On the Origin of Cells, Genomes and Viruses

Eugene V. Koonin

National Center for Biotechnology Information, National Library of Medicine, NIH, Bethesda, MD 20894

Origin of Life is the hardest problem in biology if not in all of science. We might never know what actually happened on Earth some 4 billion years ago that resulted in the emergence of the first cells.

Nevertheless, the only hope to arrive at plausible scenarios of those pivotal events is to seek consilience of (at least) four complementary approaches: 1) theoretical modeling of the first stages of life’s evolution, 2) bottom up approach, that is, attempts to recapitulate the events at the origin of life through physico-chemical experimentation, 3) top down approach, that is, attempting to back extrapolate from comparative analysis of extant genomes as well as protein and RNA structures, 4) astrobiology, that is, harnessing data on exoplanets and meteorites for potential insights into the origin of the earthly life, the only one known to us. I will present a mathematical model of the origin of cells via symbiosis between primordial reproducers (protocells) and primordial replicators that gave rise to genomes. I will further resent theoretical arguments for the inevitability of the emergence of parasites in the evolution of replicators and the essential role of host-parasite coevolution in the origin of biological complexity. I will then discuss several attempts on top down reconstruction of the earliest events in biological evolution, in particular, the origin of the translation systems within the primordial RNA-peptide world, the origin of viruses and the concomitant origin of replication and transcription.