Molecular Beginnings

In the days when life was brewing in the tidepools, lightning darting through the ammonia atmosphere catalyzed amino acids that concentrated in the pools. The amino acids joined into chains, and there were many self-replicators operating in the soup. There were cycles of replication catalyzed by other intersecting cycles. The problem was that although the teeming ferment diversified itself into countless iterations of molecular tinkertoys, these progressions of automata were not really going anywhere except to make a mat of scum on the surface of a tidepool, or a special variety of clay in which a slime of pre-life helped silicates self-adhere. It wasn't until the sealing off of cycles within this mat that DNA became the one and only privileged replicator: then the sequences of amino acid chains were tied back to DNA, so the soup had a direction for embodiment. It couldn't happen until one set of replicators became the node for interactions of all other cycles. Some RNA segments that work in our cells today were once independent replicators, but they got integrated into DNA's web. Some other very far-flung replicator regimes were squeezed out of existence along the way before DNA could become the one and only universal molecular ancestor (which itself was squeezed through a fairly narrow bottleneck, as evidenced by the many homologous segments between humans and even our most distant vegetative relatives.) It was really the closing off of the DNA regime that opened the permutational space to allow variations and try out all possibilities, thus bringing about the panoply of life on earth.