PT - JOURNAL ARTICLE AU - Arshan Nasir AU - Kyung Mo Kim AU - Gustavo Caetano-Anollés TI - No ‘small genome attraction’ artifact: A response to Harish et al. ‘Did viruses evolve as a distinct supergroup from common ancestors of cells?’ AID - 10.1101/050179 DP - 2016 Jan 01 TA - bioRxiv PG - 050179 4099 - http://biorxiv.org/content/early/2016/04/28/050179.short 4100 - http://biorxiv.org/content/early/2016/04/28/050179.full AB - In a recent eLetter and associated preprint, Harish, Abroi, Gough and Kurland criticized our structural phylogenomic methods, which support the early cellular origin of viruses. Their claims include the argument that the rooting of our trees is artifactual and distorted by small genome (proteome) size. Here we uncover their aprioristic reasoning, which mingles with misunderstandings and misinterpretations of cladistic methodology. To demonstrate, we labeled the phylogenetic positions of the smallest proteomes in our phylogenetic trees and confirm that the smallest genomes were neither attracted towards the root nor caused any distortions in the four-supergroup tree of life. Their results therefore stem from confusing outgroups with ancestors and handpicking problematic taxa to distort tree reconstruction. In doing so, they ignored the details of our rooting method, taxa sampling rationale, the plethora of evidence given in our study supporting the ancient origin of the viral supergroup and also recent literature on viral evolution. Indeed, our tree of life uncovered many viral monophyletic groups consistent with ICTV classifications and showed remarkable evolutionary tracings of virion morphotypes onto a revealing tree topology.