We live in genome-centric times. Already high-throughput sequencing machines have unraveled genetic blueprints for thousands of organisms, as well as viruses and organelles, and cheaper, faster technology promises thousands more in the near future. But where did the first genomes come from—and how? What rules govern how they function and what they look like? And why do they vary so much in size from organism to organism?
In a special theme issue of the Philosophical Transactions of the Royal Society B, two dozen experts discuss genome evolution—starting from the deep beginnings in the presumably RNA world, through rampant genome innovation through lateral gene transfer across species, to the divergent histories of particular genes and gene families. They touch upon an emerging concept of the supergenome, which describes the set of all genes in the local environment that a prokaryote has potential access to because of lateral-transfer processes. Based on genomes of primitive organisms, researchers are piecing together the genetic tool kit of the earliest bilateral animals. And one paper argues that viruses, being vast sources of genetic material, cannot be dismissed as nonliving material.