Earth's Oxygen History Could Explain "Darwin's Dilemma" In Evolution 78
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.
A matter of perspective (Score:5, Interesting)
... 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)
... 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.
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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.
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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.
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... 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.
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Maybe it's an oxymoron.
Re:A matter of perspective (Score:4, Interesting)
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.
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Where are all the fossilized robots?
They are your cells. Organic robots are the most cost effective implementation of self-replicating devices on this planet.
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There is fossil record of bacteria back to over 3.5 billion years before present.
Re:A matter of perspective and dice rolling (Score:2)
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The problem with The Magic Soup theory is that over time, all closed systems tend to disorder ...
The "Magic Soup" theory that you're trying to strawman is NOT a closed system. Energy that comes in from sunlight or even just heat = not a closed system. The rest of the post isn't even worth replying to.
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It's not a closed system. Sunlight is being added all the time .
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The problem with The Magic Soup theory is that over time, all closed systems tend to disorder, and the longer the time, the greater the disorder.
So is NYC more or less disordered than 1600? Yes, I know you'll go back to "closed system" but the point is, once life forms are involved, the disorder is thermodynamic, not complexity and structural. A beach, left for 10,000,000 years seems less disorderly than the rocky shore it replaced. Greater order over time. Sort-of.
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And sure, think of me as some wacko, it helps you hold your wrong opinions as fact in your fragile little self-image. Ooh, you proved me wrong and insulted me. You win the Internets. You are obviously deliberately ignorant, and enough people have proven your wrong statements wrong, no need for me to bother.
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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.
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It wasn't until the Cambrian Explosion when the evolutionary branches were viable.
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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
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Alright, maybe reset is extreme, but...
Cause or Contributor? (Score:2)
Re:Cause or Contributor? (Score:4, Insightful)
Re:Cause or Contributor? (Score:4, Funny)
"They are suggesting that higher O2 sparked the explosion"
That sounds logical from the chemists perspective
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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)
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Re:Terraforming (Score:5, Interesting)
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.
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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.
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We will never know.
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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)
Re:Unseen evolution (Score:5, Insightful)
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.
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Also, does "
Explosion took 10 million years! (Score:5, Informative)
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)
Then there is the widely respected alien hypothesis from planet nibiru
Evolution isn't slow (Score:3, Interesting)
which may have been five times the evolutionary rate seen today.
Look up epigenetics, and a few other factors, evolution is not slow.
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I would love to Evolve... (Score:4, Funny)
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!
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Paywall (Score:2)
Why are Paywalled papers still promoted on Slashdot?
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This is a software issue (Score:4, Interesting)
Maybe high O2 led to evolution of hard tissue (Score:4, Interesting)
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.
Snowball Earth (Score:2)
Another leading theory which explains this delay is Snowball Earth [wikipedia.org], a super ice age enveloping the entire surface of the planet.
What about the Plants (Score:2)
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