X-Message-Number: 11873
From: Thomas Donaldson <>
Subject: For Robert Moore: more about the evolution of aging
Date: Wed, 2 Jun 1999 23:52:59 +1000 (EST)

To Robert Moore:

If you want to know more about evolutionary theories accounting for aging
and lifespan you might first look at the papers I cited in my posting for
the previous Cryonet.

However you do ask some questions worth answers. The very first point I
will make is that for men at least, there is no time at which the man
cannot sire a child. This means that someone who lives to 70 has a greater
opportunity to produce more children than someone who only lives to 60.
Moreover, even for women, before 1850 everyone was old at 40, and
menopause played no special role. We see it now because women are living
for longer, too.

For men at least, there is no upper lifespan beyond which they cannot
produce children. If this is true for men, then the genetics involved
suggests that women would carry similar genes, too. Basically, though, it
is simply false that after a certain age we can do no more than help
our previous progeny to survive. Not only that, but even now particularly
prosperous men WILL produce children at high ages by wedding a much
younger woman. 

The paper by Hamilton even goes into detail about just how strong the 
selection will be given the kind of factors I have discussed here. Yes,
it's true that at lower ages right now the selection is stronger; but
it only becomes weaker as we age, it does not go away. Hamilton discusses
that kind of selection as different functions depending on age of abstract

It's also reasonable to ask about those who, even in Roman or Greek times,
lived to what we still consider a high age. The really important thing
to understand here is that such people in the mass of the population 
were extremely rare. We may remember them because of what they did, but
in terms of reproduction (producing children) they were so rare that
they did not have any GENETIC impact on the rest of the human race. The
remarkable thing that is happening now is that such high ages have now
become the norm, rather than the exception. 

Not only is this a matter of theory, but some students of aging have
looked at records of lifespans over time. For Christian burials this is
a lot of work but the information is often right there on the tombstones.
It turns out that until about 1800 (when a bulge had appeared in the
general lifespan curve, which become higher and stronger into this 
century) a graph of lifespans did not look at all like the one we see
now. Instead it looked exponential... with time, more people died at
a constant exponential rate (as you can guess, that rate was much higher
than at present). You might look in your nearest academic library for
the HANDBOOK OF AGING (Biological section). It is a collection of papers
on all the different sides of aging.

Our picture of the past, now, is badly skewed by the simple fact that
we hear nothing from those who were illiterate (the large majority) but
only from those who were literate and in the upper classes. These were
people who lived quite exceptional lives compared to that of the rest of
the human race living at that time. In terms of what people of the time
understood, they knew that death would come to everyone ie. that there
was such a thing as aging, but it was far from the most prominent cause
of death for most people ie. the peasants and the poor, who had no voice
in history. 

You've also probably heard of some people such as the Pygmies who are said
to believe that death is always caused by some kind of magic directed at 
the person who dies ie. that it is not at all the "natural" state of
affairs. Since their deathrate curve was exponential, they weren't really
all that foolish in their belief. They simply had never encountered aging
in the way we have. There is also a strong suggestion in the Epic of 
Gilgamesh, which comes down to us from the very earliest urban
civilizations, that the realization that death came to everyone occurred
AFTER we began to live in cities and a very small minority of the
population lived long enough to die of aging, not of any bacterial
or viral disease or injury. Since people aren't stupid, such a realization
would also spread to those who did not live in cities, too... unless they were
isolated enough.

Finally, I hope you understand that I'm not just giving you my private
opinion. Thinking about EVOLUTIONARY causes of aging has gone on for some
time, as you can see if you read the papers I suggest. I don't claim any
originality here, but I will say that these ideas don't seem to have
spread as far as they should.

			Best and long long life to everyone,

				Thomas Donaldson

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