Ageing as an evolutionary force

Daniel J Housman house at athena.mit.edu
Tue Apr 14 11:20:49 EST 1992


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	The question has been raised that if the cells in the germ lines
of living organisms have the capability to keep DNA nearly perfectly
intact under attack from free radicals why then is it that the cells
all over the organism are not able to protect themselves in this same manner.
This is a topic that I don't claim to have any expertice but I am 
willing to offer some speculation upon the matter. 
	Ageing like flowering in angiosperms could be an evolutionary 
advantage that promotes recombination and thereby promotes diversity 
that allows survivability. People generally think that aging is a
process which is necessary and a process that must occur merely because
the world is too harsh for an organism to survive in it intact defeating 
entropy for a prolonged period of time. This is not completely 
sensible. It is possible to produce cell lines of cancer cells that 
are essentially immortal. The machinery for immortality exists and were it
to be evolutionarily advantageous to not age and live forever then the
world would have evolved with organisms that were immortal. 
	The reasons why the aging process is useful evolutionarily are as
follows. If there were not a younger generation and an older generation there
would be intermating between generations causing a lack of recombination
that would normally be caused by the constant reshuffling of genes from one
generation to the next. The reproductively active cycles of the organism 
may at one point become inactive to prevent the overexertion of any one
single genotyope during non-selective conditions. Menopause is an example
of this sort. The overexertion would cause a lack of variability in the 
population as a whole and under selective conditions populations with large
amounts of variation would survive. There is no great advantage to staying 
alive longer since major injuries occur making the organism less fit such
as the loss of limbs. The degeneration of the body could be a way to get
rid of the dead weight in the population that would be competing for energy 
 sources so the partially destroyed organisms would be eliminated through an
aging process. Remember that evolution did not occur during the cushy 
non-selective times like today and the immortal organisms would simply 
proliferate without the ability to disappear giving them the problem of
having a lack of adaptability. 
	What this would mean is that there are some inherent causes of aging 
that ought to be conserved throughout the cells of all organisms and the 
DNA must somehow code for this process. This process is probably one of
the fundamental processes of biology and deserves some attention to its
biochemistry. The research that would need to be done would be what factors
be it flaws in the DNA or cellular clocks are causing aging and how can they
be manipulated.

Dan Housman 
95 MIT 




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