Marilyn Harris wrote:
>> Nobody knows.  Also, "average" age isn't a very useful measure of
>> health, because it includes child mortality, accidental deaths,
>> warfare, etc.
> 
> Actually I was thinking in terms of the diseases of older age that
> afflict us 

I thought that's what you were thinking, which is why I pointed out
that average age wouldn't tell us much about that, even if we knew
it.  And, sadly, we still don't have very good answers to that 
question even about _today's_ populations, i.e. although there are
studies about relative incidence of specific cancers in various
populations, what we really need is some good _comprehensive_
statistical data on life-expectancy at various ages of various
populations, and under various dietary and environmental 
conditions.  And there just simply isn't any such data, at
least not of useful quality.  It's astonishing how poor in
scientific-grade health and epidemiological data our "information
sciety" really is.

> So, I wonder how much simple aging is as an
> important predictor of cancer?

It is my understanding that it isn't.  Cancer is not an age-
related disease, although it is a highly probabilistic disease.
That is to say, if in a given year 0.01% of all persons get 
colon cancer, then if you live 50 years your chance of getting
colon cancer in your lifetime is 0.50%, but if you live 100
years it's 1.00%.  Given that colon cancer can be fatal and 
that at least some other potential causes of death are NOT
independent of age, that also means your probability of dying 
from it rather than other causes gets higher the longer you 
live.  But in any given year your chance of contracting it 
remains 0.01% regardless of whether you're 20 years old or 90,
so it's not age-related.

This is my naive understanding, and a) it may not be entirely
true, and b) it may not be the same for all cancers, i.e. some 
cancers may be less independent of age than others.  In 
particular, cancers that are caused by exposure to toxins
should be more dependent on length of exposure, which in turn
is not going to be independent of age, i.e. in the case of
lung cancer from cigarette smoke obviously most older smokers
have been smoking longer since most smokers start at about
the same age.

To be honest, I'm mostly speculating based on my lay 
understanding here... if anyone can point to sources of 
hard information on this question it would be appreciated!

:j