Re your specific points:
- You say “They might be the oldest and simplest but their complexity is how they are now, not Gazillions of years ago.” Exactly. That’s why I proposed a less complex predecessor. Current thinking is that birds evolved from certain dinosaurs, and it is plausible that over “Gazillions of years” birds resulted from that evolution. However, a bird is not a dinosaur, a Bengal tiger is not a Saber tooth tiger, and an Archaeal microbe is not its hypothetical ancestor.
- Archaea come in many forms, some which can tolerate high temperatures (Thermophiles), and at the other extreme some can tolerate temperatures as cold as -20°C (Psychrophiles). The first Thermophiles were found around deep-sea hydrothermal vents, with a remarkable biochemistry based on chemosynthesis; these microbes are the base of support for complex ecosystems. The Archaea contain thousands of genera, with vastly different properties; for example, from the linked article below: “...animals at hydrothermal vents have special biochemical adaptations that protect them from hydrogen sulfide.”. Here is a good article about the Thermophiles.
https://ocean.si.edu/ecosystems/deep-s ... ts-pumping
- While most casual discussions of microbes seem to center around their biochemistry, the research literature I’ve read to date has mostly focused on the cell cycle, because that’s where the complexity is revealed and many questions remain. The link below provides details of the cell cycle of Sulfolobus acidocaldariu, the most widely explored archaeon. Here is just one of many examples of how involved and finely orchestrated s. acidocaldari’s cell cycle is: “Several DNA repair genes displayed cyclic induction…”
https://www.pnas.org/doi/full/10.1073/pnas.0611333104
- The presence of dedicated structures to synthesize proteins (ribosome) or move the organism (archaellum) ,
- The vast number of genera displaying widely varying chemistries,
- The existence of “special biochemical adaptations” in Thermophiles.
- The presence of biochemical messengers to inhibit fission,
- The activity of DNA repair genes,
- The variety of different biochemicals used for the same purpose in different archaeons’ cell cycle steps, and
- The orchestrated steps of the cell cycle that have fall-backs in case a key substance is missing
To repeat, in my opinion it is beyond reasonable that something so complex and dependent on such organized behavior could be the result of a happy accident. Or to put it another way, it is beyond reasonable that the very first cell to exhibit life, i.e., replicate itself, was a fully formed archaeon with all of the structures, DNA, and fault-tolerant cell cycles that the domain exhibits. YMMV.
Thanks again for the reference to Franklin Harrold’s work. That will be the next thing I look at.