Mixtures of single-chain amphiphiles (e.g., fatty acids, alcohols, and aldehydes) form membrane-bound compartments under prebiotically plausible conditions. However, their sensitivity to metal ions restricts their ability to host Mg 2+ -driven RNA polymerisation and Fe-driven protometabolic processes, and suggests that complex phospholipids were likely needed for the emergence of robust primitive cells. Notably, phospholipids enhance the stability of fatty acid-based membranes to pH and divalent cations, but such blended membranes do not host the compositional diversity of phospholipids nor mirror the functional capabilities exhibited by modern membranes.