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Old August 27 2013, 01:31 PM   #31
Relayer1
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Re: Whee are the aliens?

Warped9 wrote: View Post
Life might indeed be common in terms of simple or non complex life like on the microbial level or such. And there might be worlds teaming with complex life on the animal level like Earth of the past before the rise of human intelligence and human civilization. The rarity mightn't be in life or even a measure of intelligence, but in intelligence giving rise to advanced technological civilizations.
Possible, but you also have to take into account 'deep time'. Even if there have been many intelligent civilisations within detectable range, over the (pretty unimaginable) length of time they could have developed in, the chances of them evolving at the same time as us (or at least at the right time for us to have picked up their traces) are very very small.
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Old August 27 2013, 02:10 PM   #32
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Re: Whee are the aliens?

Lindley wrote: View Post
Edit_XYZ wrote: View Post
1. Abiogenesis.
What is the road from a bunch of chemicals to the "simplest" molecules that can replicate themselves halfway reliably?
Let's - VERY optimistically - assume that a specific chain of 100 chemical reactions are enough to create this "simplest" molecule.

Now - Darwinian selection has no part in creating this molecule; for Darwinian selection, you need self-replication, which you do not yet have.
Which leaves probability in charge. For a very rough approximation, calculate factorial 100. It gives a number so close to 0 as the chance of this "simplest" molecule emerging, that the chances are life on Earth is alone in the observable universe (and a huge chunk of the unobservable one).

Conclusion - abiogenesis is rare. VERY rare. Even if my factorial 100 approximation is exceedingly rough and even if there are hundreds of billions of Earth-like worlds in our galaxy, the chances are only ours ever gave birth to life.
Two objections to this argument. First, chemical reactions are highly sensitive to conditions. If the right conditions exist, they can easily drive a particular product from 1% to 99%. We aren't entirely sure what the right conditions are for ambiogenesis, of course.
Indeed - the conditions needed for the first of 100 chemical reactions must exist; followed by the conditions needed for the second of 100 chemical reactions; etc; etc. Throughout the process, conditions that destroy the fledgling molecule-to-become-self-replicating must not come to pass.

The chances of 100 such conditions existing in the right succession are - very roughly - approximated as factorial 100.

One more thing - abiogenesis is not a case of 'all roads lead to Rome'; we have tried to create life in the laboratory mimicking primordial Earth conditions or not, etc, etc - and failed.
We can be quite sure that there are only a limited number of '100 chemical reactions'* chains that lead to life. Only one such chain is confirmed to exist - the one that lead to life on Earth, to us.

*Realistically, a LOT more than 100 chemical reactions are necessary in order to create a self-replicating molecule. Such a molecule is so complex, we have trouble even theoretically designing it.
I was just being highly optimistic in my 100 steps estimate.

Second, even an exceptionally unlikely event becomes probable when there are enough chances. Winning the lottery is exceptionally unlikely, yet someone seems to win every few weeks because there are so many players. Similarly, there could be trillions of ambiogenesis precursor molecules out there. Granted, 100! is much larger than one trillion, but the odds are at least improved somewhat.
100! is 9.3326215444×10ˆ157.
That means there is a chance in 9.3326215444×10ˆ157 for life to come into being.
Lindley, the number of atoms in the observable universe is generously estimated at 10ˆ80. And only a small fraction of these are amenable to giving birth to life.

This means that, in order to win the 'lottery' of life, you need more than the atoms in the observable universe. A LOT more.

As I already said, 100! gives a number so close to 0 as the chance for the "simplest" self-replicating molecule to emerge, that the chances are life on Earth is alone in the observable universe (and a huge chunk of the unobservable one).
Even considering the abyss of time (6-7 billions of years), of space, considering Earth-like planets as a dime a dozen and taking my 100! only as a very rough/high estimate.
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Old August 27 2013, 02:34 PM   #33
Edit_XYZ
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Re: Whee are the aliens?

Warped9 wrote: View Post
Every generation is so sure of its grasp of science only for later generations to learn how to shine a light into previously dark rooms.

The universe is so vast and stranger than we can imagine that's it's folly to assume we already have definitive answers. I suspect we don't even know we're overlooking something, perhaps something crucial, in trying to answer this question.
I recommend reading:
http://chem.tufts.edu/answersinscien...ityofwrong.htm

Also, we're talking about biochemistry in conditions we can recreate, not about massive black holes or other such extreme phenomena.
Our theoretical/empirical knowledge in biochemistry is pretty good.
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Old August 27 2013, 03:05 PM   #34
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Re: Whee are the aliens?

Edit_XYZ wrote: View Post
This means that, in order to win the 'lottery' of life, you need more than the atoms in the observable universe. A LOT more.
At any one time, yes. When you have millions of years to work with that acts as a multiplier on "lottery tickets" as well---a fairly large one.

Our ability to design a self-replicating molecule is irrelevant; there are lots of things nature does better than our designs.

I'm also going to question your conclusion that evolutionary forces are irrelevant. Certainly, it wouldn't work in the traditional sense. However, it's possible that certain molecules had advantages (or disadvantages!) of some sort given a particular environment, and this could prune the decision tree considerably.

I'm not saying it's not unlikely, mind.
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Old August 27 2013, 03:07 PM   #35
CorporalCaptain
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Re: Whee are the aliens?

Edit_XYZ wrote: View Post
1. Abiogenesis.
What is the road from a bunch of chemicals to the "simplest" molecules that can replicate themselves halfway reliably?
Let's - VERY optimistically - assume that a specific chain of 100 chemical reactions are enough to create this "simplest" molecule.

Now - Darwinian selection has no part in creating this molecule; for Darwinian selection, you need self-replication, which you do not yet have.
Which leaves probability in charge. For a very rough approximation, calculate factorial 100. It gives a number so close to 0 [sic] as the chance of this "simplest" molecule emerging, that the chances are life on Earth is alone in the observable universe (and a huge chunk of the unobservable one).
Care to explain just what 100! is a "very rough approximation" of in this context and how you know it even is an approximation?
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Old August 27 2013, 03:26 PM   #36
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Re: Whee are the aliens?

Lindley wrote: View Post
Edit_XYZ wrote: View Post
This means that, in order to win the 'lottery' of life, you need more than the atoms in the observable universe. A LOT more.
At any one time, yes. When you have millions of years to work with that acts as a multiplier on "lottery tickets" as well---a fairly large one.

Our ability to design a self-replicating molecule is irrelevant; there are lots of things nature does better than our designs.

I'm also going to question your conclusion that evolutionary forces are irrelevant. Certainly, it wouldn't work in the traditional sense. However, it's possible that certain molecules had advantages (or disadvantages!) of some sort given a particular environment, and this could prune the decision tree considerably.

I'm not saying it's not unlikely, mind.
Lindley, if a molecule can't self-reproduce, it cannot 'spread' its 'advantages'. Other molecules disappearing from the environment also doesn't help it, if it can't self-reproduce. AKA NO Darwinian evolution.
Feel free to post a scenario for Darwinian selection where the actors are not self-replicating - if you have one.


Our inability to design a self-replicating molecule is highly relevant, showing us we're talking about a highly complex construct - that is not easily achievable by putting some environments one after the other. You need some very, very specific environments - so subtle, we didn't figure out which despite a lot of searching (not blindly, but guided by science).


And we're talking about, VERY generously, 100 orders of magnitude between the chances of life existing and the number of atoms in the observable universe that can give birth to life (between ~10ˆ157 and a small fraction of 10ˆ80).
Good luck winning this lottery.

As said, Lindley, you can have all the 6-7 billion years of abyss of time. It barely makes a dent in the improbability.
And you can have the universal abyss of space, considering Earth-like planets as a dime a dozen and taking my 100! only as a very rough/high estimate. The probability of life appearing twice in the observable universe remains practically 0.

CorporalCaptain wrote: View Post
Edit_XYZ wrote: View Post
1. Abiogenesis.
What is the road from a bunch of chemicals to the "simplest" molecules that can replicate themselves halfway reliably?
Let's - VERY optimistically - assume that a specific chain of 100 chemical reactions are enough to create this "simplest" molecule.

Now - Darwinian selection has no part in creating this molecule; for Darwinian selection, you need self-replication, which you do not yet have.
Which leaves probability in charge. For a very rough approximation, calculate factorial 100. It gives a number so close to 0 [sic] as the chance of this "simplest" molecule emerging, that the chances are life on Earth is alone in the observable universe (and a huge chunk of the unobservable one).
Care to explain just what 100! is a "very rough approximation" of in this context and how you know it even is an approximation?
I take it as a very rough approximation because it leaves out many factors:
-In the primordial earth, there were many environments, not just 100;
-As such, the problem of abiogenesis is more correctly stated as: 'these 100 steps should follow one after another without one or more destructive environments appearing between them, destroying the future self-replicating molecule';
-The number of steps necessary to create a molecule that can replicate half-way reliably is probably larger than 100;

In essence, 100! is a simplification, only there to give a rough idea about the improbability of self-replicating molecules emerging.
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Old August 27 2013, 03:56 PM   #37
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Re: Whee are the aliens?

Edit_XYZ wrote: View Post
CorporalCaptain wrote: View Post
Edit_XYZ wrote: View Post
1. Abiogenesis.
What is the road from a bunch of chemicals to the "simplest" molecules that can replicate themselves halfway reliably?
Let's - VERY optimistically - assume that a specific chain of 100 chemical reactions are enough to create this "simplest" molecule.

Now - Darwinian selection has no part in creating this molecule; for Darwinian selection, you need self-replication, which you do not yet have.
Which leaves probability in charge. For a very rough approximation, calculate factorial 100. It gives a number so close to 0 [sic] as the chance of this "simplest" molecule emerging, that the chances are life on Earth is alone in the observable universe (and a huge chunk of the unobservable one).
Care to explain just what 100! is a "very rough approximation" of in this context and how you know it even is an approximation?
I take it as a very rough approximation because it leaves out many factors:
-In the primordial earth, there were many environments, not just 100;
-As such, the problem of abiogenesis is more correctly stated as: 'these 100 steps should follow one after another without one or more destructive environments appearing between them, destroying the future self-replicating molecule';
-The number of steps necessary to create a molecule replicating half-way reliably is probably larger than 100;
Etc.

In essence, 100! is a simplification, only there to give a rough idea about the improbability of self-replicating molecules emerging.
So, in other words, it's just something you pulled out of your ass.

The issue isn't so much the 100 part, but the factorial. You seem to have settled on that, because you like the fact that 100! is astronomically huge.

Here are just two problems with your assumption that factorial is the correct function.

First, the steps that need to be performed in order are not all independent of each other. Certain later steps can occur only if their reactants are available. Therefore, not all of the combinations counted by your function are equally likely to occur, since some of them are in fact impossible, namely the ones describing sequences in which steps occur before their reactants are available. For example, if C depends on both A and B, then CAB, CBA, ACB, and BCA are four of the 6=3! sequences counted by your function, but they couldn't possibly occur, since C simply can't happen without the products of both A and B. This is one reason why your function grossly underestimates the odds of the final product occurring randomly. The impossible combinations, being ruled out, can't muck things up.

The overwhelming majority of the combinations you've counted are in fact impossible for this first reason alone. The number of impossible combinations is at least 99!. Just consider the combinations where the final step occurs first, and then count all ways of reordering the remaining 99 steps. Those are all impossible combinations, unless the molecule in question only needs one step to be produced. Similarly, the ones where the final step occurs second are also invalid. Assuming 100 steps are required to produce the molecule in question, then since the final step has to occur last, only at most 99! of the counted combinations are valid, which is at most 99!/100!=1% of the total counted. Further dependencies place further restrictions on the ordering.

A second problem is that steps that are independent of each other can be interchanged. For example, if A and B are independent of each other, but C depends on both A and B, then ABC and BAC are both valid sequences. Your function only admits one of them.

The factorial function counts the number of ways of reordering sequences. That's the wrong function to use in this case. There is no valid argument that it is even a rough approximation of the correct value.
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Old August 27 2013, 04:01 PM   #38
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Re: Whee are the aliens?

Edit_XYZ wrote: View Post
Lindley, if a molecule can't self-reproduce, it cannot 'spread' its 'advantages'. Other molecules disappearing from the environment also doesn't help it, if it can't self-reproduce. AKA NO Darwinian evolution.
Feel free to post a scenario for Darwinian selection where the actors are not self-replicating - if you have one.
I'm not referring to Darwinian selection per se (that requires reproduction). More that if certain environments favor a particular molecular intermediate heavily, then that form may dominate in that environment; and the probability of any other outcome *prior* to that point in the chain becomes of little importance. Hence, the decision tree could be heavily pruned in places.

This works on the theory that many reactions are reversible, so even if a molecule undergoes the "wrong" reaction at some point it may eventually end up in the "right" state due to conditions. Also, there can be more than one way to synthesize a given molecule, so that needs to be considered as well.

Our inability to design a self-replicating molecule is highly relevant, showing us we're talking about a highly complex construct - that is not easily achievable by putting some environments one after the other. You need some very, very specific environments - so subtle, we didn't figure out which despite a lot of searching (not blindly, but guided by science).
You're the one arguing the number of possibilities is immense. I'm not convinced "science" gives us enough of an advantage to claim we could find in a few years when nature took billions of years to figure out. Heuristics only improve state space search if you pick the right one.

I'm not sure how it affects the math, but I'd also point out that even though the number of possible molecules increases incredibly fast, the number of possible *reactions* at each step does not. There are a (comparatively) restricted number of ways functional groups can interact. This *might* indicate your assumption of 100! possible outcomes is overly pessimistic.
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Old August 27 2013, 04:18 PM   #39
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Re: Whee are the aliens?

CorporalCaptain wrote: View Post
Edit_XYZ wrote: View Post
CorporalCaptain wrote: View Post

Care to explain just what 100! is a "very rough approximation" of in this context and how you know it even is an approximation?
I take it as a very rough approximation because it leaves out many factors:
-In the primordial earth, there were many environments, not just 100;
-As such, the problem of abiogenesis is more correctly stated as: 'these 100 steps should follow one after another without one or more destructive environments appearing between them, destroying the future self-replicating molecule';
-The number of steps necessary to create a molecule replicating half-way reliably is probably larger than 100;
Etc.

In essence, 100! is a simplification, only there to give a rough idea about the improbability of self-replicating molecules emerging.
So, in other words, it's just something you pulled out of your ass
Annoyed much, CorporalCaptain?
BTW, a simplification is far from 'pulling out of one's ass'.

The issue isn't so much the 100 part, but the factorial. You seem to have settled on that, because you like the fact that 100! is astronomically huge.
Really?
You don't say?

Here are just two problems with your assumption that factorial is the correct function.

First, the steps that need to be performed in order are not all independent of each other. Certain later steps can occur only if their reactants are available. Therefore, not all of the combinations counted by your function are equally likely to occur, since some of them are in fact impossible, namely the ones describing sequences in which steps occur before their reactants are available. For example, if C depends on both A and B, then CAB, CBA, ACB, and BCA are four of the 6=3! sequences counted by your function, but they couldn't possibly occur, since C simply can't happen without the products of both A and B. This is one reason why your function grossly underestimates the odds of the final product occurring randomly. The impossible combinations, being ruled out, can't muck things up.
You are confusing the environments and the chemical steps to which they give birth.
I posited 100 environments that must occur in order, in order to create in the 'warm pond' or wherever the chemical steps for the appearance of life.
These environments are independent of each other, one can occur out of order* - in which case, of course, the fledgling molecule not being available, bye bye future self-replicating molecule.

*Unless you want to post a magical environment that creates the successive ones/a large number of the successive ones.

The overwhelming majority of the combinations you've counted are in fact impossible for this first reason alone. In fact, the number of impossible combinations is at least 99!. Just consider the combinations where the final step occurs first, and then count all ways of reordering the remaining 99 steps. Those are all impossible combinations, unless the molecule in question only needs one step to be produced.
Cute. See above.

A second problem is that steps that are independent of each other can be interchanged. For example, if A and B aSo - here you're positing a magical initial condition that can create re independent of each other, but C depends on both A and B, then ABSo - here you're positing a magical initial condition that can create C and BAC are both valid sequences. Your function only admits one of them.

The factorial function counts the number of ways of reordering sequences. That's the wrong function to use in this case. There is no valid argument that it is even a rough approximation of the correct value.
The chemical steps necessary you achieve a self-replicating molecule cannot be interchanged (especially when talking about as few as 100*) - even if the 100 environments can appear independently of each other (although, if they have no fledgling molecule, they go nowhere).

If you interchange these chemical steps you will end up with a boring chemical soup - nothing self-replicating.

*When you want to talk about a more realistic ~1000 chemical steps - sure, you can probably interchange a few.
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Old August 27 2013, 04:41 PM   #40
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Re: Whee are the aliens?

Edit_XYZ wrote: View Post
Annoyed much, CorporalCaptain?
Not at all. You're just posting nonsense.
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Old August 27 2013, 04:43 PM   #41
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Re: Whee are the aliens?

Lindley wrote: View Post
Edit_XYZ wrote: View Post
Lindley, if a molecule can't self-reproduce, it cannot 'spread' its 'advantages'. Other molecules disappearing from the environment also doesn't help it, if it can't self-reproduce. AKA NO Darwinian evolution.
Feel free to post a scenario for Darwinian selection where the actors are not self-replicating - if you have one.
I'm not referring to Darwinian selection per se (that requires reproduction). More that if certain environments favor a particular molecular intermediate heavily, then that form may dominate in that environment; and the probability of any other outcome *prior* to that point in the chain becomes of little importance. Hence, the decision tree could be heavily pruned in places.

This works on the theory that many reactions are reversible, so even if a molecule undergoes the "wrong" reaction at some point it may eventually end up in the "right" state due to conditions. Also, there can be more than one way to synthesize a given molecule, so that needs to be considered as well.
The difference between Darwinian selection and life appearing by chance is probability:
It is very probable that a molecule that can self-replicate better will replicate more - Darwinian selection.
It is not probable that just the right environment will come to help along a not-yet-self-replicating molecule.

If the outcomes prior to one point in the chain are not relevant, then the chain effectively starts there; if you need certain non-common compounds in the 'warm pond', though, it doesn't start there.

And yes, there could be more than one road to life (for example, you mentioned a variant of 101 steps where the molecule goes wrong and then an environment comes that redresses it).
But the number of roads to life is limited - that is pretty certain after the failures of artificial abiogenesis.

Our inability to design a self-replicating molecule is highly relevant, showing us we're talking about a highly complex construct - that is not easily achievable by putting some environments one after the other. You need some very, very specific environments - so subtle, we didn't figure out which despite a lot of searching (not blindly, but guided by science).
You're the one arguing the number of possibilities is immense. I'm not convinced "science" gives us enough of an advantage to claim we could find in a few years when nature took billions of years to figure out. Heuristics only improve state space search if you pick the right one.
Yes, but of this immense number of possibilities, the overwhelming majority are gibbeish. Nature didn't eliminate those; we did.
Nature advanced blindly; we don't.

I'm not sure how it affects the math, but I'd also point out that even though the number of possible molecules increases incredibly fast, the number of possible *reactions* at each step does not. There are a (comparatively) restricted number of ways functional groups can interact. This *might* indicate your assumption of 100! possible outcomes is overly pessimistic.
100! gives such a small chance not because of the number of possible reactions at each point, but because the 100 environments must be independent from each other (environment 1 must not create environment 2, etc) and they must come in a specific order and no other.

I took these environments as independent of each other.
That's why I took the number of environments as small as 100; if environment A creates B creates C, for example, I took them all as a single environment 1 in the 100 chain (due to the high probability of B, C).

Let's say that there are 1.000.000 roads to life (and shame on our biologists for not discovering even one) - this increases the chance of life emerging, but not enough.
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Old August 27 2013, 04:47 PM   #42
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Re: Whee are the aliens?

CorporalCaptain wrote: View Post
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Annoyed much, CorporalCaptain?
Not at all. You're just posting nonsense.
And now, unsupported dictums on your part.
You may want to come up with something less confused than your previous post to support it.
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Old August 27 2013, 05:25 PM   #43
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Re: Whee are the aliens?

Edit_XYZ wrote: View Post


Our inability to design a self-replicating molecule is highly relevant, showing us we're talking about a highly complex construct - that is not easily achievable by putting some environments one after the other. You need some very, very specific environments - so subtle, we didn't figure out which despite a lot of searching (not blindly, but guided by science).
So in a lab we haven't been able to re-create a self-replicating molecule. Could that mean our hypothesis is in error. Science does not stand still.
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Old August 27 2013, 10:16 PM   #44
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Re: Whee are the aliens?

Edit_XYZ wrote: View Post
I posited 100 environments that must occur in order, in order to create in the 'warm pond' or wherever the chemical steps for the appearance of life.
Actually, no, that's not what you posited in the first place. What you posited was:

Edit_XYZ wrote: View Post
Let's - VERY optimistically - assume that a specific chain of 100 chemical reactions are enough to create this "simplest" molecule.
For the purposes of illustration, by way of a simple example, you said sequence of "reactions", not sequence of "environments".

It was your evident assertion, that the probability of such a sequence of reactions occurring is approximately 1/100!, that I disproved. The factorial function is not the way to enumerate all of the possibilities in the case you first described, as I showed.

But, OK, so now you want to shift the goalposts. You're not trying to find the probability of a sequence of reactions occurring. Rather, you're trying to find the probability that "environments" all occur in a sequence that is itself compatible with supporting some sequence of reactions. You've postulated some properties of these "environments". Crucially, you said, quite correctly:

Edit_XYZ wrote: View Post
'these 100 steps should follow one after another without one or more destructive environments appearing between them, destroying the future self-replicating molecule'
Quite correct, they should, in order for the final product in question to be produced.

But for 1/100! to be the correct approximate probability of the environments occurring in the correct sequence, it is necessary—among other things—to assume that at each step all but one of the environments should be destructive to the molecules produced so far, with the environment left over leading to the next step.
But how do you know this must be the case?
Frankly, you don't. It's just an assumption, and it's a very specific one. Evidently, its only reason for existing is to ensure a ridiculously astronomical probability of the final product in question occurring.

Further questions suggest themselves.
Why can't a single environment be conducive to multiple steps in the process?
Why can't the products of some or all of the steps exist in multiple environments?
There are plenty of reasonable assumptions that drastically improve the odds of random reactions producing key chemicals.

Even with all of these sorts of questions aside, there still remains the even more basic question, posed already and addressed by you with only another handwave:
Why is only one order of reactions acceptable?
Further questions suggest themselves here as well.
Why is it that only one sequence of reactions produces a viable final product?
Couldn't there be a variety of final products from different reaction sequences, all different, yet all viable?
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Old August 29 2013, 09:02 PM   #45
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Re: Whee are the aliens?

Warped9 wrote: View Post
Thoughts anyone on where is ET?
E.T. stayed home.

Because interstellar travel is either impossible or infeasible on any timescale that would be justifiable in the resource allocation systems of any sentient life form, and interplanetary travel, while far more doable, isn't likely to be noticed across interstellar distances.

Simply put: we could easily be surrounded by intelligent life forms both far ahead and far behind us technologically, but we would never know it unless one of them developed the means to physically visit our system. Apart from the fact that they have no specific reason to visit us (just one system among thousands in the neighborhood) they also probably lack either the motive or the means to do so.
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