The origin and function of orphan genes (OGs) is a mysterious problem in modern molecular biology. The recently developed PHOG database helped to shed light on some aspects in the evolution of these genes. Presumably, a rapid evolution is the main factor that influences the origin of OGs. The evolutionary rate of particular genes reflects the degree of their conservation, although exceptions from this rule contribute to the dynamic process of genome evolution during speciation. It is demonstrated that a great number of OGs detected is an artifact of insufficient sequencing. If DNAs of all organisms living on Earth were sequenced, then the OG number would be greatly reduced, giving the way to genes specific of particular taxonomic groups.