​What are Chemical Systems?

Chemical systems are defined here as chemical mixtures comprising a network or set of interacting molecules. That is, system-dependent behavior and the system processes cannot be ascribed to any of the components acting in isolation.

Using this rather inclusive definition, a chemical system can be composed, in its simplest manifestation, of very few molecules also incorporating elements of their geochemical environment. At first glance, this definition seems too broad in terms of system composition. But the important aspect of the definition should in all cases remain the emergent properties, namely interconnectedness of the system and how the system behaves, rather than the contingent chemical composition of the system processes.​

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​What is Chemical Contiguity?

The Oxford English Dictionary defines contiguity as “the condition of touching or being in contact whether physical or non-physical”. In the chemical context employed here contiguity is seen as a connected gradient of physico-chemical conditions through which the different components of a chemical system (or “set” as above) can be synthesized and achieve their connectivity.​

​Relevance of the chemical systems and Contiguity

During the last fifty years, research on the emergence of life has focused mainly on exploring mechanisms for obtaining biochemicals and related functions under prebiotically plausible conditions. These chemicals were then considered indispensable for the emergence and evolution of cellular life and were extensively studied using simple chemical reactions or selection schemes to evolve them and enable novel functions.

It is certain that some examples used as illustrations in this article are too artificial to have played any role in the actual evolution on the early Earth or are even altogether wrong. However, they underscore the potential of the chemical system approach to facilitate the study of the emergence of life and also document the work at hand

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