In an overview article in The Scientist , Jef Akst profiles “RNA world” research today. RNA world, the conviction that very early life forms used RNA instead of DNA is the five-star hotel of origin-of-life theories.
One of the people he interviews is University College (London) biochemist Nick Lane, a proponent of the “metabolism first” idea; metabolism, he says, had to come first though he thinks RNA world is on the right track:
But the notion that RNA, on its own, spontaneously assembled and evolved on early Earth has fallen out of favor. More likely, whatever conditions spawned compounds as complex as nucleotides also generated other organics, perhaps early forms of modern amino acids and fatty acids, the constituent parts of proteins and membranes. “I’m not sure how many people anymore believe in a pure RNA world. I certainly don’t,” says Lane. “I think the field has drifted away from that, and there’s now an acknowledgment it had to be ‘dirty.’?”
His Portland State University colleague Niles Lehman describes early life as driven by a form of “molecular co-operation,” not competition.
These molecules would interact with each other, and though they would not have been self-replicating or able to evolve in a Darwinian fashion, one could imagine a different kind of selection driven by the kinetics of the chemical reactions, says Lehman. Under these conditions, he argues, the notion of early life being contingent on a selfish molecule may miss the mark. When it comes to mixtures of interacting molecules, the Darwinian concepts of individual fitness and discrete generations do not apply, he says. “As you approach the origin of life itself, you have to think outside the box a little bit to imagine these systems getting off the ground. . . . The rules of the game are significantly different in the first moments.”
Lehman and others suggest a sort of molecular cooperation as a key factor in the origin of life. Polymers that assembled with other polymers might have been better protected against hydrolysis, for example, and as a result, started growing in number. Over time, these chemical systems could have “evolved” to be more stable and more complex. As more species of molecules joined the interactions, they may have created chemical networks that began to take on functions. “Imagine that, of [a] set of molecules, there might be some that catalyze a chemical reaction that gives rise to a molecule that’s needed—something that’s in short supply, for example,” says Hud. “That would then allow the polymers that are around this ‘generator’ to increase in number. And so there’s a functional sequence.”
This level of co-operation sounds like a form of self-organization. Would it be fair to say that self-organization theory is gaining ground on RNA world?
The big question in origin of life is really “Can we wring information from matter — shake the bit out of the it?” Or is it the other way around, as the great physicists would have it: The bit creates the it.
But can that happen without an existing intelligence? Here’s an illustration:
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.
See also: Is there a good reason to believe that life’s origin must be a fully natural event?
Does nature just “naturally” produce life?
Can all the numbers for life’s origin just happen to fall into place?
Welcome to “RNA world,” the five-star hotel of origin-of-life theories
Self-organization: Can we wring information from matter — shake the bit out of the it?
The Science Fictions series at your fingertips (origin of life)
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