Starboard Tack wrote: What he says is exactly what I have been saying. The current universal code can't change without lethal consequences. I grant it could change, but if it did it would be lethal. It hasn't changed, presumably because what changes have occurred have been lethal. I really don't know why you think I am distorting what he said, since I am simply repeating his words.
I think you are distorting (albeit unintentionally) his words because you are not using them in context. It is easy to take someones words verbatim and make them say something they do not mean.
It says that the RNA world is a virtual impossibility. Proof of concept experiments work in the lab, but cannot be extrapolated to early earth chemistry. The oxygen ozone paradox is one of many reasons. With oxygen, no pre-biotic chemistry since the compounds react vigorously with oxygen. Without oxygen, no pre-biotic chemistry because you would have no ozone and the UV light would destroy the pre-biotic chemistry. Thermal vents appear to be out since all the ocean's waters cycle through those vents and are super heated under pressure every 10 million years. The RNA world hypothesis is deader than Elvis. Don't take my word for it. Here is a link to a group in favor of panspermia that does a good job of laying out just some of the problems:
http://www.panspermia.org/rnaworld.htm
Current Opinion in Chemical Biology
Volume 8, Issue 6, December 2004, Pages 629-633 The importance of prebiotic chemistry in the RNA World Hughes et al.
Conclusions
If the sequences of functional nucleic acids are by and large multivariate and plastic, then how can we more concretely learn about the conditions that prevailed at origins? Paradoxically, it seems like we will learn much more about origins from experiments that are hard (and thus constrain possibilities), rather than experiments that are easy. In this regard, the hard-won knowledge from experiments that have explored prebiotic chemistry is still the surest window onto any putative RNA World. The experiments begun by Miller in 1953 [55], which effectively gave birth to the modern approach to origins as an experimentally testable science, began to delimit the molecular environment of the abiotic world that preceded the era of RNA. For example, it is clear that purine nucleobases must have been present in the original RNA World, because of the simplicity of the chemistry involved in their creation [56.] , [57.] and [58.] . However, the formation of ribonucleotides has proven difficult (although recent work by Benner may yet resolve this perennial problem [59]). This is one reason that researchers in the field have turned to nucleic acid surrogates, such as peptide-nucleic acids, as possible replicators at origins [60.] , [61.] and [62.] . However, if we go by such criteria as a guide, then it seems likely that the RNA World may not have been the pristine RNA-dominated ecosystem sometimes envisioned, but simply a transient go-between during the relatively rapid evolution of a DNA"protein world [63].
Update
Recent works by Springsteen and Joyce [64], when combined with the previous work from Steve Benner's Group [59], have demonstrated that ribose could have been present in the prebiotic soup. However, the efficient abiotic synthesis of nucleosides from ribose, and the standard nucleobases remains to be demonstrated.
So this is just one paper, but there are others. I dont see how the RNA world is considered "dead"
The total lack of chemical evidence for its existence, no chemistry that could have produced it on earth, insufficient quantities that could be delivered by extraterrestrial sources, etc. Mainly that there isn't the slightest evidence it ever existed.
ibid.
Other problems with DNA 'evolving' in the first place is the time available. According to Gerald Joyce, 400 million years minimum would be required, yet sterilization events were occurring right up to the point where first life appears 3.8 billion years ago.
Citation?
Gerald F. Joyce, "The Rise and Fall of the RNA World," p 339-407 v 3, The New Biologist, 1991
Ill check that out later.
My apologies. You're right, I have no idea what you believe. I refer to texts rather than the original papers because I have no reason to doubt the citation references from people who disagree with my views simply because they disagree with me. Apparently you do not share that view. Unfortunately, Fry rarely seems to reference papers, just authors and dates. No very helpful tracking down the resource.
Understood. My issues with books is the general lack of peer review, the fact it is an interpretation (often) of the primary literature, it is much harder to verify (books are harder to come by than published articles) and it is much easier for someone to take parts of a book out of context and distort which I have seen done FAR too many times. I like the books, they have their place, but unless I have, or cant easily get a copy of what is being sourced, I am skeptical of what is ever claimed.
Not so much. Since you may not take the time to review the panspermia site, here is their summary:
It goes without saying that the emergence of this RNA world and the transition to a DNA world imply an impressive number of stages, each more improbable than the previous one " Franois Jacob, 1997
1. There is no remnant or trace evidence of precellular life anywhere today. That it ever existed is entirely conjectural. (note: this would be your imaginary pre-biotic soup.)
2. Although its emergence from nonliving matter is hard to conceive, precellular life must have appeared almost immediately. (note: as I said, no time at all.)
3. There was almost no time for precellular life to evolve into the simplest bacterial cells. (note: ditto. no time at all.)
4. Precellular life has never been created in a lab.
5. In spite of the RNA world, there is no consensus on the model for precellular life. (note: as I said. the RNA world is deader than Elvis.)
While not part of the summary, this is also worth noting:
Incidentally, when one starts thinking along these lines, one must consider the unthinkable, i.e., that the length of time that RNA-based proteins actually bestrode the earth might be zero.
I am still neutral to the panspermia hypothesis. I dont like the fact they seem to rely on disproving terrestrial origins, therefore panspermia (much like how many creationists say if evolution is wrong, God must be true). I think they would be better off letting their theory stand on its own merits.
