Shipud writes: A study was recently published by a group from the University of Illinois, Urbana-Champaign . The authors analyzed the structures of proteins found in the genomes of organisms from the three domains of life. Those domains are eukarya which includes all plant, animals, fungi and some microbes; bacteria, and archaea which is a group of single-celled microorganisms distinct from eukarya and bacteria. The researchers also included a group of viruses known as NCLDVs (Nucelocyptoplasmic Large DNA viruses), Their conclusion is these viruses may have evolved from a, now extinct, fourth domain of life. Viruses are not considered to be alive, or even to have a place on the universal tree of life, by most researchers. So their claim has far-reaching consequences in our understanding of the origins of life.