3. The Evolution of Cells

3.5 Evolution is not Chance but Necessity

On celestial bodies endowed with water as the principal solvent, one would expect the evolution of Life to have proceeded – under appropriate conditions – in a way similar to that on earth. The origin of life and the evolution of increasingly highly organized systems is not chance, as asserted by Monod16 but a response to necessity, as first defended by Kuhn17.

During divergent phases of evolution, many forms appear that have similar chances of survival. As a result, the population acquires a great diversity. As a gradual improvement of the mechanism of transfer of information occurs, such a mechanism begins to serve an entirely different purpose, new and not foreseen. This turning point initiates a convergent phase during which immediate selective advantages favor those mutants that serve the next purpose best. George C. Williams developed this notion in: “Adaptation and Natural Selection, Princeton University Press, 1966”. Williams pointed out that evolution of a trait must confer an immediate selective advantage on an individual rather than yield long-turn benefit for the group or species as a whole. The process that leads to this turning point is in itself highly improbable but has to occur sooner or later by constraint if the population is of sufficient size. The smaller the size of the population, the longer the time needed, with some opportunities missed, not to be retrieved.

An event that will suddenly rise to one evolutive level a system captive at another level is not chance. Under appropriate conditions, the origin of life and its evolution is a necessity. On earth, the overabundance of energy provided by the sun renders the thermodynamic laws of doom inapplicable. If given the same conditions, the inevitable steps leading to higher levels of transmission of information would occur again. These steps are replication, formation of aggregates, formation of an envelope, evolution of the genetic code, storage of information into a stable entity, exchange of genetic material between individuals. What is chance is the solution adopted at the moment the event occurred. The details can and will differ, as the structure of ribosomes, the storage of information, the configuration of enzymes, etc. However, the general purpose would still be equally well served.


16. Monod: Le hasard et la nécessité, ed. Seuil, Paris, 1970

17. Kuhn: Ang. Chem. Intern. Edit. 11: 798-820, 1972

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