changing rad levels over time (2)

[Andrew Karam <karam.1@osu.edu>]

One thing I forgot to mention in my previous message is that we are trying
to find out if the ability to withstand higher radiation levels in the
distant past could have carried on to current organisms.  The problem is
that we can't think of a good reason for radiation resistance to have been
retained over 3.5 billion years and a large reduction in background
radiation levels.  One possibility is that nearby supernovae may have
"spiked" rad levels sufficiently high with a sufficiently short periodicity
to maintain this ability.  Using the results of one paper suggests that the
Earth would have been exposed to a doubling dose (100 R) about every 2-5
million years.  This may have produced enough additional C-14 and H-3 to
affect even sheltered organisms.  

If anyone can think of a plausible mechanism for mutation repair to retain
primitive capabilities over this length of time OR if anyone can suggest
some test to show that modern organisms have mutation repair capabilities
similar to those of early organisms, we'd appreciate your input.  And we
are not hesitant to share credit where it is due (ie we won't take your
idea and present it as ours).

Andy
The opinions expressed above are well-reasoned and insightful.  Needless to
say, they are not those of my employer.(with apologies to Michael Feldman)


Andrew Karam, CHP				"The mind is not a vessel
karam.1@osu.edu				to be filled but a fire
						to be lighted." (Plutarch)
Ohio State University 
Radiation Safety Section
1314 Kinnear Road
Columbus, OH  43221
(614) 292-1284    	(614) 202-7002 (fax)