[MUSIC]
Think about this: Wherever you’re sitting right now, chances are there’s a spider
nearby.
Which means there’s also a spider web.
And you should be excited about that, because spider silk is awesome.
Spiders manufacture something stronger, stretchier, or stickier than just about anything humans
have engineered.
A thread of spider silk is nearly invisible, which is why you’ve probably walked through
it with your face.
Yet when it comes to strength, some spider silk fibers rival steel and Kevlar.
Imagine this: A silk cord about the diameter of a garden hose could hold up a passenger
jet.
So how does such a tiny animal weave such an amazing material using nothing but its
rear end?
I wanted to find out, so I went to the American Museum of Natural History to meet Dr. Cheryl
Hayashi, who’s maybe the world’s #1 expert in the science of spider silk.
Everybody knows that spiders make silk, but I don’t think most people realize just how
many kinds of silk spiders make.
There’s over 46,000 described species of spiders – and most spiders make four, five,
six, seven, eight kinds of silk.
So if you do the math, it’s huge!
So this is Nephila clavipes, the golden orb-weaver, and she can make seven different types of
silk.
Seven different kinds of spider silk?
In that tiny little body?
Yeah!
Well, some people don’t think it’s a tiny little body…
It's not the smallest spider I’ve ever seen!
When you look at the golden orb weaver’s trademark web, you’re actually looking at
several different types of silk.
There’s the dragline silk: The spider drags it behind like a climber’s safety rope.
It also makes up the web’s outer frame.
There’s one silk to guide the web’s construction.
The spiral that traps prey, is actually a mix of two more silks: A stretchy silk covered
in a sticky glue-like silk on top.
There’s a cement-like silk to attach the web to whatever it’s hanging on.
There’s a silk for wrapping up prey.
They even wrap their eggs in silk.
Seven different silks, all made by one spider.
So what exactly is this stuff?
Spider silk is made of proteins, and the dominant proteins inside a silk fiber are these specialized
category of proteins called spidroins, which stands for spider fibroins, that are unique
to spiders.
Inside the body, all of the silk glands have liquid protein in them.
So it’s liquid protein, and when I dissect a spider and I take out a silk gland, and
I break the gland open, it has the consistency of honey!
It’s a viscous, gooey substance that’s in there.
And it’s highly-concentrated silk protein.
It kind of makes you wonder what an anatomically correct Spider-Man would look like.
The raw ingredients for every protein chain are twenty amino acids, and the recipes for
these chains are coded in genes.
The order of amino acids in these chains determine what a protein looks like, and what it will
do.
And spider silk proteins are built in a very special way.
Imagine a silk molecule like a long train, made up of different boxcars.
Inside each type of boxcar is a string of amino acids.
In any one type of silk, we see the same boxcars over and over all the way along the train.
This unique pattern is what makes each silk so specialized.
Spiders have cooked up some equally specialized ways to use these silks.
Like the trapdoor spider, which weaves a camouflaged shelter from silk.
The ogre spider, that it casts out a silk net like a fisherman.
Or the redback spider, who weaves a trap in the form of sticky spring-loaded snares.
Other spiders shoot venom-laced deadly silly string silk.
Small spiders can even ride the winds on silk sails, a trick called “ballooning” that
can carry them kilometers into the sky.
To find the origins of spider silk, we have to go a long way back.
This is fossil amber, it’s from a Burmese deposit, and there’s a spider in here, and
this is 100 million years old.
Do you want to touch a 100-million-year-old spider?
I need to be very careful.
I’m holding a piece of the world from 100 million years ago, and there’s a spider
in there that was already making silk like spiders do today?
Yes.
100 million years old!
I can keep this, right?
It’ll be our secret.
Here’s another fossil spider, this one’s not quite as old: only 20 million years old.
Only 20-million-years-old?
Practically yesterday!
This one is just beautiful.
I mean, you can see the spider inside.
It’s posing like a spider!
It knew that we would find it one day, and it was like, “I’m gonna give them a really
good pose.
I’m going to do my best spidering.”
Thank you, I really appreciate it!
But Dr. Hayashi doesn’t just study how spiders evolved and how they make silk.
She also studies its mechanical properties.
If you’re picturing her pulling on spider silk with tiny tweezers, you’re not far
off.
This is one strand of dragline silk, that what’s on this card.
She unweaves these single silk strands by hand, and mounts them into a special machine
to test how much pulling it can take before it breaks.
And you can see there’s a fiber connecting that.
So the only thing connecting this part of the machine: this clamp to this clamp, is
the silk fiber.
Can we pull on it?
We can pull on it!
We’re going to break this spider silk so good.
[SUSPENSEFUL MUSIC]
Weight for weight, almost nothing we humans have invented is as strong, as stretchy, or
absorbs energy as well as some spider silks.
So naturally, we’re trying to figure out how to manufacture and weave this stuff for
ourselves.
The approach is you take the spider silk gene, and you move that silk gene into another organism
such as bacteria, a plant, a silk worm, or even goats.
Goats… like?
Where is it coming out of the goats?
So in the goat, it actually comes out, it’s expressed in the mammary gland.
So it comes out with the milk.
What happens if you drink that milk?
Do you get special powers?
Um, I haven’t tried that myself.
I’m going to market spider silk milk goat cheese.
You heard it first!
Spider goat silk is still experimental, but it shows us something really amazing about
the power of evolution.
With all our tools, and all of our knowledge we haven’t invented a material as awesome
as spider silk.
We’re still no match for millions of years worth of nature’s experiments.
Well, I made a new friend.
I made two new friends.
[SPIDER NOISES]
She's like, waving to the camera.
You know, that's what they say about spiders, you put a camera on them.
I know!
Hamming it up!
Hamming it up.
She's saying "Hi Mom!"