RedGage

Description

Viruses are widespread and come in many shapes and sizes. They play an important part in the evolution of many species. But are they alive and should they be included as part of the tree of life? Moreira and López-García discuss ten reasons why they should be excluded. When viruses were discovered, they were accepted as missing links between the inert world and living organisms. However, this idea was soon abandoned as information about their molecular parasitic nature accumulated. Recently, the notion that viruses are living organisms that have had a role in the evolution of some essential features of cells has experienced a renaissance owing to the discovery of unusually large and complex viruses that possess typical cellular genes. Here, we contend that there is strong evidence against the notion that viruses are alive and represent ancient lineages of the tree of life.