A study of the proteins of giant viruses adds them to the list of primitive life forms that have existed since the dawn of life. They seem to constitute a fourth superkingdom. Professor Gustavo Caetano-Anollés led the analysis.
Scientists found ancient structural patterns in the folds of the virus proteins, which are virtually molecular fossils. Folds that are common to all organisms studied are the oldest. Less common folds are, literally, new wrinkles.
The researchers looked at archaea, bacteria, eukaryotes, and both kinds of viruses. The giant viruses have biochemistry for making proteins, which small viruses have lost.
Modern viruses have lost much of their biochemical machinery and become obligate parasites of an extreme kind.