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

by Brian Greene

RNA is thus both software and hardware. It can direct as well as catalyze chemical reactions. And among such reactions are some that promote the replication of RNA itself. While the molecular machinery that makes copies of DNA uses an elaborate collection of chemical cogs and wheels, RNA itself can promote the synthesis of the base pairs necessary for its own replication. Consider the implication. Molecules of RNA, blending software and hardware, have the potential to sidestep the chicken and egg conundrum: How do you assemble molecular hardware without first having the molecular software, the instructions to carry out the assembling? How do you synthesize molecular software without first having the molecular hardware, the infrastructure to carry out the synthesizing? Embodying both functions, RNA melds chicken and egg, and thus has the capacity to propel an era of molecular Darwinism forward. Such is the RNA World proposal. It imagines that before there was life there was a world suffused with RNA molecules, which through molecular Darwinism evolved over an almost unfathomable number of generations into the chemical structures that constituted the first cells.