Life on Earth: a Possibility Too Small, or an Undiscovered Law?

[lwymarie]

Accorinding to a lot of data and information, it seems that the possibility of producing life is too small. Does it mean that the life on Earth is not formed 'accidentially'? I do not mean that there must be a God (as it is not a religious forum). However, does the too small possiblity means that there is acutally an undiscovered law governing the universe? What do you think?

 

[quasi426]

Some believe the origins of biomolecules came from debris from outer space.

 

[Emieno]

Accorinding to a lot of data and information, it seems that the possibility of producing life is too small. Does it mean that the life on Earth is not formed 'accidentially'? I do not mean that there must be a God (as it is not a religious forum). However, does the too small possiblity means that there is acutally an undiscovered law governing the universe? What do you think?

Life came from cells,
Cell is composed of chemical elements
Chemical elements are divided into organic and inorganic ones
Although there wouldnot have been many organic elements on early earth, from small amount of them small parts of cell were created, then under some conditions of primitive environment, they needed to divide to survive and grow.

 

[wolram]

For life to be universal it must have a plan, at least to get to the single cell
stage, AFAIK no one can make life from a chemistry set, so it seems to me
that life would be a very rare occurence.

 

[hexhunter]

it doesn't really help prove god, or 'intentional' life, it does however help disprove the liklyhood of living creatures on similar worlds, what sort of planet would be better for life?

 

[El Hombre Invisible]

Some believe the origins of biomolecules came from debris from outer space.

That's true, and I haven't heard anything on this for ages. Comets contain some organic molecules... something cyanide and something else I can't remember, but it is thought that comets may be kind of 'starter packs' for life. Sounds groovy.

 

[DaveC426913]

That's true, and I haven't heard anything on this for ages. Comets contain some organic molecules... something cyanide and something else I can't remember, but it is thought that comets may be kind of 'starter packs' for life. Sounds groovy.

I still say this doesn't answer the question. So what if the molecules came from comets? How does that explain *how* life came to be?

 

[iggybaseball]

There have been several theories submitted as to how life on Earth began. For example, Stanley Miller in 1953 developed a simple experiment to prove how life may come into existence. Assuming that this process had happened after reduced molecules existed in Earth's atmosphere, Miller set up a flask of water that connected to another flask containing Hydrogen, Ammonia, and Methane. He placed small electrodes in the flask containing the gases to simulate lightning.

When he heated the flask with water, water vapor would travel to the smaller flask with the gas and electrodes. Next the gas would be condensed back into liquid and sent back to the original flask of water and the system would circulate. He later found that his water flask found copious amounts of formaldehyde and hydrogen cyanide, precursors to life.

Now this account is far from extensive and there is a lot to the story. For example, some people argued that the gasses he assumed to exist in early Earth are not completely accurate. However there have been more demonstrations to prove their theories.

There is a plethora of information on the subject and I think a reason why some find it difficult to simulate is because the atmosphere of our Earth and what not is much different from when it first birthed life. As for other hidden laws we may not know of , I agree in general that this is true, because I believe that we still have much to learn in science.

 

[El Hombre Invisible]

I still say this doesn't answer the question. So what if the molecules came from comets? How does that explain *how* life came to be?

I wasn't trying to. I was just commenting that I had heard this theory. Explaining how to get from organic molecules to human beings is a job I'm not qualified to do. Someone else might want to, but I imagine that would be a veeeeeery long post.

 

[El Hombre Invisible]

He later found that his water flask found copious amounts of formaldehyde and hydrogen cyanide, precursors to life.

THAT'S THE FELLAS! Yeah, they were found to be in comets too.

 

[Moonbear]

The problem of trying to use probability to justify that life started out as something other than a random process is that probability uses information about past occurrences to predict future occurrences of something. So, if we only know life started once (or that's our best guess anyway), that's not much of a data set to use for predicting trends or probabilities. Since we still don't know exactly how that first life came to exist, how can we really say much about the odds of it happening again? The reality is that life DID come into existence; any probability estimates are only for the chance that it can independently happen again in the future. Think of it like playing the lottery. Your odds of winning in the future could be something like 1 in 16 million (made up number). So, you could argue that you would need to buy 16 million tickets before you would win. But, that's not how it really happens. Every so often you hear of the case where some lucky person who never buys tickets walks into a convenience store and buys one ticket with the dollar in change he got from buying a jug of milk and hits the jackpot. Does that mean there was some intelligent plan or non-randomness involved? Absolutely not. The nature of true randomness is that if your odds are 1 in 16 million, you could hit it on the first try or on the 16-millionth try, or any try in between.

The other issue I have is that there is non-randomness in the formation of chemical bonds, yet when people predict the probability of life forming, they seem to assume it had to happen through all of the necessary elements simultaneously colliding and forming life in one instant. For example, we know that all amino acids have both a common structure and R-groups that make them distinct from one another. Chemists would have a really hard time conducting any experiments or synthesizing any new compounds if chemical reactions were completely random and nothing could be predicted about the behavior of elements or compounds when they are mixed together. This does not require that there is intelligence involved in those reactions happening just because they are non-random. A molecule won't just react with any other molecule it happens to bump into, there have to be certain conditions met, but once those conditions are met, there's a very high probability that two molecules will react.

So, just because there is a low probability of something happening a second time, and because some aspects of it are not explained by total randomness, this does not mean the only explanation is an intelligent force. It's not an either/or situation.

 

[wolram]

This is from wikipidia
On September 28, 1969, a meteorite that fell over Murchison, Victoria, Australia was found to contain over 90 different amino acids, nineteen of which are found in Earth life. Comets and other icy outer-solar-system bodies are thought to contain large amounts of complex carbon compounds (such as tholins) formed by these processes, in some cases so much so that the surfaces of these bodies are turned dark red or as black as asphalt. The early Earth was bombarded heavily by comets,
So may be life or its basic building blocks were formed in space, but step 2
finding a friendly host would be the next difficulty, step 3 evolving cellular
structure, i think would be a matter of time and a lot of it.

 

[vanesch]

The problem of trying to use probability to justify that life started out as something other than a random process is that probability uses information about past occurrences to predict future occurrences of something.

Just as a teaser: quantum theory could play a role, in that if quantum theory is correct "all the way up", then this leads to a vastly more complicated universe (many worlds) than we observe. The development of life then derives from the quantum version of the anthropological principle. The only requirement for the anthropological principle to work is that the observed universe must be only a tiny spec of the ontological universe. Now, this can be the case classically (if the universe is infinite), or you can even obtain it for a smaller scale universe, if you allow for quantum superpositions.
Then it doesn't matter how terribly SMALL the a priori probabilities are for live to emerge: multiplied with the mindboggling size of the universe (in whatever version, which makes it much bigger than the *observable* universe), you can make them arbitrarily big. Which means that life happens *somewhere*. And if you're alive, then that somewhere must be here (that's the anthropological principle).

Now, I realize that the anthropological principle is not liked much because it sounds like a non-falsifiable statement. It isn't, really: but we don't know enough of the true a-priori probabilities for life to emerge. Nevertheless, it is not non-falsifiable, because it makes some definite predictions: for instance, if the anthropological principle is to be invoked, this means that there are no extraterrestrial life forms in the observable universe (otherwise that would make TWO of them in a small patch of the universe (namely only about 15 billion light years across), leading to necessarily FINITE probabilities that cannot be too small, and the invocation of the anthropological principle is not necessary). Too bad for Tom Cruise :-)

cheers,
Patrick.

 

[gerben]

Accorinding to a lot of data and information, it seems that the possibility of producing life is too small. Does it mean that the life on Earth is not formed 'accidentially'? I do not mean that there must be a God (as it is not a religious forum). However, does the too small possiblity means that there is acutally an undiscovered law governing the universe? What do you think?

A low probability for some event does not mean that it does not happen unless there is "something special".
If you throw a dice you will witness an event that had a probability of 1/6. Throw 10 dice and you will witness an event that had a probability of only 0.000000017

 

[wolram]

all this about probabilities reminded me of the fallen tree, one probability
was a pink elephant in a flying saucer knocked it down, the other that the
wind blew it down.

 

[pattylou]

Life schmife.

You don't need a cell to magically appear out of primordial soup. What you need, is a replicator. Period. Once you have a replicator, "random" doesn't really apply in the same way. The replicator catalyzes its own synthesis, and the whole ball of wax takes off.

Nucliec acid, baby, nucleic acid!

If you go to pubmed and search on 'prebiotic chemistry' you'll find lots of neat chemistry that has been done in the last 5 - 10 years. Miller and Urey were great, but there are all sorts of shiny new experiments - things like how certain clays in lakebeds catalyze the formation of oligonucleotides. Things like how hydrothermal vents might catalyze the formation of oligonucleotides. They've managed to simulate reasonable conditions to make a 50-mer, (50 nucleotides long) which can then catalyze its own synthesis.

And since oligonucleotides (like this 50-mer) can base pair with individual nucleotides - any sequence should automatically *catalyze* its own synthesis to a limited extent.

So, to make the first replicator, all you need is an oligonucleotide! You can worry about cell membranes and proteins, later.

Nucleic acid. I'm tellin' ya.

 

[saltydog]

They've managed to simulate reasonable conditions to make a 50-mer, (50 nucleotides long) which can then catalyze its own synthesis.

And since oligonucleotides (like this 50-mer) can base pair with individual nucleotides - any sequence should automatically *catalyze* its own synthesis to a limited extent.

Can you describe the chemical environment in which this synthesis occurred?
How about a reference? You can embed the link in the post by choosing the goggles on the tool bar, input a name for the link, then the actual link.

 

[pattylou]

Here's a review article from 2004:

Orig Life Evol Biosph. 2004 Dec;34(6):549-70. Related Articles, Links

Montmorillonite, oligonucleotides, RNA and origin of life.

Ertem G.

http://nai.nasa.gov/nai2005/abstracts/947%20-%20NAI2005ABS.doc.pdf

Also see:

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&dopt=Abstract&list_uids=12458736

This sort of research shows what sorts of steps *might* have happened on the early Earth. There are still too many unknowns to say with any certainty where life began (lake beds, hydrothermal vents, etc), and so on. I hope you find the references useful.

 

[pattylou]

Sorry - didn't see your first question.

This research doesn't deal with the formation of organic molecules; they assume organics are present (either due to Miller Urey type stuff, meteorites, or other events). So, if you are wondering about how reactive the atmosphere was, or something like that - I don't know if that applies.

Assuming organic reactants are present: In my understanding, the important feature in this line of experiments is montmorillonite. This is a clay found in some lakes. Whether a first replicator formed on montmorillonite or not is an open question. Anyway, in these experiments, researchers vary the concentrations of certain ions (looking at whether Na or K are more conducive to polymerization, for example); they vary the reactants, whether the nucleotides are mono, di, or tri phosphate, the reactions are aqueous, around pH8. Conditions are fiddled with, as the question of how the first replicator may have come about, is very interesting.

Here is one example of a set of conditions that has been used:

"Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. <snip> The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. "

 

[Danger]

"Oligomers of adenylic acid of up to the 11-mer in length are formed by the reaction of the phosphorimidazolide of adenosine (ImpA) in pH 8 aqueous solution at room temperature in the presence of Na(+)-montmorillonite. <snip> The exchangeable cation associated with the montmorillonite effects the observed catalysis with Li+, Na+, NH4+, and Ca2+ being the more effective while Mg2+ and Al3+ are almost ineffective catalysts. "

Oh great... I had to be on my 14th beer before I ran across this. Now I'll have to come back to it tomorrow to read it properly. :grumpy: The one thing that I notice about Wooly's comments is that he seems to echo a lot of non-scientists/creationists/SF critics who marvel at how perfect the Earth is for us to live on, and thus must have been designed for us. They all seem to miss the point that it's perfect for us because this is where we evolved. If we had started on Venus instead, we'd probably have a sulphur/silicon metabolism and think that Earth was a frigid near-vacuum environment. Those critters that live on undersea volcanic vents would probably hold the same opinion about surface conditions if they were sentient. Although it's one of the most practical, workable situations, no rule says that life has to be Earth-like, or even carbon based. Even something that resembles us superficially but uses levorotating sugars instead of dextrorotating would be a completely different life form.

 

[saltydog]

Here's a review article from 2004:

Orig Life Evol Biosph. 2004 Dec;34(6):549-70. Related Articles, Links

Montmorillonite, oligonucleotides, RNA and origin of life.

Ertem G.

http://nai.nasa.gov/nai2005/abstracts/947%20-%20NAI2005ABS.doc.pdf

Also see:

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&dopt=Abstract&list_uids=12458736

This sort of research shows what sorts of steps *might* have happened on the early Earth. There are still too many unknowns to say with any certainty where life began (lake beds, hydrothermal vents, etc), and so on. I hope you find the references useful.

PattyLou, Moonbear, somebody, can you please explain to me how to get the ENTIRE article out of Pub-Med. That's only an abstract up there, both of them. I'd like some details.

 

[El Hombre Invisible]

all this about probabilities reminded me of the fallen tree, one probability
was a pink elephant in a flying saucer knocked it down, the other that the
wind blew it down.

Trees are pretty strongly rooted, so it was probably the elephant. When did this happen?

 

[pattylou]

Hi Saltydog.

You can only get the abstract from Pubmed. After that, you can either go to your local library (if it is a good one and they carry the journal) or you can sometimes find full text online - After you have the title of the article you want, google it in quotes and if you are lucky you'll find it as a PDF.

But scan through abstracts of "related articles" on pubmed first. You'll get a feel for the field, who the researchers are (Ferris, Ertem come up a lot in this montmorillonite stuff), what the progress in the field has been, and so on.

And then there's the whole hydrothermal vent crowd. There are some other ideas floating around too.

 

[saltydog]

http://nai.nasa.gov/nai2005/abstracts/947%20-%20NAI2005ABS.doc.pdf

Also see:

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&dopt=Abstract&list_uids=12458736

Well, I aint' done yet. She brought it up. This is an excerpt:

"Na-montmorillonite catalyzes the self-condensation of 5’-phosphorimidazolide derivative of
adenosine, ImpA. Oligo(A)s formed in this reaction are 10 monomer units long and contain
67% 3’,5’-phosphodiester bonds. Under the same reaction conditions, ImpC, ImpU and
ImpG also undergo condensation producing oligomers containing up to 12-14 monomer units
for oligo(C)s to 6 monomer units for oligo(G)s. In oligo(C)s and oligo(U)s, 75-80% of the
monomers are linked by 2’,5’-phosphodiester bonds.

Hexamer and higher oligomers isolated from synthetic oligo(C)s, which contain both 3’,5’-
and 2’,5’-linkages, serve as catalysts for the non-enzymatic template directed synthesis of
oligo(G)s from activated monomer 2-MeImpG. Pentamer and higher oligomers containing
exclusively 2’,5’-linkages, which were isolated from the synthetic oligo(C)s, also serve as
templates and produce oligo(G)s with both 2’,5’- and 3’,5’-phosphodiester bonds."

You know what, I'd like to pick this apart. I mean, do they have to be so technical?

Is my decryption correct: Got a small sugar-phosphate strand with cytosine on it and under specific laboratory conditions, guanine nucleotides in the media line up on it.

That's very interesting really. And no enzymes in the media neither?

Edit: I mean how do the phosphate-diester bonds between nucleotides form (is it that or do I have to look it up?) . Are they saying the clay catalyzes the creation of these bonds? That seems to be the key to me.

So are they saying if I start with some amount of cytosine strands, then let it cook for a while, I'll get a decent amount of sugar-phosphate guanine strands?

Suppose I start with a guanine strand? Can I make a cytosine strand? How about a little of both?

 

[pattylou]

I think you're on the right track in your thinking.

Certain non-enzymatic things can catalyze nucleotide dimerization - UV light, for example.

The finding some years ago that clays could do the same thing - was exciting. It allows for a wider range of possible scenarios on early Earth that might have started the ball of life rolling. Ever since learning that this montmorillonite clay could catalyze nucleotide dimerization, people have been fiddling with it to see how far it can be taken. A fifty-mer is pretty amazing! And yes, the base pairing is simple hydrogen bonding - so it makes sense that an oligo will give a leg up to the next strand that forms. (It will help orient the nucleotides, and act as a template.

Chemistry happens, you know? It's pretty cool.

So are they saying if I start with some amount of cytosine strands, then let it cook for a while, I'll get a decent amount of sugar-phosphate guanine strands?

Suppose I start with a guanine strand? Can I make a cytosine strand? How about a little of both?

Yep. In my understanding. And since the planet had 500million years or so to work on it, I really don't buy the initial premise in the thread that life was too improbable to have occurred "by chance."

 

[saltydog]

Thanks. I'll spend some time with it.

I really don't buy the initial premise in the thread that life was too improbable to have occurred "by chance."

"What marvelous adaptive tendencies of diversity in chance-fluctuating environments. Such is a beautiful expression of Quantum Mechanical favor"

 

[vanesch]

And since the planet had 500million years or so to work on it, I really don't buy the initial premise in the thread that life was too improbable to have occurred "by chance."

The difficulty I have with the statement that life "is quite probable" is: where are the little green men then ?

Let us call L the probability per unit hypercube of spacetime (in units of (10 billion light years)^3 x 10 billion years) to devellop life, including all factors (types of stars, planets, density of stars in the universe, presence of clay...). I take it that if life devellops, then also intelligent life devellops with not too small a probability.
Given the unit I chose, L is also about the probability to find a planet with life on it in the visible universe.
Now, L can take a priori all values: it can be 10^1220 or it can be 10^(-55230). But if we know enough cosmology, planetology, exo geology, chemistry and biology, we can calculate L from a few physical constants (the fundamental constants like the speed of light, Planck's constant and so on and a few cosmological parameters such as the matter density in the universe, its density fluctuations etc...), so L is just a physical quantity that is in principle calculable (although it is extremely difficult to do so in practice). The important point is just that L is a quantity that is determined by the laws of nature and a few cosmological parameters (that give us the expected number of stars, their kinds, the distribution of planets, their geology etc...).

If L is a big value, then the universe is FULL of life, so the question is: WHERE ARE THE LITTLE GREEN MEN ?
If L is a very small value, then the odds of life having develloped in the visible universe is rather small, at odds with what we observe, namely that we are here. It is in this range that the anthropological principle has a meaning: amongst zillions of "possible" universes, we picked (of course) one in which we exist."

However, the arguments here seem to imply that L is of the order of unity: the number of times for life to devellop in the visible universe over about 10 billion years independently is a small positive integer: we are not invaded by little green men all the time, and nevertheless we are here. So of all possible values of L, it turns out that L can only take on values in a rather narrow range. So it seems that our universe has by coincidence those right laws of nature (which determine the constant L) for it to fall in this narrow range. Such a coincidence is usually called: parameter fine tuning, and considered a bad thing (there's a remarquable coincidence that one doesn't understand when such a thing happens).

 

[pattylou]

I believe we are not invaded by little green men, due to the vastness of space.

I also believe there is a problem with the notion that life will certainly give rise to intelligent life. I have not seen good speculation on this one way or the other, but consider that for life to be intelligent, it must first be multicellular. For life to be multicellular, it must be able to perform some serious catabolism in order to harvest necessary energy for organising itself ---- in practical terms, I know of no strictly anaerobic multicellular organisms, for example. Aerobic respiration allows more energy harvest per glucose, and requires an oxygen atmosphere.

If (and this is a big if) an oxygen atmosphere is required for the emergence of multicellular life, then certain conditions muct be present on the planet - Oxygen is tough to make and retain (it's very reactive), and plants (and algae, etc) can do it because of being able to harvest energy from the sun.

To sum up the above, although it may be possible that the emergence of simple life is likely to lead to intelligent life, I don't know that this is a foregone conclusion.

Now let's also consider time scales. Life got going here on Earth pretty darn quick. Our technology, which allows radio waves, such as SETI has looked for, is quite recent indeed. There is no reason, as far as I am aware, to assume that aliens will have had sufficiently more time than us, to develop space travel. Any intelligent life "out there" may be roughly where we are, in terms of development. Consider that the nearest star, Vega?, is 25 years away. (I don't know the distance of the closest Sol type star. Anyone?) We earthlings started emitting "intelligent" radio waves in the last 100 years, so think about this - there are precious few stars that would even be able to detect *our* intelligent life yet.

Finally, given the fabulous formaldehyde signatures from Mars reported by the ISA last year, as well as other indications, I believe it is likely we will find simple life on Mars.

-patty

 

[vanesch]

I believe we are not invaded by little green men, due to the vastness of space.

I also believe there is a problem with the notion that life will certainly give rise to intelligent life.

In fact, this doesn't change the argument. Call L then simply the probability density of intelligent life to devellop in the visible universe in about 10 billion years, with all the necessary conditions of getting up to radiobeaming up to the earth.
It is very odd that that probability is a number of order unity ; my same arguments go: if it is much bigger, we have little green men on the TV, and if it is much smaller, we shouldn't be here.

Of course, what has changed is that indeed, the universe might be full of non-intelligent life (intelligent in the sense of technologically able to send TV pictures across the universe), say with density K, which is much bigger than 1 (per hypercube 10billion (light) years ^4), and a tiny fraction (epsilon) of that only is part of the conditions cited above. But again, the funny thing is then, that the probability of going from this (very abundant) non-intelligent life to "radiobeaming life" is JUST FINETUNED so as to yield an L of order unity, because L = epsilon x K

That's the kind of coincidental finetuning which is suspect.