From: Joao Pedro (jpnitya@mail.esoterica.pt)
Date: Tue Sep 16 1997 - 02:29:13 MDT
Hi!
Anders Sandberg wrote:
> Aging is not an evolutionary disadvantage, so there is no selection
> against it. In nature few individuals even reach adult age, so from
> the persepctive of their genes it is more important to give them
> the chance to reproduce than to give them a long life. This is why
> it is possible to breed long-lived fruit flies by preventing them
> from mating until a certain age, now aging is a disadvantage and
> evolution strives to limit it.
This is a condensed version of "Why are We Allowed to Age?", an essay
written by me on the subject of evolution of aging. The full text,
hopefully, will be available next week at,
http://homepage.esoterica.pt/~jpnitya/science/why.htm
Why Are We Allowed to Age?
(...)
Is Aging a Bad Thing?
(...)
The main, natural, objective of any living creature is to
reproduce. To
survive long enough to pass on it's genes to the next
generation.
Natural selection, selects the genes that can produce the
higher numbers
of the most fit offspring whereas fitness is defined as the
capacity to
produce fit offspring.
(...)
This is roughly the explanation for the evolution of aging
given by Peter
Medawar already some time ago. Basically, although aging is,
individually,
a bad thing, there is no evolutionary pressure to spread
longer longevity
genes if no individuals reach an old age.
(...)
One question still troubled me when I found about this, in
higher animals
on top of the food chain that can have long gestation periods
and have
some, few, chances of reaching old age, wasn't aging a cause
of death?
We never witness extremely old animals in the wild because
they die
before it can happen. But many still die in consequence of
aging! In the
competitive world wild animals live, a small loss in it's
skills is usually
lethal and this loss must be done by aging in many cases.
Medawar's explanation is not, IMHO, good enough for some
species.
(...)
I used computer models to simulate the effects of an extra
longevity trait
in ancient human populations and I reached the conclusion that
it would
take hundreds of generations for this kind of traits to
implement
themselves in the gene pool.1
(...) although the good gene is not the most
common type, it will eventually spread in the population after
a certain
period of time.
(...)
It is, at least for me, an unargumentable fact that there is
evolutionary
pressure for some species to extend their lives. And we still
age...
Why do We Still Age?
One theory of why do we still age claims that in order for
higher species
like ours and other mammals to have a more complex structure,
the price
we pay is that we age. Although simplistic I enjoy this theory
but I don't
see aging as a price but as a choice, a irrational, random
choice made by
our genes millions ago.
If we look at our genotype as a computer program, we will see
that our
computer program is much more complex and detailed than the
non-aging
species computers programs. If I write a very complex computer
program, chances are it will have mistakes or bugs but if I
write a simple
one, these chances decrease.
We all started as a very simple computer program and then we
started to
become more complex, we started to have new procedures and
extensions to the program. Some programmers prefer to make
sure
everything is working fine with their work so far before
proceeding to the
next appendix but others just keep adding more and more
procedures
before completely checking the previous ones.
I think this is what happened in evolution. Some species
worked their
way to make the programs they have to work perfectly while
others,
preferred to add new extensions to their programs while the
previous
ones were not yet working fine. I see aging as a phenomenon
derived
from mistakes in our programs or, biologically, in our genes.
Non-aging
species are less complex and have successfully corrected their
mistakes
as the generation succeeded one other inexorably.
(...)
How do We Correct this Errors?
(...)
I believe there are errors much more important than others,
perhaps with
just one error corrected we can live up to a thousand years. I
don't think
this is likely because if this was the case, natural selection
would already
had made us live up to a thousand years. My opinion is that
there are
huge numbers of mistakes that cause aging.
Not only must we correct this errors but we will also have to
correct the
errors that will affect us in the future (say, after 300
years). If, with
already some evolutionary pressure being made, we only live
until a
maximum of about 120 imagine the genetic trash that exist
after 120
years! All lethal genes of retarded effect will be there, it
will be a
monumental performance.
(...)
I hope it's not too boring, I cut several parts (more than 50%).
> > Also, there are certainly lethal genes that are active when you are,
> > say, 200 years old and you will have to deal with them too with the only
> > difference being the fact than no-one even knows they exist.
>
> Yes, but as soon as we have solved that genetic problem (which may
> be hard), then the solution can be applied to all people. This is just
> a limit on how fast lifespan can be increased (and something to
> worry about for us first-generation transhumans).
>
> I think our main difference lies in optimism: you see a lot of
> problems, I see a lot of hard problems that can be solved, at least
> in principle.
I see problems waiting for a solution but try to face the problems and
not be carried away in my dreams.
Nice talking to you, sorry for the long message,
--
Hasta la vista...
"Life's too short to cry, long enough to try." - Kai Hansen
Visit my site at: http://mithlond.esoterica.pt/~jpnitya/
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