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Earth's Oxygen History Could Explain "Darwin's Dilemma" In Evolution
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.
... 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.
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.
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.
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.
Thank you, Bradley Manning, Edward Snowden and so many others, for courageously defending humanity, my freedom and more!
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.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Then there is the widely respected alien hypothesis from planet nibiru
which may have been five times the evolutionary rate seen today.
Look up epigenetics, and a few other factors, evolution is not slow.
"If any question why we died, Tell them because our fathers lied."
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!
I only look human.
My mother is a halfling and my dad is an ogre, so that makes me an Ogreling
Why are Paywalled papers still promoted on Slashdot?
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.
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. 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.
just a ghost in the machine.
Another leading theory which explains this delay is Snowball Earth, a super ice age enveloping the entire surface of the planet.
Ceci n'est pas une signature.
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
radiation.
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.
Sounded like someone combined notes from a scientific lecture on the history of the earth with a "young earth" creationist's history of the earth.
A Shadeless room is a brighter room.
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.
It's not a closed system. Sunlight is being added all the time .
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.
Learn to love Alaska
You haven't defined "the system" but will change that definition whenever it suits you to prove your point.
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.
Learn to love Alaska