Until the End of Time: Mind, Matter, and Our Search for Meaning in an Evolving Universe

by Brian Greene

Imagine, then, that as RNA molecules continued to replicate, a chance mutation facilitated something novel: the mutant RNA coaxed some of the amino acids in the environmental stew to hook up into chains yielding the first rudimentary proteins (a crude version of the kinds of processes that now take place in ribosomes). If, by chance, some of these basic proteins happened to increase the efficiency of RNA replication—after all, catalyzing reactions is, in part, what proteins do—they would be richly rewarded: the proteins would usher the mutant form of RNA to dominance, and the newly plentiful supply of mutant RNA would help synthesize more of the proteins. In tandem, they would constitute a self-reinforcing chemical loop that would propel the chance molecular aberrations to become the norm. Over time, the continued molecular machinations might hit upon another chemical novelty, a double-railed ladder—a rudimentary form of DNA—that proved to be a more stable and more efficient structure for molecular replication, and thus gradually usurped the replication processes and relegated RNA to a supporting role. The chance formation of molecular bags—cell walls—would increase fitness further by concentrating chemicals in sequestered regions and offering protection from environmental disruption. Spreading throughout the chemical population, the structures necessary for the first rudimentary cells would assemble.32 Life would be born.