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動画の字幕をクリックしてすぐ単語の意味を調べられます!
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Feathers are some of the most remarkable things
ever made by an animal.
They are gorgeous in their complexity,
delicate in their construction,
and yet strong enough to hold a bird
thousands of feet in the air.
Like all things in nature,
feathers evolved over millions of years
into their modern form.
It could be hard to imagine
how this could have happened.
After all, what did the intermediate forms look like?
What good is half a wing,
festooned with half-feathers?
Thanks to science,
we now know that birds are living dinosaurs.
You can see the kinship in their skeletons.
Certain dinosaurs share some anatomical details with birds
found in no other animals, such as wish bones.
And in the late 1990s,
paleontologists started digging up
some compelling support for that idea:
dinosaurs with bits of feathers
still preserved on their bodies.
Since then, scientists have found
dozens of species of dinosaurs
with remnants of feathers.
Some were as small as pigeons,
and some were the size of a school bus.
If you look at how they are related on a family tree,
the evolution of feathers
doesn't seem quite so impossible.
The most distant feathered relatives of birds
had straight feathers that looked like wires.
Then these wires split apart,
producing simple branches.
In many dinosaur lineages,
these simple feathers evolved
into more intricate ones,
including some that we see today on birds.
At the same time,
the feathers spread across the bodies of dinosaurs,
turning from sparse patches of fuzz
into dense plumage,
which even extended down to their legs.
A few fossils even preserved some of the molecules
that give feathers color.
They reveal a beautiful range of colors:
glossy, dark plumage, reminiscent of crows,
alternating strips of black and white,
or splashes of bright red.
Some dinosaurs had high crests on their heads,
and others had long, dramatic tail feathers.
Now, none of these dinosaurs
could use their feathers to fly -
their arms were too short
and the rest of their bodies were far too heavy.
But, birds don't just use feathers to fly.
A woodcock uses feathers to blend in perfectly
with its forest backdrop.
An ostrich stretches its wings over its nest
to shade its young.
A peacock displays its magnificent tail feathers
to attract peahens.
Feathers could have served these functions
for dinosaurs too.
Exactly how feathered dinosaurs took flight
is still a bit of a mystery.
But if a small-feathered dinosaur flapped
its arms as it ran up an incline,
its feathers would have provided extra lift
to help it run faster.
This accident of physics might have led
to the evolution of longer dinosaur arms,
which would let them run faster
and even leap short distances through the air.
Eventually, their arms stretched out into wings.
Only then, perhaps 50 million years
after the first wiry feathers evolved,
did feathers lift those dinosaurs into the sky.
コツ:単語をクリックしてすぐ意味を調べられます!

読み込み中…

【TED-Ed】How did feathers evolve? - Carl Zimmer

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VoiceTube 2013 年 5 月 7 日 に公開
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