So your earlier claim was vacuous. Got it.
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It seems likely that there was some sort of proto-life before there was DNA.
It does not require faith to accept that there is a lot we do not know about the origin of life. Yet it still seems likely that the origin was in natural events.
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What do you mean it seems likely? How did you determine it was likely? How do you bridge from porto life to DNA life?
How have you determined it is likely? There is very little evidence of a bridge. You appear to have faith it was natural as you are making a statement based on gut feel. Origin of life studies are small speculative pieces of the process at best.
Neil, what do you think happens when you poke a hole in a bacterial cellular membrane and the contents move into a test tube solution?
It seems likely that DNA is too complex to have just occured by random molecular motion. A “metabolism first” scenario is probably how it started. It would have looked very different from current life, but might have set the stage for current forms of life to evolve.
“Seems likely” is a very weak statement. And it is only an opinion, not a truth claim. I’m open to evidence for other possibilities.
I don’t know. But that has no relation to anything that I have said.
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Rubbish. DNA does not create anything.
The origin of these sequences in extant organisms is well-understood. Mutation and recombination explain their origins.
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Spilling out its cytoplasmic contents by comprising membrane integrity will kill a bacterium. What does this have to do with anything Neil said?
For one, the molecule which catalyzes protein synthesis is RNA, a ribozyme. This is serious evidence for a past (and present) RNA world.
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This is Bill trying to perform an experiment in the origin of life. If abiogenesis were true, he reasons, a solution of cellular components should spontaneously assemble into a cell. Since that doesn’t happen, abiogenesis didn’t happen either. QED.
You can perform similar experiments to show other things. For example, if you pass a sponge through a filter that separates all its cells, they will spontaneously reassemble into a new sponge. This shows that the evolution of multicellularity is easy. You can also assemble a pile of dust, but it will never turn into a human being. This shows that the creation of Adam didn’t happen. Science is fun!
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It’s a demonstration of a current RNA world. That life started as RNA-based should be obvious from the fact that it is still RNA-based and has never been anything else, so far as anyone is aware.
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I agree, but I was speaking from a historical perspective, when RNA-based catalysis preceded the predominant protein-based form of catalysis we see today. The ribosome’s ribozyme (and things like self-splicing introns) is a functional souvenir from that time period.
PS: i modified my earlier comment to reflect your input.
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I don’t buy the idea that life started as RNA-based (RNA-first). I think RNA replaced something before it. I subscribe to the metabolism-first hypothesis.
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I suspect that chemical cycles were active prior to RNA-based life, but I don’t think there was anything you could call ‘life’ then.
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The peptidyl transferase is more than just a souvenir, a relic. It is the very heart of all life as we know it today. IMO, it is more accurate to consider proteins and DNA as spin-offs of a still very-active RNA World.
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I didn’t say there was but I guess my mentioning of the metabolism-first hypothesis led you to think so. Whether RNA-life forms emerged first is certainly unknown, but there is good evidence they did exist.
Sure it is at the heart of life, but considering that proteins do almost everything now we can say it is a relic in some sense.
Proteins are successful usurpers I guess thanks to their unique features.
I understood that to mean you think there was life before RNA-based life, specifically something in line with the metabolism-first hypotheses. I don’t think anything suggested by any of the metabolism-first hypotheses I’m familiar with qualifies as life, nor would anything between them and RNA.
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Sorry for my imprecise language. Let me try to clarify. RNA-first (or genetics-first) scenarios tend to assume RNA-based life-like systems were somehow around at the earliest time points in the origin of life without trying to account for the synthetic pathways that could continuously replenish precursor stocks and that doesn’t sit well with me. Instead, I think there were geochemical cycles which produced the starting materials needed for any sort of world to exist be it an RNA, DNA or protein world. So when I said I didn’t buy the idea of RNA-based life at the start, I really meant that there had to exist a relatively stable means of chemical synthesis to prior to the emergence of any world.
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Who said anything about RNA-first? I certainly didn’t. I just said the first life (along with all subsequent life) was almost certainly RNA-based. No claims to the nature of the prior chemistry was made by me, excepting that those chemistries were not ‘life’.
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Oops! I just realized. Sorry.
How do you know the “first life” was “almost certainly RNA-based”? How did you rule out the possibility of other life forms based on some other polymers existing alongside RNA-based life?
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DNA makes a great template system for storing and replicating genetic information. Proteins are great as catalysts. RNA does both jobs. In RNA you have both chicken and egg!
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I haven’t ruled out the possibility, that would be ‘definitely RNA-based’. But there is no other chemistry capable of being life that we know of, proposed alternatives are, for various reasons, less plausible than just riding RNA all the way back.
Do not multiply entities beyond necessity.
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Super. I just wanted to see a bit of cautiousness sprinkled in, but I agree with you.
Absolutely. The RNA-world best explains the available data.
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