A useful characteristic

A useful characteristic upon which to base a definition of life is that of descent with modification: the ability of a life form to produce offspring that are like its parent or parents, but with the possibility of some variation due to chance. Descent with modification is sufficient by itself to allow evolution, assuming that the variations in the offspring allow for differential survival. The study of this form of heritability is called genetics. In all known life forms (assuming prions are not counted as such), the genetic material is primarily DNA or the related molecule, RNA.

This argument would, however, include replicating elements which have been observed to evolve, but are not generally accepted as being alive. Examples include viruses, plasmids, transposons, satellite DNA. Another exception might be the software code of certain forms of computer viruses and programs created through genetic programming.