So now we know how to get nucleotides, problem solved, right? Well, not quite. The issue with nucleotides is that they themselves are composed of different subunits: there is a sugar joined to a phosphate group at one end and a base at the other end. The bases are able to form from the hydrogen cyanide, but for quite a long time scientists did not have any success in getting the base to combine with the sugar. Proponents of the “RNA world" hypothesis were worried that they would have to abandon their model. Along came chemist John Sutherland, however, who showed that under the right conditions, the sugar and the base could actually be created together, instead of having to be combined individually.
What about linking the monomers together into a long chain? The primitive RNA could probably copy itself in chunks, rather than by being strung together one individual monomer at a time, like today; research that demonstrates this is being done by biochemist Andy Ellington. But whatever the details of the copying method, how on earth did the molecule start copying itself in the first place? Chemistry professor James Ferris has an hypothesis; on the surface of a particular type of clay, called montmorillonite, RNA nucleotides will actually come together to form chains. Jack Szostak has further found that from a random group of these linked nucleotides, some will eventually possess catalytic properties.
But the basis of life isn’t a “naked" molecule of nucleic acid; the basis of life is a cell. How did the cell originate? According to scientists, once there were amino acids on the primitive Earth (remember the Miller-Urey experiment), this would not have been so difficult. Amino acids in solution actually form proteinoids, molecules that are similar to modern proteins, when they are exposed to cycles of heating and concentration and subsequent re-hydration, such as would have happened to shallow pools left behind by receding ocean tides. These proteinoids, when re-hydrated, form structures called microspheres, which look superficially like membrane-enclosed cells.
The idea of the "primordial ribozyme" and the "proteinoid proto-cell" have been criticized by some scientists, though, as we'll see in the next article. These critics have put forth other models, one of the most complete being one that places basic biochemical processes as the first true "spark of life."