Dariusz:

>More on human past, and human gentics: I wonder, is the actual lifespan of
>human beings (or any other species, for that matter) an issue of genetics?
>(likely) If so, is it considered an "advancement/improvement" to
>genetically increase this time-period in a species (like humans)? (likely)
>If so, has our lifespan increased with the years? *If* IE is how we should
>eat (assumption), then how would our current potential lifespan compare
>with that of our instinctively-eating ancestors? Surely, they didn't live
>for 120-140 years for most of them; which seems to be the current figure
>for the human lifespan's potential.


I have recently borrowed "Reversing Human Aging", by Michael Fossel, Ph.D.,
M.D. at the local library.

It is known that most cells of our body can only divide a finite number of
times. The "clocks" are the "telomeres", i.e. the ends of the chromosomes.
Each chromosome has 2 telomeres, thus each cell has 46*2=92 clocks, all
of which have a different hour. Each time a cell divides, a new chromosome
is formed from an old one, the new telomere is slightly shorter than
the old one. Some chromosomes are thus older than others, and some
cells are older than others.

As the cell ages, expression of genes is modified. Protein turnover is
lower, thus the amount of damaged protein is higher. Mitochondrial
membranes also become more leaky, which results in a higher concentration
of free radicals inside the cell which can damage proteins and ADN. Damaged
ADN can be repaired, but when the system fails to detect it, abnormal
cells can proliferate.

When some cells age, nearby cells are affected. The entire organ is affected.
And malfunction of an organ can affect the entire body.

There are probably other aspects of aging: some cells, like neurons, never
divide, thus any damage is irreversible. We also know that the production
of some hormones (DHEA, melatonin...) decrease steadily.

No matter how much supplements of antioxydants we take (to fight
free-radical damage), the biological clocks are still ticking, and our
maximum life-span will still be about 120 years (unless sciencists
discover telomere treatments). But well before reaching that age,
the dysfunctions of the body make it more and more vulnerable to
injuries, viruses; blood supply is less efficient, arteries stiffen, etc.
Modern medicine nevertheless allows us to survive at high expense, but
certainly most of the Americans of 70+ years old wouldn't survive
without modern comfort, hygiene and health care.

Best wishes,

Jean-Louis
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