Phase separation induced by active polymerization makes protocells robust against environmental changes

The origin of life remains a scientific mystery, particularly the emergence of protocells. One hypothesis proposes that protocells arose as droplets formed via liquid-liquid phase separation of polymers. The work on this hypothesis leaves open how protocells survived in fluctuating or cyclic environments. We consider a model system incorporating both spontaneous polymerization and droplet-facilitated fuel-driven polymerization. We show that the resulting droplets display a stationary hysteresis with respect to available fuel. Droplets can remain stable even after the fuel-driven polymerization reactions significantly diminish, suggesting a potential mechanism for protocell formation and resilience to environmental fluctuations. This robustness would have enabled protocells to endure early environmental challenges, such as energy shortages in a famine.