- Nov 11, 2019
To understand the evolution of proteins and nucleic acids, one needs to understand the planet history... although it may seem impossible to have this kind of process today, it is possible that in the past (1M of years ago) it was possible... who knows?!The problem is more than speculative evidence for some anaerobic microbe producing a phosphine signature. The problem goes back to where that microbe came from. The evolution of proteins and nucleic acids has to come first. How likely is that in clouds above Venus, or above anywhere...leading to a LUCA-type microbe living in the clouds?
Not likely in clouds.
One would have to question the meaning of "large amounts of water."Large amounts of water are not needed to get life started.
The most likely theories of abiogenesis require a continuous aqueous milieu at a stable, moderate temperature. Fluctuations in heating/cooling and drying would be random and/or relatively extreme events unsuitable for any complex organization of macromolecules to assemble into the first living cell. It cannot be ruled out that some of the chemicals used in abiogenesis underwent various processes before their incorporation, where "extremes" may have played a role. But the assembly and origin almost certainly occurred in a thermally stable solution of substantial volume.Heating and cooling with wetting and drying must take place
Life arising in the oceans precludes any need for UV shielding.The most likely theories and experiments are done indoors. They do not even require protection from intense solar UV.
Proteins are widely believed to have been a secondary development due to an initial RNA-based life form. Self-assembly of proteins and polynucleotides in liquids is documented.The more successful ones (David Usher) have been done under heating/cooling, wetting/drying conditions. All needed for initial peptide or nucleotide bond formation.
The complexities involved are clearly not well established, and adding solid phases is just another element of complexity. That would hardly rule it out. Occam's razor is no where to be seen in this topic.Solid phases (clay minerals) only add to the many complexities.
The panspermia concept is as unlikely as the magic wand notion. The shear forces of impact and ejecta, to say nothing of the heat involved, renders it highly unlikely, as does surviving the hazards of space weather for millions of years in a near vacuum. And then you go through it again with the heat of entry, and the shear and heat of impact. And then you must land in an area which contains all of the minerals and nutrients required to survive and propagate. It makes adding solid surfaces appear rather simple by comparison. Besides all that, panspermia simply puts the origin and its complex chemistry somewhere else.Maybe the most likely answer (for the Earth) is Panspermia?
That is a statement quite impossible to accept. What is most likely believed is science by consensus, which usually is correct, at least in my experience. You sound like a contrarian, which some appreciate. All of the known laws of physics and major observations in science are based on consensus. How could science progress otherwise? It cannot.What is most likely believed is science by consensus and that has always been irrelevant.
Clearly UV cannot penetrate very far in water. You know this. So any developing chemistry on its way to life would be in water anyway, but would have to be deep enough to shield it from UV, or nothing will arise. Very simple. That is why most insist, as do I, that life arose in the oceans, at least deep enough to avoid UV. It is clearly the optimal solution. As noted, the oceans also provide nutrients and thermal stability for an aqueous-based abiogenesis."Life arising in the oceans precludes any need for UV shielding" A common misconception.
With a doctorate in biochemistry, I am well aware of the need for peptide bonds in proteins, and phosphodiester bonds (your "nucleotide bonds") in polynucleotides. However, it seems likely that there was no protein in the earliest life forms, with many accepting RNA genomes (i.e. RNA-coding) and RNA mechanistic-based life forms. We could go on for hours, but it will soon become circular. Getting pretty close already.There is no viable way around the need for peptide and nucleotide bonds to get cellular life underway,
Who is Richard Dickerson? He does not appear on this thread.Please re-read what Richard Dickerson wrote...posted yesterday.
This was an issue I neglected to mention in one of your last posts. It is quite revealing to your concepts of abiogenesis. LUCA is already a fully formed "central dogma life form". It cannot offer more on abiogenesis than any microbes living today, actually. We need to get from self-replicating polymers to replicating cells bound up in membranes. LUCA must have appeared long after the first life form arose. There is nothing there regarding a starting point, only relationships.And don't forget what the LUCA (Aquifex) is telling us.
While waiting for your reply to my request about the "dilemma", I had to revisit the notion of an "RNA World", to brush up on the concept. Wiki (1) defines it as:There is nothing there regarding a starting point, only relationships.
In order to accept LUCA as the first life form, you must reject the RNA world. You say that LUCA is accepted by consensus agreement, but this after you ran the notion through the ringer. Who was it? Oh yes, "blind faith the one unpardonable sin". Thomas Huxley.You are not correct that LUCA must have appeared after the first life.... It WAS the first life...a full biological organism by definition and by consensus. Aquifex a microaerophile in an anoxic world.
Using water as negative pressure for abiogenesis is rather strange, since it is the one, single component that drives all of the folding of proteins, the formation of membranes, the diffusion of nutrients and waste products, to name just a few of its many required activities. And the amounts of water which are present that are unrelated to metabolism are nearly infinitely higher. It would almost seem that William Martin believes life is a solid-state format.Through hydrolysis, water literally works against the synthesis and accumulation of polymers at life’s emergence." William Martin