Could Thermal Gradients Drive Molecular Evolution?

Disequilibrium conditions are central for understanding the origin of life. Taking energetic chemicals at high concentrations to synthesize more complex molecules will not be enough to emulate and understand early molecular evolution. To comprehend the dynamic development of a molecular Darwinian system, the knowledge of energy flows according to the second law of thermodynamics is crucial. We review experiments which explore thermal gradients to trigger Darwinian evolution. On the one hand, laminar thermal convection leads to highly regular temperature oscillations that allow the melting and replication of DNA. In the same setting, molecules move along the thermal gradient, a mechanism termed thermophoresis or Soret effect. If thermophoresis is perpendicular to the convection flow and inside a long chamber, accumulation becomes very efficient and accumulates even short DNA thousand-fold. We showed that replication and accumulation can be implemented in the same micrometer-sized setting. Future experiments will show how replication and accumulation of DNA could give rise to a Darwin process of replication and selection, solely driven by a thermal gradient.