It depicts one multi-stage scenario of chemical origins of first life - from soup to RNA - stopping short of the information issues once RNA/DNA are first formed.
It even has a generalized "chemical formula" for "proto-life" creation from ocean & hot spring chemicals.
I think it is worth exploring because we will not get hung up in the information content issues and deal with how far you can get with chemicals.
Each step in the first Life scenario is supported by known chemical reactions, although the plausibility of conditions for some steps is debatable.
NOTE: I am only briefly recapping the article - it is more technical and fills in detain what I have briefly summarized here.
The interesting advances in this suggested scenario are:
1. COOLER VENTS: Mid-ocean hot vents that are cooler than the previously considered black smokers.
Why useful? There is less likelihood of organic chemical breakdown in the cooler vents.
2. MINERAL MEMBRANE BUBBLES: Inorganic semi-permeable "membranes" from hollow mineral bubbles at vent sites.
Why useful? They are depicted here as a necessary precursor for isolating products of chemical reactions that otherwise would break down - like an inorganic cellular membrane
3. MEMBRANE REPLACEMENT: As the bubble-protected "proto life" reactions build, the bubble is eventually filled with material that can make a real organic membrane (here I use the term organic in a strict chemical sense, as carbon based, not really implying an organic life form - we are still at a purely chemical stage)
The articles states that
(p34, bottom right) Laboratory experiments have demonstrated such iron-sulphide membranes to be semi-permeable. Any larger "sticky" organic products (amino, fatty and nucleic acids, sugars) were trapped in the bubbles and pores, but small unreactive organic molecules (acetic acid, methane) escaped.
and
Amino acid polymers not only had the propensity to co-opt catalysts from their surroundings, but in bulk, they could also have lined the inorganic bubbles that enclosed them.
4. SPECIFIC CATALYSTS: The energy for each these reactions is stepped up through catalysts.
For example, Russell suggests that greigite [Fe5 Ni S8], a nickel sulphide that co-precipitated in the membrane experiments in Russells's lab.
5. RNA AS A CHEMICAL PRODUCT ALONE: a) Russell suggest that the basics for RNA (phosphate from hydrothermal vents, sugar ribose and adenine from "primitive materials". When linked together "adenine, ribose and phosphate are known as adenosine monophosphate, one of the building blocks of RNA"
5
Citing Mellerish, Russell suggests that "a bound chain or RNA would have gripped amino acids and effected the formation of peptide bonds"Citing models developed by Copley & Morowitz, Russell then suggests that RNA captured on a mineral is a template to generate amino acids without transfer RNA.
6. FROM ACETATE GENERATION TO 2 FORMS OF PROTOLIFE
a) I will just quote the article here:
As productive as acetate generation must have been for the first organisms, some other means of combining CO2 and H2 - to synthesize methane for example, are even more advantageous in term of energy release
4H2 + CO2 - - > CH4 + 2H2O
But achieving this reaction is not so easy: Substantial barriers exist, although they can be side-stepped by catalysis and jumped with a bit more thermal energy.
William Martin and I posit that the organisms that achieved this feat, the proto-methanogens, marked the first and most significant fork in the evolutionary tree. In our view, these two different carbon dioxide assimilators, the proto-acetogens and the proto-methanogens quickly specialized and fledged, evolving over time into bacteria and archaea (primitive microbes that are neither bacteria nor eukaryotes). But how did they escape the hydrothermal hatchery?
7. EARTH's MOTION MOVES IT FROM VENT TO IDEAL LOCATION:
Convection of the earth's mantle, and a tendency for chemical proto-life "cells" to gravitate downward (where surface-based harm would not destroy the "cell"), after a thrust up from a tectonic junction, releases the "colonies of bacteria" and places some at an ideal depth for further life to form.
8. PHOTOSYNTHESIS More good stuff here - read the article.
I won't repeat the article here, and it is not yet on their web site, so a library or a magazine stand is the next best thing.
The article goes on to suggest with some specificity and laboratory backing, that:
- Short pieces of RNA (such as might be form on a mineralized iron sulphide surface) can act as templates for the formation of peptides.
- primitive photosynthesis
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That ends my review. I will make my views known in an opinion piece later in the thread.
This article is about chemistry.
I beg you ... Please do not distract from chemistry to information theory in this thread. I am well aware of the endless "abiogenesis" threads that get stalled in assumptions about the information content issues.
