Reclassifying Viruses as Living?
kinman2 at YAHOO.COM
Tue Mar 14 21:30:30 CST 2006
I have always thought of viruses as being forms of life. And I would also agree with Cornelia's statement that primitive viruses lie at the root of life. That is why in my 1994 classification of life, I placed a new Phylum Parabacteria at the very base of Kingdom Monera. I divided it into two Classes. Class Progenotea is divided into two Orders: Paraprogenotida (precellular progenotes), which would include the earliest viruses, and Euprogenotida (for obcells, protocells, or whatever the earliest cellular organisms turn out to have been).
The other Class Viralea is an admittedly polyphyletic group for modern-day infectious nucleic acids (viruses, viroids, and virusoids). Perhaps all of these are escaped genes of one kind or another, that have been popping in and out of cellular organisms since the very first Euprogenotida evolved by encapsulating just the right primitive nucleic acid. Before that happened, nucleic acids parasitized each other and the organic soup which they had helped to create.
Viralea parasitize all forms of cellular life, just as bacteria parasitize each other and eukaryotes. And heterotrophic eukaryotes (including us humans) can be said to "parasitize" (sensu lato) anything below us in the food chain, ultimately getting most of our energy and raw materials from phototrophs at the bottom of the food chain. Anyway, if primitive viruses helped create the original organic soup (a relatively unbounded cell of protoplasm, if you will), and are ancestral to all cellular nucleic acids, then viruses should be seen as living, and as a vital part of the beginnings of life and its subsequent evolution. That modern-day viruses are highly specialized is not surprising, since they have been evolving along with us cellular organisms (packets of organic soup) for billions of years. Like Walter said, if they evolve (and they have helped us to evolve), then they are an integral part of life (hence alive).
P.S. If Cavalier-Smith's "obcell theory" is correct, cellular life's ancestral nucleic acid was actually attached to the outside of a unilayered obcell. This obcell would have internalized the nucleic acid by enveloping it (in a sort of primitive "gastrulation"-like event) and creating the first true prokaryote. The cenancestor would thus have been a "diderm", and all monoderm taxa (gram positives and all their descendants) arose when the outer cell layer was subsequently lost.
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