When did Earth's oxygen atmosphere appear?

By Phil Plait | March 21, 2009 10:00 am

In my book Death from the Skies!, I described Earth’s first mass extinction event: the evolution of bacteria that were able to ingest the primitive atmosphere of the time, and excrete oxygen. To these little beasties, oxygen was a lethal poison, and when enough accumulated in the atmosphere, it killed off a lot of our planet’s nascent life. They couldn’t survive their own waste (and, as I point out in the book, take home whatever cautionary tale from that you like). The survivors were ones who could use this new molecule to their advantage.

Billions of years later, those survivors became us.

But how many billions of years? Current thinking is that this event happened about 2.7 billion years ago.

But new data seem to indicate that this event may have happened earlier than that. A lot earlier: like 3.5 billion years ago. This new data comes in the form of geological core samples containing hematite, a mineral that forms either through aerobic processes of bacteria (that is, biology using oxygen) or through photolysis (chemical changes from light) due to sunlight. But that latter happens only near the surface of water, and the hematite in the core samples seem to be from too deep in water to be from photolysis.

Bacteria smoking
The real reason all the good air went away.

The new data are controversial, of course. It’s one thing to push back a date for an event like this, but another entirely to do so by 750 million years! A lot of current evidence points to free oxygen being produced 2.7 billion years ago. Clearly, either one or both of these measurements is wrong. Sometimes, when I hear a controversy like this, I wonder if they’re both in fact right: maybe there was free oxygen produced at the earlier date, and it went away for a time due to some mysterious event, and then came back 700 million years later as cyanobacteria rediscovered how wonderful oxygen is.

I’m just talking out of my hat there. Usually in science, when there are two contradictory sets of data, one turns out to be wrong. Misinterpreted or dated incorrectly. But not always. The fun part of this will be the arguing that goes on between scientists as they try to figure this one out.

My advice for them: before arguing, take a deep breath. And whoever turns out to be right, remember just why you can take that breath.

There’s no way that, all those eons ago, those little bacteria could have known that their distant descendants would ponder their very existence. But life’s funny that way.

Tip o’ the reducing atmosphere to Larry Klaes.

Bacteria image from V2’s Flickr photostream and cigarette from http://www.flickr.com/photos/denisdefreyne/1148931440/” target=”_blank”>Denis Defreyne’s photostream.

CATEGORIZED UNDER: Cool stuff, Science

Comments (68)

  1. Joules

    Interesting, Now I am wondering if our fate could be similar to those ancient bacterias that couldn´t survive their own waste, as you mentioned.

  2. Dude, those E. coli are smokin’.

    I thought I recognized those bacteria. They show up on the first page of Google image results for “e. coli”. They’re from a University of California page on E. coli research.

  3. Greg in Austin

    You wrote a book?

    8)

  4. >>And whoever turns out to be right, remember just why you can take that breath.<<

    That is a great point… artfully put. Wish all scientists could remember that, because questioning and debate are crucial tools. But sometimes it seems the only time they pull together is when creationists start ranting, LOL…

  5. Come on Phil! Don’t you know that bacteriogenic, second hand smoke spawned, mass extinction events are just pseudocientific lies invented by the liberal media because they want to take away your freedom?

  6. Now the IDers will cry “Teach the controversy about Oxygen!”
    [grumble]
    Science works exactly this way, and that is the very source of its power!

    Your “remember just why you can take that breath.” reminds me of the way I talk about planetary nebulae with Scout groups at McCormick Observatory. I tell them to thank PNs every time they do this: [I inhale deeply] for that’s the source of the oxygen they breathe. (Nitrogen too!)
    :lol:

  7. Randy A.

    As a science teacher, I find that my students often see science as a body of knowledge that they’re expected to learn. And unfortunately, I often must teach it that way, because we have a lot to cover in a semester.
    But I love to point out controversies like this, that show that scientists are constantly investigating new things, and revising old theories. To me, this is what makes science fun and interesting!

    I also like pointing out connections. For instance, 2.7 billion years ago, reduced iron in the ocean was oxidized, and hematite precipitated onto the sea floor (the age of these layers is the prime evidence for those who say photosynthesis first evolved 2.7 Ba). This hematite formed the “banded iron formations” that are our primary source of iron today.
    So think about it — your car, and all the steel and iron we use today, is available to us because of those photosynthesizing bacteria a couple billion years ago…

  8. Wendy

    All so fascinating!!!

  9. CoffeeCupContrails

    This is wonderful. When our understanding of the genome data improves vastly in the future, it may become possible to decipher the structures of all the oxygen excreting ancestors of ours: all the different species that came and went before the first animals by simply reading our genome. Our DNA is, after all, the very best fossil record.

    From that structure and chemical composition, it will then be possible to determine the gases or liquids that they processed to release the oxygen (or other elements and compounds), giving us an idea of the composition of the atmosphere or at least the local environments that our ancestors thrived in.

    THERE’s science for you.

  10. Dan Izzo

    Phil, Phil, Phil;

    Don’t you know that it was Jesus who destroyed the sinful bacteria and that this all really occurred 6000 years ago?

    On a more serious note. That’s pretty interesting, pushing the date back that far I would guess could really change some ideas about the progression of life. After all 700 million years is long time even on evolutionary timescales.

    Are there any theories on what fills the evolutionary gap? Did the oxygenization just take longer than we thought? Or did things stagnate for awhile.

    I was under the impression that we have a fairly complete picture of large scale evolution, but if we suddenly push the date of oxygenization back 700 millions years, doesn’t something have to fill the gap?

  11. QUASAR

    I took so many millions and billions of years for this Earth to get to this condition and now we’re going to ruin it in less than 1,000. If we don’t manage to destroy ourselves, do you think that our descendants in distant future will view us as the great apes or just those greedy apes?

  12. whomever1

    Surely you can come up with a death from the skies scenario for generating oxygen–couldn’t you get some monatomic oxygen by smashing some comets into the earth?

  13. QUASAR

    @ whomever1

    It would take a lot of comets to generate the amount of oxygen that the Earth currently has or had billions of years ago!

  14. Chip

    A “far out” but fun speculation was presented on (I think) a NatGeo program several years ago, based on the theory that the Moon was formed very early in Earth’s history when a large body in the still-forming solar system collided with early molten Earth, ejecting lots of material. The early Moon orbited much closed to Earth then. This concept has been known for many years.

    The newer speculation, based on the chemical content of very old rocks from Greenland, surmises a slightly different story. An early Earth formed including oceans and possibly life but without a moon. Then, along came a massive body that collided with “Earth 1″ vaporizing the oceans and land surface. Life arose again on “Earth2″, the Earth we know today. Cool idea though it makes the Occam’s Razor gauge jump a few points.

    Another theory is that after early microbial life arose on Earth, the planet, due to continental drift and atmospheric changes, froze down to the equator becoming “snowball Earth”. We are the decedents of the microbes that survived under the ice.

  15. Didac

    The atmospheric transition seems to be a very ancient and far from smooth process. However the idea of a great extinction of anaerobes may take into account what “atmosphere” means for bacteria. Microhabitats in the soil present pronounced concentration gradients of O2 and other gases. One must not forget that even in our guts, the rule belongs to anaerobes such Bacteroides.

  16. Grump

    QUASAR Says:

    I took so many millions and billions of years for this Earth to get to this condition and now we’re going to ruin it in less than 1,000

    I see something different in the multiple extinctions of Earth’s history: Humanity is not “ruining the Earth” (not completely, anyway.) We’re only destroying ourselves.

    “Life” in the broadest sense will continue long after humanity is gone. Even if we kill off ourselves, and 99% of all the other species, even by so dramatic an act as a global thermonuclear war, so what? It has happened before, and after only a few million years (a tiny expanse of geological time) the Earth was teeming with life again, as the few survivors flourished in all that open real-estate.

    So next time some New-Agey “Green” tells you that we must stop destroying “Mother Nature”, point out that we can’t! Mother Nature is incredibly robust, and She doesn’t give a flying fig about humanity, we’re just another species. And the species we destroy will be replaced by others as soon as we’re gone.

    No, in the end the only reason to protect the environment is to save our own sorry asses.

  17. So, Grump, what you are saying is “All of this has happened before. All of this will happen again.” ;)

  18. QUASAR

    @ Grump

    Hello? What world are you living in? Habitat destruction, overpopulation and pollution are very serious problems!

  19. ExExExEx

    @QUASAR

    He lives in the real world.

  20. Bruce

    He never argued against them being serious problems, all he said is that if we don’t clean up our act, the planet WILL recover. We just won’t be around to see it.

  21. George

    Still hoping for some comment from you, Phil, regarding the purported terminal Pleistocene North American comet encounter. The NOVA companion website for the March 31 episode concerning same is up and running. Check out the promo and fascinating new information here: http://www.pbs.org/wgbh/nova/clovis/program.html. Phil, I have made repeated posts requesting your comment on this subject. It certainly would seem an astronomer, blogger, and author of a book called “Death from the Skies” would take notice and comment — supportive or skeptical — on these extraordinary findings.

  22. George

    My link was bad because it inadvertently included a period. Here is a good one: http://www.pbs.org/wgbh/nova/clovis/program.html

  23. Adam

    Grump’s right. Humanity could easily ruin civilization through incompetence and shortsightedness. With a fair amount of luck we might manage to render ourselves extinct (although it would be difficult, people are resilient, adaptable, and very widespread). But ruining nature permanently is beyond our current capabilities. Even if we could keep up our 20th century lifestyle indefinitely, nature would adapt just as it did to the original pollutant of oxygen. You’d see thriving ecosystems soaking up the nutrient rich outflow of farms, insects sequestering pesticides to use as a chemical defense, organisms doing annual cross country migrations by clinging to trucks, and who knows what else. Nature’s main problem with humanity is that we don’t stand still long enough for it to adapt. But hopefully civilization can come to some sort of equilibrium and we will wind up with a world filled with greater diversity and possibility just as the advent of photosynthesis opened the way for aerobic respiration, terrestrial life, and multicellularity.

  24. Craig

    @Joules:

    Interesting, Now I am wondering if our fate could be similar to those ancient bacterias that couldn´t survive their own waste, as you mentioned.

    Not quite. As I understand it, the cyanobacteria that were emitting the oxygen (as a side effect of having evolved photosynthesis) weren’t killed off “by their own waste”; rather, their waste killed off almost everything else. It was atmospheric genocide, not suicide.

    Of course, the cyanobacteria copped it in the end when oxygen-breathing critters evolved and ate nearly all of the cyanobacteria…

    @Quasar: Grump is right. We aren’t killing Mother Nature, Mother Nature is threatening to kill us.

    Yes, we’re driving massive extinctions and distinctly altering the composition of the atmosphere right now, but those are temporary effects and not without precedent in Earth history. Give it a few million years and you’d have to look hard to even know we were here.

    I say this as a fairly politically active greenie (horrified by deforestation, terrified by climate change, not overly troubled by nuclear power but would prefer true renewables nonetheless). Nature is a lot bigger than we are; we can affect it (because we’re part of it), but we can’t destroy it.

  25. There is a theory that evolution provides species with a “self destruct” button, therefore it can only evolve to a certain point. Some theorize this is the reason we have not heard from anyone else out there in the Universe

  26. sure thing

    ok, then how do you explain Britney Spears?

  27. There’s really no conflict in this case. Earth’s bulk atmosphere didn’t go oxic until about 2.5 billion years ago, or a little later, but that doesn’t mean cyanobacteria evolved two weeks prior. It’s very likely that oxygenic photosynthesis evolved several million, or hundreds of million, years before but still wasn’t particularly common in the world at large.

    It’s difficult to over-emphasize how destructive the evolution of oxygenic photosynthesis was, at least in the short term, back in the Archean Eon. Producing free oxygen then was roughly equivalent to what would happen if some microbe today evolved the capacity to pump out chlorine gas. At first, any microbes living near the first colonies of cyanobacteria would have been killed outright by the lethal oxygen stinking up the place.

    Being able to exhale a chemical warfare cloud would probably have been very useful in keeping competitor microbes out of your way. This would have helped cyanobacteria muscle their way into a wide range of marine photic-zone niches… such that millions of years later the cyanobacteria situation would get quite out of hand. One result was total oxygenation of the atmosphere.

  28. amphiox

    It seems likely to me that the earliest photosynthetic organisms would not have been immune to the toxic effects of oxygen. When they first appeared, their O2 waste would have been rapidly diluted by their environment. These O2 vulnerable photosynthesizers would likely have been the majority until total O2 levels reached a critical threshold, after which they would have been exterminated along with the rest of the O2 sensitive lifeforms, and subsequent generations of cyanobacteria would have descended from the minority that did evolve O2 resistance.

    Aerobic utilization of O2 probably evolved significantly later. The survivors of the oxygen crisis would have mostly been facultative anaerobes.

    So it is not inaccurate to suggest that the first photosynthesizers really did exterminate themselves with their own waste.

  29. amphiox

    It is extremely unlikely in my opinion that any human induced event would be capable of causing total extinction of humans. The survivors of mass extinctions have generally been the widespread, the adaptable, and the flexible, and humans have all these talents in the far extreme.

    It is very likely that even in the most extreme cases, some small populations scattered around the world would survive, and repopulate the planet. (There is the possibility that these separate populations might speciate if the crash was bad enough, and we could get a replay of the sapiens-neanderthal situation, in which case it won’t be guaranteed that H. sapiens will be the variant that inherits the earth, but the new species would still be ‘human’).

    The only thing going against us is our relatively large size, as mass extinction survivors tend to be small critters.

    Human civilization, of course, is incredibly fragile and would be guaranteed to be snuffed.

  30. Torbjörn Larsson, OM

    Nice subject, I had hoped somebody would blog about it.

    A lot of current evidence points to free oxygen being produced 2.7 billion years ago. Clearly, either one or both of these measurements is wrong.

    Layman here, but I don’t think this is entirely correct, as Planetologist noted. IIRC they have found fossils of organisms known to photosynthesize (in their modern form, at least) as far back as that. (While earlier formations indicating free oxygen seems to date back to 2.4 Ga.) So there is AFAIU no direct conflict between the measurements.

    What intrigues me is that this may point to oceans that are quite like the modern ones at this time. Apparently there are cherts that gives Archean temperatures (two isotope thermometers) descending from ~ 70 Celsius @ 3.5 Ga to ~ 60 Celsius @ 2 Ga.

    But photosynthesis, at least its modern variants, has an upper temperature limit of 73 Celsius and much lower at low pH’s (45 Celsius @ pH 2). I assume that this means the oceans had lost their initial acidity at 3.5 Ga.

    The real conflict may be atmospheric data. If Archaean temperatures depended on an initial dense CO2 atmosphere, say 10 bars as I have seen suggested, it is harder to understand how free oxygen could exist that early. Though the temperature data has some large excursions so BA’s idea of some large scale events may be the key.

    For instance, 2.7 billion years ago, reduced iron in the ocean was oxidized, and hematite precipitated onto the sea floor (the age of these layers is the prime evidence for those who say photosynthesis first evolved 2.7 Ba). This hematite formed the “banded iron formations” that are our primary source of iron today.

    As I described above, I believe the data, especially the prime evidence, is slightly different. (And FWIW Wikipedia seems to agree.)

    Anyway, the exciting thing is that the Nature article abstract refers to hematite. (If not banded iron formations, as the news article illustrates with, and claims the researchers refers to. Pay walls are a public enemy.)

  31. Torbjörn Larsson, OM

    [Test comment, to see if it works.]

  32. Torbjörn Larsson, OM

    [Test comment with links removed, due to commenting difficulties.]

    Nice subject, I had hoped somebody would blog about it.

    A lot of current evidence points to free oxygen being produced 2.7 billion years ago. Clearly, either one or both of these measurements is wrong.

    Layman here, but I don’t think this is entirely correct, as Planetologist noted. IIRC they have found fossils of organisms known to photosynthesize (in their modern form, at least) as far back as that. (While earlier formations indicating free oxygen seems to date back to 2.4 Ga.) So there is AFAIU no direct conflict between the measurements.

    What intrigues me is that this may point to oceans that are quite like the modern ones at this time. Apparently there are cherts that gives Archean temperatures (two isotope thermometers) descending from ~ 70 Celsius @ 3.5 Ga to ~ 60 Celsius @ 2 Ga.

    But photosynthesis, at least its modern variants, has an upper temperature limit of 73 Celsius and much lower at low pH’s (45 Celsius @ pH 2. I assume that this means the oceans had lost their initial acidity at 3.5 Ga.

    The real conflict may be atmospheric data. If Archaean temperatures depended on an initial dense CO2 atmosphere, say 10 bars as I have seen suggested, it is harder to understand how free oxygen could exist that early. Though the temperature data has some large excursions so BA’s idea of some large scale events may be the key.

    For instance, 2.7 billion years ago, reduced iron in the ocean was oxidized, and hematite precipitated onto the sea floor (the age of these layers is the prime evidence for those who say photosynthesis first evolved 2.7 Ba). This hematite formed the “banded iron formations” that are our primary source of iron today.

    As I described above, I believe the data, especially the prime evidence, is slightly different. (And FWIW Wikipedia seems to agree.)

    Anyway, the exciting thing is that the Nature article abstract refers to hematite. (If not banded iron formations, as the news article illustrates with, and claims the researchers refers to. Pay walls are a public enemy.)

  33. Torbjörn Larsson, OM

    I have to give up on the links.

    The chert data is from “A palaeotemperature curve for the Precambrian oceans based on silicon isotopes in cherts” Franc¸ois Robert & Marc Chaussidon; Nature, Vol 443, 26 October 2006.

    The photosynthesis data is from “Limits of Microbial Photosynthesis in Hot Spring Ecosystems”, Cox, A. D.; Shock, E. L.

    And Wikipedia reference is from Wikipedia, :o “Oxygen revolution”.

  34. IVAN3MAN

    @ Torbjörn Larsson, OM,

    Hmm… you’re comment with links gets ‘spammed’, but bloody OilIsMastery’s comment gets through on the “Entire Cosmos series is on HULU” thread! What’s going on with your so-called ‘anti-spam’ filter, Phil?

  35. IVAN3MAN

    Err… that should be your, not “you’re”. Damn stupid Norton Security Scan always comes on when I’m in the middle of doing something and distracting me!

  36. @ Michael L:

    There is a theory that evolution provides species with a “self destruct” button, therefore it can only evolve to a certain point. Some theorize this is the reason we have not heard from anyone else out there in the Universe.

    What would be the benefit to the species of such a feature? How would it help an individual animal pass along its genetics?

    That theory seems to contradict the very forces that drive evolution. I suspect it is woo.

    Besides, I think there’s a better reason why we haven’t heard from anyone: intelligence, as we define it, may not be a successful long-term survival strategy. Intelligent species may simply be too starkers to get too much far beyond the rocket stage before managing to bring about their own demise.

  37. IVAN3MAN

    @ kuhnigget, and Michael L,

    In Cosmos: A Personal Voyage, Prof. Carl Sagan stated:

    If civilizations tend to destroy themselves soon after reaching a technological phase, there might be no one for us to talk with but ourselves. And that we do but poorly. Civilizations would take billions of years of tortuous evolution to arise, and then snuff themselves out in an instant of unforgivable neglect.

  38. icemith

    I read about two thirds of the comments about four or five hours ago, during a break from mowing the lawn. Very interesting. And I think I looked more than once at the photo of the bacteria etc. I had even thought about making a comment about it.

    However, after a shower and dinner and a bit of TV, decided to read the rest of the comments, as there would be a few more by now. That is when I noticed it. There were black streaks across the photo, vertical streaks, looking as though they were Smoke Billows from the white bacteria. Then it dawned on me. They WERE cigarettes, and I believe they were not smoking before. I checked the original blog e-mail and they were smoking there too.

    So, how come I didn’t notice the black smoke before? Is this photo “Evolving” over time? Maybe not 2.7 or even 3.5 Billion years, but is it happening? Maybe not overnight, but happening nonetheless?

    Did anyone else notice this? Or was I just too worn out from mowing? (No comments about “grass” will be tolerated.)

    Ivan.

  39. We’ve known microbes appeared (via fossils) as far back as 3.5 bya for a while. That they were oxygen-producing is news to me, though – I’d have to go back and check my sources. It is very likely that some form of life-produced oxygen environment arose on Earth not just once, but several times – perhaps many times – before it finally “took” (around 2.1 bya “ish”). Why would it go away? Both extra-terrestrial and terrestrial reasons are possible. For ET events, we have large impact events, especially early on, having a good chance of reforming the surface and atmosphere.

    More probably, especially in connection with a yo-yo effect of oxy/non-oxy atmospheres, the oxygen-producing bacteria could have been too successful, overproducing and outgrowing their environment, to the point where they poisoned themselves out of a home and died off before they could adapt, leading to a collapse of the O2 production and resurgence of CO2. A strong CO2 atmo causes a resurgence of O2 producers and the cycle starts again, over and over many times (possibly) until the right balance is achieved between CO2-breathers and O2 breathers.

  40. Mena

    But Science Pundit, the liberal media ate my baby!!!!

  41. There are physical and geochemical signs of photosynthetic life on Earth going back to 3.85 Ga, when deposits of organically-derived (isotopically light) carbon were laid down in rocks now found near Isua, Greenland. Layers of graphite at Isua suggest that microbial mats in the photic zone were around at that time, and it seems more likely than not that such mats were exuded by photosynthesizers.

    Slightly later, around 3.5 Ga, we have structures that appear to be stromatolites. However, it’s most probable those early sun-feeders weren’t oxygenic, they were producing sulfur. Prior to the evolution of oxygenic photosynthesis there were lots of bacteria that used sunlight to drive the oxidation of H2S gas to elemental sulfur or possibly sulfate, coupled with reduction of CO2 to generate biomass. During the Archean volcanic activity was more vigorous than now, and the mantle probably had a slightly higher fH2 than today, so there was more atmospheric H2S to support at least regional environments of vigorous sulfur photosynthesis in the oceans. Other forms of photosynthesis use ferrous iron as an electron donor… there are several options.

    Oxygenic photosynthesis likely evolved from early cell lines that used H2S… put super-simply, cyanobacteria eventually learned the trick of using H2O instead of H2S…. producing O2 instead of S as a waste product, and opening the entire world ocean photic-zone as a potential habitat. That’s an oversimplification, because the biochemistry of oxygenic photosynthesis is really complicated, and apparently so tricky to evolve that it only happened once in all of Earth’s history… or at least it evolved in only one group, ever. I’m actually writing a paper on this topic now, focused on the hypothesis that O2 atmospheres are probably very rare in the universe.

    Anyway, I also wanted to add that ferric iron can be produced without oxygenic photosynthesis. An easy way is photolysis… ferrous iron in the ancient ocean photic zone would have been exposed to harsher UV than today (no ozone layer to speak of), promoting more efficient production of Fe(III) at the ocean surface. Once produced, dissolved Fe(III) is highly insoluble – even in a moderately-acidic Archean ocean – and would have sedimented out. I suspect this new study’s results for that reason: that photolytically derived ferric oxides could have produced limited quantities of hematite at regional scales, without any biological mediation at all. An interesting thing about such photo-iron deposits is that they would have provided a rich energy source for iron-reducing microbes living in seafloor sediment. It’s not clear exactly when Fe(III)-reducing metabolism evolved, but it’s likely at least that old. So, one doesn’t need an O2 atmosphere to produce hematite, or even a world where O2-producers are found. One only needs a UV source and dissolved ferrous iron.

    Shameless plug, but I blog about these topics quite a bit…. origins of life and the geochemical evolution of planets, astrobiology and similar.

  42. I have a few doubts about this new study, actually. Here’s my own take on the topic:

    http://planetologist.net/2009/03/22/photosynthesis-in-early-archean/

  43. George N

    Isn’t this dying out of organisms the same thing that happens to the yeasties in the making of beer? Poor little darlings.

  44. Gary

    Once, many years ago, I was fortunate to examine microscopically a thin section of rock dated at 2.3 billion years old that contained shadowy strings of spheres – cynobacteria – that were early oxygen generators. At that time, these were the oldest known fossils. Way cool.

  45. TheBlackCat

    @ George: according to the Nova article, they have essentially nothing back it up besides the fact that there happened to be a few fires. And the article cites a lot of evidence contradicting the position. It could have happened, but what they present is far from convincing. We are talking about an event that far exceed the Tunguska event.

    Besides, extinctions of most or all large land animals in a given area happened consistently in the recent past, but not at the same time. They always happened shortly after the time humans first arrived in a given area. It happened on every continent and island worldwide besides Africa. It happened as far back as prior to the end of the lass ice age and as recently as less than a thousand years ago when the moas were wiped out (or even more recently if you include the dodo). I think the implications are pretty clear.

  46. TheBlackCat

    I should add that the current rate of extinction is on par with the rate during the time the dinosaurs went extinct. Currently 1/4 of all animals species are at risk of extinction. If they die the period of human history would be one of the worst mass extinctions in the history of the planet.

    That being said, the planet has come through mass extinctions where 90-95% of all life went extinct, so life on this planet is not going to get wiped out no matter how hard we try.

  47. Fredrik

    Isn’t it well established that it took a while before oxygene started to appear in the atmosphere due the iron oxidizing?

  48. Derek

    I believe we are destroying earths atmosphere now. Not by gas or poison but radio telecommunications.

  49. rightross

    You have no idea what happened 2.7 billion years ago and the sooner you “scientists” admit it, the better off all of us will be. You change your ideas like a giddy, teenage dgirl changes her clothes before her first date yet every time you do you report the new change as fact. If you don’t like the Creation/intelligent design notions I can deal with it but, for goodness sake man, 2.7 BILLION years ago is a long time. We don’t even really know what happened 500 years ago – we revise actual “recorded” history all the time and we get our knowledge about that from people who were there, observed it, and wrote books about it.

  50. Darth Robo

    Always leave it to an IDer/Creationist to say:

    “How do YOU know? Where you THERE?!?”

  51. @rightross
    We don’t even really know what happened 500 years ago – we revise actual “recorded” history all the time and we get our knowledge about that from people who were there, observed it, and wrote books about it.

    A bit like the bible eh?

  52. TheBlackCat

    @ Shane: “A bit like the bible eh?”

    The people who wrote the Bible (New Testament) were not present at the supposed events, they are second- or third-hand accounts at best. For the stuff in the book of Genesis it was perhaps dozens of generations after the supposed events occurred.

    Given a choice between human accounts, the records nature has indelibly etched in the stones all around us, I prefer to trust the rocks. Nature doesn’t lie, have biases, try to demonize its opponents, or do any of the untrustworthy things humans do.

  53. @TheBlackCat

    I agree TBC. I’ll turn up the sarcasm meter a little more next time. :-)

  54. TheBlackCat

    @ Shane: I wasn’t trying to disagree with you, I was trying to further reinforce the point I thought (apparently correctly) that you were making.

  55. @TheBlackCat
    No worries. I thought so, then I second guessed and then my bad. Cheers :-)

  56. AK

    There are a couple of misconceptions I’d like to address:

    First, the “evidence” of cyanobacteria that long ago isn’t. The fossils show strong similarities to cyanobacterial colonies: long strings of cells (created by binary division that lengthens the strings) with occasional swellings that could well be specialized cells with alternate functions. In cyanobacteria these cells perform nitrogen fixation, and are insulated from the oxygen-rich environment by multiple layers of membrane. This is necessary because even trace amounts of oxygen can poison the fixation process. What these fossils appear to be is some bacterial lineage with a similar requirement for specialized cells that perform an easily poisoned function. However, that’s no proof that they’re cyanobacteria, or performing nitrogen fixation. The similarity of shapes, which isn’t really all that great, may well be the result of convergent evolution.

    The second misconception is that cyanobacteria are necessary to create oxygen. All modern photosynthesis today uses the Z scheme mechanism pioneered by cyanobacteria, either as such, or via chloroplasts, which are derived from cyanobacteria. However, prior to the appearance of this scheme, it’s quite possible that a number of different mechanisms were present involving running part of the electron-transport chain backwards. Such mechanisms probably would have gone extinct after cyanobacteria evolved, although the peroxisomes of modern Eukaryotes may be vestiges of them.

    @Planetologist:

    I left a reply to your point at your blog.

  57. Jeff

    I do not think 750 million years error is significant when we are talking about the Precambrian era. Of course, after the Cambrian, the fossil record is pretty firm. But before that, it is very murky and even a billion or 2 billion years off before that time really doesn’t tell us much. The earth is so dynamic, so much recycling of the crust has occured, and preCambrian record so obscure, that the true origins and early phase of life might be permanently erased.

  58. Yes, yes… Bible and all that… okay, now back to reality.

    @Fredrik
    Yes, the conventional model of atmospheric evolution during the Archean, consistent with the available geochemical record, shows that molecular oxygen attained low atmospheric concentrations by about 2.5 Ga… probably no more than 1% or so. For a long time after that atmospheric O2 was more or less buffered by sedimentation of marine ferric oxides. Basically that means most of the O2 produced by marine cyanobacteria was immediately consumed to oxidize dissolved ferrous iron to ferric, and ferric is pretty insoluble… as soon as it formed it precipitated out as solid little particles of ferric oxide. Most of the iron humans mine today comes from that iron oxide, dumped onto the sea floor during a fairly narrow timeframe between about 2.5 and 2.0 Ga.

    Anyway, once most of the ocean’s iron was dumped, the atmosphere could begin to build up waste O2. By about 700 million years ago O2 levels were probably at 15 – 20%, all from cyanobacteria.

  59. @TheBlackCat “Nature doesn’t lie, have biases, try to demonize its opponents, or do any of the untrustworthy things humans do.”

    Unfortunately, nature doesn’t speak directly to us. It is interpreted via human beings who do have biases, do try to demonize their opponents, and do all the untrustworthy things that humans do.

    @BA “This new data comes in the form of geological core samples containing hematite, a mineral that forms either through aerobic processes of bacteria (that is, biology using oxygen) or through photolysis (chemical changes from light) due to sunlight. But that latter happens only near the surface of water, and the hematite in the core samples seem to be from too deep in water to be from photolysis.”

    The main point is that hematite production does not necessarily have to be biological in origin. There is another photochemical mechanism. I’m not sure what the actual evidence is that this hematite formed too deep in water to be caused by photolysis. How do we know at what depth it formed billions of years ago? So the biological argument seems a little weak to me.

  60. Darth Robo

    Always leave it to Tom Marking to start pedantic apologetics.

  61. @Darth Robo “Always leave it to Tom Marking to start pedantic apologetics.”

    Gee Darth, just one more byte and your message might have actual information content.

  62. Also, another strange thing about this precipitated iron from the oceans is that in almost all cases it was deposited in banded formations which means that it turned on, stopped, turned on again, etc. which is very hard to explain. What environmental influences could cause this iron deposition to fluctuate so wildly? There’s probably a great deal about this that is still unknown.

    http://www.galleries.com/rocks/bif.htm

    “Banded Iron Formations are thought to have formed from the precipitation of iron from the Earth’s ancient oceans. Photosynthetic bacteria produced, for perhaps the first time in the young Earth’s oceans, free oxygen which oxidized the dissolved iron that existed abundantly at the time. Oxidized iron is not soluble in water and thus it would precipitate out of the oceans and onto the muddy sea floor.

    For reasons largely unknown, this was a periodic process resulting in the alternating bands of iron oxide and shale. The periodic process might have been due to seasonal fluctuations or storm surges or other hypothesis. Whatever the reason, there never seemed to be a time when the iron layer formation or the shale (mud) formation persisted long enough to produce a layer thicker than 10 centimeters or so.”

  63. Torbjörn Larsson, OM

    Oops, forgot this despite the interesting thread. But better late than never:

    @ IVAN3MAN:

    Yes, I guessed that was the problem. Haven’t happened in a while.

    Reading over it again in a less tired mode, I guess it was the “Hot Spring” ecosystems that set off BA’s spam alarm. Damn, I believe I feel envious of these critters, stuck in their hot, wet clone swamp, dividing their non-existing brains out.

    @ Scott:

    Thanks, I think I actually understand that; and the yo-yo effect seems reasonable to me.

    Also, I believe it may have taken quite a while before plate tectonics got reliably going to soup up CO2 since AFAIU a theory is that both the minerals and the plate seams needs water to be pliable and sufficient lubricated.

    @ Planetologist:

    deposits of organically-derived (isotopically light) carbon were laid down in rocks now found near Isua, Greenland. Layers of graphite at Isua suggest that microbial mats in the photic zone were around at that time

    I believe I saw a very recent (February?) paper that claimed to have rejected the Isua rock evidence by way of inclusions (if that is the right term) into the original rock. That is the current opinion on this?

    or at least it evolved in only one group, ever. I’m actually writing a paper on this topic now, focused on the hypothesis that O2 atmospheres are probably very rare in the universe.

    I don’t understand that reasoning. DNA, nucleated cells, and Hox genes are examples of unique frozen accidents, where the competitors seem to disappear (RNA world/alternate codes, eukaryotes without nucleus or mitochondria) or coexist (fungus).

    Why wouldn’t oxygenic photosynthesis be such? (And if it is complexity that is the argument, for example the current nucleus is rather complicated, no?) I guess I need to wait for the paper, huh? :-)

    I blog about these topics quite a bit

    It is interesting topics to me too, so I will check it out, for sure.

  64. Dov Henis

    Genes, Not Cells, Were Earth’s First Organisms
    And Are Earth’s Primal Organisms
    (a recapitulation)

    A. Pushing back an oxygen-rich atmosphere date

    http://www.sciencenews.org/view/generic/id/41755/title/Pushing_back_an_oxygen-rich_atmosphere

    Hematite crystals in Australian rocks hint that Earth’s atmosphere was oxygenated earlier than previously thought.

    There’s evidence of eukaryotic life, i.e. monocellular organisms with DNA sequestered in a protective nucleus, from roughly 1.9 billion years ago. Multicellular animals appear on the scene much later.

    Large quantities of oxide minerals in rocks around the world indicate that the atmosphere had at least small amounts of oxygen by 2.2 billion years ago. The presence of certain biomarkers in Australian rocks has been hailed as evidence that oxygen-making organisms had evolved by 2.7 billion years ago, but recent studies have cast some doubt on that earlier date.

    Now, analyses of rocks laid down 3.46 billion years ago in what is now Australia push back the oxygen era even further, Hiroshi Ohmoto, a geochemist at Pennsylvania State University in University Park, and his colleagues contend online March 15 in Nature Geoscience.

    B. Earliest single-celled organisms

    (Forwarded) If the 4.6 billion Earth years are compressed into a single year: the Precambrian Era, evolution of first life forms, extends from January 1 to mid-November; the Paleozoic Era, evolution of invertebrates and primitive fishes, extends through the rest of November and part of December, and the Mesozoic, era of dinosaurs, takes up most of the remainder of December. Our time, the Quaternary, would occupy only the last four hours on New Year’s Eve.

    For most of Earth’s history, there were only single-celled organisms. Fossilised single-celled micro-organisms have been found in rocks 3·5 billion years old.

    By 2.4 Ga (gigaannum = 10^9 years) the ratio of stable isotopes of carbon, iron and sulfur shows the action of living things on inorganic minerals and sediments and molecular biomarkers indicate photosynthesis, demonstrating that life on Earth was widespread by then.

    C. Revised fixations that cells were the earliest Earth-life’s organisms, and that tie life’s genesis with organic bio-metabolism

    These fixations dictate that Earth’s earliest organisms were fueled by netabolically self-generated energy.

    But cells were NOT the earliest Earth-life’s organisms. Genes, Not Cells, Were Earth’s First Organisms, And Are Earth’s Primal Organisms.

    Cells are no more organisms than future manned spaceships would be organisms. The innner and outermost cell membranes are multi-functional organs evolved and produced by the organisms that reside within the outermost membrane, as would be the spaceship’s inner and outermost skins-walls produced by their residents, even if the membranes are organic whereas the skins-walls are not. And undoubtedly the capabilities of multi-functional spaceship skins-walls would be far below those of cell’s membranes.

    The primal genes came into being, phased from polymers into replicating beings, organisms, by absorbed sun energy, and proceeded to carry on their life during daylight times, fueled solely by sun energy, and this most probably was the state of life affair until sometime earlier than 3.5 Ga, which is when fossilised single-celled micro-organisms have been found in rocks.

    D. It is thus rationally possible to de-couple life’s genesis and onset of bio-metabolism,

    and to update the comprehension of the nature of Earth life per
    Life’s Manifest

    http://www.the-scientist.com/community/posts/list/112.page#578

    Dov Henis
    (Comments From The 22nd Century)
    EVOLUTION Beyond Darwin 200

    http://www.physforum.com/index.php?showtopic=14988&st=405&#entry396201
    or
    http://www.the-scientist.com/community/posts/list/100/122.page#1407

  65. Pete

    Re intelligent life killing itself off –
    There is a sci-fi novel called “Toolmaker Koan” that posits the theory that intelligence appears to always end up adopting some form of the “us vs them” meme at a global scale, leading to a species-destroying war, thus providing the filter that keeps the galaxy apparently empty of intelligent life.

    Given the vehemence that we’ve seen in defense of cultural memes in the past few decades alone, this hypothesis seems plausible.

    Also on a sci-fi note, Larry Niven has a short story about a meeting with a species that did business with the original intelligent inhabitants of Earth, before the oxygen pollution killed them all….

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