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(STEVE LEONARD) Imagine the freedom,
the buzz, the excitement of taking to the skies,
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If only I could,
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Being able to fly is something
that humans have always dreamed of,
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but for two-thirds of the animals
alive today, it's a reality.
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Flight is one of the greatest breakthroughs
in the whole story of evolution.
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I'm going to find out how life
achieved the miracle of flight,
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Over millions of years,
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a string of evolutionary accidents
created wings not once but several times,
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and in very different ways,
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Oh, yes! Look at you.
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Flight is a unique weapon,
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Mastering the skies
leaves earthbound creatures at your mercy,
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Where there's a black eagle on the wing,
rock hyrax need to be alert to aerial attack,
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But wings aren't just about extra strike power,
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Flying is the fastest,
most efficient way to travel,
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It allows you to find food,
explore new territory, or escape from danger,
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So there were lots of good reasons for life
to get into the air - the trick was how to do it,
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There's one big problem facing any animal
that wants to fly.
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Gravity.
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And to fly, you’ve got to find a way to defy it.
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So, in the journey of life, who was
the first to conquer gravity and get airborne?
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500 million years ago, animals
took their first steps onto land,
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The pioneers included millipedes,
scorpions and spiders,
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But while these creatures crawled
over the earth, the skies remained empty,
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Life stayed grounded
for at least another 100 million years..,
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..until one group of animals
finally made the breakthrough,
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The insects.
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The first animals ever to fly.
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But how did they sprout wings?
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One idea is that it's all because
insects love to sunbathe.
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Insects are cold-blooded,
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They need heat from the outside
to warm themselves up and move around,
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They often bask in the sun,
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and maybe in the past, one bug developed
small flaps on its back to help soak up the rays,
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like mini solar panels,
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Purely by chance, these panels may also have
helped the insect to be carried by the wind,
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Perhaps the panels then evolved into a more
aerodynamic shape, eventually becoming wings,
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But there's a flaw in this theory,
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Insect wings have complex hinged joints,
worked by muscles and tendons,
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Could they really have evolved
from those simple fixed panels?
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There is another explanation
as to how flight began,
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It all started not in the air but in the water.
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Many insects spend the first part
of their lives submerged,
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They breathe through gills, pumping
them up and down to take in oxygen,
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It's thought it was gills like these
that gradually turned into wings,
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But how could such a dramatic change
take place?
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One insect living in the rivers
of North America holds a clue,
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Stonefly larvae spend almost a year underwater,
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then emerge in late winter
to start their adult lives,
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The adults live just a few days,
and their sole purpose is to breed,
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But to find a mate, they have to make
a death-defying crossing to the shore,
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Their wings are far too weak to fly..,
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..but they do make good sails,
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Perhaps this is how flight began,
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An ancient insect waved its gills
to catch the breeze and set sail,
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just like stoneflies do today,
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Gills already had the joints and muscles
to flap up and down,
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and could then have evolved from sails to wings,
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And then, insects really took off,
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Whatever that first flying insect was, it won
the biggest evolutionary jackpot of all time,
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Its genes were now unstoppable,
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and today its legacy is around
10 million flying insect species -
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the most successful type of animal on Earth,
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Ancient fossils have shed light
on some of the oldest aerial pioneers,
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Among them is one design
that's really stood the test of time,
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Dragonflies have been around
for more than 300 million years,
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They were already on the wing
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when our four-legged ancestors
were still crawling around in swamps,
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Dragonflies are the Red Barons
of the insect world - fast, agile aerial aces.
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These are male emperor dragonflies,
and they're fiercely territorial,
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When rivals meet, they test
each other's flying skills to the limit,
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These dogfights can be vicious, even deadly,
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Dragonflies are among the largest,
fastest insects on the planet,
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but compared to some,
these modern ones are midgets,
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Go back 300 million years..,
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..and things were very, very different.
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Then there were giants,
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Dragonflies with two-foot wingspans -
the size of a hawk,
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How did such mega-bugs stay in the air?
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Well, there was one big difference back then,
one that could turn me into a super-athlete,
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The atmosphere was supercharged with oxygen,
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There was almost twice the amount
there is today to power those monster wings,
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Dragonflies are still dazzling fliers,
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but the best stunt pilot of them all
is smaller and much less glamorous,
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(BUZZING)
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Ever tried to swat a fly?
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Tricky, isn't it?
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They really are the most amazing
of all flying animals.
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And one of the most annoying.
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Their manoeuvrability is unrivalled.
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And their reactions are 12 times faster
than or own.
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So what's their secret?
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Well, bizarrely, it's because their ancestors
gave up a pair of wings.
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(BUZZING)
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Like dragonflies, all early insects
had two pairs of wings,
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In one type, the hind wings shrank, evolving
into tiny rod and ball structures called halteres,
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They have become precision instruments,
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They work a bit like gyroscopic stabilisers
on a modern helicopter or plane,
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Flies come in a great variety
of shapes and sizes,
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They include the hoverfly, crane fly, mosquito,
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and our friendly housefly,
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and they all have halteres,
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Halteres give the fly precise feedback
on its position,
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helping it make split-second adjustments
without losing control,
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So it can dodge a swipe
and instantly regain perfect poise,
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Love 'em or hate 'em,
you’ve got to admire 'em.
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There are now more than 100,000 kinds of fly,
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Their duck and dive design
has let them take over the world,
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and though they're small, they have
a massive impact on other life, including us,
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In fact, flies are the most
dangerous animals on Earth,
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responsible for more human deaths
than any other creature,
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They carry and spread disease,
and because they're so small and manoeuvrable,
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it's impossible to escape from them,
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Having the top technology for flight isn't the
only thing that's made insects such a success,
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It's also about when to fly.
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It's hard to believe that this
and this are the same animal.
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(MUSIC)
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Why does such a gorgeous creature
have such weird and wingless offspring?
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It's because its life is split in two -
one part for eating and one for breeding,
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Caterpillars are munching machines,
Their only purpose is to eat and grow,
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At this stage, having wings
would just get in the way,
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A caterpillar can balloon to an incredible
2,000 times its starting weight,
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That's like a human baby gaining eight tons
in a month and becoming the size of a bus,
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Once it's finished gorging,
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the caterpillar uses all those calories
to make a stunning transformation,
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From ugly bug..,
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..to winged beauty,
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The adult has a very different mission -
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to attract a mate and lay its eggs far and wide,
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Wings make this job much easier,
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and one species of butterfly
has taken air travel to extremes,
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This is the monarch, long haul operator
of the insect world,
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It's late summer in Canada,
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and these are great-great-grandchildren
of monarchs that flew north in spring,
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Now they're ready to embark
on one of nature's most miraculous journeys,
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Triggered by shorter, cooler nights,
they head south,
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flying the entire length
of North America and beyond,
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(MUSIC)
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Finally, having flown 3,000 miles,
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the monarchs reach their winter destination
in the mountains of central Mexico,
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Somehow, they find their way back
to the same trees used by previous generations,
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Millions clustered together
for safety and warmth,
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Insects flew unchallenged
for about 100 million years..,
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..but another twist of evolution
would bring about a second wave of flight,
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Skulking in the undergrowth was the ancestor
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of some of the most successful fliers ever that
would dominate the skies for 150 million years.
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The smallest would be
little bigger than a sparrow,
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and the largest, the size of a light aircraft -
the biggest animal ever to fly.
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They were the pterosaurs,
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Sadly, there are none left
to help us piece together their story,
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but what we do know is that
they evolved from an ancient kind of reptile.
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But how did a for-legged reptile turn
into one of nature’s most magnificent fliers?
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Today, there's a tree-dwelling reptile
that offers a clue,
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For a green iguana cornered in the treetops,
there's just one way out -
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straight down!
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They generally hang out over water
for a safer landing,
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A simple free fall isn't very stylish,
but it is a start,
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If you can add some control to your descent,
then you're a step closer to taking flight,
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In the forests of south-east Asia
lives an animal that's done just that,
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This gecko has evolved
a kind of onboard parachute,
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Webbed toes and flaps of skin along its sides
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act like air brakes, giving it
some control over its speed,
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It can't travel far, but it's certainly
a leap in the right direction,
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But if you think the flying gecko is impressive,
wait till you see its neighbour,
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The draco looks like any other lizard -
until it jumps,
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This simple wing is actually skin membrane
stretched over its ribs,
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It lets this tiny lizard glide up to 100 metres,
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Strictly speaking, it's still not flying,
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but it saves an awful lot
of climbing up and down,
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One ancient reptile took gliding a stage further,
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Once its arms became wings,
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it could develop the power of true flight,
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(SCREECHES)
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And this second airborne breakthrough
spawned the pterosaurs,
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(MUSIC)
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From fossils, we know that there were
many different kinds of pterosaurs,
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One had a mouth with a built-in sieve
to filter out small creatures from the water -
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much like a modern flamingo does,
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Another had hooked teeth
good for snagging slippery prey,
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It used its beak to trap fish
just below the surface, like a skimmer does,
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00:25:05,087 --> 00:25:08,796
Another pterosaur
had an expandable throat pouch -
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a built-in fishing net,
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It was a kind of prehistoric pelican,
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But there's one thing about the pterosaurs
no bird can match - their size,
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Some got as big as this!
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But how did these giants
get off the ground and stay airborne?
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Well, John is going to show me how.
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OK, John.
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(JOHN) OK, let's run.
(STEVE) OK.
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Jumping off a cliff is a good start,
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Wow! That was pretty spectacular!
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00:26:05,127 --> 00:26:09,279
Well, pterosaurs might have been
slightly more graceful than that!
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The largest was Quetzalcoatlus,
and that got up to about 40 feet.
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00:26:18,927 --> 00:26:23,318
But how did the world's
biggest ever flying animal stay up?
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Pterosaurs were built very much like this -
very little body and all wing.
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00:26:33,327 --> 00:26:37,115
This hang glider's made
of hollow aluminium tubes,
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and the pterosaurs' bones
were also hollow to minimise weight.
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Once up in the air, they'd have soared away
and just used up draughts and thermals,
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very much like what we're doing.
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Whoa!
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This is beautiful.
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It is completely effortless -
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on my part anyway!
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This must be the closest thing
to just growing wings and flying.
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The one thing we don't really know
is how these large pterosaurs landed,
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00:27:55,487 --> 00:27:57,796
but I think I'm about to find out!
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00:27:57,967 --> 00:28:02,006
By landing into the wind,
we hope to avoid crash-landing,
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00:28:02,167 --> 00:28:04,203
There we go. OK.
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00:28:04,367 --> 00:28:07,245
Well, that's the theory!
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(STEVE LAUGHS) Excellent! That was great!
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Pterosaurs must have been a magnificent sight,
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00:28:27,607 --> 00:28:30,997
They ruled the skies for 150 million years,
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00:28:31,167 --> 00:28:35,080
but they mysteriously vanished
along with the dinosaurs,
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00:28:35,247 --> 00:28:38,956
By then, a third airborne animal had arrived,
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00:28:39,127 --> 00:28:42,085
Its success was down
to a brand-new structure -
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00:28:42,247 --> 00:28:49,164
one that would lead to the most beautiful flying
animals the world has ever known - the feather.
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(MUSIC)
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00:29:44,287 --> 00:29:49,202
The surprising thing about feathers
is that they didn't even evolve for flight.
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00:29:49,367 --> 00:29:54,043
Not only that, birds didn't even
invent the feather - they inherited it.
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(ROARS)
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00:30:03,287 --> 00:30:09,965
Birds are directly descended from a group
that includes the greatest predators of all time,
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00:30:15,407 --> 00:30:18,843
These fossils are of small meat-eating dinosaurs,
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00:30:19,007 --> 00:30:25,082
but look more closely and you'll notice
some mysterious impressions made by feathers,
224
00:30:35,287 --> 00:30:39,326
So what made these scaly hunters go fluffy?
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00:30:48,767 --> 00:30:51,679
Feathers are in fact modified scales,
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00:30:51,847 --> 00:30:56,398
Over countless generations,
some scales began to thin and fray,
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evolving into fluffy down,
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00:30:59,367 --> 00:31:03,042
but what did dinosaurs need these feathers for?
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00:31:04,567 --> 00:31:10,915
Today, fluffy feathers are still used by young
birds like albatross chicks to keep warm,
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00:31:14,047 --> 00:31:19,201
In the Antarctic, they must survive
sub-zero temperatures for months on end,
231
00:31:20,527 --> 00:31:24,759
Downy feathers might well have helped
insulate small dinosaurs,
232
00:31:24,927 --> 00:31:29,398
but what they weren't much good for
was making a wing,
233
00:31:30,447 --> 00:31:35,646
So how did fluffy feathers like these
turn into stiff ones like this used for flight?
234
00:31:35,807 --> 00:31:40,642
The latest theory is that evolution
hijacked the feather for a different job
235
00:31:40,807 --> 00:31:43,685
long before it was used for flight. Hello.
236
00:31:43,847 --> 00:31:50,241
It's now thought that feathers might have been
used for display, just like many birds do today.
237
00:32:00,367 --> 00:32:05,600
And stiff feathers make for far more
spectacular displays than fluffy down,
238
00:32:10,007 --> 00:32:13,363
Male birds flaunt themselves
to win over a female,
239
00:32:13,527 --> 00:32:16,200
and perhaps it was the same for dinosaurs,
240
00:32:16,367 --> 00:32:18,756
By choosing the most striking males,
241
00:32:18,927 --> 00:32:23,205
the females helped feathers evolve
in a completely different way,
242
00:32:25,127 --> 00:32:30,724
As soft feathers became longer and stronger,
they were more suitable for building wings
243
00:32:30,887 --> 00:32:33,117
as well as showing off,
244
00:32:35,927 --> 00:32:41,524
So feathered dinosaurs weren't just
the warmest, they were also the prettiest.
245
00:32:42,767 --> 00:32:45,839
And they were ready to take flight,
246
00:32:49,247 --> 00:32:53,684
But how did that first leap
into the skies actually happen?
247
00:32:57,887 --> 00:33:01,721
One theory is that feathered dinosaurs
lived on the ground
248
00:33:01,887 --> 00:33:05,880
and flapped their feathery arms
to help them jump for insects.
249
00:33:07,847 --> 00:33:09,599
But the most poplar theory,
250
00:33:09,767 --> 00:33:16,923
and certainly the one I find easiest to believe,
is that flight started up here, in the trees.
251
00:33:34,007 --> 00:33:39,001
A set of feathered arms would come in
very handy for a tree-dwelling dinosaur -
252
00:33:39,167 --> 00:33:43,718
they'd break a fall, and it's easy
to imagine with a few modifications,
253
00:33:43,887 --> 00:33:46,799
how they cold turn leaping into gliding.
254
00:33:48,287 --> 00:33:52,678
Then, as feathers and the muscles
moving them continued to develop,
255
00:33:52,847 --> 00:33:57,637
arms were reshaped into wings
strong enough to flap their way into the air,
256
00:33:57,807 --> 00:34:00,480
Gliding became true powered flight,
257
00:34:00,647 --> 00:34:03,286
Enter the birds,
258
00:34:20,807 --> 00:34:23,765
The evolution of birds
was a massive breakthrough.
259
00:34:23,927 --> 00:34:29,559
Their superb flying ability unlocked a way of life
that has proved very successful.
260
00:34:31,487 --> 00:34:34,923
The dinosaurs died out, yet birds survived,
261
00:34:35,087 --> 00:34:39,205
and more than that,
went on to dominate the skies,
262
00:34:39,407 --> 00:34:41,796
(MUSIC)
263
00:35:09,687 --> 00:35:13,202
All this thanks to the fabulous feather,
264
00:35:19,487 --> 00:35:23,765
The arrival of the birds marked a new era
in the history of life
265
00:35:23,927 --> 00:35:30,082
and the beginnings of an evolutionary battle
that would push flight to the extreme,
266
00:35:39,887 --> 00:35:44,881
Each spring, adult mayflies have just
a few short hours to get out of the water,
267
00:35:45,047 --> 00:35:47,515
find a mate, breed and lay eggs,
268
00:35:51,447 --> 00:35:54,166
But many never make it,
269
00:36:39,687 --> 00:36:42,599
The mayfly feast lasts just a few days,
270
00:36:42,767 --> 00:36:47,045
but there's lots more insect food
on offer if you can get to it,
271
00:36:56,367 --> 00:36:58,437
In an average summer month,
272
00:36:58,607 --> 00:37:04,159
it's estimated that around four billion insects
fly over each square mile of Britain,
273
00:37:05,567 --> 00:37:08,718
That's around one ton of insects.
274
00:37:13,607 --> 00:37:19,682
And I bet the people down there have no idea
what's floating around above their heads!
275
00:37:19,847 --> 00:37:23,283
We can't see them up here
because they're so small,
276
00:37:23,447 --> 00:37:28,919
but there are birds that can, that have evolved
to reach this banquet in the skies,
277
00:37:29,087 --> 00:37:32,523
And none are better at it than the swift.
278
00:37:33,647 --> 00:37:36,081
It's the ultimate high flier.
279
00:37:39,087 --> 00:37:43,956
Swifts spend most of their life on the wing
and all because of insects,
280
00:37:44,927 --> 00:37:49,239
They fly from South Africa each year
for our summer's insect feast,
281
00:37:49,407 --> 00:37:53,195
a return trip of around 14,000 miles,
282
00:37:55,807 --> 00:37:57,877
A long history of aerial pursuit
283
00:37:58,047 --> 00:38:03,724
has given swifts a streamlined body
with long narrow wings to slice through the sky,
284
00:38:10,287 --> 00:38:12,437
Only when filmed at normal speed
285
00:38:12,607 --> 00:38:16,520
can you really appreciate
how well they live up to their name,
286
00:38:35,687 --> 00:38:41,080
Swifts are so specialised for living on the wing,
they can't even land on the ground,
287
00:38:41,247 --> 00:38:46,162
Their tiny legs and long wings would make it
impossible for them to take off again,
288
00:38:47,767 --> 00:38:50,486
That's why they always nest up high,
289
00:38:53,047 --> 00:38:57,086
One mouthful like this
contains up to 500 insects,
290
00:38:57,247 --> 00:39:03,880
and when food is plentiful, the chick
may get ten meals - 5,000 insects in a day,
291
00:39:08,287 --> 00:39:14,886
But in bad weather, most insects are grounded,
and the parents have a hard job finding food,
292
00:39:23,527 --> 00:39:29,397
Sometimes, the adults have to desert
their chicks and fly ahead of the storm to feed,
293
00:39:36,687 --> 00:39:40,077
A British swift will even cross the sea to Europe,
294
00:39:51,767 --> 00:39:57,046
A trip to Holland's no big deal when you can
cover more than 180 miles in a day,
295
00:40:03,087 --> 00:40:04,440
Back at the nest,
296
00:40:04,607 --> 00:40:10,284
the helpless chick can only wait
whilst the adults feed in fair continental skies,
297
00:40:16,527 --> 00:40:22,204
Another day, and still the chick waits,
living on its fat reserves,
298
00:40:28,527 --> 00:40:30,677
Swift chicks are tough,
299
00:40:30,847 --> 00:40:36,877
They can lose half their bodyweight, surviving
for days without a meal, but there is a limit,
300
00:40:37,047 --> 00:40:40,005
This chick needs to eat, and soon,
301
00:40:41,887 --> 00:40:48,122
The parent is in sight of home, after
a round trip of perhaps 1,000 miles or more,
302
00:40:58,887 --> 00:41:02,800
It's just in time to deliver a life-saving meal,
303
00:41:06,927 --> 00:41:14,003
Millions of years of chasing tiny-winged insects
have shaped swifts into true aerial aces,
304
00:41:16,247 --> 00:41:22,117
Amazing to think that they started as feathered
dinosaurs that clambered around in the trees!
305
00:41:38,167 --> 00:41:42,399
Central America is home to the swift's
closest living relatives -
306
00:41:42,567 --> 00:41:47,800
a group of birds that have pushed flight
along a very different evolutionary track,
307
00:41:49,287 --> 00:41:51,562
Hummingbirds.
308
00:41:52,447 --> 00:41:57,202
Hummingbirds can fly
backwards, forwards, up and down,
309
00:41:57,367 --> 00:41:59,756
and all with unbelievable precision,
310
00:42:13,767 --> 00:42:17,555
These aerobatics are unrivalled among birds,
311
00:42:18,927 --> 00:42:22,044
And all because of flowers.
312
00:42:25,287 --> 00:42:28,802
But how did flowers lead to such fancy flight?
313
00:42:28,967 --> 00:42:34,519
Over millions of years, hummingbirds
and plants have struck up an evolutionary deal,
314
00:42:35,447 --> 00:42:40,521
The hummingbirds get to drink nectar
in return for pollinating plants,
315
00:42:45,287 --> 00:42:49,724
And hovering has proved
the most efficient way to get a meal,
316
00:42:51,207 --> 00:42:58,238
It's a relationship that's been perfected until
bird and flower fit together like a key in a lock,
317
00:43:00,527 --> 00:43:04,964
Plants have forced hummingbirds
to become more like feathered insects,
318
00:43:05,127 --> 00:43:10,042
At first glance, it's hard to tell
a hummingbird from a hummingbird hawkmoth,
319
00:43:14,967 --> 00:43:19,085
It's a great example of what's known
as convergent evolution,
320
00:43:19,247 --> 00:43:25,004
where two entirely unrelated animals find
almost identical solutions to the same problem,
321
00:43:39,847 --> 00:43:44,602
But the hummingbird’s supreme
flying ability comes at a great cost.
322
00:43:46,287 --> 00:43:49,359
Their wings flap an amazing 80 times a second,
323
00:43:49,527 --> 00:43:53,964
needing flight muscles twice as big
as those of other birds,
324
00:43:57,687 --> 00:44:01,282
Their heart beats an astonishing
1200 times per minute -
325
00:44:01,447 --> 00:44:05,076
nearly 20 times faster than yours or mine,
326
00:44:05,807 --> 00:44:11,484
To fuel all that, a hummingbird eats
roughly half its weight in sugar every day,
327
00:44:11,647 --> 00:44:16,675
They're slaves to their own lifestyle,
locked in a never-ending quest for food.
328
00:44:18,087 --> 00:44:23,081
And they can only achieve such precision flying
by staying very small,
329
00:44:25,447 --> 00:44:27,597
Swans have the opposite problem.
330
00:44:27,767 --> 00:44:31,680
They're so heavy that just
getting into the air is a struggle.
331
00:44:31,847 --> 00:44:33,326
Come on, then. Come on!
332
00:44:33,487 --> 00:44:35,523
Come on, swans! Come on.
333
00:44:35,687 --> 00:44:37,405
Come on, swans. Come on.
334
00:44:37,567 --> 00:44:39,683
Come on. Up you go.
335
00:44:39,847 --> 00:44:41,838
Come on, boys and girls.
336
00:44:42,007 --> 00:44:43,998
Here we go.
337
00:44:52,527 --> 00:44:54,165
Fantastic!
338
00:44:54,967 --> 00:44:56,685
Look at that!
339
00:44:57,887 --> 00:44:59,400
Hello!
340
00:45:04,047 --> 00:45:06,925
Oh, yes! Look at you.
341
00:45:07,087 --> 00:45:08,998
You beauties!
342
00:45:15,447 --> 00:45:18,917
Swans are one of the heaviest of all flying birds.
343
00:45:19,087 --> 00:45:25,845
They're like the bird equivalent of a jumbo jet,
so they take a lot of energy to get into the air.
344
00:45:26,007 --> 00:45:33,277
Once they're up in the air, it's all about saving
energy, and that's why they fly in this formation.
345
00:45:34,887 --> 00:45:36,764
By sticking close together,
346
00:45:36,927 --> 00:45:42,081
each bird gains a little extra lift
from turbulence created by the bird in front,
347
00:45:42,247 --> 00:45:45,557
It's enough to make a 50% energy saving,
348
00:45:58,287 --> 00:46:02,326
And when you’re this big,
landing is also a problem.
349
00:46:02,487 --> 00:46:05,001
OK, girls.
350
00:46:05,167 --> 00:46:07,522
OK, here we go.
351
00:46:07,687 --> 00:46:10,076
Whoa! Skids down...
352
00:46:21,847 --> 00:46:23,405
Perfect.
353
00:46:32,487 --> 00:46:36,878
I don't think I have ever seen anything
quite as spectacular as that.
354
00:46:37,047 --> 00:46:39,277
That is unbelievable.
355
00:46:41,327 --> 00:46:43,921
I think you deserve a treat after that.
356
00:46:45,807 --> 00:46:48,685
Easy! There we go.
357
00:46:48,847 --> 00:46:51,407
Very good.
358
00:46:52,687 --> 00:46:55,360
Thanks to that first feathered dinosaur,
359
00:46:55,527 --> 00:46:59,918
today, more than 9,000 species of bird
fill the air
360
00:47:00,087 --> 00:47:03,397
across every continent,
361
00:47:04,607 --> 00:47:07,997
(MUSIC)
362
00:48:28,087 --> 00:48:31,716
And the eagle is the king of them all.
363
00:48:32,567 --> 00:48:37,436
The ultimate symbol of power
and dominance of the skies.
364
00:48:39,647 --> 00:48:45,756
But like most birds, it does have a weakness -
its eyes work best in daylight,
365
00:48:46,967 --> 00:48:49,606
That left the night sky up for grabs,
366
00:48:49,767 --> 00:48:53,237
and another family of animals
seized their chance.
367
00:48:54,567 --> 00:48:55,886
(CLICK)
368
00:48:56,407 --> 00:49:00,685
Bats. Some of the most mysterious
of all animals.
369
00:49:02,087 --> 00:49:06,205
Creatures of the night
that can find their way around in darkness,
370
00:49:06,367 --> 00:49:09,165
and live secret lives in deep, dark places.
371
00:49:10,087 --> 00:49:13,716
But perhaps their biggest secret
is how they evolved.
372
00:49:23,887 --> 00:49:27,004
Bats are descended
from a small nocturnal mammal
373
00:49:27,167 --> 00:49:32,287
that took to the trees in search of prey,
like tree shrews do today,
374
00:49:43,807 --> 00:49:48,323
They probably began to glide on skin flaps
stretched between their limbs,
375
00:49:48,487 --> 00:49:51,206
like flying squirrels and sugar gliders,
376
00:49:51,447 --> 00:49:53,881
(MUSIC)
377
00:50:21,447 --> 00:50:25,520
It's a great way to get around,
but still not real flight -
378
00:50:25,687 --> 00:50:28,645
more like free-falling with style,
379
00:50:34,967 --> 00:50:38,357
But it's the colugo
that may provide the missing link
380
00:50:38,527 --> 00:50:40,882
to show how bats evolved true wings,
381
00:50:41,047 --> 00:50:45,086
The difference is in its hands - they're webbed,
382
00:50:50,007 --> 00:50:52,680
The bat's ancestor had these, too,
383
00:50:52,847 --> 00:50:59,764
but its fingers got longer and the skin between
them stretched to turn hands into wings,
384
00:50:59,927 --> 00:51:03,237
Eventually, it flapped these wings and took off,
385
00:51:03,407 --> 00:51:06,604
making bats the fourth and final group
386
00:51:06,767 --> 00:51:11,522
after insects, pterosaurs and birds,
to really fly,
387
00:51:12,847 --> 00:51:16,362
You might think that one bat
is pretty much like any other,
388
00:51:16,527 --> 00:51:20,918
but they're one of the most widespread
and diverse of any kind of mammal.
389
00:51:21,087 --> 00:51:25,558
This one is a fit bat
and, apparently, likes his banana.
390
00:51:25,727 --> 00:51:28,287
Go on. Get that into you.
391
00:51:29,247 --> 00:51:32,603
I think you really have bitten off
more than you can chew.
392
00:51:35,087 --> 00:51:39,558
Fruit bats like this flying fox
are the biggest of all bats,
393
00:51:39,727 --> 00:51:43,276
They have a wing span of up to five feet,
394
00:51:45,167 --> 00:51:49,285
They spend the day crowded together
in their favourite trees,
395
00:51:50,647 --> 00:51:53,684
There can be millions in a single colony,
396
00:51:59,767 --> 00:52:04,158
Then, as dusk falls, there's a mass exodus,
397
00:52:04,807 --> 00:52:11,201
The power of flight means they can cover up
to 30 miles a night in search of the ripest fruit,
398
00:52:16,487 --> 00:52:21,003
No other mammal puts on a show quite like this,
399
00:52:21,167 --> 00:52:24,557
(MUSIC)
400
00:52:45,087 --> 00:52:49,160
Bats are now one of the most successful types
of mammal on Earth,
401
00:52:49,327 --> 00:52:54,720
There are nearly 1,000 species,
each with its own special habits,
402
00:52:54,887 --> 00:52:57,401
Many are fruit lovers,
403
00:53:00,367 --> 00:53:02,927
Others sip nectar,
404
00:53:11,687 --> 00:53:14,884
Other bats have even learned to fish,
405
00:53:25,847 --> 00:53:30,398
But what most like to eat
is a big fat juicy insect,
406
00:53:33,167 --> 00:53:36,716
Bats need more than wings
to track down food in the dark,
407
00:53:36,887 --> 00:53:41,642
These creatures of the night had to evolve
a new way of mapping out their world,
408
00:53:45,967 --> 00:53:51,997
They listen to the echoes of their own calls
and create an image of their surroundings,
409
00:53:52,167 --> 00:53:54,158
(CHIRPING)
410
00:53:54,327 --> 00:54:00,766
It's called echolocation, but how did
such a complex system evolve?
411
00:54:00,927 --> 00:54:03,157
(ECHOING CLICKING)
412
00:54:05,327 --> 00:54:08,876
It's likely bats began
by using simple clicking sounds
413
00:54:09,047 --> 00:54:13,006
which gave them just a very rough picture
of what's around,
414
00:54:14,087 --> 00:54:18,000
But detecting even basic shapes
is better than flying blind,
415
00:54:22,807 --> 00:54:25,719
Then, by using
a more complex range of sounds,
416
00:54:25,887 --> 00:54:28,526
echolocation was improved,
417
00:54:31,927 --> 00:54:36,682
Bats were gradually able to pick up
smaller details in their surroundings,
418
00:54:36,847 --> 00:54:40,283
including their prey,
419
00:54:40,447 --> 00:54:41,926
(CLICKING)
420
00:54:42,087 --> 00:54:45,716
Insects filled the night sky
long before the bats arrived,
421
00:54:45,887 --> 00:54:50,165
They were a meal waiting to happen,
and the bats tucked in,
422
00:54:50,327 --> 00:54:51,646
(CLICKING)
423
00:54:52,527 --> 00:54:55,439
(CLICKING)
424
00:55:05,807 --> 00:55:09,163
There seems to be no limit
to their sensory perception,
425
00:55:20,087 --> 00:55:22,999
Using its finely-tuned echolocation skills,
426
00:55:23,167 --> 00:55:28,321
the Natterer's bat can even pluck a spider
from its web without becoming entangled,
427
00:55:29,527 --> 00:55:32,246
(CLICKING)
428
00:55:40,527 --> 00:55:42,040
(CLICKING)
429
00:55:42,207 --> 00:55:46,200
Once it's got its prize,
the bat goes instantly into reverse,
430
00:55:46,367 --> 00:55:51,964
keeping its wings clear of the sticky threads
with just millimetres to spare,
431
00:55:54,447 --> 00:55:58,326
The ultimate refinement of seeing with sound,
432
00:56:06,687 --> 00:56:09,997
Bats were the last group of animals
to get airborne,
433
00:56:10,167 --> 00:56:12,601
and like all aerial creatures,
434
00:56:12,767 --> 00:56:17,204
they've used their wings to reach
almost every part of the globe,
435
00:56:18,807 --> 00:56:22,766
Their sheer numbers are testament
to the success of flight,
436
00:56:27,607 --> 00:56:31,759
Being able to fly is one of evolution's
greatest triumphs,
437
00:56:44,727 --> 00:56:48,481
Through countless twists and turns
along life's journey,
438
00:56:48,647 --> 00:56:55,086
the power of flight has shaped some of the
most successful animals that have ever lived,
439
00:57:07,047 --> 00:57:13,361
Today's winged creatures make up around
two-thirds of all the species on the planet,
440
00:57:23,287 --> 00:57:26,882
And yet they're all descended
from just four ancestors
441
00:57:27,047 --> 00:57:31,325
who managed to grow wings
and take to the air,
442
00:57:34,087 --> 00:57:39,320
We humans have always dreamed
of joining them, and now we can,
443
00:57:39,487 --> 00:57:41,318
Well, almost!
444
00:57:41,487 --> 00:57:45,162
We do need a little bit of help -
from something big, noisy,
445
00:57:45,327 --> 00:57:48,160
and compared to what evolution has created,
446
00:57:48,327 --> 00:57:50,363
rather crude!
447
00:58:17,047 --> 00:58:19,197
Next week on the “Journey of Life”,
448
00:58:19,367 --> 00:58:23,485
I'm going to discover how relationships
between all living things
449
00:58:23,647 --> 00:58:26,798
have shaped the variety of life we see today,