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Re: CNN article on radical mutation/doomsday genes

--Original Message-- From: Betty Cunningham <bettyc@flyinggoat.com>
29 November 1998 23:24


Thanks for that ref, Betty.  It looks like being one of the best science
bookmarks for me, particularly if you chop off the bit after "science/", so
you can get at all the other daily sites too.

I was concerned by this paragraph in it:

"Evolution is often thought of as incremental," said biologist Andrew
Cossins of the University of Liverpool in England. "But the fossil record
contains many examples of apparently rapid changes in body form. This
mechanism provides, for the first time, a means by which changes in body
form can be substantial and stepwise rather than progressive."

This mechanism is of course not the first to explain sudden evolutionary
changes, as some people (me for example) would think on a first reading.  On
reflection I suppose he is talking about enormous differences between a
particular offspring and its parent.  [No - on a third reading I think *he
was* making the mistake!]  All right, this mechanism might well do that, but
that is not required for punctuated evolution;  a species is a bit like a
drop of mercury in a hollow in a somewhat mobile rumpled blanket.  It sits
in its hollow, keeping fairly still, or occasionally following slow
movements of it, until the lip of the hollow drops and the gene(or mercury)
pool plops out over the edge and rushes to another hollow.  OK, very crude,
and even I can think of a few aspects it doesn't cover, but that is why
evolution is punctuated, not this heat shock effect.

In fact, if it were true, it would only cause punctuated evolution in
response to abnormal heat.