Re: Did life originate with viruses?

Perplexed in Peoria wrote:

"dkomo" <dkomo871@xxxxxxxxxxx> wrote in message news:dtq8ie$16vk$1@xxxxxxxxxxxxxxxxxxxxxx

There's a provocative article in the latest (March 2006) issue of
Discover magazine called "Unintelligent Design" by Charles Siebert. The
blurb for it says "A monstrous discovery suggests that viruses, long
regarded as lowly evolutionary latecomers, may have been the precursors
of all life on Earth."

http://www.discover.com/issues/mar-06/cover/

This "monstrous discovery" is that of the Mimivirus, the largest virus
ever discovered. Its genome weighs in at a whopping 1.2 million
letters, at least ten times larger than a typical virus, and larger than
the genomes of 20 or more parasitic bacteria. It has about 1000 genes,
and is one of the few viruses that can be seen with an ordinary microscope.

The article makes a number of amazing statements that I'll just list
here without comment:


[snip amazing statements]

I don't know how accurate these claims are. Comments?

Here's a research paper on the Mimivirus:

http://www.pnas.org/cgi/content/full/102/41/14689


It looks like the Mimivirus will be an interesting beastie to study, but
for the life of me, I can't see what relevance it could possibly have to
the origin of life. The PNAS paper references an earlier Science paper.
Science 19 November 2004:
Vol. 306. no. 5700, pp. 1344 - 1350
And the abstract of the Science paper mentions that the protein synthesis
components of Mimi include some tRNAs and some aaRSs. This suggests that
it might alter the effective genetic code of its host. Very interesting,
if true. But the main point of the paper is apparently the construction
of a phylogenetic tree which has Mimi branching from the tree on the Eukaryote
line after the Archaea, but before any branchings of modern Eukaryotes.
IMHO, this is almost certainly an artifact, as suggested here.
http://www.sciencemag.org/cgi/content/full/sci;308/5725/1114a

While viruses or something similar may well have been involved in mediating
rampant gene transfer in the early days of life, it is inconceivable to me
that life could have originated as a parasitic virus. Parasitic on what?
And even if you use a definition of life with fine print forcing us to
conclude that the virus was a 'parasite' of some membrane bound host that
was 'not really alive', you still have to say what the living virus gained
by infecting the non-living host. Activated nucleotides, like modern viruses?
If so, I would like to see an explanation as to why the non-living host
was making them, and if it was making them, why it needed a viral infection
to take that next evolutionary step to nucleic acids.

In any case, the discovery of extra-large genomes is not a step toward
understanding the origin. What we need to find is extra-small genomes.



<hand-waving mode on>

Besides the nuclear genesis hypothesis, the other proposal the Discover
story mentioned all too briefly was that viruses were the *precursors*
to cell-based life. It's hard to see how that can be since viruses
can't replicate on their own, nor do they have an enclosed metabolism.

From bits and shards in the story, I think the following is what the
viral genesis proposal is saying. A long, long time ago during the RNA
world, there were these segments of RNA floating around which could
replicate on their own. They were surrounded by primitive protein
coats. These were the ancestors of all modern day viruses, as well as
of the other three kingdoms of life. Eventually some of them acquired
cell walls, metabolism, a cytoplasm and DNA, and became the first crude
bacterial organisms. The original viruses evolved to simpler forms
which no longer reproduced on their own, nor were alive in the modern
sense.

<hand-waving mode off>


--dkomo@xxxxxxxx


.

Relevant Pages

  • Re: Did life originate with viruses?
    ... inconceivable to me that life could have originated as a parasitic ... with fine print forcing us to conclude that the virus was a ... Discover story mentioned all too briefly was that viruses were the ... that they have linear DNA like eukaryotes rather than circular DNA. ...
    (sci.bio.evolution)
  • Re: Evolutions problems
    ... >>> Actually, at least one virus has been assembled from ... Are viruses qualified as living? ... viruses as a form of life. ...
    (talk.origins)
  • Re: Did life originate with viruses?
    ... that life could have originated as a parasitic virus. ... conclude that the virus was a 'parasite' of some membrane bound host that ... Activated nucleotides, like modern viruses? ...
    (sci.bio.evolution)
  • News: Virophage suggests viruses are alive
    ... The discovery of a giant virus that falls ill through infection by another ... virus1 is fuelling the debate about whether viruses are alive. ...
    (sci.bio.evolution)
  • Re: Did life originate with viruses?
    ... This "monstrous discovery" is that of the Mimivirus, ... and is one of the few viruses that can be seen with an ordinary microscope. ... for the life of me, I can't see what relevance it could possibly have to ...
    (sci.bio.evolution)