The Mitochondrial Free Radical Theory of Aging - Supernova: Pliki

CHAPTER 16
Prospective Impact on the Healthy
Human Lifespan
The message of the previous two chapters is that we have a realistic chance of achieving, in
only a few decades, a degree of control over the rate of human aging which far exceeds
anything that has hitherto seemed feasible. Since that conclusion is rather dramatic, I will use
this penultimate chapter to stand back from the technical details and critique it on various
other grounds, as well as briefly analysing some of its scientific predictions. The closing chapter
then considers a few implications of these predictions, for society at large and (more especially)
for the gerontologist; that discussion has the brevity and limited scope which is appropriate
in a book principally focused on the scientific issues, but it cannot be omitted entirely.
16.1. Plausibility of Engineered Negligible Senescence
A number of eloquent and senior gerontologists have dismissed the possibility of great
extensions of healthy lifespan on purely biological grounds, by examining what would be
necessary in order to achieve massively improved maintenance and repair of tissue. All such
arguments of which I am aware are drastically flawed. Most of the examples I critique in this
section come from a very clear and information-packed book published only four years ago
by a very prominent gerontologist; 1 they are suitable for analysis not only for that reason
but also because that book, like this, was written so as to be accessible to a wide audience.
16.1.1. Plausibility of Indefinite Maintenance
One of the commonest arguments that indefinite maintenance is impossible appeals to
an analogy between the human body and man-made machines. An example is that the
heart is a pump, with many similarities to man-made pumps, albeit with somewhat better
efficiency, durability and reliability than any which man has built so far. From this is inferred
that, once it does finally begin to lose functionality, the heart can only be kept “on the road”
by being overhauled in the same sort of way as a man-made pump. In particular, it would
have to be stopped for the duration of that overhaul, and a backup pump substituted. In the
specific case of the heart it is unclear how this can be considered a remotely conclusive
argument against the feasibility of such maintenance, since exactly that substitution is already
done during heart transplants. But there is a much more fundamental flaw in it, which
applies equally to any organ, irrespective of our ability to overhaul it by invasive surgery:
namely, that it is over-anthropomorphic with regard to scale. It is indeed clear that an engineer
cannot overhaul a heart-sized, man-made pump, with a spanner and screwdriver, without
first stopping it. But if the pump were the size of St. Paul’s Cathedral, while nevertheless
built entirely from independently replaceable components that were all the size of bolts and
screws, then the only problem that the engineer would have in performing the overhaul
while the pump remained in operation would be with the G-forces. And that—in fact, a
The Mitochondrial Free Radical Theory of Aging, by Aubrey D.N.J. de Grey.
©1999 R.G. Landes Company.