X-Message-Number: 22656
Date: Mon, 6 Oct 2003 10:14:22 -0400 (EDT)
From: Charles Platt <>
Subject: life extension and population

David Stodolsky writes:

"One way to reduce fuel consumption is to limit population.
This solution is counter to the promotion of any life
extension technology."

And this assumption is based on...?

First, population is limiting itself. The demographic
transition is pretty much undeniable at this point, with
births per female lifetime down to 1.2 in some Euro nations
(which are now worried about population _decrease_). Of
course this has happened at the same time that average life
expectancy has increased. Therefore your suggestion that life
extension tends to worsen the population problem has already
been disproved, if we are talking about average life
expectancy. Women don't necessarily have more children just
because they expect to live longer; the reverse has turned
out to be true.

If you're concerned about the effects of lengthening the
*maximum* human lifespan (say, from 120 to 250 years, more or
less) it's important to remember that this only leads to
linear growth as opposed to the exponential growth caused by
an increase in the birth rate. Therefore I regard an increase
in the maximum lifespan as being far less likely to impose
"population stress" than an increase in the birth rate. But
what are the actual numbers?

A few years ago, I searched for any kind of UN-sponsored or
other simulation/projection of the consequences of an
increase in maximum lifespan. Finding nothing, I called
various government agencies and nonprofit population study
groups. So far as I could tell, no demographers anywhere had
ever studied this issue. The people at Worldwatch and the
Population Institute, for instance, were baffled by my
question.

So, I wrote my own little simulation program and ran various
scenarios (all relating to US population). I found that if
maximum lifespan increases by 5 years during each future
10-year period, while fertility rate decreases by 1.5 percent
every 5 years, and an assumed reduction in age-related
diseases lowers the risk of death by 60 percent every five
years, everything balances out. The result after 200 years is
the same as if the current birth rate and maximum lifespan
remained the same, coupled with a slight decrease in risk of
death in higher age groups.

Of course life extensionists are expecting a much bigger
increase in maximum lifespan, and it may happen more
suddenly instead of being spread out over a couple of
centuries. And nanotechnologists have their own view of the
future. But my projection is more consistent with the
historic rate of change of population variables.

In any case, the principle is very clear: An eventual
doubling in maximum lifespan, coupled with a very large
reduction in disease risk, can be offset by a relatively
modest decline in fertility. The decline that would be
necessary in the US has already been exceeded in some other
nations.

I believe the concern about the effects of an increased
maximum lifespan is rooted more in psychology than in
reality. We feel an instinctive resentment in response to the
idea of 150-year-olds becoming a dominant age group. This
resentment probably is linked with an assumption that someone
of that age is parasitic and unproductive. Of course if life
extension therapies are successful, the assumption is wrong.

One last point: Since life extension will cost money, it
should affect richer nations more than poorer nations.
Fortunately, richer nations have lower birth rates than
poorer nations, generally speaking, and are much better
positioned to tolerate an increased maximum lifespan without
catastrophic environmental consequences.

Anyone who worries about population should be much more
concerned with third-world birth rates than first-world life
expectancy.

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