[QUOTE]Originally posted by Quetzal: [B]Apologies in advance for the length of this post. Enjoy!
Even though abiogenesis – the origin of life from non-life – is not related to the validity or falsehood of evolutionary theory, it is an interesting subject in its own right. Although evolutionary theory does not rest on the truth of abiogenesis, creationists in particular seem to demand that a non-supernatural origin of life be “proven” before evolution can be accepted.
I suppose your right, there is theistic evolution. But surely, if, hypothetically, it becomes clear that abiogenesis is not feasible by natural means, then there is no reason to accept materialistic evolution. Once a Creator is established as a neccessary condition for life, would not Creation make a lot more sense than evolution?
Quetzal: The modern chemical composition of the Earth is mostly Fe, Mg, Si, and O, with the other elements contributing 5% of the total. Life originated as a result of chemical reactions occurring (largely) in the atmosphere followed by reactions in the primeval oceans and lakes. The atmosphere at the end of the Hadean Period (~4-4.2 gya) is primarily composed of variable amounts of CO2, N2, SO2, H2S, S, HCl, B2O3, and smaller quantities of H2, CH4, SO3, NH3 and HF (but no O2), due partly to outgassing from volcanoes, and partly to the reaction of condensing water vapor (formed as the Earth cooled) with minerals such as nitrides (hence NH3), carbides (hence CH4, CO, etc.) and sulfides (hence H2S). There was no free oxygen (any free O2 ...
Bart007: What if there was free O2, would that have any adverse affect on the formation of life's molecules, or are you simply pointing out that there simply was not any O2 in the prebiotic atmosphere?
quote:Originally posted by joz: Great post Quetzal, thanx.....
Q)I was under the impression that one of the problems with The Biotic Soup Hypothesis of abogenesis was the low abundance of sugars produced and the lack of long chain fatty acids (in the Urey/Miller experiments). Has anything new cropped up that makes this less of a problem?
Wow, try and get some work done for one day, and look what happens! I'll try and answer everyone's posts (or quibbles) as I get the opportunity.
Anyway, joz, you're absolutely correct. One of the crucial problems with the experiments was their apparent inability to synthesize complex sugars, specifically ribose. Ribosomal RNA, of course, was the autocatalytic self-replicator that Cech discovered. It wasn't so much that they didn't get sugars or that the chemistry wasn't correct (after all, you get HCHO forming photochemically in the atmosphere today, then by Formose reaction you get isomers like formaldehyde (CH2O)6 [detectable in modern rainwater]. It's a fairly simple step to re-arrange things into C6H12O6). Getting from there to ribose is mostly a question of concentration and energy with the right catalyst.
Miller's biggest problem was (and remains) trying to get rRNA to form spontaneously. That and the fact that RNA couldn't be the first replicator simply because it is really unstable and formed in very tiny quantities. It wasn't until only a couple of years ago that it was found peptides (which are REALLY easy) were able to bond to the 5' site on the nucleic acid forming a stable hybrid polymer: pRNA.
You still have major problems with concentration and getting the nucleic acids to line up properly - something that hypothesis 2 and both 3's accomplish by using inorganic templates. Fe4S4][SFeS]2), which is structurally identical to the active center of ferredoxin (the Fe4S4).
I believe every experiment you refer to was intelligently designed and controlled to get the intended results. That none of these experiments were every done replicating actual prebiotic atmosphere conditions. Peptides may form easily in the presence of amoni acids, but none that are of any use to life.
To make life, we need amino acids, sugars, bases, and phosphates. This gives us other catch 22's. You need formaldehyde to make sugars, but formaldehyde fixes amino acids so that they do not react. Methane polymerizes formaldehyde, but must be present to make amino acids. Amino acids plus bases destroys formaldehyde. Calcium and magnesium in our oceans destroy phosphates, you can't get phosphates in oceans. Heat needed to make amino acids also destroys the amino acids.
You have presented abiogenesis in the best light possible. I will post a new topic on abiogenesis and which will reflect why I believe abiogenesis is impossible as based upon scientific considerations only.