George McCabe <xrghm at lepvax.gsfc.nasa.gov> wrote
What motivates "random" mutations in an organism like a
virus? Some of the talk here seems to attribute intelligence, even malice,
to a virus. I have always assumed that strong if infrequent events like
cosmic rays, disuptive contact with a foreign chemical agent, and the like...
create new strains. It is intriguing to think though that there exists
some more tangible, perhaps deterministic motivator. What for example,
caused a new strain of Ebola, airborne and monkey specific to appear, if
it didn't exist undetected before.
By no means did I intend to ascribe an intelligence to viruses,
but random mutations are strictly that--random mutations. These could be
brought about by the means you suggested or errors in DNA replication,
modification of the viral DNA by the host, etc. There are lots a
mechanisms by which random mutations arise. Here the term "random" just
refers to the topological position of the mutation in the genome and that
there is not a 'force' that directs mutations toward any pre-established end.
As for why Ebola and similar strains were not detected, no one may have
ever looked. If Ebola is highly lethal and localized to the deep
interiors of the tropical jungle, then it is unlikely that scientists
will notice the virus. The latter idea has been used to argue for more
bio-watch centers in the tropical rainforest. Some people argue that if
such centers were around twenty years ago we would not have the current
problem with HIV. (but the latter is not my opinion).
William Jewell College
Liberty, MO 64068
eMail mowjmat at coop.crn.org