"Are we born to die?" "For millennia, we've tried To outsmart our own mortality..." "Only to find that death Is the greatest certainty." "But for the first time In history," "That may be about to change." "Science is unraveling The mysteries of aging," "Discovering an animal." "That comes back from the dead," "And turning our quest For eternal life on its head." "Are we about to enter The age of immortality?" "Or is death necessary For the survival of our species?" "Can we cheat death?" "Space, time, life itself." "The secrets of the cosmos." "Lie through the wormhole." "Captions paid for by Discovery communications." "When will I die?" "It's a question I've asked myself." "I'm sure you've thought About it, too." "From the day we are born," "The clock of our lives marks." "Our inevitable decline..." "Ticking inexorably Toward our final hour." "Medical science has made Incredible advances." "In prolonging life." "For most of human history," "People were lucky To survive into their 40s." "Now, people often break 100." "The oldest person we know of." "Lived to celebrate Her 122nd birthday." "And as we probe deeper into The fundamental biology of life," "We are now questioning." "Whether death really has To come at all," "Whether we can..." "Stop the clock" "David sinclair likes To live in the fast lane." "But he knows our bodies," "Like cars, can't push The needle forever." "Well, I've been interested In studying aging." "Since I can remember." "I think it was Around the age of 4." "When I realized that my parents Would one day die," "And I would, too," "And that seemed Extremely tragic." "And I also thought That if we could figure out." "Why we age And what we could do about it," "That would have a really big Beneficial impact on the world." "David spends a lot of time Thinking about old age." "But he's interested in more Than the wrinkles on our skin." "As a professor of genetics At harvard," "He asks what role Our genes play in aging." "An aging body is a lot Like a rusty old car." "Rust, or oxidation, Is what causes everything," "Including our dna, To break down." "David believes We may soon be able." "To repair our failing bodies." "As easily as a mechanic can Spruce up a rusty body panel." "David's research focuses." "On our body's own set Of repair mechanics..." "A group of genes Called sirtuins." "As our bodies age," "They accumulate Old or senescent cells." "And longevity genes prevent Those cells from accumulating." "This would be similar, In an old car," "To the mechanics removing Rusty old parts." "And replacing them With new ones." "But these repair genes Begin to fall silent." "As we pass our 30s and 40s." "So if we could find a way." "Of getting these longevity genes Working harder," "This would be a way To keep our bodies healthier." "And working for longer." "If our cells have The tools to restore." "And rebuild themselves, why Can't they do that forever..." "In other words, stop aging?" "Sinclair has dedicated His career." "To finding ways to help Our repair mechanisms." "Keep going well past middle age." "It's driven him deep into The inner mechanics of the cell." "In order for a human cell To function," "It requires close collaboration." "Between two distinct parts..." "The nucleus, The cell's control center," "And its tiny power engines Called mitochondria." "Every task a cell performs Relies on precise communication." "Between these two." "Imagine this kitchen Is a young cell." "Inside it are the nucleus And mitochondria," "Two chefs working in concert." "Our genes are Just like a recipe book." "In a young cell, the nucleus And the mitochondria," "They're reading The recipe perfectly," "And they're really Working well together." "A delicious meal Is taking shape." "But over time, The communication." "And coordination Between the chefs gets worse." "In an old cell, the nucleus And the mitochondria," "They're throwing in things That don't belong." "They're leaving things out." "They don't communicate well." "One chef might be trying To pass a spoon to the other," "And the other one is Not paying attention." "It's as if the chefs Are spilling on the recipe book." "And losing that ability To read it." "Dna is the recipe of life." "But over time," "Wear and tear makes The recipe hard to read," "And our cells lose the ability To prepare the meal." "Whether it's damage Or changes in the environment," "The cell eventually loses The memory." "Of which genes should be on And which genes should be off," "And that, we think, Causes aging." "David has been combing Through aging cells," "Trying to see if he can identify." "Which vital ingredient They lack." "And now he thinks He's found the molecule." "That will get our cellular Kitchen back on track." "It's called n.A.D." "it's a molecule That's essential for life." "Without it, you'd be dead In about 20 seconds." "And, as we age, The levels of this molecule." "Go down steadily to the point Where you have." "About half the levels Of what you once had." "David wondered if there Was a way to restore n.A.D." "To more youthful levels." "He injected mice With a special compound." "That boosts production of n.A.D." "The effects were dramatic." "This mouse is Very youthful and energetic." "You can see the ears are still Nice and young-looking," "And the fur isn't turning gray." "As you can see here, This mouse is going gray." "She's losing hair." "Her ears are getting wrinkled." "Her spine is starting to bend." "Well, what's amazing About these mice." "Is that they were born On the same day." "What we saw was A rapid-aging reversal." "In their muscles," "From a mouse that's equivalent To a 60-year-old human." "Back to a 20-year-old." "If we could apply this To humans," "Imagine what a city street Might look like 50 years from now." "Almost everyone Would appear youthful," "Free of the illness And frailties of age." "David's research." "May one day slow down and Even reverse aging in people." "We're not talking here About being older for longer." "It's quite the opposite." "It's about being Younger for longer." "But david's work only Treats the symptoms of aging." "It doesn't attack The root of the problem..." "The gradual decay of our dna." "Japanese scientist shin kubota Thinks we can turn that tide." "My dream is to live With my families." "Of different generations." "So that we can enjoy Our great-great grandchildren." "The sea is Where all life began," "And with every empty shell It leaves behind," "It seems to prove That all lives must end." "But shin knows otherwise." "Shin studies A tiny marine animal." "Called turritopsis dohrnii," "Or the immortal jellyfish." "This creature has figured out How to cheat death." "At shin's lab In the town of shirahama." "Is the world's Only captive population." "Of immortal animals." "First discovered In the mediterranean in 1988," "This jellyfish is no bigger Than your fingernail." "Immortal jellyfish is Very cute, small jellyfish." "Diameter is About several millimeter." "But after showing These creatures." "Such tender, loving care," "Shin does the unthinkable." "He chops them into pieces." "Try to kill this jellyfish," "You will be surprised." "A remarkable thing happens." "The jellyfish does not die Beneath shin's hand." "Instead, It seems to be reborn." "The bell reabsorbs the tentacles And becomes a gelatinous blob." "I call this stage the meatball." "The meatball becomes a polyp," "And soon it matures Into an adult jellyfish." "The jellyfish shows Very remarkable transformation." "The jellyfish's secret Is a process called." "Cellular Transdifferentiation." "The cells in any fragment Of the animal." "Can figure out What body parts are missing," "Then retrofit themselves To grow back the entire body." "If we could determine How do the jellyfish rejuvenate," "We could borrow Its techniques." "Imagine shin were attacked By a mutant sea monster." "It's japan, after all, So it's not such a crazy idea." "If the only thing left of shin." "Were the tip Of one little finger..." "Transdifferentiation could Turn those finger cells." "Into brain cells," "Heart cells, muscle cells." "Shin would come back From the dead." "It seems like science fiction," "But jellyfish and humans Have surprisingly similar genes." "If a jellyfish can Learn this trick," "Perhaps we can, as well." "From the ruins Of a single animal," "Hundreds of identical jellyfish Have sprouted." "It's a feat unequaled in nature," "But perhaps not for long." "If we could unlock the genetic Secrets of this jellyfish," "We could regenerate Aging organs," "Perhaps even entire bodies." "I believe, one day," "That humans can become immortal." "Using the same process As a jellyfish." "The promise of immortality Always seemed a fantasy," "But the infinite regeneration." "Of the jellyfish Is biological reality." "So can we get there With our biology?" "Some people believe we will," "And sooner than you think." "Death has always been A fact of life." "Why?" "Because our bodies wear down." "Our hearts won't Beat forever." "Our muscles gradually weaken." "Our brains lose their edge." "But it doesn't have To be that way." "Our bodies have Built-in technology." "To repair themselves..." "Stem cells." "These cells have the potential." "To replenish any organ In the body." "If we can coax them Into doing it." "Cell biologist larry goldstein Thinks that if we want." "To extend our life-spans," "We'll have to leap past A major obstacle..." "The slow decline Of our minds." "I had The unfortunate experience." "Of helping to care for my mother." "When she developed Alzheimer's disease." "In her late 60s." "It was a terrible experience," "And I hate the idea Of anybody else." "Having to go through that With their family members." "And their loved ones." "50% of us will develop Alzheimer's disease." "By the time We're 85 years old." "It does no good to age to 85." "And be physically healthy." "If your brain doesn't function." "At the sanford consortium Of regenerative medicine," "Larry keeps an hourglass On his desk." "It reminds him of all the people Who are running out of time." "But larry thinks He's found the key." "To fighting Debilitating diseases of aging." "Like alzheimer's..." "Stem cells." "The problem is that We don't really understand." "What goes wrong in brain cells That have the disease." "And we're using stem cells To try to tackle that problem." "In a unique way." "Stem cells are the body's Original building blocks." "They have the potential To become any type of cell." "In the primordial furnace Of the womb," "Our bodies use These raw materials." "Much like a master glassblower," "Sculpting beautifully intricate, Finished organs." "From shapeless, raw ingredients." "You can think about stem cells." "As being like Biological raw material," "Just like these glass pellets Are the raw material." "That you can throw Into a really hot oven." "And use to make anything at all That you'd like to make." "So, let's see how this works." "In you go." "Ooh, that's hot." "As we grow from an embryo," "Our bodies prepare And shape stem cells." "For the adult roles." "They will need to fill." "Each stem cell decides What adult cell type to become." "Based on cues From the cells around it." "Stem cells respond." "To biochemical signals From other cells." "And so a heart cell started out As a stem cell," "And it got instructions To become a heart cell." "You can imagine Putting a heart together." "With different Vessel cells." "Or different Muscle cells." "A great glassblower can put all These different shapes together." "To make something Beautiful at the end." " Cool enough to touch." " Amazing." "It's incredible, really, When you think about it." "Millions and millions Of stem cells get together," "Respond to the right sorts Of biochemical signals," "And make this heart." "The power of stem cells To create organs from scratch." "Has drawn the interest Of scientists for decades." "The goal is To harness this resource." "To rebuild and replace Failing tissue." "But there's a problem..." "By the time we're fully grown," "We've exhausted our supply Of embryonic stem cells," "And the few stem cells We have left." "Are not nearly as flexible." "There are so-called Adult stem cells," "Which are partially formed." "They're committed to make one Of the types of adult tissues." "Skin stem cells make skin." "Brain stem cells Make brain tissues." "But the important point." "Is that It's partially committed." "It has part of a shape That commits it." "To do some things And not others." "Only embryonic stem cells." "Have the flexibility To become any cell in the body." "But harvesting them From embryonic tissue." "Has proved politically Controversial." "Then, in 2006," "Scientists made A stunning discovery." "Adult stem cells can be recycled Back to embryonic form." "By modifying Just four of their genes." "They become what are called Induced pluripotent stem cells," "Or ips cells." "So the discovery of ips cell." "Was like the shot heard 'round the world." "It was a true revolution In our understanding." "Of what cells could do," "And how simply it could be done." "Like throwing glass Back into the furnace," "We can now restore cells To their embryonic state." "And create raw materials." "We could use To stay eternally young." "You could make this Into brain cells," "Or heart cells, or skin cells, Or what have you." "We've used genetic trickery To take, for example," "A skin cell from my arm," "Trick it using genetic elements." "Into becoming a cell." "Like an embryonic stem cell In its abilities." "Iarry is now using These rebooted cells." "To uncover what goes wrong In alzheimer's." "He starts with skin cells Of people with the disease." "And changes them Into brain cells." "Then, he can study exactly What's going wrong." "In those cells and develop New drugs to treat them." "Right now, we have zero drugs." "That alter the course Of alzheimer's disease." "I do know that if we want To make it past 85 or 90." "On a regular basis," "We're going to have To solve the problem." "Iarry hopes His work on alzheimer's is." "The beginning Of something bigger." "He thinks if we stored Our stem cells." "While we're young and healthy," "We could use them later To replace our aging organs." "It's incredible really When you think about it..." "The ability To someday build an organ." "From stem cells like this Will be a huge breakthrough." "In the future, We may be able." "To extend our lives By recreating." "Our failing hearts, lungs, And kidneys." "But what happens to our society When people live longer?" "Are we turning nature's plan Upside down?" "One scientist Has simulated a world." "Where no one dies of old age," "And he's reached A startling conclusion." "If our organs have The power to regenerate," "Why do they allow us To age and die?" "Plants, bugs, animals..." "It happens to us all." "Perhaps it's because." "Death is programmed into us By evolution." "Old animals must die To free up space for the young." "So, if we cheat death," "If we regenerate The sweetness of youth..." "Will evolution end?" "It's taken humans More than 1,000 years." "And many lifetimes To master the game of chess." "That's a puzzle for brazilian Evolutionary biologist." "André martins." "Wouldn't it be better If one person." "Could live long enough To acquire." "That mastery all By him or herself?" "For quite a while, Scientists thought." "That evolution could Not explain aging." "When someone die, in average, They will leave less children," "And that's a clear disadvantage." "From the evolutionary Point of view." "Evolution is Supposed to favor." "The individuals Best adapted for survival." "So why doesn't it let us Survive forever?" "Why are we denied The ultimate adaptation?" "Andr created A computer simulation." "To find out." "I have always find the evolution Problem fascinating." "I thought it could explain Not how but why we age." "Andr' simulation uses Game theory," "The math of competitive Situations." "He thought he could find out." "Whether dying Actually serves a purpose." "By staging a competition." "So, what the computer model Does is simulate the competition." "Between mortals And immortals." "When you see blue, it means That that region of space," "There is a mortal living there." "And if it's red, there is An immortal living there." "They fill out every space." "And they start competing For the limited resources there." "To picture andr' simulation," "Imagine a head-to-head contest." "Between two very different Soccer teams." "The immortal players, in red, Do not wear out with time." "But the mortals, in blue," "Will eventually become Too tired to play." "By pitting the two Against each other." "In a game lasting Many generations," "Andr thought he could find out." "Just how much advantage Immortality conveys." "Every time I run the simulation," "The same thing happens." "The advantage of not dying Makes a huge difference," "And the immortals Start winning." "Like soccer, Life is a competitive struggle." "If you compete more effectively, You control the game." "But andr' simulation contains Another life-like factor..." "Environmental change." "Just like in the real world," "Andr' virtual players face Constantly shifting conditions," "Like new diseases," "Predators," "And climate change." "While immortals can Struggle through them," "Not all mortals make it." "However, when they die," "They are replaced With younger, stronger players." "In any Evolutionary process," "If you are mutating And adapting," "The new generations will be Slightly better than older ones." "Because they are The ones that survive." "Since the mortals can evolve," "This gives them an advantage." "That allow us then To get back in the field." "In evolution, Each new generation." "Has some tricks The last one didn't." "And the faster You get them on the field," "The faster the species improves." "The impact, After many generations," "Is huge." "First, there is No advantage for any side." "And then, slowly The blue mortals start winning." "And after a while, They can actually drive." "The red team, the immortals, To extinction." "In the end, The mortal population wins." "Because the immortals Can't adapt." "They're doomed." "This suggests that aging Has a biological goal." "Andr believes, to keep pace With a changing world," "We need new generations With new adaptations." "And we must make room for them," "Which makes mortality necessary." "The mortal can drive The immortals to extinction." "It was much easier Than what I was expecting." "From evolutionary point of view For the species," "It is a good thing to die." "Yeah!" "From a personal point of view, It's not a good thing at all." "We owe our very existence To the wonders of evolution," "Even though it has designed us To get out of the way." "But what if we could sidestep Natural evolution," "Manipulate the genes That make us die?" "Could we evolve ourselves To live forever?" "At the core of every living cell." "Is a single Fabulously complex molecule..." "Dna." "Its genetic code Is the source of life." "But dna is also The reason we die." "As we age, our dna code Gets slowly jumbled," "Until it can no longer Keep us alive." "If we can undo Those mistakes," "We can stop death's shadow From creeping up on us." "Professor Jennifer doudna thinks We're on the brink." "Of being able to fix All the errors in our dna." "And make ourselves Immune to disease and decay." "It's been an amazing decade Or more in science." "When it's been possible To sequence." "Not only the entire human genome." "But now many human genomes." "And what's really on the horizon." "Is the opportunity To rewrite that information." "Over the past few years, Jennifer has developed." "A revolutionary Dna-editing technique." "Which has turned the dream Of modifying our genes." "Into practical reality." "What's exciting right now Is that we have a chance." "To make changes to the dna." "At the level of a single letter." "In the more Than 3 billion letters." "In the human cell." "So this is a wonderful moment," "When a technology Has become available." "For that kind of precision Genome engineering." "In the past, Dna editing has been." "A crude, hit-and-miss affair." "Imagine trying to fix A pair of eyeglasses." "Without being able To see them." "And with tools that are Far too big for the job." "We didn't dare To edit human genes that way." "But Jennifer And her collaborator," "Emmanuelle charpentier, Have developed a new," "Far more precise tool." "That makes dna surgery Not only possible," "But easy." "It's called crispr," "And it places Almost god-like powers." "In the hands of humanity." "Like many scientific wonders," "Crispr was pioneered By nature herself." "Inside bacteria." "We began our project With the goal of understanding." "How bacteria fight Viral infection." "But we recognized That molecules involved." "In those processes In bacteria." "Could be harnessed As a technology." "For rewriting the dna in cells." "You could think About the dna of a bacterium." "As a house." "And the invading viral dna As a burglar." "Jennifer And emmanuelle discovered." "That bacteria have a built-in Surveillance system." "They can't prevent The first attack..." "But a system called crispr." "Takes a precise snapshot Of the viral dna," "The same way A security camera captures." "A picture of a burglar." "In a real bacterial cell," "The crispr sequence is the way." "That the cell records images In the form of dna." "That represent foreign invaders." "And keep it for future reference." "To protect the cell From those same invaders." "When the intruder Shows up a second time," "The bacterial cell Recognizes the invader." "From stored surveillance images." "And calls the cops." "In the bacterial cell, Those cops are the enzyme cas9." "So when the house Pulls out a picture." "From the surveillance camera..." "And identifies A potential invader," "That's the crispr system Using the enzyme cas9." "To find and destroy foreign dna." "The cas9 molecule acts Like a pair of scissors." "Precisely guided by crispr." "To a matching site On the virus' dna." "It then cuts the dna In that spot," "Destroying the virus' Ability to reproduce." "The threat to the bacterium Is eliminated." "But Jennifer realized." "She could adapt This natural mechanism." "Into a pinpoint method For gene editing," "Accurate down to A single letter of dna." "This genome-editing technology Provides the opportunity." "Both to identify." "Genetic mutations That cause disease," "But also to actually correct Those mutations." "The ability to Precisely fix errors in our dna." "Brings the promise Of extending our lives," "Lifting the shadow That death casts over us." "We could use crispr to stamp out Hereditary diseases." "Like cystic fibrosis And sickle cell anemia." "Or simply make better humans," "Ones with extra-strong bones," "Low risk of alzheimer's," "Or built-in resistance To cancer." "But a dark side looms." "Could this technology be used To create." "Genetically engineered embryos For a super race," "An elite population Of designer babies." "With enhanced intelligence, Beauty, or strength?" "I, myself, came To this realization over time," "And one of the things That really influenced me." "Was a dream that I had In which I was being asked." "To explain the crispr technology To someone in a dark room," "And when that person Turned around," "It was the profile of hitler." "I still feel chills when I think About that moment in my dream," "When I really felt strongly That this technology needs." "To be handled with caution." "Humans genetically Engineered to live longer." "Are no longer the stuff Of science fiction." "The more we study our genome," "The more opportunities We will see to improve it." "In fact, scientists Are already hunting." "For the genetic secret To living for 200 years." "In the dna of another animal." "In 2007, fishermen caught A bowhead whale." "Off the coast of alaska." "Embedded in its flesh," "They found a harpoon tip Dating to the 1890s." "No mammal on earth lives Longer than the bowhead." "Some of them live past 200." "If we are looking for the Genetic tools to cheat death," "All that we need is Probably already out there," "In nature's vast pool of dna." "We just have to find it." "Harvard scientist George church believes." "We need to probe The vast pool of animal dna." "To find the secret Of longer life." "One of the mysteries of aging Is why it is." "That some animals like mice Live for 2 1/2 years." "Because of their Genetic program," "While other animals like bowhead Whales live for 200 years." "Because of a different program." "There's a wide range Of life spans." "Across all organisms in nature," "But there is A consistent trend..." "Large animals tend To live longer." "You could think of this In terms of a swimming race..." "Between long-distance swimmers And sprinters." "In this analogy, The bowhead whale long-live..." "They're like The marathon white-cap swimmers," "And the mice are like The red-cap sprinters." "Big animals move slowly But last for the long haul." "Small guys race along And burn out quickly." "But george doesn't think Size explains." "A bowhead whale's Long life span." "He thinks the secret lies In how it takes care of its dna." "Researchers Recently found evidence." "That the bowhead excels." "At repairing damage To its genes." "In humans, dna damage is A major cause of aging." "George thinks we could Repair that damage using." "The powerful new crispr Gene-editing technique." "We're harnessing Vast amounts of information." "Gathered On long-lived animals." "And converting it Into a gene therapy." "That can test whether We can do aging reversal." "In large animals and humans." "Most of us die because Our organs fail..." "Our hearts, our lungs," "Livers, our brains." "But george thinks We can build better organs." "By going back And removing genetic defects." "From the cells They are made from." "To test this idea," "George looked At the genomes of pigs." "We are using Editing methods." "To engineer cells That are capable." "Of producing pig embryos." "Scientists Have discovered that," "Over the millennia, Pig dna has been contaminated." "By 62 different viruses." "George decided to use it As a test case." "To see if gene-editing." "Could delete These tiny contaminants." "What we did Was unprecedented," "Which was change 62 Pig viral genes simultaneously." "So that now the pigs are, For the first time, virus-free." "With sperm And egg cleansed." "Of ancient contaminants," "George made his own pig embryos." "Using in vitro fertilization." "Once the pig embryos Are implanted," "We no longer have to keep Going back to the embryo stage." "Then, the pigs breed Just like regular pigs would." "It's just that they No longer produce viruses." "It also gives us the opportunity." "To make more healthy organs." "Which are resistant to viruses, Cancer, and aging." "Ultimately, George wants to apply." "This technique to humans." "And to a much broader range Of genetic defects," "Deleting harmful genes." "And adding in beneficial ones." "We find in long-lived animals Like the bowhead whale." "Today, we can test for genetic Defects in unborn children," "But we lack the means To cure them." "So when you go To a modern obstetrics clinic." "Like this, and you're concerned About genetic disease," "The mother and the father can Get a readout of their genome." "And make decisions that might Involve termination." "George believes that, In the near future," "Parents won't have to face These difficult choices." "The gene-editing techniques He's pioneering in animals." "Will soon be applied To the genes of human parents." "Before they Ever conceive a child." "In the near future, You'll be able to edit." "Either the mother Or father's body dna." "So that the sperm Or egg does not contain." "The very serious disease." "And never even makes it Into an embryo." "Further into the future," "We'll even add dna modifications So that children are born." "Not only healthy but With long-lived super organs." "Today, living for 200 years Is beyond our reach." "But with precision editing In the sperm and egg," "Our genes may soon have." "The staying power of the genes Of the bowhead whale." "Just as our ancestors." "Had a life expectancy Of 45 years," "Today it's more like 90." "Mothers today can expect Their children to live." "Into their 100s." "Imagine a future Where people." "Over 100 years old continue Contributing to society." "As if they were In their 30s again," "Where their vast experience Is valued," "And ageism is A thing of the past." "But this man thinks Our quest to cheat death." "Threatens the fabric Of civilization itself." "He says it's time For us to embrace death." "A century ago," "The average life expectancy Of an american was around 52." "With genetic engineering," "Living to 150 will Fairly soon be the new norm." "Now, that sounds great." "Who doesn't want more time To grow, to love, to create?" "But what happens If we keep pushing the limit... 300, 500, maybe forever?" "You'd think a world Where death is a rarity." "Would be a utopia." "But would it?" "Stephen cave is A professional philosopher." "He thinks a lot about death." "You might say it's what gets him Out of bed in the morning." "Most people, most of the time, Are running away from death." "We're terrified of death." "Even though it's one of life's Great certainties," "Along with taxes." "Most people are in denial of it." "But stephen is A little different." "He's actually running Towards death." "As he sees it, Our civilization depends on it." "I think it's important That we actually face up." "To mortality, That actually life is richer." "And better and more valuable." "When we recognize That it is limited." "But that awareness Of our own mortality causes." "An intense anxiety." "To deal with it, We repress and deny it," "And even lie to ourselves." "Social psychologists call it Terror management theory." "But what do we do?" "How do we cope with that terror?" "Well, we tell ourselves stories That deny the reality of death," "That tell us that somehow We can keep going forever." "In other words, Confront someone with the fact." "That they're going to die," "And they will believe any story Claiming we can live forever." "So every civilization Has some story." "About why we don't need To fear death." "Now this might be a religion, For example," "That promises that if we believe We can live forever in heaven." "Or it might be patriotism Or nationalism." "That promises we can live on As part of this greater whole." "Imagine these Identically dressed runners." "Represent one subgroup Of human society." "And now suppose that The group splits in two," "With each half taking different Paths through the city." "The two groups remain Indistinguishable." "From one another," "Until one passes Through a graveyard." "The group who have been Running past the cemetery." "Will unconsciously have been Reminded about death," "And because of that they will Be in a different state of mind." "When they finish their run." "When the members of The group join back together," "They meet a pair of individuals Who belong to a new group." "The members of the group Who saw the tombstones." "Aren't interested In the outsiders." "Those who never saw The reminders." "Of the dead Are more open-minded." "Over 400 studies have shown Merely thinking about death." "Causes us to pull tighter Into our social groups." "This may sound Like a bad thing," "But stephen argues that, On balance," "Over the course of history, It has not been." "Fear of death is the engine That drives us." "To create tight-knit societies," "And from that culture and Civilization itself are born." "So much of what we've built is About helping us to live longer." "And if we can't stay Alive physically, you know," "If buildings and medicine." "And science Doesn't do it for us," "Then we've got art And culture and religion." "That helps to carry us forward," "Even after bodily death." "Stephen believes All civilizations exist." "To defend us Against the fear of death." "Without the fear of death," "Humanity as we know it Would cease to exist." "If we all woke up tomorrow And found ourselves immortal," "Then there would be profound Changes in our society." "Religion would lose Its unique selling point." "We wouldn't need to sign up." "In order To get eternity in heaven." "If we already had eternity Here on earth." "The inevitability That our lives will one day end." "Has spurred us To leave a legacy," "To create literature, Art, technology," "Everything That makes us who we are." "Rather than paralyzing Us with fear," "Stephen believes Knowledge of our demise." "Can help us live." "You can see life As like a book." "Just as a book Is bounded by its covers," "So our lives are bounded By beginning and end." "And even though a book Is limited by its cover," "Still it can encompass Fantastic adventures." "And distant landscapes And exotic figures." "The characters in a book," "They're not afraid Of you reaching the last page." "And so we shouldn't worry." "About whether our story Is long or short," "Whether it's a comic story Or an epic." "We should just focus On making it a good story." "We've been so busy striving To cheat death," "We forgot to ask ourselves If we really want to live." "In a world filled With immortals." "As science allows life To last longer," "It may also grow sweeter," "Free from disease, Physical infirmity," "And the slow decay Of the mind." "But nothing needs To last forever." "To the young, Death's shadow brings fear." "But to a man of my age, It brings vigor," "The desire to do what I love While I still have time." "I'm happy to cheat death," "But only as long As my passion for life remains."