From: Robert J. Bradbury (bradbury@aeiveos.com)
Date: Wed Sep 03 2003 - 20:05:18 MDT
On Wed, 3 Sep 2003, Kevin Freels wrote:
> If the majority of cancers occur in individuals after the age of
> reproduction, there would be no filter to remove them.
This is known in gerontology as being due to the "declining force
of natural selection". It is one of the two major theories as to
why aging occurs -- the other being "antagonistic plieotropy".
> In fact, any genetic mutation that caused any type of problem after the
> reproductive years should persist through the years. This would leave most
> people today with a variety of mutations that continue to be passed on to
> their offspring. They would continue to persist over hundreds of millions of
> years with no selection pressure applied whatsoever.
Not so -- K-selection vs. R-selection will apply selection pressure
particularly if the "elders" of a group contribute significantly
to the survival of their children, grand-children, etc. This seems
likely to be true in humans, elephants and whales -- though there
is still a fair amount of academic debate on this topic.
It is also true that a fair amount of various causes of death may
be due to mutations that occur during development (causing some childhood
cancers) or during adulthood (See [1] for example). These may not
impact the germ line cells and so there is no inheritance involved
at all.
Cancer is a Murphy's Law type situation: "Anything that can go wrong
will go wrong." [2]
Robert
1. Wikman H, et al,
"hOGG1 polymorphism and loss of heterozygosity (LOH): significance for lung
cancer susceptibility in a caucasian population"
Int J Cancer. 2000 Dec 15;88(6):932-7
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11093817&dopt=Abstract
2. http://dmawww.epfl.ch/roso.mosaic/dm/murphy.html
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