why don't any animals have wheels?

I mean, animals use a plethora of complicated locomotive techniques—

slithering, fins, legs, wings—

but yet, no animal has wheels.

What's really paradoxical about this question

is that us humans seem pretty technologically advanced.

We've mastered the wheel, but we have yet to design something

that fully takes advantage of the limb,

which is why this contraption seems so eerie.

It may be the closest we have come to mimicking

what nature is already quite natural with.

Of course, nature, the source of these miraculous limbs

that we have yet to adequately reproduce,

doesn't use wheels.

The wheel gives a mechanical advantage to the user,

allowing them to move heavy things more easily,

but if the wheel is so simple and seems like such a no-brainer,

why don't any animals have them?

Well, to be sure, let's take a look at the wheel spider.

When escaping from a predator, this spider will turn its body

into what is essentially a tire rolling downhill.

And who can forget tumbleweeds?

These things roll around in the wind, spreading seeds everywhere.

An even crappier example is the dung beetle,

who takes pieces of poop and turns them into rollable balls

that can be easily moved.

But those are examples of rolling, not wheels

as we are looking for them today.

Wheels on axles— something that's a part of a whole,

but yet exists independently of it

and can spin indefinitely in one direction

without having to wind itself back again.

Bacterial flagella actually operate in this manner,

but we don't see it in any larger life form,

which brings us to the first problem of finding wheels on animals.

How can a living wheel be completely separate from the animal

and still receive nutrients and expel waste?

Or, if that wheel was made out of a dead material

the animal produced, like fingernails or hair,

how would it build into the shape of a wheel

while maintaining separation from the host?

For that matter, how does developing a wheel

on your body help you along the way?

I mean, look at a giraffe— having a neck

that's just a little bit longer still means

that you'll be able to reach food that's a bit higher,

you'll have more food, will live longer,

and will have more babies, making longer necks more common.

But if your mutation is a wheel that's only a little bit round,

it doesn't provide the same benefit.

It doesn't equal you making more babies.

And as much as I hate to admit it,

the wheel may be a bit overrated.

Think of it this way— in order for a wheel

to be useful for movement, it sort of requires

a prior invention— roads.

Without a smooth surface to roll on,

like a road or rails, the wheel falls short,

and wings and fins and limbs do a better job

for the terrain found on Earth.

Even when humans knew about the wheel,

they had little use for it across rough terrain

or muddy, debris-ridden streets,

which is why wealthy people in the past

simply got carried around in litter—

no, not rubbish— a litter,

a vehicle that uses no wheels and is carried by people or animals.

Fancy, rich people would get carried around

in chair sedans, but another type of litter

was simply a sling made out of fabric

that would help you carry, say, wounded soldiers

across the terrain of a battlefield.

The modern-day stretcher is an example of a litter.

Okay, so in order for the wheels on your body to be useful,

you have to build roads.

So what gives, animals? Why didn't you ever build roads?

I mean, you guys are capable of some pretty awesome things—

complicated burrows, nests, dams—

why didn't you ever build roads?

Well, this question is fundamental to Richard Dawkins' analysis

of the wheeled animal problem.

He says that the problem with roads

is that they're not selfish enough.

A nest, a burrow, a dam— these are things that you can defend;

that you can build and then only use for your own benefit.

Because hey, you were smart enough and industrious enough to build it,

but roads can be used by anything that stumbles upon it.

I mean, you lost energy and resources to build that road,

while a moocher can just come up and use it anyway

and have time left to make a bunch of babies and prosper.

So the road is a really cool example of how humans got benefits

from breaking the mold and doing things

not just for themselves, but for everyone.

In fact, of all the animals, only humans

have ever invented taxes— money that we force others to pay

to build services that they might not even use.

So the next time you see a wheel, say, "Thanks, wheel.

"You're a great symbol of the fact that humans can cooperate

and be unselfish."

And as always, thanks for watching.

I wheel-y mean that.

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