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Most humans have both arms and legs. This arrangement is quite useful out in nature, but it seems like as technology advances, this anatomy is becoming less and less necessary

Furthermore, space travel will, at least in worlds that respect conservation laws, need to be as low mass as possible. And, it seems like removing unnecessary limbs would be a good step in that direction

While it seems like we could easily thrive with just the arms or just the legs (especially with the right adaptations), I have some doubts about removing all four limbs. Though many people have lived without limbs, I feel that a wholly limbless society may not be able to survive

These humans would be genetically engineered, and so could have some sort of simple adaptations to make up for the lack of limbs. For the sake of lightness, they are around 30cm tall, with smaller organs and very little fat

Could these humans thrive without arms or legs?

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  • $\begingroup$ Well, the Daleks and cybermen seem to do just fine on TV... $\endgroup$
    – DWKraus
    Jan 18, 2022 at 12:02
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    $\begingroup$ One EMP or solar flare frying all their artificial limbs, and they are extinct. $\endgroup$
    – KeizerHarm
    Jan 18, 2022 at 12:05
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    $\begingroup$ @IchthysKing Oh... then, I don't feel qualified to answer. It seems like a horrible thing to do to a society. $\endgroup$
    – KeizerHarm
    Jan 18, 2022 at 12:10
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    $\begingroup$ Daleks! You want Daleks? This is how you get Daleks! Kelads had arms and legs until Davros had a ”better” idea. 😱 $\endgroup$ Jan 18, 2022 at 13:41
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    $\begingroup$ The problem is that the Beaners still need a way to move about the spaceship. And you need to build it to somehow be lighter than the arms and legs we removed. $\endgroup$
    – Daron
    Jan 18, 2022 at 18:54

10 Answers 10

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Nerve Ending Interface.

enter image description here

The Beaners are suitable for space travel because the spaceships are custom built for them. They wear neural readers on each stump that are used to control things around the ship. They still need limbs to move around ala XCOM MEK troopers:

https://static.wikia.nocookie.net/xcom/images/f/fe/XCOM_EW_MECTrooper.png/revision/latest/scale-to-width-down/423?cb=20140121210735

They save weight because they do not need limbs for every activity. The ship carries less than 4 limbs per person. And those limbs are lighter and stronger than meat limbs.

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it's probably a bad idea.

While it's not impossible to live without the limbs, especially so in a society with non-limbless people there to help (Nick Vujicic, born with only a foot, comes to mind), it is far from an optimal choice. To live without having limbs normally means you're sacrificing a lot of things if you don't necessarily have anyone to help you:

  • movement speed. You might still be able to go places, but you're not gonna be fast at it. To be able to move at a decent pace you'll need some sort of electric wheelchair, and for it to be specifically made so that you can get on and off of it and use it by yourself.

  • height. A good chunk of one's height is in their legs, you're likely not gonna be able to see above 1m tall grass.

  • thermoregulation. Your limbs constitute a meaningful part of your body's surface area, and also plays an important role in dissipating heat. If you can't keep yourself cool through other methods, you might be at a risk. Cases where people have no limbs whatsoever they need to change clothes regularly to avoid problems like overheating.

  • proper ability to use nearly every single bit of technology today. Things are normally made with your average human in mind, meaning that you're naturally at a disadvantage if you have no hands...or arms... Or legs. You'd need to essentially adapt most pieces of technology to the new human body, or what's left of it.

  • competence in zero Gravity movement. In the ISS the predominant method of movement is to basically use your limbs to swing/push/pull your way around the station and outside of it in case of things such as repairs. Your bean humans will have to hope they can bump their heads or waists in the right way just to go from a wall to the next, and won't be nearly as dexterous at it. External repairs would likely require machines, since they'd have basically no way to cling to the station without any limbs.

Overall, it'd be a pretty bad idea. It limits their competence at moving around, limits their ability to function properly in a warm environment and limits their ability to use technology quickly and efficiently, or to do many tasks that require, well, limbs to be made, such as clinging to the hull of a station while doing repairs in the vacuum of space where your mouth and nose are within the confines of a helmet and thus have little to no capacity to be used to hold anything. It's just a bad things overall. Sure, they'll survive, because we can survive without limbs, but we can also survive as tetraplegics, because we have people that aren't in the same boat to help us with the problems that come from such conditions.

If you want humans adapted to possibly be compact and you have a high enough technology for the necessary changes here's what you do:

1- let them be born normally as any human would.

2- let them live normally until they're around 25 years old, at which point their brain and body will be fully developed.

3- surgically extract their organs, brain and spinal cord, and put those in a specialized mechanical body that's stronger, more agile and much more capable at keeping said brain and organs healthy and protected on earth, in space and potentially even in other planets.

4-put them into a rehabilitation center so they can get used to their new, mostly mechanical superbodies.

Basically you turn this: enter image description here

Into this:

enter image description here

And from there it's a breeze. Need them to be a little more compacted? Disassemble their limbs and non-essential parts of their bodies and store them elsewhere. Need them to perform a specialized function where extra limbs would be helpful? Strap in an extra limb, or 2,or 4. Need them to work in outer space? Rather than an entire suit, just attach the specialized life support systems directly to their bodies. Add some thrusters to their legs and arms while you're at it to ensure they can travel freely in space without worrying about being bound by safety cords or being trapped forever in space if they accidentally loose their grip and end in open space with nothing to hold onto. For all intents and purposes they should have all that's needed to cling to and navigate the outer stations properly and efficiently. Most important bonus: you can't have a nose itch while in outer space if you Don't have an organic nose with nerve ends on it.

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  • $\begingroup$ Limbs dissipate a reasonable amount of heat, sure, but they're also responsible for generating a big chunk of said heat. $\endgroup$ Jan 18, 2022 at 18:02
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    $\begingroup$ phantom itch is a thing ... and now most of the standard treatments won't work ... $\endgroup$
    – Harthag
    Jan 19, 2022 at 16:38
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Q: "These humans would be genetically engineered, and so could have some sort of simple adaptations to make up for the lack of limbs. For the sake of lightness, they are around 30cm tall, with smaller organs and very little fat. Could these humans thrive without arms or legs?"

Not a good plan to let the infant be born without limbs

At birth, you don't know if a child will become an astronaut. In your world, people would be predestined to become astronauts ? Are they born in space ?

I see a few biological hurdles that have to do with the brain and the connections needed for artificial limbs and balance. A genetic change involving the brain would be complicated. In the case limbs are present, your brain develops during life, to handle two legs and arms. By applying genetic changes only to remove the limbs, the infant will never need to learn any concept of "having limbs", from the moment it is born.

Nothing is prewired, you "put limbs on". For brain-controlled devices (nicely illustrated above), you'd need neural pathways to connect to. You don't walk and fight comfortly with a joystick. But the genetically altered child was born without neural pathways to control a pair of legs. There is no connect for limbs motoric control in the brain, there may be no balance system feedback, probably the balance system won't develop altogether.

Amputate the limbs only when neccesary, and ask for permission first

Forget genetics. Let a human be born with arms and legs. Let it develop. Then you could mount the human onto something bigger, and stronger, keeping the arms and legs in, preferably (e.g. Earth applications, great strength etc) or.. you amputate the limbs (voluntarily) to prepare for space travel. In that case you choose for that, as an adult. Great advantage: you now have a person with trained legs.. and all you need to do, is plug in your exoskeleton limbs to already developed neural pathways. It will require far less training than a limb-less person needs.

Probably, only astronauts would be this mad

Space travel will be a strong incentive, to undergo the procedure. It will have to be researched, though.. Some day, the astronaut will return on the home planet, in gravity circumstances, the astronaut would need good technology. In Earth culture, the astronaut will want to look attractive, requiring android limbs of good quality.

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I think this query is predicated on the assumption that a human's arms and legs represent a significant source of mass that needs to be eliminated during spaceflight. Think about how massive even our modern ground-to-orbit vehicles are. They are far more massive than the combined body mass of their human crews. Now think about the space shuttles, which mass well over 800 thousand kilograms, not even accounting for their fuel and booster stages used to enter orbit.

Now, we haven't even mentioned that the game rather changes once you are no longer in a gravity well. In microgravity, getting around actually becomes a lot easier, or at least a lot less energy intensive. The mass of the craft and its contents essentially equates to fuel cost; the more massive the vessel, the more energy is needed to accelerate it the same amount. The mass limitations on what modern astronauts can bring with them on flights is mainly a result of our primitive spaceflight technology, and the fact that we have basically no industry in orbit and must manufacture everything planetside (people included), and ergo must shove it up out of a fairly steep gravity well by brute force. There are far more efficient ways of getting resources into space (constructs and people alike), including just creating them there in the first place.

Anyway, this has been a verbose way of saying that people's arms and legs are not something I can see future astronauts worrying about the mass of, especially as technology advances, as I assume it has in your story. If someone wants to bring along, let's say, their small collection of android hard drives on a space mission, I see no reason why they should not be allowed to. If someone wants to bring along their arms and legs that they were born with and are a vital part of their physical being, you had best let them.

Now, I don't know what kind of world you are building in which space captains are thinking about cutting off people's arms and legs to save on mass, or even just breeding a race of humans with only torsos and heads, but if you really are that impressively stingy about mass, then there are better ways to eliminate it. A human's arms and legs just aren't that high a percentage of their body mass, especially for obese people. The torso is the most massive part of the body. If you're so determined to eliminate flesh mass, you might as well just decapitate everyone and put their heads on advanced life support apparatus, or even just rip out their brains and put them in life support tanks. And who says they need to be conscious during flight? You could do away with the bulky life support systems and just freeze the heads or brains until they reach their destination, where they can be given new bodies, if our medical tech is at that level. In fact, while we're talking about ripping people's brains out, you might consider just scanning their brains instead and emulating them aboard a computer server. Virtual humans take up virtually no mass, and can be duplicated or backed up any number of times. The humans who had their brains scanned might as well just go on living their ordinary human lives back on Earth (or whatever planet you are setting this on or at) while their computer-emulated replicants are out crewing a spaceship.

And that's even assuming the ship needs a crew, since if you're going this rout, which I'm not saying you should, the ship could very well just be a single machine intelligence, human-based or not, and depending on its purpose, could be as small as that car that Elon sent onto a Mars-intercept trajectory, or even smaller. It could even be a single intelligence controlling a swarm of bug-sized machines sent establish a base on an asteroid or something.

So, sorry if I got a little carried away, but the short of it is that if you are trying to eliminate extravagances, such as people having limbs, where do you stop? In a way, our organic human bodies are extravagances, inefficient contraptions given us by nature's trial and error, but it is nonetheless easy to see our spacefaring descendants spending that truly tiny amount of extra energy to bring their organic bodies along with them.

And that's the other thing. I don't know what kind of energy economy the people in your story possess. Being so stingy about mass to the comical degrees discussed here, and to have such arguments be even slightly justifiable, they would need to be at or around the same technological level that we are now, or lower. Advanced spacefaring civilizations will surely have far greater access to energy than us primitives. Space travelers of the future might be within their rights to bring their whole organic body along with their shipping-crate full of lead ingots and their granite mansion on a space voyage, because people just don't care. The extra energy needed to accelerate the additional mass just isn't significant enough to even put a dent in the ship's fuel readout. Especially if the society in your story has access to something like antimatter propulsion, or goodness-forbid black-hole engines. And lets not even talk about how you might not even have to carry your fuel with you during flight, but could instead use various remote-propulsion techniques such as light sails pushed by lasers.

Basically, there is no point in creating the bean humans. It may be possible to function normally without limbs in a technologically advanced society in which you can have robot limbs or just live permanently in VR, but lacking limbs confers no advantages, and the proactive work needed to surgically remove preexisting limbs that the person will be literally and emotionally attached to, or the even greater feat of genetic engineering needed to create humans born without limbs seems like an effective barrier to having a limbless humanity.

Safe travels, fellow builder.

sources: https://www.nasa.gov/pdf/516059main_ALG_ST_SSA-Mass%2012-15-10.pdf)

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Why Not?

Given advanced technology, I would ask why humans with fleshy limbs would fare better than ones who are given access to mechanical ones from birth, with easy replacement parts and a wide variety of body plans to choose from. Given sufficiently advanced and reliable equipment, moving human pods about in a hostile environment is much safer than trying to convey entire full-size humans, vastly less resource-intense, and gives much more leeway to create a body plan as simple and reliable as possible to protect the most important thing - the brain - as much as possible. EMP sufficient to disable advanced tech on a spaceship or alien planet will be equally lethal to a normal human as to a "reduced" human.

CYBERMEN: A sufficiently advanced society venturing out into space, new worlds or failing old ones will need to be able to rapidly adapt to new environmental conditions. The simplest way is to have the essence of the person in a small, transferrable (and preferably G-force and shock resistant) body. Direct neural interface enables seamless connection to new equipment, and all the team can be kept as safe as possible wherever they are.

DALEKS: If you really think small limbs are of some benefit, you could have tiny limbs or tentacles, I suppose. Perhaps there are some ineffable qualities of humans that require organic interfaces to the brain to preserve the nature of what it is to be human. Such a tiny person would have some minor functionality, but it wouldn't have to look at all like a human, and such limbs would really only be desirable if electronic interfaces and equipment were unreliable.

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Your humans are modular

An ordinary human is made up of cells. These humans can move and rearrange their cells. The ordinary networks of actin and motor proteins that allow cells to move in the human body have been redesigned to allow directed motion from one cellular address to another. A complex set of microscopic transmission links allows them to navigate the way. Every extracellular matrix protein in the body has been designed to zip and unzip almost instantly.

Your humans may be called "amoeboid" by the ignorant, but they are not simple blobs of flesh. They are capable of coalescing to a nice round blob form while riding in a space vehicle, or generating myriad pseudopods each with fine dextrous control, or even duplicating a small human with arms and legs for artistic reasons. Their coordination and motor cognition is immeasurably superior to that of their ancient forebears.

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I have a hard time seeing a benefit in removing everyone's arms and legs genetically just to save energy for space travel. Even if the species lived only on space ships, they would still face "gravity" whenever they accelerate. Unless they live in space ships that mostly float around instead of traveling somewhere, legs would be useful to keep oneself mobile. And arms tend to be useful to touch stuff like buttons or move food into one's mouth.

The technology that would be required to make not having arms and legs as a species a minor issue would be incredible advanced, reliable and available for everyone. With such technology around, why not simply remove all biological matter and live in a space and energy efficient computer simulation?

Without such almost magic technology, reducing the body size seems the better way. Arms and legs (only) make up about 20% of a human's weight. My quick (and quite possibly wrong) calculation suggest, reducing their height by about 10% also saves around 20% weight. But lets not nitpick, let's just assume the choice is between removing their arms and legs versus reducing their size by half. Doesn't sound hard to choose, I think.

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  • $\begingroup$ The spacefaring future belongs to malaysian women ;-) $\endgroup$ Jan 18, 2022 at 18:03
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Who needs organic limbs at all?

Once you have really efficient life support systems and cybernetic interfacing, why on Earth (or why on any planet) would you want to be limited to the one original set of feeble, damageable, mortal meat-on-bone appendages?

Rather just wear whatever body suits your needs at the moment. Whether that is a fully organic human body made to order,
or a cybernetic body that can go where no human can possibly go (fancy doing the backstroke in a lava lake?)

or how about making your body a nice, shiny, superluminal spaceship, with all the accessories? I've always dreamed of exploring the galaxy like Helva (XH-834), a woman locked into a cyborg shell in infancy to become the 'Brain' of a starship, the ship who sang.
enter image description here

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  • $\begingroup$ "why on Earth (or why on any planet) would you want to be limited to the one original set" why ? well people prefer not to loose their original set in the first place. You're born with them, you are attached to them. I certainly hope all procedures mensioned here are voluntary.. $\endgroup$
    – Goodies
    Jan 18, 2022 at 19:15
  • $\begingroup$ @Goodies you wear shoes all the time, right? Lost the ability to grip with your toes, I bet? Why did you choose to remove the functionality of your toes? Same thing. When the replacement is actually better than the original (as shoes beat well-callused and agile toes), you do not miss the function of the originals. $\endgroup$
    – PcMan
    Jan 18, 2022 at 19:26
  • $\begingroup$ Shoes didn't kill our toes. Imagine you'd go walk upright (bipedal humanoid) keeping your tree-branch gripping toes.. Too much energy cost. People with shorter toes will survive. Guess people were adjusted (by nature) at some point in evolution. to have shorter toes. I found a nice piece about the mechanics and balance involved, it is a quite advanced system.. ncbi.nlm.nih.gov/pmc/articles/PMC1571307 $\endgroup$
    – Goodies
    Jan 18, 2022 at 20:41
  • $\begingroup$ @Goodies hunybun, get your facts straight. If you grow up and never wear shoes, your toes are much more widely splayed, stronger, and immensely more flexible. I've seen a KoiSan bushman roll a homemade cigarette with his feet. Not to show off, it was just more convenient as his hands were holding a calabash of beer at the time. It's NOT an evolutionary thing, it is a direct accommodation to an imposed environmental condition. People chose to wear shoes (because they protect the feet so much better), and in the process are quite happy to throw away a lot of the functionality of those limbs! $\endgroup$
    – PcMan
    Jan 19, 2022 at 8:49
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Yeah they would still need arms and legs because even in a microgravity environment people would still need to move objects and manage food and hygiene around. How could they do it without limbs?

And artifitial gravity could make genetic modifications into a bizarre appearance or the creation of a bizarre race of people unnecessary.

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Survey the limbless people to find the truth

All these questions, answers and comments are made by people who have all their limbs intact. You should make a survey and ask those people who have lost their limbs. They will tell you what kind of hell they are going through.

Also survey those people who have artificial limbs and ask them

  • How happy and easy they are feeling with artificial limbs compared to original limbs?
  • Are they feeling pains in different seasons?
  • Will they recommend that other humans also get artificial limbs?

Limbs are not for movement only

Real limbs are parts of body with sensors gathering information for further processing.

Sensitivity

Artificial limbs do not have sensitivity as the original limbs. You will loose a lot of information which could be harmful in certain situations.

Pleasure

You touch something nice (run your imagination) with real limb and artificial limb. Can you get similar pleasure?

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