How can it be that there exists not a single example of a working wheel in nature?

September 23, 2007 7:26 PM

How can it be that there exists not a single example of a working wheel in nature, which after all gave us (among other things) the eyeball?
posted by It ain't over yet to science & nature (41 comments total)

Why would there be a wheel in nature?
posted by danb at 7:27 PM on September 23, 2007

Nature uses lots of rotary mechanisms. ATP Synthase is a classic example. It's even got axles!
posted by meehawl at 7:28 PM on September 23, 2007 [2 favorites]

How about the tumbleweed?
posted by Guy Smiley at 7:32 PM on September 23, 2007

Evolution works by making small changes to existing biology. The predecessor to any new adaptation must have served a useful purpose.

The eye evolved as a series of progressively more useful sensory organs.

Apparently, evolution never found a path to a fully functioning wheel & axle combination-- half a wheel or a bent axle isn't very useful as a mechanical device.
posted by justkevin at 7:34 PM on September 23, 2007 [2 favorites]

Also, roads or other flat surfaces help a lot if you want to use wheels for efficient transport.

Hey, the tumbleweed made me remember another example. When you get a nick/foreign agent into your body, certain of your body's innate immunity cells become more adhesive and "roll" along the site of damage within your blood vessels, picking up chemical alarm signals like flypaper. They want to collect these to present them to your adaptive immune system. You can watch this in a microscope - it's like a big, sticky rollathon.
posted by meehawl at 7:35 PM on September 23, 2007 [2 favorites]

Think about it mechanically. How would the blood vessels (or other vital "duct-work" if we're talking about non-animals) bridge the necessary gap between a biological wheel and axle?
posted by pmbuko at 7:43 PM on September 23, 2007 [1 favorite]

Why, symbiosis, of course.
posted by IronLizard at 7:46 PM on September 23, 2007

Steven Vogel discusses this question in Cat's Paws and Catapults: Mechanical Worlds of Nature and People. His major points agree with those mentioned above: Nature has created rotary mechanisms: bacterial flagella, for example. However, you may be asking why macro-scale fauna don't employ wheels for travel. Low-friction bearings don't seem to be a problem, as evidenced by our own joints. It may be that the need for smooth surfaces is too high a restriction to make natural wheels useful.
posted by Mapes at 7:53 PM on September 23, 2007

Evolution doesn't result in systematic progress toward an optimal solution.

What we call "evolution" is a post-hoc ascription. The micro-phenomenon that leads to "evolution" is:

If you have kids, you win; if not, you lose.

Which, in my opinion, is a pretty low bar to set. Empirically, I can make the observation that there are an awful lot of ugly people around, given each of them is the culmination of thousands of matings of the most attractive people of every generation. I would argue that evolution is more properly viewed as the result of eons of organisms that are just good enough to git 'er done.
posted by Maxwell_Smart at 8:10 PM on September 23, 2007 [2 favorites]

Do these count?
posted by Partial Law at 8:12 PM on September 23, 2007 [2 favorites]

Possibly because a wheel is next to useless on most natural surfaces without some mechanical advantage to assist it (such as an engine or other source of power) - legs/feet would be far more efficient in almost all situations. It's only when you start using prepared surfaces that a wheel gives any real advantage.
posted by dg at 8:20 PM on September 23, 2007 [1 favorite]

Legs are your wheels. Repeat that.

The civilizations the "never invented the wheel", like the Inca, had no use for a wheel. They had people and animals to carry everything.

Wheels need roads or paths. legs go wherever. Nature chose legs.
posted by kuujjuarapik at 8:27 PM on September 23, 2007 [3 favorites]

From rendez-vous 39 of Richard Dawkins' The Ancestor's Tale:

Bacteria...are also the only non-human creatures known to me who have developed that icon of human civilisation, the wheel.

The wheel may even have been the first locomotor device ever evolved, given that for most of its first 2 billion years, life consisted of nothing but bacteria. Many bacteria, of which Rhizobium is typical, swim using thread-like spiral propellers, each driven by its own continuously rotating propeller shaft. It used to be thought that these 'flagella' were wagged like tails, the appearance of spiral rotation resulting from a wave of motion passing along the length of the flagellum, as in a wriggling snake. The truth is much more remarkable. The bacterial flagellum is attached to a shaft that rotates feely and indefinitely in a hole that runs through the cell wall. This is a a true axle, a freely rotating hub. It is driven by a tiny molecular motor which uses the same biophysical principles as a muscle. But a muscle is a reciprocating engine, which, after contracting, has to lengthen again to prepare for a new power stroke. The bacterial motor just keeps on going in the same direction: a molecular turbine.

Oh, and just for fun, say what you will about the wheel, but New World civilisations still lacked the wheel by the time of the Spanish Conquest. Going back to Dawkins:

Here's another way in which we risk overrating the wheel. It is dependent for maximum efficiency on a prior invention - the road (or other smooth, hard surface). A car's powerful engine enabled is to beat a horse or a dog or a cheetah on a hard, flat road. Bur run the race over wild country or ploughed fields, perhaps with hedges or ditches in the way, and it is a rout: the horse will leave the car wallowing.

Well then, perhaps we should change our question. Why haven't animals developed the road?

He goes on to say that although it is technically feasible, "...it is a dangerous altruistic activity." since it would benefit more than just the person who made the road, and Darwinism is a selfish game. Food for thought.
posted by furtive at 8:44 PM on September 23, 2007 [2 favorites]

re: the purpose, who gets around more easily, people in wheelchairs or people with legs? Wheels are good for moving dead weight over smooth surfaces, but not for the spontaneous self-motivated animal to respond to unexpected terrain.

re: the mechanics, you have to deal with the break between the axle and the outer wheel if you're going to use wheels in the most efficient sense (not just as tumbling roundish things), so you'll need two circulatory systems or some weird slime osmosis thing or something.

previously.
posted by mdn at 8:48 PM on September 23, 2007

Actually there is one example the rhizobium, as documented in Richard Dawkin's fantastic evolutionary opus 'The Ancestor's Tale'. It's "a true axle, a freely rotating hub, driven by a tiny molecular motor" and he goes on at length about it's relevance to evolution (and it's relevance to being used as a counter-evolution argument).
posted by Jezztek at 8:49 PM on September 23, 2007

Doh, I guess I was too late...
posted by Jezztek at 8:49 PM on September 23, 2007

It's not the smooth surface issue. It's that, to be useful, a wheel has to be free-spinning. Animal appendages require some sort of connection, a path for nutrients and nerve impulses and so forth. You can't have a free-spinning wheel that also maintains a connection like this with its host.
posted by zadcat at 9:21 PM on September 23, 2007

Some "New World Civilizations" actually had the wheel, but only seem to have used it in toys, possibly for the infrastructure/road reasons alluded to above. Nonetheless they invented and understood the principle. See "Wheeled Toys in Mexico", by Gordon F. Ekholm, American Antiquity 1946
posted by Rumple at 9:24 PM on September 23, 2007

Dung beetles use something akin to the wheel.

The problem with wheels is that they require bearings capable of an arbitrarily large number of rotations in a single direction. That's radically different than for limbs, because it means you can't pipe or connect easily to anything on the far side of the rotary joint. If you have a critter which has wheels, how does it get blood into and out of the flesh of the wheel?

If it isn't alive, how does it grow? And if it isn't alive, how do you heal damage to it, especially damage and wear on the bearing surface?
posted by Steven C. Den Beste at 9:30 PM on September 23, 2007

In The Amber Spyglass by Phillip Pullman, there is a species that evolved to travel on wheels - there were ancient lava flows that served as roads and seedpods that they hooked their claws into to use as wheels. Of course, that's a fictional book, not real life, but it does provide an example of an environment that's conducive to wheels in nature. They also had a diamond-shaped spine - the front and back legs held the wheels and the side legs pushed. That doesn't really explain why similar wheels don't show up in nature in our world, but it does kind of illustrate the kinds of conditions that would be necessary for that to happen.
posted by brittanyq at 10:21 PM on September 23, 2007 [2 favorites]

What animals or plants would be improved by wheels? It's hard to imagine one. Extant limbs and wings and slithery bits seem much more versatile and practical. Perhaps if wheels would be useful, they could have evolved. I am imagining a mechanism a bit like how I would guess a rattlesnake's tail-rattle might or might not be made: you could have a 'tire' of dead skin that could be produced and sloughed off by a limb that would act as an axle. There might be elaborations hat could reduce wear and tear - lubrication of course,maybe even bearings. If that ever evolved, however, it didn't catch on in a way that got preserved in the fossil record. What I can't imagine is how such a beast wouldn't be totally crap compared to competitors with proper legs. It would also have to have a separate mechanism for propulsion; flatulence, or sails, or something.
posted by nowonmai at 10:34 PM on September 23, 2007

Humans are natural, and we use wheels.
posted by TravellingDen at 10:44 PM on September 23, 2007

Buckeye seeds.
Jumping galls.
posted by the Real Dan at 10:55 PM on September 23, 2007

Barlowe's Guide to Extraterrestrials has an entry on Piers Anthony's Polarians (search for "wheel") - an alien species that has evolved a biological wheel-like organ of transportation.
posted by Guy Smiley at 11:03 PM on September 23, 2007

Well then, perhaps we should change our question. Why haven't animals developed the road?

Animals did develop the road -- they were called humans. It merely required some minimum level of intelligence, and humans were the first on the planet to reach it.
posted by Krrrlson at 11:07 PM on September 23, 2007

Not so much a wheel as a rolling ball but I once saw a 8 inch diameter ball rolling down a creek that turned out to be a clusterfuck of salamanders. I thought someone lost a toy and went to grab it but then watched in awe as it rolled on past.
posted by Iron Rat at 11:16 PM on September 23, 2007 [1 favorite]

a mechanism for a dead tissue wheel that grows is quite easy to imagine. The forks, which are living tissue, lengthen and grow farther apart, and deposit layers of chitinous material on the wheel/axle.
posted by lastobelus at 12:41 AM on September 24, 2007

I have seen film of a revolving ice circle that was big enough for a man to ride.
posted by hortense at 1:23 AM on September 24, 2007

MC Escher pondered this question and created a critter that looked like an armored lizard with six legs. When it needed to go up stairs or over rough terrain, it walked. On a flat surface, it rolled up into a wheel shape, and used its legs to push itself along. It was featured in one of his "impossible building" pictures.
posted by Steven C. Den Beste at 2:25 AM on September 24, 2007

A better question might be why animals larger than bacteria don't generally employ 'rolling' as a means of locomotion. This sidesteps the 'axle' issue which people seem to get hung up on.

Obviously there would be some sensory issues (how do you keep eyes focused on the same spot if you're rolling) but it's hard to believe that neurological accomodations couldn't deal with that.
posted by unSane at 5:55 AM on September 24, 2007

Well then, perhaps we should change our question. Why haven't animals developed the road?

I would argue that animals have developed roads. The cows in the pasture near my house certainly have roads--they always follow the same paths through the fields and have worn a smooth dirt path through the grass. I've driven on a couple of roads that were much less well defined than the cow path.
posted by jtfowl0 at 6:22 AM on September 24, 2007

Hoop Snake!
posted by flickroad at 6:23 AM on September 24, 2007 [1 favorite]

I was thinking the same thing, brittanyq.
posted by Doohickie at 7:11 AM on September 24, 2007

Roly Poly!
posted by iamkimiam at 8:29 AM on September 24, 2007

Setting aside the "There are wheels in nature, on (for instance) The General Lee, which is every bit as natural as a wasp's nest is" viewpoint, I say that wheels exist in nature. Various seeds operate as wheels. Apple falls, rolls a ways, has better chance of being eaten, germinating, whatever.

The question of why there are no wheels with axles in nature, I refer back Zadcat's excellent answer.
posted by dirtdirt at 8:35 AM on September 24, 2007

Are there any other simple machines in nature, independent of human invention? Tools are made by animals, so if you want to distinguish that process from nature, you will not find any tools, wheels or otherwise, elsewhere in biology. You'll find plenty of things similar to the tools, which may be what you meant.
posted by Tehanu at 10:12 AM on September 24, 2007

Hamsters have wheels.
posted by callmejay at 11:32 AM on September 24, 2007 [2 favorites]

Wheels are hard to drive. It's much more efficient to be a creature that walks up a hill than a creature that has to power a wheel to get up a hill.
posted by oneirodynia at 12:21 PM on September 24, 2007

Some "New World Civilizations" actually had the wheel, but only seem to have used it in toys, possibly for the infrastructure/road reasons alluded to above.

It's actually more likely that it's because they didn't have draft animals (horses or cattle) to pull the carts.
posted by oneirodynia at 12:28 PM on September 24, 2007

I think the Wheelers in Ozma of Oz used the method that lastobelus proposes.
posted by booksandlibretti at 6:28 PM on September 24, 2007

Are there any other simple machines in nature, independent of human invention?

Yes, ATP Synthase (see above). It is a molecular engine driven by a single proton motive force, a simple electrochemical potential created by naked hydrogen atoms. It's reversible - run it one way and you get ATP, a high-energy molecule. Run it the other way to consume ATP and you get rotary motion... the basis for flagella and cilia and all kinds of refinements. We have literally zillions of these little motors inside us... a typical 70 Kg human will turn over 40 Kg of ATP a day to supply energy throughout its body.
posted by meehawl at 10:30 PM on September 24, 2007