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How life emerged is one of the major questions that remains to be answered. Apart from being of interest for completeness of biology, it is also a very interesting study case from the vantage point of physics. Living organisms are inherently non-equilibrium systems. Since non-equilibrium thermodynamics is still a developing field, the emergence of life is a highly interesting study case. Here we present the progress we have made during the last few years, employing experimental biophysics to capture the mechanisms that could eventually lead to the emergence of life. We show how a simple non-equilibrium system, a thermal gradient, gives rise to a range of relevant phenomena, in particular, polymerization, elongation, and replication of DNA molecules as well as demixing of mixed DNA sequences into sequence-pure hydrogels. 1 Introduction 2 Thermophoresis, the Biased Movement of Molecules in Thermal Gradients 3 The Dynamical Behavior of Accumulated Molecules 4 Overcoming Spiegelman’s Monster 5 Sequence Purification and Oscillations by a Gel-Phase Transition in Thermal Gradients 6 Loose Ends 7 Discussion and Conclusion [ABSTRACT FROM AUTHOR]

The key requirement to solve the origin of life puzzle are disequilibrium conditions. Early molecular evolution cannot be explained by initial high concentrations of energetic chemicals since they would just react towards their chemical equilibrium allowing no further development. We argue here that persistent disequilibria are needed to increase complexity during molecular evolution. We propose thermal gradients as the disequilibrium setting which drove Darwinian molecular evolution. On the one hand the thermal gradient gives rise to laminar thermal convection flow with highly regular temperature oscillations that allow melting and replication of DNA. On the other hand molecules move along the thermal gradient, a mechanism termed Soret effect or thermophoresis. Inside a long chamber a combination of the convection flow and thermophoresis leads to a very efficient accumulation of molecules. Short DNA is concentrated thousand-fold, whereas longer DNA is exponentially better accumulated. We demonstrated both scenarios in the same micrometer-sized setting. Forthcoming experiments will reveal how replication and accumulation of DNA in a system, driven only by a thermal gradient, could create a Darwinian process of replication and selection. [ABSTRACT FROM AUTHOR]