Since Miller’s experiment in 1953, showing that chemical reactions can be the origin of life on Earth, part of the research has focused on the discovery of possible synthesis pathways in the conditions of the primitive environment of our planet. Other scientists are more interested in understanding what life is. Robert Pascal, emeritus research director at the Physics of Ionic and Molecular Interactions laboratory (CNRS/Aix-Marseille Univ.), proposed a new minimalist theoretical model of living processes. In this system, based on simple autocatalytic cycles, an energy supply makes it possible to compensate for thermodynamic instability and to achieve kinetic stability thanks to the multiplication of the original activated molecule.
This scheme is based on a thermodynamically activated molecule which, as soon as energy is supplied to it, transforms into a second compound, which can eventually transform itself into a third compound. After one complete cycle, the cycle leads to two copies of the starting molecule, allowing it to continue. The system is then able to grow and reproduce. In the absence of energy, the degradation of activated species leads to by-products which do not allow a cycle to be reconstituted: the system “dies” definitively and cannot be restarted.
This theoretical scheme takes into account other parameters of life, such as natural selection. Several different systems can in fact compete for the same energy source, allowing the most efficient to win and letting the others waste away. We do not find the capacity for adaptation and variation of a genetic code, but such a system could have appeared before this principle.
The diagram thus reproduces the behavior of living beings, capable of emerging, growing, entering into competition with conspecifics and dying. This model also has the advantage of being able to engage from of a single copy of a very rare and very unstable chemical species, within a molecular jumble. The continuation of this work will notably consist of finding chemical compounds compatible with the primitive environment and capable of reproducing this theoretical pattern.
Editor: MK
