The Origin of Life - Self Replication

The Origin of Life - Self Replicating Molecules

This chapter will attempt to quantify the amount of molecular knowledge needed for self replication (and thus the origin of life). Both proteins and RNA will be considered. While many researchers have theorized that one of these molecules emerged as the first self replicator, origin theories stand a much better chance if both are involved. While RNA can perform some of the functions normally performed by proteins, proteins are much more efficient. Amino acids have many functional groups available in their side chains, and these functional groups impart to proteins a versatility than RNA cannot possibly possess.

   To understand why a system comprised of both is better, consider how numbers and letters are used in the following two sentences.

The number is 4,900,555,015 dollars.

The number is four billion nine hundred million five hundred fifty five thousand and fifteen dollars.

   Often numbers communicate numerical concepts better than words. The first sentence is much easier to understand. Forcing RNA to do the job of a protein is clumsy. It is analogous to writing out a very large number using words to represent the numbers. Just because it is possible, does not mean that it is the easiest or best way to accomplish the task. RNA is good at storing information. Proteins are good at regulating chemical reactions. The first system of replicating molecules was probably a combination of both, and a good model for such a system is alive and well today in the simplest bacteria. Nevertheless, because chemical evolution does not explain the spontaneous emergence of bacteria from the primordial soup something simpler needs to be considered. The goal of this chapter is to show that something simpler does not work because simple systems cannot self replicate.
     

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