Unfortunately, however, clays can only favour an accumulation of pre-existing molecules, not the in situ develoment of two-dimensional organic systems, because their negative charges repel the negative charges of amino acids and nucleic acids. This is why Wächtershäuser proposed that surface metabolism developed on positively-charged minerals, and in particular on crystals of iron pyrite (FeS2).
Wächtershäuser’s theory suggests, furthermore, that the first two-dimensional organic systems could eventually detach themselves from their supporting surfaces, and gradually turn into three-dimensional vesicles. The end result is, again, the formation of primordial metabolic structures which are supposed to be potentially capable of evolving into primitive cells. But even in this case, we do not know if those structures were destined to abort or to go on evolving all the way up to the origin of cellular life.

“Postchemical” evolution

The first scientific theories on the origin of life were proposed independently by Alexander Oparin in 1924 and by J.B.S. Haldane in 1929. Oparin discovered that a solution of proteins can spontaneously produce microscopic aggregates – which he called coacervates – that are capable of a bland metabolism, and proposed that the first cells came into being by the evolution of primitive metabolic coacervates. Haldane, on the other hand, was highly impressed by the replication properties of viruses, and attributed the origin of life to the evolution of virus-like molecular replicators.
Today, Oparin’s coacervates are not as favoured as Fox’s microspheres or Wächtershäusers’s vesicles, and RNA replicators are preferred to Haldane’s viroids, but these differences have not changed the substance of the original opposition. Between the two fundamental functions of life – metabolism and replication – Oparin gave an evolutionary priority to metabolism, while Haldane gave it to replication, and the choice between these two alternatives is still the key point that today divides the origin-of-life theories in two contrasting camps.