In the case of, say, a factory machine tool, von Neumann observed, you have an automaton that can turn out very complex parts but not another machine tool. Likewise, a universal Turing machine can output an arbitrarily complex tape but not another Turing machine. However, in almost any biological organism, you have an automaton that can not only reproduce identical copies of itself but also (through evolution) give rise to organisms that are more complex than itself. So von Neumann asked, What are the essential features required for an automaton to reproduce itself and to evolve? To give his
...more
