Abiogenesis

[olivergringold]

This is my first post, so feel free to label me as a n00b or flame me to your heart's delight. I'm going to take the opportunity afforded by my first post to ramble unendingly, and more specifically to the ends of naming the basic components of what the first unicellular organism needed to have to kickstart evolution and, given an old Earth, name a plausible way in which that may have formed without relying entirely on chance. Ready? Too bad.

The cell's main feature is its DNA, or deoxyribonucleic acid. This is a sequence of four different chemicals: adenine [A], thymine [T], guanine [G], and cytosine [C], which are held in a chain by a linking phosphate "backbone." Since A and T naturally bond chemcially, and G and C as well, DNA forms in a double-helix shape, with each side of the helix being the chemical opposite of the other (As become Ts, etcetera). This all being obvious and boring, all a First Organism would need is a long phosphate chain and high concentrations of adenine, thymine, guanine and cytosine in the general vicinity.

Obviously, though, for life to occur it's just not that simple. The chemicals need to bond with the phosphate chain, and there needs to be an "energy" source for the DNA to split and replicate, to permit variation. An experiment attempting to replicate this was carried out, which resulted in proteins. This was not a success, however, as said proteins were not capable of creating, or even being classified as, life. Consider, however, an old Earth:

The spinning of the Earth's core has generated a magnetic field preventing many of the sun's ultraviolet, X-Ray and Gamma Rays from penetrating into the Earth's atmosphere, and the upper layers of magma begin to cool. High concentrations of water condense in the crevices between the crusts, and violent electric storms frequently bombard the planet. All of the chemicals required to give rise to life are already there, and the energy required to bond them is available in abundance. Still, however, the odds of all the right chemicals happening to be in the same place at the right time are none that any wise person would bet on. Consider, though, that chance may not be the only factor at play.

Vines are often known to travel up the stems of plants in a perfect spiral shape. This is a very fascinating phenomenon, as nobody would suspect that lurking in the DNA is an instruction for the vine to travel in such a fashion. How on Earth (no pun intended) could it be occurring by chance? Indeed, however, it is not. The vine is simply distributing its weight. According to the known laws of physics, the most efficient way for a lengthy object to distribute its weight as it moves upwards is to travel in a spiral. The vine doesn't know this any more than Newton's apple "knew" about the gravity controlling it. Still, though, the organism is not only bound by its DNA, but also by the world around it.

A and T, as well as G and C, combine without any external intervention during cell reproduction. When faced with each other, the connection is instantaneous as a result of the chemical constructions of their bonds. Just as the physics may control the plants, here it is the chemistry which controls the cells. I posit, then, that it is plausible, if not outright likely, that because many of the chemicals involved were already predisposed to creating chemical bonds, the probability of abiogenesis occurring on an Old Earth extends well beyond that of pure chance.

What does all of this mean? Absolutely nothing, save for my being an exceptionally pretentious and lengthy writer. There's no known way for us to turn the clock back and see what our planet really was like in its infancy, and recent studies about the laws of causation suggest that we may never know precisely how abiogenesis happened on Earth, if not in general. Though, in closing, for all those who purport Intelligent Design and preach that God must have been He Who Turned On Evolution, remember that it only had to be possible, not likely, and that it only had to happen once.

[The Duke of Vandals]

I fail to see how it offers to explain much of how the first cell arose. Even if chemicals were predisposed to create chemical bonds, it's still very far from being able to explain the origin of the first cell.

Unfortuneatly, as a Christian, you lack any valid alternative explanation. A designer can never be a long term explanation because the designer requires a designer.

Let Dawkins help you put things into perspective.

The origin of life on this planet — which means the origin of the first self-replicating molecule — is hard to study, because it (probably) only happened once, 4 billion years ago and under very different conditions from those with which we are familiar. We may never know how it happened. Unlike the ordinary evolutionary events that followed, it must have been a genuinely very improbable — in the sense of unpredictable — event: too improbable, perhaps, for chemists to reproduce it in the laboratory or even devise a plausible theory for what happened. This weirdly paradoxical conclusion — that a chemical account of the origin of life, in order to be plausible, has to be implausible — would follow if it were the case that life is extremely rare in the universe. And indeed we have never encountered any hint of extraterrestrial life, not even by radio — the circumstance that prompted Enrico Fermi's cry: "Where is everybody?"

Suppose life's origin on a planet took place through a hugely improbable stroke of luck, so improbable that it happens on only one in a billion planets. The National Science Foundation would laugh at any chemist whose proposed research had only a one in a hundred chance of succeeding, let alone one in a billion. Yet, given that there are at least a billion billion planets in the universe, even such absurdly low odds as these will yield life on a billion planets. And — this is where the famous anthropic principle comes in — Earth has to be one of them, because here we are.

If you set out in a spaceship to find the one planet in the galaxy that has life, the odds against your finding it would be so great that the task would be indistinguishable, in practice, from impossible. But if you are alive (as you manifestly are if you are about to step into a spaceship) you needn't bother to go looking for that one planet because, by definition, you are already standing on it. The anthropic principle really is rather elegant. By the way, I don't actually think the origin of life was as improbable as all that. I think the galaxy has plenty of islands of life dotted about, even if the islands are too spaced out for any one to hope for a meeting with any other. My point is only that, given the number of planets in the universe, the origin of life could in theory be as lucky as a blindfolded golfer scoring a hole in one. The beauty of the anthropic principle is that, even in the teeth of such stupefying odds against, it still gives us a perfectly satisfying explanation for life's presence on our own planet.

http://www.edge.org/3rd_culture/dawkins ... index.html


The bottom line is we don't know... but we don't need to know what happened to toss out what we know DIDN'T happen.

[Pista Gyerek]

Slightly off-topic, it's worth noting that the components of the cell are hardly ideal...an intelligent designer easily could have created something far more efficient. Instead it, like all forms of life, high and low, is constructed much like a Rube Goldberg machine, stacking function atop function until the necessary end is reached by mind-blowingly inefficient means.

If you want to make assumptions about how an intelligent designer would or wouldn't create something, you need a Discovery Institute fellowship.

[olivergringold]

That or a Templeton Prize. I'll pass on both, in favor of "intelligence."

[QED]

I fail to see how it offers to explain much of how the first cell arose. Even if chemicals were predisposed to create chemical bonds, it's still very far from being able to explain the origin of the first cell.

It's a long way alright. But has nobody has sat around for whole lifetime (let alone tens or hundreds of millions of years) to see what natural "molecular evolution" might come up with. What can we say about molecular chemistry that prevents any given valid molecular structure arising as a statistical outcome? Evolution by natural selection would find itself just at home working on prebiotic molecular structures, as full-blown biotic ones.

I think it's fair to say that the argument therefore revolves around the question of whether or not an imperfect replicator (no matter how crude -- we're a long way from whole cells here) could make a chance appearance from among all the natural chemistry going on in the prebiotic environment. Any population of imperfect replicators has the potential for considerable expansion -- as any mutation that makes an individual replicate more often, will result in more offspring bearing that approximate ability. This "design" (ho ho) then becomes the norm for the population and so on in, what seems like, a perfectly reasonable ramp (of barely discernible incline) all the way up towards (three billion years later!) something as complex as a eukaryotic cell.

Stuart A. Kauffman has given much thought to the origin of complexity in biological systems and has developed "models" of random networks exhibiting a kind of self-organization that he terms "order for free." This discussion might be of interest to anyone who hasn't come across it before.

[olivergringold]

For the purposes of this thread, since nobody has yet refuted my position that a First Replicator would not have had to rely solely on chance, the odds are far greater in our favor than those you present to otseng, QED. Designists oughtn't have the opportunity to weasel their way out here.

[QED]

I posit, then, that it is plausible, if not outright likely, that because many of the chemicals involved were already predisposed to creating chemical bonds, the probability of abiogenesis occurring on an Old Earth extends well beyond that of pure chance.

...Though, in closing, for all those who purport Intelligent Design and preach that God must have been He Who Turned On Evolution, remember that it only had to be possible, not likely, and that it only had to happen once.

When I refer to "an imperfect self-replicator appearing by chance from natural chemistry" there is already an element (no pun intended) of predisposition in the nature of the chemicals. This has been pounced upon elsewhere as evidence that a provident creator deliberately "rigged" the periodic table to create atoms with particular bonding tendencies to promote the assembly of organic molecules. Of course most Designists would go on to add that the assembly of proteins would also require "intelligent intervention" when we would see NS supplying all the apparent smarts.

I'm pretty sure otseng would take your suggestion about the molecular predisposition as strong supporting evidence for an Intelligent Designer of the periodic table. What would you make of that I wonder?

[olivergringold]

If we were being intelligently designed then it would make sense that our Magic Man wouldn't necessarily want to give us the chemicals that bond easiest as much as he'd want to give us the chemicals that have the highest possible yield during their lifetime. ATGC is all we've ever known, but I have very little reason to believe that there aren't other chemicals, no less arbitrary, which could have made us live longer, grow faster, and generate more biological benefit from receiving lower amounts of energy from external sources. I cannot speculate on what these might have been, as the only components of our body which deal with the chemicals in our DNA have been "designed" (ha ha) from the ground up to deal specifically with ATGC.

The fact that our particular chemicals naturally bond means that a Designer's hand wouldn't be needed for them to come together. It does not, in and of itself, entirely rule out the notion of Design, but it certainly isn't a purporting argument.

[nine dog war]

The theory of evolution covers only why there is a diversity of creatures, not the existence of life itself. It leaves room for all the fantisiful ideas of creators.

[QED]

The theory of evolution covers only why there is a diversity of creatures, not the existence of life itself. It leaves room for all the fantisiful ideas of creators.

The theory of evolution covers only why there is a diversity of creatures, not the existence of life itself. It leaves room for all the fantisiful ideas of creators.

ToE pertains to the origin of species, yet the principle of Natural Selection is something that is general enough to order anything capable of making approximate copies of itself. This would lend itself to molecular evolution.