Theoretical origin of life; logical criticism of studies (Introduction)

by David Turell @, Thursday, January 10, 2019, 00:07 (160 days ago) @ David Turell

All studies have to supply intelligent designs and intervention. Nothing works from scratch as it would have on early Earth:

"But one of the most famous candidate molecules, HCN (hydrogen cyanide), often considered a stepping stone to life, is not prebiotically plausible, Benner argues. Why? Because “current theory holds that Earth’s native atmosphere was more oxidizing than the Miller atmosphere.” [Miller-Urey lightning in a bottle]

"Thus, the prebiotic plausibility of HCN, the other molecules, and adenine long ago vanished as Earth-made species, even though literature too voluminous to cite here continues to assume otherwise.

"This creates a paradox. If one premises that life originated via an RNA-First prebiotic process that used adenine as a precursor and that adenine was formed from HCN from a Hadean terran atmosphere, then the premises that view HCN as an impossible product of our early atmosphere force the conclusion that life could not have originated on Earth. An unacceptable conclusion follows by the force of logic from seemingly acceptable premises.

"Organic chemists, if not all experimentalists in the field of prebiotic chemistry, are faced with a similar dilemma. We do our best to perform experiments that we believe re-enact possible steps of prebiotic evolution, but we know that we need to intervene manually to obtain meaningful results. Simply mixing chemicals and watching for a living system to appear from the broth seems unreasonable to me. This approach has never worked, and it is not expected to work, at least not if one is limited to the lifetime of a human, let alone the duration of a funding period or a Ph.D. thesis. So, what is a reasonable level of intervention by the experimentalist in prebiotic chemistry, and what are “plausible prebiotic conditions” in this context?

"Richert identifies numerous sources of intervention in the lab that would never happen in the real world: using pure chemicals from a supplier, breaking up a series of reactions that need to be sequential, using high concentrations of chemicals that would be implausible in nature, eliminating contaminants that would ruin the reaction, inserting enzymes to get steps to run faster, purifying the products of one reaction, then putting the products into another process with a drastic change in conditions for the next stage, and more.


" Can Richert rescue OOL from reckless use of human intervention? He agrees with Benner that it is not easy to gauge the plausibility of prebiotic scenarios. He gives several more examples of how the subjective judgment of the investigator can creep in. But “plausibility is important,” he says. “So, perhaps it is time to think about ways out of the ‘Hand of God’ dilemma.”


"A final word of caution. Life is a non-equilibrium phenomenon. It requires an energy source that drives its reactions. Assuming that simple heating/cooling cycles could have driven the formation of functional biomacromolecules that were then able to harness the energy emitted by the sun via photosynthesis, seems unrealistic to me. Achieving the level of specificity required to successfully operate a protocell with genetic apparatus, metabolism, and cell division under strongly denaturing conditions is not easy, certainly when it comes to enzyme-free replication relying on the intrinsic specificity of small molecule interactions. So, the periodic addition of a chemical condensing agent may be unavoidable to drive biochemical reactions that are endergonic, even in “minimal intervention” experiments. Without the chemical activation, equilibrium (death) sets in. So, some level of human intervention may always be required for complex, multistep processes. After all, what the dominant activation agent was before enzymes began to use ATP will remain an enigma to many of us for the foreseeable future."

Comment: These comments are from two prominent OOL researchers. They are Steven A. Benner and Clemens Richert. It is going nowhere. But grant money will continue in huge amounts.

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