Rationality: From AI to Zombies

by Eliezer Yudkowsky

Here’s an example: DNA stores information very nicely, in a durable format that allows for exact duplication. A ribosome turns that stored information into a sequence of amino acids, a protein, which folds up into a variety of chemically active shapes. The combined system, DNA and ribosome, can build all sorts of protein machinery. But what good is DNA, without a ribosome that turns DNA information into proteins? What good is a ribosome, without DNA to tell it which proteins to make? Organisms don’t always leave fossils, and evolutionary biology can’t always figure out the incremental pathway. But in this case we do know how it happened. RNA shares with DNA the property of being able to carry information and replicate itself, although RNA is less durable and copies less accurately. And RNA also shares the ability of proteins to fold up into chemically active shapes, though it’s not as versatile as the amino acid chains of proteins. Almost certainly, RNA is the single A which predates the mutually dependent A* and B. It’s just as important to note that RNA does the combined job of DNA and proteins poorly, as that it does the combined job at all. It’s amazing enough that a single molecule can both store information and manipulate chemistry. For it to do the job well would be a wholly unnecessary miracle. What was the very first replicator ever to exist? It may well have been an RNA strand, because by some strange coincidence, the chemical ingredients of RNA are chemicals tha...

Why DNA complexity is not irreducibley complex.