Goddess of the Earth
Gaia, the Greek word for Earth goddess, also is the name of the controversial hypothesis that life on Earth controls the environment. NOVA explores this provocative theory that challenges conventional ways of thinking about the Earth.
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00:37July 1976.
00:40The planet Mars was being approached by a spacecraft from Earth.
00:43NASA had sent it there to look for life.
00:46But in a strange way, this project was to lead to a very controversial idea
00:50about the nature of life back on Earth.
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00:56The possibility of life on Mars had intrigued human beings for centuries.
01:00NASA itself had made a film about some of the latest weird ideas.
01:05On Mars, deadly ultraviolet radiation from the sun penetrates to the surface.
01:11Life forms on Mars may have silica shells to protect them against this radiation.
01:17We know that Mars is very dry.
01:19Life forms on Mars may have developed special ways of preserving their water content.
01:26There may be a kind of plant, an ice eater, with fine root-like probes,
01:31searching not for liquid water, but searching the permafrost,
01:36reaching down to get at that ice.
01:40The plan was for the spacecraft to drop part of itself down through the atmosphere
01:44to land on the surface of the planet.
01:47Back on Earth, scientists were waiting to see what would happen.
01:51One of them was a Briton called Dr. Jim Lovelock.
01:54I kept getting puzzled. Why were they sending these complicated experiments to Mars
01:59when it should be possible to determine whether there was life on that
02:03or any other planet come to that without ever going there at all?
02:08Nevertheless, the plan went ahead.
02:10The lander was lowered to the surface and sent back the first pictures.
02:16Everything had worked perfectly.
02:28On Mars, the lander had quickly set about its task.
02:36It collected samples of the Martian soil with a specially designed scoop
02:40and then tested them for signs of life.
02:43The conclusion was that Mars was in fact completely lifeless,
02:48and this confirmed what I had personally concluded ten years earlier.
02:58Jim Lovelock now works as a freelance scientist and inventor.
03:01His laboratory is attached to the cottage where he lives on the borders of Devon and Cornwall.
03:06It's surrounded by a few acres of land and the family's pet peacocks.
03:1325 years ago, Jim Lovelock developed an instrument known as an electron capture detector.
03:19It's still the most sensitive means of testing for minute amounts of gas in the atmosphere.
03:24His reputation as an outstanding scientist has been recognised by the Royal Society,
03:29of which he's been a fellow for the last decade.
03:32It's one of many honours he's been awarded in a long and distinguished career.
03:37Some of these are from NASA, where he worked for many years.
03:41It was while he was planning how to detect life on Mars
03:44that an important idea occurred to him which would challenge our view of life on Earth.
03:49It seemed to me, and I said to them, it shouldn't be necessary to go to a planet like Mars,
03:55or indeed any other planet, to find life.
03:57You can get enough information from telescopes to tell you whether there's life there or not.
04:03Their reaction was largely one of bafflement.
04:05They couldn't see what I was getting at, and they asked me to explain more.
04:10His idea about using a telescope was not to look for so-called Martian canals
04:15or any other artefact of that kind.
04:17Instead, it was to study the light that's being reflected from the surface.
04:23As every schoolchild knows, when white light is passed through a simple prism, you get a spectrum.
04:28Take the light from Mars.
04:30Do this with much more sophisticated apparatus,
04:33and parts of the spectrum will change depending on which gases make up the Martian atmosphere.
04:39And that's the clue.
04:40Because according to Jim Lovelock, the gases will tell you whether there is life there.
04:45Well, you see, if you have life on the planet,
04:47it's bound to use any of the mobile media that are available to it,
04:52like the atmosphere or the oceans,
04:54as a source of raw materials,
04:56and also as a conveyor belt for getting rid of waste products and so on.
05:00And such a use of the atmosphere,
05:02and there wasn't an ocean on Mars, there was only an atmosphere,
05:05would be bound to change its chemical composition
05:08away from that of a lifeless planet.
05:10And this should be easily recognisable.
05:14Mars, Venus and our own planet Earth
05:18reveal rather interesting differences
05:20when compared in this way.
05:22A collaborator of Jim Lovelock in this work is Professor Lynn Margulis.
05:26The most impressive thing is when you compare the Earth with neighbouring planets.
05:29You compare them with Mars on one side and Venus on the other.
05:34And in fact, it's been called humorously the Goldilocks problem.
05:37Mars is too cold and Venus is too hot, and the Earth is just right.
05:41If you do that comparison, you find something absolutely remarkable.
05:44Venus and Mars both have about 90% the same temperature.
05:48Venus and Mars both have about 98% carbon dioxide in their atmosphere,
05:53CO2 in their atmosphere, very high quantities,
05:56and they have about 2% nitrogen and they have trace amounts of oxygen.
06:00So they're in some ways very similar.
06:02Their temperatures are very different, but in those ways they're very similar.
06:05And you look at the Earth, and the Earth is bizarre.
06:07It has virtually no carbon dioxide, 0.03%.
06:11In fact, the big argument is between 0.0322 and 0.0321, it's in there.
06:17The big argument about the big CO2 atmosphere.
06:20And the Earth also has much too much oxygen, and oxygen is explosive.
06:24Everybody knows it exploded and destroyed the Apollo astronauts.
06:28Now you look at this. Why is the Earth, nitrogen and oxygen,
06:31an explosive mixture, and virtually no CO2?
06:36The oxygen comes from the plant life on Earth.
06:39Another gas that reacts with it is methane.
06:42This comes from bacteria living in swamps,
06:45and from animals, or to be more precise, from the bacteria living in their guts.
06:52It's the presence of these sorts of gases, produced by living organisms,
06:56that make our atmosphere so different from that of Mars and Venus.
07:01First of all, this was proof that there was life on Earth, if you needed it.
07:06Something that NASA wasn't really looking for.
07:09Indeed, they were very worried that somebody might find
07:12that somebody had been spending money that they had produced
07:15to prove that there was life on Earth.
07:17That would not have gone down at all well politically.
07:20But there was something else besides a strange mix of gases.
07:23It suddenly dawned on me that more remarkably even
07:27than this strange, potentially explosive atmosphere that we had,
07:30was the fact that it remained constant like that over geological periods of time.
07:36And this is an event as unlikely as riding on a bicycle,
07:41unscathed through rush hour traffic.
07:43It's something totally impossible, and it required the presence
07:47of some means of regulating some sort of automatic system
07:51that would keep this constancy.
07:53To account for this, Jim Lovelock put forward the controversial idea
07:57that life itself was responsible for this stability.
08:01On Earth, he suggested, there was a huge global system
08:04that was self-regulating, in the sense that life was part of it.
08:08And life interacted powerfully with the environment,
08:12in such a way that conditions on Earth remained constantly fit for its survival.
08:19In the late 1960s and early 70s, these ideas were buzzing around in my head.
08:24And I was very lucky, for at that time I lived in a village in Wiltshire,
08:29and had as a near neighbour the novelist William Golding.
08:32And he was very sympathetic of the idea of this giant system.
08:35We used to talk about it during walks around the village.
08:38And he said, you know, if you're going to put forward the idea
08:42of a powerful system like that, you'd better give it a good name.
08:47And he said, I suggest that you call it Gaia,
08:51the name that the Greeks used for the Earth's goddess.
08:54The Gaia hypothesis.
08:56The notion that life controlled the environment
08:59proved to be controversial to many scientists.
09:02The conventional wisdom held by geologists
09:05was that life was a kind of passenger on the Earth.
09:08It did a few things, like it made oxygen from plants and animals,
09:13ate the plants and returned it.
09:15But it just turned things round and round.
09:17It didn't do anything particular.
09:19It was a passenger on the spaceship Earth, if you like.
09:22In the same way, the biologist assumed that the Earth's environment
09:26was something that was driven by ineluctable physical forces
09:31and life had nothing to do with the evolution of the planet.
09:35Now, the Gaia notion is quite different.
09:39It sees those two processes, that's to say the evolution of life
09:43and the evolution of the planet, as not two processes
09:46but one single tightly coupled process.
09:49The most compelling evidence, he believes,
09:51is not just the constancy of gases but the constancy of temperature.
09:55The average temperature of the planet
09:57has never dropped below 5 degrees Celsius
10:00or exceeded 25 degrees Celsius.
10:03Since life began over 3 billion years ago,
10:06the oceans have never completely frozen solid
10:08nor have they boiled dry.
10:11Now, this is in great contrast to the experience
10:14of our sister planets, Mars and Venus.
10:17The day-to-night time temperature range on Mars
10:22can be as great as from a warm summer's day here in Britain
10:27to something like minus 100 degrees Celsius at night.
10:31As big a range as that,
10:33something that would be quite impossible for life as we know it.
10:40This is despite the fact that the Sun, like all stars,
10:43is gradually getting hotter.
10:47Since life began 3.5 billion years ago,
10:50the Sun's internal processes have stepped up its heat production
10:54by about 30%.
10:56One would expect that we shouldn't be far short of boiling now.
10:59And as you know, we're not.
11:01Or conversely, if it's right and comfortable now,
11:04then the Earth should have been a frozen ball of ice
11:07when life began.
11:09Well, clearly it wasn't.
11:11And some explanation is needed
11:13for accounting for the constancy
11:16in spite of this big change in solar output.
11:20It is hard to believe, from an astronomical point of view,
11:24that the temperature is simply by accident maintained constant.
11:28We prefer to believe
11:30that there's an active temperature regulating system.
11:33And when we look around,
11:35we see that it is really the sum of the organisms and their activities
11:40that have the potential for regulating the temperature.
11:43Organisms produce gases that can absorb radiation.
11:46They change surface temperatures.
11:48They produce clouds by producing lots of water that make clouds
11:52that change surfaces from dark to white, and so on.
11:56And we see lots of potential for the organisms to regulate temperature,
12:00and we believe, actually,
12:02that temperature is also part of the Gaian regulation system.
12:05For example, during the day,
12:07a tropical forest stimulates the formation of clouds.
12:10This keeps it moist but also helps to cool it
12:13as the white clouds reflect the sun's heat back and out into space.
12:30However, this is a short-term process.
12:32The planet needs another regulatory system
12:35to compensate for that warming sun.
12:38It goes back to when the planet Earth first formed
12:41four and a half billion years ago.
12:44At that time, the atmosphere owed a lot to the activity of volcanoes.
12:58The gases pouring out of those red-hot vents
13:01included carbon dioxide and water vapor.
13:04As the Earth cooled, the water vapor eventually condensed,
13:07fell as rain, and formed the early oceans.
13:11It was here that life began.
13:13But with a weak sun, the temperatures might have been freezing
13:16were it not for the carbon dioxide.
13:19This might have made up to a third or more of the Earth's atmosphere.
13:22CO2 is a gas that traps heat,
13:25a greenhouse gas that would have served the useful purpose
13:28of retaining the heat from that weak sun,
13:30making sure temperatures were warm enough for life to begin.
13:36But later, as the sun became warmer,
13:39the planet needed a thinner blanket of carbon dioxide.
13:42This would allow some of the increased heat to escape,
13:45ensuring conditions did not become too hot for life.
13:48All very neat and convenient.
13:50But what reduced the carbon dioxide?
13:56Life did, according to Jim Lovelock.
13:59He started doing it in the sea over 3 billion years ago,
14:02and it's still at it today.
14:04May the 17th, 1980.
14:07The north of Scotland, viewed from a satellite in space.
14:10Nothing remarkable, but on a slightly different wavelength there is.
14:14Just northwest of Stornoway, there's something rather strange in the sea.
14:18A vast white shape.
14:21On the 29th of May, the same thing again.
14:24Land's end, and the western approaches to the English Channel.
14:27Nothing remarkable, until the wavelength is changed.
14:30Then, the same white shape.
14:32This, Lovelock believes, is what is pumping or sucking down the carbon dioxide.
14:37The research ship Squillar belongs to the Marine Biological Association,
14:41the MBA at Plymouth.
14:43It's on its way to trap whatever caused that white shape.
14:47In this case, it's in the English Channel.
14:50One of the scientists is preparing equipment to sample water at different depths.
14:58The plunger will seal the container.
15:04The sample of water trapped inside is then taken back to the MBA,
15:08filtered, and the residue examined with an electron microscope.
15:12The sample of water trapped inside is then taken back to the MBA,
15:16filtered, and the residue examined with an electron microscope.
15:32It's called a coccolithophore, and it's about two hundredths of a millimetre across.
15:37Put billions of them together, and they make up those strange white shapes in the sea.
15:42In this case, between Norway and Denmark, emerging from the Skagerrak.
15:49Their shells are made of calcium carbonate.
15:52The carbonate came from the carbon dioxide in the atmosphere.
15:57When they die, they sink and form sediments on the bottom of the sea.
16:02Occasionally, geological movements push these up to form familiar structures,
16:06such as the White Cliffs of Dover.
16:08These cliffs are an ancient burial ground for carbon dioxide.
16:16Plants also can suck down carbon dioxide from the atmosphere.
16:20When a tree grows, it sinks its roots deep into the soil.
16:25To build itself, it uses carbon, and when it dies,
16:28bacteria oxidise this carbon back to carbon dioxide, returning it to the atmosphere.
16:34But underground, something else happens.
16:37Here, the tree roots decay, releasing carbon dioxide,
16:41but this dissolves in the moisture, forming a weak acid,
16:44changing the silicate particles in the clay to bicarbonate.
16:49Rainwater washes this through into streams, and eventually into the sea,
16:53where it's used by the coccolithophores to make their shells.
16:58The power of this CO2 pumping process can be seen each year at the greening of the planet.
17:04This is imagery from a space satellite.
17:06The tropical forests of Africa are clearly visible as a green area.
17:10But it's April, 1982, and what is perhaps more striking
17:14is what is about to happen to the northern latitudes as summer begins.
17:18We are about to watch the whole year in about 20 seconds.
17:34By concentrating on Asia and slowing the movement down,
17:38it's possible to watch the step-by-step progression of the growth of vegetation northwards
17:43through summer, until by July, even Siberia is green.
17:56This is followed by the retreat during autumn to India,
18:00This is followed by the retreat during autumn to India and Southeast Asia.
18:15Carbon dioxide is measured at a number of locations around the world.
18:20The levels of this gas over Alaska have been plotted as the vegetation moved through North America.
18:25As it stands in April, the CO2 level is high, but it starts to drop as the greening moves north.
18:34By August, it has been sucked down to a minimum by these plants.
18:37As they disappear with the onset of autumn, it starts to climb again,
18:41reaching a maximum in the early months of the year.
18:44Such is the power of plants to remove carbon dioxide.
18:48But in doing so, those plants are producing another gas as a by-product,
18:52a gas so potentially dangerous that if it weren't controlled, it would destroy the plants and everything else.
19:03The gas those plants make is oxygen.
19:06If it rises too high, then no rainstorm on Earth would put out the fires produced by a lightning strike.
19:12The evidence for the constancy of oxygen is quite interesting.
19:16In the fossil record, in the sediments, for about two or three hundred million years back,
19:22you invariably find layers of charcoal.
19:25Now, the presence of charcoal is a kind of fossil record of ancient fires.
19:31Now, this tells us quite clearly the limits of the range for oxygen in the atmosphere.
19:38If you have less than 15% of oxygen, you can't light a fire.
19:43Things won't burn, so there couldn't have been any charcoal if it had been less than 15%.
19:48If you have much more than 25% of oxygen, and that's not much more than there is now of 21%,
19:55fires burn so fiercely and so vigorously that it wouldn't be possible to sustain the growth of a forest.
20:02So, above 25%, you couldn't have charcoal either.
20:05So, we're pretty sure that over the last 200 million years or so,
20:09oxygen has been held precisely and accurately at something in its present level.
20:15Certainly not below 15%, certainly not above 25%.
20:19A simple demonstration proves the point.
20:21A battery is used to ignite a match head in an atmosphere of less than 15% oxygen.
20:27The flame can't be sustained, and the match soon goes out.
20:30But, when the oxygen level is increased to 25%, the match ignites quickly and burns to a cinder.
20:39The question arises, what holds the oxygen level at 21% so precisely?
20:45The answer that you're driven to is that you must have an active regulating system,
20:50and that's what Lovelock means by Gaia.
20:52You have an active regulating system. What does that mean?
20:54It means that as oxygen goes too high, there are various factors that affect it.
20:59As it goes too high, there are various mechanisms that lower it.
21:01And as it goes too low, there are various mechanisms that produce it.
21:05All that vegetation on the planet makes oxygen,
21:08and the animal life on Earth consumes it, making carbon dioxide.
21:12But that isn't enough to balance the system.
21:15According to Jim Lovelock, the animals don't consume all the oxygen the plants make.
21:20He believes something else is needed, and it's to be found in the guts of animals.
21:25Dr. Pat Zimmerman has been working on this.
21:44These are termites.
21:46Amongst other things, they eat wood, and they do it with the aid of bacteria in their guts.
21:52In the process, these microbes make the gas methane,
21:55sometimes stored in little sacks within their bodies.
21:58We got interested in methane emissions from termites
22:01because we saw them everywhere we went to do research.
22:04We saw them in the tropics, in trees, everywhere it's been cleared.
22:08And when we looked into the literature,
22:10we found that termites occur over about two-thirds of the Earth's land surface,
22:14and that there may be as many as three-quarters of a ton of termites for every person in the world.
22:20Even if just a small portion of what they ate was converted into methane,
22:24it would have the potential to have an impact on the chemistry of the atmosphere.
22:29It turns out that about one percent of the carbon that a termite ingests is re-emitted as methane.
22:35It's a slightly lower percentage than that for cattle.
22:38Cattle are five to six percent.
22:40But there are enough termites, and they eat enough material.
22:44They eat an amount of material equivalent to about a third of the net primary productivity of the Earth.
22:52That is that all of the carbon that's fixed by plants in a year, termites would eat about a third of that.
22:58And so they may produce as much as half of the methane that gets into the atmosphere.
23:03Once in the atmosphere, according to Lovelock,
23:06that methane interacts with the excess oxygen to destroy it.
23:11And he believes this is the most important mechanism involved.
23:14What's more, termites are not the only animals to carry these bugs in their guts.
23:19They're to be found even in our guts.
23:21Indeed, my friend and colleague Lynn Margulis often kind of humbles us by saying
23:27that perhaps you could think of the purpose of humans on Earth
23:31as to act as convenient incubators for the three pounds of these respectable ancient bacteria
23:37that we carry around in our guts, producing methane.
23:41We have seen a phenomenon, namely the regulation of temperature,
23:44the regulation of gas composition of the lower atmosphere.
23:48We have seen that it's directly involved with surface life.
23:52Since we have not discovered or worked out all the mechanistic details,
23:57and I certainly agree we are nowhere near having finished that job,
24:01people say, I don't believe it, you don't have a mechanism,
24:04therefore the phenomenon of regulation doesn't exist.
24:07Those people will be biting their tongues another decade or so.
24:11Some scientists, like Dr. Zimmerman, have come to find the Gaia hypothesis useful.
24:16Others reject it completely.
24:18From the beginning, it's been controversial.
24:21The idea that the planet acts as a self-regulating organism was received
24:25when Lovelock first published it with less than total enthusiasm.
24:29It felt like a lead balloon.
24:32It wasn't that there was any criticism.
24:34In fact, there was an astonishing absence of criticism.
24:37It was just a kind of no-reaction response.
24:41And this isn't altogether surprising,
24:43for scientists nowadays do tend to be tethered into their disciplines.
24:49The chemist doesn't want to know too much about biology or physics and vice versa.
24:54And this is a very interdisciplinary topic.
24:57The only people, really, who would be sympathetic and understand such a system as Gaia
25:02are physiologists and engineers, both of whom work with automatic control systems.
25:08However, Lovelock's book about the Gaia hypothesis
25:11did attract interest outside the scientific community.
25:14The Bishop of Birmingham.
25:15The first time, when I read a review, I thought, how extraordinary.
25:18This is contrary to all that I'd read in my amateur status as a scientist.
25:22So I wanted to find out.
25:24I'm always rather interested in the unorthodox,
25:26and I wanted to find out about his reputability.
25:30And then, when I discovered, indeed, he was very reputable,
25:33fellow of the Royal Society and the rest of it,
25:35I thought, how extraordinary this chimes in
25:39with the kind of thesis which I'd been pursuing in a book which was just written.
25:44And it struck me in two ways to chime in.
25:50In the first way, it made me think of what theologians call the imminence of God.
25:55That is to say, the Holy Spirit of God working within creation.
25:59And the way in which the cybernetic controls set up
26:03and make life optimal for human beings to appear
26:07in so many different ways, which he describes,
26:10that immediately put me in mind of the Holy Spirit working within creation.
26:16And so that really was the... that was the first thing that struck me.
26:21And then, secondly, I thought to myself,
26:24how improbable that these should be random cybernetic devices,
26:30if it's what he said, these fine-tuning devices and so on.
26:33And this very much chimed in with my thesis,
26:35because I don't believe that the whole evolution,
26:39right from the very beginning to the appearance of Homo sapiens,
26:42is purely random.
26:44One of the great surprises I had was that for every letter I received
26:48from a scientist after publishing the book on Gaia,
26:51I received two letters from people interested in the religious aspects of this problem.
26:57This surprised me very much, because I hadn't thought that I'd written a religious book.
27:03But I'm beginning to understand now that, of course,
27:07one of the bases, perhaps, of many religions
27:10is a kind of instinctive feeling that there is more to the earth
27:14than just a pile of rocks that we happen to inhabit
27:17and that we may be part of an interactive system.
27:20And it's nice to think, although this isn't scientific,
27:23this is the metaphor, if you like, of Gaia,
27:26that we are part of a great big entity, Gaia, that is regulating our planet.
27:36A general interest in these matters is not restricted to clergymen.
27:40March 1969 and Apollo 9 lifts off.
27:43Once in space, astronaut Rusty Schweickart prepares to clamber out of the command module.
27:48Well, shortly after I stepped out, which was sunrise over the Pacific Ocean,
27:52I had a couple of things to do,
27:54including maneuvering on the outside of the lunar module on the handrails.
27:58And Dave Scott, over in the command module, had to photograph those movements.
28:03And as luck would have it, the camera failed,
28:07and Dave asked for five minutes to try and repair the camera.
28:10It was a wonderful thing, because I found myself outside a spacecraft,
28:15200 miles above the earth, looking down at this incredibly beautiful sight.
28:20Moments like that, it's similar to things that have happened to people since time immemorial,
28:27looking at the stars at night.
28:29You tend to ask yourself, who am I? What is this all about?
28:34How did I get here?
28:36And so that was a unique opportunity for five minutes,
28:40to simply let all of that come in, the beauty of it, in this amazing place.
28:46And, of course, that experience then changed my life.
28:54As a result, Schweickart became deeply interested in the ecology of the planet
28:59and also in ideas about Gaia.
29:01The concept embodied within Gaia creates or evokes a different type of relationship.
29:10We're no longer dealing with the planetary whole conceptually as a thing,
29:17but rather as, in some sense, a living entity.
29:21And our relationship with life is different from our relationship with inanimate objects.
29:32Schweickart has spent many years thinking about just what he means by the phrase,
29:36the planet is a living entity.
29:39But many others who read Jim Lovelock's book may be expecting too much,
29:43or so believes an Oxford biologist, Dr. Richard Dawkins.
29:47I read a book review which excited me rather,
29:50because it seemed to be suggesting that what Lovelock was saying
29:53was that the whole world was a single living organism,
29:57which, if true, would indeed, of course, be a very exciting idea,
30:00the kind of idea that appeals to me.
30:02But I was, immediately I had misgivings,
30:04because it sounded to me exactly like the kind of thing that I'd been fighting against for years.
30:12Dawkins believes it's a misleading analogy to confuse the mechanisms of a living organism,
30:17such as an insect, with that of the Gaia system.
30:21If there is a system there, it's very different from the sort of system that we see in a body,
30:26like a human body, or a cat's body, or a bee's body.
30:30The body of an organism is the end product of thousands, millions of generations of natural selection,
30:37and in each of those generations, the fittest have survived and passed on their attributes.
30:42The result of this is that the machinery of a living body is immensely complicated,
30:46it regulates itself in very complicated ways,
30:49it takes action, finely tuned, sensitive action, to preserve itself and to preserve its offspring.
30:56The danger, it's not exactly distressing or disturbing, except for an academic biologist who values the truth,
31:01the danger is that they will say things like,
31:05the function of oxygen is to do so and so,
31:09the function of ammonia is, the function of methane is,
31:12and where is is followed by some regulatory purpose, something for the good of the biosphere.
31:18Don't get me wrong, I'm not saying that I'm objecting to that kind of purposeful language.
31:23At the level of the individual organism, I'm quite happy to say,
31:26the function of a bird's wing is to keep the bird up,
31:29the function of a bird's eye is to form a well-focused image, and so on.
31:33I'm quite happy with that kind of purposeful language,
31:35because that's at the right level in the hierarchy of life.
31:38What I'm not happy about is to talk about the function of a particular gas in the regulation of the biosphere,
31:45because it implies that individual organisms that are manufacturing that gas are doing it for the good of the biosphere.
31:52It further implies that if it were bad for them as individuals, they might still do it,
31:57because that's the only way the biosphere will persist.
32:00And the real danger is that people will think, will assume,
32:03that individual organisms will sacrifice themselves for the benefit of the entire system.
32:08And that's wrong, and it's dangerously wrong,
32:11in the sense that it's very, very widely believed among laymen and even among professionals.
32:16In addition, Richard Dawkins would maintain that living organisms can optimise conditions to enhance their survival,
32:23but life in the form of the Gaia system cannot.
32:26It has no planning, no foresight.
32:28Did Jim Lovelock perhaps overstate his case?
32:31In the early days, when it was a bit poetic,
32:33one kind of thought of life as optimising conditions on the earth for its survival.
32:39Now that I understand the theory behind Gaia very much more than I did then,
32:44I recognise that this is not so, that it's nothing as highly contrived or complicated as that.
32:53There's no foresight or planning involved on the part of life in regulating the planet.
32:58It's just a kind of automatic process.
33:02According to Lovelock, an example of this lack of foresight occurred 2,000 million years ago.
33:08This primeval world looked very different from ours.
33:11There were no trees, no grass, no fish or land animals,
33:14just bacteria and an atmosphere that would have stunk like a cesspool.
33:19Then, suddenly, 2 billion years ago,
33:21one of the major events in the history of life on earth took place.
33:25Most of it was poison to death.
33:27The poisoners were these.
33:29They're known as stromatolites.
33:32Some of these fossilised remains are vast.
33:37Their descendants are still around today.
33:40Behind this popular bathing beach near Cape Cod in Massachusetts,
33:44the shelter of the sand dunes has produced a salt marsh.
33:49Here, descendants of these ancient poisoners are revealed by anyone walking on it.
33:54The evidence is in the footprint.
33:56With each step, the sand is compressed,
33:58revealing what's lurking just beneath the surface.
34:02They're green and quickly crawl out of sight.
34:05They're bacteria.
34:07Elsewhere, they've formed mats that are more obvious.
34:10In parts of the world, they've clustered together to form small stromatolites.
34:16The key factor is that these mats of bacteria emit a gas,
34:20and that was the poison that did the damage 2 billion years ago.
34:24Cut into a dry section of a mat and multicoloured layers are revealed.
34:29Dr. John Stoltz.
34:31These layers represent different types of bacteria.
34:35The bottom layer there is predominated by organisms that produce hydrogen sulphide.
34:41And then this pink layer is dominated by organisms which use this sulphide.
34:47But what's really interesting is this top green layer,
34:50which is inhabited by cyanobacteria.
34:53Cyanobacteria produce oxygen.
34:56Cyanobacteria produce oxygen.
34:58And 2 billion years ago, they were the ones, the organisms,
35:01that were responsible for the change in the composition of the Earth's atmosphere.
35:06Cyanobacteria, or blue-green algae,
35:08started pouring oxygen into the primeval atmosphere.
35:12As a result, it became more like today's,
35:15but with devastating results for the existing life of that time.
35:19This was probably the greatest air pollution disaster this planet has ever known.
35:24Quite suddenly, a deadly poisonous gas, oxygen,
35:27appeared in its free state in the atmosphere.
35:30Oxygen is sudden death to anaerobic microorganisms.
35:35Many critics argue that this poisoning is evidence that the Gaia system doesn't exist.
35:40Where's the self-regulation, they argue, that's supposed to maintain life?
35:44Gaia would seem to be irresponsible, to say the least.
35:48How can anything which has no capacity whatever for foresight and planning be irresponsible?
35:53It's just doing its thing.
35:55It's in the nature of living things to do their thing.
35:59When we go away for a weekend,
36:01it's no use us leaving a pile of grain for our peacocks to ration themselves with over the weekend.
36:07They won't divide it up into four neat piles and say,
36:10we'll eat this on Saturday and that one on Sunday.
36:12They just eat the lot and get indigestion.
36:14We do it, so why shouldn't Gaia do it? It's very biological.
36:19In other words, Jim Lovelock believes that two billion years ago,
36:22Gaia had a hiccup, but recovered.
36:25Others, however, question whether such a system can be self-regulating.
36:32Dr. Stephen Schneider is one of those.
36:34He is a scientist at the National Center for Atmospheric Research at Boulder, Colorado.
36:39The issue of self-regulation itself is, to me, not yet proved,
36:43although a very, very interesting idea.
36:46For example, how do you define self?
36:49Life is not a single entity.
36:51It's many, many, many millions of entities.
36:53And if the environment changes, which makes some entities favored and others rejected,
37:00is that self-regulation only to those who are favored?
37:03I think the concept is not crisply defined yet.
37:06He also feels that what happened during the last ice age makes Gaia's self-regulation questionable.
37:11It lasted for 200,000 years and ended 12,000 years ago
37:15when we started the present interglacial warm period.
37:18During it, the ice caps extended towards the equator.
37:21Today, the North Polar Ice Cap is located chiefly on Greenland and round the pole.
37:27But during the last ice age, it stretched much further south,
37:30covering almost all the British Isles and much of northern Europe.
37:36For years, scientists have been studying the remains of these ice caps
37:40in an attempt to find out more about the ice ages themselves.
37:44By drilling into the ice, it's possible to learn something about the atmosphere of thousands of years ago.
37:51As the ice froze at that time, it trapped small amounts of air inside it.
38:00Drill out a core of ice and it'll contain minute bubbles of that ancient atmosphere.
38:06Melt the ice in a vacuum, releasing those trapped bubbles, and you have 20,000-year-old air.
38:11What they found is that it was different from ours.
38:15About 20,000 years ago, at the height of the last ice age,
38:18when planetary temperatures were something like 5 degrees Celsius colder than today,
38:22scientists have found that there was about a third less CO2 than there is in the atmosphere today.
38:28How could such a thing have happened?
38:31The theory goes that the microbes in the sea sucked down the carbon dioxide.
38:36Less of this greenhouse gas meant lower temperatures.
38:40In other words, the ice age became even colder and life made it that way.
38:47So, therefore, you find life actually amplifying the difference between the cold and the warm times.
38:53This is hardly a coincidence.
38:55Life actually amplifying the difference between the cold and the warm times.
38:59This is hardly an example of self-regulation because it's working in the wrong direction.
39:03It's making things more extreme from one to the other,
39:06and it's hard to see how that actually leads to benefit of a collective biosphere.
39:11Oh, I would respond to that by saying that they are, in fact, being anthropomorphic.
39:17They're thinking in terms of people.
39:19It's very inconvenient for us living in the northern hemisphere to have an ice age.
39:23It would be catastrophic in its effects.
39:26But if you look at the life on the planet as a whole,
39:29there is no doubt that during the depths of the glaciations there must have been more life on the planet.
39:35The total mass of life must have been greater because the CO2,
39:39as shown in the atmosphere, shown by the rock records,
39:43was lower during the heights of the ice age than it is now.
39:47And there's only one way that it could have been lower,
39:50and that was by more vigorous pumping by a larger and more active biosphere.
39:55So as far as Gaia goes, an ice age is not a bad thing.
39:58It's a good thing.
39:59It's these warm periods in between that represent the undesirable state.
40:05For Jim Lovelock, the self-regulation of the system does not mean that all life will survive,
40:10and human beings are no more favoured than anything else.
40:14But if Gaia likes to keep things cool,
40:17it will only be possible for a few million years more, according to Lovelock.
40:20The reason is that the carbon dioxide has almost completely gone.
40:25It's estimated that when the world began, CO2 made up about 30% of the atmosphere,
40:30that when life appeared, Jim Lovelock believes,
40:33it very quickly sucked this down to just a few percent.
40:37In the three billion years since then,
40:39CO2 has been steadily dropping until now it's about a thirtieth of one percent.
40:44If it goes on, CO2 will be at zero in a hundred million years.
40:50But the sun will still be getting hotter, so the system will become unstable,
40:54and will eventually flip itself into a new stable state,
40:57where life on earth will just have to tolerate much higher temperatures.
41:03We have just about reached the end of the capacity of the system to reduce CO2.
41:10You see, the reason is that plants need CO2 to grow.
41:13But as the sun warms up, you need less and less of it in order to keep the planet cool.
41:19And we're reaching a crisis point,
41:21because quite obviously plants can't grow at zero CO2,
41:25and yet zero CO2 will be needed to keep a constant climate in about a hundred million years' time.
41:31So a crisis is just about upon us, geologically speaking.
41:36In the past, Gaia has managed to cope with many crises to life.
41:40One occurred 64 million years ago, when the dinosaurs became extinct,
41:44along with 70% of the species then living.
41:47This wasn't the only mass extinction.
41:49The fossil records show they have occurred repeatedly.
41:52In fact, geologists use changes in fossils to date the history of the world.
41:57When certain types disappear in the rocks and are replaced by others,
42:01geologists describe it as the end of one period and the start of another.
42:05Professor Fisher.
42:07All of the world's natural history museums have large collections of fossils.
42:11These range from tiny things, of which there can be millions in a teaspoon of chalk,
42:16to such large and spectacular and rare fossils such as these dinosaurs.
42:23These fossils show beyond question that life on Earth has undergone great changes in the history of the world,
42:31and to geologists, the appearance and disappearance of different fossil groups
42:35has furnished a means of recognising discrete chapters in Earth history,
42:40called periods or systems,
42:43and every museum, every textbook has a chart of those systems, such as this one.
42:49And what has emerged during the last year is that they are all wrong.
42:55Professor Fisher recognises that the basic classification is correct.
43:00It's the variation of length that's the problem.
43:03Some of these periods are shown to be millions of years longer than others,
43:08but not according to the latest research.
43:11What has emerged in the last year is that the periods are of almost exactly the same length,
43:1774 million years.
43:20There are a couple of exceptions in which two successive periods add up to 74 million years together.
43:28What is remarkable about this is that with these periods changing so regularly,
43:32the implication is that mass extinctions also occur very regularly,
43:37and the question inevitably arises, what on Earth could cause this?
43:43One clue could lie in the large craters scattered over the Earth's surface.
43:47Dating reveals that those also were formed at regular intervals,
43:51which remarkably appear to match the times of the extinctions.
43:55The latest theory holds that the common link is a shower of comets hitting the Earth.
43:59The effect of an impact great enough to cause such craters would be devastating.
44:08It's calculated that the shock would be a thousand times
44:11that of all the world's nuclear weapons going off in one place.
44:16The effect would be to throw up a blanket of dirt and debris which would circulate around the world,
44:21blocking out the Sun, killing most plants and animals.
44:24That would explain extinctions, but not why they happen at regular intervals.
44:29Why should we be showered with comets so regularly?
44:34At Berkeley University in California,
44:36they've explained this with a controversial theory involving comets and the Sun.
44:42They need a telescope to find out if they're right.
44:45The man leading the project, Dr. Richard Muller.
44:48We finally found a mechanism that would do the job.
44:51If the Sun had a companion star, another star,
44:55that orbits the Sun on a 26 million year period,
44:59then when it came close, it would perturb the comets that are always out there
45:04and send a shower of them in towards the inner solar system where the Earth is.
45:09According to the theory, the solar system is surrounded by a huge ring of comets
45:14way out in space, known as the Oort cloud.
45:17It's thought to be the leftover debris after the formation of the solar system.
45:22Although many dispute Muller's ideas,
45:24if he's correct, then the Sun's supposed twin star
45:27will pass close by this ring of comets once every 26 million years.
45:32As it does so, its gravity will perturb or attract some of these comets away.
45:37As they fall back, they adopt an eccentric elliptical orbit
45:40which sends millions of them hurtling through the solar system.
45:44Result, the odds are that some of them will hit the planet Earth,
45:48causing huge craters and extinctions every 26 million years
45:52and, because of the orbit, a massive extinction every 74 million years.
45:59Each night, the scientists in the Berkeley Observatory prepare to hunt for the Sun's twin.
46:04Well, some fog, but I think we'll make it.
46:07How's everything? Is the computer out? Is the scan converter doing it?
46:10Computer is out. The scan converter is running.
46:12OK. Things look ready. Why don't we go ahead?
46:15By March of this year, they had mapped every suitable star in the northern hemisphere
46:20and were preparing to make the second survey to check how they'd moved.
46:24They're using the university computer to help the telescope locate every possible star.
46:30Richard Muller believes it might be one known as a red dwarf
46:34and visible with a pair of binoculars,
46:37but with this telescope, they intend to make sure.
46:40He has also had to think of a name for the Sun's supposed twin.
46:44I came up with several possibilities.
46:47My favourite is Nemesis.
46:50Nemesis was a Greek goddess.
46:53It was her job to make sure that no creatures on Earth
46:57became too powerful, too rich, too successful, too proud,
47:02namely, too godlike.
47:05If they did this, then she should destroy them.
47:09Well, the creatures on Earth before man that were most successful
47:13had been around for the longest time were the dinosaurs.
47:16And they were destroyed by something external,
47:19not by little mammals eating dinosaur eggs or anything else,
47:23not competition on the Earth. They were destroyed by an external agent.
47:26It seemed that Nemesis would be the appropriate name for this.
47:30If the two Greek goddesses exist, they've clashed before.
47:34But next time might be different for Gaia.
47:37The Sun's getting hotter, and despite mankind's best efforts,
47:41the carbon dioxide has almost gone.
47:44What will happen at the next collision?
47:47The nearer you get to the end point of one of these regulating systems,
47:51the more vulnerable it becomes to a perturbation.
47:55The less able it is to withstand it and return things to their status quo.
48:00And I would imagine that if we get another planetismal hit
48:04in the next hundred million years,
48:07the system's going to flip to a new stable state.
48:10As I mentioned earlier, it's going to flip to a new stable state
48:13anyway in about a hundred million years,
48:15but you could precipitate that change
48:17if you suddenly poked it when it's in this vulnerable state.
48:21Gaia's run by the sum of the biota,
48:24and therefore you can lose enormous numbers
48:27and great diversity with mass extinctions,
48:29but you never come anywhere near losing everything.
48:32And you certainly don't lose the major groups of bacteria ever.
48:35They've been in continuous existence,
48:38and we think it's the major groups of bacteria
48:40that actually are running the Gaian system.
48:42So in a sense, whether they're caused by impact or whatever they're caused by,
48:46these great extinctions are tests of Gaia, and the system bounces back.
48:50I imagine that if the system does flip to a different stable state,
48:54there'll be a sudden and enormous change in speciation,
48:57just as there was when the dinosaurs vanished, a great big change.
49:01And there'll be a new biota that will be fit for the new environment
49:06and the new system of things.
49:08I doubt whether it'll be very comfortable for us,
49:11but we're a very clever and adaptable species.
49:13Maybe we can cope. I don't know.