Richard Dawkins. The selfish gene (№ 182011)

Viruses consist of pure DNA (or similar self-replicating molecule) surrounded by a protein coat. They are all parasites. It is assumed that they arose out of the "rebellious" genes that were freed and now travel from body to body directly through the air, rather than the more traditional way - in such "crews", as the sperm and egg. If so, we could equally well see ourselves as a colony of viruses.