“In the early history of our planet, when enormous amounts of organic molecules were being produced by sunlight in a hydrogen-rich atmosphere, very simple, nonparasitic organisms had a fighting chance. The first living things may have been something like free-living viroids, only a few hundred nucleotides long. Experimental work on making such creatures from scratch may begin by the end of the century. There is still much to be understood about the origin of life, including the origin of the genetic code. But we have been performing such experiments for only some thirty years. Nature has had a four-billion-year head start. All in all, we have not done badly.”

Annotation

Sagan had just finished describing the Miller-Urey experiments: mix the gases of the early Earth, add a spark, wait ten minutes, and you get "an extremely rich collection of complex organic molecules, including the constituent parts of proteins and nucleic acids." A brown tar full of the building blocks of life, conjured from nothing. Amino acids had been assembled into protein-like molecules. Nucleotides had formed short chains capable of self-replication under certain conditions. The notes of the music of life, as he put it, but not the music itself. Sagan looked at these results, looked at how simple the simplest known organisms were (viroids, fewer than 10,000 atoms) and concluded the gap was closable within twenty years. He was reasoning from a real trajectory: the genetic code had been cracked only fifteen years earlier, recombinant DNA was brand new, and molecular biology was solving problems at a pace that made the remaining distance look short.

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