Why does aging exist? Why don't we live in a world in which higher animals are built to take a best-shot attempt at biological immortality? We know it's not impossible from a purely technical, biological perspective: the existence of children proves that much.

for all that we suffer age-related degeneration - and frailty, pain and death as a result - we produce healthy, youthful children with each new generation. Our cellular biochemistry contains the potential to rejuvenate and repair itself: children are the demonstrable proof that decay and entropy are not inevitable.

The bottom line is that it all comes down to evolution; I've looked at the way in which evolutionary realities tend to rule out immortality in the past:

[A] worthy summary article for the layman can be found at Joao Pedro de Magalhaes' website.

A perhaps more striking, if overly simplistic, explanation for the existence of aging was given by Jaque Cousteau - no immortality because change is the lowest common denominator, and immortality in a species that cannot radically change itself spells extinction. It will ultimately find itself doomed by environmental changes, if not by evolutionary competition.

This doesn't preclude the possibility of an evolving clade of species with the necessary biochemistry for physical immortality; individual animals just won't have the chance to make much use of it. The Ageless Animals website provides an interesting view of outliers in the evolutionary processes that determine aging.

If you wander over to EurekAlert! today, you'll find another viewpoint on the way in which evolutionary mechanisms lead to the rise of aging, starting with the simple organisms right back at the beginning:

Scientists have puzzled over just why organisms evolved aging as a strategy, and now there appears to be an answer. Allowing one individual to carry all the cellular damage inflicted over time, rather than dividing it between two organisms during reproduction, increases the chances that the individual's line will continue to reproduce for many generations to come, a new study indicates.

The earliest organisms, single-celled creatures called prokaryotes, which include bacteria, probably did not age but rather divided damaged material equally among new cells. There was not a parent cell, but rather the original cell divided into two siblings that were, in effect, the same age and shared the damage from the original cell equally.

Somewhere along the way, that strategy changed so that a parent cell retained most of the damage from aging and the offspring started with a mostly clean slate.

...

The implication is that evolution favors individuals aging as a means of allowing their lineage to persist longer.

"A lineage is more likely to survive in the long run if one individual falls on the grenade of its own cellular damage," Bergstrom said.

On it went from there.

We will understand aging in the course of defeating it, but defeat it we will, just as we are working to defeat disease and other forms of damage to the human body. The only question is whether we can engineer the support and understanding to defeat aging within our lifetimes, or not.

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Posted by Reason at March 13, 2007 7:40 PM | TrackBack (0)