It Takes Two to Tango Information, Metabolism, and the Origins of Life

man's logical analysis led him to claim that life is not Metabolism, and the Origins of Life one thing but two, metabolism and replication. Wills and Bada agree that this duality has fueled many of the most ferocious debates regarding the origins of A Historical and Scientific Overview By Iris Fry life, and has led otherwise broad-minded people to retreat into opposing camps: New Brunswick, NJ: Rutgers University Press (2000). 327 pp. $55.00 Thinkers about the origin of life have wrestled, with varying degrees of success, with the question of how The Spark of Life: Darwin the first organisms could have acquired [the minimal and the Primeval Soup essential properties that distinguish a living system By Christopher Wills and Jeffrey Bada from inanimate nature]. These thinkers can be roughly Cambridge, MA: Perseus Publishing divided into those who believe that genes came first (2000). 291 pp. $27.00 and those who believe that life must have started with metabolism. (Wills and Bada, p. xviii) It might be thought that the discovery of the universal mechanisms basic to the essential properties of living Evidently, the chicken and the egg need an update. beings would have helped solve the problem of life's In the dark ages before 1981, when proteins were the origins. As it turns out, these discoveries, by almost only known catalysts, we asked a simple but unanswer-entirely transforming the question, have shown it to be able question: Which came first—proteins or nucleic even more difficult than it formerly appeared. acids? With the discovery of catalytic RNA, and the —Jacques Monod, Chance and Necessity, 1974 realization that RNA could serve both as replicase and as genome, the original question was replaced by a new For hundreds of years the origin of life was thought to and equally perplexing one: How did the first functionally be well understood and did not pose any problem to complex RNAs arise? The Urey/Miller experiment in naturalists and lay persons alike. Interestingly, doubts 1953 provided a stunning proof-of-principle that simu-began to rise with the growth of biological knowledge, lated prebiotic chemistry could generate biologically in-and the question became a complete mystery, espe-teresting molecules, but progress since then has been cially at the end of the nineteenth and the beginning of disappointing, and plausible prebiotic pathways have the twentieth century. (Fry, p. 1) not been identified for the synthesis of nucleic acids, let alone the lipids that are …