Soru

Passage A
For decades, the "RNA World" hypothesis has reigned as the premier explanation for the transition from prebiotic chemistry to biology. The core conundrum of abiogenesis—whether genetic replication or enzymatic catalysis came first—was elegantly bypassed in the 1980s by the discovery of ribozymes. These RNA molecules, capable of catalyzing chemical reactions including their own replication, demonstrated that a single molecular species could perform the dual roles of genetic database and functional enzyme. In the envisioned RNA world, primitive life began not as structured cells, but as self-sustaining pools of RNA molecules. Under prebiotic conditions, the primordial environment facilitated the spontaneous assembly of activated nucleotides into short polymers. Over generations, selective pressures favored those sequences that replicated with greater efficiency and accuracy. Proponents point to the modern ribosome, the cell’s protein-manufacturing machine, as a molecular fossil of this ancient era; its catalytic core is composed entirely of RNA, suggesting that proteins were later evolutionary innovations co-opted by a pre-existing RNA-dominated system. The primary appeal of this hypothesis lies in its conceptual parsimony: a single molecule solves both the replication and catalytic hurdles, providing a clear, linear path to the first true cells. This model suggests that genetic information and evolutionary selection are the true starting points of life, with metabolic complexity emerging only after a reliable system of inheritance was firmly established. In laboratory settings, researchers have successfully evolved ribozymes that can catalyze various chemical transformations, lending empirical weight to the idea that RNA could manage a primitive organism's physiology. Though these synthetic ribozymes are far simpler than modern proteins, they demonstrate a versatile catalytic capacity. Proponents argue that in the vastness of the early oceans, given millions of years, prebiotic chemistry would inevitably produce a self-replicating RNA molecule. Once self-replication began, Darwinian natural selection would take over, driving the evolution of more complex catalytic functions.

Passage B
While the RNA World hypothesis possesses undeniable elegance, it is increasingly criticized for its chemical implausibility under realistic prebiotic conditions. Critics argue that RNA is far too complex and chemically unstable to have accumulated in sufficient quantities on a barren, early Earth. The spontaneous synthesis of nucleotides—requiring the precise linkage of a ribose sugar, a phosphate group, and a nitrogenous base—is notoriously difficult to replicate in plausible prebiotic simulations without highly specialized, artificial laboratory interventions. Furthermore, RNA’s extreme susceptibility to hydrolysis in water poses a terminal threat to its persistence over evolutionary timescales. How could a delicate polymer survive and replicate in a chaotic primordial ocean?

Alternatively, the "metabolism-first" model suggests that life arose not from a single self-replicating molecule, but from ordered networks of chemical reactions. Proponents of this view, such as those advocating the iron-sulfur world hypothesis, argue that mineral surfaces in deep-sea hydrothermal vents catalyzed the first cyclic metabolic pathways. These primitive cycles generated energy and organic molecules from simple inorganic precursors like carbon dioxide and hydrogen sulfide. In this scenario, genetic molecules like RNA were not the originators of life, but rather sophisticated late-stage products, synthesized and stabilized by an already functioning, energy-harnessing metabolic system. Without a steady, localized supply of energy and raw materials provided by an established metabolic network, the complex polymerization of RNA would have been thermodynamically impossible. Life, in this view, is fundamentally defined by thermodynamic self-organization and energy flow, with genetic replication acting as a structural refinement added later to stabilize and record the system's operations. Furthermore, the probability of assembling a functional, self-replicating RNA molecule from a random sequence of nucleotides is astronomically low. A metabolism-first approach resolves this statistical bottleneck by proposing that chemical evolution proceeded through pathways of increasing thermodynamic efficiency rather than random molecular collisions. By utilizing geothermal energy, these mineral-bound reaction networks could grow in complexity over time. The emergence of RNA was not an accidental chemical fluke, but a deterministic consequence of a highly organized, prebiotic metabolic engine.

Which of the following assertions best represents how the author of Passage B would challenge the claim in Passage A that the prebiotic environment could facilitate the spontaneous polymerization of nucleotides?