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Are we born to die?
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For millennia, we've tried
to outsmart our own mortality...
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Only to find that death
is the greatest certainty.
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But for the first time
in history,
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that may be about to change.
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Science is unraveling
the mysteries of aging,
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discovering an animal
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that comes back from the dead,
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and turning our quest
for eternal life on its head.
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Are we about to enter
the age of immortality?
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Or is death necessary
for the survival of our species?
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Can we cheat death?
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Space, time, life itself.
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The secrets of the cosmos
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lie through the wormhole.
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Captions by vitac...
www.Vitac.Com
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captions paid for by
discovery communications
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when will I die?
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It's a question
I've asked myself.
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I'm sure you've thought
about it, too.
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From the day we are born,
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the clock of our lives marks
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our inevitable decline...
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Ticking inexorably
toward our final hour.
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Medical science has made
incredible advances
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in prolonging life.
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For most of human history,
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people were lucky
to survive into their 40s.
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Now, people often break 100.
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The oldest person we know of
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lived to celebrate
her 122nd birthday.
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And as we probe deeper into
the fundamental biology of life,
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we are now questioning
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whether death really has
to come at all,
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whether we can... Stop the clock
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David Sinclair likes
to live in the fast Lane.
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But he knows our bodies,
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like cars, can't push
the needle forever.
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Well, I've been interested
in studying aging
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since I can remember.
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I think it was
around the age of 4
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when I realized that my parents
would one day die,
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and I would, too,
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and that seemed
extremely tragic.
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And I also thought
that if we could figure out
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why we age
and what we could do about it,
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that would have a really big
beneficial impact on the world.
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David spends a lot of time
thinking about old age.
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But he's interested in more
than the wrinkles on our skin.
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As a professor of genetics
at Harvard,
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he asks what role
our genes play in aging.
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An aging body is a lot
like a rusty old car.
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Rust, or oxidation,
is what causes everything,
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including our DNA,
to break down.
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David believes
we may soon be able
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to repair our failing bodies
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as easily as a mechanic can
spruce up a rusty body panel.
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David's research focuses
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on our body's own set
of repair mechanics...
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A group of genes
called sirtuins.
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As our bodies age,
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they accumulate
old or senescent cells.
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And longevity genes prevent
those cells from accumulating.
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This would be similar,
in an old car,
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to the mechanics removing
rusty old parts
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and replacing them
with new ones.
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But these repair genes
begin to fall silent
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as we pass our 30s and 40s.
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So if we could find a way
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of getting these longevity genes
working harder,
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this would be a way
to keep our bodies healthier
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and working for longer.
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If our cells have
the tools to restore
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and rebuild themselves, why
can't they do that forever...
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In other words, stop aging?
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Sinclair has dedicated
his career
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to finding ways to help
our repair mechanisms
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keep going well past middle age.
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It's driven him deep into
the inner mechanics of the cell.
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In order for a human cell
to function,
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it requires close collaboration
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between two distinct parts...
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The nucleus,
the cell's control center,
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and its tiny power engines
called mitochondria.
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Every task a cell performs
relies on precise communication
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between these two.
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Imagine this kitchen
is a young cell.
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Inside it are the nucleus
and mitochondria,
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two chefs working in concert.
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Our genes are
just like a recipe book.
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In a young cell, the nucleus
and the mitochondria,
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they're reading
the recipe perfectly,
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and they're really
working well together.
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A delicious meal
is taking shape.
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But over time, the communication
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and coordination
between the chefs gets worse.
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In an old cell, the nucleus
and the mitochondria,
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they're throwing in things
that don't belong.
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They're leaving things out.
They don't communicate well.
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One chef might be trying
to pass a spoon to the other,
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and the other one is
not paying attention.
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It's as if the chefs
are spilling on the recipe book
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and losing that ability
to read it.
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DNA is the recipe of life.
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But over time,
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wear and tear makes
the recipe hard to read,
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and our cells lose the ability
to prepare the meal.
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Whether it's damage
or changes in the environment,
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the cell eventually loses
the memory
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of which genes should be on
and which genes should be off,
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and that, we think,
causes aging.
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David has been combing
through aging cells,
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trying to see if he can identify
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which vital ingredient
they lack.
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And now he thinks
he's found the molecule
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that will get our cellular
kitchen back on track.
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It's called N.A.D.
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It's a molecule
that's essential for life.
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Without it, you'd be dead
in about 20 seconds.
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And, as we age,
the levels of this molecule
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go down steadily to the point
where you have
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about half the levels
of what you once had.
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David wondered if there
was a way to restore N.A.D.
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To more youthful levels.
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He injected mice
with a special compound
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that boosts production of N.A.D.
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The effects were dramatic.
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This mouse is
very youthful and energetic.
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You can see the ears are still
nice and young-looking,
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and the fur isn't turning gray.
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As you can see here,
this mouse is going gray.
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She's losing hair.
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Her ears are getting wrinkled.
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Her spine is starting to bend.
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Well, what's amazing
about these mice
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is that they were born
on the same day.
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What we saw was
a rapid-aging reversal
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in their muscles,
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from a mouse that's equivalent
to a 60-year-old human
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back to a 20-year-old.
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If we could apply this
to humans,
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imagine what a city street
might look like
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50 years from now.
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Almost everyone
would appear youthful,
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free of the illness
and frailties of age.
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David's research
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may one day slow down and
even reverse aging in people.
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We're not talking here
about being older for longer.
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It's quite the opposite.
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It's about being
younger for longer.
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But David's work only
treats the symptoms of aging.
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It doesn't attack
the root of the problem...
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The gradual decay of our DNA.
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Japanese scientist Shin Kubota
thinks we can turn that tide.
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My dream is to live
with my families
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of different generations
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so that we can enjoy
our great-great grandchildren.
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The sea is where all life began,
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and with every empty shell
it leaves behind,
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it seems to prove
that all lives must end.
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But shin knows otherwise.
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Shin studies
a tiny marine animal
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called Turritopsis Dohrnii,
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or the immortal jellyfish.
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This creature has figured out
how to cheat death.
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At shin's lab
in the town of Shirahama
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is the world's
only captive population
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of immortal animals.
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First discovered
in the Mediterranean in 1988,
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this jellyfish is no bigger
than your fingernail.
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Immortal jellyfish is
very cute, small jellyfish.
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Diameter is
about several millimeter.
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But after showing
these creatures
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such tender, loving care,
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shin does the unthinkable.
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He chops them into pieces.
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Try to kill this jellyfish,
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you will be surprised.
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A remarkable thing happens.
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The jellyfish does not die
beneath shin's hand.
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Instead, it seems to be reborn.
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The bell reabsorbs the tentacles
and becomes a gelatinous blob.
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I call this stage the meatball.
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The meatball becomes a polyp,
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and soon it matures
into an adult jellyfish.
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The jellyfish shows
very remarkable transformation.
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The jellyfish's secret
is a process called
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cellular transdifferentiation.
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The cells in any fragment
of the animal
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can figure out
what body parts are missing,
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then retrofit themselves
to grow back the entire body.
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If we could determine
how do the jellyfish rejuvenate,
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we could borrow its techniques.
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Imagine shin were attacked
by a mutant sea monster.
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It's Japan, after all,
so it's not such a crazy idea.
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If the only thing left of shin
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were the tip
of one little finger...
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Transdifferentiation could
turn those finger cells
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into brain cells,
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heart cells, muscle cells.
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Shin would come back
from the dead.
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It seems like science fiction,
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but jellyfish and humans
have surprisingly similar genes.
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If a jellyfish can
learn this trick,
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perhaps we can, as well.
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From the ruins
of a single animal,
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hundreds of identical jellyfish
have sprouted.
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It's a feat unequaled in nature,
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but perhaps not for long.
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If we could unlock the genetic
secrets of this jellyfish,
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we could regenerate
aging organs,
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perhaps even entire bodies.
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I believe, one day,
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that humans can become immortal
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using the same process
as a jellyfish.
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The promise of immortality
always seemed a fantasy,
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but the infinite regeneration
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of the jellyfish
is biological reality.
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So can we get there
with our biology?
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Some people believe we will,
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and sooner than you think.
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Death has always been
a fact of life.
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Why?
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Because our bodies wear down.
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Our hearts won't beat forever.
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Our muscles gradually weaken.
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Our brains lose their edge.
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But it doesn't have
to be that way.
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Our bodies have
built-in technology
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to repair themselves...
Stem cells.
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These cells have the potential
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to replenish any organ
in the body
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if we can coax them
into doing it.
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Cell biologist Larry Goldstein
thinks that if we want
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to extend our life-spans,
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we'll have to leap past
a major obstacle...
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The slow decline of our minds.
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I had the unfortunate experience
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of helping to care for my mother
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when she developed
Alzheimer's disease
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in her late 60s.
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It was a terrible experience,
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and I hate the idea
of anybody else
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having to go through that
with their family members
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and their loved ones.
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50% of us will develop
Alzheimer's disease
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by the time we're 85 years old.
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It does no good to age to 85
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and be physically healthy
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if your brain doesn't function.
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At the Sanford consortium
of regenerative medicine,
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Larry keeps an hourglass
on his desk.
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It reminds him of all the people
who are running out of time.
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But Larry thinks
he's found the key
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to fighting
debilitating diseases of aging
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like Alzheimer's... Stem cells.
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The problem is that
we don't really understand
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what goes wrong in brain cells
that have the disease.
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00:13:46,470 --> 00:13:49,240
And we're using stem cells
to try to tackle that problem
263
00:13:49,240 --> 00:13:50,640
in a unique way.
264
00:13:50,640 --> 00:13:54,810
Stem cells are the body's
original building blocks.
265
00:13:54,810 --> 00:13:58,610
They have the potential
to become any type of cell.
266
00:14:01,550 --> 00:14:05,250
In the primordial furnace
of the womb,
267
00:14:05,250 --> 00:14:07,490
our bodies use
these raw materials
268
00:14:07,490 --> 00:14:09,690
much like a master glassblower,
269
00:14:09,690 --> 00:14:12,930
sculpting beautifully intricate,
finished organs
270
00:14:12,930 --> 00:14:15,760
from shapeless, raw ingredients.
271
00:14:15,760 --> 00:14:17,730
You can think about stem cells
272
00:14:17,730 --> 00:14:20,830
as being like
biological raw material,
273
00:14:20,840 --> 00:14:24,140
just like these glass pellets
are the raw material
274
00:14:24,140 --> 00:14:27,010
that you can throw
into a really hot oven
275
00:14:27,010 --> 00:14:29,840
and use to make anything at all
that you'd like to make.
276
00:14:29,840 --> 00:14:32,680
So, let's see how this works.
277
00:14:32,680 --> 00:14:36,250
In you go. Ooh, that's hot.
278
00:14:36,250 --> 00:14:38,750
As we grow from an embryo,
279
00:14:38,750 --> 00:14:41,450
our bodies prepare
and shape stem cells
280
00:14:41,460 --> 00:14:45,220
for the adult roles
they will need to fill.
282
00:14:45,230 --> 00:14:49,960
Each stem cell decides
what adult cell type to become
283
00:14:49,960 --> 00:14:53,330
based on cues
from the cells around it.
284
00:14:53,330 --> 00:14:54,730
Stem cells respond
285
00:14:54,740 --> 00:14:57,270
to biochemical signals
from other cells.
286
00:14:57,270 --> 00:15:00,240
And so a heart cell started out
as a stem cell,
287
00:15:00,240 --> 00:15:02,940
and it got instructions
to become a heart cell.
288
00:15:02,940 --> 00:15:04,640
You can imagine
putting a heart together
289
00:15:04,650 --> 00:15:06,110
with different vessel cells
290
00:15:06,110 --> 00:15:07,510
or different muscle cells.
291
00:15:07,520 --> 00:15:10,720
A great glassblower can put all
these different shapes together
292
00:15:10,720 --> 00:15:13,390
to make something
beautiful at the end.
293
00:15:13,390 --> 00:15:15,960
- Cool enough to touch.
- Amazing.
294
00:15:15,960 --> 00:15:18,020
It's incredible, really,
when you think about it.
295
00:15:18,030 --> 00:15:21,260
Millions and millions
of stem cells get together,
296
00:15:21,260 --> 00:15:24,530
respond to the right sorts
of biochemical signals,
297
00:15:24,530 --> 00:15:28,230
and make this heart.
298
00:15:28,240 --> 00:15:31,800
The power of stem cells
to create organs from scratch
299
00:15:31,810 --> 00:15:35,810
has drawn the interest
of scientists for decades.
300
00:15:35,810 --> 00:15:38,780
The goal is
to harness this resource
301
00:15:38,780 --> 00:15:42,680
to rebuild and replace
failing tissue.
302
00:15:42,680 --> 00:15:44,780
But there's a problem...
303
00:15:44,790 --> 00:15:46,920
By the time we're fully grown,
304
00:15:46,920 --> 00:15:51,060
we've exhausted our supply
of embryonic stem cells,
305
00:15:51,060 --> 00:15:53,960
and the few stem cells
we have left
306
00:15:53,960 --> 00:15:56,030
are not nearly as flexible.
307
00:15:56,030 --> 00:15:58,060
There are so-called
adult stem cells,
308
00:15:58,070 --> 00:15:59,900
which are partially formed.
309
00:15:59,900 --> 00:16:04,540
They're committed to make one
of the types of adult tissues.
310
00:16:04,540 --> 00:16:06,640
Skin stem cells make skin.
311
00:16:06,640 --> 00:16:08,940
Brain stem cells
make brain tissues.
312
00:16:08,940 --> 00:16:10,440
But the important point
313
00:16:10,450 --> 00:16:12,280
is that
it's partially committed.
314
00:16:12,280 --> 00:16:14,550
It has part of a shape
that commits it
315
00:16:14,550 --> 00:16:18,220
to do some things
and not others.
316
00:16:18,220 --> 00:16:20,550
Only embryonic stem cells
317
00:16:20,560 --> 00:16:24,220
have the flexibility
to become any cell in the body.
318
00:16:24,230 --> 00:16:26,730
But harvesting them
from embryonic tissue
319
00:16:26,730 --> 00:16:30,500
has proved politically
controversial.
320
00:16:30,500 --> 00:16:32,700
Then, in 2006,
321
00:16:32,700 --> 00:16:35,900
scientists made
a stunning discovery.
322
00:16:35,900 --> 00:16:40,970
Adult stem cells can be recycled
back to embryonic form
323
00:16:40,980 --> 00:16:45,010
by modifying
just four of their genes.
324
00:16:45,010 --> 00:16:49,880
They become what are called
induced pluripotent stem cells,
325
00:16:49,880 --> 00:16:53,020
or IPS cells.
326
00:16:53,020 --> 00:16:55,120
So the discovery of IPS cell
327
00:16:55,120 --> 00:16:57,120
was like the shot heard
'round the world.
328
00:16:57,130 --> 00:17:00,330
It was a true revolution
in our understanding
329
00:17:00,330 --> 00:17:03,200
of what cells could do,
330
00:17:03,200 --> 00:17:05,660
and how simply it could be done.
331
00:17:05,670 --> 00:17:08,430
Like throwing glass
back into the furnace,
332
00:17:08,440 --> 00:17:11,940
we can now restore cells
to their embryonic state
333
00:17:11,940 --> 00:17:13,570
and create raw materials
334
00:17:13,570 --> 00:17:16,710
we could use
to stay eternally young.
335
00:17:16,710 --> 00:17:19,040
You could make this
into brain cells,
336
00:17:19,050 --> 00:17:21,780
or heart cells, or skin cells,
or what have you.
337
00:17:21,780 --> 00:17:25,580
We've used genetic trickery
to take, for example,
338
00:17:25,590 --> 00:17:27,990
a skin cell from my arm,
339
00:17:27,990 --> 00:17:30,090
trick it using genetic elements
340
00:17:30,090 --> 00:17:31,490
into becoming a cell
341
00:17:31,490 --> 00:17:36,800
like an embryonic stem cell
in its abilities.
342
00:17:36,800 --> 00:17:39,630
Larry is now using
these rebooted cells
343
00:17:39,630 --> 00:17:43,340
to uncover what goes wrong
in Alzheimer's.
344
00:17:43,340 --> 00:17:46,710
He starts with skin cells
of people with the disease
345
00:17:46,710 --> 00:17:49,880
and changes them
into brain cells.
346
00:17:49,880 --> 00:17:53,080
Then, he can study exactly
what's going wrong
347
00:17:53,080 --> 00:17:57,750
in those cells and develop
new drugs to treat them.
348
00:17:57,750 --> 00:18:00,350
Right now, we have zero drugs
349
00:18:00,350 --> 00:18:02,890
that alter the course
of Alzheimer's disease.
350
00:18:02,890 --> 00:18:06,830
I do know that if we want
to make it past 85 or 90
351
00:18:06,830 --> 00:18:08,760
on a regular basis,
352
00:18:08,760 --> 00:18:10,830
we're going to have
to solve the problem.
353
00:18:10,830 --> 00:18:13,370
Larry hopes
his work on Alzheimer's is
354
00:18:13,370 --> 00:18:15,400
the beginning
of something bigger.
355
00:18:15,400 --> 00:18:17,840
He thinks if we stored
our stem cells
356
00:18:17,840 --> 00:18:19,810
while we're young and healthy,
357
00:18:19,810 --> 00:18:23,640
we could use them later
to replace our aging organs.
358
00:18:23,640 --> 00:18:25,610
It's incredible really
when you think about it...
359
00:18:25,610 --> 00:18:27,750
The ability
to someday build an organ
360
00:18:27,750 --> 00:18:31,650
from stem cells like this
will be a huge breakthrough.
361
00:18:31,650 --> 00:18:33,650
In the future, we may be able
362
00:18:33,650 --> 00:18:36,490
to extend our lives
by recreating
363
00:18:36,490 --> 00:18:39,530
our failing hearts, lungs,
and kidneys.
364
00:18:39,530 --> 00:18:43,600
But what happens to our society
when people live longer?
365
00:18:43,600 --> 00:18:46,930
Are we turning nature's plan
upside down?
366
00:18:46,930 --> 00:18:48,770
One scientist
has simulated a world
367
00:18:48,770 --> 00:18:51,370
where no one dies of old age,
368
00:18:51,370 --> 00:18:54,170
and he's reached
a startling conclusion.
369
00:18:57,100 --> 00:19:00,340
If our organs have
the power to regenerate,
370
00:19:00,340 --> 00:19:04,110
why do they allow us
to age and die?
371
00:19:04,110 --> 00:19:10,280
Plants, bugs, animals...
It happens to us all.
372
00:19:10,280 --> 00:19:11,550
Perhaps it's because
373
00:19:11,550 --> 00:19:15,220
death is programmed into us
by evolution.
374
00:19:15,220 --> 00:19:19,960
Old animals must die
to free up space for the young.
375
00:19:19,960 --> 00:19:23,490
So, if we cheat death,
376
00:19:23,500 --> 00:19:26,660
if we regenerate
the sweetness of youth...
377
00:19:30,970 --> 00:19:34,500
Will evolution end?
378
00:19:34,510 --> 00:19:37,240
It's taken humans
more than 1,000 years
379
00:19:37,240 --> 00:19:41,080
and many lifetimes
to master the game of chess.
380
00:19:41,080 --> 00:19:44,180
That's a puzzle for Brazilian
evolutionary biologist
381
00:19:44,180 --> 00:19:45,680
André Martins.
382
00:19:45,680 --> 00:19:48,250
Wouldn't it be better
if one person
383
00:19:48,250 --> 00:19:50,250
could live long enough
to acquire
384
00:19:50,260 --> 00:19:53,360
that mastery all
by him or herself?
385
00:19:53,360 --> 00:19:55,790
For quite a while,
scientists thought
386
00:19:55,790 --> 00:19:59,160
that evolution could
not explain aging.
387
00:19:59,160 --> 00:20:03,400
When someone die, in average,
they will leave less children,
388
00:20:03,400 --> 00:20:05,100
and that's a clear disadvantage
389
00:20:05,100 --> 00:20:08,470
from the evolutionary
point of view.
390
00:20:08,470 --> 00:20:10,510
Evolution is supposed to favor
391
00:20:10,510 --> 00:20:13,810
the individuals
best adapted for survival.
392
00:20:13,810 --> 00:20:17,280
So why doesn't it let us
survive forever?
393
00:20:17,280 --> 00:20:21,020
Why are we denied
the ultimate adaptation?
394
00:20:21,020 --> 00:20:23,090
André created
a computer simulation
395
00:20:23,090 --> 00:20:24,720
to find out.
396
00:20:24,720 --> 00:20:29,090
I have always find the evolution
problem fascinating.
397
00:20:29,090 --> 00:20:33,000
I thought it could explain
not how but why we age.
398
00:20:33,000 --> 00:20:35,130
André' simulation uses
game theory,
399
00:20:35,130 --> 00:20:38,170
the math of competitive
situations.
400
00:20:38,170 --> 00:20:39,670
He thought he could find out
401
00:20:39,670 --> 00:20:42,640
whether dying
actually serves a purpose
402
00:20:42,640 --> 00:20:44,910
by staging a competition.
403
00:20:44,910 --> 00:20:49,350
So, what the computer model
does is simulate the competition
404
00:20:49,350 --> 00:20:51,980
between mortals and immortals.
405
00:20:51,980 --> 00:20:55,420
When you see blue, it means
that that region of space,
406
00:20:55,420 --> 00:20:57,490
there is a mortal living there.
407
00:20:57,490 --> 00:21:00,990
And if it's red, there is
an immortal living there.
408
00:21:00,990 --> 00:21:02,360
They fill out every space
409
00:21:02,360 --> 00:21:08,000
and they start competing
for the limited resources there.
410
00:21:08,000 --> 00:21:10,930
To picture André' simulation,
411
00:21:10,940 --> 00:21:13,140
imagine a head-to-head contest
412
00:21:13,140 --> 00:21:16,840
between two very different
soccer teams.
413
00:21:16,840 --> 00:21:21,540
The immortal players, in red,
do not wear out with time.
414
00:21:21,550 --> 00:21:23,750
But the mortals, in blue,
415
00:21:23,750 --> 00:21:27,450
will eventually become
too tired to play.
416
00:21:27,450 --> 00:21:29,750
By pitting the two
against each other
417
00:21:29,750 --> 00:21:33,220
in a game lasting
many generations,
418
00:21:33,220 --> 00:21:34,660
André thought he could find out
419
00:21:34,660 --> 00:21:38,260
just how much advantage
immortality conveys.
420
00:21:38,260 --> 00:21:40,160
Every time I run the simulation,
421
00:21:40,170 --> 00:21:41,630
the same thing happens.
422
00:21:41,630 --> 00:21:45,100
The advantage of not dying
makes a huge difference,
423
00:21:45,100 --> 00:21:48,610
and the immortals start winning.
424
00:21:48,610 --> 00:21:52,440
Like soccer,
life is a competitive struggle.
425
00:21:52,440 --> 00:21:57,010
If you compete more effectively,
you control the game.
426
00:21:57,020 --> 00:22:01,080
But André' simulation contains
another life-like factor...
427
00:22:01,090 --> 00:22:03,690
Environmental change.
428
00:22:03,690 --> 00:22:05,320
Just like in the real world,
429
00:22:05,320 --> 00:22:10,230
André' virtual players face
constantly shifting conditions,
430
00:22:10,230 --> 00:22:16,400
like new diseases, predators,
432
00:22:16,400 --> 00:22:18,230
and climate change.
433
00:22:18,240 --> 00:22:22,540
While immortals can
struggle through them,
434
00:22:22,540 --> 00:22:24,940
not all mortals make it.
435
00:22:24,940 --> 00:22:26,340
However, when they die,
436
00:22:26,340 --> 00:22:30,850
they are replaced
with younger, stronger players.
437
00:22:30,850 --> 00:22:32,380
In any evolutionary process,
438
00:22:32,380 --> 00:22:34,550
if you are mutating
and adapting,
439
00:22:34,550 --> 00:22:37,350
the new generations will be
slightly better than older ones
440
00:22:37,360 --> 00:22:41,120
because they are
the ones that survive.
441
00:22:41,130 --> 00:22:43,960
Since the mortals can evolve,
442
00:22:43,960 --> 00:22:46,530
this gives them an advantage
443
00:22:46,530 --> 00:22:50,600
that allow us then
to get back in the field.
444
00:22:50,600 --> 00:22:52,970
In evolution,
each new generation
445
00:22:52,970 --> 00:22:55,610
has some tricks
the last one didn't.
446
00:22:55,610 --> 00:22:57,640
And the faster
you get them on the field,
447
00:22:57,640 --> 00:23:00,580
the faster the species improves.
448
00:23:00,580 --> 00:23:04,050
The impact,
after many generations,
449
00:23:04,050 --> 00:23:05,850
is huge.
450
00:23:06,420 --> 00:23:09,750
First, there is
no advantage for any side.
451
00:23:09,750 --> 00:23:14,290
And then, slowly
the blue mortals start winning.
452
00:23:14,290 --> 00:23:17,060
And after a while,
they can actually drive
453
00:23:17,060 --> 00:23:21,030
the red team, the immortals,
to extinction.
454
00:23:21,030 --> 00:23:24,900
In the end,
the mortal population wins
455
00:23:24,900 --> 00:23:27,570
because the immortals
can't adapt.
456
00:23:27,570 --> 00:23:28,740
They're doomed.
457
00:23:28,740 --> 00:23:33,280
This suggests that aging
has a biological goal.
458
00:23:36,380 --> 00:23:39,780
André believes, to keep pace
with a changing world,
459
00:23:39,780 --> 00:23:43,850
we need new generations
with new adaptations.
460
00:23:43,860 --> 00:23:45,590
And we must make room for them,
461
00:23:45,590 --> 00:23:48,930
which makes mortality necessary.
462
00:23:48,930 --> 00:23:52,900
The mortal can drive
the immortals to extinction.
463
00:23:52,900 --> 00:23:55,470
It was much easier
than what I was expecting.
464
00:23:55,470 --> 00:23:58,000
From evolutionary point of view
for the species,
465
00:23:58,000 --> 00:23:59,470
it is a good thing to die.
466
00:23:59,470 --> 00:24:00,940
Yeah!
467
00:24:00,940 --> 00:24:03,300
From a personal point of view,
it's not a good thing at all.
468
00:24:05,910 --> 00:24:10,710
We owe our very existence
to the wonders of evolution,
469
00:24:10,720 --> 00:24:14,520
even though it has designed us
to get out of the way.
470
00:24:14,520 --> 00:24:18,090
But what if we could sidestep
natural evolution,
471
00:24:18,090 --> 00:24:21,860
manipulate the genes
that make us die?
472
00:24:21,860 --> 00:24:27,000
Could we evolve ourselves
to live forever?
473
00:24:29,680 --> 00:24:32,280
At the core of every living cell
474
00:24:32,280 --> 00:24:36,780
is a single
fabulously complex molecule...
475
00:24:36,780 --> 00:24:38,550
DNA.
476
00:24:38,550 --> 00:24:42,250
Its genetic code
is the source of life.
477
00:24:42,260 --> 00:24:45,990
But DNA is also
the reason we die.
478
00:24:45,990 --> 00:24:50,130
As we age, our DNA code
gets slowly jumbled,
479
00:24:50,130 --> 00:24:53,430
until it can no longer
keep us alive.
480
00:24:53,430 --> 00:24:56,100
If we can undo those mistakes,
481
00:24:56,100 --> 00:25:00,270
we can stop death's shadow
from creeping up on us.
482
00:25:05,850 --> 00:25:08,610
Professor Jennifer Doudna thinks
we're on the brink
483
00:25:08,620 --> 00:25:12,780
of being able to fix
all the errors in our DNA
484
00:25:12,790 --> 00:25:16,420
and make ourselves
immune to disease and decay.
485
00:25:16,420 --> 00:25:20,190
It's been an amazing decade
or more in science
486
00:25:20,190 --> 00:25:23,090
when it's been possible
to sequence
487
00:25:23,100 --> 00:25:25,300
not only the entire human genome
488
00:25:25,300 --> 00:25:27,400
but now many human genomes.
489
00:25:27,400 --> 00:25:30,140
And what's really on the horizon
490
00:25:30,140 --> 00:25:34,440
is the opportunity
to rewrite that information.
491
00:25:34,440 --> 00:25:36,740
Over the past few years,
Jennifer has developed
492
00:25:36,740 --> 00:25:39,740
a revolutionary
DNA-editing technique
493
00:25:39,750 --> 00:25:43,480
which has turned the dream
of modifying our genes
494
00:25:43,480 --> 00:25:45,350
into practical reality.
495
00:25:45,350 --> 00:25:48,390
What's exciting right now
is that we have a chance
496
00:25:48,390 --> 00:25:52,060
to make changes to the DNA
497
00:25:52,060 --> 00:25:54,090
at the level of a single letter
498
00:25:54,090 --> 00:25:56,900
in the more
than 3 billion letters
499
00:25:56,900 --> 00:25:58,230
in the human cell.
500
00:25:58,230 --> 00:26:00,130
So this is a wonderful moment,
501
00:26:00,130 --> 00:26:02,800
when a technology
has become available
502
00:26:02,800 --> 00:26:07,370
for that kind of precision
genome engineering.
503
00:26:09,610 --> 00:26:12,040
In the past,
DNA editing has been
504
00:26:12,050 --> 00:26:15,010
a crude, hit-and-miss affair.
505
00:26:15,020 --> 00:26:17,180
Imagine trying to fix
a pair of eyeglasses
506
00:26:17,180 --> 00:26:19,320
without being able to see them
507
00:26:19,320 --> 00:26:23,120
and with tools that are
far too big for the job.
508
00:26:23,120 --> 00:26:26,860
We didn't dare
to edit human genes that way.
509
00:26:26,860 --> 00:26:28,730
But Jennifer
and her collaborator,
510
00:26:28,730 --> 00:26:31,930
Emmanuelle Charpentier,
have developed a new,
511
00:26:31,930 --> 00:26:33,600
far more precise tool
512
00:26:33,600 --> 00:26:37,140
that makes DNA surgery
not only possible,
513
00:26:37,140 --> 00:26:39,040
but easy.
514
00:26:39,040 --> 00:26:41,210
It's called CRISPR,
515
00:26:41,210 --> 00:26:43,510
and it places
almost god-like powers
516
00:26:43,510 --> 00:26:46,480
in the hands of humanity.
517
00:26:46,480 --> 00:26:48,210
Like many scientific wonders,
518
00:26:48,220 --> 00:26:51,780
CRISPR was pioneered
by nature herself
519
00:26:51,790 --> 00:26:54,320
inside bacteria.
520
00:26:54,320 --> 00:26:58,320
We began our project
with the goal of understanding
521
00:26:58,330 --> 00:27:01,490
how bacteria fight
viral infection.
522
00:27:01,500 --> 00:27:05,430
But we recognized
that molecules involved
523
00:27:05,430 --> 00:27:07,970
in those processes in bacteria
524
00:27:07,970 --> 00:27:10,570
could be harnessed
as a technology
525
00:27:10,570 --> 00:27:14,040
for rewriting the DNA in cells.
526
00:27:17,280 --> 00:27:19,810
You could think
about the DNA of a bacterium
527
00:27:19,810 --> 00:27:21,210
as a house
528
00:27:21,210 --> 00:27:24,820
and the invading viral DNA
as a burglar.
529
00:27:26,250 --> 00:27:28,250
Jennifer
and Emmanuelle discovered
530
00:27:28,260 --> 00:27:31,720
that bacteria have a built-in
surveillance system.
531
00:27:31,730 --> 00:27:33,830
They can't prevent
the first attack...
532
00:27:33,830 --> 00:27:36,090
But a system called CRISPR
533
00:27:36,100 --> 00:27:39,600
takes a precise snapshot
of the viral DNA,
534
00:27:39,600 --> 00:27:41,870
the same way
a security camera captures
535
00:27:41,870 --> 00:27:44,540
a picture of a burglar.
536
00:27:44,540 --> 00:27:46,140
In a real bacterial cell,
537
00:27:46,140 --> 00:27:48,770
the CRISPR sequence is the way
538
00:27:48,780 --> 00:27:53,040
that the cell records images
in the form of DNA
539
00:27:53,050 --> 00:27:55,510
that represent foreign invaders
540
00:27:55,520 --> 00:27:57,720
and keep it for future reference
541
00:27:57,720 --> 00:28:00,150
to protect the cell
from those same invaders.
542
00:28:03,260 --> 00:28:06,190
When the intruder
shows up a second time,
543
00:28:06,190 --> 00:28:08,730
the bacterial cell
recognizes the invader
544
00:28:08,730 --> 00:28:11,000
from stored surveillance images
545
00:28:11,000 --> 00:28:12,730
and calls the cops.
546
00:28:12,730 --> 00:28:18,270
In the bacterial cell,
those cops are the enzyme cas9.
547
00:28:18,270 --> 00:28:21,040
So when the house
pulls out a picture
548
00:28:21,040 --> 00:28:22,870
from the surveillance camera...
549
00:28:22,880 --> 00:28:26,880
And identifies
a potential invader,
550
00:28:26,880 --> 00:28:31,220
that's the CRISPR system
using the enzyme cas9
551
00:28:31,220 --> 00:28:36,620
to find and destroy foreign DNA.
552
00:28:36,620 --> 00:28:39,760
The cas9 molecule acts
like a pair of scissors
553
00:28:39,760 --> 00:28:41,630
precisely guided by CRISPR
554
00:28:41,630 --> 00:28:45,230
to a matching site
on the virus' DNA.
555
00:28:45,230 --> 00:28:47,870
It then cuts the DNA
in that spot,
556
00:28:47,870 --> 00:28:51,240
destroying the virus'
ability to reproduce.
557
00:28:51,240 --> 00:28:55,870
The threat to the bacterium
is eliminated.
558
00:28:55,880 --> 00:28:57,310
But Jennifer realized
559
00:28:57,310 --> 00:28:59,180
she could adapt
this natural mechanism
560
00:28:59,180 --> 00:29:02,310
into a pinpoint method
for gene editing,
561
00:29:02,320 --> 00:29:06,950
accurate down to
a single letter of DNA.
562
00:29:06,950 --> 00:29:11,790
This genome-editing technology
provides the opportunity
563
00:29:11,790 --> 00:29:13,860
both to identify
564
00:29:13,860 --> 00:29:16,230
genetic mutations
that cause disease,
565
00:29:16,230 --> 00:29:20,570
but also to actually correct
those mutations.
566
00:29:20,570 --> 00:29:23,870
The ability to
precisely fix errors in our DNA
567
00:29:23,870 --> 00:29:27,170
brings the promise
of extending our lives,
568
00:29:27,170 --> 00:29:30,940
lifting the shadow
that death casts over us.
569
00:29:30,940 --> 00:29:34,180
We could use CRISPR to stamp out
hereditary diseases
570
00:29:34,180 --> 00:29:37,750
like cystic fibrosis
and sickle cell anemia
571
00:29:37,750 --> 00:29:40,120
or simply make better humans,
572
00:29:40,120 --> 00:29:42,250
ones with extra-strong bones,
573
00:29:42,260 --> 00:29:43,660
low risk of Alzheimer's,
574
00:29:43,660 --> 00:29:46,590
or built-in resistance
to cancer.
575
00:29:46,590 --> 00:29:49,160
But a dark side looms.
576
00:29:49,160 --> 00:29:51,600
Could this technology be used
to create
577
00:29:51,600 --> 00:29:55,400
genetically engineered embryos
for a super race,
578
00:29:55,400 --> 00:29:57,870
an elite population
of designer babies
579
00:29:57,870 --> 00:30:02,140
with enhanced intelligence,
beauty, or strength?
580
00:30:02,140 --> 00:30:05,940
I, myself, came
to this realization over time,
581
00:30:05,950 --> 00:30:08,150
and one of the things
that really influenced me
582
00:30:08,150 --> 00:30:11,920
was a dream that I had
in which I was being asked
583
00:30:11,920 --> 00:30:16,520
to explain the CRISPR technology
to someone in a dark room,
584
00:30:16,520 --> 00:30:20,090
and when that person
turned around,
585
00:30:20,090 --> 00:30:22,830
it was the profile of Hitler.
586
00:30:22,830 --> 00:30:26,830
I still feel chills when I think
about that moment in my dream,
587
00:30:26,830 --> 00:30:31,500
when I really felt strongly
that this technology needs
588
00:30:31,510 --> 00:30:34,040
to be handled with caution.
589
00:30:34,040 --> 00:30:36,770
Humans genetically
engineered to live longer
590
00:30:36,780 --> 00:30:39,240
are no longer the stuff
of science fiction.
591
00:30:39,250 --> 00:30:41,310
The more we study our genome,
592
00:30:41,310 --> 00:30:44,750
the more opportunities
we will see to improve it.
593
00:30:44,750 --> 00:30:47,550
In fact, scientists
are already hunting
594
00:30:47,550 --> 00:30:51,820
for the genetic secret
to living for 200 years
595
00:30:51,830 --> 00:30:55,260
in the DNA of another animal.
596
00:30:59,280 --> 00:31:03,580
In 2007, fishermen caught
a bowhead whale
597
00:31:03,580 --> 00:31:06,110
off the coast of Alaska.
598
00:31:06,120 --> 00:31:08,250
Embedded in its flesh,
599
00:31:08,250 --> 00:31:13,590
they found a harpoon tip
dating to the 1890s.
600
00:31:13,590 --> 00:31:17,160
No mammal on earth lives
longer than the bowhead.
601
00:31:17,160 --> 00:31:20,390
Some of them live past 200.
602
00:31:20,400 --> 00:31:24,230
If we are looking for the
genetic tools to cheat death,
603
00:31:24,230 --> 00:31:27,670
all that we need is
probably already out there,
604
00:31:27,670 --> 00:31:30,400
in nature's vast pool of DNA.
605
00:31:30,410 --> 00:31:33,470
We just have to find it.
606
00:31:37,350 --> 00:31:39,750
Harvard scientist
George church believes
607
00:31:39,750 --> 00:31:43,020
we need to probe
the vast pool of animal DNA
608
00:31:43,020 --> 00:31:45,290
to find the secret
of longer life.
609
00:31:45,290 --> 00:31:47,150
One of the mysteries of aging
is why it is
610
00:31:47,160 --> 00:31:50,390
that some animals like mice
live for 2 1/2 years
611
00:31:50,390 --> 00:31:52,290
because of their
genetic program,
612
00:31:52,300 --> 00:31:55,700
while other animals like bowhead
whales live for 200 years
613
00:31:55,700 --> 00:31:57,300
because of a different program.
614
00:31:57,300 --> 00:31:59,470
There's a wide range
of life spans
615
00:31:59,470 --> 00:32:02,100
across all organisms in nature,
616
00:32:02,110 --> 00:32:04,370
but there is
a consistent trend...
617
00:32:04,370 --> 00:32:07,340
Large animals tend
to live longer.
618
00:32:07,340 --> 00:32:09,980
You could think of this
in terms of a swimming race...
619
00:32:11,380 --> 00:32:16,050
Between long-distance swimmers
and sprinters.
620
00:32:16,050 --> 00:32:19,750
In this analogy,
the bowhead whale long-live...
621
00:32:19,760 --> 00:32:22,990
They're like
the marathon white-cap swimmers,
622
00:32:22,990 --> 00:32:28,330
and the mice are like
the red-cap sprinters.
623
00:32:28,330 --> 00:32:32,300
Big animals move slowly
but last for the long haul.
624
00:32:32,300 --> 00:32:36,770
Small guys race along
and burn out quickly.
625
00:32:36,770 --> 00:32:39,210
But George doesn't think
size explains
626
00:32:39,210 --> 00:32:41,610
a bowhead whale's
long life span.
627
00:32:41,610 --> 00:32:45,780
He thinks the secret lies
in how it takes care of its DNA.
628
00:32:45,780 --> 00:32:47,780
Researchers
recently found evidence
629
00:32:47,780 --> 00:32:49,750
that the bowhead excels
630
00:32:49,750 --> 00:32:52,920
at repairing damage
to its genes.
631
00:32:52,920 --> 00:32:57,290
In humans, DNA damage is
a major cause of aging.
632
00:32:57,290 --> 00:32:59,890
George thinks we could
repair that damage using
633
00:32:59,900 --> 00:33:03,530
the powerful new CRISPR
gene-editing technique.
634
00:33:03,530 --> 00:33:06,500
We're harnessing
vast amounts of information
635
00:33:06,500 --> 00:33:09,170
gathered on long-lived animals
636
00:33:09,170 --> 00:33:11,640
and converting it
into a gene therapy
637
00:33:11,640 --> 00:33:15,480
that can test whether
we can do aging reversal
638
00:33:15,480 --> 00:33:17,110
in large animals and humans.
639
00:33:18,880 --> 00:33:21,420
Most of us die because
our organs fail...
640
00:33:21,420 --> 00:33:26,320
Our hearts, our lungs,
livers, our brains.
642
00:33:26,320 --> 00:33:29,420
But George thinks
we can build better organs
643
00:33:29,430 --> 00:33:32,060
by going back
and removing genetic defects
644
00:33:32,060 --> 00:33:34,660
from the cells
they are made from.
645
00:33:34,660 --> 00:33:36,630
To test this idea,
646
00:33:36,630 --> 00:33:39,170
George looked
at the genomes of pigs.
647
00:33:40,270 --> 00:33:42,870
We are using editing methods
648
00:33:42,870 --> 00:33:44,870
to engineer cells
that are capable
649
00:33:44,870 --> 00:33:47,540
of producing pig embryos.
650
00:33:47,540 --> 00:33:48,840
Scientists have discovered that,
651
00:33:48,850 --> 00:33:52,380
over the millennia,
pig DNA has been contaminated
652
00:33:52,380 --> 00:33:56,550
by 62 different viruses.
653
00:33:56,550 --> 00:33:59,420
George decided to use it
as a test case
654
00:33:59,420 --> 00:34:01,290
to see if gene-editing
655
00:34:01,290 --> 00:34:04,860
could delete
these tiny contaminants.
656
00:34:04,860 --> 00:34:06,860
What we did was unprecedented,
657
00:34:06,860 --> 00:34:11,630
which was change 62
pig viral genes simultaneously
658
00:34:11,630 --> 00:34:15,670
so that now the pigs are,
for the first time, virus-free.
659
00:34:15,670 --> 00:34:18,070
With sperm and egg cleansed
660
00:34:18,070 --> 00:34:19,970
of ancient contaminants,
661
00:34:19,980 --> 00:34:22,410
George made his own pig embryos
662
00:34:22,410 --> 00:34:25,080
using in vitro fertilization.
663
00:34:25,080 --> 00:34:27,210
Once the pig embryos
are implanted,
664
00:34:27,220 --> 00:34:30,050
we no longer have to keep
going back to the embryo stage.
665
00:34:30,050 --> 00:34:33,650
Then, the pigs breed
just like regular pigs would.
666
00:34:33,660 --> 00:34:36,860
It's just that they
no longer produce viruses.
667
00:34:36,860 --> 00:34:38,330
It also gives us the opportunity
668
00:34:38,330 --> 00:34:40,730
to make more healthy organs
669
00:34:40,730 --> 00:34:45,300
which are resistant to viruses,
cancer, and aging.
670
00:34:45,300 --> 00:34:47,670
Ultimately,
George wants to apply
671
00:34:47,670 --> 00:34:49,300
this technique to humans
672
00:34:49,310 --> 00:34:52,740
and to a much broader range
of genetic defects,
673
00:34:52,740 --> 00:34:54,680
deleting harmful genes
674
00:34:54,680 --> 00:34:56,540
and adding in beneficial ones
675
00:34:56,550 --> 00:35:00,180
we find in long-lived animals
like the bowhead whale.
676
00:35:02,220 --> 00:35:05,650
Today, we can test for genetic
defects in unborn children,
677
00:35:05,660 --> 00:35:08,960
but we lack the means
to cure them.
678
00:35:08,960 --> 00:35:11,060
So when you go
to a modern obstetrics clinic
679
00:35:11,060 --> 00:35:13,790
like this, and you're concerned
about genetic disease,
680
00:35:13,800 --> 00:35:16,860
the mother and the father can
get a readout of their genome
681
00:35:16,870 --> 00:35:20,840
and make decisions that might
involve termination.
682
00:35:20,840 --> 00:35:23,240
George believes that,
in the near future,
683
00:35:23,240 --> 00:35:26,710
parents won't have to face
these difficult choices.
684
00:35:26,710 --> 00:35:29,880
The gene-editing techniques
he's pioneering in animals
685
00:35:29,880 --> 00:35:33,180
will soon be applied
to the genes of human parents
686
00:35:33,180 --> 00:35:35,780
before they
ever conceive a child.
687
00:35:35,790 --> 00:35:38,520
In the near future,
you'll be able to edit
688
00:35:38,520 --> 00:35:40,390
either the mother
or father's body DNA
689
00:35:40,390 --> 00:35:42,720
so that the sperm
or egg does not contain
690
00:35:42,730 --> 00:35:44,460
the very serious disease
691
00:35:44,460 --> 00:35:46,630
and never even makes it
into an embryo.
692
00:35:46,630 --> 00:35:49,400
Further into the future,
693
00:35:49,400 --> 00:35:52,870
we'll even add DNA modifications
so that children are born
694
00:35:52,870 --> 00:35:58,070
not only healthy but
with long-lived super organs.
695
00:35:58,070 --> 00:36:02,410
Today, living for 200 years
is beyond our reach.
696
00:36:02,410 --> 00:36:05,950
But with precision editing
in the sperm and egg,
697
00:36:05,950 --> 00:36:07,310
our genes may soon have
698
00:36:07,320 --> 00:36:10,720
the staying power of the genes
of the bowhead whale.
699
00:36:10,720 --> 00:36:12,720
Just as our ancestors
700
00:36:12,720 --> 00:36:14,960
had a life expectancy
of 45 years,
701
00:36:14,960 --> 00:36:16,260
today it's more like 90.
702
00:36:16,260 --> 00:36:18,660
Mothers today can expect
their children to live
703
00:36:18,660 --> 00:36:20,730
into their 100s.
704
00:36:20,730 --> 00:36:22,260
Imagine a future where people
705
00:36:22,270 --> 00:36:25,730
over 100 years old continue
contributing to society
706
00:36:25,740 --> 00:36:28,500
as if they were
in their 30s again,
707
00:36:28,500 --> 00:36:31,570
where their vast experience
is valued,
708
00:36:31,570 --> 00:36:34,740
and ageism is
a thing of the past.
709
00:36:34,740 --> 00:36:37,880
But this man thinks
our quest to cheat death
710
00:36:37,880 --> 00:36:41,180
threatens the fabric
of civilization itself.
711
00:36:41,180 --> 00:36:45,020
He says it's time
for us to embrace death.
712
00:36:47,140 --> 00:36:49,470
A century ago,
713
00:36:49,480 --> 00:36:55,850
the average life expectancy
of an American was around 52.
714
00:36:55,850 --> 00:36:58,450
With genetic engineering,
715
00:36:58,450 --> 00:37:03,820
living to 150 will
fairly soon be the new norm.
716
00:37:03,820 --> 00:37:05,960
Now, that sounds great.
717
00:37:05,960 --> 00:37:12,430
Who doesn't want more time
to grow, to love, to create?
718
00:37:12,430 --> 00:37:17,500
But what happens
if we keep pushing the limit...
719
00:37:17,500 --> 00:37:22,470
300, 500, maybe forever?
720
00:37:22,480 --> 00:37:24,980
You'd think a world
where death is a rarity
721
00:37:24,980 --> 00:37:28,080
would be a utopia.
722
00:37:28,080 --> 00:37:30,610
But would it?
723
00:37:34,020 --> 00:37:38,460
Stephen cave is
a professional philosopher.
724
00:37:38,460 --> 00:37:42,990
He thinks a lot about death.
725
00:37:43,000 --> 00:37:47,260
You might say it's what gets him
out of bed in the morning.
726
00:37:47,270 --> 00:37:51,500
Most people, most of the time,
are running away from death.
727
00:37:51,500 --> 00:37:52,940
We're terrified of death
728
00:37:52,940 --> 00:37:54,910
even though it's one of life's
great certainties,
729
00:37:54,910 --> 00:37:56,510
along with taxes.
730
00:37:56,510 --> 00:37:59,280
Most people are in denial of it.
731
00:37:59,280 --> 00:38:01,780
But Stephen is
a little different.
732
00:38:01,780 --> 00:38:05,180
He's actually running
towards death.
733
00:38:05,180 --> 00:38:09,250
As he sees it,
our civilization depends on it.
734
00:38:09,260 --> 00:38:11,360
I think it's important
that we actually face up
735
00:38:11,360 --> 00:38:14,890
to mortality,
that actually life is richer
736
00:38:14,890 --> 00:38:16,560
and better and more valuable
737
00:38:16,560 --> 00:38:20,030
when we recognize
that it is limited.
738
00:38:20,030 --> 00:38:22,700
But that awareness
of our own mortality causes
739
00:38:22,700 --> 00:38:24,500
an intense anxiety.
740
00:38:24,500 --> 00:38:28,510
To deal with it,
we repress and deny it,
741
00:38:28,510 --> 00:38:31,280
and even lie to ourselves.
742
00:38:31,280 --> 00:38:35,710
Social psychologists call it
terror management theory.
743
00:38:35,710 --> 00:38:38,820
But what do we do?
How do we cope with that terror?
744
00:38:38,820 --> 00:38:43,320
Well, we tell ourselves stories
that deny the reality of death,
745
00:38:43,320 --> 00:38:47,930
that tell us that somehow
we can keep going forever.
746
00:38:47,930 --> 00:38:50,630
In other words,
confront someone with the fact
747
00:38:50,630 --> 00:38:52,430
that they're going to die,
748
00:38:52,430 --> 00:38:56,530
and they will believe any story
claiming we can live forever.
749
00:38:56,540 --> 00:39:00,270
So every civilization
has some story
750
00:39:00,270 --> 00:39:02,310
about why we don't need
to fear death.
751
00:39:02,310 --> 00:39:04,240
Now this might be a religion,
for example,
752
00:39:04,240 --> 00:39:07,980
that promises that if we believe
we can live forever in heaven.
753
00:39:07,980 --> 00:39:10,950
Or it might be patriotism
or nationalism
754
00:39:10,950 --> 00:39:14,520
that promises we can live on
as part of this greater whole.
755
00:39:18,760 --> 00:39:21,120
Imagine these
identically dressed runners
756
00:39:21,130 --> 00:39:25,060
represent one subgroup
of human society.
757
00:39:25,060 --> 00:39:28,430
And now suppose that
the group splits in two,
758
00:39:28,430 --> 00:39:31,940
with each half taking different
paths through the city.
759
00:39:31,940 --> 00:39:35,310
The two groups remain
indistinguishable
760
00:39:35,310 --> 00:39:37,270
from one another,
761
00:39:37,280 --> 00:39:40,080
until one passes
through a graveyard.
762
00:39:40,080 --> 00:39:43,410
The group who have been
running past the cemetery
763
00:39:43,420 --> 00:39:46,180
will unconsciously have been
reminded about death,
764
00:39:46,190 --> 00:39:49,050
and because of that they will
be in a different state of mind
765
00:39:49,050 --> 00:39:51,660
when they finish their run.
766
00:39:51,660 --> 00:39:54,260
When the members of
the group join back together,
767
00:39:54,260 --> 00:39:58,260
they meet a pair of individuals
who belong to a new group.
768
00:39:58,260 --> 00:40:00,530
The members of the group
who saw the tombstones
769
00:40:00,530 --> 00:40:03,300
aren't interested
in the outsiders.
770
00:40:03,300 --> 00:40:05,070
Those who never saw
the reminders
771
00:40:05,070 --> 00:40:08,440
of the dead
are more open-minded.
772
00:40:08,440 --> 00:40:11,440
Over 400 studies have shown
merely thinking about death
773
00:40:11,440 --> 00:40:15,250
causes us to pull tighter
into our social groups.
774
00:40:15,250 --> 00:40:17,110
This may sound like a bad thing,
775
00:40:17,120 --> 00:40:19,950
but Stephen argues that,
on balance,
776
00:40:19,950 --> 00:40:23,750
over the course of history,
it has not been.
777
00:40:23,760 --> 00:40:26,260
Fear of death is the engine
that drives us
778
00:40:26,260 --> 00:40:28,530
to create tight-knit societies,
779
00:40:28,530 --> 00:40:33,700
and from that culture and
civilization itself are born.
780
00:40:33,700 --> 00:40:38,770
So much of what we've built is
about helping us to live longer.
781
00:40:38,770 --> 00:40:41,340
And if we can't stay
alive physically, you know,
782
00:40:41,340 --> 00:40:43,140
if buildings and medicine
783
00:40:43,140 --> 00:40:45,140
and science
doesn't do it for us,
784
00:40:45,140 --> 00:40:47,780
then we've got art
and culture and religion
785
00:40:47,780 --> 00:40:49,410
that helps to carry us forward,
786
00:40:49,420 --> 00:40:52,180
even after bodily death.
787
00:40:52,180 --> 00:40:55,390
Stephen believes
all civilizations exist
788
00:40:55,390 --> 00:40:58,390
to defend us
against the fear of death.
789
00:40:58,390 --> 00:41:00,190
Without the fear of death,
790
00:41:00,190 --> 00:41:04,600
humanity as we know it
would cease to exist.
791
00:41:04,600 --> 00:41:06,760
If we all woke up tomorrow
and found ourselves immortal,
792
00:41:06,770 --> 00:41:09,830
then there would be profound
changes in our society.
793
00:41:09,840 --> 00:41:12,670
Religion would lose
its unique selling point.
794
00:41:12,670 --> 00:41:14,740
We wouldn't need to sign up
795
00:41:14,740 --> 00:41:16,440
in order
to get eternity in heaven
796
00:41:16,440 --> 00:41:19,210
if we already had eternity
here on earth.
797
00:41:19,210 --> 00:41:23,280
The inevitability
that our lives will one day end
798
00:41:23,280 --> 00:41:25,620
has spurred us
to leave a legacy,
799
00:41:25,620 --> 00:41:28,550
to create literature,
art, technology,
800
00:41:28,550 --> 00:41:30,920
everything
that makes us who we are.
801
00:41:30,920 --> 00:41:33,920
Rather than paralyzing
us with fear,
802
00:41:33,930 --> 00:41:36,690
Stephen believes
knowledge of our demise
803
00:41:36,700 --> 00:41:39,160
can help us live.
804
00:41:39,160 --> 00:41:41,630
You can see life as like a book.
805
00:41:41,630 --> 00:41:43,970
Just as a book
is bounded by its covers,
806
00:41:43,970 --> 00:41:47,600
so our lives are bounded
by beginning and end.
807
00:41:47,610 --> 00:41:50,870
And even though a book
is limited by its cover,
808
00:41:50,880 --> 00:41:54,380
still it can encompass
fantastic adventures
809
00:41:54,380 --> 00:41:56,910
and distant landscapes
and exotic figures.
810
00:41:56,920 --> 00:41:59,120
The characters in a book,
811
00:41:59,120 --> 00:42:04,120
they're not afraid
of you reaching the last page.
812
00:42:04,120 --> 00:42:05,260
And so we shouldn't worry
813
00:42:05,260 --> 00:42:08,090
about whether our story
is long or short,
814
00:42:08,090 --> 00:42:10,260
whether it's a comic story
or an epic.
815
00:42:10,260 --> 00:42:13,960
We should just focus
on making it a good story.
816
00:42:15,930 --> 00:42:20,200
We've been so busy striving
to cheat death,
817
00:42:20,210 --> 00:42:23,140
we forgot to ask ourselves
if we really want to live
818
00:42:23,140 --> 00:42:26,040
in a world filled
with immortals.
819
00:42:26,050 --> 00:42:29,350
As science allows life
to last longer,
820
00:42:29,350 --> 00:42:32,020
it may also grow sweeter,
821
00:42:32,020 --> 00:42:35,390
free from disease,
physical infirmity,
822
00:42:35,390 --> 00:42:38,620
and the slow decay of the mind.
823
00:42:38,620 --> 00:42:41,560
But nothing needs
to last forever.
824
00:42:41,560 --> 00:42:46,130
To the young,
death's shadow brings fear.
825
00:42:46,130 --> 00:42:50,230
But to a man of my age,
it brings vigor,
826
00:42:50,240 --> 00:42:54,070
the desire to do what I love
while I still have time.
827
00:42:54,070 --> 00:42:56,570
Oh, I'm happy to cheat death,
828
00:42:56,580 --> 00:43:00,710
but only as long
as my passion for life remains.