[Script Info]
Title: 
[Events]
Format: Layer, Start, End, Style, Name, MarginL, MarginR, MarginV, Effect, Text
Dialogue: 0,0:00:01.12,0:00:05.87,Default,,0000,0000,0000,,The Earth is 4.6 billion years old,
Dialogue: 0,0:00:05.90,0:00:10.60,Default,,0000,0000,0000,,but a human lifetime often lasts\Nfor less than 100 years.
Dialogue: 0,0:00:11.19,0:00:14.51,Default,,0000,0000,0000,,So why care about\Nthe history of our planet
Dialogue: 0,0:00:14.53,0:00:20.39,Default,,0000,0000,0000,,when the distant past seems\Nso inconsequential to everyday life?
Dialogue: 0,0:00:20.85,0:00:22.97,Default,,0000,0000,0000,,You see, as far as we can tell,
Dialogue: 0,0:00:22.99,0:00:26.23,Default,,0000,0000,0000,,Earth is the only planet\Nin our solar system
Dialogue: 0,0:00:26.25,0:00:28.76,Default,,0000,0000,0000,,known to have sparked life,
Dialogue: 0,0:00:28.78,0:00:34.18,Default,,0000,0000,0000,,and the only system able to provide\Nlife support for human beings.
Dialogue: 0,0:00:34.76,0:00:36.02,Default,,0000,0000,0000,,So why Earth?
Dialogue: 0,0:00:36.73,0:00:40.11,Default,,0000,0000,0000,,We know Earth is unique\Nfor having plate tectonics,
Dialogue: 0,0:00:40.13,0:00:41.69,Default,,0000,0000,0000,,liquid water on its surface
Dialogue: 0,0:00:41.71,0:00:43.99,Default,,0000,0000,0000,,and an oxygen-rich atmosphere.
Dialogue: 0,0:00:44.46,0:00:46.78,Default,,0000,0000,0000,,But this has not always been the case,
Dialogue: 0,0:00:46.80,0:00:51.64,Default,,0000,0000,0000,,and we know this because ancient rocks\Nhave recorded the pivotal moments
Dialogue: 0,0:00:51.66,0:00:54.47,Default,,0000,0000,0000,,in Earth's planetary evolution.
Dialogue: 0,0:00:55.65,0:00:58.64,Default,,0000,0000,0000,,And one of the best places\Nto observe those ancient rocks
Dialogue: 0,0:00:58.66,0:01:02.13,Default,,0000,0000,0000,,is in the Pilbara of Western Australia.
Dialogue: 0,0:01:03.49,0:01:07.99,Default,,0000,0000,0000,,The rocks here are 3.5 billion years old,
Dialogue: 0,0:01:08.02,0:01:12.62,Default,,0000,0000,0000,,and they contain some of the oldest\Nevidence for life on the planet.
Dialogue: 0,0:01:13.30,0:01:15.71,Default,,0000,0000,0000,,Now, often when we think of early life,
Dialogue: 0,0:01:15.74,0:01:18.96,Default,,0000,0000,0000,,we might imagine a stegosaurus
Dialogue: 0,0:01:18.98,0:01:22.41,Default,,0000,0000,0000,,or maybe a fish crawling onto land.
Dialogue: 0,0:01:23.01,0:01:25.24,Default,,0000,0000,0000,,But the early life that I'm talking about
Dialogue: 0,0:01:25.26,0:01:29.19,Default,,0000,0000,0000,,is simple microscopic life, like bacteria.
Dialogue: 0,0:01:29.74,0:01:33.73,Default,,0000,0000,0000,,And their fossils are often preserved\Nas layered rock structures,
Dialogue: 0,0:01:33.75,0:01:35.89,Default,,0000,0000,0000,,called stromatolites.
Dialogue: 0,0:01:36.52,0:01:41.48,Default,,0000,0000,0000,,This simple form of life\Nis almost all we see in the fossil record
Dialogue: 0,0:01:41.51,0:01:45.64,Default,,0000,0000,0000,,for the first three billion years\Nof life on Earth.
Dialogue: 0,0:01:46.26,0:01:49.71,Default,,0000,0000,0000,,Our species can only be traced\Nback in the fossil record
Dialogue: 0,0:01:49.74,0:01:52.24,Default,,0000,0000,0000,,to a few hundred thousand years ago.
Dialogue: 0,0:01:52.27,0:01:54.23,Default,,0000,0000,0000,,We know from the fossil record,
Dialogue: 0,0:01:54.26,0:01:58.31,Default,,0000,0000,0000,,bacteria life had grabbed\Na strong foothold
Dialogue: 0,0:01:58.33,0:02:01.71,Default,,0000,0000,0000,,by about 3.5 to four billion years ago.
Dialogue: 0,0:02:02.32,0:02:05.96,Default,,0000,0000,0000,,The rocks older than this\Nhave been either destroyed
Dialogue: 0,0:02:05.98,0:02:09.11,Default,,0000,0000,0000,,or highly deformed\Nthrough plate tectonics.
Dialogue: 0,0:02:09.55,0:02:11.99,Default,,0000,0000,0000,,So what remains a missing\Npiece of the puzzle
Dialogue: 0,0:02:12.01,0:02:16.98,Default,,0000,0000,0000,,is exactly when and how\Nlife on Earth began.
Dialogue: 0,0:02:19.09,0:02:22.66,Default,,0000,0000,0000,,Here again is that ancient\Nvolcanic landscape in the Pilbara.
Dialogue: 0,0:02:23.08,0:02:27.90,Default,,0000,0000,0000,,Little did I know that our research here\Nwould provide another clue
Dialogue: 0,0:02:27.93,0:02:30.29,Default,,0000,0000,0000,,to that origin-of-life puzzle.
Dialogue: 0,0:02:30.87,0:02:32.98,Default,,0000,0000,0000,,It was on my first field trip here,
Dialogue: 0,0:02:33.00,0:02:37.15,Default,,0000,0000,0000,,toward the end of a full,\Nlong week mapping project,
Dialogue: 0,0:02:37.17,0:02:40.16,Default,,0000,0000,0000,,that I came across something\Nrather special.
Dialogue: 0,0:02:41.03,0:02:44.63,Default,,0000,0000,0000,,Now, what probably looks like\Na bunch of wrinkly old rocks
Dialogue: 0,0:02:44.66,0:02:46.67,Default,,0000,0000,0000,,are actually stromatolites.
Dialogue: 0,0:02:46.69,0:02:50.82,Default,,0000,0000,0000,,And at the center of this mound\Nwas a small, peculiar rock
Dialogue: 0,0:02:50.84,0:02:53.52,Default,,0000,0000,0000,,about the size of a child's hand.
Dialogue: 0,0:02:54.14,0:02:59.04,Default,,0000,0000,0000,,It took six months before we inspected\Nthis rock under a microscope,
Dialogue: 0,0:02:59.07,0:03:01.68,Default,,0000,0000,0000,,when one of my mentors\Nat the time, Malcolm Walter,
Dialogue: 0,0:03:01.71,0:03:05.57,Default,,0000,0000,0000,,suggested the rock resembled geyserite.
Dialogue: 0,0:03:06.03,0:03:09.54,Default,,0000,0000,0000,,Geyserite is a rock type that only forms
Dialogue: 0,0:03:09.57,0:03:13.69,Default,,0000,0000,0000,,in and around the edges\Nof hot spring pools.
Dialogue: 0,0:03:14.16,0:03:17.65,Default,,0000,0000,0000,,Now, in order for you to understand\Nthe significance of geyserite,
Dialogue: 0,0:03:17.67,0:03:21.82,Default,,0000,0000,0000,,I need to take you back\Na couple of centuries.
Dialogue: 0,0:03:23.46,0:03:27.52,Default,,0000,0000,0000,,In 1871, in a letter\Nto his friend Joseph Hooker,
Dialogue: 0,0:03:27.54,0:03:29.35,Default,,0000,0000,0000,,Charles Darwin suggested:
Dialogue: 0,0:03:30.18,0:03:33.90,Default,,0000,0000,0000,,"What if life started\Nin some warm little pond
Dialogue: 0,0:03:33.93,0:03:36.05,Default,,0000,0000,0000,,with all sort of chemicals
Dialogue: 0,0:03:36.07,0:03:40.34,Default,,0000,0000,0000,,still ready to undergo\Nmore complex changes?"
Dialogue: 0,0:03:40.88,0:03:43.97,Default,,0000,0000,0000,,Well, we know of warm little ponds.\NWe call them "hot springs."
Dialogue: 0,0:03:43.99,0:03:46.32,Default,,0000,0000,0000,,In these environments, you have hot water
Dialogue: 0,0:03:46.34,0:03:49.36,Default,,0000,0000,0000,,dissolving minerals\Nfrom the underlying rocks.
Dialogue: 0,0:03:50.30,0:03:55.35,Default,,0000,0000,0000,,This solution mixes with organic compounds
Dialogue: 0,0:03:55.38,0:03:58.01,Default,,0000,0000,0000,,and results in a kind of chemical factory,
Dialogue: 0,0:03:58.03,0:04:04.02,Default,,0000,0000,0000,,which researchers have shown\Ncan manufacture simple cellular structures
Dialogue: 0,0:04:04.05,0:04:07.34,Default,,0000,0000,0000,,that are the first steps toward life.
Dialogue: 0,0:04:07.36,0:04:09.62,Default,,0000,0000,0000,,But 100 years after Darwin's letter,
Dialogue: 0,0:04:09.64,0:04:13.82,Default,,0000,0000,0000,,deep-sea hydrothermal vents, or hot vents,\Nwere discovered in the ocean.
Dialogue: 0,0:04:13.84,0:04:16.15,Default,,0000,0000,0000,,And these are also chemical factories.
Dialogue: 0,0:04:16.18,0:04:19.73,Default,,0000,0000,0000,,This one is located along\Nthe Tonga volcanic arc,
Dialogue: 0,0:04:19.75,0:04:24.25,Default,,0000,0000,0000,,1,100 meters below sea level\Nin the Pacific Ocean.
Dialogue: 0,0:04:25.56,0:04:29.26,Default,,0000,0000,0000,,The black smoke that you see billowing\Nout of these chimneylike structures
Dialogue: 0,0:04:29.28,0:04:31.10,Default,,0000,0000,0000,,is also mineral-rich fluid,
Dialogue: 0,0:04:31.12,0:04:34.02,Default,,0000,0000,0000,,which is being fed off by bacteria.
Dialogue: 0,0:04:34.97,0:04:37.24,Default,,0000,0000,0000,,And since the discovery\Nof these deep-sea vents,
Dialogue: 0,0:04:37.26,0:04:41.52,Default,,0000,0000,0000,,the favored scenario for an origin of life\Nhas been in the ocean.
Dialogue: 0,0:04:42.09,0:04:43.67,Default,,0000,0000,0000,,And this is for good reason:
Dialogue: 0,0:04:45.12,0:04:48.43,Default,,0000,0000,0000,,deep-sea vents are well-known\Nin the ancient rock record,
Dialogue: 0,0:04:48.45,0:04:51.52,Default,,0000,0000,0000,,and it's thought that the early Earth\Nhad a global ocean
Dialogue: 0,0:04:51.54,0:04:54.29,Default,,0000,0000,0000,,and very little land surface.
Dialogue: 0,0:04:54.32,0:04:59.02,Default,,0000,0000,0000,,So the probability that deep-sea vents\Nwere abundant on the very early Earth
Dialogue: 0,0:04:59.04,0:05:01.52,Default,,0000,0000,0000,,fits well with an origin of life
Dialogue: 0,0:05:01.55,0:05:02.83,Default,,0000,0000,0000,,in the ocean.
Dialogue: 0,0:05:04.23,0:05:05.38,Default,,0000,0000,0000,,However ...
Dialogue: 0,0:05:06.50,0:05:10.66,Default,,0000,0000,0000,,our research in the Pilbara\Nprovides and supports
Dialogue: 0,0:05:10.68,0:05:12.94,Default,,0000,0000,0000,,an alternative perspective.
Dialogue: 0,0:05:13.59,0:05:19.49,Default,,0000,0000,0000,,After three years, finally, we were\Nable to show that, in fact,
Dialogue: 0,0:05:19.51,0:05:22.89,Default,,0000,0000,0000,,our little rock was geyserite.
Dialogue: 0,0:05:22.92,0:05:26.98,Default,,0000,0000,0000,,So this conclusion suggested\Nnot only did hot springs exist
Dialogue: 0,0:05:27.01,0:05:31.06,Default,,0000,0000,0000,,in our 3.5 billion-year-old\Nvolcano in the Pilbara,
Dialogue: 0,0:05:31.09,0:05:37.45,Default,,0000,0000,0000,,but it pushed back evidence for life\Nliving on land in hot springs
Dialogue: 0,0:05:37.47,0:05:39.71,Default,,0000,0000,0000,,in the geological record of Earth
Dialogue: 0,0:05:39.73,0:05:43.64,Default,,0000,0000,0000,,by three billion years.
Dialogue: 0,0:05:44.82,0:05:48.24,Default,,0000,0000,0000,,And so, from a geological perspective,
Dialogue: 0,0:05:48.27,0:05:55.12,Default,,0000,0000,0000,,Darwin's warm little pond\Nis a reasonable origin-of-life candidate.
Dialogue: 0,0:05:57.17,0:06:00.74,Default,,0000,0000,0000,,Of course, it's still debatable\Nhow life began on Earth,
Dialogue: 0,0:06:00.76,0:06:03.22,Default,,0000,0000,0000,,and it probably always will be.
Dialogue: 0,0:06:03.25,0:06:05.80,Default,,0000,0000,0000,,But it is clear that it's flourished;
Dialogue: 0,0:06:05.83,0:06:07.19,Default,,0000,0000,0000,,it has diversified,
Dialogue: 0,0:06:07.21,0:06:09.74,Default,,0000,0000,0000,,and it has become ever more complex.
Dialogue: 0,0:06:09.76,0:06:13.08,Default,,0000,0000,0000,,Eventually, it reached\Nthe age of the human,
Dialogue: 0,0:06:13.11,0:06:16.73,Default,,0000,0000,0000,,a species that has begun\Nto question its own existence
Dialogue: 0,0:06:16.76,0:06:19.62,Default,,0000,0000,0000,,and the existence of life elsewhere:
Dialogue: 0,0:06:20.60,0:06:23.73,Default,,0000,0000,0000,,Is there a cosmic community\Nwaiting to connect with us,
Dialogue: 0,0:06:23.76,0:06:26.16,Default,,0000,0000,0000,,or are we all there is?
Dialogue: 0,0:06:26.88,0:06:31.36,Default,,0000,0000,0000,,A clue to this puzzle again\Ncomes from the ancient rock record.
Dialogue: 0,0:06:32.32,0:06:34.58,Default,,0000,0000,0000,,At about 2.5 billion years ago,
Dialogue: 0,0:06:34.60,0:06:39.45,Default,,0000,0000,0000,,there is evidence that bacteria\Nhad begun to produce oxygen,
Dialogue: 0,0:06:39.47,0:06:41.74,Default,,0000,0000,0000,,kind of like plants do today.
Dialogue: 0,0:06:41.76,0:06:44.24,Default,,0000,0000,0000,,Geologists refer to\Nthe period that followed
Dialogue: 0,0:06:44.26,0:06:46.92,Default,,0000,0000,0000,,as the Great Oxidation Event.
Dialogue: 0,0:06:47.44,0:06:52.09,Default,,0000,0000,0000,,It is implied from rocks\Ncalled banded iron formations,
Dialogue: 0,0:06:52.12,0:06:57.26,Default,,0000,0000,0000,,many of which can be observed as\Nhundreds-of-meter-thick packages of rock
Dialogue: 0,0:06:57.28,0:06:59.44,Default,,0000,0000,0000,,which are exposed in gorges
Dialogue: 0,0:06:59.47,0:07:02.84,Default,,0000,0000,0000,,that carve their way through\Nthe Karijini National Park
Dialogue: 0,0:07:02.86,0:07:04.62,Default,,0000,0000,0000,,in Western Australia.
Dialogue: 0,0:07:05.16,0:07:09.53,Default,,0000,0000,0000,,The arrival of free oxygen allowed\Ntwo major changes to occur on our planet.
Dialogue: 0,0:07:09.55,0:07:13.04,Default,,0000,0000,0000,,First, it allowed complex life to evolve.
Dialogue: 0,0:07:13.06,0:07:17.02,Default,,0000,0000,0000,,You see, life needs oxygen\Nto get big and complex.
Dialogue: 0,0:07:17.73,0:07:20.74,Default,,0000,0000,0000,,And it produced the ozone layer,\Nwhich protects modern life
Dialogue: 0,0:07:20.77,0:07:24.34,Default,,0000,0000,0000,,from the harmful effects\Nof the sun's UVB radiation.
Dialogue: 0,0:07:24.84,0:07:29.80,Default,,0000,0000,0000,,So in an ironic twist, microbial life\Nmade way for complex life,
Dialogue: 0,0:07:29.82,0:07:33.46,Default,,0000,0000,0000,,and in essence, relinquished\Nits three-billion-year reign
Dialogue: 0,0:07:33.48,0:07:34.65,Default,,0000,0000,0000,,over the planet.
Dialogue: 0,0:07:35.16,0:07:38.76,Default,,0000,0000,0000,,Today, we humans dig up\Nfossilized complex life
Dialogue: 0,0:07:38.78,0:07:40.24,Default,,0000,0000,0000,,and burn it for fuel.
Dialogue: 0,0:07:41.15,0:07:45.54,Default,,0000,0000,0000,,This practice pumps vast amounts\Nof carbon dioxide into the atmosphere,
Dialogue: 0,0:07:45.57,0:07:48.02,Default,,0000,0000,0000,,and like our microbial predecessors,
Dialogue: 0,0:07:48.04,0:07:51.48,Default,,0000,0000,0000,,we have begun to make\Nsubstantial changes to our planet.
Dialogue: 0,0:07:52.89,0:07:56.56,Default,,0000,0000,0000,,And the effects of those\Nare encompassed by global warming.
Dialogue: 0,0:07:58.79,0:08:03.97,Default,,0000,0000,0000,,Unfortunately, the ironic twist here\Ncould see the demise of humanity.
Dialogue: 0,0:08:04.42,0:08:08.38,Default,,0000,0000,0000,,And so maybe the reason\Nwe aren't connecting with life elsewhere,
Dialogue: 0,0:08:08.40,0:08:10.44,Default,,0000,0000,0000,,intelligent life elsewhere,
Dialogue: 0,0:08:10.46,0:08:12.54,Default,,0000,0000,0000,,is that once it evolves,
Dialogue: 0,0:08:12.57,0:08:15.31,Default,,0000,0000,0000,,it extinguishes itself quickly.
Dialogue: 0,0:08:16.15,0:08:18.05,Default,,0000,0000,0000,,If the rocks could talk,
Dialogue: 0,0:08:18.08,0:08:21.10,Default,,0000,0000,0000,,I suspect they might say this:
Dialogue: 0,0:08:22.34,0:08:25.19,Default,,0000,0000,0000,,life on Earth is precious.
Dialogue: 0,0:08:26.70,0:08:31.08,Default,,0000,0000,0000,,It is the product of\Nfour or so billion years
Dialogue: 0,0:08:31.11,0:08:35.81,Default,,0000,0000,0000,,of a delicate and complex co-evolution
Dialogue: 0,0:08:35.84,0:08:38.35,Default,,0000,0000,0000,,between life and Earth,
Dialogue: 0,0:08:38.37,0:08:43.66,Default,,0000,0000,0000,,of which humans only represent\Nthe very last speck of time.
Dialogue: 0,0:08:45.47,0:08:49.74,Default,,0000,0000,0000,,You can use this information\Nas a guide or a forecast --
Dialogue: 0,0:08:49.76,0:08:54.96,Default,,0000,0000,0000,,or an explanation as to why it seems\Nso lonely in this part of the galaxy.
Dialogue: 0,0:08:56.63,0:09:00.32,Default,,0000,0000,0000,,But use it to gain some perspective
Dialogue: 0,0:09:01.17,0:09:05.92,Default,,0000,0000,0000,,about the legacy that you\Nwant to leave behind
Dialogue: 0,0:09:05.94,0:09:10.59,Default,,0000,0000,0000,,on the planet that you call home.
Dialogue: 0,0:09:12.08,0:09:13.33,Default,,0000,0000,0000,,Thank you.
Dialogue: 0,0:09:13.36,0:09:16.90,Default,,0000,0000,0000,,(Applause)