Why Don't Any Animals Have Wheels?

Hey, Vsauce, Michael here, and today we are going to ask a question—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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