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Viruses NOT fourth domain of life, says RealClearScience editor

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At Real ClearScience, Alex B. Berezow advises us to “Simmer Down” because viruses are “Not ‘Fourth Domain’ of Life”:


The biggest difference between cells and viruses is their method of replication. All three domains of life replicate by cell division, which implies that this trait was derived from the Last Universal Common Ancestor (LUCA). (In other words, LUCA is the theoretical ancestor of Bacteria, Arcahea, and Eukarya.)

Viruses, which do not replicate by cell division, probably evolved independently multiple times, “here, there, and everywhere,” as the authors conclude. Some probably evolved before LUCA, and others well after LUCA. Many have likely exchanged genetic material via horizontal gene transfer. Lumping them all into a fourth domain, therefore, makes little sense.

Little sense? Not necessarily. A fourth domain can consist simply of “Others.” What they have in common is that they are thought to have evolved multiple times and exchanged genetic material by horizontal gene transfer. (Where they got all that material is a separate question.)

The viruses that set this fourth domain idea in motion are the recently discovered giant ones. See, for example,

The Scientist asks, Should giant viruses be the fourth domain of life?

Biggest virus ever: “We don’t understand anything anymore!”

Largest virus genomes hint at fourth domain of life

See also: Pandoravirus, Mimivirus, and Megavirus.

Berezow tells us that the whole affair is not academic but rather raises anew the question “What exactly is life, and how did it evolve?”

Indeed. Here is a small slice of the problem:

The definition of life has reached the point where science historian George Dyson tells us, “Life is whatever you define it to be.” Richard Dawkins has suggested it is “anything highly statistically improbable, but in a particular direction.” And at a year 2000 international “What is life?” conference, no two definitions were the same. Biochemist Edward Trifonov noted that there are 123 definitions available and, undeterred, promptly proposed his own: Life is self-reproduction with variations. Which was just as promptly contested. In a 2012 issue of philosophy journal Synthèse, Edouard Machery concluded that “scientists, philosophers, and ethicists should discard the project of defining life.”

Still in the game, astrobiologist Charley Lineweaver proposes a new, non-Darwinian approach to defining life:

Bigger slice. The whole pie.

If we don’t know what life is, the question of whether viruses are a fourth domain is academic, actually. In fact, contra Berezow, it is a classic illustration of an academic question. It cannot be settled with available information.

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of note: Can't seem to find any explanation, much less a demonstration, as to how that incredible machine evolved in the preceding article! bornagain77
After 40 years, the first complete picture of a key flu virus machine - Nov. 20, 2014 Excerpt: "The structures reveal how the polymerase specifically recognises and binds to the viral RNA, rather than just any available RNA, and how that binding activates the machine. They also show that the three component proteins that make up the polymerase are very intertwined, which explains why it has been very difficult to piece together how this machine works based on structures of individual parts. Although the structures of both viruses' polymerases were very similar, the scientists found one key difference, which showed that one part of the machine can swivel around to a large degree. That ability to swivel explains exactly how the polymerase uses host cell RNA to kick-start the production of viral proteins. The swivelling component takes the necessary piece of host cell RNA and directs it into a slot leading to the machine's heart, where it triggers the production of viral messenger RNA." http://phys.org/news/2014-11-years-picture-key-flu-virus.html bornagain77
They don't know how to define it, have no idea what it is, are trying to understand how it functions at the cellular and molecular levels, but they believe they know how it started and evolved. Now, go figure. Oh, well, whatever, anyway... it's just pathetic. Dionisio

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