Phu đề video History of Word in two hour

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    00:00:01 What if we could tell you everything, the entire history of the world?

    00:00:07 Now, what if we told you, we could do it in just two hours?

    00:00:12 We're going to tell the whole story, from the Big Bang to the present day.

    00:00:18 How the planet prepared, for the rise of man.

    00:00:22 How the Stone Age, led to the steam engine.

    00:00:27 How the first seeds sprouted, into cities and civilizations.

    00:00:33 Everything is connected, and the path leads to you.

    00:00:39 lt took history 1 3.7 billion years to unfold.

    00:00:43 We'll show you everything you, need to know in the next two hours.

    00:01:06 This is our infant universe.

    00:01:09 Everything that will ever exist,everything that will ever happen,

    00:01:14 all begins here, within this tiny bundle of energy,smaller than an atom.

    00:01:23 And right now, history as we know it is about to mysteriously begin.

    00:01:30 For reasons we may never know,our universe suddenly erupts.

    00:01:45 ln a millionth of a millionth, of a millionth of a millionth

    00:01:49 of a millionth, of a millionth of a second,

    00:01:52 it went from a size, smaller than an atom

    00:01:55 to bigger than a galaxy.

    00:02:04 What you're seeing is energy,

    00:02:07 and it's one key to understanding, everything that will unfold in the next two hours.

    00:02:14 Within a fraction of a second, the Big Bang creates, all the energy that will ever exist,

    00:02:21 all the energy that will power the stars,

    00:02:24 that will fuel, anything that ever lives.

    00:02:28 All the energy, that you will ever consume

    00:02:31 dates back to the beginning of time. When you put gas into your car,

    00:02:40 you're tapping energy, that was created during the Big Bang.

    00:02:46 You're tapping, the energy of the universe itself.

    00:02:58 We're only a few minutes into our two-hourjourney,but already 380,000 years havepassed. You are about to witness the birth of your original ancestors, the first atoms.

    00:03:20 This is hydrogen.

    00:03:23 The universe will use it to make

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    everything in the world around us.

    00:03:27

    00:03:29 Hydrogen is like a baseball team.

    00:03:31

    00:03:32 You say, "What player do l want

    to start my team with?"

    00:03:34

    00:03:34 Well, if l want to start a universe,

    l want to start it with hydrogen.

    00:03:37

    00:03:37 Because from that, with a lot of heat

    and a lot of pressure,

    00:03:39

    00:03:39 you can build more kinds of atoms.

    00:03:41

    00:03:43 The first atoms

    blast through the early universe.

    00:03:46

    00:03:49 And luckily for us,

    they don't spread out evenly,

    00:03:52

    00:03:54 because in those tiny pockets

    with more atoms,

    00:03:57

    00:03:57 gravity, the great sculptor

    of the early universe,

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    00:04:01 begins to work its magic.

    00:04:03

    00:04:10 The first galaxies

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    are beginning to form,

    00:04:13

    00:04:14 revealing a timeless secret

    of the universe.

    00:04:17

    00:04:23 Throughout history,

    00:04:24

    00:04:24 whenever more matter and energy

    can be drawn together in one place,

    00:04:28

    00:04:28 more complex things can emerge.

    00:04:31

    00:04:32 We have all of these urban centers

    around the planet

    00:04:36

    00:04:36 where so much creativity, so much art,

    so much science,

    00:04:40

    00:04:40 so much culture came about

    00:04:42

    00:04:43 because of all these opportunities for

    things to interact with each other.

    00:04:46

    00:04:47 Really, in a sense, where

    there is stuff, new stuff can develop.

    00:04:51

    00:04:51 And where there isn't anything,

    nothing much can develop.

    00:04:54

    00:05:01 300 million years after the Big Bang,

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    00:05:04

    00:05:05 inside of forming galaxies,

    00:05:08

    00:05:09 gravity continues to squeeze together

    clouds of gas and dust,

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    00:05:14 causing pressure and heat

    to violently rise.

    00:05:17

    00:05:21 When the temperature reaches

    1 8 million degrees Fahrenheit,

    00:05:25

    00:05:25 hydrogen atoms slam together,

    creating a new element, helium,

    00:05:30

    00:05:30 and radiating bursts of energy.

    00:05:32

    00:05:34 The first stars are born.

    00:05:37

    00:05:39 Suddenly there were

    these new beacons of light

    00:05:42

    00:05:42 shining forth,

    pouring energy into the universe.

    00:05:46

    00:05:48 Let there be light.

    00:05:49

    00:05:51 But something is missing

    from this early universe.

    00:05:54

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    00:05:54 There are billions of stars,

    yet not a single planet.

    00:05:58

    00:05:59 To form planets and eventually people,

    00:06:03

    00:06:03 to take the next leap that would

    make all of history possible,

    00:06:06

    00:06:07 the universe needs more to work with

    than just hydrogen and helium.

    00:06:11

    00:06:12 The complicated elements,

    00:06:14

    00:06:14 the heavier things

    that we build stuff out of,

    00:06:16

    00:06:16 for example, iron or life built out

    of carbon and things like that,

    00:06:21

    00:06:21 they're actually

    manufactured in stars.

    00:06:23

    00:06:23 We may see stars like our own sun

    as sources of light,

    00:06:27

    00:06:27 but there is something bigger

    happening deep inside.

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    00:06:31 Stars are element factories.

    00:06:34

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    00:06:34 They fuse hydrogen into helium,

    helium into lithium,

    00:06:38

    00:06:38 forging 25 of the most common elements

    we'll need to live,

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    00:06:42 including carbon, oxygen,

    nitrogen, and iron.

    00:06:46

    00:06:48 So more than 1 2 billion years ago,

    00:06:51

    00:06:51 stars are already creating the element

    that will spur the lron Age,

    00:06:56

    00:06:56 allow for the building of cities

    00:06:59

    00:06:59 and the creation of some of mankind's

    most famous monuments.

    00:07:03

    00:07:08 But a look at the Statue of Liberty

    00:07:10

    00:07:10 reveals the next challenge

    awaiting the early universe.

    00:07:13

    00:07:14 While the statue's frame is iron,

    00:07:17

    00:07:17 her skin requires an element

    too heavy to be made in stars.

    00:07:21

    00:07:27 For Lady Liberty to have

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    material for her skin,

    00:07:30

    00:07:32 for there to be

    gold for wedding rings,

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    00:07:36 or uranium for nuclear reactors,

    00:07:39

    00:07:39 some elements had

    to be created another way.

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    00:07:42 Stars don't have

    enough energy to do the job,

    00:07:45

    00:07:46 but if the element factory

    isn't powerful enough,

    00:07:49

    00:07:49 how about blowing up the factory?

    00:07:52

    00:07:56 Just a few million years

    after the first stars formed,

    00:07:59

    00:07:59 some of them exploded.

    00:08:01

    00:08:02 These explosions, known as supernovas,

    00:08:06

    00:08:06 are the biggest blasts in the universe

    since the Big Bang,

    00:08:09

    00:08:09 providing the extra boost of energy

    needed to fuse heavier elements.

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    00:09:09

    00:09:10 Copper and tin, Bronze Age.

    00:09:12

    00:09:12 Without supernovas,

    there's no Bronze Age.

    00:09:15

    00:09:16 Go to any supermarket

    and buy a multivitamin

    00:09:17

    00:09:19 and go and look in the ingredients.

    00:09:20

    00:09:20 You'll find copper. You'll find zinc.

    You'll find selenium.

    00:09:23

    00:09:23 You'll find all sorts of elements

    that can only be made in a supernova.

    00:09:28

    00:09:29 The elements made by stars

    will become the seeds of life on Earth

    00:09:34

    00:09:34 and the drivers of human history.

    00:09:37

    00:09:38 But the journey has just begun.

    00:09:40

    00:09:41 Before there can be life, the universe

    has to build us a suitable home.

    00:09:47

    00:09:49 To build a proper house, you have to

    assemble the right materials

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    00:09:53 all in one place.

    00:09:55

    00:09:57 Now when planets form,

    it's the same thing,

    00:10:00

    00:10:00 it's the materials

    that you have at hand

    00:10:03

    00:10:03 that's gonna dictate the kind of house

    that your planet's gonna be.

    00:10:06

    00:10:07 To get enough of the right material

    in the right place all at once

    00:10:11

    00:10:11 takes a very long time.

    00:10:14

    00:10:14 Over the next eight billion years,

    00:10:17

    00:10:17 more than half of history

    as we know it,

    00:10:19

    00:10:19 the element factories

    continue their work.

    00:10:22

    00:10:23 Stars explode and are reborn,

    00:10:27

    00:10:30 each generation with

    more heavy elements than the last.

    00:10:33

    00:10:37 Until 4.6 billion years ago.

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    00:10:40

    00:10:41 Finally there are

    enough materials gathered

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    00:10:44 for the next step on the path to us.

    00:10:47

    00:10:53 A new star is born.

    00:10:55

    00:10:56 This is our sun.

    00:10:58

    00:10:58 lt's so massive that it's gathered up

    00:11:00

    00:11:00 99.9% of the gas and dust

    in the solar system,

    00:11:04

    00:11:05 but there's still

    just enough left behind

    00:11:07

    00:11:07 for gravity to build

    some other things,

    00:11:10

    00:11:10 like planets.

    00:11:12

    00:11:13 The third one out from this star

    will be our home.

    00:11:16

    00:11:19 By the time Earth emerges just over

    four and a half billion years ago,

    00:11:23

    00:11:23 two-thirds of the history

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    of the universe has already passed.

    00:11:27

    00:11:31 The first sunrises sweep

    across a foreboding alien planet,

    00:11:36

    00:11:37 a world spinning so rapidly

    that a day lasts only six hours.

    00:11:41

    00:11:45 When you go back to the early Earth,

    right after the planet formed,

    00:11:49

    00:11:50 you really have to think

    of the Earth as another planet.

    00:11:53

    00:11:54 The sun would have looked out

    over a hellacious scene

    00:11:57

    00:11:59 ofjust molten lava.

    00:12:00

    00:12:04 And in places you would

    see rafts of black volcanic rock.

    00:12:09

    00:12:11 Within the liquefied rock

    the elements are all in a jumble.

    00:12:15

    00:12:16 Something has to

    bring order out of this chaos.

    00:12:20

    00:12:20 And once again

    that something is gravity.

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    00:12:23

    00:12:25 Lighter material

    drifts toward the surface

    00:12:28

    00:12:28 and forms a solid crust,

    00:12:30

    00:12:33 while heavier material

    sinks toward the center,

    00:12:36

    00:12:36 forming a molten iron-nickel core.

    00:12:39

    00:12:40 This churning liquid metal

    00:12:42

    00:12:42 creates a magnetic field

    that reaches out into space.

    00:12:45

    00:12:46 Like a force field,

    it will protect our future home

    00:12:49

    00:12:49 from the sun's

    deadly charged particles.

    00:12:52

    00:12:52 Soon this magnetic field

    will allow for life to grow,

    00:12:56

    00:12:56 and later, guide the explorers who

    will connect two halves of the world.

    00:13:00

    00:13:01 But for all this to unfold, the Earth

    will need a critical partner.

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    00:13:06

    00:13:14 Four and a half billion years ago,

    00:13:16

    00:13:17 an object the size of Mars

    smashes into the planet

    00:13:20

    00:13:20 at 25,000 miles per hour.

    00:13:23

    00:13:29 Earth swallows up

    much of the impactor.

    00:13:31

    00:13:39 But a spray of molten debris

    is whipped off into space.

    00:13:43

    00:13:44 Within as little as a year,

    gravity gathers this debris

    00:13:48

    00:13:48 into a secondary sphere

    in orbit around the Earth,

    00:13:51

    00:13:52 where it has been ever since.

    00:13:54

    00:13:57 The formation of the moon

    00:13:58

    00:13:58 was an incredibly important event

    in Earth's history.

    00:14:01

    00:14:02 And in fact, its creation,

    over four billion years ago,

    00:14:03

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    00:14:06 is really important to

    the Earth's climate today.

    00:14:08

    00:14:08 The moon keeps Earth steady.

    00:14:11

    00:14:11 lts gravitational pull

    prevents the planet from wobbling,

    00:14:15

    00:14:15 saving us from wild climate swings.

    00:14:18

    00:14:18 And the collision that formed the moon

    leaves Earth tilted on its axis,

    00:14:23

    00:14:24 giving the planet

    a key ingredient to life,

    00:14:26

    00:14:27 seasons.

    00:14:29

    00:14:32 Having seasons is very, very important

    00:14:34

    00:14:34 for the evolution of life

    on the Earth,

    00:14:36

    00:14:36 and having some stability

    in the tilt of those axes,

    00:14:40

    00:14:40 that's very, very important also

    for maintaining life on the Earth.

    00:14:43

    00:14:46 The moon's gravity

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    also begins to slow Earth's rotation,

    00:14:51

    00:14:51 which will eventually lengthen

    our days from six hours to 24.

    00:14:57

    00:15:07 4.4 billion years ago.

    00:15:10

    00:15:11 lt's too hot on Earth

    for liquid water to exist,

    00:15:15

    00:15:15 but there's water vapor,

    steam in the atmosphere.

    00:15:19

    00:15:21 The trick is

    how to get it out of the sky.

    00:15:24

    00:15:24 Onto any world where you hope

    to have life, a little rain must fall.

    00:15:29

    00:15:36 For millions of years

    as the planet cools, rain pours down,

    00:15:41

    00:15:41 forming puddles, lakes,

    and eventually our oceans.

    00:15:47

    00:15:50 By 3.8 billion years ago,

    00:15:53

    00:15:53 our planet has a moon

    and permanent oceans,

    00:15:57

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    00:15:57 but it hardly resembles

    the place we now call home.

    00:16:00

    00:16:02 To become the stage

    for all of human history,

    00:16:05

    00:16:05 Earth needs an oxygen-rich atmosphere,

    00:16:08

    00:16:08 fertile continents

    for people to discover and develop.

    00:16:12

    00:16:12 Who will create our modern world?

    00:16:15

    00:16:15 There's a trillion of them

    crawling on your skin right now.

    00:16:19

    00:16:28 We're telling the history of the world

    in two hours,

    00:16:31

    00:16:31 from the Big Bang to the present day.

    00:16:35

    00:16:35 And our modern world

    holds important clues to the story.

    00:16:39

    00:16:39 ln fact, structures like this

    00:16:42

    00:16:42 hide a mysterious link

    to the first life on Earth.

    00:16:46

    00:16:53 3.8 billion years ago,

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    00:16:55

    00:16:57 beneath the surface

    of our primeval oceans,

    00:17:00

    00:17:02 a revolution is taking place.

    00:17:05

    00:17:09 Six simple elements,

    including hydrogen from the Big Bang,

    00:17:13

    00:17:13 and oxygen, carbon,

    and nitrogen created by stars,

    00:17:17

    00:17:17 have combined

    to form the key substances

    00:17:19

    00:17:19 that will make up all life,

    including us.

    00:17:23

    00:17:26 The most spectacular is DNA.

    00:17:29

    00:17:31 Within its spirals

    hide the secret codes of life.

    00:17:34

    00:17:37 700,000 years

    after the planet first formed,

    00:17:41

    00:17:42 life on Earth begins.

    00:17:44

    00:17:46 We stand

    not on the shoulders of giants,

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    00:17:49

    00:17:49 but of tiny organisms, bacteria.

    00:17:52

    00:17:55 We're very egocentric. We think

    that we animals run the world,

    00:17:59

    00:17:59 but in fact we are very late entrants.

    00:18:02

    00:18:03 lt was an empire of bacteria

    long before animals.

    00:18:06

    00:18:06 Animals come along,

    00:18:07

    00:18:07 and we like to think

    that we wiped out that empire.

    00:18:11

    00:18:11 Well, we would be dead

    if we wiped out that empire.

    00:18:14

    00:18:15 l have within me

    an entire zoo of bacteria.

    00:18:18

    00:18:19 ln fact, each one of us

    00:18:21

    00:18:21 has more bacteria living in our bodies

    than there are people on the planet.

    00:18:26

    00:18:28 For billions of years,

    00:18:30

    00:18:30 microbes like these

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    will have Earth to themselves.

    00:18:34

    00:18:36 Like our infant universe,

    00:18:38

    00:18:38 the first life is small, simple,

    and full of possibilities.

    00:18:43

    00:18:44 The secret of how it explodes

    00:18:45

    00:18:45 into all of the incredible forms

    we see today, including us,

    00:18:50

    00:18:50 goes back to the beginning of time.

    00:18:52

    00:18:53 As we've seen,

    00:18:54

    00:18:54 all the energy that will ever exist

    was created in the Big Bang.

    00:18:58

    00:19:00 All creatures need to grab their share

    of this energy to survive.

    00:19:05

    00:19:05 The more we harness,

    the more efficiently we use it,

    00:19:09

    00:19:09 the more complex we can become.

    00:19:11

    00:19:12 And almost all of our share

    of the Big Bang's energy

    00:19:15

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    00:19:15 is beamed to us by the sun.

    00:19:18

    00:19:21 Two and a half billion years ago,

    00:19:23

    00:19:24 some very special bacteria

    00:19:26

    00:19:26 figure out how to

    consume the sun's energy to live.

    00:19:30

    00:19:32 ln doing this, they also create

    00:19:34

    00:19:35 the most important waste product

    in the history of the world,

    00:19:38

    00:19:40 oxygen.

    00:19:42

    00:19:45 Soon, oxygen will remake our world,

    00:19:47

    00:19:48 but first,

    it has another important job to do.

    00:19:51

    00:19:53 Earth's ancient seas

    are full of iron particles,

    00:19:56

    00:19:56 and everyone knows

    what happens when oxygen meets iron.

    00:20:01

    00:20:03 Here l'm a little bacterium.

    l've produced this oxygen molecule,

    00:20:06

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    00:20:06 and here's a big piece

    of iron and clump, l rust it.

    00:20:09

    00:20:12 The rusted iron

    collects on the sea floor.

    00:20:14

    00:20:17 Billions of years later,

    these huge deposits will be raised up

    00:20:22

    00:20:22 to become major sources

    of the world's iron and steel.

    00:20:26

    00:20:30 lt was these iron deposits

    00:20:31

    00:20:31 that later on

    drove the lndustrial Revolution.

    00:20:34

    00:20:36 ln this way, the Brooklyn Bridge

    00:20:38

    00:20:39 and the other early landmarks

    of the lndustrial Age

    00:20:42

    00:20:42 are a direct link to

    some of the first life forms on Earth.

    00:20:46

    00:20:49 Once there's no more iron

    left in the sea to rust,

    00:20:52

    00:20:52 these ancient bacteria

    have a mission to complete.

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    00:20:56

    00:20:56 They create so much oxygen

    00:20:59

    00:20:59 that it fills the oceans

    and escapes into the atmosphere.

    00:21:04

    00:21:06 And from then on

    we have a very different planet

    00:21:09

    00:21:09 from all the other planets

    in the solar system.

    00:21:11

    00:21:12 Now, life takes a giant leap.

    00:21:14

    00:21:15 For the first time,

    some bacteria learn to live on oxygen.

    00:21:19

    00:21:21 Every human breath is a ritual

    two and a half billion years old.

    00:21:26

    00:21:29 Life tends to stick with what works

    00:21:30

    00:21:32 even over the course of

    billions of years.

    00:21:33

    00:21:34 Oxygen is a game changer.

    00:21:36

    00:21:36 By taming its power,

    00:21:38

    00:21:38 life has found

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    a better way to energize itself.

    00:21:41

    00:21:41 Twenty times more efficient

    than anything used on Earth before.

    00:21:45

    00:21:46 What life does

    with all this new energy

    00:21:49

    00:21:49 will be the story that leads to us.

    00:21:51

    00:21:58 Over the next two billion years,

    life becomes more complex.

    00:22:02

    00:22:05 Skies become blue,

    00:22:07

    00:22:08 and so do the oceans

    that reflect them.

    00:22:11

    00:22:12 Large, solid continents appear.

    00:22:15

    00:22:15 Earth is beginning to look

    more like the place we now call home.

    00:22:19

    00:22:28 550 million years ago,

    00:22:30

    00:22:31 as the planet celebrates

    its four billionth birthday,

    00:22:35

    00:22:36 oxygen levels in the atmosphere have

    risen from next to nothing

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    00:22:39

    00:22:40 to as much as 1 3%.

    00:22:42

    00:22:44 Take a deep breath,

    00:22:46

    00:22:46 because life on Earth

    is about to go wild.

    00:22:49

    00:22:55 This is the Cambrian explosion,

    biology's version of the Big Bang.

    00:23:00

    00:23:02 Right after you have abundant oxygen,

    you get size and complexity.

    00:23:05

    00:23:07 And oxygen lets you do that.

    00:23:10

    00:23:13 lt's in this breathtaking span

    of roughly 30 million years

    00:23:17

    00:23:17 that most of the

    major animal groups evolve.

    00:23:20

    00:23:22 By 500 million years ago, the first

    bony fish have evolved in the seas.

    00:23:28

    00:23:29 These fish are our direct ancestors.

    00:23:31

    00:23:32 Though they look nothing like us,

    00:23:34

    00:23:34 they evolve the body parts that will

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    make our own bodies possible,

    00:23:38

    00:23:38 including a spine,

    and a mouth with jaws and teeth.

    00:23:42

    00:23:44 We owe a great deal

    to our fish ancestors.

    00:23:46

    00:23:46 ln fact, all vertebrates today

    00:23:47

    00:23:47 really represent modifications

    of the original fish body plan.

    00:23:50

    00:23:53 For the first four billion years

    of Earth's history,

    00:23:56

    00:23:56 plants and animals

    have stuck to the seas.

    00:23:59

    00:24:02 But that all begins to change.

    00:24:04

    00:24:04 With oxygen comes an ozone layer,

    00:24:07

    00:24:07 protecting us from

    dangerous radiation.

    00:24:10

    00:24:13 Plants make the move first.

    00:24:15

    00:24:25 Around 400 million years ago,

    animals are ready to take the leap.

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    00:24:30

    00:24:32 Among the first ashore

    are the amphibians,

    00:24:35

    00:24:35 whose descendants will include us.

    00:24:38

    00:24:39 The most amazing thing about animal

    evolution ever, for me personally,

    00:24:42

    00:24:44 is that moment that first amphibian

    00:24:46

    00:24:46 walks out of the primeval ocean

    onto land

    00:24:50

    00:24:50 and takes a big gulp of air.

    00:24:52

    00:24:54 Kind of like great-great-great-

    great-great-great grandpa

    00:24:57

    00:24:57 coming out of the ocean

    and seeing this fantastic world.

    00:25:01

    00:25:03 And it's like, "Hey! l can live here.

    00:25:05

    00:25:05 "Look at those trees.

    Look at those bugs.

    00:25:06

    00:25:06 "There's food here. l can do this."

    00:25:08

    00:25:14 Eventually, humans will conquer

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    every imaginable terrain.

    00:25:18

    00:25:21 But before we can do that,

    00:25:23

    00:25:23 our ancestors must first cut their

    final tie to the water,

    00:25:27

    00:25:28 mating season.

    00:25:29

    00:25:33 Like modern frogs,

    00:25:35

    00:25:35 they have jelly-like eggs

    that would dry out on land.

    00:25:38

    00:25:41 But some amphibians

    eventually solve the problem.

    00:25:44

    00:25:45 They evolve a new form of egg

    00:25:47

    00:25:48 with a shell

    that keeps the moisture in.

    00:25:50

    00:25:51 This allows us

    to carry the ocean with us onto land

    00:25:55

    00:25:56 and signals the evolution

    of amphibians into reptiles.

    00:26:01

    00:26:01 You could be 300, 400, 500,

    1 ,000 miles away from water

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    00:26:06

    00:26:06 and still have the water in that egg

    in order to birth.

    00:26:09

    00:26:10 That is the key.

    00:26:11

    00:26:12 lt cuts that final tie to the ocean.

    00:26:15

    00:26:16 That way we could colonize

    the rest of the land.

    00:26:19

    00:26:33 300 million years ago, life flourishes

    in massive tropical swamps

    00:26:40

    00:26:40 where planet Earth

    is cooking up a surprise.

    00:26:43

    00:26:44 As plants die here,

    00:26:46

    00:26:47 they are buried, compacted,

    and cooked.

    00:26:52

    00:26:53 Energy created in the Big Bang

    00:26:55

    00:26:55 and radiated by the sun

    to plants on Earth

    00:26:59

    00:27:00 is now locked away underground

    as coal,

    00:27:05

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    00:27:05 a gift to be opened by human beings

    millions of years in the future.

    00:27:10

    00:27:19 250 million years ago,

    00:27:21

    00:27:23 an apocalypse unfolds.

    00:27:25

    00:27:26 The biggest spike in volcanic activity

    since the early days of the planet.

    00:27:31

    00:27:32 The atmosphere is choked

    with carbon dioxide,

    00:27:36

    00:27:36 and the diversity of animal life

    spawned in the Cambrian explosion

    00:27:40

    00:27:40 is stopped dead in its tracks.

    00:27:42

    00:27:46 More than 70% of all species on Earth

    go extinct

    00:27:50

    00:27:50 in the worst mass die-off in history,

    the Permian extinction.

    00:27:55

    00:27:58 Extinction is a recurring character

    in the story of planet Earth.

    00:28:02

    00:28:04 Five times

    in the last 500 million years,

    00:28:07

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    00:28:07 some cataclysm

    wiped out the dominant species.

    00:28:11

    00:28:12 lt's a reshuffling of the deck that

    allows new creatures to take hold.

    00:28:16

    00:28:17 New creatures like the dinosaurs.

    00:28:21

    00:28:24 Dinosaurs will reign

    for the next 1 60 million years.

    00:28:28

    00:28:30 During that time,

    the first hardwood forests appear.

    00:28:34

    00:28:36 And after

    more than four billion years,

    00:28:39

    00:28:39 the moon's gravity finally settles

    Earth into a 24-hour day.

    00:28:44

    00:28:47 At the start of the dinosaur era,

    00:28:48

    00:28:49 the continents are clustered together

    00:28:51

    00:28:51 into a single landmass

    we call Pangaea.

    00:28:53

    00:28:54 But now they start to break apart.

    00:28:57

    00:29:00 Africa separates from South America.

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    00:29:03

    00:29:04 The vast Atlantic Ocean opens up,

    00:29:06

    00:29:07 creating what will become one of the

    defining barriers of human history,

    00:29:11

    00:29:12 the gulf

    between the old and new worlds.

    00:29:15

    00:29:19 The undisputed stars

    of the dinosaur era

    00:29:21

    00:29:21 are animals like Triceratops

    and T-Rex.

    00:29:25

    00:29:25 But there are some important creatures

    scurrying around their feet.

    00:29:29

    00:29:30 lf we were to trace our lineage back

    far enough,

    00:29:33

    00:29:33 we would come to really small

    shrew-like mammals

    00:29:37

    00:29:37 surrounded by

    these titans of reptile life.

    00:29:40

    00:29:41 During that time, mammals,

    we were living on the fringes.

    00:29:44

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    00:29:44 We were maybe stealing dinosaur eggs,

    maybe just eking out an existence.

    00:29:49

    00:29:49 So the dinosaurs kind of held us back.

    00:29:52

    00:29:53 The biggest headline of the history

    of dinosaurs,

    00:29:56

    00:29:56 which is 1 60 million years,

    is that we lost!

    00:29:59

    00:30:00 Mammals lost.

    00:30:01

    00:30:02 We couldn't get much bigger

    than a small cat.

    00:30:05

    00:30:05 For 1 60 million years,

    all the medium-size, medium-big,

    00:30:09

    00:30:09 big, gigantic and stupendous animals

    were dinosaurs, for that whole time!

    00:30:14

    00:30:15 They beat us fair and square.

    00:30:18

    00:30:20 But the deck

    is about to be reshuffled.

    00:30:23

    00:30:32 Sixty-five million years ago,

    00:30:34

    00:30:34 a six-mile wide object,

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    likely an asteroid,

    00:30:38

    00:30:38 slams into the Earth.

    00:30:40

    00:30:48 A dust cloud blocks out the sun.

    00:30:51

    00:30:51 Temperatures plummet.

    00:30:53

    00:30:54 Every creature on land

    weighing over 50 pounds goes extinct.

    00:30:58

    00:31:00 The reign of the dinosaurs is over.

    00:31:03

    00:31:05 The greatest gift that the dinosaurs

    ever gave us was dying.

    00:31:09

    00:31:10 When they went extinct,

    it gave the mammals time to rise.

    00:31:14

    00:31:16 lt doesn't take long after

    the disappearance of the dinosaurs

    00:31:19

    00:31:19 for the first true primates to appear.

    00:31:22

    00:31:23 Like their later versions,

    including us,

    00:31:26

    00:31:26 these mammals have evolved

    forward-facing eyes

    00:31:29

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    00:31:29 allowing for accurate depth perception

    and flexible hands with five digits.

    00:31:35

    00:31:35 They have five fingers, just like us,

    which means we can grasp things.

    00:31:40

    00:31:40 lf you think about other animals

    that don't have digits

    00:31:42

    00:31:44 organized the way ours are,

    their ability to hold things,

    00:31:46

    00:31:46 to manipulate objects,

    is much more limited.

    00:31:49

    00:31:52 Fifty million years ago,

    00:31:54

    00:31:54 our primate ancestors are evolving

    on a planet that is warming.

    00:31:58

    00:31:59 lt's so hot,

    there are jungles at the poles.

    00:32:02

    00:32:05 As the continents drift,

    00:32:07

    00:32:07 the Americas and Africa

    have almost fully taken shape.

    00:32:10

    00:32:12 But in northern Africa,

    00:32:13

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    00:32:14 modern-day Egypt

    is submerged beneath an ancient sea.

    00:32:17

    00:32:19 On the floor of that sea live small,

    shelled creatures called nummulites.

    00:32:24

    00:32:24 Their shells,

    made of calcium and carbon,

    00:32:26

    00:32:26 pile up on the sea bottom

    over millions of years,

    00:32:29

    00:32:29 where they form into limestone.

    00:32:32

    00:32:33 Limestone that will be used

    to build the Great Pyramids.

    00:32:36

    00:32:37 lf you look closely

    at the pyramids today,

    00:32:39

    00:32:40 you can still see evidence that

    these 4,000-year-old monuments

    00:32:43

    00:32:43 are in fact made of

    50-million-year-old seashells.

    00:32:48

    00:32:56 By 1 0 million years ago,

    00:32:58

    00:32:58 Earth is morphing into a world

    most of us would recognize.

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    00:33:02

    00:33:02 The Colorado River

    is carving out the Grand Canyon.

    00:33:05

    00:33:06 Mountain ranges

    like the Himalayas have arisen.

    00:33:09

    00:33:09 They're so tall,

    they disrupt weather patterns

    00:33:12

    00:33:13 setting the stage for a colder planet.

    00:33:16

    00:33:20 The lsthmus of Panama emerges

    to connect North and South America,

    00:33:25

    00:33:25 cleaving the connection between

    the Atlantic and the Pacific,

    00:33:29

    00:33:29 disrupting ocean currents

    00:33:30

    00:33:30 and tipping the world

    even more towards an ice age.

    00:33:34

    00:33:37 With the planet getting colder,

    00:33:39

    00:33:39 our primate ancestors

    hang on in the tropics,

    00:33:42

    00:33:42 but a new creature is coming in

    that threatens to destroy them.

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    00:33:47

    00:33:56 Seven million years ago,

    00:33:58

    00:34:00 our primate ancestors

    live safely in the trees.

    00:34:03

    00:34:04 But their neighborhood

    is about to be invaded.

    00:34:07

    00:34:08 This newcomer will have

    as profound an effect on human history

    00:34:11

    00:34:11 as any other living thing on Earth.

    00:34:14

    00:34:16 lt seems almost impossible to believe,

    00:34:19

    00:34:19 but one of the most important things

    that will lead to the emergence of us,

    00:34:23

    00:34:24 is the emergence of grass.

    00:34:27

    00:34:29 The grasslands appear almost

    simultaneously around the world.

    00:34:33

    00:34:35 We get the African savannas,

    00:34:37

    00:34:39 we get the Eurasian steppe lands,

    00:34:41

    00:34:42 we get the North American prairies,

    00:34:45

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    00:34:46 we get the great grasslands

    ofArgentina,

    00:34:49

    00:34:50 appearing simultaneously

    around the world.

    00:34:53

    00:34:56 ln Eastern Africa, grasslands invade

    the traditional woodland habitat

    00:35:00

    00:35:01 of our ape ancestors.

    00:35:02

    00:35:03 With fewer trees

    and greater gaps between them,

    00:35:06

    00:35:06 our ancestors have to adapt.

    00:35:09

    00:35:09 Apes would notice that there's more

    and more apes in the same tree

    00:35:12

    00:35:12 and less and less food,

    00:35:14

    00:35:15 increasing incentives for apes

    00:35:16

    00:35:16 to go from one patch of food

    to a different one,

    00:35:18

    00:35:18 separated by grasslands.

    00:35:19

    00:35:20 Now, one way to do it

    is to run like hell, you know.

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    00:35:23

    00:35:23 The other way to do it is to extend

    one's food sources into the grasslands

    00:35:27

    00:35:27 to seek out the foods

    that are available there.

    00:35:30

    00:35:32 And so, some apes make the move down

    into this stark, new habitat.

    00:35:37

    00:35:40 lt's a landscape better suited

    to primates that can walk on two legs.

    00:35:45

    00:35:46 Keeping their heads up above the tall

    grasses to watch for predators.

    00:35:51

    00:35:54 Standing on two feet

    is a revolutionary advance.

    00:35:57

    00:35:59 Because it frees up our hands.

    00:36:01

    00:36:03 Hands we will need

    to shape human history.

    00:36:06

    00:36:16 2.6 million years ago,

    00:36:18

    00:36:21 early proto-humans or hominids

    00:36:24

    00:36:24 walk an Earth whose rocks are

    loaded with the element silicon.

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    00:36:28

    00:36:31 Created in the cores of stars

    billions of years before,

    00:36:36

    00:36:36 silicon is the second-most

    abundant element in Earth's crust.

    00:36:40

    00:36:40 One of its chemical quirks

    is the ability to bond with oxygen

    00:36:44

    00:36:44 to form crystals

    that combine into solid rocks,

    00:36:48

    00:36:49 rocks that can be chipped

    and shaped without shattering.

    00:36:52

    00:36:54 Hominids started doing this

    2.6 million years ago,

    00:36:57

    00:36:58 breaking cryptocrystalline silicates

    to make sharp edges,

    00:37:01

    00:37:01 and people use them for millions,

    literally 2.6 million years.

    00:37:05

    00:37:10 Simply having a modified stone

    with a sharp edge on it,

    00:37:13

    00:37:13 now suddenly you have a hammer.

    00:37:15

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    00:37:15 You have a crude cutting edge.

    00:37:18

    00:37:18 A simple modified stone means

    a human can suddenly do

    00:37:22

    00:37:22 a thousand more things

    than we could do previously.

    00:37:26

    00:37:31 That little extra bit of technology

    00:37:34

    00:37:34 enabled our ancestors to persist

    and eventually turn into us.

    00:37:40

    00:37:43 Silicon launches the first

    technological revolution,

    00:37:46

    00:37:47 the Stone Age.

    00:37:49

    00:37:51 Millions of years after it powers

    our first handheld devices,

    00:37:56

    00:37:56 another chemical quirk

    of silicon will make it

    00:37:59

    00:37:59 the height of technology once again.

    00:38:01

    00:38:04 The next leap towards

    becoming truly human

    00:38:07

    00:38:07 relies on a little-known secret

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    of our home planet.

    00:38:10

    00:38:10 ln the known universe,

    00:38:12

    00:38:12 it turns out Earth

    may have a rare and special power.

    00:38:15

    00:38:21 Of all the planets and moons

    in the solar system,

    00:38:24

    00:38:24 we think that Earth is unique

    in the ability to sustain fire.

    00:38:29

    00:38:32 Other planets and moons

    have lightning and lava.

    00:38:35

    00:38:38 But only on Earth do we have

    the two critical things

    00:38:40

    00:38:41 we need for fire to burn,

    00:38:43

    00:38:45 a vast fuel supply

    in the form of plants and trees,

    00:38:48

    00:38:49 and an atmosphere full of oxygen

    to fan the flames.

    00:38:52

    00:38:53 lf fire wasn't a possibility, you'd

    have nothing like us running around.

    00:38:57

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    00:39:01 Homo sapiens,

    they made a world with fire.

    00:39:04

    00:39:10 Our ancestors have fire firmly

    under control by 800,000 years ago.

    00:39:15

    00:39:19 lt's a skill that connects us

    back to the very beginning.

    00:39:22

    00:39:24 Remember that all energy

    was created in the Big Bang

    00:39:27

    00:39:27 and all life is in a competition

    for our share of this energy.

    00:39:31

    00:39:33 Using fire to cook is like having

    00:39:35

    00:39:35 an external stomach

    to break down foods,

    00:39:38

    00:39:38 releasing more calories,

    giving us more energy,

    00:39:42

    00:39:42 which in turn allows us

    to support bigger brains.

    00:39:45

    00:39:48 Fire is also the ultimate

    gateway technology.

    00:39:51

    00:39:52 We will soon use it

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    to turn clay into pottery,

    00:39:55

    00:39:56 metal into weapons,

    00:39:58

    00:39:59 water into steam power.

    00:40:01

    00:40:03 lf you don't have fire, you can't have

    the internal combustion engine.

    00:40:06

    00:40:06 No fire, no metal.

    00:40:08

    00:40:08 No fire, no rubber.

    00:40:09

    00:40:11 lt's a technology that opens a world

    of possibilities

    00:40:14

    00:40:14 for creatures that know how to use it.

    00:40:16

    00:40:22 200,000 years ago,

    00:40:24

    00:40:27 the modern human

    has fully taken shape.

    00:40:29

    00:40:31 The larynx or voice box

    00:40:33

    00:40:33 which is high up in the throat

    in our ancestors, descends.

    00:40:37

    00:40:38 More complex sounds are now possible.

    00:40:41

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    00:40:44 We begin to speak.

    00:40:47

    00:40:49 For the first time,

    information can be shared

    00:40:52

    00:40:52 between individuals

    and across generations.

    00:40:56

    00:40:57 Humans have gained

    a critical advantage

    00:40:59

    00:40:59 over every other creature on Earth.

    00:41:01

    00:41:02 You can tell, "My grandfather said

    that when the elephants didn't show up

    00:41:05

    00:41:05 "we go off and hunted zebras."

    00:41:06

    00:41:07 You know, "My aunt told me that her

    cousin found this water hole

    00:41:10

    00:41:10 "on the other side of that river."

    00:41:11

    00:41:13 And we can all benefit

    00:41:14

    00:41:14 and we can all understand what they

    mean when they were describing

    00:41:17

    00:41:17 what they found out on that landscape.

    00:41:19

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    00:41:20 Language changes humans

    from being like stand-alone computers

    00:41:24

    00:41:24 to being networked computers

    where you can share information.

    00:41:27

    00:41:30 Now, one doesn't need to depend

    on one's own personal experience.

    00:41:32

    00:41:33 One can borrow the personal experience

    of anyone

    00:41:36

    00:41:36 with whom one can communicate.

    00:41:37

    00:41:38 That's a powerful advantage.

    00:41:39

    00:41:39 No other creature has that.

    00:41:41

    00:41:42 As a species,

    humans become exponentially smarter.

    00:41:46

    00:41:47 The global game board has been set,

    and we are now ready to play.

    00:41:51

    00:41:54 1 00,000 years ago, man can move.

    00:41:58

    00:41:59 We have agile hands

    and primitive tools.

    00:42:02

    00:42:02 We can communicate and control fire.

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    00:42:05

    00:42:06 We are finally ready to expand

    out of our African home

    00:42:09

    00:42:11 on a path

    millions of years in the making.

    00:42:14

    00:42:19 Shifting continents have linked Africa

    and Eurasia

    00:42:22

    00:42:22 into the largest contiguous landmass

    on Earth, Afro-Eurasia.

    00:42:27

    00:42:29 33 million square miles,

    00:42:31

    00:42:31 more than twice the surface area

    of our entire moon.

    00:42:34

    00:42:36 For early humans,

    00:42:37

    00:42:37 this means more than half the land

    on Earth can be reached on foot.

    00:42:42

    00:42:47 Human dispersal

    was a crucial game changer.

    00:42:50

    00:42:51 We are one of the few primates

    00:42:53

    00:42:53 that live on more than

    one continent simultaneously.

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    00:42:56

    00:42:57 So what that means is that

    we're better insulated

    00:43:00

    00:43:00 from the kinds of things that caused

    big mammals to become extinct

    00:43:02

    00:43:03 than other primates are.

    00:43:04

    00:43:05 lt's extinction insurance.

    Dispersal is extinction insurance.

    00:43:08

    00:43:12 But just as the world

    begins to open itself up to man,

    00:43:16

    00:43:16 the planet turns on us.

    00:43:18

    00:43:20 An ice age begins.

    00:43:22

    00:43:24 Now the planet will test us

    like never before.

    00:43:27

    00:43:29 By 50,000 years ago, glaciers begin

    to advance down from the North Pole.

    00:43:34

    00:43:34 At the same time, humans continue

    their conquest of the globe,

    00:43:38

    00:43:38 arriving in China and Australia.

    00:43:40

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    00:43:41 By 30,000 years ago, Homo sapiens

    reach Europe for the first time.

    00:43:45

    00:43:46 By 20,000 years ago, with the ice

    nearing its most extreme,

    00:43:50

    00:43:51 the march of man reaches the frigid

    tundra of Northeast Siberia.

    00:43:55

    00:43:57 Despite the trials of the lce Age,

    00:43:59

    00:44:00 man endures and develops the last

    skills we will need to be truly human.

    00:44:07

    00:44:12 The clues lie in these symbols.

    00:44:14

    00:44:16 We have taken an intellectual leap,

    00:44:18

    00:44:18 to think beyond the here and now,

    00:44:21

    00:44:21 beyond what is simply

    needed to survive.

    00:44:24

    00:44:25 We can only start saying we have

    an organism that is human,

    00:44:28

    00:44:28 that is the same as us,

    00:44:29

    00:44:29 when we start seeing evidence

    of symbolic thought.

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    00:44:31

    00:44:33 lt's when we start seeing

    a picture of a cow

    00:44:37

    00:44:38 that everybody will recognize

    as the picture of a cow.

    00:44:41

    00:44:41 Because only when we start seeing

    all of those things

    00:44:44

    00:44:44 can we say that is a human.

    00:44:46

    00:44:47 People or creatures

    that think like us,

    00:44:50

    00:44:51 that see the world

    in the same way as us.

    00:44:53

    00:44:54 And from that moment on,

    00:44:55

    00:44:55 human history was marked to be

    radically different

    00:44:56

    00:44:58 to any other species on this planet.

    00:45:00

    00:45:01 Now, with huge amounts of the planet's

    water locked up in ice,

    00:45:05

    00:45:05 sea levels plummet by 300 to 400 feet.

    00:45:09

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    00:45:10 The last great barrier

    to the spread of man is erased.

    00:45:14

    00:45:14 We come across the Bering Land Bridge

    from Siberia to North America.

    00:45:19

    00:45:23 We are telling the history

    of the world in two hours,

    00:45:26

    00:45:26 and in just one hour, more than

    1 3 billion years have already passed.

    00:45:31

    00:45:31 These years of preparation

    have allowed man

    00:45:34

    00:45:34 to finally emerge

    and spread out across the planet.

    00:45:37

    00:45:38 And human history as we know it

    can truly begin.

    00:45:41

    00:45:48 Our history of the world began with

    the beginning of time, the Big Bang.

    00:45:53

    00:45:54 lt has taken us on a journey

    of nearly 14 billion years.

    00:45:58

    00:46:01 Now, as humans take center stage,

    00:46:04

    00:46:04 it's important to remember

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    00:46:06

    00:46:07 just how small a slice of history

    we actually occupy.

    00:46:11

    00:46:12 To make things simple,

    00:46:13

    00:46:13 imagine compressing 14 billion years

    of history

    00:46:17

    00:46:18 down to just 14 years.

    00:46:20

    00:46:22 On this scale, the Earth would have

    existed only for the past five years.

    00:46:28

    00:46:29 So that's about a third

    of the history of the universe.

    00:46:31

    00:46:32 Large complex creatures

    would have developed seven months ago.

    00:46:36

    00:46:37 On this scale, dinosaurs went extinct

    only about three weeks ago.

    00:46:42

    00:46:43 The entire recorded history of humans

    00:46:45

    00:46:46 would span

    only the last three minutes.

    00:46:49

    00:46:50 Modern industrial societies,

    00:46:51

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    00:46:52 the lndustrial Revolution,

    effectively, six seconds ago.

    00:46:55

    00:46:57 What this shows me is that we humans

    have been around

    00:47:00

    00:47:00 for only a very brief instant in

    the recorded history of the universe.

    00:47:05

    00:47:06 Mankind has waited billions of years

    for our brief instant to shine,

    00:47:11

    00:47:12 as the stars and our evolving planet

    00:47:14

    00:47:14 carried out the slow work

    of organizing the elements

    00:47:17

    00:47:18 in a way that would

    make human history possible.

    00:47:20

    00:47:27 lt's 1 0,000 B.C.,

    00:47:29

    00:47:29 less than 1 00,000 years

    after expanding out ofAfrica,

    00:47:34

    00:47:34 man has reached South America.

    00:47:36

    00:47:37 Humans have met the adversity

    of the ice age head on,

    00:47:40

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    00:47:41 and rather than die off,

    00:47:42

    00:47:43 we have adapted,

    become even more intelligent.

    00:47:46

    00:47:47 And now

    we have colonized the entire globe.

    00:47:50

    00:47:52 From coast to mountaintop,

    00:47:55

    00:47:58 from tundra to desert,

    00:48:03

    00:48:04 humans are there.

    00:48:06

    00:48:07 Our closest living ancestors,

    the chimpanzees, live in the tropics.

    00:48:11

    00:48:11 They only live in the tropics.

    00:48:13

    00:48:13 Humans have managed to colonize

    the entire globe.

    00:48:16

    00:48:18 lce age land bridges allowed man

    to spread around the world,

    00:48:22

    00:48:22 but now the ice begins to melt

    and sea levels rise again.

    00:48:28

    00:48:28 Humans are trapped and separated in

    two vast and unconnected hemispheres.

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    00:48:33

    00:48:33 Each pocket of humanity left to make

    the best of what it has been given.

    00:48:38

    00:48:39 As the glaciers recede,

    00:48:41

    00:48:41 they carve out lakes,

    rivers, and bays.

    00:48:45

    00:48:46 The map as we know it emerges.

    00:48:48

    00:48:51 ln Africa,

    00:48:52

    00:48:52 increased rainfall causes Lake

    Victoria and Lake Albert to overflow

    00:48:56

    00:48:58 and form Egypt's Nile River.

    00:49:00

    00:49:02 ln Eurasia, other rivers emerge,

    00:49:04

    00:49:05 the Tigris and Euphrates

    in Mesopotamia, modern-day lraq.

    00:49:09

    00:49:11 The lndus in modern-day Pakistan

    and China's Yellow and Yangtze.

    00:49:16

    00:49:18 These river valleys

    become critically important

    00:49:20

    00:49:20 for how human history will now be

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    played out

    00:49:23

    00:49:23 following the retreat

    of these ice sheets.

    00:49:25

    00:49:27 These are the river valleys

    whose waters and fertile soils

    00:49:31

    00:49:31 will allow the first seeds

    of civilization to be planted.

    00:49:35

    00:49:38 With temperatures warming

    after the ice age,

    00:49:41

    00:49:41 plants and animals are more plentiful,

    00:49:44

    00:49:45 and man can finally

    choose to stop moving.

    00:49:48

    00:49:50 Permanent settlements begin.

    00:49:52

    00:49:54 Populations grow.

    00:49:55

    00:50:00 With more mouths to feed,

    our ancestors have to get clever.

    00:50:04

    00:50:06 They had to find a way

    to increase the amount of food

    00:50:08

    00:50:08 they could get from the surroundings.

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    00:50:10

    00:50:11 Now, one discovery forever changes

    the planet and the path of mankind.

    00:50:17

    00:50:20 We learn to plant seeds.

    00:50:22

    00:50:25 And the seeds we sow

    come from the same plants

    00:50:28

    00:50:28 that millions of years earlier

    spurred our evolution from ape to man,

    00:50:33

    00:50:33 the unheralded hero

    of human history, grass.

    00:50:38

    00:50:40 A grass seed is tiny, right?

    lt's no food.

    00:50:42

    00:50:42 l can hunt a bison

    or l can take grass.

    00:50:44

    00:50:45 You hunt a bison, right?

    00:50:47

    00:50:47 lronically, grass seeds

    become the most important food crops

    00:50:50

    00:50:50 in the world, but they're the things

    that are ignored by hunter-gatherers

    00:50:53

    00:50:53 for thousands and thousands of years.

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    00:50:55

    00:50:55 People don't start using them until

    they absolutely have to use them.

    00:50:58

    00:51:00 Some of the species of grass

    that we are most familiar with

    00:51:03

    00:51:03 includes sugarcane.

    00:51:05

    00:51:05 lt includes wheat and rye and barley,

    00:51:09

    00:51:09 all of the cereal crops

    are types of grass.

    00:51:12

    00:51:13 So it's not just

    that beautiful green lawn

    00:51:16

    00:51:16 that we measure

    our middle class success from.

    00:51:18

    00:51:19 lt's also the staple crop

    upon which civilization depends.

    00:51:24

    00:51:24 lt is the majority

    of our calorie intake.

    00:51:27

    00:51:29 Once again,

    it all goes back to the Big Bang.

    00:51:32

    00:51:34 Central to the story of all life

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    is our competition for that energy

    00:51:37

    00:51:37 created at the beginning of time.

    00:51:39

    00:51:40 Just as oxygen gave us an edge,

    00:51:43

    00:51:43 just as fire allowed us

    to consume more calories,

    00:51:47

    00:51:47 switching to farming

    is an energy revolution.

    00:51:50

    00:51:51 A hunter-gatherer

    needs 1 0 square miles of territory

    00:51:54

    00:51:54 to provide himself

    with enough sustenance,

    00:51:57

    00:51:57 enough energy in the form of

    plants and meat to survive.

    00:52:01

    00:52:02 A farmer can harvest the sun's energy

    so efficiently,

    00:52:06

    00:52:06 he can fulfill his needs using

    only a tenth of a square mile of land.

    00:52:11

    00:52:14 ln the warming after the last ice age,

    farming begins to take hold

    00:52:18

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    of the world.

    00:52:55

    00:52:56 Unlike the Fertile Crescent

    and the rest ofAfro-Eurasia,

    00:53:00

    00:53:00 places like sub-Saharan Africa

    and the Americas

    00:53:03

    00:53:03 have very few wild species

    that can be easily domesticated.

    00:53:08

    00:53:10 lt's a critical difference.

    00:53:13

    00:53:13 People blessed with the right mix

    of plants and animals

    00:53:16

    00:53:16 will become more powerful

    00:53:18

    00:53:18 and get a massive head start

    on the road to the modern world.

    00:53:22

    00:53:30 One animal that gives any human

    who can tame it

    00:53:33

    00:53:33 an almost unbeatable edge

    is the horse.

    00:53:37

    00:53:39 lt's a little-known fact that although

    horses first evolved in the Americas,

    00:53:43

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    00:53:43 they died out there

    along with many other large mammals

    00:53:47

    00:53:47 around 1 0,000 B.C.

    00:53:49

    00:53:49 There were at least three species

    of ice age horses in North America,

    00:53:52

    00:53:52 maybe more, some as small as ponies,

    some as big as Clydesdales.

    00:53:56

    00:53:56 And they had evolved in North America

    for 40 million years.

    00:53:59

    00:53:59 They're part of the whole history, and

    then... They're gone. They're gone.

    00:54:03

    00:54:04 These powerful potential allies

    00:54:06

    00:54:06 disappear before they can be used

    by the first North Americans.

    00:54:10

    00:54:10 Fortunately before that happened,

    00:54:12

    00:54:12 large numbers of horses escaped back

    across the Bering Strait land bridge

    00:54:16

    00:54:16 and spread out

    across the great grasslands

    00:54:18

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    00:54:18 and steppe lands of Central Eurasia.

    00:54:20

    00:54:22 A narrow escape that had

    a profound effect on human history.

    00:54:26

    00:54:27 Around 4,000 B.C.,

    00:54:29

    00:54:29 nomadic people in Central Asia

    learn to tame them for the first time.

    00:54:34

    00:54:36 Domesticated horses will be harnessed

    across Eurasia,

    00:54:40

    00:54:40 advancing everything

    from work to warfare.

    00:54:43

    00:54:47 Perhaps no other animal

    has had a bigger influence

    00:54:50

    00:54:50 on the course of human history.

    00:54:52

    00:54:54 And the circle wouldn't be complete

    for another 5,000 years

    00:54:58

    00:54:58 when Christopher Columbus

    would bring horses with him

    00:55:01

    00:55:01 on his second voyage to the Americas.

    00:55:04

    00:55:05 His horses would be the first

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    to set hooves in the Americas

    00:55:09

    00:55:09 since the great die-off

    over 1 0,000 years earlier.

    00:55:13

    00:55:21 6,000 years ago,

    domestication of animals and plants

    00:55:25

    00:55:25 sets the stage for the next phase

    of human history.

    00:55:29

    00:55:30 Like clouds of interstellar dust

    gathering in material to form stars,

    00:55:35

    00:55:35 a type of gravity is at work

    as places like Sumeria,

    00:55:39

    00:55:39 located in part of the

    Fertile Crescent known as Mesopotamia,

    00:55:43

    00:55:43 draw in people,

    support large populations,

    00:55:46

    00:55:46 and spin up into centers of power

    and innovation.

    00:55:50

    00:55:52 By 3,000 B.C.,

    00:55:54

    00:55:54 some of these Sumerian settlements

    can truly be called our first cities.

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    00:56:46 ln the case of the Middle East,

    wheat and barley.

    00:56:48

    00:56:49 ln the case of wheat and barley,

    00:56:50

    00:56:50 they both ripen

    at about the same time.

    00:56:53

    00:56:53 Humans have to gather the seeds

    at the same time.

    00:56:56

    00:56:56 So now we have our food for the year

    that has arrived in one hit.

    00:57:00

    00:57:01 lt's like getting your salary

    paid once a year.

    00:57:04

    00:57:04 You need to record it.

    You need to plan,

    00:57:06

    00:57:06 because if inevitably your crop fails,

    you have famine.

    00:57:10

    00:57:11 And you're not gonna have another go

    for another 1 2 months.

    00:57:14

    00:57:19 ln these first cities, crops are king.

    00:57:23

    00:57:25 To keep track of them,

    00:57:27

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    00:57:27 our ancestors

    develop the first writing.

    00:57:30

    00:57:30 To protect them, the first armies.

    00:57:33

    00:57:34 And to administer them,

    the beginnings of politics.

    00:57:37

    00:57:38 When you have hundreds or thousands

    of people who are living together,

    00:57:42

    00:57:42 there's simply too many people

    00:57:43

    00:57:43 to sort of run around

    and create a census.

    00:57:45

    00:57:45 lt creates a need for government.

    00:57:48

    00:57:49 lt creates a need for some form of

    social and political hierarchy.

    00:57:53

    00:57:55 Planting seeds has set man

    on a new path.

    00:57:57

    00:57:59 Settlements have grown into cities.

    00:58:01

    00:58:02 But to take the next epic step

    from city to civilization,

    00:58:07

    00:58:07 we'll need the help

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    of a very surprising creature.

    00:58:11

    00:58:22 5,000 years ago,

    00:58:25

    00:58:25 after wandering the Earth

    for more than 1 00,000 years,

    00:58:29

    00:58:30 mankind has begun to settle down.

    00:58:32

    00:58:35 We cluster near rivers,

    along the Tigris and Euphrates,

    00:58:39

    00:58:41 the Nile, the lndus,

    00:58:45

    00:58:47 the Yellow and Yangtze.

    00:58:49

    00:58:49 Civilizations are about to take off.

    00:58:51

    00:58:54 But first,

    they must all master one thing, trade.

    00:58:58

    00:58:59 The more they exchange goods

    and learn from other lands,

    00:59:02

    00:59:02 the faster they grow.

    00:59:04

    00:59:05 lt seems that long-distance trade

    and communication

    00:59:08

    00:59:08

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    00:59:10