1. A computer system comprising: a set of computers including at least one computer providing for running one or more virtual machines, said set progressing through a series of configurations including virtual machine configurations; and a chronology generator for recording a chronology for said series of computer configurations in computer-readable media; wherein a new virtual machine configuration can arise because a virtual machine is cloned, said chronology means generating a multi-generational genealogy of virtual machines in response to a genealogy command; and wherein said chronology generator provides a measure of genetic diversity in said genealogy.