Why the history of viruses matters

There are three dominant models of viruses that seem to complete each other.

• The "virus first" model suggests that simple forms of viruses existed before cells and may have provided the raw material for the development of cellular life.
• "Escape" or progressive model proposes that viruses come from genetic elements that escaped from the genes of larger organisms.
• The "reduction" model suggests that viruses were once larger, free-living organisms that lost their genetic information and ended up smaller and unable to reproduce except inside the cells of other organisms.