Original subtitles

What is the meaning of life?

Don't you believe there's a reason for us being here?

Join the Greenleaf community.

We are, after all, such sophisticated creatures,

the result of billions of years of evolution.

Surely life is about more than just our biological needs,

more than the daily rat race.

Is all the knowledge we've gained

over the generations aiming towards some final goal?

Are we architects of our own fate?

Or is life just a series of random accidents?

Is our existence just a fluke of nature?

Or are we here for a reason?

Space, time, life itself.

The secrets of the cosmos lie through the wormhole.

Captions by vitac... www.Vitac.Com

captions paid for by discovery communications

why are we here?

I know you've thought about it.

We all have.

What is our purpose?

What is our destiny?

We're born.

If we're lucky, we reproduce,

and then we die.

Repeat that a few billion times,

and you get from the first simple life forms on Earth

to us.

Ever since Darwin,

scientists have been working on how we got here.

But now they're asking the question

we all seek the answer to... Why?

Is all our wonderful complexity

directed towards some greater goal?

Do our lives have an ultimate purpose?

To English biochemist Lee Cronin,

everything exists for a reason.

[ Bell dings ]

Even haggis, the bizarre sheep stomach dish

that the Scots can't get enough of.

Cronin: Haggis exists because it's the Scottish national dish.

And it's been refined for hundreds of years.

And that has a lot of parallels with, actually, biology.

Freeman: 3.5 billion years ago, the first living cell appeared.

Before that, Earth was just a vast soup of chemicals.

Why did those chemicals combine in just the right amounts

in just the right sequence to become living things?

Lee is convinced that it couldn't have been dumb luck,

just as a chef can't invent haggis

by randomly throwing ingredients together.

The invention of the haggis recipe required feedback.

Cronin: So as information passed back over time,

and the customer, if you like, is going, "no, that's wrong,

that's wrong, that's awful."

And this gets better and better and better,

until we get to the perfect haggis.

Freeman: Lee thinks the environment on early Earth played the role

of the chef's customer.

Cronin: What we think happened is there is a natural law of evolution,

that it refines the chemicals in steps over time,

where we can go from this easy, to start with,

to this very special dish.

Freeman: If Lee is right, the forces of evolution

were at work long before the first cell.

Chemicals competed against other chemicals.

To find out for sure, Lee thought, why not play god

and try to evolve chemicals into life forms in the lab?

This is a machine that simulates

millions of years of chemical evolution

in a matter of weeks.

Lee starts with four simple chemicals

that can be mixed in 17 million possible combinations.

So in the first step,

the ingredients are selected by the machine.

And then, they are pumped into the Wells here.

And they make random recipes.

They just select random amounts.

Freeman: The machine then squirts out tiny blobs

of each chemical cocktail into a water-filled petri dish.

It's videoing the actual droplet behavior.

So it's looking at how much the droplets are moving.

So that's one feature that we want.

Another feature we're looking for is droplets that divide,

so it's like replication.

Another property we're looking for is droplets than can vibrate

and sense the environment.

Freeman: When the blobs show signs of life,

that recipe is selected for replication.

And the inferior recipes are destroyed.

Then, with each generation,

the machine makes small, random changes to the recipe.

After several weeks of trial and error,

Lee's chemical blobs come alive.

They get mobile.

They hunt and capture other droplets.

Cronin: Oh, that one... There was a fusion.

Oh, it's done it. That was nice.

Freeman: They even reproduce.

If you found them outdoors, you would probably mistake them

for little gelatinous life forms,

even though they're not... At least, not yet.

The next thing we want to be able to do

is to feed the droplets on their own

so they can take food naturally from the environment

and grow and get bigger and divide.

Then, we're really on the pathway

to turning this random chemistry into living chemistry,

into biology.

Freeman: Evolutionary biologists

say that DNA in genes gives life its foundational purpose,

to survive and evolve to be better at surviving.

But if Lee is right,

DNA is not the only chemical that can exist for this purpose.

This is why we're really excited, because we can show

that evolution can occur in the natural world

without genetic material.

Freeman: Lee believes we are here for a reason,

a reason shared with all life forms

and the chemicals that constitute them...

To live, to survive, and to evolve.

Cronin: Where there is energy and there is matter,

chemistry transforms into biology over time.

And this is a natural law.

At the deepest level, inside every cell in our body,

we are driven

by the never-ending struggle of chemicals

to make copies of themselves.

But if the only purpose of life is to make more chemicals,

why did we ever become more complex than this?

This guy can replicate dozens of times a day,

reproducing its bag of chemicals

far more efficiently than we can.

And yet, here we are.

What's the reason for bags of chemicals like you and me?

Evolutionary biologist Richard Lensky

at Michigan state university

is a biological time traveler.

So any biologist would love to see the way

the film of life on Earth played out

and to actually watch the transitions that occurred

over these several billion years

and ask, "why did it work out the way it did?"

Freeman: Richard doesn't have billions of years

to watch evolution in action,

but he does have the span of one lifetime,

which he has dedicated

to performing the longest evolutionary experiment

in the history of science.

27 years ago,

Richard plucked

12 genetically identical E. Coli bacteria from a container

and allowed them to start their own populations

in 12 separate worlds.

Ever since, day after day,

he's watched each of the 12 populations multiply

and compete amongst themselves for a limited amount of food.

Lensky: Key part of the experiment is just keeping it going,

day after day after day,

transferring a small amount from each flask

into fresh medium each day.

And the bacteria grow and replicate in that fresh medium

until they run out of the sugar that they grow on.

And then, they sit there

until, the next day, that whole process is repeated.

Freeman: At the end of every day,

he allowed a small sample of the survivors

to continue producing new generations.

Year after year, the daily process went on and on.

In each flask, the cells of bacteria replicate,

passing on tiny, random mutations

to their offspring's DNA.

For the first 15 years of the experiment,

the separated populations evolved pretty much in lockstep,

each strain gradually adapting to this flask environment.

But one night,

one of the colonies had a sudden and dramatic victory

in the arms race of evolution.

One day, we came in and found that one of our flasks

had many more bacteria than the others.

One of the lines of bacteria,

after they had finished the glucose, they said, "hmm,

there's something else to eat."

And that gave them a huge advantage.

Freeman: Overnight, these E. Coli

had switched on new and complex internal machinery

that allowed them to extract energy

from a benign chemical additive.

Armed with this new talent,

they vanquished their competitors.

But when Richard examined the DNA of these E. Coli,

he realized that the mutation that switched on the new talent

was merely the last in a long series.

The others had lain dormant for thousands of generations.

Richard thinks of it as life playing a grand version

of his favorite game, poker.

Lensky: I always liked playing games that involved a mixture

of luck and skill.

Most card games, you've got the shuffling,

and yet poker takes some skill to make a lot of money.

Freeman: For E. Coli and humans alike,

each genetic mutation is like a new card dealt to the species.

If the right hand is made in the right order,

the organism can win big for posterity.

Lensky: In this case, the bacteria have this key mutation,

but it had to happen in the context

where there were other mutations before it.

Freeman: When there is a queen and a king of hearts on the table,

and you have the 10 and Ace of hearts in your hand,

you are set up to potentially make a royal flush,

the most powerful hand in poker.

All you need is for the final card to be a Jack of hearts.

Well, if you were looking for a third seven,

that does you no good at all.

But if you've got the other parts of a royal flush,

you're happy.

Freeman: E. Coli adapt to meet their immediate needs

through genetic mutation.

But some mutations don't have an immediate reward.

They are investments for their distant descendants

so that they can win a big evolutionary jackpot.

It's a purpose that Richard sees mirrored

in the story of his own work and in his own species,

homo sapiens.

Thousands of generations of those who came before him

adapted to meet their immediate needs

but also made tiny contributions

that set Richard up to be a Jack of hearts.

They allowed him to run an experiment

that forever changed humanity's understanding of evolution,

one that would be carried on by his prot�g�s

long after he's gone.

Could this be the purpose of all life,

from simple single cells to human beings?

Well, my wife says my purpose in life is to take out the garbage.

But I do have a couple of other purposes.

I don't know what the deepest possible meaning of life is.

So many happenstances and contingencies

and lucky events went into it.

To me, that's just an amazing story

that I'm one tiny, little speck of,

and I'm very glad to be a part of it.

Freeman: Why do we so desperately search for the meaning of life?

Perhaps it is because we must.

New science suggests that, 50,000 years ago,

human beings dramatically transformed.

And ever since, the survival of our species

depends on each of us finding our unique purpose.

When you look at yourself in the mirror,

do you see the person you truly believe you are?

I'm lucky.

I discovered that I have a love and a talent for acting.

What's your reason for being here?

We're often told that our purpose

can be anything we want it to be.

New evidence suggests that may not be true.

Evolution may have required

that each of us be born with a specific purpose.

What is the meaning of life?

Geneticist Razib Khan says that the answer is different now

than it was for our prehistoric ancestors.

The change began with the explosion of... agriculture

and the rise of an entirely new class of animal.

The wild ancestors of these animals would have

violently attacked Razib for threatening their territory.

But now, these domesticated descendants

cuddle up to him for food and attention.

Razib knows that this difference in behavior

is all in their genes.

Khan: Many of the changes in mammals occur in a group of genes

that are termed neural crest genes,

and basically, it's just a shorthand way

to say that it affects the development of their brain.

And they're more childlike.

Freeman: Every species of animal

has a set of chromosomes made from thousands of genes.

Most of these genes are common to all life.

When early farmers allowed only the tamest offspring to breed,

a specific set of genes mutated,

eventually giving rise to the domestic goat.

[ Goat bleats ]

Those same genes in the wolf

mutated to give rise to the domestic dog.

[ Dog barks ]

Wild aurochs had these genes also.

When they mutated,

domestic cattle came to be.

[ Cow lows ]

In fact, nature uses essentially the same genetic recipe

to turn any wild animal into a domestic.

But one barnyard animal... [ Cat meows ]

Is not like the others.

[ Cat purring ]

Obviously, you know,

unless you live on the planet melmac,

you don't eat cats.

They are not a food animal.

But cats feed on mice,

and mice really,

really are attracted to human granaries.

So it seems entirely likely

that cats were tolerated in early human villages

because they served a useful role

for the nascent farming communities.

Freeman: Cats were not intentionally tamed.

So Razib and his colleagues

looked to their DNA to see how they became so friendly.

Khan: We found in the study

that the comparison to the wildcat,

the domestic cat exhibited many changes in the genome

that have been seen in other domestic organisms,

in particular, the genes

that seem to be involved with docility.

So our study suggested that the cat is, to some extent,

a self-domesticated organism.

Freeman: No farmer set out to breed a domestic cat.

They domesticated themselves.

So that led Razib to wonder, did we humans

also turn ourselves into a domestic species?

Khan: Humans exhibit a lot of changes in our genome

over the last 10,000 years.

My own personal opinion is yes,

you can define humans as a domestic animal.

We live in large groups.

If you took humans individually and put them on an island,

they really couldn't survive.

Freeman: Compared with our wild ancestors 50,000 years ago,

we are more docile, slower,

weaker boned,

and more childlike.

But don't let that get you down.

The apparent downgrades of domestication

have actually given each one of us

a more important purpose in life.

Khan: A hunter-gatherer had to be Jack-of-all-trades because,

probably, there was only 10 to 20 other people

that you interacted with on a regular basis.

When you go up to a village of 500,

you could have a warrior or two,

maybe someone who specialized in healing.

Once you get to the size of cities,

you have whole casts of specialists that do things

that everybody else in the past might have done.

Freeman: When animals are domesticated, individuals in their populations

are more likely to develop exceptional

and specific talents.

Humans are no exception.

It is what has kept our civilization humming along.

Think of a farm.

It takes a lot more than two people to keep it running.

Carpenters, mechanics,

arborists, veterinarians,

the farm relies on all of them

to develop their natural talents into useful skills.

Razib nurtured his gift of intelligence.

And now, his research adds to our collective wisdom.

But he also has another natural talent

that doesn't seem to serve any purpose at all.

The one thing that I can probably do

that impresses people is i can eat hot peppers.

That's the one thing where it's, like,

I'm pretty sure I can beat anybody that I see and meet.

Freeman: Eating this pepper would send most people

scrambling for water.

But for Razib, it's candy.

Our species thrives because each of us feels driven

to purSue our own highly specialized ambition.

But our individual purpose in life may come to haunt us.

It could make our very reason to exist obsolete

and mean lights out for humanity.

Have you ever shared a funny image with a friend online?

[ Camera shutter clicks ]

A meme made you do that.

But memes aren't just Internet jokes.

They are any idea that spreads.

Great ideas, like those of Da Vinci, Einstein, and Buddha,

are the reason humanity has thrived.

In fact, memes may be the real purpose of life.

We may exist not to spread our genes,

but to spread ideas.

As long as the ideas reproduce,

we may be dispensable.

If you ask evolutionary theorist Sue Blackmore

about a universal purpose of all life,

she'll say it's to spread genes.

Blackmore: So, my lovely chickens,

for example, those are kind of living machines

that carry around the genes

and lay an egg and carry on and so on.

And over the centuries of domestication,

they've become nice, fat chickens that lay lots of eggs.

That is what we might call the first replicator.

That information, coded in genes,

in the DNA molecules

in bodies of us, chickens, trees,

that's the first replicator on planet Earth.

Come on, chickens. Come on.

Come on. Come on, chickens. Come on.

Freeman: But humans have one critical difference.

When we developed the capacity for imitation and language,

we became vessels for an additional replicator.

[ Cellphone rings ] Hello?

- Freeman: The meme. - Yeah?

Memes are the cultural equivalent

of genes, if you like.

They are information that's copied from person to person,

person to book.

They encompass all of the habits, skills, stories,

that we pass from person to person.

And they compete to use our brains

to get themselves copied.

And in that way, they evolve.

Freeman: Like genes, memes are selfish replicators.

They spread whatever they can, regardless of the consequences.

Long ago, the meme

of fighting tribal enemies with a stone axe

spread far and wide.

But it wasn't long before a new meme arrived...

The meme of fighting with a bronze sword.

Memes compete to survive.

The best memes get their carriers to copy them,

remember them, and pass them on.

And just like bad genes,

the inferior memes usually end up extinct.

When it comes to memes,

the same evolutionary competition is going on.

The memes that we like,

or that provide something for us,

or that trick us into copying them,

they thrive,

culture fills up with them,

and the rest disappear.

Freeman: We are constantly spreading memes.

A knock on the door is a meme.

A handshake is a meme.

There are countless other ways

to get someone's attention behind a door

and countless ways to greet them.

But in western culture,

these memes stuck.

In fact, Sue and her friends are all spreading a meme

that came from the other side of the globe...

Samba music.

Blackmore: Our samba band is mimetic.

This interesting evolution of samba

because it's evolved in Brazil as street music.

So it's evolved to be loud, active, fun, bright clothes,

to suit the sunshine in the streets.

It comes over here to britain,

and we play the same music,

but it slightly changes to fit in its new niche,

just like animals do when they

evolved into different biological niches.

[ Cellphones chiming, vibrating ]

Freeman: Memes have taken the world by storm.

But now, something new is coming...

The technological replicating meme,

or the treme.

Blackmore: Now, we have all this amazing silicon-based technology,

with digital information flowing about all over the place.

This is a new kind of copying.

It's this digital information that is competing

to use the resources of all this information technology

that we've created.

Freeman: Live music is a meme,

but music on your smartphone is a treme

because technology can effortlessly copy and share it.

Tremes can spread fast and wide.

They are often spread by computers that don't need humans

to like, share, or tweet them.

Sue thinks that, someday,

when our computers can spread and copy tremes

more effectively than we can,

we will all lose our uniquely human reason for existing.

It sounds like a dystopian nightmare,

but it may be something we willingly choose.

Blackmore: I think it's important to know

that this wouldn't be happening if a lot of it weren't good

because we wouldn't let it happen.

The only reason that all these tremes

can take off the way they do is because we want more music,

we want more books,

we want more fun videos, informative videos.

And because these things

are chosen by us and we like them,

we are willingly producing all the hardware

and all the software that is gradually taking over.

Freeman: So, is this the ultimate purpose

of 3.5 billion years of life on Earth,

to be replaced

by ever more sophisticated information replicators?

It sounds strange.

But as physicists begin to examine life's purpose,

they are finding that life and information

could be one and the same.

What is the ultimate purpose of life?

Is it to be cast aside and replaced by machines

whose only pursuit is information?

Well...

Some scientists now believe...

That we have always been nothing more than evolving algorithms.

Physicist Sara Walker is crafting a new definition

and understanding of life.

I think about biological systems as physical systems.

But they're a unique kind of physical system.

And they're uniquely defined, really,

by the way they handle information.

Freeman: Sara defines life as a self-replicating algorithm,

a computational machine that processes information

and then makes copies of itself.

[ Glass shatters ]

[ Glass shatters ]

It's a concept that really hits home for Sara...

Now that she's made a little algorithm of her own.

What's amazing about having a small child in your home

is how they learn things.

Look at that big mess. What is all that stuff?

So he's really just like an information junkie,

running around the house being like, "what is this,

what is this, what is this?"

And so it's pretty fun.

Freeman: Sara sees her son, corwin,

as a collection of logical processes

working hard to solve the problems of staying alive...

In other words, an algorithm.

And everything he does,

he's processing information about the world he lives in,

even when he's doing his best to just eat lunch.

Eating is definitely information processing.

You're taking chemicals from your environment,

and you're ingesting them, and your body has to actually

be able to figure out how to use those chemicals

for the right kind of chemical reactions.

Freeman: Sara believes that corwin

and all of us humans came to be because evolution

guided life to become better information processors.

Walker: I do think evolution has an arrow.

I do think it actually evolves toward more complex systems

and better information processing systems.

Freeman: Evolution's arrow locked living organisms

into an information-gathering arms race.

Vision and hearing get sharper.

Teeth and claws get better at grabbing prey

and sampling the information in its meat.

Sara believes everything we do follows this evolutionary drive

to gather and decode more information.

Yay, good job, corwin!

Freeman: In fact,

even the technology that we create

follows the same pattern.

So one thing that you might think we humans want to do

is remember what our kids look like when they're little.

So originally,

people used to capture that kind of memory or image

by actually painting it, right?

And then, we figured out something very clever,

which is that we can actually just capture the light and store

that image from the light we capture.

[ Camera shutter clicks ]

And those are cameras.

Freeman: The information-gathering algorithms of cameras

are evolving, too.

Digital cameras evolved to process more information.

They record full color

and even recognize when a face is present.

Then came the smartphone camera,

which can even figure out who that person is.

Walker: And we've now evolved technology

which is helping us process information even better.

Not only humans fit in this framework,

but even our modern social systems

and our technological systems are sort of a natural outcome

of the way the universe operates.

Freeman: Biology and technology are locked together

in a joint quest for more information.

In fact, this could be the ultimate purpose of life.

Walker: Evolution is really about capturing

more information about the environment.

And through that process,

the environment becomes more complex.

Living systems fundamentally change

the universe that they're in and use that

to do the kind of amazing things

that we, as biological systems, do.

Perhaps that actually is the purpose of living systems,

is to figure out how the universe actually works.

So living systems, in this kind of framework,

are somewhat fundamental to the universe

because they're the way the universe figures itself out.

Freeman: Life is an epic quest for knowledge.

I'd love to think we humans will reach the end of this long road

and know everything there is to know about the universe.

But evolution may have other plans.

Our thirst for information

could soon wipe us from the face of the planet.

It is common to think of evolution

as progress,

species locked in a struggle

to become the fastest, the strongest,

and the tallest,

reach ever-higher levels of complexity and skill.

But life is not an ever-growing edifice

of biological refinement.

It's a series of dramatic collapses.

Jim Sethna is a physicist at Cornell.

He researches the fine line

separating success from catastrophic failure.

These rice krispies could sit on the shelf for years.

But expose them to milk,

and they crackle as they collapse into mush.

Most of the systems we see crackling noise,

it's at a transition between two different states.

So in the rice krispies,

it's a transition between the dry state

and the soaked state.

Freeman: Jim is interested in how any system behaves

when it sits on the knife's edge

between stability and crackling apart,

a so-called critical point.

A burning log crackles

as pockets of air, small and large,

expand in rapid succession.

Mountain snow builds up

until a tiny movement escalates into a crackling avalanche.

Jim and a growing group of scientists

believe that our own bodies

are also poised at the edge of collapse.

Ironically, it's what has kept us out of harm's way

for millions of years.

[ Car door closes ]

Think about our sense of hearing.

Evolution pushed it so close to a tipping point

that a tiny change in the air around us

causes a cascade of thoughts,

senses, and images in your brain.

Your hearing is so finely tuned

that, if it were any more sensitive,

you would be sensitive to the random motions

of air molecules hitting your eardrum.

Freeman: Our eyes are even more sensitive.

A single photon can send billions of neurons

crackling into overdrive

and conjure up a phantom that isn't there.

Species have developed all kinds of senses,

and each of them has been, over billions of years,

honed to the absolute limits.

Freeman: In fact, being poised between function and collapse

is the normal state

of every functioning cell in your body.

Jim and his colleagues,

eshan mitra and Sarah Shelby, are investigating why.

The membrane of a human cell exists on a knife's edge.

When there's a tiny change in the outside environment,

the structure of its fats and proteins instantly collapses

and rearranges itself.

Sethna: Its cells have to be very finely tuned

to distinguish the things it wants to expel.

They sit near this critical point

in order to make it easy

for the cell to respond sensitively and quickly

to new information about its outside.

Freeman: The membranes of cells exist on the border of disorder.

The same is true for the systems of cells

that comprise our senses.

And as Jim is learning,

entire systems of organisms can also teeter on the edge.

Consider the mesmerizing movements

of flocks of starlings.

It is virtually impossible

for a predator to feast on this flock.

The movement of one bird

changes the entire shape of the murmuration.

Each bird is sort of programmed in its head

to fly in roughly the same direction as its neighbors.

But it's tuned in this way

so that they're at the border of stability,

and that is what makes them respond quickly and efficiently

to their environment.

Freeman: Dinosaurs were also poised at the knife's edge.

Their massive size optimized them to weather any predators.

But optimization always comes at a price.

Sethna: When you optimize things,

they naturally end up at some kind of critical point

because you're trying to milk as much as possible out of a system

before you hit a catastrophe.

Freeman: A change in climate eradicated the dinosaur.

A single miscue can collapse a murmuration.

A few aberrant neurons

can trigger an epileptic fit inside the human brain.

A cell's membrane can collapse into a state of disarray

and die.

And human life itself

may also be poised for a dramatic collapse.

After all,

we constantly optimize ourselves to the point of failure

and hold on as long as we can.

Jim, however, is hopeful.

In spite of our never-ending quest to better ourselves,

we have one critical talent to prevent catastrophe.

We have an unusual advantage that we are a system

that's at a critical point when it's self-aware,

that is able to analyze the problems

and avoid the disasters,

which are getting more serious

if we get better at controlling the world.

Freeman: If lives are built to so easily come crackling apart,

what's the point?

This scientist says that it's really quite simple.

The point of it all

is to discover the point of it all

because when you think about purpose,

everything changes.

Is humanity on a path

to knowing all there is to know about the universe?

Or are we bound to be replaced?

It's hard to think about our ultimate purpose

when everyday life can be filled with so many hurdles.

But that may be a mistake

because taking the time to think about why we are really here

could be what makes those daily struggles much easier.

We call came from somewhere,

and we all have somewhere we want to go.

Psychologist Tony burrow

has thought about this journey his entire life,

which began with his atypical family.

When I was two months old,

I was adopted by two white parents.

When you have parents

who are of different racial background than you,

it gives you a lot of opportunities

to talk about race.

I wanted to know... How do people who experience

chronic forms of discrimination and oppression

deal with this?

And for me, this gives rise to questions of purpose.

Freeman: Hiking is walking with purpose.

There is an end goal,

but that's not why people like Tony

go through all the trouble of reaching the trail's end.

Tony thinks that having a purpose in life

is not only necessary for happiness,

it subconsciously changes how we perceive ourselves and the world

around us.

Tony is a professor at Cornell university,

where students every morning face an infamous challenge,

a figurative and literal uphill climb... the slope.

This 500-foot-long ascent

is the wall between a warm, cozy bed

and a long day of intense classwork.

Burrow: So a couple of semesters ago,

a student came up to me after class and said, "professor,

I'm really sorry I couldn't make it to class last Tuesday."

And he said, "you know, I really just couldn't get up the slope.

I didn't have the energy."

And I started to think about it.

Was this a question of motivation?

Excuse me.

Do you have a few minutes to participate in a study?

Oh, sure.

Freeman: As students begin their journey,

he asks them what goal they want to accomplish that day.

At the top of the slope,

a researcher asks them how difficult the climb was

and to estimate its steepness.

Burrow: So we found a strong and reliable relationship

between the angle that they perceived

after ascending the slope

and the degree of effort

that they said was necessary to get to the top.

Freeman: The steeper you feel the slope is,

the more effort you think you've expended to climb it.

No big surprise there.

But Tony adds a twist.

He asks some subjects, at the bottom of the hill,

to write not about their goal for the day,

but their long-term purpose in life.

Burrow: A goal is terminal.

It's something that you can accomplish.

A sense of purpose is a broader framework

that describes and orients who one approaches the goals

that they've laid out for themselves.

So we don't think of purpose

as something that you can actually accomplish.

Freeman: Students prompted to think about their life's purpose

still thought the climb was just as brutal as the other group,

but they didn't mind it

while the students contemplating their daily goals

often struggled.

The purpose-minded group

tackled the hill with a sense of purpose.

Tony believes having a purpose frees us

from feeling the full weight of the obstacles in front of us,

whether a literal hill we must climb

or a personal challenge we must overcome.

Burrow: I think what purpose does, first and foremost,

is reminds people that where they are right now

is not forever,

that they're heading in a particular direction.

And just like when we're on a hike,

it doesn't really matter

if you're confronted with a challenge.

The goal is to continue to hike.

And for individuals who can cultivate a sense of purpose,

they may begin to see other life challenges in the same way.

Freeman: In our lives, having a purpose

can flatten the mountains between where we are

and where we're going.

Are we here, now, alive, for a reason?

People like Ann frank and Nelson mandela

asked that question in their darkest hours.

Their determination to make a reason for life

gave them the strength to carry on

and the power to shape the world.

Life may not have one unifying purpose,

but that shouldn't stop us all from searching for it.

Finding a reason and believing in it

may be all the purpose that we need.

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