Virus world hypothesis

The virus world hypothesis (also called the virus-first hypothesis, the virus early hypothesis or the co-evolution hypothesis) proposes that self-replicatingvirus-like genetic elements existed before cellular life and contributed to its emergence. It is one of several scientific hypotheses that attempt to explain the origin and evolution of viruses.

Modern viruses are obligate parasites that cannot replicate independently of their cellular hosts; thus it may seem more intuitive for viruses to have originated from cells, an idea suggested in the "escape hypothesis". Nevertheless, under the hypothesized "virus world", viruses are theorized to be direct descendants of the very first replicons to arise, and to have emerged simultaneously with or even before the evolution of cells. These primordial soup-dwelling replicons could have evolved into archaic virus-like structures, which in turn became the precursors of cellular life forms, with the latter possibly emerging as factories and reservoirs dedicated to virus production and dissemination.

The hypothesis is considered one of the three classical hypotheses of viral origins, although it is now thought that these hypotheses may not be mutually exclusive, as different groups of viruses may have evolved through different routes, leading to a "chimeric scenario".