In addition to molecular syntheses there also were, of course, degradation processes going on, and it has been shown that the combination of these opposite reactions was bound to produce a stationary state where the oceans had the consistency of a slightly diluted broth. The so-called primitive soup, therefore, is not a fancy but a chemical necessity.
Together with the positive results, however, we must also consider the negatives ones, and of these one of the most important is the fact that the abiotic synthesis of molecules has been relatively easy for amino acids, but much more difficult for nucleotides. Another complication is the fact that left-handed and right-handed molecules are produced in vitro with the same frequency, and this is a serious obstacle, because most biological reactions require only one type of symmetry. As we can see, the formation of a primitive soup was an important step, but was only a first step, and does not take us very far. In order to go further, we clearly need to discover something else.

Chemical evolution

In order to join two amino acids with a peptide bond, a water molecule has to be removed, and this suggests immediately that the reaction should not easily take place in water. The energy balance does conferm, in fact, that amino acid polymerization is not favoured in water, and we cannot expect therefore that the primitive both could spontaneously produce a stable popolation of proteins. How then did these molecules appear?
A solution to this problem was proposed in the 1960s by Sidney Fox, on the basis of experimental results that he obtained by heating up a mixture of amino acids in the absence of water. Fox found that, in these conditions, amino acids do aggregate into macromolecules which can even reach large dimensions, and which he called proteinoids.
These are not real proteins because their amino acids are not arranged in linear chains of polypeptides, but form directly a variety of three-dimensional chemical bonds. Proteinoids, however, are somewhat similar to proteins in various respects, including a bland catalytic activity (they can, for example, catalyze ATP hydrolysis).