longevity & puberty: opinions sought

Aubrey de Grey ag24 at mole.bio.cam.ac.uk
Wed Feb 21 08:26:34 EST 2001

Jeff Liss wrote:

> I am a non-scientist writing a book and would like to hear some basic
> opinions about the possibility of genetically extended life.

Most of the detailed scientific discussion of life-extension happens
at sci.life-extension, rather than here.  If you look at Deja News in
that group you will find threads covering most of the major proposed
mechanisms and interventions.

> If a way
> could be found to retard the decay of telomeres (these are the ends of
> molecular chains the decay of which causes them to unravel?)

Close enough.

> then
> assume that a human lifetime, barring of course major illness and close
> encounters with Mack trucks, could be extended to about two hundred
> years.

This is not presently a popular view among professional biogerontologists
-- most of us think that quite a large panel of interventions would be
needed, in unison, in order to extend lifespan that much.

> Many folks stuck in a previous medical paradigm complain that
> the notion is unattractive because one would live the last 120 years
> aged and infirm.  Of course this is ridiculous because I assume the
> entire aging process would be extended, so that 100 years old would be
> a healthy middle age.

Quite right.  In fact, some biogerontologists are even more optimistic:
they think that the period of frailty at the end of life would not be
increased significantly, i.e. that the extension would be entirely of
the fully-functional period.

> My question is: under this scenario, how would puberty be affected?
> Would one grow to adulthood more slowly?   Would the transformational
> puberty years be extended?  Or do you think the body has a mission to
> grow to maturity as quickly as possible without regard to total lifespan
> -- i.e. even the pre-puberty childhood growth would remain roughly the
> same?

The simple answer is that puberty would be unaffected because the life-
extending intervention would not be administered until after puberty.

The likely scenario for the development of such a therapy is that it
would initially be developed in model organisms, most importantly mice,
and that quite a number of the panel of interventions would involve
genetic modifications, which are easy to do in the germ line (the
sperm and eggs) of mice.  This would have the potential to slow down
development (including puberty) as well as aging, and whether it would
actually do so is very hard to guess.  But, once such a therapy had
been refined in mice to the point that it was realistic and worthwhile
to try to translate it to humans -- let's say, once we had a doubling
of mouse lifespan -- you can be quite sure that there will be a clamour
of unprecedented proportions to translate it to humans who are already
alive, and especially to those who are already elderly.  We still have
a very long way to go to refine gene therapy to the point where we can
get engineered DNA into all (or nearly all) cells of whatever cell
type we choose, without any side-effects, but efforts to that end are
moving pretty fast.  So, consider the pros and cons of implementing
germ-line transformation in humans at that point.  The beneficiary of
such treatment isn't born, so if they are NOT given the treatment they
can still confidently expect a 70-year or more lifespan before they
need it.  So the question one would have to address is whether it's
likely or unlikely that, 70 years from the point at which such a 
therapy is developed in mice, it will be administerable somatically
(i.e. by gene therapy) to humans.  And it would be quite a pessimist
who would bet on that being unlikely.

The above assumes that the interventions in question would be able to
reverse age-related decline, rather than merely retard or arrest it.
But there are good reasons to suppose that they would indeed be able
to do so -- indeed, that interventions which could (even theoretically)
only retard aging will never retard it very much, so conversely that
interventions that do extend lifespan a lot will be ones that reverse
age-related molecular and cellular changes.

> I would appreciate your speculations or your direction to a discussion
> on this subject.  thanks very much.

Feel free to ask more; note, however, that you'll probably get more
response on sci.life-extension.

Aubrey de Grey

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