Scientist suggests life began in freshwater pond, not the ocean
February 14, 2012 by Bob Yirka
(PhysOrg.com) -- For most everyone alive today, it's almost a fundamental fact. Life began in the ocean and evolved into all of the different organisms that exist today. The idea that this could be wrong causes great discomfort, like discovering as an adult that you were adopted as a child. Nonetheless, a team of diverse scientists led by Armen Mulkidjanian is suggesting that very thing; instead of life beginning in deep thermal vents in the ocean, the prevailing view, they say it perhaps instead started in landlocked freshwater pools created by thermal vapor. Their theory is based, as they explain in their paper published in the Proceedings of the National Academy of Sciences, mostly on the idea that the sea is just too salty to provide the ideal conditions necessary to spur life into existence.
Mulkidjanian and his colleagues argue that in looking at the way cells are made today, its hard to imagine they got their start in water that was far saltier than it is now. They point out that cells in all living organisms have a much higher proportion of potassium to sodium, whereas the ocean is the reverse. Such high levels of salt would have made it difficult for cells to synthesize proteins, they say, making it extremely difficult for them the form into the molecular machines with strong walls seen today. Such thick walls would not have existed when cells were just starting to form, making it almost impossible for them to get started, grow and mature.
In contrast, they say, the conditions found on land during the time period when life is believed to have started, was likely far more conducive. In addition to the existing pools of fresh water created by the condensation and cooling of geothermal vapor, there were the higher temperatures that are believed to have existed worldwide. In addition, they say that those pools of water, or mud, likely had many of the same ingredients found in modern cells: phosphate ions, zinc, manganese and especially potassium. Thus the newly forming original cells would not have had to work hard to keep out harmful sodium ions. Also, to counter arguments that newly developing cells on land would be stopped in their tracks by harmful UV radiation from the sun, the team notes that both RNA and DNA have been shown to be stable under such exposure.
Despite the teams compelling arguments, there are likely to be many doubters, and rather than converting most in the scientific community, this new idea is likely to spark debate that will almost certainly continue for many years to come.
More information: Origin of first cells at terrestrial, anoxic geothermal fields, PNAS, Published online before print February 13, 2012, doi:10.1073/pnas.1117774109
Abstract
All cells contain much more potassium, phosphate, and transition metals than modern (or reconstructed primeval) oceans, lakes, or rivers. Cells maintain ion gradients by using sophisticated, energy-dependent membrane enzymes (membrane pumps) that are embedded in elaborate ion-tight membranes. The first cells could possess neither ion-tight membranes nor membrane pumps, so the concentrations of small inorganic molecules and ions within protocells and in their environment would equilibrate. Hence, the ion composition of modern cells might reflect the inorganic ion composition of the habitats of protocells. We attempted to reconstruct the hatcheries of the first cells by combining geochemical analysis with phylogenomic scrutiny of the inorganic ion requirements of universal components of modern cells. These ubiquitous, and by inference primordial, proteins and functional systems show affinity to and functional requirement for K+, Zn2+, Mn2+, and phosphate. Thus, protocells must have evolved in habitats with a high K+/Na+ ratio and relatively high concentrations of Zn, Mn, and phosphorous compounds. Geochemical reconstruction shows that the ionic composition conducive to the origin of cells could not have existed in marine settings but is compatible with emissions of vapor-dominated zones of inland geothermal systems. Under the anoxic, CO2-dominated primordial atmosphere, the chemistry of basins at geothermal fields would resemble the internal milieu of modern cells. The precellular stages of evolution might have transpired in shallow ponds of condensed and cooled geothermal vapor that were lined with porous silicate minerals mixed with metal sulfides and enriched in K+, Zn2+, and phosphorous compounds.
Journal reference:
Proceedings of the National Academy of Sciences
© 2011 PhysOrg.com
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Feb 14, 2012
Rank: 4 / 5 (23)
So?
The Bible also claims that Earth was created before the sun, the Moon and the stars.
And since when did an unsubstantiated claim ever carry any weight?
Feb 14, 2012
Rank: 3.7 / 5 (12)
Feb 14, 2012
Rank: 5 / 5 (7)
The first plants would have been single celled organisms and the first organisms would have been much simpler then plants--or even photosynthetic bacteria. They would have been little more than self-sustaining chemical reactions.
Feb 14, 2012
Rank: 5 / 5 (3)
Feb 14, 2012
Rank: 2.8 / 5 (5)
If one considers a "god" to be any existing being with sufficiently advanced technology, even "divine creation" has probably happened. After all, we already talk about spreading Earth life to other planets.
Feb 14, 2012
Rank: 3.9 / 5 (19)
You mean apart from all the DNA and RNA evidence? The speciation observed in the lab and in nature? That's a wee bit more than 'a bunch of bones'.
http://www.talkor...ion.html
(go to the list of references at the end of the article. That should give you a good starting point to catch up on the state of speciation and evolution)
Feb 14, 2012
Rank: 1 / 5 (5)
Feb 14, 2012
Rank: 4 / 5 (16)
Feb 14, 2012
Rank: 3.9 / 5 (15)
Evolution requires millions of years- you can't expect a person to jump out of a petri dish in a couple of weeks. Creationism precludes the millions of years of transformation by its stance of a 6,000 year old earth. You just walked into a biker bar wearing a sequined thong.
Feb 14, 2012
Rank: 1 / 5 (13)
Can't be that hard to go through all the possible combinations..can it??????
Feb 14, 2012
Rank: 3.7 / 5 (15)
This is a science site. Moderators, surely we don't have to suffer through walls of religious spam here? And it is spam, being completely irrelevant to both the topic and to the nature of the site as a whole.
Feb 14, 2012
Rank: 3.4 / 5 (10)
Feb 14, 2012
Rank: 5 / 5 (1)
Does a scientific article really need such trite pap as an introduction? I'm sure those weren't Mulkidjanian's words.
All it does is serve to bolster the anti-science purveyor's views of rigidity and dogmatic thinking and how dare anyone ever challenge what a kid might have read in a book fifty years ago!
The scientific reality, of course, is very different, where all kinds of ideas are challenged all the time. This type editorialized reporting which manufactures controversy is a disservice to science.
Feb 14, 2012
Rank: 5 / 5 (1)
Even the deep seas, near hydrothermal vents, may not have been too salty for life. Most of the minerals from them, at least today, seem to be compounds of heavier metals.
Feb 14, 2012
Rank: 3.4 / 5 (5)
Ugh...haven't we gone over this enough? Science emphatically does not have to prove anything. It demonstrates evidence and comes up with theories that best fit that evidence. Evolution is as "proven" as gravity, the periodic table of elements, or that pi is an irrational number.
Feb 14, 2012
Rank: 4.2 / 5 (10)
You're correct, but for the wrong reason. Evolution wasn't a factor in the origin of life. It became important afterwards, once life took hold.
It's not just a chemical mix, other contributing factors are likely just as important - environmental conditions, energy gradients, mechanical agitation, etc.
Given that we don't know the exact conditions on early earth - the exact environment or the exact physical process taking place, it's little wonder that the few research labs that actually try to do this type of work (generally for short periods of time) have not duplicated life as we know it. The search space is vast, to say the least.
Nevertheless, progress is being made, from understanding the minimum genome for life, to prebiotic chemistry, replicating molecules, lipid/vesicle formation to artificial life and genomes.
Feb 14, 2012
Rank: 2 / 5 (4)
It absolutely can. That's why understanding the areas I've mentioned above will help us to refine and narrow the vast search space.
Feb 14, 2012
Rank: 3.8 / 5 (4)
Feb 14, 2012
Rank: 3.9 / 5 (7)
Life appears to have taken many millions of years to start, in a planet-sized experiment.
Yes, it it would be ridiculously hard to try all of the possible combinations of chemistry. Read up on combinatorics and try the math.
However science has numerous times recreated likely combinations of chemicals and events on a tiny scale, and in doing so they have often produced many of the key building blocks of life.
So there must be many, many combinations of chemicals and energy sources that create such building blocks.
Even the next step of concentrating the building blocks and providing a scaffold for them appears to be accomplished by clays, by mica, by pyrites, by lipid bubbles, and by white-smoker hydro-thermal vents, and probably many other means yet to be discovered.
Feb 15, 2012
Rank: 3.4 / 5 (5)
Feb 15, 2012
Rank: 2.6 / 5 (7)
Feb 15, 2012
Rank: 3 / 5 (4)
Feb 15, 2012
Rank: not rated yet
@ nkalagana:
The problem with Monod's "improbable accident" as I understand it, is that it doesn't resemble any stochastic process it speaks about. It sounds more like a model of a vast revisited phase space with a small volume for success.
In a stochastic process sense, the short time to observed first life as well as the predicted average times of diverse abiogenesis scenarios speaks of an easy, frequent and/or successful process. So it would be expected to happen a lot.
After that evolution is contingent, and traits like technological intelligence expected to be exceedingly rare according to most biologists.
Feb 15, 2012
Rank: 1.8 / 5 (10)
Feb 15, 2012
Rank: 3 / 5 (6)
[Religious trolling]
The rest of your comment concerns modern life. The paper is research on chemical to biological evolution prerequisites and the pathways up to "emergence of
ion-tight phospholipid membranes."
@ mmead:
Science is not math, it can't be "proven" from assumed axioms since nothing can be assumed. It is based on observation and testing to reject that which isn't the case and which doesn't work.
Biological evolution, which this research doesn't concern as much as prerequisites for chemical evolution, is the best observed fact and its theory the best tested in all of science due to its ubiquiteness and complexity. The most important 30 evidences is described here.
Feb 15, 2012
Rank: 3 / 5 (4)
Actually, evolution has been observed both in the lab and in the wild and has multiple converging series of evidence from genetic rates of change, archaic structures, to detailed fossil records, radiocarbon evidence, confirmed prediction and predictable consequences. The mechanisms and code by which life evolves have been found (mutations DNA, RNA) even though early evolutionists had no such data to go on, they posited the mechanism and it was found. Gravity, by comparison is much more mysterious.
Feb 15, 2012
Rank: 2.3 / 5 (3)
HTML fail. I'm sure you have been told of Talkorigins, head over there and look up Theobald's review of what evidence the science is based on.
Feb 15, 2012
Rank: 1 / 5 (1)
Feb 15, 2012
Rank: 4 / 5 (4)
Please revisit your textbooks. The theory of evolution says nothing about how life gets started. It is solely concerned with how life develops thereafter.
Feb 15, 2012
Rank: 5 / 5 (3)
The trite answer, which already Darwin understood, is that yesterdays organics is todays nutrient. That which formed the first life is used as food today by already existing life, and small molecules will be scavenged before they can build complexity.
More generally, the environment has changed. Chemical evolution needs redox potentials (which later is reproduced in cells during metabolism), and there is much less of them today, fewer heat sources like hydrothermal vents. Most importantly, the modern oxygen atmosphere is a poison for biochemicals and the primordial chemical pathways, the chemicals oxidate quickly and pathways are blocked or diverted.
Feb 15, 2012
Rank: 1 / 5 (2)
I was merely just bringing it down to the start which matters more if you want to convert everyone.You can't really discuss evolution and say so much without understanding the start.
Feb 15, 2012
Rank: 3 / 5 (2)
There are experiments that show you can get complex basic organic compounds (amino acids) from rather simple processes (something we think the ur-atmosphere looked like and an arc of lightning)
But if you think we can already exhaustively replicate all that a planet size laboratory was effectively undergoing for several billion years until the lucky moment happened - then you might think again.
Feb 15, 2012
Rank: 5 / 5 (1)
DNA is not "a protein chain"
Feb 15, 2012
Rank: 5 / 5 (1)
Just a slight correction AP, the 'lucky' moment (I assume you mean first life) didn't take several billion years to occur, but somewhere in the region of 750 million years after earth's formation.
Feb 15, 2012
Rank: 5 / 5 (2)
...if it happened on Earth at all. That's still one of the unknowns. We already know that amino acids are out there in the universe. So who knows where it all started?
http://www.univer...-sample/
Some theories state that life formed in the deep like the bacteria living on radiation. This could have happened even before the planet acquired oceans.
http://www.scienc...ys.shtml
Even if we can replicate a startup self-replicating protein/prion in the lab that won't be any conclusive proof as to whether it started here or not. (Though it would be enormously helpful in establishing THAT it can happen - apart from the obvious technological applications)
That's the thing with singular events: You can simulate them, but as long as you didn't observe them having conclusive evidence is almost impossible to come by.
Feb 15, 2012
Rank: not rated yet
Sure, but there is no reason why the simplest credible possibility should not be the frontrunner. Either way, it doesn't negate the timeline of when earth's first organisms appeared (or at least left traces of their existence).
The law of parsimony works best when considering varied possibilities, until evidence to the contrary is found.
Feb 17, 2012
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Feb 19, 2012
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Feb 19, 2012
Rank: 5 / 5 (1)
Since we're looking at organic molecules I don't know why there should be self repliating inorganic molecules (remember: 'organic' just means 'contains carbon' - nothing more)
As for organic self replicating stuff: Prions would classify.
Feb 19, 2012
Rank: 5 / 5 (1)
Feb 24, 2012
Rank: 1 / 5 (1)
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