When life as we know it became possible on Earth
The mystery of how our planet's atmosphere became rich in oxygen has finally been solved
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Independent Minds
It was one of the most important changes to have happened to the Earth's atmosphere and it was the reason why today we can breathe life-giving oxygen. And yet the Great Oxidation Event has remained a mystery – until now.
Without oxygen, life on Earth would not exist as we know it. It has provided the supercharged air that has fuelled an explosion in the diversity and size of all living organisms, from the smallest shrimp to the biggest dinosaur.
About 21 per cent of air is oxygen, a vital ingredient for living organisms to carry out the most efficient method of converting food into energy using aerobic respiration. Yet an oxygen-rich atmosphere did not always exist, and the explanation for how it came about has eluded generations of scientists.
Now a team of researchers led by Kurt Konhauser of the University of Alberta in Edmonton, Canada, has come up with a convincing explanation for why oxygen suddenly began to accumulate in the early atmosphere of the Earth about 2.7 billion years ago, when life consisted of nothing more complex than single-cell microbes.
The Great Oxidation Event happened, they believe, when one group of oxygen-destroying microbes began to die off, leaving another group of oxygen-producing microbes to gain the ascendancy. The trigger for this event was a fall in a trace metal called nickel, which led to the inexorable rise of oxygen – and life – on Earth.
The role of nickel in the story of atmospheric oxygen is new. If Professor Konhauser and his colleagues are right then it could explain not just the explosive evolution of life, but how the Earth itself was shaped, because it the erosive power of oxygen that was so crucial to the sculpturing of rocks, the formation of rivers and the carving out of the coastlines.
"The Great Oxidation Event is what irreversibly changed surface environments on Earth and ultimately made advanced life possible. It was a major turning point in the evolution of life on our planet, and we are getting closer to understanding how it occurred," said Dominic Papineau of the Carnegie Institution in Washington.
Oxygen as a molecule is so reactive that it soon disappears unless it is being constantly produced. The concentration of oxygen in the atmosphere today is maintained by plants carrying out photosynthesis – the conversion of sunlight into chemical energy and oxygen.
The first photosynthetic microbes, the "blue-green" algae or cyanobacteria, are thought to have evolved about 300 million years before the Great Oxidation Event 2.5 billion years ago. But the oxygen they produced was quickly destroyed by the methane gas produced by the far more numerous methanogenic bacteria, which could breathe without oxygen using the less efficient method of anaerobic respiration.
These methanogenic bacteria, which still live in the waterlogged, oxygen-starved environment of swamps and wetlands, crucially need nickel to survive. Without a rich supply of nickel, the vital enzymes of these methane-producing microbes are fatally undermined.
The scientists found that by analysing a type of sedimentary rock known as banded-iron formations they could monitor levels of nickel in the oceans of the early Earth dating as far back as 3.8 billion years ago. They found there was a marked fall in nickel between 2.7 billion and 2.5 billion years ago – the same time as the Great Oxidation Event.
"The timing fits very well. The drop in nickel could have set the stage for the Great Oxidation Event. And from what we know about living methogens, lower levels of nickel would have cut back methane production," Dr Papineau said.
"The nickel connection was not something anyone had considered before. But our study indicates that it may have had a huge impact on the Earth's environment and on the history of life," he said.
Professor Konhauser said that the study, published in Nature, supports the idea that these methane-producing microbes prevented oxygen from accumulating in the early atmosphere for hundreds of millions of years.
The scientists believe that nickel levels fell because the Earth's crust had cooled down during this period, which meant that there was less nickel being ejected from volcanic eruptions into the ocean.
"We're certain from looking at the rocks in banded-iron formations that nickel dropped about 2.5 billion years ago to about half its previous value. The issue is how the methane-producing microbes responded to this decrease in nickel. We think they died off," Professor Konhauser said.
Although the Great Oxidation Event did not lead to a sudden rise of oxygen to levels like those experienced today, it did cause a significant rise that has never been reversed.
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Comments
I'm assuming what was meant to be said is that oxygen breathing life became possible at this point, however the question remains:
How did they know nothing but single-celled organisms existed at this time, which are complex in and of themselves? Sounds like speculation.
"We're certain from looking at the rocks in banded-iron formations that nickel dropped about 2.5 billion years ago to about half its previous value. The issue is how the methane-producing microbes responded to this decrease in nickel. We think they died off," - Again, sounds like speculation.
"Although the Great Oxidation Event did not lead to a sudden rise of oxygen to levels like those experienced today, it did cause a significant rise that has never been reversed." - Really? How do they know it was never reversed?
All sounds like speculation on top of more speculation to me.
Furthermore, there's no way to really know what the atmosphere would have been like at this time, that alone is guess work and speculation, so without even that as a clear foundation, how can scientists propose a theory like this?
"How did they know nothing but single-celled organisms existed at this time"
The records provided by rock samples indicate this. There has, as of yet, been nothing found in pre-Ediacaran (600My ago) strata to indicate the existence of multicellular life; in fact, even simple eukaryotes do not appear until 2,100Mya and all prior life seems to have been prokaryotic.
"We're certain from ... banded-iron formations that nickel dropped about 2.5 billion years ago ... The issue is how the methane-producing microbes responded to this decrease in nickel. We think they died off,"
First, the nickel content fall is observed, not speculation. Second, we know that all observed methanogenic bacteria require nickel. It is hardly speculation to surmise that a famine (of nickel0 would lead to a dying-off, is it?
"the Great Oxidation Event ...did cause a significant rise that has never been reversed. - Really? How do they know it was never reversed?"
Rocks again. For example, iron, which forms ferrous (Fe 2+) compounds in anaerobic environments and ferric (Fe 3+) in aerobic. Other examples of rocks which form in particular circumstances allow us to calculate approximate O2 levels throughout Earth's history.
Again, research, not speculation. So, enxt time you wish to snipe, at least do your research before coming to an ill-informed criticism of someone's work
Radiometric dating done on samples from the eruption of Mt St Helens should yield dates that match up with the date of the eruption as this is known. Instead they yield several different ages of millions of years. This research was carried out by the RATE group with samples dated by several different institutions. So my question stands, how do they know these organisms existed at that time?
As for the 2nd quote, yes the nickel content fall is observed, however they themselves said the issue is how the microbes responded...they THINK they died out but they do not know for certain. Speculation.
I'm hearing all this stuff about rocks from you but not from them. There was no indication that this had anything to do with their research. Granted, I'm not going to presume to know whether this is right or wrong so I'll take your word for it.
But frankly, the history of the world, as presented by such theories, isn't one I agree with either way.
Your comments on radiometric dating are misleading. The radioisotopes used for rocks of this age will have half-lives of great length otherwise near-complete decay of the isotopes will preclude the dating of the rocks. Using radioisotopes relies on the statistical decay of the isotopes, so for long half-life samples, an event as recent as Mt. St. Helens can not be robustly analysed with any degree of validity. Anyway, errors of several million years are accepted over long timescales, when one looks at rocks from 2 500 000 000, a deviation of several million years is still less than a one percent difference.
Therefore, radiometric dating still stands as a useful tool in the age discrimination of rocks. The existence of certain forms of life at this point is inferred from the presence of fossils and by the presence of chemical biomarkers (though the validity of some of these biomarkers as a purely biotic product has been reassessed lately).
This article reports another article, to say that the authors of the first article have not researched their subject on the basis of the summary here is pretty ignorant. Find and read the original article and see if your suppositions carry any weight.
This is a field that has been pretty intensely studied over the last decade, your comments about suppositions on suppositions are ill-informed and misjudged, many of these suppositions are pretty well accepted by the research communities involved in this field.
I still prefer some of the predominantly tectonic models for the Great Oxidation Event, they're more elegant and the scale and timing of ancient tectonic events appear to me to be much more efficient agents of such a dramatic change.
"...the history of the world as presented by such theories..." may not be one you agree with but sadly I'm not sure that anyone is going to revise their opinions of Earth History based on your say-so
I am commenting on what I observe from this article and what I observe is speculation built on speculation, I didn't use the word supposition. I believe I'm entitled to draw my conclusions from what I observe and what I believe just as they are, and just as they are entitled to present that conclusion, I'm entitled to comment on it.
The fact that their suppositions are pretty well accepted by the research communities involved makes no difference really. It could simply be a case of the blind leading the blind couldn't it?
I can hardly be blamed for not looking up the original article or papers when the article as presented here gave no links or indication towards the original. Perhaps they should do so before publishing such an article here for all to read.
The problem I have with articles like this and the arguements people have given me concerning my view is that these things aren't written for the average person or the person who doesn't spend 90% of their time online to understand. So scientists can say what they want and simply because it sounds scientific, people won't bother to question it. Then when someone does, another intellectual comes along and throws out a bunch of terms even the dictionary hasn't heard of. For example, I'm pretty certain the average person doesn't know that the model for atomic structure they are taught or have been taught in education is outdated and inaccurate. On the basis of that, how can people trust what these scientists say when they're constantly changing what it is their findings say without telling anyone other than the hardcore scientific community?
It's like being in a position of power, and because you have that power you use it to take advantage of those who don't know any better.
As for Mt St Helens, the fact is that yes you shouldn't be able to do radiometric dating on a sample of rock that formed after the eruption and get anything conclusive, but when you do, for rock that's mean to be 20 odd years old, the results say it's hard millions of years of radioactive decay.
If an species has less food available the numbers of this organism start to decrease. This has been observed countless times when animals habitats have been destroyed. So if there's less nickle available then the number of microbes will fall because there's not enough food to sustane a high population level. This is fact not speculation.
If you had read the scientists report, rather than a newspaper article, then you'd know that they used rocks to determine what was happening in the past.
What history of the world do you prefer, then one where God created everything for humans?
So you're saying radioactive decay begins when radioactive elements decay...decay begins when it decays...Well what I'm saying is that in order to date the rocks, you have to know when the elements began to decay and as far as I know this is counted from when the rock has crystalized.
"Also when Mt St Helens erupted it blew out a whole range of rcoks, some of which had been inside it for millions of years, so a wide agerange is not that unexpected."
It is when the rock tested is the rock formed from the molten rock that erupted.
"If an species has less food available the numbers of this organism start to decrease. This has been observed countless times when animals habitats have been destroyed. So if there's less nickle available then the number of microbes will fall because there's not enough food to sustane a high population level. This is fact not speculation."
If it was as straight forward as this, I'm sure they would have said so. They said they weren't certain how the microbes reacted and they THINK they died off. You're telling me that's not speculation?
"If you had read the scientists report, rather than a newspaper article, then you'd know that they used rocks to determine what was happening in the past."
As I said to someone else, if the Independent is going to write an article on a scientific report, perhaps they should provide a link to said report. I also said what I think about the use of rocks.
"What history of the world do you prefer, then one where God created everything for humans?"
As a matter of fact, yes :)
This is a relatively young research area and, as I mentioned above, some lines of evidence used in the exploration of these events have been reassessed recently and there are other models being explored to explain the G.O.E., I mentioned plate tectonic processes as a compelling alternative. I think that this demonstrates that this area at least is not dominated by dogma (yet).
You could easily Google the names of the authors and the subject if you desired to read the article (it is on the nature website), the author of the Independent article was just providing a digest and probably doesn't provide links because many articles are only available on subscription.
You seem to feel scientists are conspiring against laymen and suggest that this article and others are deliberately impenetrable so that scientists may retain their positions in their lofty towers yet this article seems pretty straightforward and, again, is not written by a scientist so even if it were incomprehensible it would be another step down the line from scientists. When 'jargon' is used it is usually to communicate against specialist, to communicate in plain language would entail the kind of monstrous words that get used by germans when they splice thirty shorter words together. Also, your statement concerning atomic structure is interesting given that we spent the best part of a lesson at my school learning the history of models of atomic structure and were explicitly told that the model we used was not correct but was the most convenient model for our purposes without getting into undergrad level explanations. If your argument were correct it would not be scientists deluding the public, it would be teachers and journalists and you would be justified in your conspiracy theories.
Your comments on radiometric dating are still wrong, perhaps I didn't explain clearly before but Mt. St. Helens does not provide a robust or representative test of the method. Using rocks this young is akin to using a survey of ten people to represent the views of a nation, the vast half lives of the isotopes used require vast times over which to decay before the rates observed fit a statistical model, you are however quite correct that the age represents the age since cooling.
In one of your earlier comments you say there is no way to know what the atmosphere was like, actually there is, the rocks record a number of clues.
You say you do not like the history presented in this article, the mechanics may be wrong but there was a great oxidation event and if you prefer to believe that God caused it then so be it, but in that case God was behind the agent of change, there will still have been an agent of change though.
"What history of the world do you prefer, then one where God created everything for humans?"
As a matter of fact, yes :)
The old bury your head in the sand routine, a fear of anything that contradicts a fable from 2000 years ago. Embrace science and advance your understanding of this universe.
The problem is that "science" today presumes to answer questions it has no business answering, namely origins. Science is there to tell us how things work, not how they began. Science is based on observable and repeatable events, and frankly the origins of life are neither observable or thus far repeatable. It's a metaphysical and philosophical debate, and science deals with neither one of these. So could you please explain to me how my understanding of the universe isn't being advanced if I don't believe in what science says about origins?
I wonder what the writers of this research would have to say about this:
http://live.psu.edu/story/38514
I am a layperson and not ashamed to say it, which makes me think independently and look for what really matters, and that is a working observable experiment as defined by pure science that proves their theories. If a scientist can't demonstrate this then it's not ignorant on my part to say they have proved only the ability to hypothesize on their presuppositions.
There is no motive for a scientist other than to observe and study what he sees. Science is wonderful and interesting.
You are right, that is what scientists do, and I don't see why I should have to be a scientist to say their conclusion doesn't sound very concrete to me. Afterall, they publish their findings for the public to see, I believe the public is intelligent enough to say whether they think the emperor has no clothes, or to acknowledge the elephant in the room.
Indeed I could propose a hypothesis, but as near as I can tell you are someone who has their own set of presuppositions about the world and therefore my hypothesis would be nothing to you. We could sit here and argue about hypotheses and theories all day until we are blue in the face and not get anywhere, and there's no point in that so I will just say this:
The underlying world view upon which this research is based on is based on a uniformitarian, naturalistic world-view which makes no logical sense. It proposes to tell us that something can come from nothing and that nothing can produce meaning. But how can nothing produce meaning? If nothing can produce meaning than meaning is really nothing and nothing has any point because there are no points. The blind watchmaker isn't just blind, he's deaf, mute and braindead. Therefore, how can we truly know anything? Obviously we DO know something, and so there must be a source of meaning that isn't just random chemical processes.
Science is a wonderful tool for explaining what we observe today, but beyond that it is speculation, and shaky speculation when it comes to origins. Indeed, there is motive for a scientist to observe and study what he sees, HOWEVER, some will only observe and study what fits into his own little box of how the universe works. Anything outside that box, however viable, is ignored. That is not clear and true motive. A scientist should be one who searches for truth and not just proof of one narrow world view.
Have you ever allowed your own personal search for truth to go beyond "Anything else is not true because it's foolish and it's foolish because it's not true."? I once believed all this stuff, but I got to a point where I realised it just did not make sense of the universe I live in, so I can understand why people hold on to it. What's more confusing is why they get so worked up if someone else doesn't.
It's called photolysis of water vapour. The hard UV from the Sun splits water molecules high in the atmosphere. The resulting Oxygen stays Earthbound, the resulting free Hydrogen drifts upwards and escapes into space. We knowthat this happens now because we can measure the Hydrogen in the Geo corona. Actually it's a pain in the neck for reseachers using satelites for space research in the far UV. Let this process run for 4.5 thousand million years and you generate enough free oxygen to account for the atmosphere several times over. The total quantity of water thus converted corresponds to decrease in ocean water levels of at most a few ten meters.
So, it's the mix of water and Sun, not bacteria.
Human being are so crazy, just burnes and destrois everithing.
To violent and deestroy the Law's of Natur, will destroy Human Kind.
Embodied beings, with their grotesk limitationes and mortal natur, want to control Universal Natur of Cosmic Entity - must be a Joke.
No sane living entity can be serious to try to do that.
What those want to understand about the Absolute, whom are not even able to Think. - without words
Massege to Humanity - Love Respect and Obey The Natur of Cosmic Creation Vedic Truth
Purpose of Life Breth Extention.
Crazy Fools thinking, purpose of life is to make money and lord over nationes above nationes.Humans schould be Unified to Safe The Living Planet, As It Is...
Remember, when You are finished to shoot kill and burn everything, there will be no more Air to Breth.
Sincerelly
Remember = those who killed the indians, and their knowlidge of Natur, They are all Dead too.
It's a funny old game is pre-history.
Thus the nickel levels only record the fall in the level of methanogenic bacteria and are not the cause.