According to Abiogenesis, it is assumed that the first life form was a simple cellular organism, which can evolve by itself during the prebiotic era, and then as time goes by, this simple cell starts to get more functions, being more complex, and forming more complex life forms.
As we are discussing the origin of life, we should be more concerned about that assumed simple cell: how simple the cell could be? And what is the minimum abstraction that can be assumed for a cell to be alive? That is, what are the minimum required biological components to have a living organism?
As described by Dr. Nita Sahai about The Origins of life (reference 1), the minimum basic components of Extant Life are:
- Heritable, Mutable Genes (i.e. DNA)
- Metabolic Cycles (i.e. Proteins and enzymes)
- Boundary Membrane (i.e. lipids)
However, the relationships between DNA, proteins, enzymes, and the cell’s membrane present a biological conundrum.
Here we face multiple Chicken or Egg problems.
- which came first: replication or metabolism? DNA or DNA polymerase Enzyme?
- DNA/RNA coded information, or Cell Machinery that is capable of reading this information to perform all cell functions?
- Enzymes are necessary for the timely formation of proteins, but these enzymes are built, in part, with proteins.
- Proteins are required to create Ribosome Machines, but Ribosome Machines are required to create Proteins.
The idea of having all of these components at once, at the same time, in the same place, joining together perfectly the first time, is extremely, EXTREMELY improbable. In addition to that, still multiple other issues are yet to be explained like:
- The prebiotic chemical formation for the lipids, carbohydrates, proteins and Amino acids by natural processes (like chance, time and necessity)
- The information, the instructions or the software encoding within DNA/RNA
Irreducible complex system
That leads us to a concept proposed by famous biochemist Dr. Michael Behe called “irreducible complexity”, which refers to a system that has a number of components, which interact with each other, to produce a function, that the components can’t do by themselves, and if you take one or more components away, the system doesn’t work, so it is irreducible.
That concept can be applied to very simple cells, to larger Eukaryotes (organisms with cells with nucleus enclosed), organs, and entire organisms. This idea can be applied to machinery and equipment as well, as most devices are built from components, and there are core components that can’t be eliminated or otherwise the device will not function. Sometimes the overall idea is used to counter argue Darwinian evolution, but we are focusing here on the origin of life, showing how the biology of primitive cells exhibit irreducible complexity.
The simplest forms of life are single-cell bacteria. Viruses are simpler than the simplest known cell and they lack the structures required to be alive as they reproduce only when their genes take over the host cell’s reproduction machinery. Nonetheless, even viruses require a minimum number of parts to function.
It’s also getting clear that the living cell contains a lot of nano machinery, and using the term “machines” induces automatically:
- The composition of parts (in which some are irreducibly complex)
- Purposely functioning
- Maintenance and correction and, accordingly,
Scientists have no proposal yet as to what the simplest cell should look like, or how the least required components come together to start that assumed cell.
The living cell looks like it was designed, functions to achieve a certain purpose as if designed, and contains parts working together in harmony as if designed. That’s because it really is designed.
Some further examples:
- Bacteria Flagellum (reference 3)
- Microtubules (reference 4)
- DNA copying machines (reference 5)
That term “machines” has been widely used in a lot of articles with titles like:
- The cell as a collection of protein Machines: preparing the Next Generation of Molecular Biologists, Bruce Alberts
- Polymerases and the Replisome: Machines within Machines, Tania A Baker and Stephen P Bell
- Eukaryotic Transcription: An Interlaces Network of Transcription Factors and Chromatin-Modifying Machines, James T Kagonaga
- Mechanical Devices of Spliceosome: Motors, Clocks, Springs, and Things, Jonathan P Staley and Christine Guthrie
- Molecular Movement inside the Translational Engine, Kevin S Wilson and Harry F Noller
- The Hsp70 and Hsp60 Chaperone Machines, Bernd Bukau and Arthur L Horwitch