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RE: " we're evolved for radiation " - geophysicist on pole reversals
Jim,
I think you are over responding to my questions. My original question,
which may not have been too clear, is why did the author think that the
diminishing magnetic field affect life on earth? Again, my impression is
that the atmosphere is our primary solar and cosmic radiation shield. Also,
the phrase that life "evolved for radiation" seemed strange to me.
As I understand it, evolution is a response to a changing environment. If
you put primitive cells into a flask and gave them all the energy (heat) and
nutrients to exist, would they evolve beyond their? I would think not.
Even if a genetic change would occur, it might not express itself. However,
some stress, such as a reduction in food supply, would probably result is
some evolutionary change. Of course, not all of the cells would evolve in
response to the stress. (When I was in graduate school to selectively
choose E. coli and other bacteria that had specific genetic markers, like
those that were unable to survive without the addition of specific amino
acids. We did not have a lot of the techniques and markers used now.) If
life exists on Mars or other places in our Solar System, it is because the
organisms can survive in their present environment, and the environment
prevents future chances for survival. If their environments improved, they
might have the opportunity to evolve. What I am trying to say is they have
"geared up" for survival, but cannot advance.
With regard to ionizing radiation, I view it as another environmental
factor, like heat, UV radiation, food, etc. While you say that it is
essential, you would have to evaluate the response of each and every
biological system to see if that was true. (I think you can say it is
essential for some systems, but only those you test and prove it is
essential. To say it is essential of ALL cells, you would have to test ALL
cells.)
While you can say that DNA is conserved, I am not sure it is provable or
matters either. How do you know that a certain codon that was essential for
a unicellular creature exists it human cells? You can probably decode the
sequence, but if is cannot be expressed, how do you know if it is the true
original sequence, or a result of recombination from more distant genetic
sequences? When radiodurans repair DNA damage, do they use the same
molecules humans use?
By the way I got rid of my high school biology books years ago. My reading
in science has become more contemporary and challenging.
My second question was to determine when the last "flip-flop" occurred. It
would have been interesting if any civilized culture had reported on any
events they witnessed, like no auroras. Also, besides mass extinctions,
there have been mass diversions of species that have occurred. Stephen
Gould was a proponent of this aspect of evolution. I wonder if any magnetic
shifts correlated with such evolutionary events.
Have a good week.
-- John
John Jacobus, MS
Certified Health Physicist
3050 Traymore Lane
Bowie, MD 20715-2024
E-mail: jenday1@email.msn.com (H)
-----Original Message-----
From: Muckerheide [mailto:muckerheide@attbi.com]
Sent: Monday, November 04, 2002 10:12 PM
To: John Jacobus; radsafe@list.vanderbilt.edu
Subject: Re: " we're evolved for radiation " - geophysicist on pole
reversals
on 11/3/02 8:59 PM, John Jacobus at jenday1@MSN.COM wrote:
> Jaro,
>
> What is meant by "we're evolved for radiation?" Had humans evolved the
last
> time it occurred, or was life more primitive?
What? This is just biology. Cells/organisms work the same in humans and all
eukaryotes. Even to prokaryote functions. (Even though organisms have
different rates, e.g., radiodurans repairs DNA a million times faster than
humans.)
"Evolutionary biology" shows that humans have "evolutionarily conserved DNA"
back to "primitive" cells.
[Last year I found these basics now in high school biology texts!]
Cells, and organisms, fail to function without radiation. Radiation is not
something we "survive," it's essential. Dose rates below about 0.01 mr/hr
cause physiological damage, with health consequences, not just irrelevant
chromosome aberrations, etc. [Note: <0.01 mr/hr equates to <90 mr/yr.]
. . .
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