WHY IS LIFE SO COMPLICATED?

It is now time to sum up what we may have learned from the first three chapters. Chapter 1 describes the historical development of ideas leading up to the question that I consider to be fundamental to all investigation of the origin of life: Is the origin of life the same thing as the origin of replication? I give some reasons why I am inclined to answer no to this question, to give a tentative preference to the hypothesis that metabolism and replication had separate origins. Chapter 2 gives a sketchy account of some of the classic experiments and some of the classic theories concerning the origin of life. I observe that the experiments since the time of Max Delbrück have been spectacularly successful in elucidating the structure and function of the apparatus of replication and much less successful in giving us a deep understanding of metabolism. Although the experiments of Cech and others (Cech, 1993; Wright and Joyce, 1997) on ribozymes have demonstrated that RNA can function as an enzyme, it acts as an enzyme only within a limited domain. An early review article (Cech and Bass, 1986) said, “It appears to be the limited versatility of RNA catalysts, rather than any deficit in catalytic efficiency or accuracy, that is responsible for the relatively restricted occurrence of RNA as a biological catalyst.”