Answer:
Dear
George,
In the
long run we are all dead. But the short run can be elongated in a
way that makes the long run longer.
People
are like machines: they wear out. However a machine can always be
repaired.
A
good mechanic with a stock of spare parts can keep it going indefinitely.
Managing
wear and tear may not be as complicated as it looks, all is linked
by a single word: oxidation.
A lot of oxygen is needed to power a cell and some of it goes absent
without leave.
Instead
of reacting with carbon from the sugar to form carbon dioxide, it
forms highly reactive molecules called free radicals. These go around
oxidizing—and thus damaging—other molecules, such as DNA
and proteins, which causes all sorts of trouble.
Clear
up free radicals and their kin, and you will slow down the process
of ageing. And the chemicals you use to do that are antioxidants.
Some
vitamins, such as vitamin C, are antioxidants in their own right.
This is the basis of the high-street propaganda, though there is no
evidence that consuming such antioxidants in large quantities brings
any benefit.
One way
that might let people to live 100 years is to accept the machine analogy
literally.
When
you take your car to be serviced or repaired, you expect the mechanic
to replace any worn or damaged parts with new ones. That, roughly,
is what those proposing an idea called partial immortalization are
suggesting. And they will make the new parts with stem cells.
The world
has heard much of stem cells recently. They come in several varieties,
from those found in embryos, which can turn into any sort of body
cell, to those whose destiny is constrained to becoming just one or
a few sorts of cell.
The thing
about stem cells of all types, which makes them different from ordinary
body cells, is that they have special permission to multiply indefinitely.
There
are scientific researchers who propose what is known as regenerative
medicine—using stem cells to grow replacements for tissues and
organs that have worn out. The most visionary of them contemplate
the routine renewal of the body's organs in a Lincoln's axis sort
of way.
