From a scientist's prospective it's going
to be rather different from that of most religious
traditions, which holds that we die because
this is only a temporary staging area before
we go to the big show the next stage in which
we go to heaven or hell or wherever some kind
of afterlife.
For scientists the question has a rather different
answer and it has to do with the kinds of
causes we look for in science.
So you have proximate causes versus ultimate
causes.
For example, why does sugar taste sweet or
why does fruit taste sweet something like
that?
You would say well because there's molecular
receptors on your tongue that are geared toward
sending signals to a certain part of the brain
that register sweetness and pleasure and so
on with fruit.
That's approximate answer.
And ultimate answer is because foods that
taste sweet are more likely to be consumed
and those in our natural environment are the
kinds of foods that are both rare and nutritious
and so the more of them you eat the better
and we evolved that tendency.
To answer the question why we die, it's the
same kind of thing.
Approximate answers include cancer, heart
disease, arthrosclerosis.
The ultimate answer though is found in two
principles of nature, that is the second law
of thermodynamics or entropy, which means
everything runs down, including our bodies.
And the whole universe, the whole universe
runs down so ultimately even if you could
double your lifespan, triple it, live essentially
forever you can't really because the universe
will eventually die in a heat death.
And then second is the principle of natural
selection that drives evolution.
And it has to do with a cost benefit analysis
of how many limited resources you put into
organisms.
So obviously natural selection is going to
select for infants and toddlers and babies
to be well cared for, have super regenerative
powers to keep their bodies going in order
to get the genes into the next generation,
get them up to reproductive age and so on.
So we see cells that divide very rapidly in
infants and babies.
A little cut you could practically watch it
heal.
It's incredible.
Whereas someone my age when I get cut it takes
much longer to heal.
And so the question is why wouldn't evolution
just make it so that I, now in my early 60s,
can't just keep going to 200/300?
And the answer is there's no reason for it.
Because after I've brought my own offspring
into reproductive age and then they've brought
their offspring into reproductive age I'm
really of no use anymore.
I can serve a useful purpose as a parent,
of course, bringing my genes up and then useful
purpose as a grandparent to help my offspring
bring their offspring up to reproductive age,
but beyond that really there's no sense in
pouring any more resources into great, great,
great, great, great grandparents because the
genes in the little infant are already going
to be well taken care of.
So it's sort of a weird way to think about
it, but in a way nature operates because of
entropy.
Nature has to select and choose in kind of
a triage where are we going to put the resources.
I'm saying it like there's somebody up there
allocating resources, the government is doling
out checks to organisms.
No, there is nothing like that, of course,
this is just how natural selection operates.
So in short, we die so that our future generations
may live because there are limited resources.
