Compelling reasons why viruses are relevant for the origin of cells
2and advances of viral metagenomics that establish viruses as a quantitatively dominant component of the biosphere 3 , the evolution of viruses has become a topic of lively discussion 2,4–8 . Several scenarios were proposed according to which viruses antedated cells and contributed to their origin 4,5,7 . The Opinion article by Moreira and LopezGarcia extends this discussion 1 by making three fundamental points: viruses are not alive, contrary to claims that they are 2,5 ; viruses do not belong in the tree of life (TOL); and viruses are not ancient and are irrelevant for the reconstruction of cellular evolution.