- 5/16/2025
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00:00Our planet was born in violence and grew with disaster. Four billion years ago, primitive
00:11life may have been drifting in the oceans, but disaster loomed. The seas were lost to
00:18intense heat, yet science tells us life survived. Deep underground, it waited for the oceans
00:28to return. Life's goal is to survive, no matter what. And survive it did, first through
00:43fire, and then through ice, on a miracle planet.
01:06Today, New York is a thriving cosmopolitan city, one of the great cities on Earth. Yet
01:1720,000 years ago, this whole area was covered by vast sheets of ice. Glaciers ground their
01:24way through Central Park. Large rocks that have no right to be here. It's as if they
01:32were dropped erratically by some mythical giant. Before geology was a science, it was
01:38recognized that they were from another place. Some thought they were the debris carried
01:44by the waters of Noah's flood. They were carried by water, but not liquid water. Ice. To the
01:59north, Greenland is still a country of ice. Large rocks locked in glaciers are slowly
02:13transported away from where they were originally formed. Glaciers move very slowly. Their forward
02:24motion can be measured in years, rather than in distance. But when the ice melts, the cargo
02:32it carries is dropped. Geologists call these rocks erratics, or dropstones. For science,
02:47they are important pieces of evidence. They give clues to the evolution of life. Erratics are found
02:58across the globe, and they are proof as to which parts of the Earth were once covered by ice.
03:0420,000 years ago, some parts of the world were locked in ice. In Canada, near Lake Huron,
03:12there is evidence of a far earlier ice age, when the entire globe may have been frozen.
03:17Mike Hailston, a district geologist with Canada's Ministry of Northern Development and Mines,
03:23knows where to find rocks that predate the last ice age by billions of years.
03:29This is the one that I wanted to show you. It's an Archean granite boulder stuck in a rot that's
03:362.4 billion years old. It's a diamictite formed from a glacial action that occurred 2.4 billion
03:44years ago. Throughout the region, there are rocks and gravel sediments that really have no place
03:50in local geology. They are all between 2.2 and 2.4 billion years old. Older rocks are found in
04:03younger strata, as if the Earth has constantly recycled its crust. The rocks have been moved
04:09by continental drift, as well as by glaciers. To try and locate where they originally came from
04:17takes us back into the past. Glacial sediments over 2 billion years old have been found in at
04:24least seven different parts of the globe. Until fairly recently, trying to pinpoint where they
04:32came from has been purely educated guesswork. Namibia in southern Africa is an ancient
04:43landscape carved by wind and erosion. But glacial sediments also show that ice once played a major
04:54role. Now hot and dusty, as well as isolated, it is a hard country to work in. For geologists,
05:02though, it can be a paradise. Dr. Joseph Kirschvink is from the California Institute of Technology.
05:09His specialty is magnetics. The Earth is surrounded by magnetism produced by its own
05:17magnetic field, the way compasses work. Long ago, as they formed on the Earth's surface,
05:23the jagged rocks in this riverbed were molten lava. We are sitting on some lavas that erupted
05:312.2 billion years ago during a time of a very large glaciation. It's very nice because when
05:39the lava is cool, they preserve the direction of the magnetic field, and from that we can measure
05:44the latitude. Molten lava contains many minerals which are magnetized. As the lava flows,
05:56these minerals follow the magnetic force of the Earth. Once it cools, the magnetic direction of
06:07that moment is fixed forever. It is then possible to locate exactly where the rock was formed. To
06:16do this, one matches the magnetic history of the rock with the angle of the lines of
06:21geomagnetic force that surround the planet. Once that has been determined, the latitude can be
06:28fixed. At the center of the screen is the pole. The further away a point is from the center,
06:35the closer it is to the equator. When the samples from Namibia were analyzed,
06:47their magnetic compasses pointed to the fact that they all had originated near
06:51the equatorial regions, closer to the equator than Hawaii and Guam are today.
06:57This confirms that over two billion years ago, there were glaciers near the equator.
07:05To have glaciers there at that latitude implies that it has to be colder as you go north. Hence,
07:17the entire Earth right down to the equator had to have been frozen.
07:21Not once, but twice, for glacial sediments in Strata dated between 800 to 600 million years ago.
07:44From this data, Dr. Kirschvink put forward the proposal that the Earth had been completely
07:49covered in ice at least twice in its history.
08:08It was called the Snowball Earth, and like many scientific theories, this one is hotly debated.
08:20Children always enjoy scrambling around looking for rocks. And there are few better teachers
08:29than Dr. Paul Hoffman of Harvard University. For years now, his passion has been geology,
08:37and he is also a keen advocate for Snowball Earth.
08:40The impact of the snowball events would, of course, be much more severe because organisms
08:48might try to escape towards the tropics. But eventually, in the oceans, the ice will
08:54completely envelop the tropics because this ice is flowing. It will move into the tropics and meet
09:00at the equator. Working with scientists at the University of Tokyo, a computer simulation was
09:13carried out to show what would happen to today's world if a Snowball Earth event were to occur.
09:27At 35 degrees north, Tokyo is just a little further south than New York.
09:34Ice up to 1,000 meters or 3,000 feet thick would bury the city.
09:44At first, any life that could not find shelter would freeze to death.
09:56At the start, the glaciers would move slowly. It would take millions of years for the ice to reach
10:01a latitude where Hawaii and Cuba are. But from there to the equator would take only a few decades.
10:14Paul Hoffman thinks that the sea might freeze down to a depth of over half a mile.
10:36Some life might escape under the ice, but only for a while, for sunlight would be cut off.
10:44And the base of the food chain would die.
10:54It would seem as if the world would become a dead planet.
10:59But life is present on the Earth today, so where could it have taken refuge?
11:04And an even more extensive, and we think very interesting, place where life would have survived
11:10would be in cracks that would always develop because the sea ice is flowing, whereas the ice
11:18that is at the coast would be frozen and locked in place. And therefore there will always be a
11:26shear between the glaciers flowing in the ocean and the landfast ice. And so cracks will continually
11:32open and then freeze and then open and freeze and open and freeze. And there's a very rich biota
11:40that lives in cracks and in channels of salty water that get enclosed within new sea ice.
11:48How a snowball event gets started is still not fully understood.
12:02But strangely it may have something to do with the gases which keep the Earth warm.
12:09Moderate levels of carbon dioxide help to keep the planet warm.
12:15But there is evidence which suggests that prior to the first snowball event
12:20these levels were far lower. If so, what kept the planet warm?
12:28A large area of the Earth's surface is called the crust.
12:32If so, what kept the planet warm?
12:38A large area of wetlands and swamp in the southeast of the United States
12:42can give some clues to the makeup of Earth's early atmosphere.
12:48The Okefenokee National Wildlife Refuge covers an area of 400,000 acres.
12:54The shallow warm water is sometimes only knee-deep.
12:58On the surface the swamp floor is soft and spongy.
13:06Don Berryhill was a science teacher. Now as a volunteer guide
13:10he enjoys sharing both his love for the area as well as his love for science.
13:14See where I'm digging down here? Look what's coming out.
13:18All right, that's a gas that's produced by the bacteria and the fungi down there.
13:24As soon as the bottom of the swamp is disturbed, gas bubbles escape.
13:36It is a highly flammable gas called methane.
13:42This gas is sometimes used in households for cooking
13:46but here it is produced by microbial life called methanogenes.
13:54That's a turtle.
14:00Unlike so much life on the planet today,
14:04methanogenes don't rely on sunlight for energy.
14:08Instead they get their energy by breaking down nutrients
14:12and making methane as a waste gas.
14:24Methane
14:36Scientists believe that methane was the greenhouse gas
14:40which kept the early earth warm.
14:44As methane bubbles to the surface
14:48we now know that climate change is nothing new
14:52This is Dr. Jim Casting of Pennsylvania State University
14:56who is a leading researcher in atmospherics.
15:00His research shows that if there was no carbon dioxide in the atmosphere
15:04methane alone could keep the climate well above the freezing level.
15:08But if you go back prior to the rise of oxygen
15:12around 2.3 billion years ago
15:16then methane levels could have been much higher.
15:20Methane by itself would be enough to counteract the reduced luminosity.
15:32He believes that the atmosphere then
15:36would have appeared reddish because of the high methane levels.
15:50At that time in the planet's existence
15:54there was no life on land, no plants, no animals.
15:58The only life forms were microbial
16:02and lived in the oceans.
16:10Methanogenes belong to a group of microbes known as the archaea
16:14a different branch of the tree
16:18from which the microbes were eventually to evolve to higher life.
16:22They belong to the family Eukarya
16:26and they are the ancestors of life today.
16:30Then a totally new organism emerged into the oceans
16:34perhaps a single cell mutated when reproducing
16:38it's something we'll never know
16:42but these cyanobacteria were to change the world.
16:47Methane was released into energy
16:51and as a by-product produce oxygen
16:55a process known as photosynthesis.
16:59Oxygen was released into the atmosphere in huge quantities
17:03and in those days there was nothing that could use it.
17:07Dr. Casting thinks that it reached a level
17:11when its reaction to methane accelerated
17:15over time the world would change from its reddish color to blue
17:19with nothing to stop it oxygen production
17:23continued unabated for millions of years.
17:27These little microorganisms caused the rise of oxygen
17:31caused the decline of methane
17:35and triggered a global glaciation which may have come close to wiping them out.
17:39Then the sun was smaller than it is today
17:43so with the warm blanket of methane removed
17:47the world began to cool.
17:51There were no other greenhouse gases to warm it
17:55so slowly the planet began to freeze.
18:03Life had kept the planet warm
18:07and now life was bringing chaos and disaster.
18:11What we have learned is that when there is a mass extinction
18:15in the aftermath those organisms
18:19that are quick off the mark and can take advantage
18:23of empty eco-space and seize
18:27those places even if they are not the most advanced
18:31or most suitable organisms if they can get there first
18:35and establish their foothold they can be very difficult to dislodge
18:39and so after each mass extinction there is a new biota
18:43which takes hold and becomes ascendant
18:47for a long period of time perhaps until the next mass extinction.
18:55Scientists believe that if there were snowball events then
18:59they must have persisted for millions of years.
19:03During that time the face of the planet would have seemed a frozen and desolate wasteland
19:07but that's not what the lands of Iceland are today.
19:11There was perhaps a chance that life could survive in water beyond the oceans
19:15living from the heat and energy that comes from the earth itself.
19:19Iceland is known for its volcanic and thermal activity.
19:23The land has only a thin crust above the heated mantle of the planet
19:27it sits very close to awesome power and force.
19:31Hot springs are found across the island
19:35where the heat of the earth forces its way out.
19:41Places like these could have been a safe haven for microorganisms
19:45which like the heat, the thermophiles.
19:49Dr. Viggo Martinsson and his team work for a company
19:53which hopes to use rare microbes for research.
19:57Very steaming coming up from that deep down in the earth.
20:04And it's places like this where thermophiles can live.
20:15Where the water bubbles out it's too hot for just about any living organism.
20:19But cooler edges are full of bacterial life.
20:25Look, this is great. This is all covered with cyanobacteria.
20:29This is rich in all kinds of species.
20:35The life in these pools is made up mainly of bacteria which photosynthesize.
20:43The microbes cluster together to form thick mats.
20:47The earliest evidence of organisms like this
20:51appear before the first snowball event.
20:55Even then the green filaments of cyanobacteria
20:59would have clustered together.
21:03Around them are other microbes able to tolerate high temperatures
21:07living off the nutrients.
21:11Perhaps this was also where our distant ancestors
21:15found shelter from the ice.
21:19The Geraltormer area is a refuge for life.
21:23Life like this where you can find cyanobacteria
21:27or you can also find all different kinds of broad range of diversity
21:31of different kinds of bacteria.
21:35It's a great place to live.
21:39Cyanobacteria.
21:47Maybe the planet needed a disaster like a snowball earth
21:51to let new forms of life take strides forward.
21:57Shortly after the ice melted, life had changed greatly
22:01even if it was still minute.
22:06This is a microorganism known as chonoflagellate.
22:10It's an unusual group of microbes
22:14which cluster together in colonies.
22:18These are the closest known ancestors of animals and us
22:22and for the next billion years life stood still.
22:26There were no further advances.
22:30If we were to compare the earth's history to a single year
22:34then microscopic creatures were life's main force
22:38up until mid-November.
22:44But the second snowball event about 600 million years ago
22:48was to change that forever.
23:00Life's history is painted in its rocks.
23:04This barren wasteland was once the bed of an ancient ocean.
23:14Namibia in southern Africa is mostly a harsh and arid land
23:18but this means that the rocks that lie upon the surface
23:22are relatively undisturbed by water erosion or moved by flooding.
23:30Etched into some of the scattered rocks
23:34are strange shapes and forms.
23:42As well as here on a Namibian farm
23:46similar fossils have been found
23:50in Siberia, Australia and Newfoundland.
23:54On the other side you see the positive outcrops of the same fossil.
23:58Fossils certainly
24:02but fossils of what?
24:10For us as laymen we didn't know what it was.
24:14It could be anything from a fish or a fern.
24:18Actually it looks more like a fish
24:22but then later on even the scientists weren't sure
24:26whether it was a plant or whether it was a living organism.
24:32These fossils date back to the end of the second snowball event
24:36and they were neither fish nor leaf.
24:40They were the first living creatures larger than microbes
24:44to appear on the planet.
24:48These were giant steps forward in evolution.
24:52Scientists think that it may have lived on the sea floor
24:56half buried in the mud.
25:00They have a body shape and form
25:04which resembles nothing living in the modern age.
25:14So too with this strange creature found in Siberia
25:18A stone with five strange fossil marks
25:22is a record of this animal's movements on the sea floor.
25:30This is the first time in the history of the planet
25:34that a living creature moved with direction and purpose.
25:42This one too comes from Siberia
25:46and has been named Kimberella.
25:50It had a snail-shaped body and a strange long protrusion
25:54which allowed it to feed from the sea floor.
25:58The first time that any creature had dug in the mud
26:02releasing nutrients back into the water.
26:16This period after the second snowball earth
26:20is called the Ediacaran
26:24after a range of hills in South Australia
26:28where similar fossils were found.
26:32And somewhere among these creatures was the ancestor for modern life.
26:36It might have been this
26:40a fossil discovered in Australia in 2003.
26:46Some think here is evidence of a backbone
26:50perhaps making this creature the size of an adult's small finger
26:54the predecessor of the vertebrates.
26:58We can only speculate as to how it lived.
27:02After three billion years of life it was amongst the first creatures
27:06which would be visible to the naked eye.
27:10Both snowball events seem to have been crucial for evolution.
27:14The second could not have happened without the first
27:18which saw the rise of organisms like this eukaryote.
27:22Although still tiny it was a thousand times larger
27:26than the early microbes.
27:34The mystery yet to be solved was how the ice melted.
27:38Once a planet like the earth was frozen
27:42it would reflect sunlight back into space and so remain frozen.
27:50What did happen to melt the ice?
27:54A hint can be found in this mine
27:58in the Kalahari region of South Africa.
28:02This is the largest deposit of manganese to be found anywhere in the world.
28:08All the ore was laid down on the bottom of an ocean floor
28:12just when the first snowball event ended.
28:16Dr. Joseph Kirschvink from Caltech
28:20who first published the snowball earth hypothesis
28:24wondered if this deposit was in some way connected to the melting of the ice.
28:28Okay...
28:32Actually...
28:36It's a good solid sample.
28:40All the manganese in this mine were of manganese dioxide
28:44which can only form with oxygen.
28:48Only molecular oxygen, free molecular oxygen like we have in the earth
28:52is able to oxidize the manganese and make it fall out as this black rust.
28:56And what we're standing on today and what you can see here
29:00is the evidence of a massive amount of oxygen
29:04being put into the environment just at this time, just after the snowball.
29:12He believes that the oxygen in the atmosphere of the early earth
29:16was almost non-existent.
29:20After the first snowball event it increased to around 1%.
29:24Today it grows to 20%, close to the level in the atmosphere today.
29:32Oxygen molecules also produce an enormous amount of energy.
29:36And because energy became available
29:40life was able to evolve into larger and more complex forms.
29:54Yet the questions kept coming.
30:02It occurred to me that a frozen surface
30:06would not influence the working of geology.
30:10And it just hit me one morning that oh, of course
30:14the carbon dioxide from volcanoes would continue to build up in the air.
30:24Volcanic gases contain large amounts of carbon dioxide
30:28which normally dissolves into the seawater.
30:36But since the world was covered by ice
30:40the carbon dioxide had nowhere to go but up.
30:44It continued to build to levels
30:48which may have been 2,000 times higher than those of today.
30:54As the earth warmed, the ice began to melt.
31:00You go from an average temperature of going down to minus 50
31:04almost to plus 50.
31:08And at that point you melt the ice extremely rapidly.
31:12It was the earth's own forces
31:16which brought the snowballs to an abrupt and dramatic finish.
31:21It was the earth's own forces
31:25which brought the snowballs to an abrupt and dramatic finish.
31:51One study has suggested that when the surface of the sea
31:55reaches 45 degrees Celsius, about 110 Fahrenheit
31:59it would trigger weather patterns that the world has never seen before or since.
32:21The temperature differentials would cause massive hurricanes to build.
32:35These hyper-hurricanes would generate waves the height of buildings.
32:51These hyper-hurricanes would generate waves the height of buildings.
33:03These hyper-hurricanes would generate waves the height of buildings.
33:08All this activity boosts oxygen production.
33:12Normally, nutrients which dent into the sea
33:16are released by the sea water.
33:20But the sea water is a very powerful source of oxygen.
33:24It's a very powerful source of oxygen.
33:28It's a very powerful source of oxygen.
33:32It's a very powerful source of oxygen.
33:37The nutrients which dent into the oceans from the earth
33:41would settle back to the bottom or be consumed by bacterial life.
33:47In deep water, microbes aren't harmed by a surging ocean from the hyper-hurricanes.
33:51Many are transported from the depths to shallow waters.
34:01Then when the winds died and the ocean calmed,
34:06with sunlight and nutrients,
34:10photosynthetic microbes would explode in numbers,
34:14releasing yet more oxygen.
34:18The algal bloom would be so great that the seas would turn green.
34:22More and yet more oxygen would be pumped into the environment.
34:30The strength of life which had survived two snowball earth periods
34:35was about to embark on a new chapter,
34:39but this time with abundant oxygen.
34:47Oxygen was the molecule that would change the world.
34:52If earth had never experienced these glaciations,
34:56life could have been quite different.
35:00Life on earth might still be limited to the bacterial grade.
35:04We could still be just a planet of slimy oceans and stromatolites
35:08with nothing big enough to move and do things.
35:13And oxygen allowed one more innovation without which larger animals could not exist.
35:17That was collagen, the scaffold which cells use to bind together.
35:25In this experiment in Japan,
35:29synthetic collagen is mixed with cells in a colorant.
35:34These cells with collagen on the left of the screen
35:38multiply vigorously while those on the right are static.
35:44Cells begin to cluster together as they bind together.
35:48This is what we call a synthetic collagen.
35:52It's a mixture of collagen and collagen.
35:56It's a mixture of collagen and collagen.
36:00Cells begin to cluster together as they must in every large living creature.
36:06Vitamin C was added to create an environment
36:10in which it would be easier for cells to secrete collagen.
36:14A thin tissue-like skin has formed in the dish.
36:18Collagen is a unique material which is produced by all animals, including humans.
36:24It helps cells to shape tissue.
36:29As collagen multiplies, it assembles collagen
36:33that it has secreted into a fine net-like structure.
36:39As the cells divide and multiply over and over,
36:43the collagen allows them to create different shapes and tissues.
36:53Dr. Kenneth Tao of the Smithsonian Institute
36:58found that collagen was shaped to life after the second snowball earth.
37:06And since collagen is made from many atoms of oxygen,
37:10it could never have been produced if atmospheric oxygen had not been present.
37:18After the first snowball event,
37:22it's thought that collagen might have been available
37:27but then most of it was used for respiration.
37:31After the second event, oxygen rose dramatically.
37:39When oxygen rose at that period of time,
37:43the body plans could be developed differently
37:47and larger sheet-like forms of animals could develop
37:51using more collagen, stronger collagen.
37:57The trillions of cells which make a human body
38:01are bound together by collagen.
38:13And without collagen and without oxygen,
38:17we would not be here today.
38:22After the first snowball event, there was little change in life.
38:38After the second, oxygen levels soared
38:42and the first complex life appeared,
38:46expanding horizons and leading to higher and yet more complex life.
38:52These strange creatures
38:56which evolved from the snowball events
39:00would not last long.
39:04They would die.
39:08They would die.
39:12They would die.
39:16They would die.
39:21But they did not last long.
39:25Just a few tens of millions of years
39:29before a new life force took over.
39:37Now life could never step backwards
39:41and it was in shallow seas around a vanished continent
39:45where the next step would be taken.
39:50The fossil evidence shows a rich environment of corals and fish and other marine creatures.
40:04Corals need warmth and sunlight, and there would have been an abundance of both.
40:10At this time in the Earth's history, we think that our closest ancestor was this fish, called
40:16Arandaspis.
40:22It's the oldest known fish with a backbone.
40:25Without fins, it would not have been a good swimmer.
40:40They would have been filter feeders, sucking up microbes from the coral on the seafloor.
40:48As yet no animal had developed a jaw, so probably the deep waters were not a suitable niche
40:53for them to live on, but that would change.
41:07There was a rich variety of life.
41:10Amongst it were numerous trilobites, small segmented and hard-shelled creatures.
41:15Some were free swimmers, while others crawled along the seafloor.
41:23When the change came, these creatures left clues, which were picked up by an English
41:28paleontologist.
41:36This quarry in Shropshire, in the west of England, was once near the equator and a part
41:40of the Iaptus Sea, an ancient sea which vanished some 400 million years ago.
41:49Marine fossils, and trilobites in particular, are Dr. Richard Forty's driving passion.
41:56Oh, lovely.
41:58Look at this one.
42:01It's a chain coral.
42:09The abundance of fossils in the coral record suddenly vanish, a sure sign that something
42:13drastic happened to this environment.
42:32There were other noticeable changes to life as well.
42:50Trilobites began to alter their appearance.
42:52Some began to grow protective armor.
43:16It's almost certain that they were a response, a defensive response, to being under greater
43:22pressure from a variety of predators.
43:25Life, in other words, got a little bit tougher for the trilobites, and one of their responses
43:33was to increase their protective armor.
43:39Life undertook a new development in body shape.
43:42Only in the fossil record we find fish like this, sleek, fast predators.
43:51The world began to be divided into predator and prey.
44:00It was the start of the arms race on the Miracle Planet.
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