 2020.
Djokic's scientific passions are equal to her passion for sharing knowledge. During her graduate studies, she designed and developed an immersive virtual field trip (VFT) that has been used to teach astrobiology at UNSW Sydney since 2016. Her geological research also led to her involvement in the IMAX documentary The Story of Earth, which (as its title suggests) illustrates Earth's approximately 4.6-billion-year history. She is a seeker of knowledge and believes all people should be encouraged to be curious about our world.
Tara Djokic | Speaker | TED.com