Why don't animals have wheels?

[banquo's_bumble_puppy]

This is my strangest thread yet. Why don't animals have wheels? Is it because wheels are an energy inefficient method of getting around? We see wings, legs, fins and flippers....yet no wheels.

[PatKelley]

Best suited to a flat surface- which isn't that prevalent on earth. A couple of close matches, though- tumbleweeds are spherical, and essentially shaped to bounce or roll along a relatively flat desert terrain dispersing their seeds. Linear wheels like on a car, though... very easy to get bogged down in mud, not effecient in water (should the animal need to go there or navigate water), and motorizing a wheel would be the biggest problem of all. Very little in the animal kingdom works off of torque - there are a few seeds that come to mind, flagellum, and perhaps a few boring insects. The lever is apparently a simpler machine and more often the favored mechanism.

[banquo's_bumble_puppy]

answer makes good sense...thanks :D

[mid]

Wheels require an axle. 'Growing' an axle doesn't strike me as an easy thing to do; you can't run veins to the rotating part, or they'll twist themselves round it - even an owl's head only rotates so far before it has to come back again.

[Gullible Jones]

Grow the axel in a blood-filled cavity, and make sure it has a lot of holes in it.

[davep]

http://www.dslnorthwest.net/~danwilcox/wheels.htm might be of interest.

[pghnative]

Grow the axel in a blood-filled cavity, and make sure it has a lot of holes in it.Except you need two such cavities (one coming and one going), which would need to be concentric to work.

[jja]

I once tried to design animals based on the simple machines (wedge, screw, etc.) in order to show why the lever is the best solution. %?) I tried to address the axle problem here:

http://pageatatime.com/2004/081204.html

As the sage might say, this auger's ill.

[beskeptical]

Not only does the rotating axle not allow a good blood supply, if you used the blood filled cavity idea you have a problem with the sealing the cavity and with a mechanism for a pressure and O2 gradient.

Oxygen exchange occurs in capillaries, not in veins or arteries. The reason is in the capillary the red cells go through single file and pass close to the tissues being perfused. At that point there is a chemical gradient that causes O2 to diffuse out of the blood vessel and CO2 to diffuse in. It wouldn't be efficient in a 'pool' of blood.

Then you have the blood flow problem. The heart pumps the blood but after the capillary the force exerted from the heart pump is completely dissipated. From the veins back to the heart you have a low pressure system. Inhaling not only pulls air into the lungs via a pressure gradient, it also pulls blood back toward the heart via a pressure gradient thus assisting the heart pump.

How would you arrange this flow through a cavity along the route without getting a problem where the blood was pooling in the cavity? And to get the blood to pass near the tissues, not just in the axle but also in the wheels, the blood would have to flow into the cavity then into the axle and wheels then back out into the cavity (or a second separate one and how would you structure that?). It just isn't conducive to blood system anatomy.

[pghnative]

How would you arrange this flow through a cavity along the route without getting a problem where the blood was pooling in the cavity? And to get the blood to pass near the tissues, not just in the axle but also in the wheels, the blood would have to flow into the cavity then into the axle and wheels then back out into the cavity (or a second separate one and how would you structure that?). ....It would need to be a second one, in order to maintain a fluid pressure gradient which drives the flow. So it would need to be concentric. Very difficult to engineer. (Though an Intelligent Designer could do it --- but that's another thread.) Another problem is sealing the gap between the rotating parts and the non-rotating parts.

[gopher65]

Surely the god of Evoluation could do it! (Discworld, "The Last Continent" The god of Evoluation was hung up on trying to create elephants with wheels for quite some time before he finally gave up)

[Gillianren]

(though Terry Pratchett did spell the word correctly.)

those elephants fell over a lot, too, because of the whole "the veldt isn't flat" thing.

[PatKelley]

An easier method would be a mollusk-like shell grown with a retractable mantle, enabling wheel growth, and a "foot" to drive the wheel without actual connections.

Gastropods kind of make their own rapidly decaying roads (mucous trails) to smooth their transit over terrain.

[Izunya]

One reason I haven't seen anyone mention yet: what would be the intermediate forms?

I mean, as near as we can tell, eyes evolved from little one-nerve doohinguses (doohingi?) that basically sensed light and shadow and that was it. There are still worms out there that use this system, because they've never really needed more. And we can easily figure out what benefit it has for the organism: the worm gets steered to cool, dark, damp places, rather than bright, hot spots (like sidewalks) where it will quickly fry. This is the way evolution works. Even the clunky, buggy version 1.1 has some positive benefit to the organism.

With this in mind . . . how the heck would you evolve an axel?

There are only two kinds of wheel I can really imagine evolving on their own (gengineering changes the whole picture). One is pretty much PatKelley's ball-and-socket design. Mollusk-style "foot" wrapped around a ball, which is not living tissue and doesn't require blood flow. I first envisioned the ball being something like a pearl, perhaps--a hard, excreted mass, possibly even evolved for the same reasons as pearls--but when I think about it, it might be better if the ball was somewhat spongey.

The second kind of wheel is closer to the tumbleweed: an organism that is a ball or a wheel.

Izunya

[space cadet]

The Mount Lyell Salamandar, which lives on steep mountainsides, is known to curl its long, thin body into a hoop, and then roll itself out of danger, much like a bicycle tire bouncing down a hillside.

As for an animal with wheels... well, what if it were to curl its legs or claws inward and thus make an axel for, say, something in nature that could be manipulated to act like a wheel... like a hollow log, or a round coconut or melon with a hole poked through it, or some other plant? Ok, that's probably stretching it, but there's got to be something in nature that an animal could use for a wheel. All it would have to do is poke a hole through it, stick its specially evolved legs (they'd have to be really smooth and bony) into the holes and away it would go. Then when it got to its burrow or whatever it could park its little wheel in the driveway and then it would be able to walk around like a normal animal.

[Gullible Jones]

You've been reading HDM, haven't you. :P

[space cadet]

Eh? I don't know what that is. :(

[Gullible Jones]

Pullman's His Dark Materials trilogy features creatures like you described, who use very hard, coconut-like seeds as wheels. There's a symbiosis between them and the plants that produce those seeds... Other than that, I won't provide any spoilers.

It's an interesting idea, because it could actually happen... Well, under certain conditions anyway. The problem is how you'd get an environment which incorporated those conditions.

[Sock Munkey]

Many mollusk shells are long spirals. If such a shell were deeply grooved or had flat stubby protrusions it would work like a propeller when revolved around the body. The inside of the shell would need to be shaped like an internal cam so that flexing of the muscle would spin it.

The critter would likely need counter-rotating shells mouted either side-by-side or fore and aft because of torque.

Aside from that last factor I see no reason why it couldn't happen.

[Maksutov]

This is my strangest thread yet. Why don't animals have wheels?[edit]
Mainly because they can't afford them, since the large majority of animals either don't have jobs or affluent parents. The few animals that do have jobs typically don't get paid for them; they just get room and board, and, in many cases, a rather predictable life and death.

Of course some animals do have wheels, such as Rin-Tin-Tin (http://www.bumpkinproductions.co.uk/page.php?domain_name=bumpkinproductions.co.uk&view page=Page%20%20Five) and the Taco Bell Chihuahua.

[mickal555]

There's a type of bacteria that uses axel wheels I think...

[hermanpetri]

SockMunkey makes me think he's on to something.

Imagine a creature which curls up into a little ball and enters a chrysallis stage. Excretions from the creature's body produce a nearly spherical shell around it with the creature living in the hollow round inside if the shell. Upon maturity the creature simply walks along the inside surface of the shell just like a hampster running in its wheel.

Legs aren't neccessary for this motivation, sluglike wiggling or any other device which can shift the center of gravity forward or backward would do the trick. Do you all remember those little weasel balls sold around the holidays? It's a sphere with a little off-axis weight moving on the inside. Something like that.

The creature would be severly restricted in its ability to sense the world outside of the shell however, but entry and egress would be possible merely by having a large enough hole in the side of the shell centered on the axis of rotation (like the hole in the center of a tire). Or better yet, the shell doesn't have to be completely spherical. It could be just exactly like walking along the inside rim of a tire. This would open up the possibility of having better perception of the outside world.

Not a practical design by any means I admit - but possible I think. Now whether or not this qualifies as a wheel in the sense that everyone has been suggesting is questionable.

EDIT: An evolutionary precursor to this scenario could be suggested in that the shell originally functioned merely to provide protection for the creature while it metamorphosises during its pupa stage (thus the exit hole later).

[Maksutov]

Human evolution has already taken a detour in that direction. (http://www.bizitairproducts.com/waterball.htm#)

[Van Rijn]

There's a type of bacteria that uses axel wheels I think...

You are probably thinking of bacterial flagella (http://en.wikipedia.org/wiki/Flagellum#Bacterial_flagellum) which act much like screw propellers with something like a shaft and bearings.

[Chip]

Sow bugs will curl up into a ball and roll away if in trouble. I think some Millipedes can temporarily form wheels with their bodies. Once, in Arizona, I observed a spider tuck her legs up and roll down the side of a ditch, then unfold and scramble away. Not the same yet not unlike those rolling robots in Star Wars. Sorry, I'm not an Entomologist, otherwise I'd look them up. :o

[Izunya]

Sow bugs will curl up into a ball and roll away if in trouble. I think some Millipedes can temporarily form wheels with their bodies. Once, in Arizona, I observed a spider tuck her legs up and roll down the side of a ditch, then unfold and scramble away. Not the same yet not unlike those rolling robots in Star Wars. Sorry, I'm not an Entomologist, otherwise I'd look them up. :o

Hey, I forgot all about pill-bugs! Not sure what the real scientific name for these critters--they're little, they're grey, my sister and I called them rolypolies when we younger, they look kind of like a millipede that never got past its first deca. You've seen 'em.

I'm not sure how good the ball is for rolling away from trouble. I can attest that if you have a number of stiff grass stems and a gentle touch, you can get together a nice game of micro-croquet. (Shades of Alice.) Doesn't seem to hurt the bugs, either, although I have no way of knowing how dizzy they would be when we finished with them.

Yeah . . . this is an insomniac post, so be warned, but the more I look at it the more I think curling up into a wheel is the way to go. My demented mind is feeding me something that looks like a hedgehog, but with all-terrain treads instead of spines . . .

One problem, although I suspect it's surmountable; apply this design to most earthly critters, and they're tucking their sensory organs inside the ball. You might need something with a head more like a hammerhead shark, just to get those eyeballs out where they're useful . . .

Okay, just a run-away brain, happens every day, nothing to see here. I'll catch up to you guys in the morning.

Izunya

[Maksutov]

Of course, M.C. Escher was ahead of the field when it came to this subject. (http://www.clowder.net/hop/curlups/curlups.html)

[PatKelley]

The largest and potentially most insurmountable problem in my own view is motorizing an axel or wheel. Rolling is different from actual locomotion, in that the former relies on an outside source (gravity, wind) for propulsion.

The way I'd see it developing is from a grinding feeding apparatus, eventually turning into a quick locomotive resource for an otherwise sessile creature - kind of how shell-snapping is used for propulsion in the scallop. I'd also see a rim-driven rather than axel design as possibly more practical; one could make an abrading grinding surface as a circle by constant extrusion, while at the same time holding and driving the rotor with a single appendage.

[beskeptical]

How would you arrange this flow through a cavity along the route without getting a problem where the blood was pooling in the cavity? And to get the blood to pass near the tissues, not just in the axle but also in the wheels, the blood would have to flow into the cavity then into the axle and wheels then back out into the cavity (or a second separate one and how would you structure that?). ....It would need to be a second one, in order to maintain a fluid pressure gradient which drives the flow. So it would need to be concentric. Very difficult to engineer. (Though an Intelligent Designer could do it --- but that's another thread.) Another problem is sealing the gap between the rotating parts and the non-rotating parts.Designing an in and out blood system still has to overcome the movement of the axle so how would that work? You'd have to have an absurd valve system that opened to the arterial side for the incoming blood and the venous side for the outgoing blood while closing for the reverse. It just wouldn't work.

[beskeptical]

Sow bugs will curl up into a ball and roll away if in trouble. I think some Millipedes can temporarily form wheels with their bodies. Once, in Arizona, I observed a spider tuck her legs up and roll down the side of a ditch, then unfold and scramble away. Not the same yet not unlike those rolling robots in Star Wars. Sorry, I'm not an Entomologist, otherwise I'd look them up. :oSo one could go downhill only?

[beskeptical]

There's a type of bacteria that uses axel wheels I think...

You are probably thinking of bacterial flagella (http://en.wikipedia.org/wiki/Flagellum#Bacterial_flagellum) which act much like screw propellers with something like a shaft and bearings.Single celled animals absorb nutrients and O2 directly. They don't have to deliver them via a blood stream.

[beskeptical]

The largest and potentially most insurmountable problem in my own view is motorizing an axel or wheel. Rolling is different from actual locomotion, in that the former relies on an outside source (gravity, wind) for propulsion.

The way I'd see it developing is from a grinding feeding apparatus, eventually turning into a quick locomotive resource for an otherwise sessile creature - kind of how shell-snapping is used for propulsion in the scallop.Got it up to here. I'd also see a rim-driven rather than axle design as possibly more practical; one could make an abrading grinding surface as a circle by constant extrusion, while at the same time holding and driving the rotor with a single appendage.Huh? I can't picture what you are describing here. Whether connected to the 'rim' or the center via an axle, you still have to have a connection that can rotate without twisting up.

[publiusr]

Now how do you evolve the differential and the shocks?

---or the cup-holder? #-o

[PatKelley]

The largest and potentially most insurmountable problem in my own view is motorizing an axel or wheel. Rolling is different from actual locomotion, in that the former relies on an outside source (gravity, wind) for propulsion.

The way I'd see it developing is from a grinding feeding apparatus, eventually turning into a quick locomotive resource for an otherwise sessile creature - kind of how shell-snapping is used for propulsion in the scallop.Got it up to here. I'd also see a rim-driven rather than axle design as possibly more practical; one could make an abrading grinding surface as a circle by constant extrusion, while at the same time holding and driving the rotor with a single appendage.Huh? I can't picture what you are describing here. Whether connected to the 'rim' or the center via an axle, you still have to have a connection that can rotate without twisting up.

Rim drives are somewhat out-there technically, but there are (or were) rim-driven masonry saws that operated without a central axle. It would be a step up from a simple rough sphere that could be rotated in any direction; also rim-driven. The connection would be ball-and-socket for the sphere, with the socket providing holding and drive. Linear wheels would be an extension of this to a "hollow" design that allows the driving muscles to encircle one edge-to-center section of the wheel, and by driving forward or backward rotating the shell-wheel.

[pghnative]

How would you arrange this flow through a cavity along the route without getting a problem where the blood was pooling in the cavity? And to get the blood to pass near the tissues, not just in the axle but also in the wheels, the blood would have to flow into the cavity then into the axle and wheels then back out into the cavity (or a second separate one and how would you structure that?). ....It would need to be a second one, in order to maintain a fluid pressure gradient which drives the flow. So it would need to be concentric. Very difficult to engineer. (Though an Intelligent Designer could do it --- but that's another thread.) Another problem is sealing the gap between the rotating parts and the non-rotating parts.Designing an in and out blood system still has to overcome the movement of the axle so how would that work? You'd have to have an absurd valve system that opened to the arterial side for the incoming blood and the venous side for the outgoing blood while closing for the reverse. It just wouldn't work.
When you say "it just wouldn't work", I'm not sure what you mean. Do you mean that it can't be done at all? A mechanical engineer with a simple pump, some piping, a couple of mechanical seals and some spare time could do this easily. More difficult to scale it down to the size of your average rodent, but it could be done.

Basically, try to think of a vein inside an artery. These are on the non-rotating side. The vein leads to a rotating cavity. The artery leads to a larger rotating cavity which encircles the vein's cavity. In the rotating side (which is still, from it's perspective) it is simple enough to branch off capilaries from the cavity to the rest of the tissue and back to the other cavity. The difficulty is in sealing the gaps between the rotating and non-rotating parts.

I suppose another way to do this would be to have each wheel be able to take care of its material transport independantly from the main body. So each wheel would have tiny lungs, heart, etc...

[Chip]

Sow bugs will curl up into a ball and roll away if in trouble...So one could go downhill only?

Yup. Its more a defence mechanism than a means of locomotion. They become remarkably spherical, so if the ground is smooth and there's a slight hill, they roll very well.

[PatKelley]

I dont' know why I didn't think of this earlier- but a hamsterball design, with an organism extruding a nonliving shell and then reducing its own volume to the lower half and simply walking up the sides - shell plus mobility, primarily for those with transparent shells or chemoreceptors instead of vision. More than a few holes and you've got the means for a mobile filter-feeder.

[Van Rijn]

There's a type of bacteria that uses axel wheels I think...

You are probably thinking of bacterial flagella (http://en.wikipedia.org/wiki/Flagellum#Bacterial_flagellum) which act much like screw propellers with something like a shaft and bearings.Single celled animals absorb nutrients and O2 directly. They don't have to deliver them via a blood stream.

Mostly I was responding to the comment (though it is interesting that they have a rotary engine, shaft and bearings). But there are examples in higher life forms where blood isn't used directly - the cornea is supplied with oxygen and nutrients from the aqueous humor and oxygen from the air.

Admittedly it is far less efficient than a blood supply, but I could imagine a shaft and wheel made of largely dead tissue similar to a tree trunk. The shaft could be spun by a ratcheting mechanism pressing on knobs on the side of the shaft. The same may help move aqueous humor-like fluid around the shaft, or perhaps just spinning the shaft would be sufficient. Another system could supply and drain the fluid.