Evolution of complex chemical mixtures reveals combinatorial compression and population synchronicity.

Many open questions about the origins of life are centred on the generation of complex chemical species. Past work has characterized specific chemical reactions that might lead to biological molecules. Here we establish an experimental model of chemical evolution to investigate general processes by which chemical systems continuously change. We used water as a chemical reactant, product and medium. We leveraged oscillating water activity at near-ambient temperatures to cause ratcheting of near-equilibrium reactions in mixtures of organic molecules containing carboxylic acids, amines, thiols and hydroxyl groups. Our system (1) undergoes continuous change with transitions to new chemical spaces while not converging throughout the experiment; (2) demonstrates combinatorial compression with stringent chemical selection; and (3) displays synchronicity of molecular populations. Our results suggest that chemical evolution and selection can be observed in organic mixtures and might ultimately be adapted to produce a broad array of molecules with novel structures and functions.