Membranes as a Protective Barrier Between Worlds From the Anoxic–Oxic Transition to Contemporary Environmental Instability

This conceptual essay explores the role of biological membranes as physical barriers that mediate transitions between incompatible environmental states, from the anoxic–oxic transition in early Earth history to the rapidly changing conditions of the modern environment. During the rise of atmospheric oxygen, membranes did not provide absolute separation but acted as state-dependent filters that regulated the rate and extent of oxygen penetration, thereby allowing time for biological adaptation. A parallel situation exists today, where cellular membranes are exposed to unprecedented combinations of chemical, physical, and systemic perturbations occurring on timescales far shorter than those of evolutionary adaptation. Rather than causing immediate failure, these pressures may destabilize membrane states and push biological systems toward critical thresholds, contributing to chronic disease and pathological transformations. The essay proposes that understanding and stabilizing membrane physical states, rather than focusing exclusively on molecular defects, may represent a necessary new starting point for medicine. In this context, modern analytical approaches and artificial intelligence are discussed as tools for identifying state instability and mapping the boundaries of biological resilience.