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# why do we die?

Fri Nov 3 07:59:03 EST 1995

```	Why do so many of you think that aging is something which can be
selected for?  A living organism is a complex system of interactions.  Someone
commented earlier that life was a process.  To not age means to remain in or
near some sort of equilibrium, but we are finding more and more that true
equilibria do not exist in real systems.  Instead, what you have is a set of
reactions that tend to oscillate irregularly and unpredictably around what we
like to consider the equilibrium point.  In chaos theory these are called
strange attractors.  Ie. something happens in the body, and one of the body's
systems responds to bring the body back near the "equilibrium".  The system
rushes the body past the equilibrium point, and then usually gets feedback
from another system that tells it to stop.  The other system will then swing
the body back toward the midpoint - again passing it and triggering the first
system again.  This is great, of course, but the fact is that these are
complex systems.  Complexity theory tells us that it is possible to see
chaotic behavior in these kind of systems with often the same regularity as
ordered behavior.  So during this "oscillation" we could get into a sort of
harmonic oscillation where the system swings farther to the extremes with
each pass, eventually reaching the point where the systems or the thing which
they regulate are actually damaged!  Now the body has many backup systems
which will pretty much shut down these reactions and restart them so that
they will begin to behave properly, but that does nothing about the damage
that has occurred.  Consider the many forms of heart disease, and the fact
that they often follow just this sort of pattern.
What I'm getting at is that at any given moment of time you might have
only a slight chance of having a problem with one of your systems, but that
over a length of time you will have these problems, with associated
damage accumulating.  Now before you talk about selecting against these kinds
of errors, I want to tell you that mathematically, these behaviors are
inherent in the kinds of complex systems that allow higher forms of life.
There is no way to eliminate this kind of potential chaos, because that
possibility is exactly what makes these systems able to be responsive!  They
aren't two things - eliminate the potential chaos, and you eliminate the
capacity to act.
Furthermore, there are many examples of complex systems (created
from simple equations interacting) which inevitably run down simply because
of the nature of the interactions.  There is no damage done, these are simply
calculations, after all.  It is just that over a number of iterations the
system simply reaches a state where there is no more activity.  It is entirely
possible that the equations that govern the complex chemical interactions of
organic life (particularly the more complex life) are of this type.  It seems
likely since by far the most interesting and complex mathematical systems
often have this character.

Well, enough of a word from the peanut gallery.

Thomas M. MacKay
Development Systems
College of William and Mary

(804) 221-1040