Sažetak
In evolutionary biology there is a strong hypothesis that holds that viruses may have been free-living organisms that as parasites were the precursors of life. Their diversity runs into trillions and unlike all other biological organisms some have RNA genomes and some have DNA genomes; some are single-stranded and other are double-stranded genomes; they can only self-replicate within a host cell; and, none contain ribosomes and therefore cannot make proteins. Among the three main theories of where they came from and whether they are alive, one recent account holds that viruses either predate bacteria, archaea, or eukaryotes or coevolved with host cells (Koonin and Martin Citation2005), but while they can evolve rapidly because of their short generation times and large population sizes, viruses cannot reproduce by themselves (Nature, 2020).