Evolution

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spot
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Evolution

Post by spot »

A bacterium which uses no oxygen or carbon dioxide in its metabolism is described at http://news.bbc.co.uk/1/hi/in_depth/7663927.stm

The most telling detail in there for me is "It was identified in DNA". This bacterium, like every other life form ever detected, uses DNA to encode its genetic heritage and to express itself as an individual.

I would venture to guess that a significant fraction of the DNA in that bacterium is also found in you or me.

I assume that the evolutionary steps to go from an inorganic environment to a DNA-based lifeform are far more complex than the steps to go from the common ancestor of that bacterium and people to the modern world. I have absolutely no idea what those early steps involve. The ones after the common ancestor arrives are trivially easy to follow by comparison, it's like following a thousand footsteps across a field, each representing a type of event, and analysing only the very last of them.

What stable states of life are there before DNA takes the reins?

Why has nobody yet found one? That's the big puzzle, to me - that there's not even small outposts of these intermediates alive today. There are undoubtedly places where competition wouldn't have driven such intermediaries from their niches. Is it that nobody's looked yet? Or is it that the possible niches are so small by comparison to the world in which they developed that they've just not clung on for those billions of years?
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spot
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Evolution

Post by spot »

You're suggesting that it was a single-step process, from a purely inorganic substrate there was a key moment at which all the bits came together in one place and organized themselves into a DNA replication machine.

That's a God-event. I'd much rather, as with all the subsequent evolution steps which don't demand a God-event, we looked for a succession of processes which each gave rise to the conditions necessary for the next and which were each stable enough to successfully await the next event.

Just because it's hard to fathom doesn't mean it's impossible, it just means we've not experimented sufficiently.
Nullius in verba ... ☎||||||||||| ... To Fate I sue, of other means bereft, the only refuge for the wretched left.
When flower power came along I stood for Human Rights, marched around for peace and freedom, had some nooky every night - we took it serious.
Who has a spare two minutes to play in this month's FG Trivia game! ... My other OS is Slackware.
SlipStream
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Evolution

Post by SlipStream »

sorry if this sounds negative but the way things are going mankind'll die out b4 they've a chance to expaned
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Galbally
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Evolution

Post by Galbally »

Its a series of interesting questions, I suppose what one must always keep in mind from the human perspective is the enourmous amount of time that all this self-organization has occurred over. I try to think about it, but its usually overwhelming. We do know that the basic building blocks amino acids are very readily made given the right conditions, and that stability seems to be promoted by the organization of these amino acids into the RNA and DNA structures, which of course have become self-replicating and now dominate every niche in the planet.

My own guess about the absense of any other form of code other than the DNA which every living thing is based upon, is that at the level of self-replicating amino acids and proteins, the rewards of being the most sucessful replicator was the complete overwhelming of any other form of biochemical replicator, and once that foothold was established by DNA-based forms, it was impossible for any other replicator to compete, hence the 100 percent dominance of DNA now, and the question of whether there could have even been another type of replicator.

I suppose the really big underlying question is why all this organization on such a complex level, which is very difficult to answer other than in vauge philosophical or religious terms, in that the universe seems to be based on laws that promote inherent organization for some reason and life seems to be one of the functions of this organization, unfortunately from a human perspective we ourselves are a part of this process of evolving pattens of complexity, so its hard for us to have any sort of perspective upon it.
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Evolution

Post by spot »

I agree entirely with what you say Galbally. By all means make the first step employ amino acids which are, as you say, readily available from non-life processes. By all means have them self-organize into DNA, large though that step may be - I have no problem with that as a single step. What leaves me totally lost is the extent of code which has to be put in place before self-replication can happen and functionality exist. What steps are needed to go from any number of random assemblies on a DNA construct and the emergence of functionality? That's the step too far, regardless of the length of time available. You're agreed that you need a chance event to bring those amino acids into conjunction in the first place. That's one, and it didn't randomly generate functional code. Then it happens again, on a different occasion, and again and again, all separate fortuitous events. Bear in mind that these are themselves remote and unlikely conjunctions. What's the simplest functional code that'll self-replicate? I think it's an immensely complex program, that simplest possible code set.

It's the sort of thing ideally suited to computer simulation. That's the way I'd see it being cracked but it's rather a larger problem than this distributed protein folding FG's been engaged in. It's not just a developmental jump to go to what I'm talking about, it's a different scale altogether.

Assume that such a sequence of steps can be simulated and that the minimum possible DNA sequence can be demonstrated which is self-replicating, granted the optimum environment. The single step you're faced with is assembling that sequence randomly because there's no earlier stage which fulfils my requirement of being a stable step which can exist indefinitely waiting for the next step to occur. That's the jump from non-life to life. It's the jump which leaves me puzzled. It seems a huge one to assume to be possible in the single universe we see around us.
Nullius in verba ... ☎||||||||||| ... To Fate I sue, of other means bereft, the only refuge for the wretched left.
When flower power came along I stood for Human Rights, marched around for peace and freedom, had some nooky every night - we took it serious.
Who has a spare two minutes to play in this month's FG Trivia game! ... My other OS is Slackware.
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Evolution

Post by spot »

You're just playing with the word "organic" - I was brought up to understand it to mean carbon-chained. These amino acid bases are commonplace in nature from chemical processes which don't involve life.

Are there any viruses which aren't DNA/RNA coded? Whether you start off with something that eventually becomes a virus or something that eventually becomes a bacterium doesn't affect my core puzzle - how you get that minimum coded information set to come together when nothing less informationally-dense can build toward that starting point. All the information has to be brought into being in one moment in time in one place out of components which aren't alive.
Nullius in verba ... ☎||||||||||| ... To Fate I sue, of other means bereft, the only refuge for the wretched left.
When flower power came along I stood for Human Rights, marched around for peace and freedom, had some nooky every night - we took it serious.
Who has a spare two minutes to play in this month's FG Trivia game! ... My other OS is Slackware.
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Evolution

Post by spot »

There's a name for long-chain silicate molecules. They're called asbestos. I have no idea what aspect of silicon chemistry could be used to produce molecules with the subtle variation that carbon achieves. Certainly there's nothing recognised as alive on this planet which isn't totally dependent on DNA/RNA for storing and expressing its replication instructions.
Nullius in verba ... ☎||||||||||| ... To Fate I sue, of other means bereft, the only refuge for the wretched left.
When flower power came along I stood for Human Rights, marched around for peace and freedom, had some nooky every night - we took it serious.
Who has a spare two minutes to play in this month's FG Trivia game! ... My other OS is Slackware.
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