Life origins problem

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Paranoid__Android
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Re: Life origins problem

Postby Paranoid__Android » Thu Jan 26, 2012 9:22 pm UTC

The whole point of the experiment was to get a self replicator from nothing. I don't see why people are going on about finding different ones... I mean who cares? I'm sure there are many ways that it would work but the amazing thing would be to simply get 'life' from no life.
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Re: Life origins problem

Postby thoughtfully » Thu Jan 26, 2012 9:48 pm UTC

It's obvious, isn't it? Run a simulation.. can't get a better controlled environment than that :)
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Re: Life origins problem

Postby yurell » Thu Jan 26, 2012 10:24 pm UTC

thoughtfully wrote:It's obvious, isn't it? Run a simulation.. can't get a better controlled environment than that :)


Except the Evolutioists and Darwinists will twerk the parameters to get the answers they want, so there's no chance of getting a fair and balanced result out of such a simulation.
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Re: Life origins problem

Postby mfb » Thu Jan 26, 2012 10:48 pm UTC

Scyrus wrote:for example, if the probability of life forming on Earth were extremely small EVEN taking into account the time span, it could suggest an external factor

Like... life that formed elsewhere? Why do you think the probability is higher there?
Technically, it is right that panspermia is more likely if the formation of life is less likely, but life has to evolve at least somewhere. Maybe you can gain a few orders of magnitude (I doubt that it is more than 1). But not enough to make any difference with the current knowledge.

Concerning the RNA evolution experiment: Is there any organic molecule which survives superheated water at, say, 1000°C? If not: Is it possible to build the RNA building blocks from the elements and heat-resistant catalytic converters?
I think that "heat everything up until everything organic is gone" can work, the tricky part is to assemble the organic molecules inside afterwards.


Evolutioists and Darwinists

Did you mean "Gravitationalists"?
Or just "Scientists"?

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Re: Life origins problem

Postby Gigano » Thu Jan 26, 2012 10:59 pm UTC

mfb wrote:
Scyrus wrote:for example, if the probability of life forming on Earth were extremely small EVEN taking into account the time span, it could suggest an external factor

Like... life that formed elsewhere? Why do you think the probability is higher there?
Technically, it is right that panspermia is more likely if the formation of life is less likely, but life has to evolve at least somewhere. Maybe you can gain a few orders of magnitude (I doubt that it is more than 1). But not enough to make any difference with the current knowledge.


During an astrobiology course I took last year I heard a pretty convincing argument against panspermia: time. Since the beginning of the universe there probably hasn't been enough time to allow the evolution of (pre-)life elsewhere in the universe and the traversing of what is most likely an enormous distance between the planet of origin and the earth. Given enough time it probably will happen, but insufficient time has gone by to make it a likely scenario.

mfb wrote:Concerning the RNA evolution experiment: Is there any organic molecule which survives superheated water at, say, 1000°C? If not: Is it possible to build the RNA building blocks from the elements and heat-resistant catalytic converters?
I think that "heat everything up until everything organic is gone" can work, the tricky part is to assemble the organic molecules inside afterwards.


Sterilisation indeed should be heavily applied. When creating LB medium, a growth medium for bacteria, we dissolve various organic (yeast extract and tryptone) and inorganic (sodium chloride) compounds in water and autoclave it; this means sterilisation at high pressure and 121°C for 15 minutes. This nullifies the possibility of any contaminants spoiling the medium.

Considering 1000 degrees as a sterilisation temperature might not work however. Most organic molecules will be obliterated well before reaching that temperature, even the most simple ones. One one of the nucleotide bases, adenine, disintegrates at temperature above around 350°C, and I reckon it is quite essential for some form of life to emerge, at least life that resembles life on earth. As I recall, the Miller-Urey experiment demonstrated that from the most simple chemicals you can produce organic compounds. So assuming after such high temperature sterilisation you have a bunch of simple non-organic compounds and the right catalysts to kick in organic chemistry, I think it's feasible to do it.
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Re: Life origins problem

Postby webgiant » Fri Jan 27, 2012 2:24 am UTC

Paranoid__Android wrote:I know this topic has been discussed before but this is a differnet angle on it that is concerning me. I was reading an article about RNA and how strands have been fabricated that can duplicate other RNA molucules, thus giving credability to the hypothesis that life originated from RNA moluclues (maybe forming in undersea vents, primeval soup ect.).
However the RNA molucule fabricated was 198 bases long. So for this to form randomly 198 bases would have to randomly assemble themselves in the right order.
Now this molucule wont even replicate itself, I'm assuming that one that could hypothetically do this would need to be longer and not shorter.

Now this is my resoning, please correct me if you think an estimate is wrong or my maths is faulty.
For 198 bases to randomly assemble (by randomly adding a base to the end of a chain) from an abundant supply of the 4 constituent bases you'd have a (1/4)^198 = 1 / 6.2x10^120 chance of getting the correct outcome. (is this right?)

...
...

This means that over the 500 million years there are 1.55x10^17 x 5.14x10^16 = 7.97 x 10^33 trials to get the right combination. This falls FAR FAR short of the 6.2x10^-120 chance of getting the right result.

Surely these probabilities mean life forming through this method or other similar methods is pretty much statistically impossible.
Does this mean life must have come from outer space?

Edit: surface area of a sphere is not 4pi x r :/

Most people botch probability math. You are no different. The math is actually good, but the conclusion is wrong.

A probability is not the number of trials required to produce the event, it is the percentage chance that any given trial will produce the desired result. Thus the first trial can result in the event occurring.

Take five coins. There are 2^5 possible outcomes, total 32, one of which is all heads. This does not mean that you have to toss the coins 32 times to achieve the result of all heads. Sometimes you will hit it in 1. Sometimes in 4. Sometimes you won't hit it at all. While the percentage chance of getting all five heads with five coins is 3%, this is the percentage chance per trial, not overall.

Putting "statistical impossibility" in perspective, it is statistically impossible to win the lottery with one ticket, yet people win the lottery with one ticket. The percentage is per trial, not overall.

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Re: Life origins problem

Postby Gigano » Fri Jan 27, 2012 6:11 pm UTC

webgiant wrote:A probability is not the number of trials required to produce the event, it is the percentage chance that any given trial will produce the desired result. Thus the first trial can result in the event occurring.

Take five coins. There are 2^5 possible outcomes, total 32, one of which is all heads. This does not mean that you have to toss the coins 32 times to achieve the result of all heads. Sometimes you will hit it in 1. Sometimes in 4. Sometimes you won't hit it at all. While the percentage chance of getting all five heads with five coins is 3%, this is the percentage chance per trial, not overall.


This may drift into semantics pretty quickly, but probability actually tells us how many percent of a number of trials will turn up with a particular result. In your example of five coins turning up heads all at once, in 3% of an n number of trials, the result will be five coins heads. Yes, in a sense the odds of five coins turning up heads at the beginning of each trial is roughly 3%, but that doesn't really mean anything on itself. It just means that it is unlikely to happen since there is a higher chance (97%) something else will happen.
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Paranoid__Android
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Re: Life origins problem

Postby Paranoid__Android » Fri Jan 27, 2012 8:34 pm UTC

webgiant wrote:Most people botch probability math. You are no different. The math is actually good, but the conclusion is wrong.

A probability is not the number of trials required to produce the event, it is the percentage chance that any given trial will produce the desired result. Thus the first trial can result in the event occurring.

Take five coins. There are 2^5 possible outcomes, total 32, one of which is all heads. This does not mean that you have to toss the coins 32 times to achieve the result of all heads. Sometimes you will hit it in 1. Sometimes in 4. Sometimes you won't hit it at all. While the percentage chance of getting all five heads with five coins is 3%, this is the percentage chance per trial, not overall.

Putting "statistical impossibility" in perspective, it is statistically impossible to win the lottery with one ticket, yet people win the lottery with one ticket. The percentage is per trial, not overall.


I know this. What I meant by statistical impossibility is it is so unlikely to happen within that time frame that it's pretty much impossible. I know it is possible to happen at every consecutive trial with the same probability of getting a success.
If I tried to toss 20 heads in a row with but only two attempts, it would be possible, but unlikely enough to discount as statistical improbable due to the limited number of trials.

On the topic of the experiment.

Would it be possible to manufacture a giant steel container which the organic matter could be dumped into. Then sealing it (by welding a lid on?). Then heating it to roughly 300C, thus causing all bacteria to die, also any leftover RNA ect. would be destroyed as the bond strength wouldn't be as high as thermal vibrations. As it's now sealed and airtight with no bacteria alive in it, it can be left for however long is necessary.

As for detecting any self-replicators would it be possible to construct some kind of sample retrieval mechanism to retract samples from the tank for analysis every so often? maybe a grid of syringes that drops down into the solution?
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Re: Life origins problem

Postby PossibleSloth » Fri Jan 27, 2012 11:00 pm UTC

You can't really determine the probabilities without knowing both the number of planets in the universe capable of supporting life, and the percentage of these on which biogenesis has occurred. If there are 10^20 planets in the universe capable of supporting life, the odds of life spontaneously arising on one of them is significantly higher.

Personally I think the odds of self-replicating RNA arising are better than you think.

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Re: Life origins problem

Postby Interactive Civilian » Mon Jan 30, 2012 2:55 am UTC

Gigano wrote:During an astrobiology course I took last year I heard a pretty convincing argument against panspermia: time. Since the beginning of the universe there probably hasn't been enough time to allow the evolution of (pre-)life elsewhere in the universe and the traversing of what is most likely an enormous distance between the planet of origin and the earth. Given enough time it probably will happen, but insufficient time has gone by to make it a likely scenario.

I'm curious about the numbers they gave... Because the universe is about 15 billion years old, ~10 billion-ish when the Solar system began to form, and current understanding of life on Earth is about 300 million years from the end of heavy late bombardment (and thus a stable enough planet) to the first fossil evidence of life (so from about 4.1Gya to 3.8 Gya). 300 million years is not much compared to 10 billion, and it seems to me that once life got started, the billion year time scales for it to drift would be sufficient. Also, assuming abiogenesis it is not known how much of that 300 million was spent in the transition from geochemistry to biochemistry and then how much of it was early cellular life growing enough to leave evidence behind in the fossil record. Did it take 299 million years to form and then 1 million years to spread? The opposite? or more likely somewhere in between?

Of course, if it was panspermia then those estimates become moot and may not apply at all to how long it would take for the origin of panspermia based life forms. But I am not aware of any other models to apply.

Granted, I'm not convinced of panspermia, and believe it rather unlikely as well, though I won't really decide one way or another until extra-terrestrial life is found and what its biology implies about the issue. However, it seems to me that the time-scale issue doesn't make sense. However, I do admit that it is kind of hard to conceive things like the numbers of years and the size of the universe to get a feel for the actual likelihood of primitive cells drifting across space. :)

(I'm pretty firmly in the abiogenesis camp; while the models are not complete, the chemistry and physics of some of the models make sense, as well as the ubiquity of precursor biomolecules in the universe [complex organic molecules seem to form easily enough in abiotic conditions])


[edit]
Paranoid__Android wrote:Would it be possible to manufacture a giant steel container which the organic matter could be dumped into. Then sealing it (by welding a lid on?). Then heating it to roughly 300C, thus causing all bacteria to die, also any leftover RNA ect. would be destroyed as the bond strength wouldn't be as high as thermal vibrations. As it's now sealed and airtight with no bacteria alive in it, it can be left for however long is necessary.

Just out of curiosity, is your experimental design to just have this soup sit there and see if it reacts? Because I am not aware of any model of abiogenesis which suggests this was the case, and no scientist argues that it was. In fact, the best (well, in my humble opinion) or at least the most complete, provides a constant energy source and source of raw materials, as well as inorganic catalysts and a mechanism for concentrating the compounds. I am, of course, referring to the Alkaline Hydrothermal Vent hypothesis championed by Martin & Russell, citation provided:

Martin, W. & Russell, M.J., 2003. On the origins of cells: a hypothesis for the evolutionary transitions from abiotic geochemistry to chemoautotrophic prokaryotes, and from prokaryotes to nucleated cells. Philosophical transactions of the Royal Society of London. Series B, Biological sciences, 358(1429), p.59-83; discussion 83-5. Available at: http://rstb.royalsocietypublishing.org/content/358/1429/59.abstract.

Koonin, E.V. & Martin, W., 2005. On the origin of genomes and cells within inorganic compartments. Trends in genetics : TIG, 21(12), p.647-54. Available at: http://www.molevol.de/publications/135.pdf.

Koonin, E.V., 2007. An RNA-making reactor for the origin of life. Proceedings of the National Academy of Sciences of the United States of America, 104(22), p.9105-6. Available at: http://www.pnas.org/content/104/22/9105.extract.


etc.

Locking up a bunch of molecules in a bin and hoping they'll react will most likely not work. You need a dynamic environment full of useable energy and replenishing resources. Then you need time. A lot of time.
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Re: Life origins problem

Postby mfb » Mon Jan 30, 2012 10:38 am UTC

Back-of-the-envelope calculation for panspermia: We have 51 stars within 5 pc[1], which is equivalent to 80ly^3 per star. Something which left a planetary system might travel with ~20km/s. In order to be captured by a planetary system, it has to hit a planet, be captured by a lot of gas or come very close to planets. I'll just use the approximate size of the sun itself ((3 light seconds)^2) as cross section for a capture. I think this is a good overestimate for every planetary system, and an underestimation for gas disks. But these gas disks are quite short-living.
Putting these numbers together, an object has a mean free length of 8*10^15 ly, which is equivalent to an average lifetime of 10^20 years.
Within 1 billion years, I would expect that a fraction of about ~10^-11 of these objects hits something.

It is not so trivial to extract life from earth - it has to be quite a large collision to get parts of earth into space. Life has to survive the collision. Afterwards, the parts need some instable path which leads them out of the solar system. Life has to survive at least some million years in space and the final impact. And it has to land on another planet which can support life.

Feel free to change some orders of magnitude in these numbers, if you like. The main message is: There is no interstellar internet which constantly exchanges matter between planets.


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