Why haven't any animals evolved wheels?

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Why haven't any animals evolved wheels?

Postby Mega85 » Wed Apr 05, 2017 1:50 am UTC

Surely that would be an improvement for speed.

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Re: Why haven't any animals evolved wheels?

Postby poxic » Wed Apr 05, 2017 2:00 am UTC

There are a few bacteria that have propeller-type flagella, according to the wiki.

There's actually a decently detailed discussion of "why not wheels" also on wiki. No intermediate forms that would survive competition with the simple and powerful intermediate forms of run/walk/swim/slither, for one. Also, nutrient tubes can't be breaking off all the time.
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Re: Why haven't any animals evolved wheels?

Postby Copper Bezel » Wed Apr 05, 2017 8:31 am UTC

Richard Dawkins had an interesting response to this somewhere where he pointed out that wheels are also just not very good at getting around by themselves - they need roads.
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Re: Why haven't any animals evolved wheels?

Postby p1t1o » Wed Apr 05, 2017 9:37 am UTC

Rolling locomotion for speed you say?

https://en.wikipedia.org/wiki/Wheel_spider

Not quite sure if it counts as a "wheel" but still...

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Re: Why haven't any animals evolved wheels?

Postby Liri » Wed Apr 05, 2017 12:23 pm UTC

Read His Dark Materials, of course (it's an example listed in poxic's link). The wheels aren't permanently attached to the animals that use them, instead they coevolved with a tree that drops huge, wheel-like seedpods in order to get around on all the lava flows. They can still walk around normally when not in Sport Mode.

The only time I could think of a biological wheel or rotor being advantageous was with aquatic guys, but as the wiki article helpfully states, it's only more efficient than flapping and flailing around at extremely small scales (e.g. bacteria).
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Re: Why haven't any animals evolved wheels?

Postby Soupspoon » Wed Apr 05, 2017 12:56 pm UTC

The steps (NantiPI!) you'd need to take to produce, say, an elephant on wheels would definitely indicate a directed evolution of some kind. If not a downright misguided one.

(For elephants, I'd suggest tracks...)

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Re: Why haven't any animals evolved wheels?

Postby eSOANEM » Wed Apr 05, 2017 1:19 pm UTC

Even ignoring the question of how good wheels actually are without roads, I suspect they wouldn't evolve (at least not with any significant probability) because the intermediate stages necessary are all substantially disadvantaged with respect to their neighbours. Ultimately, it's because evolution is great at finding local optima but shit at finding global ones
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Re: Why haven't any animals evolved wheels?

Postby sevenperforce » Mon Apr 10, 2017 1:14 pm UTC

As has been pointed out, this discussion begs the question of whether wheels would actually be useful.

It also demands the question of how they would be used.

Rather than a wheel per se; I could see the possibility of some creature developing a spherical keratin nodule embedded inside a socket. No axles, though.

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Re: Why haven't any animals evolved wheels?

Postby Xanthir » Mon Apr 10, 2017 8:09 pm UTC

Yeah, we've developed plenty of those already, just crammed into the wetwork. An exposed one has the significant problem of cushioning and lubrication - internally, we can just use cartilage for that purpose.
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Re: Why haven't any animals evolved wheels?

Postby Sockmonkey » Wed Apr 26, 2017 9:26 am UTC

Wheels made of living tissue would have the problem of needing rotating seals for the blood supply.

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Re: Why haven't any animals evolved wheels?

Postby Soupspoon » Wed Apr 26, 2017 10:49 am UTC

And oscillating otters for imparting angular force.

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Re: Why haven't any animals evolved wheels?

Postby monkey3 » Tue May 09, 2017 2:33 pm UTC

Wouldn't it affect the dexterity ? :mrgreen:
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Re: Why haven't any animals evolved wheels?

Postby madaco » Thu May 11, 2017 10:30 pm UTC

How would these wheels generate motion?

If you had another spinning wheel, you could use gears, of course, but that doesn't let you get started.

It seems easier to combine many small parts that pull or push a little into a larger part that pulls or pushes more, than to take many small parts that cause some small rotation and combine them into a larger part that creates a greater torque. Right?

Suppose you had concentric rings with rotating gears spaced along them (with the axis of rotation being normal to the axis of the ring), where the gears would interface with the ring directly within the ring they belong to, but not with the gears to either side of them (I guess the rings also are gears)

this could work, I guess, but if each of the small "motors" has the same torque, or all "tried" to have some particular rotation period, which was the same for all of them, I feel like that might cause issues.

Basically, the asymmetry from the different rings having different sizes, seems to me like it might cause problems, or at least inefficiencies.

Are there better ways to potentially scale up cell-level rotation to large scale rotation?

If there are no good ways to do that, it seems like you would have to use large scale push/pull in order to create the rotational motion.

Which, maybe if you had circularly arranged contracting things with activation that went around in a cycle?

that doesn't sound particularly efficient to me.

Electric motors seem a bit far fetched to me, because creating a strong electric current is probably hard (though I might be wrong about that. I guess there are those fish that create electric fields? I was thinking about nerve impulses being weak.), and having a conductive part and a magnetic part also seems tough, especially if you want it to be made of cells.

How do cars do it? Pistons, right. Or rather, I guess the term I'm looking for is crank. hm.

There is the issue of getting the rotation started when using a crank if it is at top or bottom dead center, but wikipedia says that that issue is solved in steam locomotives using two rods connected to the wheel.

__

This all seems to suggest that maybe wheels aren't the best sort of thing to use biologically?

Whatever mechanism would also have to have the wear and tear be repairable I think.

The concentric rings idea seems kinda neat to me, but the explicit layers (even if they are very thin layers) seems like it would make automatic repair (i.e. healing) very hard.

I would imagine that the supply of nutrients and nerve signals and other things would have to go across layers in order, so a big enough problem at any one layer could be catastrophic.

Or, maybe if there were only a few signals to it (say, "faster", "slower", "this direction" "the other direction", and "pain" the other way), and there was a hard shell around it, maybe stuff could get through on a surface inside a cavity in the hard shell. I'm not sure how the stuff (in a fluid probably) would get into that cavity.

Are there any methods of having a mostly watertight seal that wouldn't cause a lot of friction?

Hm, what if it went through the central "axle" into the cavity of the shell. Then if...

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________________________
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|    |  cavity | W |  | |
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|    |       _____________
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the regions labeled "W" are the part that produces the motion.


It seems like here, if the muscle section is thin enough and the connections to the outer shell and the "axle" are water-tight, this might work to get fluid through the "axle" to the inner-wheel without leaking, and this could provide the nutrients and signals needed. Assuming, of course, that the "inner wheel" would be thin enough that the stuff in the cavity could permeate through it enough.

The inside of the cavity could maybe be coated with some tissue that would maybe slowly produce material outwards to replace wear done on the outer shell. There might be an issue with ensuring that it grows outwards instead of inwards, and filling up the cavity. I don't know nearly enough biology to know whether that would be a problem.

Unfortunately, I think with this set up, if the shell cracked or otherwise got a hole in it, they would probably bleed out? Not a happy thought. Make the shell thick then, I guess.

Information about pressure on the wheel or rotation to its movement could be detected by pressure on the "axle" and sent back through nerves.

I still don't think this would work all that well, but it seems like it might be possible now, just probably not a good option?
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Re: Why haven't any animals evolved wheels?

Postby p1t1o » Tue May 16, 2017 12:29 pm UTC

tl;dr - because nature didnt produce roads/legs are better.

Wheels not a great choice if the terrain is varied. Wheels great for flat, smooth places, and great for speed - but there will be very many places you cant go. The animals with legs will outcompete you every time. Legs can go over rocks, into the jungle, up sheer cliff faces, through snow, boggy terrain, up trees etc etc.
I'd wager legs are more agile in combat as well (think: being surprised by an ambush predator). Also legs are weapons (kicking).

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Re: Why haven't any animals evolved wheels?

Postby tomandlu » Mon May 22, 2017 12:28 pm UTC

Sorry to tack this onto the end of this thread, but it seems a similar enough question to warrant it.

Why have no large land animals ever evolved a more centaur-like body layout? i.e. 4 or more 'legs' and two 'arms'?

I mean, if you look at, say, big cats hunting, the ability to claw at your prey without having to break your stride (and be at a severe disadvantage if you miss your attack) looks like it would be really useful. Likewise, it's not hard to see the utility for herbivores (able to carry foraged food stuffs to a safer location, etc.).
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Re: Why haven't any animals evolved wheels?

Postby HES » Mon May 22, 2017 12:38 pm UTC

Why go to all the effort of growing an extra pair of limbs when you can just learn to stand on two legs instead?
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Re: Why haven't any animals evolved wheels?

Postby tomandlu » Mon May 22, 2017 1:49 pm UTC

HES wrote:Why go to all the effort of growing an extra pair of limbs when you can just learn to stand on two legs instead?


Speed.
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Re: Why haven't any animals evolved wheels?

Postby Liri » Mon May 22, 2017 2:03 pm UTC

tomandlu wrote:
HES wrote:Why go to all the effort of growing an extra pair of limbs when you can just learn to stand on two legs instead?


Speed.

Centaurs aren't super aerodynamic.
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Re: Why haven't any animals evolved wheels?

Postby gmalivuk » Mon May 22, 2017 2:06 pm UTC

Also, humans can run down pretty much any other animal, even if we can't outrun them over short distances.

More importantly, even if it were a better body plan, evolution finds local maxima, but there's no reason to expect it to jump to a global maximum if there are all sorts of low-fitness body plans between them. Having four limbs (and five digits on each) is a body plan that was established quite early on, and developments since then have all been variations on that theme because slight variants tend to survive better than extra-limbed mutants.
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Re: Why haven't any animals evolved wheels?

Postby Soupspoon » Mon May 22, 2017 3:32 pm UTC

It's around the Late Devonian that Tetrapoda arise out of the various body-plans that got experimented with throughout the likes of the Cambrian Explosion. And once the workability (or sheer luck) of that bodyplan was proven and more complexities (like joint-geometries., though pentadactylity was actually a prior 'invention', it is thought, and it is easier to increase/decrease limb-end digits than limb-pairings in unsegmented creatures... arguably) heaped onto the design it becomes difficult to develop useful limb duplications/additions in a viable manner.

Are centaurs equiniplan creatures who developed arms in their 'necks' above their fore-limbs? Is that really a torso, if horse-lungs/stomachs/heart/etc are expected between the mid- and hindlegs? Alternately, do they develop mid-limbs that (never getting in the way) become foreleg-like enough for the original forelegs and upper spine to rise into the air, free to redevelop into manipulating hands (after losing their hoovened nature and rethinking their equine monodactylity). Ignore for now the classical centaur human-bit being hairless, rippling six-pack, human head form (not suited for grazing), atop a horse body with consistent hair. Poetic licence, probably, the 'true' hexapod form of a centaur being likely more towards Nightmare Fuel, and definitely exotic, rather than a neat chimeric blend of two other creatures.

It likely arises from the mental preconception that a horse has four legs, no arms, whilst a human has only one of those pairs of legs and two arms that the horse does not have (an alternate centaur-development, therefore, could be to have an inverted General Grievous thing, where "the pair of lower legs" of an anthropoform splits into two pairs, developing a horse-torso-like extension to the hips to make the two pairs not awkwardly close together).

Ditto winged creatures. Birds have "just a pair or legs, no arms, wings on their back". Thus add wings onto anthropoforms and you get angel/birdman/manbat creatures, whilst adding them to quadraped (and no-armed) creatures of various kinds gives you pegasi, griffins, dragons. Six-limbed, all of them, but with differing natures to the limb classifications (and often mix-n-match surfafe details. Feathered wings on haired or hairless forms, for example. Leathery wings on Ozish flying primates is probably Ok, as they're battish and bats are hairy mammals with hairless membranes, but those are forelimbs, not back (as in mid-spinal) limbs.

And then how about a winged centaur. Four pairs of limbs. No more limbs-per-type than any of the subchimeric contributors have, but clearly a complexity of muscular-skeletal development that exceeds any easy to understand evolution process. Only really possible by actually mix-n-matching like those flip-books with the divided pages you can use to see a dog's head on a policeman's body atop an astronauts legs, but with the imagination adding the flexibility.

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Re: Why haven't any animals evolved wheels?

Postby tomandlu » Mon May 22, 2017 4:42 pm UTC

Soupspoon wrote:It's around the Late Devonian that Tetrapoda arise out of the various body-plans that got experimented with throughout the likes of the Cambrian Explosion. And once the workability (or sheer luck) of that bodyplan was proven and more complexities (like joint-geometries., though pentadactylity was actually a prior 'invention', it is thought, and it is easier to increase/decrease limb-end digits than limb-pairings in unsegmented creatures... arguably) heaped onto the design it becomes difficult to develop useful limb duplications/additions in a viable manner.

Are centaurs equiniplan creatures who developed arms in their 'necks' above their fore-limbs? Is that really a torso, if horse-lungs/stomachs/heart/etc are expected between the mid- and hindlegs? Alternately, do they develop mid-limbs that (never getting in the way) become foreleg-like enough for the original forelegs and upper spine to rise into the air, free to redevelop into manipulating hands (after losing their hoovened nature and rethinking their equine monodactylity). Ignore for now the classical centaur human-bit being hairless, rippling six-pack, human head form (not suited for grazing), atop a horse body with consistent hair. Poetic licence, probably, the 'true' hexapod form of a centaur being likely more towards Nightmare Fuel, and definitely exotic, rather than a neat chimeric blend of two other creatures.


Heh - quite. I was thinking more along the lines of, say, crabs, lobsters, mantis, scorpions, etc. i.e. there are a lot of non-chordates (or should that be non-vertebrates?) that have a 'centaur-like' arrangement.

Putting this all together, we get (I think), "even if such an arrangement were to have practical benefits in a complex organism, it would have to have been present in simpler ancestors, and either is no benefit to the ancestors, or, for other reasons, never initially arose."

Bottom line, and given its presence in many organisms (unlike evolved wheels), it seems likely that the truth is more complex than a simple "because it's not useful and/or far too biologically complex."
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Re: Why haven't any animals evolved wheels?

Postby Copper Bezel » Mon May 22, 2017 5:14 pm UTC

Hmm, is there any extent to which variations in fish body plans are more plastic, and simply because aquatic locomotion is more forgiving than terrestrial? I know that'd be different from the plasticity granted by segmentation, although - like, insects are a big, old, varied group in the same way land vertebrates are, and they've stuck to their bauplan and only ever reduced and lost existing limbs (wings), too....
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Re: Why haven't any animals evolved wheels?

Postby Liri » Mon May 22, 2017 6:01 pm UTC

With fish, as with land animals, the necessity for speed (or not) generally informs body shape. Eels are predators, but they're mostly ambush types. Rays are filter feeders and don't need to move especially fast. Sharks, meanwhile, can move pretty darn quick. And seahorses do not.

You don't see similar superfast herbivores like antelope and their kin in the oceans. You definitely see a huge deal of variation in body plans among slow herbivores/filter feeders though.
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