Hydrothermal vents are widely considered plausible settings for the origin of life, owing to their steep redox gradients and the availability of chemical energy. However, their physicochemical properties—high temperatures, rapid thermal fluctuations, and dynamic fluid flow—may be less conducive to the persistence of fragile molecular assemblies than is often assumed. Here, I suggest that hydrothermal systems may be more consistent with the early emergence of decomposer-like metabolisms than with the initial formation of life itself. In contrast, ice–water interfaces provide conditions that favor molecular accumulation and persistence, including freeze–thaw cycling, solute concentration, and reduced diffusion, potentially enabling the gradual development of prebiotic reaction networks. From this perspective, early metabolic roles may have emerged sequentially across distinct environmental structures: producer-like systems at ice–water interfaces, consumer-like processes in surrounding aqueous environments, and decomposer-like metabolisms in hydrothermal settings. This structural ecology framework offers a way to reconcile the apparent tension between molecular fragility and the energetic richness of hydrothermal environments. It suggests that the last universal common ancestor may be better understood as a point of convergence among metabolically differentiated lineages rather than a singular point of origin.