Virus Origins and the Origin of Life

Abstract

Viruses are enigmatic, with scientists debating, often heatedly, about the nature of their existence, such as whether viruses should be categorized as living or non-living. They are not even represented in most conventional trees of life. However, viruses have played a driving role in the co-evolution of life on Earth since its origins. Viruses can serve as molecular fossils, providing a possible glimpse at a pool of genes that may have been present from a time before the Last Universal Common Ancestor (LUCA). The study of virology and the origin of life have often been intertwined. Since the earliest studies of viruses, viruses have been hypothesized to be ancient, possibly anteceding cell-based life. Other hypotheses propose that cell-based life preceded viruses, with viruses “escaping” from cellular life forms. This chapter will introduce viruses and their relationship with the origin of life, including the various proposed origin scenarios involving viruses and virus-like elements.