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Imagine a planet whose surface is perfectly spherical, without any kind of obstacles anywhere. In such a world, it would be a competitive advantage for any lifeform to evolve wheels, as transport and logistics would be greatly increased. It could also be used secondarily as a dynamo that could generate energy. The possibilities are endless.

Is it possible for life to evolve wheels in such a situation?

EDIT: there can of course be lakes/seas on the surface of the planet. The solid surface however, is completely level.

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    $\begingroup$ Related : Naturally occurring wheels $\endgroup$
    – DaaaahWhoosh
    Commented Sep 1, 2015 at 13:09
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    $\begingroup$ where there is dung there will always be dung beetle $\endgroup$
    – user6760
    Commented Sep 1, 2015 at 13:18
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    $\begingroup$ Life has already evolved wheels. There are many animals that curl up into a disk or sphere and roll. $\endgroup$
    – Superbest
    Commented Sep 1, 2015 at 23:37
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    $\begingroup$ In Philip Pullman's "His Dark Materials" trilogy, there are elephant-like beings that have developed a symbiotic relationship with trees that produce round seedpods. They use these seedpods as wheels to ride the ancient lava flows that they use as roads. $\endgroup$
    – machine
    Commented Sep 2, 2015 at 2:01
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    $\begingroup$ Related Wikipedia article: en.wikipedia.org/wiki/Rotating_locomotion_in_living_systems $\endgroup$
    – leo
    Commented Sep 3, 2015 at 9:13

15 Answers 15

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There are reasons such a smooth world is unlikely (erosion, no tectonic activity, etc.). However, you can replace "the whole world" by "a sufficiently large part of the world" and the question remains basically the same.

Note: from there the answer assumes that evolving wheels excludes the presence of legs. Having both, or a mixture of the two, is not taken in account.

Anyway, a big problem remains for evolving wheels: vegetation. Vegetation creates obstacles, wheels can be stuck in bushes, etc. Even in the case of small plants (e.g. grass) you have got problems, since plants need and create humus, and wet humus becomes mud. And wheels are very inefficient in mud.

In the case of hard and smooth ground without vegetation (it is unlikely that animals could survive there, but animals can survive in deserts, so why not?), a problem still remains: when it rains, the ground becomes slippery, and if it snows... you are stuck.

But still, if it hardly ever rains and never snows, the ground is smooth, the ground is hard, can animals evolve wheels?

Not really. Because wheels are efficient for gaining high velocity, however, when it comes to abruptly changing your direction legs clearly win. With legs you can easily escape a wheeled predator - just jump out of his trajectory.

Perhaps wheeled herbivores then? But they need vegetation. Wheeled animals eating flying insects by keeping their mouths open (pretty much like a swallow does)? Insects will promptly evolve to fly a little bit higher.

I really cannot figure out how a wheeled animal could be viable.

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    $\begingroup$ Amazing answer, full of creative ideas and hypothetical situations. You win! $\endgroup$
    – ICWiener
    Commented Sep 1, 2015 at 13:33
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    $\begingroup$ I agree with Kolaru, but instead oh wheeled animals/plants, planet Earth does have nearly spherical life (armadillo, woodlouse, desert bushes rolling in the wind, and i'm sorry if my translator put something very strange in the list). They won't have wheels, but turning into a sphere to roll might be an alternative solution ? $\endgroup$
    – Tyrabel
    Commented Sep 1, 2015 at 14:15
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    $\begingroup$ I think wheeled herbivores travelling from oasis to oasis in a salt-plain like desert would have a big advantage over legged ones. $\endgroup$
    – leftaroundabout
    Commented Sep 2, 2015 at 10:56
  • $\begingroup$ The assumption of the question seems to be that there are no obstacles - so the first part of this answer isn't really relevant to the hypothetical question. I'd also add that wheels do not intrinsically prevent you from jumping - what's to say that the wheels aren't on the end of jointed legs? We can jump on a skateboard, for example. Similarly for changing directions, we manage okay when on Skis, and we haven't evolved with them, and wheelchair users, while not quite as agile, are still fairly maneuverable (Watch wheelchair rugby, for example), and again we haven't evolved with them. $\endgroup$
    – Jon Story
    Commented Sep 2, 2015 at 12:46
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    $\begingroup$ I think this answer fails by assuming wheels and legs are mutually exclusive. There is no reason why an animal shouldn't run and then coast by rolling on the hard flat surface, maybe even accelerating further, maybe using the wind or gravity. If you can always revert to using your legs you are never stuck. $\endgroup$
    – BlindKungFuMaster
    Commented Sep 3, 2015 at 9:05
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Sure it is possible.

On earth for example there are several animals that roll up for protection. In case there are circumstances where rolling up to move increases survival chances I predict you will get an Insectus Rollatus sooner or later.

Pedalternorotandomovens centroculatus articulosus

It will likely use this feature to flee predators on exposed, flat surfaces in between safe havens or just plain downhill. Or to follow the wind across great expanses for yearly migrations.

Note: The image is Escher's Curl-up or "Pedalternorotandomovens centroculatus articulosus".

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    $\begingroup$ Interesting Escher image. $\endgroup$
    – Dan Dascalescu
    Commented Sep 1, 2015 at 23:18
  • $\begingroup$ That's really interesting. I will read up more on that $\endgroup$
    – ICWiener
    Commented Sep 2, 2015 at 9:36
  • $\begingroup$ That's a cluster lizard. $\endgroup$
    – Michael Vehrs
    Commented May 19, 2017 at 13:49
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Why add the requirement of there being no obstacles?

The Namibian Wheel spider will turn itself into a wheel and cartwheel down dunes! Evolution strikes again!

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Active wheel is possible. Schematically,

enter image description here

a massive body (blue) is connected to a bony wheel (brown) by muscles (red) which contract and relax in concert to keep the body suspended in a fixed position relative to the center of the wheel. No axles, no gears. The body rotates as well as the wheel. And no, it is not a perpetuum mobile.

A similar design with two wheels is also possible. Two wheels, besides providing better maneuverability, let the body protrude far beyond the wheel outline, achieving better acceleration. I would love to draw it, but... you know.

I have no idea how such creature could evolve. From tortoises perhaps? Or Ganzer eggs?

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    $\begingroup$ That's a really neat structure! $\endgroup$
    – Cort Ammon
    Commented Sep 2, 2015 at 1:40
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Two immediate problems with evolving wheels in place of legs/arms;

  1. From a bio-mechanical point of view, providing continuous power to a wheel is more complicated than the equivalent muscle and joint arrangement used in most limbs. To move efficiently, there would need to be some form of gearing system and, probably, the equivalent of a freewheel mechanism.

  2. It's difficult to grasp anything with a wheel so the creatures would need to evolve other forms of limb in addition to the wheels.

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Wheels would be an evolutionary advantage on any planet with a large flat expanse (even mars will do). The issue with the evolution of wheel is less to do with whether it would be useful as much as biological support and intermediate evolutionary steps.

1) You cannot easily provide blood flow to a wheel from the main body. Any vessels would be twisted and any complex mechanism to avoid this would be subject to shear or friction. This is highly unlikely to evolve. The wheel would have to either be a tool (such as one fashioned by the animal) or a non-living growth like hair or a nail.

2) Simple Darwinistic evolution does not make large jumps. Of course there are places where it looks like it has in earths history but, hey, sometimes reality is stranger (believable) fiction (wow 2 cliches in 2 sentences). A freely rotating wheel (whether it is a nail or tool) would have to have a similar useful structure that evolved first. If it is a tool, it is easy for it to be arms/hands holding onto a fashioned axle through the freely rotating wheel. The only reason I can imagine a nail growing that big is to be a bludgen. Such a weapon would not need to rotate. This means someone more creative than me would be needed to proceed with that direction.

What I am left with, therefore, is simular to the strategy used in the Amber Spyglass (the third book in the "His Dark Materials" trilogy which starts with the more famous "Northern Lights" or "Golden Compass"). A species evolves with a tendral to crack into large rounds seed pods. They eventually find the they can place this evolved axle through the seed pod and use it to roll. They use these on the large expansive cooled lava flows with cover the large plains. This creature is used as an example that in an infinite number of parellel universes almost anything can evolve. It lampshades the fact that logically, this should never occur but explains how it does.

If I were writing this, an artifical axle is far more likely as the tendral would be exposed to extreme amounts of friction whether lubricated or not.

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Actually if there wasn't any obstacles, sails would be much more likely. Using wind to travel over land. Why walk or roll, which both cost energy, when you can catch a breeze and glide/slide/float along the ground?

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  • $\begingroup$ I like the idea of sails. In an ocean-only world, would animals naturally evolve sail-like features? $\endgroup$
    – ICWiener
    Commented Sep 2, 2015 at 9:37
  • $\begingroup$ @Pickle: well, our world is almost ocean-only... and indeed there are creatures with sails. $\endgroup$
    – leftaroundabout
    Commented Sep 2, 2015 at 10:49
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How about instead of asking if wheels would evolve, we think about what kind of conditions a world would need to have to encourage such evolution.

As has been discussed in other answers, wheels aren't particularly efficient for small, variable motions. They'd get stuck in any plant life, and plant life is likely to be a major draw for animals to evolve onto land. So it's unlikely that we'll have a creature that relies totally on wheels for moving around.

So what else could give wheeled creatures an advantage? Perhaps migration is important, and some regular geological event means that animals need to migrate quickly. A couple of wheels together with some way for the animal to push itself around could help it move efficiently over long distances.

But if animals have to travel far, would flight evolve first? Maybe the winds on the planet are incredibly strong and volatile (so animals would keep lower to the ground), or maybe gravity is significantly stronger.

However, as others have mentioned and as discussed here, it would be unlikely for a partial mutation that could eventually lead to wheels to provide enough of an advantage to make the mutation stick around.

What might be more likely is that certain creatures have evolved wheels as a tool, rather than a body part. It could be a symbiosis between certain rolling creatures and other creatures which provide an advantage.

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Looking to what already exists to help with this, you are wanting a larger version of a bacterial prokaryote flagellum. This is a motor composed of a specific collection of proteins to make a rotary drive. This then spins the "tail" which makes a corkscrew shape, propelling the bacteria threw liquid.

enter image description here

Assuming you permit this system to scale up a bit, and the motor is replicated to each side of the creature, I think you could make a crustacean of some kind to use it. The chain-whip appendages attached to the motors would then form a single spoke spiral wheel shape when running, or just lay limp on the ground when still. The crustacean would need a skid plate, I think, so it can propel and steer with only two motors. It then needs very articulate mandibles to collect food while sitting, since these chain wheels would be useless in manipulating things. Make it a scavenger, like other crabs, and I think it is viable enough for a story. Perhaps the chain whip drive can be used for defense also.

The point of a wheel and axle as humans use it is to overcome friction. This makes moving heavy loads far easier, but for the longest time we just used wheels for support and provided the drive by other means. Push cart, horse and cart, slave labor pushing and pulling the pyramid stones on top of logs, etc. If that is what you are thinking, I cant do any better than Kolaru's answer, because I don't think this would come about anywhere: enter image description here

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Possible but not likely. Wheels get stuck in mud, wet sand, have problems getting around vegetation, and don't work that well on ice. Wheels make it harder to hide. If it's icy, you will get eaten or starve to death. It just doesn't make much sense.

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Somebody thinks so. Here is an image of a Polarian, from Piers Anthony's "Cluster" series, as imagined by Wayne Barlowe in his book "Barlowe's Guide to Extraterrestrials."

I don't know if you would count a sphere/ball as a "wheel", but clearly rolling is the method of locomotion here.

enter image description here

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Technically, life on Earth has evolved wheels a few times already. The best known example is ATP-synthase, which is a full blown engine and very successful - as far as I know, all modern Earthly life has it. It's using a proton gradient to produce rotational movement - of course, it would be far from trivial to scale it up to a macroscopic engine, but it shows that it is possible. It indirectly powers your muscles as well, so "raw power" wouldn't be an issue.

How could something like this be used for a macroscopic movement system? Well, the one we have works quite well - a lot of individual strings of muscles are moved to produce macroscopically-useful amounts of force; however, that's a lot easier to do for linear force than for rotational. It's not exactly simple to build a system where a single wheel would be powered by millions of tiny engines working in unison - likely far from the tolerancies and capabilities of biological evolution. A much more likely solution would be to use the same muscles and systems we have, but allowing for rolling the whole body - like Star Wars Droidekas. And indeed, there are animals on Earth that use this form of locomotion - the best known probably being Armadillos and Echidnae.

The major advantage of this system (beyond its relative simplicity) is that you have two forms of locomotion available. Especially on a "flat" world, other animals and plants would tend to favour ways to interrupt the rolling locomotion - say, a forest could have boundaries that simply cannot be crossed while rolling. It's also important to note that rolling is kind of hard to control - it's hard to observe your surroundings and adjust bearings, or even just stop.

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Phillip Pullman's series His Dark Materials featured an elephant like creature that had evolved, not wheels, but for and aft tusks that locked into a wheel shaped nuts. The world on which they lived the lava flowed heavy with some sort of silicate leaving hundred mile long smooth veins through the world. I think it's a clever adaptation and one that we would likely see. If there's a niche life, at least life on earth, will exploit it. In any case the books are worth checking out.

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No

A world without obstacles would be very windy. This would cause early life to be blown back into the sea unless it was able to grip the floor firmly.

Also most legs evolved while we were still underwater where they could also be used as flippers.

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In a small way, this has already occurred in the real world(or atleast there are traces if it being highly probable).

We have the Wheel Spider found in the Namib Desert of Southern Africa.

As per wikipedia

The spider escapes parasitic pompilid wasps by flipping onto its side and cartwheeling down sand dunes at speeds of up to 44 turns per second.

So answering the question, I think it's highly possible.

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