Quizzes & Puzzles15 mins ago
Self-Replicating Molecules.
How did certain chemicals combine to produce the first self-replicating molecules?
Answers
We don't know. Writings on the subject are still full of the words 'possibly' and 'perhaps'.
17:56 Wed 13th Nov 2013
heathfield; Are you saying "We don't know"as in 'How?' or as in 'if ?'.
OG; //Plenty of time and plenty of locations for stuff to come together just so once.// Are you suggesting that given a finite amount of time (4.54 Billion years) is enough for "stuff to come together" ? Is this not the 'stuff' of Dr Frankenstein?
jomifl; You claim to speak for an aspect of science believing in this theory, so isn't it up to YOU to describe which chemicals?
OG; //Plenty of time and plenty of locations for stuff to come together just so once.// Are you suggesting that given a finite amount of time (4.54 Billion years) is enough for "stuff to come together" ? Is this not the 'stuff' of Dr Frankenstein?
jomifl; You claim to speak for an aspect of science believing in this theory, so isn't it up to YOU to describe which chemicals?
I'm presuming here we're talking about the origins of life.
The fact is we'll never know for sure it was so long ago the evidence will have been lost - even if we can do it in an experiment or see it on another planet we won't be able to say for sure that's how it happened on Earth.
What we do know is that DNA was a later development, RNA came first and some think Sulphur compounds called Thioesters were involved before that.
http://
What we also know is that life started on Earth very very early - almost as soon as the heavy bombardment period had stopped which tends to imply it's not a difficult process.
Complex life with mitochondria took billions of years to come about
Whether complex life on Earth was a freak even is uncertain
The fact is we'll never know for sure it was so long ago the evidence will have been lost - even if we can do it in an experiment or see it on another planet we won't be able to say for sure that's how it happened on Earth.
What we do know is that DNA was a later development, RNA came first and some think Sulphur compounds called Thioesters were involved before that.
http://
What we also know is that life started on Earth very very early - almost as soon as the heavy bombardment period had stopped which tends to imply it's not a difficult process.
Complex life with mitochondria took billions of years to come about
Whether complex life on Earth was a freak even is uncertain
@Khandro,
One does not 'believe' the statements which scientists make: you either accept them or reject them.
Religion is the thing which involves/requires 'belief'.
Belief------^------science
opposite ends of the see-saw. :-)
Re: your opening post
//How did certain chemicals combine to produce the first self-replicating molecules? //
The Jehovah's Witnesses like posing questions like this, usually closely followed by the old argument-from-ignorance stance:-
"Ohhh, this science stuff is all too complicated for little me to understand so it must have been some super-being who made it all happen. Therefore God exists. QED".
Get me a bucket. Please.
One does not 'believe' the statements which scientists make: you either accept them or reject them.
Religion is the thing which involves/requires 'belief'.
Belief------^------science
opposite ends of the see-saw. :-)
Re: your opening post
//How did certain chemicals combine to produce the first self-replicating molecules? //
The Jehovah's Witnesses like posing questions like this, usually closely followed by the old argument-from-ignorance stance:-
"Ohhh, this science stuff is all too complicated for little me to understand so it must have been some super-being who made it all happen. Therefore God exists. QED".
Get me a bucket. Please.
The thing about "by chance" is that it's such a misleading statement. "by Chance" covers all sorts of different phenomena, in different ways and so on. The statement that life emerged by chance is likely* in the long run to mean that it was a thermodynamic process. Then, while life would have emerged by "chance", it was also in some sense driven by a fundamental law that the Universe wants to minimise 'free Energy'. So it was also virtually inevitable for life to emerge. It's just that the underlying laws are probabilistic.
*This is of course speculation, but seems fairly reasonable given the apparent speed with which life emerged, and also given the large numbers of particles involved.
*This is of course speculation, but seems fairly reasonable given the apparent speed with which life emerged, and also given the large numbers of particles involved.
Chance has different connotations depending on what you're talking about
If I close my eyes and throw a tennis ball at a bucket 100 yards away what would you think of the chance it goes in?
If everyone on the planet tries it what would you think of the chances that someone gets it in.
This is the thing about the nature of life on Earth - it appears only to have happened once
Once was enough
It's just that we are the once so it can look pretty improbable to us - but we don't take into consideration all the billions of places it hasn't happened.
This is the Weak Antropic Principle
http://
You should take a look at the more contentious Strong Antropic principle (I have a feeling it might appeal to you)
If I close my eyes and throw a tennis ball at a bucket 100 yards away what would you think of the chance it goes in?
If everyone on the planet tries it what would you think of the chances that someone gets it in.
This is the thing about the nature of life on Earth - it appears only to have happened once
Once was enough
It's just that we are the once so it can look pretty improbable to us - but we don't take into consideration all the billions of places it hasn't happened.
This is the Weak Antropic Principle
http://
You should take a look at the more contentious Strong Antropic principle (I have a feeling it might appeal to you)
Actually, on the subject of RNA, it is still 'odd' that such a molecule exists.
Purine and pyrimidine precursors make sense to me, as they seem to be a logical progression from bashing amino acids together in boiling water for long enough. (Note: you first have to accept that amino acids form spontanously when you combine lightning strikes with primordial earth atmospheric mix})
The sugar-phosphate backbone is a real puzzler though. Sugars are a temporary violation of the laws of thermodynamics:- energy must be captured and deployed (and you'd expect this to require higher-order molecular 'machines' to achieve this) in the formation of the right chemical bonds, joining together CO2 molecules (or some analogue) in the right orientations to make the ring-shapes which sugars are.
It could be that, in the 'soup', there was this logical progression of amino acids combining into polypeptides spontaneously (but with difficulty, such as requiring high temperature and pressures to procees without enzymic assistance) and, upon aquiring the last piece of the jigsaw by a chance collision finally take up a 3D shape which had what we now recognise as catalytic activity.
This new molecule wanders like a ship adrift in space. It could spontaneously break apart (denaturation) or it could bump into the molecules it is uniquely shaped to bind to. Bind two molecules, bring them into close proximity and reactions which used to spontaneously reverse now go to completion.
New chemical 'species' appear in the soup. New reaction possibilities arise. Reaction 'pathways' become possible.
To produce the kind of molecules that cell membranes are made of requires a whole series of reactions so there is still a long way to go before the 'soup' approaches anything like the complexity of a single-cell life form.
Purine and pyrimidine precursors make sense to me, as they seem to be a logical progression from bashing amino acids together in boiling water for long enough. (Note: you first have to accept that amino acids form spontanously when you combine lightning strikes with primordial earth atmospheric mix})
The sugar-phosphate backbone is a real puzzler though. Sugars are a temporary violation of the laws of thermodynamics:- energy must be captured and deployed (and you'd expect this to require higher-order molecular 'machines' to achieve this) in the formation of the right chemical bonds, joining together CO2 molecules (or some analogue) in the right orientations to make the ring-shapes which sugars are.
It could be that, in the 'soup', there was this logical progression of amino acids combining into polypeptides spontaneously (but with difficulty, such as requiring high temperature and pressures to procees without enzymic assistance) and, upon aquiring the last piece of the jigsaw by a chance collision finally take up a 3D shape which had what we now recognise as catalytic activity.
This new molecule wanders like a ship adrift in space. It could spontaneously break apart (denaturation) or it could bump into the molecules it is uniquely shaped to bind to. Bind two molecules, bring them into close proximity and reactions which used to spontaneously reverse now go to completion.
New chemical 'species' appear in the soup. New reaction possibilities arise. Reaction 'pathways' become possible.
To produce the kind of molecules that cell membranes are made of requires a whole series of reactions so there is still a long way to go before the 'soup' approaches anything like the complexity of a single-cell life form.
//hypo; Could you please explain the difference between accepting a theory and believing a theory?//
Not in any categorical sense. I could give you my personal opinion on the matter but I'm not sure that would be of any use to you.
If you need me to say something specific so as to advance your side of the debate by one more step then just pretend I have uttered the required trigger words and go ahead.
//my dictionary defines them as interchangeable. //
That is it's problem, not ours! :-D
Not in any categorical sense. I could give you my personal opinion on the matter but I'm not sure that would be of any use to you.
If you need me to say something specific so as to advance your side of the debate by one more step then just pretend I have uttered the required trigger words and go ahead.
//my dictionary defines them as interchangeable. //
That is it's problem, not ours! :-D
This accepting and believing a theory thing come back to the old accusation of 'faith' in Science.
As ever I come back to Popper and falsifiability.
This is the acid test
Ask a scientist what it will take to change his mind. Doesn't matter how extreme - hand of God writing 'Believe' in the Sky will do. If he say's nothing will change his mind - he's guilty of 'faith'.
I've yet to meet a theist who will give me an example of something that will make him change his mind.
This is the difference between Belief in Science and Belief.
The former is an opinion based on observation willing to change when observations change
The latter is dogmatic and will deny all observations and logic
As ever I come back to Popper and falsifiability.
This is the acid test
Ask a scientist what it will take to change his mind. Doesn't matter how extreme - hand of God writing 'Believe' in the Sky will do. If he say's nothing will change his mind - he's guilty of 'faith'.
I've yet to meet a theist who will give me an example of something that will make him change his mind.
This is the difference between Belief in Science and Belief.
The former is an opinion based on observation willing to change when observations change
The latter is dogmatic and will deny all observations and logic
If you are going to reference Dawkins, Khandro, surely it would be better to offer the full quote rather than just your cherry-picking summation?
And if you have read "The Selfish Gene" then you should be aware that Dawkins has gone into some details beyond merely attributing it all to "chance done it" as to how complex molecules may have formed. So what part of that process as described prompts your question? Specifics are your friend in this issue.
Take heart though; Abiogenesis has several different theories, with scant evidence to date supporting any of them. After all, we have only been properly investigating the process for 50-60 years or so; the process itself took hundreds of thousands of years!
You could, if you wish,believe that the formation of replicator molecules was evidence of a "divine spark", testimony to the notion of a god. If you ask scientists who do profess faith, often its actually this kind of god they profess a belief in, rather than the rather more personal god of the abrahamic religions.
The point though is surely that there are plausible hypotheses offered that require no divine inspiration - so why invent such divinity?
And if you have read "The Selfish Gene" then you should be aware that Dawkins has gone into some details beyond merely attributing it all to "chance done it" as to how complex molecules may have formed. So what part of that process as described prompts your question? Specifics are your friend in this issue.
Take heart though; Abiogenesis has several different theories, with scant evidence to date supporting any of them. After all, we have only been properly investigating the process for 50-60 years or so; the process itself took hundreds of thousands of years!
You could, if you wish,believe that the formation of replicator molecules was evidence of a "divine spark", testimony to the notion of a god. If you ask scientists who do profess faith, often its actually this kind of god they profess a belief in, rather than the rather more personal god of the abrahamic religions.
The point though is surely that there are plausible hypotheses offered that require no divine inspiration - so why invent such divinity?
Before I forget; one of the reasons we're all here is that DNA is such a fallible molecule.
Hit it with certain chemicals, or UV-B wavelengths, or cosmic rays, or alpha/beta/gamma radiation and chemical bonds can rearrange themselves. Sometimes the damage is serious enough to lead to cell death, sometimes the damage is repairable and sometimes the damage is sub-lethal and thus inheritable (in eggs/sperm, specifically).
Mutations put variety into a species and either improve its degree of fit to its environment or become the branching point for new species further down the generations. The stuff of life, in a wierd way. ;-)
Susceptibility to damage is also the reason why we have to reproduce. A hypothetical 'eternal molecule' will just accumulate more and more damage as time passes and will inevitably cease to function. For most life forms you only need one functioning copy of a gene to survive and produce children of their own.
Is is only within the last 12 months that I've heard a TV programme put forth the concept that we all have 'bad genes' within us (typically about 10 mutations each) but by shuffling genes between individuals, down the generations, we can work around these faults, as a species.
Hit it with certain chemicals, or UV-B wavelengths, or cosmic rays, or alpha/beta/gamma radiation and chemical bonds can rearrange themselves. Sometimes the damage is serious enough to lead to cell death, sometimes the damage is repairable and sometimes the damage is sub-lethal and thus inheritable (in eggs/sperm, specifically).
Mutations put variety into a species and either improve its degree of fit to its environment or become the branching point for new species further down the generations. The stuff of life, in a wierd way. ;-)
Susceptibility to damage is also the reason why we have to reproduce. A hypothetical 'eternal molecule' will just accumulate more and more damage as time passes and will inevitably cease to function. For most life forms you only need one functioning copy of a gene to survive and produce children of their own.
Is is only within the last 12 months that I've heard a TV programme put forth the concept that we all have 'bad genes' within us (typically about 10 mutations each) but by shuffling genes between individuals, down the generations, we can work around these faults, as a species.
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