WEBVTT 00:02.133 --> 00:04.166 align:left position:40% line:5% size:50% NARRATOR: A young world. 00:05.633 --> 00:08.633 align:left position:25% line:5% size:65% The atmosphere toxic. 00:08.633 --> 00:13.333 align:left position:12.5% line:5% size:77.5% The land barren and forbidding. 00:14.600 --> 00:19.366 align:left position:10% line:83% size:80% Until the arrival of a life form that changed everything. 00:21.333 --> 00:22.366 align:left position:42.5% line:89% size:47.5% Plants. 00:24.266 --> 00:25.700 align:left position:32.5% line:83% size:57.5% DORI CONTRERAS: Everything about the landscape 00:25.700 --> 00:30.466 align:left position:20% line:83% size:70% was influenced by plants moving onto the land. 00:30.466 --> 00:32.600 align:left position:40% line:83% size:50% NARRATOR: Evolving in the oceans, 00:32.600 --> 00:35.033 align:left position:22.5% line:83% size:67.5% they eventually partner with fungi 00:35.033 --> 00:37.500 align:left position:20% line:89% size:70% to turn an alien world... 00:37.500 --> 00:40.666 align:left position:22.5% line:83% size:67.5% One of the most bizarre prehistoric landscapes of all. 00:40.666 --> 00:44.500 align:left position:40% line:83% size:50% NARRATOR: ...into one we recognize today. 00:44.500 --> 00:46.166 align:left position:30% line:89% size:60% (eruption roars) 00:46.166 --> 00:49.466 align:left position:10% line:83% size:80% Along the way, they're subjected to cataclysm after cataclysm... 00:51.433 --> 00:55.500 align:left position:32.5% line:77% size:57.5% LYNN SOREGHAN: Ice could have covered the entire planet. 00:57.133 --> 01:00.133 align:left position:40% line:77% size:50% NARRATOR: ...and alter the very Earth itself. 01:00.133 --> 01:02.233 align:left position:25% line:83% size:65% CHRISTOPHER JACKSON: This interplay between biology 01:02.233 --> 01:05.233 align:left position:22.5% line:83% size:67.5% and geology has utterly transformed our land. 01:05.233 --> 01:09.000 align:left position:40% line:77% size:50% NARRATOR: How did an inhospitable rocky planet... 01:10.433 --> 01:13.333 align:left position:15% line:89% size:75% ...become an oasis for life? 01:13.333 --> 01:16.700 align:left position:15% line:89% size:75% "Ancient Earth: Life Rising." 01:17.900 --> 01:20.733 align:left position:25% line:89% size:65% Right now, on "NOVA." 01:21.966 --> 01:26.866 align:left position:47.5% line:89% size:42.5% ♪ ♪ 01:44.533 --> 01:48.100 align:left position:47.5% line:89% size:42.5% ♪ ♪ 01:49.166 --> 01:55.200 align:left position:40% line:77% size:50% NARRATOR: Viewed from above, planet Earth is a riot of colors. 02:00.966 --> 02:04.466 align:left position:22.5% line:83% size:67.5% But there is one color that is special. 02:06.400 --> 02:11.166 align:left position:12.5% line:83% size:77.5% One that reminds us our home is a living, breathing planet, 02:11.166 --> 02:14.366 align:left position:17.5% line:89% size:72.5% unique in our solar system. 02:14.366 --> 02:20.366 align:left position:47.5% line:89% size:42.5% ♪ ♪ 02:20.366 --> 02:22.400 align:left position:42.5% line:89% size:47.5% Green. 02:25.900 --> 02:30.433 align:left position:32.5% line:89% size:57.5% (wind howling) 02:31.900 --> 02:35.233 align:left position:30% line:83% size:60% This is the story of how Earth transformed... 02:35.233 --> 02:40.133 align:left position:47.5% line:89% size:42.5% ♪ ♪ 02:40.133 --> 02:44.966 align:left position:30% line:83% size:60% ...from a hostile and inhospitable world... 02:45.966 --> 02:49.833 align:left position:12.5% line:83% size:77.5% ...into a haven of opportunity for life. 02:51.400 --> 02:53.100 align:left position:30% line:83% size:60% Our green planet wasn't preordained. 02:53.100 --> 02:56.433 align:left position:15% line:83% size:75% It's the result of an immense struggle over millions of years. 02:59.666 --> 03:02.400 align:left position:40% line:77% size:50% NARRATOR: How plant life rose from the oceans 03:02.400 --> 03:07.433 align:left position:25% line:83% size:65% to dominate a rugged and desolate landscape. 03:07.433 --> 03:10.066 align:left position:30% line:77% size:60% ALY BAUMGARTNER: Everything that you know about the planet, 03:10.066 --> 03:12.233 align:left position:20% line:83% size:70% everything that you think of when you look outside, 03:12.233 --> 03:14.933 align:left position:25% line:89% size:65% is because of plants. 03:16.266 --> 03:19.466 align:left position:40% line:77% size:50% NARRATOR: And how plants reshaped Earth itself. 03:19.466 --> 03:21.333 align:left position:37.5% line:83% size:52.5% CONTRERAS: Without plants, 03:21.333 --> 03:24.200 align:left position:17.5% line:83% size:72.5% Earth would be nothing like it is today. 03:24.200 --> 03:26.366 align:left position:40% line:77% size:50% JACKSON: Plants are literal terra-formers. 03:26.366 --> 03:29.466 align:left position:17.5% line:83% size:72.5% They transformed bare rock into life-giving soil. 03:29.466 --> 03:31.466 align:left position:47.5% line:89% size:42.5% ♪ ♪ 03:31.466 --> 03:35.433 align:left position:35% line:77% size:55% KIRK JOHNSON: Plants are elaborate, beautiful little machines. 03:35.433 --> 03:37.833 align:left position:27.5% line:83% size:62.5% These are the most amazing things in the world. 03:44.100 --> 03:45.666 align:left position:25% line:5% size:65% ("Never Close Enough" by SIPHO. playing) 03:45.666 --> 03:49.033 align:left position:20% line:83% size:70% ♪ Oh, we won't ever hear the silence ♪ 03:49.033 --> 03:52.066 align:left position:17.5% line:89% size:72.5% ♪ Or ever see the colors ♪ 03:52.066 --> 03:53.366 align:left position:37.5% line:89% size:52.5% (exploding) 03:53.366 --> 03:55.700 align:left position:25% line:83% size:65% ♪ That never lived in our minds ♪ 03:55.700 --> 04:00.100 align:left position:47.5% line:89% size:42.5% ♪ ♪ 04:00.100 --> 04:02.166 align:left position:30% line:89% size:60% ♪ Just a moment ♪ 04:02.166 --> 04:04.733 align:left position:25% line:89% size:65% ♪ Never too far out ♪ 04:04.733 --> 04:06.933 align:left position:22.5% line:89% size:67.5% ♪ Never close enough ♪ 04:15.633 --> 04:20.666 align:left position:47.5% line:5% size:42.5% ♪ ♪ 04:34.466 --> 04:39.200 align:left position:40% line:5% size:50% NARRATOR: Half a billion years after Earth was formed... 04:41.166 --> 04:44.700 align:left position:30% line:5% size:60% ...the planet is covered by an endless ocean... 04:47.466 --> 04:52.233 align:left position:17.5% line:5% size:72.5% ...broken up only by a few remote volcanic islands, 04:52.233 --> 04:56.100 align:left position:25% line:5% size:65% with no trace of life on the surface. 04:58.800 --> 05:02.433 align:left position:17.5% line:5% size:72.5% But this is a living world. 05:07.433 --> 05:11.600 align:left position:17.5% line:5% size:72.5% To find ancestors of modern life, many scientists believe 05:11.600 --> 05:14.266 align:left position:22.5% line:83% size:67.5% you would have to leave the surface behind... 05:14.266 --> 05:18.733 align:left position:47.5% line:89% size:42.5% ♪ ♪ 05:18.733 --> 05:22.000 align:left position:35% line:83% size:55% ...and travel to the depths of the oceans. 05:27.466 --> 05:32.766 align:left position:12.5% line:83% size:77.5% It's thought early life thrived in superheated geothermal vents. 05:37.766 --> 05:41.466 align:left position:47.5% line:89% size:42.5% ♪ ♪ 05:41.466 --> 05:44.333 align:left position:15% line:83% size:75% These single-celled organisms would've been 05:44.333 --> 05:49.200 align:left position:20% line:83% size:70% uniquely adapted to life in this harsh environment, 05:49.200 --> 05:51.933 align:left position:12.5% line:83% size:77.5% and would ultimately give rise to plants 05:51.933 --> 05:56.333 align:left position:32.5% line:83% size:57.5% and everything that will ever live on Earth. 05:56.333 --> 06:01.133 align:left position:47.5% line:89% size:42.5% ♪ ♪ 06:01.133 --> 06:05.366 align:left position:35% line:83% size:55% But for now, they're stuck in the ocean, 06:05.366 --> 06:07.900 align:left position:17.5% line:89% size:72.5% because large landmasses... 06:07.900 --> 06:09.900 align:left position:27.5% line:83% size:62.5% (eruption roaring, water hissing) 06:09.900 --> 06:12.066 align:left position:25% line:89% size:65% ...do not yet exist. 06:17.266 --> 06:19.366 align:left position:17.5% line:71% size:72.5% So there's a theory that four billion years ago, 06:19.366 --> 06:21.166 align:left position:10% line:71% size:80% the only land on Earth were just 06:21.166 --> 06:23.066 align:left position:15% line:71% size:75% a few black volcanic islands 06:23.066 --> 06:26.366 align:left position:22.5% line:71% size:67.5% scattered in the ocean. 06:26.366 --> 06:28.433 align:left position:47.5% line:89% size:42.5% ♪ ♪ 06:28.433 --> 06:29.766 align:left position:30% line:5% size:60% This early land was made of basalt, 06:29.766 --> 06:31.466 align:left position:25% line:5% size:65% which is cooled lava. 06:31.466 --> 06:34.366 align:left position:17.5% line:5% size:72.5% And it contains magnesium, calcium-- 06:34.366 --> 06:36.066 align:left position:17.5% line:5% size:72.5% things that life requires. 06:38.700 --> 06:40.800 align:left position:35% line:77% size:55% AISHA MORRIS: The problem was that these small early 06:40.800 --> 06:42.366 align:left position:37.5% line:71% size:52.5% volcanic islands were short-lived, 06:42.366 --> 06:45.600 align:left position:20% line:71% size:70% because they were smashed to pieces by the tides 06:45.600 --> 06:48.066 align:left position:20% line:71% size:70%   created by the much closer moon at that time. 06:52.033 --> 06:53.833 align:left position:40% line:77% size:50% NARRATOR: For dry land to form and persist, 06:53.833 --> 06:57.833 align:left position:27.5% line:83% size:62.5% one of the world's most powerful geologic forces 06:57.833 --> 07:01.100 align:left position:35% line:89% size:55% had to begin: 07:01.100 --> 07:04.100 align:left position:30% line:89% size:60% plate tectonics. 07:04.100 --> 07:06.633 align:left position:30% line:89% size:60% (eruption roars) 07:08.600 --> 07:11.166 align:left position:42.5% line:77% size:47.5% MORRIS: Plate tectonics really tries to explain 07:11.166 --> 07:13.666 align:left position:17.5% line:83% size:72.5% the land forms that we see on Earth: 07:13.666 --> 07:16.066 align:left position:22.5% line:83% size:67.5% things like volcanoes, events such as earthquakes. 07:18.233 --> 07:20.833 align:left position:25% line:83% size:65% And it's really based on the idea that plates 07:20.833 --> 07:23.233 align:left position:17.5% line:83% size:72.5% on the surface of the Earth move around in relation 07:23.233 --> 07:26.133 align:left position:15% line:83% size:75% to one another, and sometimes go beneath each other, 07:26.133 --> 07:27.800 align:left position:10% line:89% size:80% sometimes crash into each other, 07:27.800 --> 07:30.066 align:left position:20% line:83% size:70% and sometimes slide past each other. 07:32.200 --> 07:34.000 align:left position:40% line:77% size:50% NARRATOR: This geologic process would prove 07:34.000 --> 07:39.500 align:left position:12.5% line:83% size:77.5% to be the key that would change the surface forever. 07:39.500 --> 07:42.466 align:left position:47.5% line:89% size:42.5% ♪ ♪ 07:42.466 --> 07:45.700 align:left position:27.5% line:83% size:62.5% But its beginnings are shrouded in mystery. 07:48.166 --> 07:51.333 align:left position:42.5% line:77% size:47.5% HAZEN: The beginnings of plate tectonics is so controversial. 07:52.366 --> 07:53.933 align:left position:20% line:89% size:70% Some people think it was 07:53.933 --> 07:56.766 align:left position:15% line:83% size:75% density differences and crust being pulled down by gravity. 07:59.433 --> 08:05.433 align:left position:40% line:5% size:50% NARRATOR: But some incredible new evidence has been discovered 08:05.433 --> 08:10.733 align:left position:35% line:83% size:55% that suggests an extra-terrestrial origin. 08:10.733 --> 08:13.133 align:left position:17.5% line:83% size:72.5% Sometimes geology gives us great clues 08:13.133 --> 08:15.766 align:left position:20% line:83% size:70% about how early processes occurred. 08:18.000 --> 08:20.566 align:left position:40% line:77% size:50% NARRATOR: Scientists have found microscopic structures 08:20.566 --> 08:24.333 align:left position:30% line:83% size:60% called spherules, thought to be formed 08:24.333 --> 08:26.400 align:left position:27.5% line:89% size:62.5% by asteroid impacts 08:26.400 --> 08:31.166 align:left position:22.5% line:83% size:67.5% 3.2 billion years ago, hidden in ancient rocks. 08:32.400 --> 08:34.333 align:left position:30% line:83% size:60% These are located alongside rocks 08:34.333 --> 08:38.433 align:left position:25% line:83% size:65% that show indications of plate tectonics. 08:38.433 --> 08:40.300 align:left position:27.5% line:83% size:62.5% So it's really hard to know for sure, 08:40.300 --> 08:42.266 align:left position:25% line:83% size:65% because this happened so long ago, 08:42.266 --> 08:44.066 align:left position:17.5% line:83% size:72.5% but one of the things that may have happened 08:44.066 --> 08:45.400 align:left position:25% line:89% size:65% is that these impacts 08:45.400 --> 08:47.900 align:left position:30% line:83% size:60% may have actually started the magma moving. 08:50.066 --> 08:52.533 align:left position:22.5% line:83% size:67.5% These asteroid impacts would've ruptured the crust. 08:52.533 --> 08:55.700 align:left position:25% line:83% size:65% They may have played some role in starting the plates 08:55.700 --> 08:58.966 align:left position:17.5% line:83% size:72.5% moving and allowing plates to sink. 08:58.966 --> 09:02.100 align:left position:35% line:83% size:55% This may have started plate tectonics. 09:06.200 --> 09:11.466 align:left position:47.5% line:89% size:42.5% ♪ ♪ 09:16.166 --> 09:19.700 align:left position:40% line:77% size:50% NARRATOR: Data suggest that one of these giant asteroids 09:19.700 --> 09:22.533 align:left position:12.5% line:89% size:77.5% is as much as 30 miles across. 09:22.533 --> 09:27.233 align:left position:47.5% line:89% size:42.5% ♪ ♪ 09:29.333 --> 09:31.900 align:left position:12.5% line:83% size:77.5% More than three times the size of the one 09:31.900 --> 09:35.200 align:left position:30% line:83% size:60% believed to have wiped out the dinosaurs. 09:35.200 --> 09:42.033 align:left position:47.5% line:89% size:42.5% ♪ ♪ 09:42.033 --> 09:45.500 align:left position:30% line:89% size:60% (explosion roars) 09:48.666 --> 09:53.466 align:left position:15% line:83% size:75% Early life forms in its path would be lost to oblivion. 09:58.133 --> 10:00.033 align:left position:35% line:89% size:55% But somehow, 10:00.033 --> 10:03.533 align:left position:17.5% line:89% size:72.5% in its deep ocean hideaway, 10:03.533 --> 10:07.033 align:left position:17.5% line:89% size:72.5% some early life clings on, 10:07.033 --> 10:13.566 align:left position:12.5% line:83% size:77.5% and its odds for making it onto land have just gotten better. 10:15.033 --> 10:17.433 align:left position:35% line:83% size:55% Because with the advent of plate tectonics 10:17.433 --> 10:19.900 align:left position:30% line:83% size:60% comes an entirely new kind of rock... 10:22.300 --> 10:25.833 align:left position:35% line:83% size:55% ...that could allow life to get a foothold. 10:28.833 --> 10:34.300 align:left position:22.5% line:83% size:67.5% This rock forms during a process called subduction. 10:34.300 --> 10:36.600 align:left position:15% line:71% size:75% Subduction is when one slab of rock, 10:36.600 --> 10:38.500 align:left position:10% line:71% size:80% a tectonic plate, is forced down 10:38.500 --> 10:39.900 align:left position:12.5% line:71% size:77.5% beneath another tectonic plate. 10:43.200 --> 10:44.633 align:left position:40% line:5% size:50% EDMONDS: The subducting plate brings water down 10:44.633 --> 10:46.400 align:left position:30% line:5% size:60% into the interior of the Earth, and that water 10:46.400 --> 10:49.366 align:left position:20% line:83% size:70% is a bit like adding salt to an icy road. 10:49.366 --> 10:53.300 align:left position:17.5% line:83% size:72.5% So adding water to hot rock makes it melt, 10:53.300 --> 10:55.200 align:left position:10% line:89% size:80% but this melt is really special. 10:55.200 --> 10:57.133 align:left position:30% line:83% size:60% It's really rich in silica and oxygen, 10:57.133 --> 10:59.433 align:left position:30% line:83% size:60% and when it rises to the surface, 10:59.433 --> 11:00.766 align:left position:30% line:89% size:60% it forms granite. 11:03.400 --> 11:07.266 align:left position:40% line:77% size:50% NARRATOR: A rock that shapes the surface of Earth as we know it today. 11:09.333 --> 11:12.333 align:left position:15% line:83% size:75% Now, you may think of granite as just a speckled 11:12.333 --> 11:15.566 align:left position:17.5% line:83% size:72.5% gray rock, but it actually has a really special property 11:15.566 --> 11:18.233 align:left position:20% line:83% size:70% that make it a wonderful land-building material. 11:21.100 --> 11:23.100 align:left position:40% line:83% size:50% NARRATOR: Granite has a low density. 11:23.100 --> 11:24.533 align:left position:42.5% line:83% size:47.5% HAZEN: So we all understand density 11:24.533 --> 11:27.000 align:left position:20% line:83% size:70% because we put ice cubes in our drink, 11:27.000 --> 11:29.666 align:left position:32.5% line:83% size:57.5% and when we do, about ten percent of that ice 11:29.666 --> 11:31.400 align:left position:22.5% line:89% size:67.5% sticks above the water, 11:31.400 --> 11:34.066 align:left position:20% line:83% size:70% 'cause ice is ten percent less dense than water. 11:34.066 --> 11:36.200 align:left position:17.5% line:89% size:72.5% And in the exact same way, 11:36.200 --> 11:39.133 align:left position:15% line:83% size:75% granite is about ten percent less dense than basalt, 11:39.133 --> 11:41.233 align:left position:15% line:89% size:75% so ten percent of the granite 11:41.233 --> 11:43.700 align:left position:22.5% line:89% size:67.5% sticks up above basalt. 11:43.700 --> 11:45.933 align:left position:47.5% line:89% size:42.5% ♪ ♪ 11:45.933 --> 11:47.600 align:left position:25% line:83% size:65% This means that after granite's formed, 11:47.600 --> 11:49.200 align:left position:25% line:89% size:65% this hard, heavy rock 11:49.200 --> 11:51.066 align:left position:22.5% line:89% size:67.5% actually floats on top 11:51.066 --> 11:54.100 align:left position:12.5% line:83% size:77.5% of the partially molten basalt beneath it. 11:59.066 --> 12:02.266 align:left position:32.5% line:89% size:57.5% (wind howling) 12:02.266 --> 12:07.333 align:left position:47.5% line:89% size:42.5% ♪ ♪ 12:07.333 --> 12:11.700 align:left position:40% line:77% size:50% NARRATOR: As plate tectonics continue, over billions of years, 12:11.700 --> 12:14.133 align:left position:25% line:89% size:65% vast swathes of rock 12:14.133 --> 12:17.600 align:left position:30% line:83% size:60% gradually emerge across the planet. 12:22.966 --> 12:26.266 align:left position:20% line:83% size:70% Earth's first landmasses are born. 12:45.533 --> 12:47.333 align:left position:20% line:89% size:70% A couple of billion years 12:47.333 --> 12:50.266 align:left position:22.5% line:83% size:67.5% after the inception of plate tectonics... 12:52.133 --> 12:55.333 align:left position:30% line:83% size:60% ...a multitude of continental-scale landmasses 12:55.333 --> 12:58.900 align:left position:30% line:83% size:60% are strewn across the surface of the planet. 13:04.600 --> 13:07.333 align:left position:30% line:89% size:60% A vast frontier. 13:11.233 --> 13:15.266 align:left position:20% line:83% size:70% A rocky world with plenty of minerals 13:15.266 --> 13:19.166 align:left position:20% line:83% size:70% containing nutrients like potassium and phosphorus, 13:19.166 --> 13:22.233 align:left position:22.5% line:89% size:67.5% key elements for life. 13:25.500 --> 13:30.300 align:left position:47.5% line:89% size:42.5% ♪ ♪ 13:32.633 --> 13:36.533 align:left position:12.5% line:83% size:77.5% For any organism that can adapt to this new territory, 13:36.533 --> 13:39.666 align:left position:12.5% line:89% size:77.5% incredible opportunities await. 13:42.200 --> 13:47.233 align:left position:47.5% line:89% size:42.5% ♪ ♪ 13:58.366 --> 14:00.900 align:left position:20% line:89% size:70% Dwelling in the shallows, 14:00.900 --> 14:04.000 align:left position:32.5% line:83% size:57.5% within touching distance of the land... 14:06.633 --> 14:10.100 align:left position:25% line:83% size:65% ...are recognizable, plant-like life. 14:12.166 --> 14:16.133 align:left position:35% line:89% size:55% Marine algae. 14:17.500 --> 14:19.133 align:left position:15% line:89% size:75% Descendants of the early life 14:19.133 --> 14:22.033 align:left position:32.5% line:83% size:57.5% that originated in geothermal vents. 14:25.833 --> 14:29.133 align:left position:35% line:83% size:55% They bask in the light-filled shallows, 14:29.133 --> 14:31.333 align:left position:32.5% line:83% size:57.5% having adopted an absolutely incredible way 14:31.333 --> 14:35.166 align:left position:30% line:83% size:60% to harvest energy directly from the sun: 14:35.166 --> 14:39.066 align:left position:32.5% line:89% size:57.5% photosynthesis. 14:39.066 --> 14:41.233 align:left position:20% line:71% size:70% Photosynthesis is a chemical reaction 14:41.233 --> 14:43.333 align:left position:12.5% line:71% size:77.5% by which plants take light from the sun 14:43.333 --> 14:46.700 align:left position:17.5% line:71% size:72.5% and combine it with water and carbon dioxide 14:46.700 --> 14:50.200 align:left position:17.5% line:5% size:72.5% to make oxygen and glucose, the sugar they use for energy. 14:51.966 --> 14:54.200 align:left position:40% line:5% size:50% NARRATOR: Marine algae have evolved to use 14:54.200 --> 14:59.066 align:left position:27.5% line:5% size:62.5% a crucial cellular innovation called chloroplasts, 14:59.066 --> 15:02.400 align:left position:22.5% line:83% size:67.5% specialized structures filled with chlorophyll, 15:02.400 --> 15:05.800 align:left position:25% line:83% size:65% a compound that helps harness the sun's energy 15:05.800 --> 15:10.500 align:left position:32.5% line:83% size:57.5% and gives them their distinctive green hue. 15:13.666 --> 15:16.500 align:left position:17.5% line:83% size:72.5% But they are still confined to the water. 15:18.700 --> 15:21.866 align:left position:20% line:83% size:70% An environment which they are perfectly adapted to. 15:23.466 --> 15:25.333 align:left position:12.5% line:71% size:77.5% A watery environment is lovely 15:25.333 --> 15:26.466 align:left position:27.5% line:71% size:62.5% if you're a plant. 15:26.466 --> 15:28.833 align:left position:17.5% line:71% size:72.5% It's like being surrounded 15:28.833 --> 15:31.100 align:left position:22.5% line:71% size:67.5% by a bath of your food. 15:31.100 --> 15:32.533 align:left position:12.5% line:83% size:77.5% You've got nutrients available to you, 15:32.533 --> 15:34.200 align:left position:10% line:89% size:80% there's no danger of drying out, 15:34.200 --> 15:38.733 align:left position:17.5% line:83% size:72.5% and you don't have to worry about gravity or soil. 15:40.600 --> 15:42.833 align:left position:40% line:77% size:50% NARRATOR: Migrating onto land at this point 15:42.833 --> 15:47.066 align:left position:35% line:83% size:55% would require a huge evolutionary leap. 15:47.066 --> 15:49.266 align:left position:17.5% line:71% size:72.5% For plants to live outside of water, 15:49.266 --> 15:51.266 align:left position:20% line:71% size:70% it's a bit like me trying to live on Mars 15:51.266 --> 15:53.066 align:left position:25% line:89% size:65% without a space suit. 15:55.766 --> 15:59.266 align:left position:40% line:77% size:50% NARRATOR: But while marine algae can't quite make it from the ocean 15:59.266 --> 16:00.833 align:left position:32.5% line:89% size:57.5% onto dry land, 16:00.833 --> 16:05.833 align:left position:17.5% line:83% size:72.5% they can adapt to another, more accessible environment: 16:05.833 --> 16:08.733 align:left position:35% line:89% size:55% fresh water. 16:10.866 --> 16:13.800 align:left position:37.5% line:83% size:52.5% Eventually, the algae take up residence 16:13.800 --> 16:16.666 align:left position:35% line:83% size:55% in the lakes, streams, and rivers. 16:19.266 --> 16:23.066 align:left position:27.5% line:83% size:62.5% From there, around half a billion years ago... 16:25.033 --> 16:29.166 align:left position:20% line:83% size:70% ...the algae begin their slow journey onto the land. 16:31.266 --> 16:33.700 align:left position:30% line:83% size:60% We may never know the combination of factors 16:33.700 --> 16:36.766 align:left position:35% line:83% size:55% that spurred green algae on land. 16:36.766 --> 16:39.566 align:left position:40% line:77% size:50% NARRATOR: Maybe it was the changing of Earth's landscapes 16:39.566 --> 16:41.666 align:left position:17.5% line:89% size:72.5% to more clement conditions, 16:41.666 --> 16:45.800 align:left position:27.5% line:83% size:62.5% or the time needed for profound genetic change. 16:45.800 --> 16:50.900 align:left position:12.5% line:83% size:77.5% But whatever the reason, green algae begins to come ashore. 16:53.300 --> 16:55.633 align:left position:25% line:83% size:65% The journey is likely to have started 16:55.633 --> 17:00.900 align:left position:20% line:83% size:70% at the pebbly shorelines of freshwater lakes and rivers. 17:00.900 --> 17:05.666 align:left position:22.5% line:83% size:67.5% Some eventually evolve a thick waxy coating 17:05.666 --> 17:09.966 align:left position:12.5% line:83% size:77.5% that stops them from drying out in their harsh new environment. 17:11.566 --> 17:16.566 align:left position:15% line:83% size:75% But this effective adaptation is a double-edged sword... 17:19.766 --> 17:22.133 align:left position:30% line:83% size:60% ...making it more difficult to absorb nutrients 17:22.133 --> 17:25.333 align:left position:20% line:83% size:70% from their surroundings, like they did in the water, 17:25.333 --> 17:30.533 align:left position:27.5% line:83% size:62.5% and making success on land nearly impossible. 17:36.433 --> 17:41.500 align:left position:22.5% line:83% size:67.5% So, how did plants come to thrive on land? 17:41.500 --> 17:47.100 align:left position:47.5% line:89% size:42.5% ♪ ♪ 17:58.266 --> 18:00.733 align:left position:15% line:83% size:75% Though this may look like an ordinary field, 18:00.733 --> 18:05.466 align:left position:12.5% line:83% size:77.5% it contains one of the world's most important geological sites, 18:05.466 --> 18:08.733 align:left position:22.5% line:83% size:67.5% and the secret to what helped plants survive on land. 18:11.100 --> 18:12.900 align:left position:12.5% line:83% size:77.5% This is an incredibly exciting place for me to be, 18:12.900 --> 18:15.400 align:left position:17.5% line:83% size:72.5% because more than a hundred years ago, this site 18:15.400 --> 18:17.433 align:left position:27.5% line:83% size:62.5% where we are today was excavated to reveal 18:17.433 --> 18:21.466 align:left position:12.5% line:83% size:77.5% the most incredible set of 400- million-year-old plant fossils. 18:25.566 --> 18:28.100 align:left position:10% line:83% size:80% What's special about the fossils from this particular site was, 18:28.100 --> 18:29.633 align:left position:17.5% line:89% size:72.5% the degree of preservation 18:29.633 --> 18:34.033 align:left position:17.5% line:83% size:72.5% of the plant material meant that we got some amazing clues 18:34.033 --> 18:37.333 align:left position:15% line:83% size:75% as to how they actually made landfall in the first place. 18:37.333 --> 18:41.366 align:left position:47.5% line:89% size:42.5% ♪ ♪ 18:41.366 --> 18:44.000 align:left position:40% line:83% size:50% NARRATOR: Around 400 million years ago, 18:44.000 --> 18:45.766 align:left position:17.5% line:83% size:72.5% this area looked completely different 18:45.766 --> 18:47.333 align:left position:20% line:89% size:70% from how it looks today. 18:47.333 --> 18:52.266 align:left position:35% line:83% size:55% It resembled Yellowstone National Park, 18:52.266 --> 18:54.000 align:left position:10% line:89% size:80% where boiling mineralized waters 18:54.000 --> 18:56.766 align:left position:15% line:89% size:75% cascade down rocky terraces. 18:59.166 --> 19:02.100 align:left position:42.5% line:77% size:47.5% FIELD: So the ancient hot springs that were here at Rhynie 19:02.100 --> 19:05.366 align:left position:20% line:83% size:70% turned any plant material that they touched into rock, 19:05.366 --> 19:07.066 align:left position:27.5% line:83% size:62.5% and that got buried over millions of years. 19:07.066 --> 19:11.066 align:left position:12.5% line:83% size:77.5% The resulting bed of fossils is what we call the Rhynie Chert. 19:11.066 --> 19:17.266 align:left position:47.5% line:89% size:42.5% ♪ ♪ 19:17.266 --> 19:19.833 align:left position:12.5% line:89% size:77.5% This fossil is really amazing. 19:19.833 --> 19:22.800 align:left position:25% line:83% size:65% If you look closely, you can see these circles 19:22.800 --> 19:24.800 align:left position:15% line:89% size:75% in the surface of the fossil. 19:27.266 --> 19:30.266 align:left position:30% line:83% size:60% And those circles are actually cross sections 19:30.266 --> 19:32.000 align:left position:25% line:83% size:65% through the stems of ancient plants 19:32.000 --> 19:34.066 align:left position:17.5% line:89% size:72.5% that grew all around here. 19:35.766 --> 19:37.466 align:left position:40% line:77% size:50% NARRATOR: And you can see something unusual 19:37.466 --> 19:40.600 align:left position:25% line:83% size:65% when you look at them under a microscope. 19:40.600 --> 19:42.666 align:left position:32.5% line:83% size:57.5% What we see is, there's this light banding 19:42.666 --> 19:46.066 align:left position:32.5% line:83% size:57.5% around the top, and that's plant tissue, 19:46.066 --> 19:48.133 align:left position:20% line:83% size:70% but if you look even more closely, 19:48.133 --> 19:50.633 align:left position:20% line:83% size:70% you see these dark brown thread-like structures 19:50.633 --> 19:52.166 align:left position:20% line:89% size:70% weaving between the cells 19:52.166 --> 19:54.300 align:left position:25% line:83% size:65% and actually invading some of the plant cells. 19:54.300 --> 19:57.800 align:left position:25% line:83% size:65% And those thread-like structures are actually fungi. 19:59.800 --> 20:02.066 align:left position:40% line:83% size:50% NARRATOR: This incredible evidence shows 20:02.066 --> 20:04.766 align:left position:25% line:83% size:65% that plants actually teamed up with another 20:04.766 --> 20:08.900 align:left position:30% line:83% size:60% kind of life form to help get onto the land-- 20:08.900 --> 20:10.500 align:left position:42.5% line:89% size:47.5% fungi. 20:14.200 --> 20:16.266 align:left position:20% line:83% size:70% Rhynie Chert fossils are some of the only 20:16.266 --> 20:18.666 align:left position:12.5% line:83% size:77.5% fossils on Earth where you can see this ancient link 20:18.666 --> 20:20.433 align:left position:20% line:89% size:70% between plants and fungi. 20:25.400 --> 20:28.233 align:left position:47.5% line:89% size:42.5% ♪ ♪ 20:28.233 --> 20:30.333 align:left position:40% line:77% size:50% NARRATOR: Fungi, however, were not newcomers 20:30.333 --> 20:32.433 align:left position:25% line:89% size:65% to the land surfaces. 20:34.933 --> 20:37.000 align:left position:32.5% line:71% size:57.5% Fungi made its way onto terrestrial land 20:37.000 --> 20:38.600 align:left position:10% line:71% size:80% probably hundreds of millions of years 20:38.600 --> 20:39.733 align:left position:32.5% line:71% size:57.5% before plants. 20:41.833 --> 20:44.200 align:left position:32.5% line:71% size:57.5%   NARRATOR: They were able to live on the land 20:44.200 --> 20:46.200 align:left position:27.5% line:83% size:62.5% consuming bacteria and drawing minerals 20:46.200 --> 20:49.200 align:left position:12.5% line:89% size:77.5% directly from the rocks below. 20:51.600 --> 20:54.000 align:left position:42.5% line:77% size:47.5% FIELD: So fungi are able to get hold of these nutrients 20:54.000 --> 20:58.600 align:left position:20% line:83% size:70% by exuding organic acids out of their fungal hyphae, 20:58.600 --> 20:59.766 align:left position:12.5% line:89% size:77.5% which are thread-like filaments 20:59.766 --> 21:01.566 align:left position:40% line:83% size:50% that form the majority of the fungus. 21:06.700 --> 21:08.833 align:left position:40% line:77% size:50% NARRATOR: Even though the Rhynie Chert fossils 21:08.833 --> 21:12.633 align:left position:37.5% line:83% size:52.5% are around 400 million years old, 21:12.633 --> 21:14.700 align:left position:12.5% line:89% size:77.5% this union of plants and fungi 21:14.700 --> 21:17.900 align:left position:27.5% line:83% size:62.5% must have occurred millions of years earlier. 21:19.633 --> 21:21.700 align:left position:37.5% line:77% size:52.5% CONTRERAS: Plants benefited from the partnership 21:21.700 --> 21:23.900 align:left position:12.5% line:83% size:77.5% because they got the nutrients from the rock's surface 21:23.900 --> 21:25.400 align:left position:25% line:89% size:65% that were broken down 21:25.400 --> 21:26.833 align:left position:35% line:89% size:55% by the fungi. 21:26.833 --> 21:28.333 align:left position:27.5% line:83% size:62.5% And then the fungi benefited because 21:28.333 --> 21:30.233 align:left position:17.5% line:83% size:72.5% they got to use the sugars that were supplied 21:30.233 --> 21:32.966 align:left position:32.5% line:83% size:57.5% from the plants doing photosynthesis. 21:34.166 --> 21:37.900 align:left position:40% line:77% size:50% NARRATOR: Bolstered by this new relationship with fungi, 21:37.900 --> 21:40.733 align:left position:32.5% line:83% size:57.5% plants evolved the ability to exchange sugars 21:40.733 --> 21:44.500 align:left position:27.5% line:83% size:62.5% for vital nutrients like nitrogen and phosphorus. 21:47.300 --> 21:50.100 align:left position:22.5% line:83% size:67.5% Even with their thick, water-retentive coating, 21:50.100 --> 21:53.133 align:left position:22.5% line:83% size:67.5% they can still get all the nutrients they need. 21:54.966 --> 21:58.000 align:left position:17.5% line:83% size:72.5% The emergence of this newly evolved mutual relationship, 21:58.000 --> 21:59.466 align:left position:35% line:89% size:55% or symbiosis, 21:59.466 --> 22:04.266 align:left position:22.5% line:83% size:67.5% is a key turning point for plants' journey. 22:04.266 --> 22:11.766 align:left position:12.5% line:83% size:77.5% Now plants can finally survive out of the water on the land. 22:11.766 --> 22:14.366 align:left position:25% line:71% size:65% The symbiosis between land plants and fungi 22:14.366 --> 22:16.566 align:left position:27.5% line:71% size:62.5% is super-important. 22:16.566 --> 22:19.833 align:left position:32.5% line:83% size:57.5% It's essential for how ecosystems evolved 22:19.833 --> 22:21.966 align:left position:20% line:89% size:70% and how they work today. 22:24.200 --> 22:26.533 align:left position:35% line:83% size:55% BAUMGARTNER: After millions of years 22:26.533 --> 22:28.600 align:left position:12.5% line:89% size:77.5% and lots of evolutionary tries, 22:28.600 --> 22:32.033 align:left position:37.5% line:83% size:52.5% plants were finally onto the land. 22:38.666 --> 22:42.933 align:left position:47.5% line:89% size:42.5% ♪ ♪ 22:42.933 --> 22:46.133 align:left position:40% line:77% size:50% NARRATOR: Plants and fungi created one of Earth's 22:46.133 --> 22:49.400 align:left position:35% line:83% size:55% first complex terrestrial ecosystems. 22:49.400 --> 22:55.400 align:left position:47.5% line:89% size:42.5% ♪ ♪ 22:55.400 --> 23:00.766 align:left position:25% line:83% size:65% And their partnership continues to this day. 23:00.766 --> 23:05.500 align:left position:47.5% line:89% size:42.5% ♪ ♪ 23:05.500 --> 23:08.233 align:left position:27.5% line:83% size:62.5% It's often easy to spot mushrooms, 23:08.233 --> 23:12.233 align:left position:17.5% line:83% size:72.5% which are the reproductive part of some types of fungi. 23:15.133 --> 23:19.933 align:left position:10% line:83% size:80% But most fungi live underground, where we can't see them. 23:19.933 --> 23:21.800 align:left position:22.5% line:5% size:67.5% So this plant has grown 23:21.800 --> 23:23.833 align:left position:22.5% line:5% size:67.5% with a fungal partner, and you can see that, 23:23.833 --> 23:25.800 align:left position:17.5% line:5% size:72.5% with the plant roots being intermingled 23:25.800 --> 23:27.100 align:left position:22.5% line:5% size:67.5% with fungal filaments, 23:27.100 --> 23:29.833 align:left position:20% line:5% size:70% and these wrap themselves around the plant roots 23:29.833 --> 23:32.666 align:left position:32.5% line:5% size:57.5% and form these intimate associations. 23:40.000 --> 23:42.200 align:left position:40% line:83% size:50% NARRATOR: These associations are so vital 23:42.200 --> 23:46.966 align:left position:10% line:83% size:80% that nearly 90% of plants living today are dependent on them. 23:46.966 --> 23:50.300 align:left position:42.5% line:77% size:47.5% FIELD: It's really easy to overlook fungi because, 23:50.300 --> 23:52.866 align:left position:27.5% line:83% size:62.5% for the most part, they live underground, 23:52.866 --> 23:55.333 align:left position:12.5% line:83% size:77.5% whilst plants grow much taller and are more obvious. 23:58.033 --> 24:00.233 align:left position:40% line:83% size:50% NARRATOR: But some fossil evidence 24:00.233 --> 24:02.733 align:left position:37.5% line:83% size:52.5% from around 420 million years ago 24:02.733 --> 24:06.900 align:left position:17.5% line:83% size:72.5% suggests that this balance once looked quite different. 24:14.366 --> 24:19.400 align:left position:47.5% line:89% size:42.5% ♪ ♪ 24:28.500 --> 24:32.700 align:left position:15% line:5% size:75% Something utterly astonishing has happened to some fungi. 24:35.433 --> 24:37.933 align:left position:20% line:5% size:70% They have become giants. 24:40.133 --> 24:42.666 align:left position:47.5% line:5% size:42.5% ♪ ♪ 24:42.666 --> 24:46.766 align:left position:15% line:5% size:75% Colossal fungal spikes tower over the landscape. 24:48.433 --> 24:51.733 align:left position:15% line:5% size:75% They're called Prototaxites. 24:56.600 --> 24:59.266 align:left position:17.5% line:5% size:72.5% Standing over 20 feet high, 24:59.266 --> 25:01.633 align:left position:32.5% line:83% size:57.5% they reproduce by releasing spores 25:01.633 --> 25:06.333 align:left position:15% line:89% size:75% that are carried by the wind. 25:06.333 --> 25:10.300 align:left position:37.5% line:77% size:52.5% CONTRERAS: The Prototaxites landscape would've been an alien world. 25:12.733 --> 25:14.600 align:left position:40% line:83% size:50% NARRATOR: So alien 25:14.600 --> 25:19.366 align:left position:17.5% line:5% size:72.5% that when the fossils were first discovered back in 1843, 25:19.366 --> 25:22.800 align:left position:27.5% line:5% size:62.5% scientists were not even sure what they were. 25:25.166 --> 25:26.900 align:left position:25% line:71% size:65% It was a very strange 25:26.900 --> 25:28.533 align:left position:27.5% line:71% size:62.5% and odd thing when people found it. 25:28.533 --> 25:31.133 align:left position:27.5% line:71% size:62.5%   It was shaped like a chunk of wood. 25:33.100 --> 25:36.933 align:left position:10% line:77% size:80% NARRATOR: But when they took a much closer look, 25:36.933 --> 25:40.466 align:left position:10% line:83% size:80% they discovered something incredible. 25:40.466 --> 25:41.666 align:left position:32.5% line:5% size:57.5% So what this is 25:41.666 --> 25:43.866 align:left position:32.5% line:5% size:57.5% is a very thin slice of Prototaxites. 25:45.633 --> 25:48.800 align:left position:47.5% line:89% size:42.5% ♪ ♪ 25:48.800 --> 25:51.066 align:left position:12.5% line:89% size:77.5% And we find that, unlike a log, 25:51.066 --> 25:53.000 align:left position:22.5% line:83% size:67.5% which would be full of woody cells, 25:53.000 --> 25:55.533 align:left position:12.5% line:83% size:77.5% instead we find a mass of these fungal filaments, 25:55.533 --> 25:59.133 align:left position:17.5% line:89% size:72.5% reminiscent of fungi today. 25:59.133 --> 26:00.733 align:left position:40% line:83% size:50% JOHNSON: It creates, 26:00.733 --> 26:04.300 align:left position:17.5% line:83% size:72.5% in my mind, one of the most bizarre prehistoric landscapes 26:04.300 --> 26:06.166 align:left position:22.5% line:83% size:67.5% of all, 'cause there's nothing like it today. 26:09.200 --> 26:13.466 align:left position:40% line:77% size:50% NARRATOR: The towering Prototaxites dominate the landscape. 26:14.866 --> 26:17.766 align:left position:25% line:83% size:65% Plants, by contrast, are still tiny, 26:17.766 --> 26:21.066 align:left position:32.5% line:83% size:57.5% measuring just a few inches or less. 26:22.500 --> 26:24.433 align:left position:17.5% line:89% size:72.5% Stuck by the water's edge, 26:24.433 --> 26:28.000 align:left position:35% line:83% size:55% near to where they first made landfall. 26:30.000 --> 26:31.833 align:left position:42.5% line:83% size:47.5% LYDON: So, even though plants 26:31.833 --> 26:33.466 align:left position:12.5% line:71% size:77.5% have made it out of the water, 26:33.466 --> 26:35.066 align:left position:27.5% line:71% size:62.5% they're still confined to the edges 26:35.066 --> 26:36.933 align:left position:25% line:71% size:65% of lakes and rivers. 26:36.933 --> 26:39.700 align:left position:20% line:71% size:70% A lot of the land surface on Earth at this time 26:39.700 --> 26:45.266 align:left position:20% line:71% size:70%   was also quite dry, and maybe rocky or very sandy. 26:45.266 --> 26:48.800 align:left position:40% line:77% size:50% NARRATOR: With no way of holding on to that water inland, 26:48.800 --> 26:53.666 align:left position:22.5% line:83% size:67.5% Earth could've remained a fungal paradise. 26:53.666 --> 26:55.200 align:left position:32.5% line:71% size:57.5% For plants to establish themselves 26:55.200 --> 26:56.700 align:left position:25% line:71% size:65% away from the water, 26:56.700 --> 26:59.366 align:left position:12.5% line:71% size:77.5% they were gonna have to change, 26:59.366 --> 27:01.266 align:left position:27.5% line:71% size:62.5% to evolve new traits that allowed them 27:01.266 --> 27:03.566 align:left position:12.5% line:89% size:77.5% to live in the new environment. 27:07.700 --> 27:10.766 align:left position:40% line:77% size:50% NARRATOR: But there is a vital ingredient missing. 27:10.766 --> 27:14.900 align:left position:47.5% line:89% size:42.5% ♪ ♪ 27:14.900 --> 27:16.933 align:left position:10% line:5% size:80% Something that seems like it has 27:16.933 --> 27:20.033 align:left position:30% line:5% size:60% always been part of the fabric of Earth. 27:22.066 --> 27:25.866 align:left position:47.5% line:89% size:42.5% ♪ ♪ 27:25.866 --> 27:28.366 align:left position:45% line:89% size:45% Soil. 27:33.100 --> 27:37.433 align:left position:20% line:83% size:70% Just one teaspoon of this crumbly brown stuff 27:37.433 --> 27:39.666 align:left position:12.5% line:71% size:77.5% includes more living organisms 27:39.666 --> 27:41.166 align:left position:20% line:71% size:70% than there are people on the planet, 27:41.166 --> 27:44.333 align:left position:35% line:71% size:55% and that is absolutely unbelievable. 27:45.433 --> 27:47.066 align:left position:17.5% line:5% size:72.5% Despite the fact that soils 27:47.066 --> 27:49.933 align:left position:12.5% line:5% size:77.5% only make up a small portion of the Earth's surface, 27:49.933 --> 27:51.633 align:left position:27.5% line:83% size:62.5% there are thousands of varieties, 27:51.633 --> 27:53.733 align:left position:17.5% line:83% size:72.5% including more than 20,000 in the U.S. alone. 27:53.733 --> 27:59.433 align:left position:47.5% line:89% size:42.5% ♪ ♪ 27:59.433 --> 28:01.466 align:left position:40% line:77% size:50% NARRATOR: Soil is formed by the combined action 28:01.466 --> 28:04.133 align:left position:35% line:83% size:55% of organisms like bacteria and fungi 28:04.133 --> 28:09.566 align:left position:15% line:83% size:75% working on biological matter like fallen leaves. 28:09.566 --> 28:11.966 align:left position:35% line:5% size:55% Combined with particles like sand or clay, 28:11.966 --> 28:14.366 align:left position:40% line:5% size:50% it is the perfect material to hold 28:14.366 --> 28:17.833 align:left position:27.5% line:83% size:62.5% all the ingredients plants need to thrive. 28:21.033 --> 28:23.633 align:left position:10% line:83% size:80% Soil traps and holds on to water and nutrients 28:23.633 --> 28:26.100 align:left position:32.5% line:83% size:57.5% so that plants can use them all year round. 28:28.666 --> 28:30.500 align:left position:10% line:89% size:80% If we look in the fossil record, 28:30.500 --> 28:33.500 align:left position:30% line:83% size:60% we see something absolutely remarkable. 28:33.500 --> 28:35.733 align:left position:15% line:89% size:75% About 470 million years ago, 28:35.733 --> 28:38.700 align:left position:17.5% line:83% size:72.5% soils as we know them today did not exist. 28:39.900 --> 28:42.100 align:left position:15% line:83% size:75% Instead, we had the earliest version of soils, 28:42.100 --> 28:44.100 align:left position:20% line:89% size:70% what we call proto-soils. 28:44.100 --> 28:46.266 align:left position:32.5% line:83% size:57.5% They were only maybe a millimeter thick. 28:48.466 --> 28:50.433 align:left position:25% line:83% size:65% They were formed from very thin layers 28:50.433 --> 28:52.666 align:left position:15% line:83% size:75% of bacterial or fungal mats; they just didn't have 28:52.666 --> 28:55.533 align:left position:20% line:83% size:70% the same kind of building blocks that soils today have. 28:59.900 --> 29:04.500 align:left position:40% line:77% size:50% NARRATOR: Early fungi do not need soil to thrive. 29:06.800 --> 29:09.866 align:left position:20% line:83% size:70% But plants need something to support and nourish them 29:09.866 --> 29:13.700 align:left position:22.5% line:83% size:67.5% if they are to survive farther away from the water. 29:15.433 --> 29:20.366 align:left position:15% line:89% size:75% Soon, they start making soil. 29:20.366 --> 29:25.266 align:left position:47.5% line:89% size:42.5% ♪ ♪ 29:25.266 --> 29:28.566 align:left position:27.5% line:89% size:62.5% They begin slowly, 29:28.566 --> 29:31.733 align:left position:22.5% line:89% size:67.5% over millions of years, 29:31.733 --> 29:33.700 align:left position:17.5% line:89% size:72.5% breaking down the bare rock 29:33.700 --> 29:38.933 align:left position:27.5% line:83% size:62.5% with tiny root-like structures called rhizoids, 29:38.933 --> 29:42.366 align:left position:27.5% line:83% size:62.5% mixing in nutrients from their fungal partners. 29:43.533 --> 29:49.100 align:left position:47.5% line:89% size:42.5% ♪ ♪ 29:49.100 --> 29:52.533 align:left position:35% line:83% size:55% But the true transformative ingredient... 29:55.033 --> 29:57.900 align:left position:15% line:89% size:75% ...is the plants themselves. 30:04.400 --> 30:08.566 align:left position:17.5% line:83% size:72.5% Generation after generation breaks down after death, 30:08.566 --> 30:11.266 align:left position:17.5% line:89% size:72.5% building up a bed of soil. 30:16.100 --> 30:21.133 align:left position:22.5% line:83% size:67.5% Turning once inert rock into a living layer. 30:26.333 --> 30:31.366 align:left position:47.5% line:89% size:42.5% ♪ ♪ 30:42.000 --> 30:46.200 align:left position:12.5% line:89% size:77.5% Fast-forward 20 million years. 30:46.200 --> 30:47.833 align:left position:25% line:83% size:65% And with the growing soil layers, 30:47.833 --> 30:49.966 align:left position:20% line:89% size:70% plants are transforming. 30:49.966 --> 30:54.000 align:left position:47.5% line:89% size:42.5% ♪ ♪ 30:56.800 --> 30:58.833 align:left position:25% line:89% size:65% They're much bigger. 31:00.966 --> 31:03.500 align:left position:12.5% line:83% size:77.5% And their ability to move water through their tissues 31:03.500 --> 31:05.700 align:left position:25% line:89% size:65% by a kind of plumbing 31:05.700 --> 31:09.133 align:left position:20% line:83% size:70% has allowed them to live farther away from the water. 31:12.166 --> 31:15.766 align:left position:20% line:83% size:70% They're now more varied, with deeper roots 31:15.766 --> 31:18.600 align:left position:12.5% line:89% size:77.5% to support their taller stems. 31:24.633 --> 31:27.266 align:left position:12.5% line:89% size:77.5% Prototaxites, the giant fungi, 31:27.266 --> 31:29.466 align:left position:22.5% line:89% size:67.5% still tower over them. 31:32.866 --> 31:34.700 align:left position:17.5% line:89% size:72.5% But soil makes it possible 31:34.700 --> 31:38.433 align:left position:25% line:83% size:65% for plants to thrive much farther inland. 31:42.366 --> 31:46.800 align:left position:22.5% line:83% size:67.5% Their wind-borne spores reach drier upland areas. 31:46.800 --> 31:53.633 align:left position:47.5% line:89% size:42.5% ♪ ♪ 31:53.633 --> 31:56.066 align:left position:15% line:89% size:75% Without the barrier that kept 31:56.066 --> 31:59.000 align:left position:22.5% line:83% size:67.5% terrestrial plant life near the water's edge, 31:59.000 --> 32:03.333 align:left position:20% line:89% size:70% plants scale new heights, 32:03.333 --> 32:07.166 align:left position:35% line:83% size:55% and diversify as they occupy new environments. 32:07.166 --> 32:10.033 align:left position:47.5% line:89% size:42.5% ♪ ♪ 32:10.033 --> 32:13.433 align:left position:27.5% line:89% size:62.5% For the first time, 32:13.433 --> 32:17.933 align:left position:15% line:83% size:75% significant parts of Earth's land are turning green. 32:20.400 --> 32:22.000 align:left position:42.5% line:83% size:47.5% FIELD: Plants changed our landscape 32:22.000 --> 32:24.100 align:left position:17.5% line:71% size:72.5% by terra-forming bare rock 32:24.100 --> 32:25.466 align:left position:27.5% line:71% size:62.5% into living matter. 32:25.466 --> 32:27.033 align:left position:32.5% line:71% size:57.5% Life and Earth, 32:27.033 --> 32:28.433 align:left position:12.5% line:71% size:77.5% they're not separate entities-- 32:28.433 --> 32:30.000 align:left position:12.5% line:71% size:77.5% they're totally interconnected. 32:36.500 --> 32:38.933 align:left position:15% line:83% size:75% So, these changes that plants caused to the Earth's surface 32:38.933 --> 32:40.566 align:left position:22.5% line:89% size:67.5% had huge consequences. 32:40.566 --> 32:43.233 align:left position:22.5% line:83% size:67.5% Pretty much everything about the landscape 32:43.233 --> 32:48.166 align:left position:32.5% line:83% size:57.5% was influenced by plants moving onto the land. 32:48.166 --> 32:51.466 align:left position:40% line:77% size:50% NARRATOR: But plants don't just alter Earth's surface. 32:51.466 --> 32:54.433 align:left position:47.5% line:89% size:42.5% ♪ ♪ 32:54.433 --> 32:56.900 align:left position:40% line:83% size:50% CARVALHO: As plants are creating 32:56.900 --> 32:59.133 align:left position:15% line:71% size:75% this beautiful green planet, 32:59.133 --> 33:01.433 align:left position:20% line:71% size:70% carbon dioxide levels in the atmosphere 33:01.433 --> 33:04.066 align:left position:17.5% line:89% size:72.5% actually start going down. 33:04.066 --> 33:07.133 align:left position:27.5% line:83% size:62.5% Part of the reason has to do with plants. 33:07.133 --> 33:08.700 align:left position:22.5% line:89% size:67.5% As plants are growing, 33:08.700 --> 33:11.033 align:left position:25% line:83% size:65% they're accumulating carbon dioxide 33:11.033 --> 33:12.966 align:left position:17.5% line:83% size:72.5% as they're transforming it into sugars, 33:12.966 --> 33:14.766 align:left position:35% line:83% size:55% and making up their plant bodies. 33:14.766 --> 33:18.400 align:left position:15% line:83% size:75% As plants had exploded across the landscape, 33:18.400 --> 33:23.466 align:left position:25% line:83% size:65% CO2 in the atmosphere decreased by upwards of 25%. 33:24.733 --> 33:28.333 align:left position:40% line:77% size:50% NARRATOR: Ironically, this poses a problem to plants. 33:32.633 --> 33:36.466 align:left position:22.5% line:83% size:67.5% Because carbon dioxide is plant food. 33:40.000 --> 33:43.566 align:left position:27.5% line:83% size:62.5% They absorb the CO2 for photosynthesis 33:43.566 --> 33:47.700 align:left position:27.5% line:83% size:62.5% through structures called stomata. 33:49.333 --> 33:51.633 align:left position:37.5% line:77% size:52.5% CONTRERAS: Stomata are these cellular complexes 33:51.633 --> 33:53.666 align:left position:12.5% line:89% size:77.5% that have a pore in the middle, 33:53.666 --> 33:55.733 align:left position:12.5% line:83% size:77.5% and these are the gas exchange pores for plants, 33:55.733 --> 33:58.200 align:left position:20% line:83% size:70% so it's the way they move carbon dioxide 33:58.200 --> 34:00.866 align:left position:15% line:89% size:75% in and out of the plant body. 34:02.666 --> 34:05.933 align:left position:10% line:83% size:80% If you look at stomata under the microscope, it almost looks like 34:05.933 --> 34:09.733 align:left position:30% line:5% size:60% they're breathing as they open and close. 34:09.733 --> 34:11.533 align:left position:40% line:5% size:50% JOHNSON: In early land plants, 34:11.533 --> 34:14.033 align:left position:17.5% line:5% size:72.5% between 420 and 390 million years ago, 34:14.033 --> 34:16.400 align:left position:25% line:71% size:65% most land plants had 34:16.400 --> 34:18.700 align:left position:15% line:71% size:75% their stomata on their stems. 34:18.700 --> 34:20.966 align:left position:17.5% line:83% size:72.5% The falling carbon dioxide levels 34:20.966 --> 34:24.133 align:left position:15% line:89% size:75% had a huge impact on plants. 34:24.133 --> 34:26.600 align:left position:22.5% line:83% size:67.5% In order to get as much carbon dioxide 34:26.600 --> 34:30.100 align:left position:25% line:83% size:65% as they were before, they would need more stomata. 34:30.100 --> 34:31.433 align:left position:22.5% line:89% size:67.5% But where to put them? 34:33.533 --> 34:37.933 align:left position:37.5% line:77% size:52.5% CONTRERAS: The answer was as elegant as it was revolutionary. 34:37.933 --> 34:42.433 align:left position:47.5% line:89% size:42.5% ♪ ♪ 34:42.433 --> 34:44.800 align:left position:42.5% line:89% size:47.5% Leaves. 34:49.866 --> 34:52.533 align:left position:47.5% line:89% size:42.5% ♪ ♪ 34:52.533 --> 34:55.233 align:left position:40% line:77% size:50% NARRATOR: Leaves came about as an adaptation 34:55.233 --> 34:59.800 align:left position:35% line:83% size:55% to cope with the changing atmosphere. 34:59.800 --> 35:01.733 align:left position:22.5% line:83% size:67.5% Leaves make plants more efficient 35:01.733 --> 35:03.733 align:left position:35% line:83% size:55% by providing greater surface area 35:03.733 --> 35:08.633 align:left position:17.5% line:83% size:72.5% for photosynthesis and for taking up CO2 for gas exchange. 35:11.433 --> 35:15.066 align:left position:47.5% line:89% size:42.5% ♪ ♪ 35:15.066 --> 35:17.066 align:left position:40% line:83% size:50% NARRATOR: In a relatively short time, 35:17.066 --> 35:20.133 align:left position:37.5% line:83% size:52.5% most plants had evolved leaves, 35:20.133 --> 35:23.433 align:left position:27.5% line:83% size:62.5% but this seemingly small innovation would trigger 35:23.433 --> 35:26.800 align:left position:22.5% line:83% size:67.5% an entirely new dynamic between plants. 35:31.200 --> 35:33.366 align:left position:27.5% line:83% size:62.5% When we have plants growing close to each other, 35:33.366 --> 35:35.700 align:left position:27.5% line:83% size:62.5% these big surfaces that capture sunlight 35:35.700 --> 35:39.566 align:left position:10% line:83% size:80% are creating competition because of the shading of each other. 35:42.900 --> 35:45.633 align:left position:40% line:83% size:50% NARRATOR: This started a race for light 35:45.633 --> 35:51.300 align:left position:12.5% line:83% size:77.5% that will ultimately transform the landscape once again. 35:51.300 --> 35:56.333 align:left position:47.5% line:89% size:42.5% ♪ ♪ 36:03.533 --> 36:06.833 align:left position:17.5% line:83% size:72.5% With leaves supporting this increased photosynthesis, 36:06.833 --> 36:09.233 align:left position:17.5% line:83% size:72.5% some plants begin building their bodies 36:09.233 --> 36:14.233 align:left position:32.5% line:83% size:57.5% out of tougher biological material, 36:14.233 --> 36:16.733 align:left position:45% line:89% size:45% wood, 36:16.733 --> 36:20.833 align:left position:15% line:83% size:75% which leads to the rise of a whole new type of organism-- 36:20.833 --> 36:23.733 align:left position:17.5% line:83% size:72.5% biological machines unlike anything 36:23.733 --> 36:26.433 align:left position:22.5% line:89% size:67.5% Earth has seen before. 36:26.433 --> 36:30.600 align:left position:17.5% line:83% size:72.5% Trees are photosynthesizing powerhouses. 36:30.600 --> 36:33.700 align:left position:17.5% line:83% size:72.5% With strong wooden trunks, they can grow much taller, 36:33.700 --> 36:36.133 align:left position:27.5% line:83% size:62.5% effectively pushing past the competition 36:36.133 --> 36:38.966 align:left position:12.5% line:89% size:77.5% towards the sunlight they need. 36:42.166 --> 36:44.233 align:left position:12.5% line:71% size:77.5% Trees were a huge step forward 36:44.233 --> 36:46.000 align:left position:17.5% line:71% size:72.5% for terrestrial plant life. 36:46.000 --> 36:47.600 align:left position:25% line:71% size:65% Trees were remarkable 36:47.600 --> 36:49.933 align:left position:20% line:71% size:70% at exploiting resources. 36:49.933 --> 36:51.533 align:left position:22.5% line:83% size:67.5% They had enormous, deep rooting systems, 36:51.533 --> 36:53.866 align:left position:35% line:83% size:55% allowing them to access water and nutrients, 36:53.866 --> 36:57.233 align:left position:12.5% line:83% size:77.5% they had these giant stems for stability, and on top of that, 36:57.233 --> 36:59.833 align:left position:27.5% line:83% size:62.5% a canopy of leaves for photosynthesis. 37:01.466 --> 37:03.833 align:left position:20% line:5% size:70% Archaeopteris, like this one here, 37:03.833 --> 37:06.933 align:left position:12.5% line:5% size:77.5% was one of the earliest trees, 37:06.933 --> 37:09.733 align:left position:25% line:5% size:65% and they formed many of the Earth's first forests. 37:11.566 --> 37:15.833 align:left position:25% line:83% size:65% Here's one branch of Archaeopteris. 37:15.833 --> 37:17.233 align:left position:22.5% line:89% size:67.5% It has big woody stems, 37:17.233 --> 37:20.166 align:left position:17.5% line:83% size:72.5% but the leaves kind of look like ferns, 37:20.166 --> 37:22.466 align:left position:30% line:89% size:60% but kind of not. 37:22.466 --> 37:23.966 align:left position:35% line:83% size:55% BAUMGARTNER: The ability of Archaeopteris 37:23.966 --> 37:26.666 align:left position:25% line:71% size:65% to consume vast amounts of carbon dioxide 37:26.666 --> 37:28.700 align:left position:17.5% line:71% size:72.5% allowed them to grow to be 37:28.700 --> 37:30.133 align:left position:25% line:71% size:65% almost 100 feet tall. 37:30.133 --> 37:35.600 align:left position:47.5% line:89% size:42.5% ♪ ♪ 37:35.600 --> 37:38.266 align:left position:40% line:77% size:50% JOHNSON: I often like to say that trees are made out of gas. 37:38.266 --> 37:43.366 align:left position:17.5% line:83% size:72.5% They absorb carbon dioxide from the atmosphere 37:43.366 --> 37:46.733 align:left position:20% line:83% size:70% to make the carbohydrate in their plant bodies. 37:48.866 --> 37:53.900 align:left position:47.5% line:89% size:42.5% ♪ ♪ 38:00.100 --> 38:04.066 align:left position:40% line:77% size:50% NARRATOR: Earth is on its way to becoming a forest world. 38:06.400 --> 38:11.433 align:left position:47.5% line:89% size:42.5% ♪ ♪ 38:16.966 --> 38:21.266 align:left position:17.5% line:83% size:72.5% The Prototaxites are gone, never to return. 38:23.900 --> 38:28.933 align:left position:47.5% line:89% size:42.5% ♪ ♪ 38:31.600 --> 38:35.600 align:left position:15% line:83% size:75% And the majority of the fungi retreats from the surface, 38:35.600 --> 38:40.833 align:left position:17.5% line:83% size:72.5% thriving in giant networks below the ground, 38:40.833 --> 38:44.500 align:left position:20% line:83% size:70% where they have remained ever since, 38:44.500 --> 38:47.600 align:left position:32.5% line:83% size:57.5% a vital partner to the plant life above them. 38:50.366 --> 38:52.500 align:left position:25% line:83% size:65% The spread of plants from the water's edge 38:52.500 --> 38:55.800 align:left position:17.5% line:83% size:72.5% across the planet's surface is dramatic. 39:05.100 --> 39:10.366 align:left position:47.5% line:89% size:42.5% ♪ ♪ 39:10.366 --> 39:13.966 align:left position:30% line:83% size:60% Plants transform the face of the planet. 39:17.000 --> 39:18.900 align:left position:30% line:89% size:60% But in doing so, 39:18.900 --> 39:23.233 align:left position:22.5% line:83% size:67.5% they also set the stage for global upheaval. 39:27.933 --> 39:33.833 align:left position:47.5% line:5% size:42.5% ♪ ♪ 39:33.833 --> 39:37.766 align:left position:22.5% line:5% size:67.5% This beautiful coastal redwood forest 39:37.766 --> 39:40.233 align:left position:12.5% line:5% size:77.5% is part of a dynamic ecosystem, 39:40.233 --> 39:42.433 align:left position:27.5% line:5% size:62.5% with trees playing an essential role, 39:42.433 --> 39:47.666 align:left position:27.5% line:5% size:62.5% even after they can no longer stand tall. 39:47.666 --> 39:51.500 align:left position:20% line:5% size:70% A fallen coastal redwood locals call the Phoenix Tree 39:51.500 --> 39:53.966 align:left position:10% line:5% size:80% is a rare instance of being able to see 39:53.966 --> 39:57.833 align:left position:22.5% line:5% size:67.5% the interconnectedness of the forests above the ground. 40:00.400 --> 40:03.233 align:left position:15% line:83% size:75% So this tree fell over about 86 years ago, 40:03.233 --> 40:04.433 align:left position:12.5% line:89% size:77.5% and the special thing about it 40:04.433 --> 40:06.000 align:left position:17.5% line:83% size:72.5% is that that wasn't a death sentence. 40:07.566 --> 40:09.366 align:left position:40% line:83% size:50% Instead, beneath each separate branch 40:09.366 --> 40:11.433 align:left position:17.5% line:89% size:72.5% are roots that are forming, 40:11.433 --> 40:13.966 align:left position:22.5% line:83% size:67.5% and these branches are eventually going to become 40:13.966 --> 40:17.000 align:left position:15% line:89% size:75% their own independent trees. 40:18.066 --> 40:23.700 align:left position:47.5% line:89% size:42.5% ♪ ♪ 40:23.700 --> 40:25.533 align:left position:12.5% line:89% size:77.5% These spread-out, shallow roots 40:25.533 --> 40:27.633 align:left position:22.5% line:83% size:67.5% allow them to basically hold hands with each other 40:27.633 --> 40:30.900 align:left position:17.5% line:83% size:72.5% for stability, and they can even share resources 40:30.900 --> 40:33.200 align:left position:20% line:89% size:70% like water and nutrients. 40:34.733 --> 40:38.100 align:left position:40% line:5% size:50% NARRATOR: But this tree is just one small piece 40:38.100 --> 40:41.300 align:left position:40% line:5% size:50% of a vast and interconnected system. 40:41.300 --> 40:43.733 align:left position:25% line:5% size:65% It's a living bridge that connects the atmosphere 40:43.733 --> 40:46.866 align:left position:35% line:5% size:55% with the soil and the life within it. 40:48.766 --> 40:51.066 align:left position:25% line:83% size:65% When trees are alive, they are homes, 40:51.066 --> 40:53.433 align:left position:32.5% line:83% size:57.5% they are food, and they provide moisture 40:53.433 --> 40:55.366 align:left position:12.5% line:89% size:77.5% to the environment around them. 40:57.900 --> 40:59.100 align:left position:30% line:83% size:60% But they actually provide the same things 40:59.100 --> 41:00.433 align:left position:20% line:89% size:70% after they've decomposed. 41:05.266 --> 41:08.100 align:left position:40% line:77% size:50% NARRATOR: Dead trees are broken down by organisms 41:08.100 --> 41:10.400 align:left position:22.5% line:83% size:67.5% that return the carbon that was locked in them 41:10.400 --> 41:13.466 align:left position:20% line:83% size:70% back into the atmosphere through respiration. 41:14.600 --> 41:19.366 align:left position:12.5% line:83% size:77.5% And this equilibrium helps keep the atmospheric CO2 in balance. 41:26.233 --> 41:28.700 align:left position:37.5% line:83% size:52.5% But around 350 million years ago, 41:28.700 --> 41:32.433 align:left position:15% line:89% size:75% that balance was interrupted. 41:34.633 --> 41:37.933 align:left position:27.5% line:83% size:62.5% Leading to a crisis that would threaten the survival 41:37.933 --> 41:40.233 align:left position:25% line:89% size:65% of all life on Earth. 41:42.733 --> 41:47.233 align:left position:47.5% line:89% size:42.5% ♪ ♪ 41:53.200 --> 41:56.100 align:left position:27.5% line:83% size:62.5% The rapid spread of terrestrial plant life 41:56.100 --> 41:59.666 align:left position:10% line:89% size:80% has left Earth a changed planet. 42:03.066 --> 42:07.366 align:left position:17.5% line:83% size:72.5% In the Southern Hemisphere, ice sheets form. 42:09.866 --> 42:13.166 align:left position:12.5% line:89% size:77.5% But in the equatorial regions, 42:13.166 --> 42:17.800 align:left position:15% line:83% size:75% the climate is still very hot and wet. 42:17.800 --> 42:22.833 align:left position:47.5% line:89% size:42.5% ♪ ♪ 42:28.333 --> 42:32.033 align:left position:20% line:83% size:70% As the ice sheets expand and contract, 42:32.033 --> 42:35.033 align:left position:22.5% line:83% size:67.5% over millions of years, sea levels fluctuate, 42:35.033 --> 42:37.800 align:left position:25% line:89% size:65% creating huge deltas 42:37.800 --> 42:40.566 align:left position:20% line:83% size:70% where vast swamp forests spring up... 42:43.933 --> 42:48.266 align:left position:25% line:83% size:65% ...covering millions of square miles... 42:50.666 --> 42:54.766 align:left position:15% line:83% size:75% ...and giving rise to a whole host of new plant species 42:54.766 --> 42:57.933 align:left position:37.5% line:83% size:52.5% that thrive in these wet conditions. 43:01.666 --> 43:04.366 align:left position:22.5% line:83% size:67.5% The largest among them, Lepidodendrons, 43:04.366 --> 43:07.566 align:left position:20% line:89% size:70% grow over 160 feet tall. 43:11.833 --> 43:14.500 align:left position:32.5% line:83% size:57.5% These are part of a group called lycopods, 43:14.500 --> 43:16.600 align:left position:32.5% line:89% size:57.5% or scale trees. 43:20.633 --> 43:23.533 align:left position:12.5% line:5% size:77.5% It looks like it's not a plant. 43:23.533 --> 43:25.400 align:left position:12.5% line:5% size:77.5% People often find these things, say, 43:25.400 --> 43:26.800 align:left position:17.5% line:89% size:72.5% "These thing's got scales. 43:26.800 --> 43:28.800 align:left position:20% line:83% size:70% "It looks like a garfish, or a dinosaur, 43:28.800 --> 43:31.433 align:left position:22.5% line:83% size:67.5% or some kind of snake, a reptile." 43:31.433 --> 43:34.433 align:left position:35% line:83% size:55% And in fact, these are called scale trees. 43:38.433 --> 43:40.933 align:left position:40% line:77% size:50% NARRATOR: The swamp forests these trees grew in 43:40.933 --> 43:44.000 align:left position:32.5% line:83% size:57.5% would've looked similar to today's, 43:44.000 --> 43:46.966 align:left position:17.5% line:83% size:72.5% except those trees would've grown incredibly quickly, 43:46.966 --> 43:48.700 align:left position:22.5% line:89% size:67.5% creating a huge amount 43:48.700 --> 43:52.566 align:left position:35% line:83% size:55% of plant mass in a very short time. 43:52.566 --> 43:55.600 align:left position:35% line:77% size:55% HETHERINGTON: Lepidendron trees could be enormous, 43:55.600 --> 43:56.866 align:left position:25% line:83% size:65% and one hypothesis is that they reach 43:56.866 --> 44:00.900 align:left position:27.5% line:83% size:62.5% this amazing height in as little as 15 years. 44:02.066 --> 44:03.900 align:left position:17.5% line:71% size:72.5% So this rapid plant growth 44:03.900 --> 44:05.933 align:left position:27.5% line:71% size:62.5% would've removed enormous amounts 44:05.933 --> 44:08.700 align:left position:27.5% line:71% size:62.5%   of carbon dioxide from the atmosphere. 44:10.233 --> 44:11.933 align:left position:40% line:83% size:50% NARRATOR: But this was not the only impact 44:11.933 --> 44:15.900 align:left position:37.5% line:83% size:52.5% these trees had on the atmosphere. 44:15.900 --> 44:17.700 align:left position:40% line:83% size:50% CARVALHO: So when these massive trees 44:17.700 --> 44:21.266 align:left position:25% line:83% size:65% fell into waterlogged conditions, 44:21.266 --> 44:23.500 align:left position:15% line:83% size:75% which typically are very low in oxygen, 44:23.500 --> 44:26.366 align:left position:12.5% line:71% size:77.5% they become really, really hard to break down. 44:26.366 --> 44:27.533 align:left position:35% line:71% size:55% Through time, 44:27.533 --> 44:29.133 align:left position:32.5% line:71% size:57.5% all this organic matter accumulates. 44:32.900 --> 44:36.600 align:left position:40% line:77% size:50% NARRATOR: This huge amount of plant mass was not broken down 44:36.600 --> 44:40.833 align:left position:12.5% line:83% size:77.5% and returned to the atmosphere, as typically happens today. 44:40.833 --> 44:42.500 align:left position:17.5% line:89% size:72.5% Instead, it was locked away 44:42.500 --> 44:46.066 align:left position:25% line:83% size:65% in the sludge of the swamp forests. 44:47.866 --> 44:49.633 align:left position:32.5% line:71% size:57.5% This would have immense consequences 44:49.633 --> 44:51.133 align:left position:20% line:71% size:70% for the Earth's climate. 44:51.133 --> 44:56.166 align:left position:47.5% line:5% size:42.5% ♪ ♪ 44:57.866 --> 45:00.633 align:left position:40% line:5% size:50% NARRATOR: The deep basins of the tropical swamp forests 45:00.633 --> 45:03.133 align:left position:25% line:83% size:65% were log-jammed with fallen trees 45:03.133 --> 45:06.633 align:left position:17.5% line:83% size:72.5% and partially decayed plant matter that formed peat. 45:08.700 --> 45:11.500 align:left position:20% line:83% size:70% This carbon-rich mixture was then buried 45:11.500 --> 45:15.933 align:left position:15% line:83% size:75% and compressed under millions of tons of marine sediment, 45:15.933 --> 45:18.200 align:left position:35% line:83% size:55% deposited by fluctuating sea levels. 45:20.500 --> 45:24.100 align:left position:20% line:83% size:70% All the ingredients were in place, 45:24.100 --> 45:25.900 align:left position:22.5% line:89% size:67.5% slowly transforming... 45:25.900 --> 45:29.666 align:left position:30% line:89% size:60% (birds squawking) 45:29.666 --> 45:31.200 align:left position:17.5% line:83% size:72.5% ...into an incredible type of rock. 45:42.000 --> 45:44.833 align:left position:20% line:83% size:70% We can see that substance in the black seam 45:44.833 --> 45:48.366 align:left position:17.5% line:83% size:72.5% behind me, within the cliff face, within the rock records. 45:48.366 --> 45:52.400 align:left position:27.5% line:83% size:62.5% And that substance is actually coal. 45:55.000 --> 45:57.366 align:left position:27.5% line:83% size:62.5% And this coal forms when that plant material 45:57.366 --> 45:58.966 align:left position:17.5% line:89% size:72.5% is buried within the Earth 45:58.966 --> 46:00.866 align:left position:15% line:83% size:75% and subjected to the Earth's intense heat 46:00.866 --> 46:02.366 align:left position:20% line:89% size:70% and the intense pressure. 46:02.366 --> 46:06.666 align:left position:17.5% line:83% size:72.5% And it forms this midnight black, energy-rich material. 46:08.366 --> 46:11.200 align:left position:17.5% line:83% size:72.5% So coal is very, very rich in carbon, 46:11.200 --> 46:13.633 align:left position:25% line:83% size:65% and it's this period of geological time 46:13.633 --> 46:15.300 align:left position:15% line:83% size:75% which is associated with the deposition 46:15.300 --> 46:17.200 align:left position:15% line:89% size:75% of these thick coal deposits, 46:17.200 --> 46:19.166 align:left position:27.5% line:83% size:62.5% so it's no surprise that this period got its name, 46:19.166 --> 46:22.066 align:left position:12.5% line:83% size:77.5% the Carboniferous, which means coal-bearing or coal-producing. 46:22.066 --> 46:27.200 align:left position:47.5% line:89% size:42.5% ♪ ♪ 46:27.200 --> 46:30.333 align:left position:40% line:77% size:50% NARRATOR: During the 60 million years of the Carboniferous, 46:30.333 --> 46:34.233 align:left position:22.5% line:83% size:67.5% plant life locked away billions of tons 46:34.233 --> 46:39.233 align:left position:40% line:83% size:50% of carbon in the form of coal. 46:39.233 --> 46:40.766 align:left position:40% line:83% size:50% JACKSON: We know that present day, 46:40.766 --> 46:43.666 align:left position:15% line:83% size:75% the burning of coal is having a dramatic impact 46:43.666 --> 46:46.366 align:left position:22.5% line:83% size:67.5% on the Earth's climate, but actually, 46:46.366 --> 46:48.333 align:left position:15% line:83% size:75% the formation of coal back in the Carboniferous 46:48.333 --> 46:51.466 align:left position:32.5% line:83% size:57.5% had an equally as profound effect. 46:53.233 --> 46:56.633 align:left position:40% line:77% size:50% NARRATOR: With so much plant matter locked away underground, 46:56.633 --> 46:59.866 align:left position:37.5% line:83% size:52.5% atmospheric carbon levels dropped. 46:59.866 --> 47:02.400 align:left position:22.5% line:83% size:67.5% And this is why massive sustained coal production 47:02.400 --> 47:06.100 align:left position:22.5% line:83% size:67.5% kicked the whole system out of balance. 47:09.533 --> 47:13.000 align:left position:40% line:83% size:50% NARRATOR: And the impact was dramatic. 47:13.000 --> 47:18.033 align:left position:47.5% line:5% size:42.5% ♪ ♪ 47:21.966 --> 47:23.500 align:left position:22.5% line:89% size:67.5% Over millions of years, 47:23.500 --> 47:27.666 align:left position:22.5% line:83% size:67.5% CO2 levels plummet, and global temperatures nosedive, 47:27.666 --> 47:30.533 align:left position:35% line:83% size:55% in a reverse of the greenhouse effect... 47:32.866 --> 47:34.966 align:left position:32.5% line:89% size:57.5% (wind howling) 47:34.966 --> 47:38.166 align:left position:15% line:89% size:75% ...causing vast icy expanses. 47:42.733 --> 47:44.666 align:left position:30% line:83% size:60% The consequences of carbon hoarding 47:44.666 --> 47:46.833 align:left position:12.5% line:89% size:77.5% by the equatorial swamp forests 47:46.833 --> 47:49.733 align:left position:35% line:83% size:55% leave plants teetering on the edge. 47:53.433 --> 47:57.433 align:left position:25% line:83% size:65% In the frozen south, the forests die off en masse. 48:03.266 --> 48:07.133 align:left position:40% line:77% size:50% SOREGHAN: As carbon dioxide continued to drop, 48:07.133 --> 48:09.466 align:left position:20% line:83% size:70% it would've become very, very cold, 48:09.466 --> 48:12.100 align:left position:17.5% line:83% size:72.5% and up to a quarter of the world's landmasses 48:12.100 --> 48:14.466 align:left position:15% line:89% size:75% would've been covered in ice. 48:16.733 --> 48:18.666 align:left position:40% line:83% size:50% NARRATOR: If this process had continued, 48:18.666 --> 48:21.200 align:left position:37.5% line:83% size:52.5% it would've had dire consequences. 48:23.666 --> 48:26.033 align:left position:12.5% line:83% size:77.5% It could've potentially caused a Snowball Earth, 48:26.033 --> 48:28.200 align:left position:32.5% line:83% size:57.5% or what we call a runaway glaciation, 48:28.200 --> 48:34.466 align:left position:25% line:83% size:65% where ice could have covered the entire planet. 48:36.533 --> 48:39.466 align:left position:40% line:83% size:50% NARRATOR: Which would've set plants back 48:39.466 --> 48:42.366 align:left position:12.5% line:89% size:77.5% hundreds of millions of years. 48:45.100 --> 48:48.333 align:left position:15% line:89% size:75% But that isn't what happens. 48:52.766 --> 48:55.200 align:left position:17.5% line:89% size:72.5% Beneath the frozen surface, 48:55.200 --> 48:57.566 align:left position:20% line:83% size:70% the giant tectonic plates are continuing 48:57.566 --> 49:00.133 align:left position:20% line:89% size:70% their perpetual movement. 49:02.300 --> 49:06.466 align:left position:40% line:77% size:50% SOREGHAN: Over the 60 million years or so of the Carboniferous, 49:06.466 --> 49:09.066 align:left position:32.5% line:83% size:57.5% plate tectonics had been creating 49:09.066 --> 49:11.666 align:left position:25% line:89% size:65% a new supercontinent. 49:11.666 --> 49:13.133 align:left position:15% line:89% size:75% They were zippering together, 49:13.133 --> 49:17.100 align:left position:12.5% line:83% size:77.5% essentially along the Equator, and moving northward. 49:17.100 --> 49:19.066 align:left position:15% line:71% size:75% Mountains were being formed, 49:19.066 --> 49:21.400 align:left position:27.5% line:71% size:62.5% new weather patterns were being altered 49:21.400 --> 49:23.333 align:left position:20% line:71% size:70% and adjusted as a result 49:23.333 --> 49:26.300 align:left position:32.5% line:83% size:57.5% of this change in the landmass on Earth. 49:30.133 --> 49:32.333 align:left position:40% line:83% size:50% NARRATOR: And with this change... 49:32.333 --> 49:35.000 align:left position:47.5% line:89% size:42.5% ♪ ♪ 49:35.000 --> 49:38.566 align:left position:12.5% line:89% size:77.5% ...about 300 million years ago, 49:38.566 --> 49:43.933 align:left position:15% line:83% size:75% most of the swamps dry up and cease their production of coal. 49:45.533 --> 49:47.000 align:left position:40% line:83% size:50% SOREGHAN: When coal formation 49:47.000 --> 49:49.666 align:left position:10% line:89% size:80% essentially ended, it meant that 49:49.666 --> 49:52.300 align:left position:12.5% line:83% size:77.5% we weren't locking away as much carbon dioxide, 49:52.300 --> 49:58.766 align:left position:22.5% line:83% size:67.5% and yet, volcanoes were still belching out CO2, 49:58.766 --> 50:01.300 align:left position:32.5% line:83% size:57.5% but we weren't drawing it down as much. 50:01.300 --> 50:04.166 align:left position:15% line:83% size:75% And therefore carbon dioxide began rising 50:04.166 --> 50:06.366 align:left position:27.5% line:83% size:62.5% in the atmosphere, the Earth began warming... 50:09.000 --> 50:11.333 align:left position:17.5% line:83% size:72.5% ...and the glaciers started melting. 50:11.333 --> 50:15.633 align:left position:47.5% line:89% size:42.5% ♪ ♪ 50:19.066 --> 50:23.166 align:left position:40% line:77% size:50% NARRATOR: The ice sheets recede and eventually disappear. 50:25.100 --> 50:29.766 align:left position:27.5% line:83% size:62.5% This set the stage for a plant renaissance. 50:29.766 --> 50:32.033 align:left position:37.5% line:83% size:52.5% Plant life exploded in diversity, 50:32.033 --> 50:36.366 align:left position:27.5% line:83% size:62.5% leading eventually to the green world we see today. 50:36.366 --> 50:41.966 align:left position:40% line:77% size:50% NARRATOR: Over the following few hundred million years, 50:41.966 --> 50:46.366 align:left position:25% line:83% size:65% plants would overcome one challenge after another, 50:46.366 --> 50:52.466 align:left position:27.5% line:83% size:62.5% developing flowers and fruit, 50:52.466 --> 50:55.233 align:left position:20% line:89% size:70% co-evolving with insects, 50:55.233 --> 50:58.033 align:left position:32.5% line:83% size:57.5% and eventually forming grasses and grains. 50:59.900 --> 51:02.633 align:left position:15% line:71% size:75% Plants transform the land from green 51:02.633 --> 51:05.500 align:left position:17.5% line:71% size:72.5% into every vivid color of the spectrum. 51:05.500 --> 51:07.833 align:left position:47.5% line:89% size:42.5% ♪ ♪ 51:07.833 --> 51:09.600 align:left position:40% line:83% size:50% NARRATOR: Earth's transformation 51:09.600 --> 51:13.466 align:left position:17.5% line:83% size:72.5% from a barren, rocky world to the living planet 51:13.466 --> 51:16.466 align:left position:15% line:89% size:75% we see today is spectacular. 51:18.333 --> 51:22.033 align:left position:27.5% line:83% size:62.5% Rocks breathed life into the land, 51:22.033 --> 51:25.200 align:left position:10% line:83% size:80% but then life altered the rocks, and changed them, 51:25.200 --> 51:28.666 align:left position:10% line:83% size:80% and diversified and enriched our planet in so many ways. 51:28.666 --> 51:31.666 align:left position:15% line:71% size:75% If plants hadn't conquered the land, 51:31.666 --> 51:34.966 align:left position:15% line:71% size:75%   we definitely would not be here today. 51:34.966 --> 51:38.566 align:left position:35% line:77% size:55% BAUMGARTNER: The chair that I am sitting in is from plants. 51:38.566 --> 51:39.966 align:left position:22.5% line:71% size:67.5% The food that you eat, 51:39.966 --> 51:41.500 align:left position:17.5% line:71% size:72.5% the clothes that you wear, 51:41.500 --> 51:43.900 align:left position:27.5% line:71% size:62.5% everything you know 51:43.900 --> 51:45.900 align:left position:25% line:89% size:65% is because of plants. 51:45.900 --> 51:50.700 align:left position:47.5% line:89% size:42.5% ♪ ♪ 51:50.700 --> 51:52.733 align:left position:20% line:71% size:70% So, no matter how we try, 51:52.733 --> 51:54.333 align:left position:20% line:71% size:70% we can't escape the fact 51:54.333 --> 51:56.533 align:left position:15% line:71% size:75% that this is a plant planet. 51:56.533 --> 52:00.733 align:left position:47.5% line:89% size:42.5% ♪ ♪ 52:08.433 --> 52:10.000 align:left position:40% line:5% size:50% NARRATOR: On "NOVA: Ancient Earth"... 52:10.000 --> 52:11.233 align:left position:35% line:5% size:55% PAUL WIGNALL: It's the mother of mass extinctions. 52:11.233 --> 52:12.900 align:left position:12.5% line:5% size:77.5% Something utterly catastrophic. 52:12.900 --> 52:14.200 align:left position:35% line:5% size:55% SURESH SINGH: Much greater than the one 52:14.200 --> 52:15.533 align:left position:27.5% line:5% size:62.5% that ended the age of the dinosaurs. 52:15.533 --> 52:18.066 align:left position:10% line:89% size:80% Now we finally know the culprit. 52:18.066 --> 52:20.400 align:left position:27.5% line:89% size:62.5% (explosion pounds) 52:20.400 --> 52:22.266 align:left position:32.5% line:77% size:57.5% JEFFREY BENCA: We are finally able to piece together clues 52:22.266 --> 52:24.266 align:left position:12.5% line:89% size:77.5% from this ancient crime scene. 52:24.266 --> 52:26.666 align:left position:42.5% line:77% size:47.5% SINGH: We're talking wildfires, acid rain, 52:26.666 --> 52:28.266 align:left position:22.5% line:89% size:67.5% deadly U.V. radiation. 52:28.266 --> 52:30.066 align:left position:22.5% line:89% size:67.5% This was hell on Earth. 52:30.066 --> 52:33.366 align:left position:40% line:83% size:50% NARRATOR: "Inferno" on "NOVA." 52:33.366 --> 52:34.966 align:left position:37.5% line:89% size:52.5% Next time. 52:34.966 --> 52:37.000 align:left position:42.5% line:83% size:47.5% SINGER: ♪ Wish I could go back in time ♪ 52:48.200 --> 52:55.733 align:left position:45% line:89% size:45% ♪ ♪ 52:59.566 --> 53:07.166 align:left position:45% line:89% size:45% ♪ ♪ 53:08.800 --> 53:16.333 align:left position:45% line:89% size:45% ♪ ♪ 53:17.966 --> 53:25.500 align:left position:45% line:89% size:45% ♪ ♪ 53:31.233 --> 53:38.400 align:left position:45% line:89% size:45% ♪ ♪