Can the origin of biosynthetic routes be explained by a Frankenstein's monster-like spontaneous assembly of prebiotic reactants?

Since it is easy to envision that prebiotically synthesized molecules underwent reactions comparable or even identical to those that occur in some metabolic pathways, it has been argued that biosynthetic routes emerged from the direct assembly of these prebiotic reactants. However, although in prebiotic simulation experiments several products present in extant metabolic routes may be formed at the same time, in biosynthetic pathways, the same precursor undergoes a stepwise transformation into other compounds, allowing changes of energy to occur that are necessary for the energetic independence of cells. In other words, from thermodynamic and equilibrium perspectives, the availability of many or all of the chemical components of a metabolic route does not necessarily imply that they will spontaneously be linked in linear or cyclic pathways. Although a number of chemical changes that mimic or are identical to a number of metabolic reactions may have taken place in the primitive environment, in the absence of a genetic apparatus ensuring the stability and diversification of the catalysts and hypothetical pathways, it is difficult to picture the continuity and evolution of such chains of reactions.This article is part of the theme issue 'Origins of life: the possible and the actual'.