Abstract

RNAs can do many things. They can store information, act in the world, and respond to the world. Because of these capabilities biologists have proposed a primordial ‘RNA world’ in which RNA, rather than DNA, performed the central role of replicator and repository of adaptive information. Deacon dismisses this hypothesis because replication is not about anything and because the structure of replicating molecules cannot contain information about the environment. I dispute both claims. An RNA and its opposite-sense complement represent each other and, by two rounds of complementation, represent themselves. Although nucleic acid sequences do not change in response to their present environment, these sequences embody information about ancestral environments via the selective filtering of alternative sequences in those environments. Nucleic acid sequences are the textual record of what has worked in the past.