This ancient rock is changing our theory on the origin of life
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0:01 - 0:06The Earth is 4.6 billion years old,
-
0:06 - 0:11but a human lifetime often lasts
for less than 100 years. -
0:11 - 0:15So why care about
the history of our planet -
0:15 - 0:20when the distant past seems
so inconsequential to everyday life? -
0:21 - 0:23You see, as far as we can tell,
-
0:23 - 0:26Earth is the only planet
in our solar system -
0:26 - 0:29known to have sparked life,
-
0:29 - 0:34and the only system able to provide
life support for human beings. -
0:35 - 0:36So why Earth?
-
0:37 - 0:40We know Earth is unique
for having plate tectonics, -
0:40 - 0:42liquid water on its surface
-
0:42 - 0:44and an oxygen-rich atmosphere.
-
0:44 - 0:47But this has not always been the case,
-
0:47 - 0:52and we know this because ancient rocks
have recorded the pivotal moments -
0:52 - 0:54in Earth's planetary evolution.
-
0:56 - 0:59And one of the best places
to observe those ancient rocks -
0:59 - 1:02is in the Pilbara of Western Australia.
-
1:03 - 1:08The rocks here are 3.5 billion years old,
-
1:08 - 1:13and they contain some of the oldest
evidence for life on the planet. -
1:13 - 1:16Now, often when we think of early life,
-
1:16 - 1:19we might imagine a stegosaurus
-
1:19 - 1:22or maybe a fish crawling onto land.
-
1:23 - 1:25But the early life that I'm talking about
-
1:25 - 1:29is simple microscopic life, like bacteria.
-
1:30 - 1:34And their fossils are often preserved
as layered rock structures, -
1:34 - 1:36called stromatolites.
-
1:37 - 1:41This simple form of life
is almost all we see in the fossil record -
1:42 - 1:46for the first three billion years
of life on Earth. -
1:46 - 1:50Our species can only be traced
back in the fossil record -
1:50 - 1:52to a few hundred thousand years ago.
-
1:52 - 1:54We know from the fossil record,
-
1:54 - 1:58bacteria life had grabbed
a strong foothold -
1:58 - 2:02by about 3.5 to four billion years ago.
-
2:02 - 2:06The rocks older than this
have been either destroyed -
2:06 - 2:09or highly deformed
through plate tectonics. -
2:10 - 2:12So what remains a missing
piece of the puzzle -
2:12 - 2:17is exactly when and how
life on Earth began. -
2:19 - 2:23Here again is that ancient
volcanic landscape in the Pilbara. -
2:23 - 2:28Little did I know that our research here
would provide another clue -
2:28 - 2:30to that origin-of-life puzzle.
-
2:31 - 2:33It was on my first field trip here,
-
2:33 - 2:37toward the end of a full,
long week mapping project, -
2:37 - 2:40that I came across something
rather special. -
2:41 - 2:45Now, what probably looks like
a bunch of wrinkly old rocks -
2:45 - 2:47are actually stromatolites.
-
2:47 - 2:51And at the center of this mound
was a small, peculiar rock -
2:51 - 2:54about the size of a child's hand.
-
2:54 - 2:59It took six months before we inspected
this rock under a microscope, -
2:59 - 3:02when one of my mentors
at the time, Malcolm Walter, -
3:02 - 3:06suggested the rock resembled geyserite.
-
3:06 - 3:10Geyserite is a rock type that only forms
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3:10 - 3:14in and around the edges
of hot spring pools. -
3:14 - 3:18Now, in order for you to understand
the significance of geyserite, -
3:18 - 3:22I need to take you back
a couple of centuries. -
3:23 - 3:28In 1871, in a letter
to his friend Joseph Hooker, -
3:28 - 3:29Charles Darwin suggested:
-
3:30 - 3:34"What if life started
in some warm little pond -
3:34 - 3:36with all sort of chemicals
-
3:36 - 3:40still ready to undergo
more complex changes?" -
3:41 - 3:44Well, we know of warm little ponds.
We call them "hot springs." -
3:44 - 3:46In these environments, you have hot water
-
3:46 - 3:49dissolving minerals
from the underlying rocks. -
3:50 - 3:55This solution mixes with organic compounds
-
3:55 - 3:58and results in a kind of chemical factory,
-
3:58 - 4:04which researchers have shown
can manufacture simple cellular structures -
4:04 - 4:07that are the first steps toward life.
-
4:07 - 4:10But 100 years after Darwin's letter,
-
4:10 - 4:14deep-sea hydrothermal vents, or hot vents,
were discovered in the ocean. -
4:14 - 4:16And these are also chemical factories.
-
4:16 - 4:20This one is located along
the Tonga volcanic arc, -
4:20 - 4:241,100 meters below sea level
in the Pacific Ocean. -
4:26 - 4:29The black smoke that you see billowing
out of these chimneylike structures -
4:29 - 4:31is also mineral-rich fluid,
-
4:31 - 4:34which is being fed off by bacteria.
-
4:35 - 4:37And since the discovery
of these deep-sea vents, -
4:37 - 4:42the favored scenario for an origin of life
has been in the ocean. -
4:42 - 4:44And this is for good reason:
-
4:45 - 4:48deep-sea vents are well-known
in the ancient rock record, -
4:48 - 4:52and it's thought that the early Earth
had a global ocean -
4:52 - 4:54and very little land surface.
-
4:54 - 4:59So the probability that deep-sea vents
were abundant on the very early Earth -
4:59 - 5:02fits well with an origin of life
-
5:02 - 5:03in the ocean.
-
5:04 - 5:05However ...
-
5:07 - 5:11our research in the Pilbara
provides and supports -
5:11 - 5:13an alternative perspective.
-
5:14 - 5:19After three years, finally, we were
able to show that, in fact, -
5:20 - 5:23our little rock was geyserite.
-
5:23 - 5:27So this conclusion suggested
not only did hot springs exist -
5:27 - 5:31in our 3.5 billion-year-old
volcano in the Pilbara, -
5:31 - 5:37but it pushed back evidence for life
living on land in hot springs -
5:37 - 5:40in the geological record of Earth
-
5:40 - 5:44by three billion years.
-
5:45 - 5:48And so, from a geological perspective,
-
5:48 - 5:55Darwin's warm little pond
is a reasonable origin-of-life candidate. -
5:57 - 6:01Of course, it's still debatable
how life began on Earth, -
6:01 - 6:03and it probably always will be.
-
6:03 - 6:06But it is clear that it's flourished;
-
6:06 - 6:07it has diversified,
-
6:07 - 6:10and it has become ever more complex.
-
6:10 - 6:13Eventually, it reached
the age of the human, -
6:13 - 6:17a species that has begun
to question its own existence -
6:17 - 6:20and the existence of life elsewhere:
-
6:21 - 6:24Is there a cosmic community
waiting to connect with us, -
6:24 - 6:26or are we all there is?
-
6:27 - 6:31A clue to this puzzle again
comes from the ancient rock record. -
6:32 - 6:35At about 2.5 billion years ago,
-
6:35 - 6:39there is evidence that bacteria
had begun to produce oxygen, -
6:39 - 6:42kind of like plants do today.
-
6:42 - 6:44Geologists refer to
the period that followed -
6:44 - 6:47as the Great Oxidation Event.
-
6:47 - 6:52It is implied from rocks
called banded iron formations, -
6:52 - 6:57many of which can be observed as
hundreds-of-meter-thick packages of rock -
6:57 - 6:59which are exposed in gorges
-
6:59 - 7:03that carve their way through
the Karijini National Park -
7:03 - 7:05in Western Australia.
-
7:05 - 7:10The arrival of free oxygen allowed
two major changes to occur on our planet. -
7:10 - 7:13First, it allowed complex life to evolve.
-
7:13 - 7:17You see, life needs oxygen
to get big and complex. -
7:18 - 7:21And it produced the ozone layer,
which protects modern life -
7:21 - 7:24from the harmful effects
of the sun's UVB radiation. -
7:25 - 7:30So in an ironic twist, microbial life
made way for complex life, -
7:30 - 7:33and in essence, relinquished
its three-billion-year reign -
7:33 - 7:35over the planet.
-
7:35 - 7:39Today, we humans dig up
fossilized complex life -
7:39 - 7:40and burn it for fuel.
-
7:41 - 7:46This practice pumps vast amounts
of carbon dioxide into the atmosphere, -
7:46 - 7:48and like our microbial predecessors,
-
7:48 - 7:51we have begun to make
substantial changes to our planet. -
7:53 - 7:57And the effects of those
are encompassed by global warming. -
7:59 - 8:04Unfortunately, the ironic twist here
could see the demise of humanity. -
8:04 - 8:08And so maybe the reason
we aren't connecting with life elsewhere, -
8:08 - 8:10intelligent life elsewhere,
-
8:10 - 8:13is that once it evolves,
-
8:13 - 8:15it extinguishes itself quickly.
-
8:16 - 8:18If the rocks could talk,
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8:18 - 8:21I suspect they might say this:
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8:22 - 8:25life on Earth is precious.
-
8:27 - 8:31It is the product of
four or so billion years -
8:31 - 8:36of a delicate and complex co-evolution
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8:36 - 8:38between life and Earth,
-
8:38 - 8:44of which humans only represent
the very last speck of time. -
8:45 - 8:50You can use this information
as a guide or a forecast -- -
8:50 - 8:55or an explanation as to why it seems
so lonely in this part of the galaxy. -
8:57 - 9:00But use it to gain some perspective
-
9:01 - 9:06about the legacy that you
want to leave behind -
9:06 - 9:11on the planet that you call home.
-
9:12 - 9:13Thank you.
-
9:13 - 9:17(Applause)
- Title:
- This ancient rock is changing our theory on the origin of life
- Speaker:
- Tara Djokic
- Description:
-
Exactly when and where did life on Earth begin? Scientists have long thought that it emerged three billion years ago in the ocean -- until astrobiologist Tara Djokic and her team made an unexpected discovery in the Western Australian desert. Learn how an ancient rock found near a hot volcanic pool is shifting our understanding of the origin-of-life puzzle.
- Video Language:
- English
- Team:
- closed TED
- Project:
- TEDTalks
- Duration:
- 09:30
Camille Martínez commented on English subtitles for This ancient rock is changing our theory on the origin of life | ||
Camille Martínez edited English subtitles for This ancient rock is changing our theory on the origin of life | ||
Oliver Friedman edited English subtitles for This ancient rock is changing our theory on the origin of life | ||
Oliver Friedman edited English subtitles for This ancient rock is changing our theory on the origin of life | ||
Oliver Friedman edited English subtitles for This ancient rock is changing our theory on the origin of life | ||
Brian Greene approved English subtitles for This ancient rock is changing our theory on the origin of life | ||
Brian Greene edited English subtitles for This ancient rock is changing our theory on the origin of life | ||
Camille Martínez accepted English subtitles for This ancient rock is changing our theory on the origin of life |
Camille Martínez
The English transcript was updated on 12/11/19.
In the talk description:
western Australian --> Western Australian
Thank you!