Origin of life: Why do we believe it is a fully natural event? - Denyse O'Leary

Hope readers enjoy these excerpts from my current series. You can go to the whole of each from the links, of course.  - Denyse 

 Note:The Science Fictions – cosmology series  is here.

  Is there a good reason to believe that life's origin must be a fully natural event?

The first clue about the adventure that we are in for is: Life is a state, an experience, that everyone has and thinks they can recognize in other people and things. A quality we think is very important. Yet no one can define it.

Darwin proposed a mechanism for the evolution of existing life -- natural selection acting on random mutation -- but, a prudent man, he stopped well short of proposing to account for life's origin. Some of his followers pressed ahead. They ask us to imagine "self-replicating entities," protocells, and "prebiotic life" (essentially, pre-life) that somehow evolved their way to life long ago. At New Scientist, Michael Marshall assures us,

Once the first self-replicating entities appeared, natural selection kicked in, favouring any offspring with variations that made them better at replicating themselves. Soon the first simple cells appeared. The rest is prehistory.

It must be prehistory. No such chains, protocells, or pre-life are found in a wild state today. And even the fabled "minimal cell" is more complex than expected. More.  

  Does nature just “naturally” produce life?

Essentially, law theorists assert that a chance origin of life is hopelessly improbable. Therefore, they assume, matter simply forms itself into life at some point, obedient to a law of its nature. The theorists do not at present have any idea what factors underlie such a law or how it has worked. Or why it is not working now, so far as we know (in the sense that new types of life are not self-assembling around us). They know that the law exists because life exists, chance is powerless to create it, and devotion to the philosophy of naturalism rules out design. More.

Apart from that, we know nothing at present.

   Can all the numbers for life’s origin just happen to fall into place? A chance origin of life offers a practical advantage:

Precisely because life is so complex, a great many ideas can be researched. And the field is still at the starting gate. When Harvard chemist George Whitesides received the coveted Priestley medal in 2007, he said, "Most chemists believe, as do I, that life emerged spontaneously from mixtures of molecules in the prebiotic Earth. How? I have no idea." He did know what he thought of the cell, however:

The cell is a bag -- a bag containing smaller bags and helpfully organizing spaghetti -- filled with a Jell-O of reacting chemicals and somehow able to replicate itself.

The secret is in that "helpfully organizing spaghetti."

Although chance-based proposals are far more numerous, they face the same key hurdles as law-based ones, including: More.

 Welcome to "RNA world," the five-star hotel of origin-of-life theories

When a cell divides, its DNA's operational instructions are copied by RNA (ribonucleic acid), which directs the proteins that build cell machinery. The current leading origin of life hypothesis, RNA world (or RNA first) offers a limited and researchable claim, first proposed in 1967 by Carl Woese, Leslie Orgel, and Francis Crick: that RNA preceded and stood in for DNA in ancient life. Because this route slightly reduces the awesome complexity, it was not only too good to be false, it was hailed by key researchers as "the molecular biologist's dream." By 1986, biochemist (and Nobelist) Walter Gilbert envisioned a whole RNA "world" and Leslie Orgel was almost certain it had existed.

Not everyone was or is "almost certain." Gustavo Caetano-Anollés is convinced of the opposite because "That world of nucleic acids could not have existed if not tethered to proteins." A. G. Cairns-Smith, admittedly a champion of a rival "clay origin" theory, labeled it "absurd to imagine," complaining that there are "14 major chemical/molecular hurdles" against more primitive nucleotides like RNA. New York University chemist Robert Shapiro (1935-2011) compared the theory's likelihood to "a gorilla composing, in English, a coherent recipe for the preparation of chili con carne" and pleaded for greater realism. Yes, RNA theorists admit, there are difficulties. More.

 Self-organization: Can we wring information from matter -- shake the bit out of the it?

Irritatingly, self-assembly does sometimes happen. But the way it happens is no help. In 2009, one type of "Lazarus" bacterium, accustomed to extreme conditions, astonished researchers (who referred to such processes as "miracles") by reconstituting itself within hours of its DNA being shattered by desiccation and radiation. The sample organisms proceeded to live normally. Clearly, the bacterium re-self-organizes, so to speak, guided by something that survives the destruction of its DNA.

But have we any reason to believe that this extra layer of interior guidance is an "inevitable physical process"? Far from it, the bacterium had to already exist in a specific form in order to self-reassemble. So it points to new levels of the specified complexity inherent in the life processes for whose origin we cannot account even without such a capacity. More.

(to be continued)