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Earth Science

Earth's Oxygen History Could Explain "Darwin's Dilemma" In Evolution 78

Posted by timothy from the you-expected-a-straight-line-on-the-graph? dept.
TaleSlinger (3080869) writes Scientists following two different lines of evidence have just published research [Here's the abstract to the paywalled Science paper] that may help resolve "Darwin's dilemma," a mystery that plagued the father of evolution until his death more than a century ago. Life appeared when the earth was tens of millions of years old, but evolution didn't go into high gear until the "Cambrian Explosion", nearly a billion years later. The two papers propose complementary theories that help explain this. The first suggests that scientists have long overestimated the amount of oxygen in the earth's atmosphere in the pre-Cambrian era just before the "explosion." The second suggests suggests that very dramatic changes driven by the tectonic breakup of the so-called "supercontinents" of the pre-Cambrian era could have caused an extraordinary leap in oxygen levels of both the ancient oceans and the earth's atmosphere. These two studies fit neatly together, suggesting that a world deprived of oxygen could have changed relatively quickly into an incubator for new life in shallow ponds spread across the continents and fed by waters rich in nutrients. Perhaps that set the stage for the explosion, which may have been five times the evolutionary rate seen today.
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Earth's Oxygen History Could Explain "Darwin's Dilemma" In Evolution More

Earth's Oxygen History Could Explain "Darwin's Dilemma" In Evolution

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  • A matter of perspective (Score:5, Interesting)

    by jandersen ( 462034 ) on Tuesday November 11, 2014 @10:46AM (#48359635)

    ... evolution didn't go into high gear until the "Cambrian Explosion", ...

    I'm not sure I believe that - one could reasonably argue that the growth in complexity from a soup of ribozymes to the first cell, was comparable to the leap from single-celled organisms to multicelled; or possibly far more involved than that. Another major leap was from prokaryotes to eukaryotes, a necessary precondition for (most) multicelled life, it would appear. What happened at the Cambrian explosion was probably just that now the organisms got big and touch enough to leave fossils.

    • Re:A matter of perspective (Score:5, Interesting)

      by fuzzyfuzzyfungus ( 1223518 ) on Tuesday November 11, 2014 @11:35AM (#48360065) Journal

      ... evolution didn't go into high gear until the "Cambrian Explosion", ...

      I'm not sure I believe that - one could reasonably argue that the growth in complexity from a soup of ribozymes to the first cell, was comparable to the leap from single-celled organisms to multicelled; or possibly far more involved than that. Another major leap was from prokaryotes to eukaryotes, a necessary precondition for (most) multicelled life, it would appear. What happened at the Cambrian explosion was probably just that now the organisms got big and touch enough to leave fossils.

      There seems to be an interplay between 'growth in complexity' and 'diversification' at work. It is undeniably the case that hammering out the basics of metabolic chemistry, and various other low-level-but-absolutely-life-critical stuff took a long time, and that it was one hell of a jump from 'glorified catalytic processes' to 'life as we know it'; but if you are looking at diversity as well as complexity, the massive increase in weirdo multicellular organisms made possible only by high powered aerobic metabolism (along with the large number of new niches for symbiotes and parasites that this created) was also very big news.

      • along with the large number of new niches for symbiotes and parasites that this created

        It isn't just "symbiotes and parasites". When virtually everything is a new niche with little competition, you're going to see explosion.

      • There were eukaryotes and photosynthesis by 3 billion years before present. They became slowly more sophisticated but nothing fundamentally new happened until about 700 million years bp.

    • ... evolution didn't go into high gear until the "Cambrian Explosion", ...

      I'm not sure I believe that - one could reasonably argue that the growth in complexity from a soup of ribozymes to the first cell, was comparable to the leap from single-celled organisms to multicelled; or possibly far more involved than that. Another major leap was from prokaryotes to eukaryotes, a necessary precondition for (most) multicelled life, it would appear. What happened at the Cambrian explosion was probably just that now the organisms got big and touch enough to leave fossils.

      Bingo. I always assumed we had a billion years of creating a massive set of genes and proteins that would be used later on, and at some point (the Cambrian Explosion) that complexity had reached a tipping point. Your normal bacterium is awesomely complex, but doesn't leave a lot of fossils laying around.

      • Maybe it's an oxymoron.

      • Re:A matter of perspective (Score:4, Interesting)

        by SydShamino ( 547793 ) on Tuesday November 11, 2014 @12:52PM (#48360879)

        Sort of how the 200 years or so of computer development up to the point of Singularity showed tremendous advances in computer science and engineering, and yet, once the machines are sentient, the wild diversity of the quintillions of robot that spread through the galaxy will represent the majority of the fossil record - especially after most of the old PCs of Earth have subducted.

      • There is fossil record of bacteria back to over 3.5 billion years before present.

    • It all helps each other. Creationists always hold that the chance is too small for evolution to happen by chance. Others like to point out that over a long enough time span, if you get to keep the winning dice rolls (advantages) it is inevitable. I always think of these gaps like that. Long enough time spans. Thou it does seem that evolution when it starts to happen happens in relatively fast spans. Usually do to a change. Also maybe there was a lifeform, bacteria that produced oxygen as waste.

    • Re: (Score:2)

      by Sique ( 173459 )
      What is much more interesting (and widely underreported) is that the Cambrian Explosion was neither an explosion -- we had the Ediacara fauna before --, nor was the Ediacara fauna the first multicellar life on earth.

      There have been multicellar livings before, like the Gabonionta [wikipedia.org], about 2.1 billion years ago, which existed for about 200 million years and have died out again.

      • Re: (Score:2)

        by AK Marc ( 707885 )
        Sounds more like an explosion of life pre-cambian, but that the life that came about was evolutionary dead-ends, and died out under pressure from future life forms.

        It wasn't until the Cambrian Explosion when the evolutionary branches were viable.

        • Re: (Score:2)

          by Sique ( 173459 )
          The thesis was that after the Great Oxygenation Event 2.1 billion years ago, multicellular life appeared, but when the oxygen levels sank again, it died out without leaving traces. So it was not pressure from future life forms, but from the abiotic conditions that caused the dead-end.

          The banches of life appearing during the Franceville era weren't less viable than the ones appearing in the Ediacara fauna. If oxygene levels today would drop below 10%, multicellular life would probably be as endangered than

          • Re: (Score:1)

            by dkman ( 863999 )
            If the hot air wind-bags go first I'm all for hitting that reset button. You know who I'm talking about slashdot.

            Alright, maybe reset is extreme, but...
  • I don't see a logical basis for claiming low O2 "sparked" a diversification explosion directly. However, those species with the greatest ability to adapt likely survived the earth's various challenging periods, including this one, and what remained after each were a higher proportion of species with inherently advanced genetic ability to adapt/change/diversify. The low O2 period may have just been the tipping point.

    • Re:Cause or Contributor? (Score:4, Insightful)

      by Muros ( 1167213 ) on Tuesday November 11, 2014 @11:06AM (#48359803)
      I think you missed the point there. Low O2 was the norm until the Cambrian explosion. They are suggesting that higher O2 sparked the explosion, as it opened up new ways for plant and animals to metabolize.

      • Re:Cause or Contributor? (Score:4, Funny)

        by Anonymous Coward on Tuesday November 11, 2014 @11:23AM (#48359957)

        "They are suggesting that higher O2 sparked the explosion"

        That sounds logical from the chemists perspective

      • Thanks, I misread that. My point still stands to some extent, and it certainly makes sense that life would thrive when the conditions for it became more favorable.

        • Re: (Score:2)

          by dave420 ( 699308 )
          If by "some" you mean "no", then yes, your point still stands to some extent.
          • So, you think there is zero merit to the idea that 'adaptability' is a favorable genetic trait that would provide a greater advantage during 'challenging' earth periods. OK.

      • So did the oxygen simply appear out of nowhere (he asks rhetorically)? Of course not. If it was somehow trapped in the oceans or underground, and then released as postulated by these papers, then one must explain the mechanism that would have dissolved and/or trapped the O2 to start with. What was different about Pre-Cambrian oceans that allowed for more oxygen to be dissolved in it than modern oceans? What caused the release and the change to what we have now? Likewise, what mechanisms in tectonic plate

  • Terraforming (Score:3, Funny)

    by sinij ( 911942 ) on Tuesday November 11, 2014 @10:52AM (#48359681)
    More you read about this, more it looks like terraforming. Sure, it all could have happened by chance, but if I was a spacefaring civilization trying to turn Mars-with-water planet into something more suitable for life this is how I would likely do it.

    • Re:Terraforming (Score:5, Interesting)

      by gurps_npc ( 621217 ) on Tuesday November 11, 2014 @11:05AM (#48359797) Homepage
      1) Yes this looks like terraforming - the process of taking a lifeless world and making it suitable for life.

      2)That in no way at all implies aliens did it because....

      3)All living worlds (hopefully Earth is just one of many) start out as lifeless and then develop life. So all living worlds MUST undergo terraforming.

      4) If aliens did it, it would have taken a LOT LESS time then it did. These studies pretty much prove your wrong about aliens doing it.

      Whens starting up, a living world's major problem is fuel. It's very hard to eat generic dirt and gasses. So first they need something that can take whatever inorganic raw materials exist and transform it into something more easily digestible. That means taking the atmosphere and turning it into oxygen rich (or whatever other gas the complex life needs) and taking inorganic dirt and turning it into organic fertilizer (i.e. manure). Then more complex life can come along and live off the manure and atmosphere. Then once life fills the planet, multi-celluar life forms can come along and start eating the single celled life forms, which has become good food.

      That is how life takes over a world naturally. Intelligence simply speeds up the process, it doesn't change it.

      • 1) Yes this looks like terraforming - the process of taking a lifeless world and making it suitable for life.

        2)That in no way at all implies aliens did it because....

        "Terraforming", even when used erroneously to imply planets being made other than like our planet, implies intelligent intervention.

      • Comment removed based on user account deletion

    • https://www.youtube.com/watch?... [youtube.com]

      https://www.youtube.com/watch?... [youtube.com]

      Excellent film, if you can get over the cheesy special effects.

  • Unseen evolution (Score:5, Interesting)

    by Roodvlees ( 2742853 ) on Tuesday November 11, 2014 @10:56AM (#48359717)
    Or there was plenty of evolution before this 'explosion', but we don't see fossils of that time because the animals had such soft bodies that don't fossilize well.

    • Re:Unseen evolution (Score:5, Insightful)

      by lgw ( 121541 ) on Tuesday November 11, 2014 @11:54AM (#48360259) Journal

      Or there was plenty of evolution before this 'explosion', but we don't see fossils of that time because the animals had such soft bodies that don't fossilize well.

      Sorry, you just don't get that much size happening with anaerobic microbes (I guess it's possible there were larger fungi - we know so little about fungi anyhow), but there's still plenty of complexity in bacteria. There was a vast amount of evolutionary "work" to get from the RNA sea (or however things started) to bacteria, which today are really quite complex and diverse despite being single-celled. But the major milestone was cyanobacteria.

      Once cyanobacteria got going, poisoning the air with deadly oxygen, the doom of almost every other species was written. The Oxygen Catastrophe, [wikipedia.org] was the largest extinction event that we're sure happened. From 2.5 to just under 1 billion years ago, they poured Oxygen into the air, but O2 levels didn't rise much - this is the mystery. One theory is tectonic, as mentioned in TFS, another is the "nickel famine": methane reacts with O2, leaving CO2 and water, so if something happened to the methane-producing bacteria (which need nickel as a catalyst) you'd get a sharp rise in O2.

      For whatever reason, O2 spiked, nearly every species died, and the slate was wiped clean. On the up side,O2-based metabolisms have so much more energy available, it opened the door to complex multicellular life.

    • If that were the case it would suggest that with all soft-bodied evolution going on, only a select few species evolved into fossilizable life forms. Seems unlikely (albeit entirely possible) that evolution was constant before and after the cambrian explosion yet we see a huge increase in diversity after the CE. If evolution was constant, an even distribution of lifeforms should have become fossilizable (theres that word again!) and the record would show the CE had a more diverse starting point.

      Also, does "

  • Explosion took 10 million years! (Score:5, Informative)

    by 140Mandak262Jamuna ( 970587 ) on Tuesday November 11, 2014 @11:06AM (#48359813) Journal
    First off the term "explosion" is in geological time scale. 10 million years is a blink of an eye in that scale. But in reality it is TWO THOUSAND times the length of the recorded history, 50 times longer than the life of Homo sapiens...

    Second lack of evidence is not the evidence of lack. Before the Cambrian "explosion" the organisms had not developed bones and shells that would fossilize. It is very hard for soft bodies to fossilize and for the indirect evidence to stick around. There are very few places where the original primordial earth crust still survives without change. Almost the entire seafloor is new. Constantly being melted into the magma in the subduction zones and being reformed in the expansion zones. No evidence of anything would survive that. So it is totally incorrect to say that earth was not teeming with life or that the competition was absent.

    Today multi-trillion cell agglomerations are sitting on keyboard and typing follow up responses to pointless postings in slashdot. Many trillion cell colonies of micro organisms live symbiotically with these agglomerations which call themselves human. Trillions of these cells commit suicide promptly when the signal arrives, to be replaced by new copies. They know they are not in the gonad and they will never reproduce. Still they all tick along doing their stuff. The foundations for such a way of life for these cells were laid down before the Cambrian "explosion".

    And we become time traveling mind readers and state confidently "Darwin was plagued by the mystery...". Darwin was constantly complaining of so many illnesses he was such a strain on Emma. He had lot more than a mystery plaguing him.

  • Aliens (Score:1)

    by Anonymous Coward

    Then there is the widely respected alien hypothesis from planet nibiru

  • Evolution isn't slow (Score:3, Interesting)

    by koan ( 80826 ) on Tuesday November 11, 2014 @11:09AM (#48359831)

    which may have been five times the evolutionary rate seen today.

    Look up epigenetics, and a few other factors, evolution is not slow.

    • Or just ask bacteria about it. Between plasmid transfer and dividing as often as several times an hour, those sneaky little bastards evolve like nobody's business.

  • I would love to Evolve... (Score:4, Funny)

    by Dareth ( 47614 ) on Tuesday November 11, 2014 @11:09AM (#48359833)

    I would love to Evolve...but every time I try, these hunters show up and try to lock me into a mobile arena. It is seriously annoying!

  • Why are Paywalled papers still promoted on Slashdot?

  • This is a software issue (Score:4, Interesting)

    by Arnold Reinhold ( 539934 ) on Tuesday November 11, 2014 @12:22PM (#48360555) Homepage
    The Cambrian explosion is more likely explained in terms of genetic software. At some point, a collection of genes evolved that could reliably control and pass on complex growth patterns. Before those existed, multi-cell organisms had very simple forms and limited functionality. Once that morphological operating system was in place, a vast variety of organisms could evolve.

  • Maybe high O2 led to evolution of hard tissue (Score:4, Interesting)

    by tyme ( 6621 ) on Tuesday November 11, 2014 @12:38PM (#48360727) Homepage Journal

    Rather than sparking rapid evolution, maybe the high O2 concentrations led to (or allowed) the development of hard tissue in existing complex organisms. Ocean acidification dissolves the shells of clams, corals, etc. [whoi.edu] and increased O2 levels could coincide with decreased CO2 levels (probably because the organisms creating all the O2 had to get it from somewhere).

    This being Slashdot (and the link being paywalled) I have not bothered to read the linked article. Hell, I've barely bothered to read the summary.

  • Life appeared when the earth was tens of millions of years old, but evolution didn't go into high gear until the "Cambrian Explosion", nearly a billion years later.

    Another leading theory which explains this delay is Snowball Earth [wikipedia.org], a super ice age enveloping the entire surface of the planet.

  • There's still a big problem that low oxygen concentration does not solve.
    If life began 4 billion years ago...
    And first photosynthesis goes to 3.2 billion.
    Imagine then a long period of low O2 until
    Precambrian explosion 500 million years ago...
    First land plants 450 million years ago.
    Why couldn't land plants have evolved much much sooner? The complex bodyplans
    of animals are not required for the development of large plant life.
    My guess is that two things limited life early on, cold temperatures and dangerous UV

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