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字幕 (186 片段)
Thumbnails are super important, guys.
And I’m not talking about the ones
that entice you to click on our videos.
I’m talking about these thumbnails.
Because when you’re an animal with thumbs,
sometimes claws just won’t do.
And some animals only have nails on their thumbs,
because they’re just that helpful.
But exactly how you and I started growing thumbnails,
or any nails really, is still a mystery.
So let’s dive into what scientists have uncovered so far.
[INTRO]
Let’s start with a bit of Nail 101.
The Latin name for a nail is an ungula.
Not to be confused with unguis,
the general term for any kind of thing protruding out of the digits:
claw, hoof, nail, et cetera.
And claws, nails, and hooves do all share some basic parts.
For example, they all contain a protein called keratin,
which gives them their toughness.
But nails are unique
because they feature a flat plate of keratinized skin
that sits on top of a digit and then kind of juts out from there.
Hooves are a little special in their own way,
because most of the animal’s weight is bearing down on them.
Because of that, the plate grows at an angle
and wraps around most of the tip of the digit.
It also means the keratinized bit has to be thicker.
And claws?
Well, if you’ve ever been unfortunate enough
to be at the receiving end of a cat swipe,
you’ll know they’re longer, and more compressed than nails.
For the purpose of this video,
we’re going to stick to just nails and claws…
which thanks to their different forms, are better suited for different tasks.
For example, since they’re pointy,
claws are great for grabbing a thing
and helping that thing rest in the hand…paw…whatever.
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