Cold-selective topological bias and the emergence of the first membranes.

The emergence of the first membranes requires more than the synthesis of amphiphiles; it requires a mechanism that stabilizes bilayer-forming geometries within chemically diverse prebiotic mixtures. We present a minimal thermodynamic model coupling amphiphile topology to self-assembly, incorporating packing, curvature, and steric contributions. Changes in temperature alter the balance between ordering and disorder within amphiphile aggregates, thereby modifying the relative stability of lamellar, micellar, and dispersed states. The model identifies a bounded temperature regime in which geometries compatible with ordered packing preferentially stabilize lamellar assemblies, while geometrically incompatible isomers partition into micellar or nonlamellar phases. In this framework, temperature acts as a physical filter on assembly stability, providing a pre-metabolic mechanism for membrane selection and suggesting that cooler environments may have offered favorable stability windows for early membrane persistence, and therefore may have been first in the origin of life in the Lipids First hypothesis.