In the last few decades there has been a lot of progress in the development of prosthetic limbs. They can be operated by the user's nerve pulses, they can be fitted with simple touch sensors, and can be constructed from materials that are both lighter and stronger than their original limbs. I've also heard that some of the newer experimental ones can even be operated by implants inserted into the movement center of the brain. Meaning that the limbs respond to the 'intent' behind the motion and not just the user's nerve endings.

This gave me an idea for a short story about a woman who volunteers to be used as a testbed for cybernetic enhancements. Realistically, how much of the human body could be replaced by cybernetics and still be able to function, using only current technology?

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    $\begingroup$ Depends on your definition of "able to function". Do you mean "live as well as without it", or rather "somehow go thorough the day and only need help once a day, then die in ten years"? $\endgroup$ – Mołot Aug 25 '16 at 6:19
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    $\begingroup$ I found a site a while ago where they were working on a lot of replacements for human parts. I couldn't find the link again with a 5 min google but this is similar : Artificial spine $\endgroup$ – Sarfaraaz Aug 25 '16 at 10:38
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    $\begingroup$ "materials that are both lighter and stronger" doesn't mean they are better than biological ones - weight and toughness aren't the primary quality criteria for human organs $\endgroup$ – enkryptor Aug 25 '16 at 12:23
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    $\begingroup$ Lets think about where we draw the line between a human with cybernetics and a robot controlled by a human brain. If you don't need the stomach, intestines, lungs, & heart to supply oxygen and nutrient rich blood to the head, all that is left is being able to decode the electronic spinal transmissions. $\endgroup$ – Jammin4CO Aug 25 '16 at 14:59
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    $\begingroup$ Based on @CandiedOrange's answer, this would probably seem like a great idea, but turn into a really depressing story. I would totally read that book! $\endgroup$ – IQAndreas Aug 25 '16 at 20:29

This is one of those things that sounds cool until you think about it.

If our goal is to get as much of her body converted over as possible this is just going to be sad.

She now has prosthetic arms and legs. They work but they are poor substitutes for the real thing. Amputees actually have to have multiple prosthetics for different uses.

We can replace her heart and kidneys. It will shorten her lifespan but we can do it. We can replace her ears with cochlear implants. We can replace her eyes by wiring cameras into her brain that will let her see a few pixels. We can even shave her bald and put a wig on her.

All these things would be a crime to do to a healthy person, for good reason.

Not that there aren't fun cybernetic toys. That chip you put in your dog can also go in your wrist. With the right keyboard you never have to type a password into your computer again.

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    $\begingroup$ I don't know man. You shouldn't underestimate the value of a colorful wig with LED lighting. Think of the possibilities! $\endgroup$ – William Mariager Aug 25 '16 at 10:05
  • $\begingroup$ There exist people who volunteer to do sad stuff and not only cool stuff, so I don't see how that's an issue. $\endgroup$ – JiK Aug 25 '16 at 10:09
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    $\begingroup$ Small-sized autonomous artificial heart and kidneys aren't possible with modern technology, are they? $\endgroup$ – enkryptor Aug 25 '16 at 10:53
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    $\begingroup$ @enkryptor: I suppose it depends what you mean by "small" and "autonomous". With hearts the pump can be small enough to implant but the problem is powering it. Does someone with an artificial heart and four prosthetic limbs really want to also have to carry a heavy battery pack around with them? That's a huge physical effort, so clearly not, but they're alive and can move so it's a question of whether or not the prosthetic is better than the alternative. For a healthy volunteer it's certainly worse. $\endgroup$ – Steve Jessop Aug 25 '16 at 12:12
  • $\begingroup$ @enkryptor I didn't hear "Small-sized" or "autonomous" I heard "how much of the human body could be replaced by cybernetics and still be able to function, using only current technology". Which is likely why this ends up sad. Personally, I think cochlear implants could be sexy. $\endgroup$ – candied_orange Aug 25 '16 at 12:29

Let's say you want to limit yourself to current technologies, and fully cyber, so not grown from stem cells, cloning, or other 100%-bio components. Similarly no support devices (e.g. pacemakers) as the core organ is still biologic.

It has to be cyber. Meaning, a piece of wood instead of a leg does not count.

Furthermore, we want that the patient be freely to move around. She does not have to have a normal life (won't have, at the moment), but she should have to be limited to living lying on a bed in a hospital.

With those constraints in mind, we have currently:

  • limbs. Those are the easiest. The Wikipedia's Artificial Limbs shows some details. But essentially, and to various degrees, full arms, hands, legs and feet could be replaced. Some more elaborate versions are still under tests, but the technology is there. Do note, that one of the limitation of those, to date, is a rather heavy weight. So your woman has to have the strength and rest of the body to more around those four limbs.
  • heart To my knowledge, the only device respecting the conditions above is the one from the French company, Carmat which implemented cyber-hearts on people, and those were able to leave the hospital, without any external devices. But do note that those are still rather bulky, and as such are only suited for people with a certain... weight. Also note that to date, the longest surviving test lived for 9 months after the transplant. But most of them were on the 65+ years old.
  • ears, using Cochlear implants,
  • eyes. There a re a few versions of it, but one could use bionic eyes.
  • bones. Some bones can be replaced by prosthesis. See, e.g. for the hip.

Additionally, there is some work on-going about different parts of the body, like kidneys, lungs, livers, etc.

Many of the current attempts are focused on biological elements grown artificially. And as such those are discarded by our earlier assumption.

Do also note, that so many changes would incur such an emotional stress, that your patient will likely go nuts from it. Or maybe be simply exhausted.

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    $\begingroup$ so many changes would incur such an empotional(sic) stress, that your patient will likely go nuts from it adding up all that essence cost... $\endgroup$ – Mindwin Aug 25 '16 at 14:28
  • $\begingroup$ tvtropes.org/pmwiki/pmwiki.php/Main/CyberneticsEatYourSoul $\endgroup$ – ApproachingDarknessFish Aug 25 '16 at 23:28
  • $\begingroup$ Please, provide a link, where did you find this information "the longest surviving test (with cyber-hearts) lived for 9 months after the transplant"? $\endgroup$ – Ivan Gerasimenko Aug 26 '16 at 8:21
  • $\begingroup$ @IvanGerasimenko sorry, I couldn't answer before. But on that section, I provided a link to the wikipedia page of the company, where I got that info. Unfortunately, that's in French. $\endgroup$ – clem steredenn Sep 5 '16 at 18:20

As early as the 1500s(edit: Can't find reference for this. Early 1900s video shows it though. Discussion here about video and head removal.) there were experiments of transplanting heads onto other bodies which were short term successful for what they were. Given the advances of medical science it is probable that you could transfer a head (and neck) of someone to a cybernetic body and be fine, but those experiments were stopped due to the ethics of the matter, even while doing it with animals. Also limiting this to the head makes it easier because the hardest problem that we have today that i know of is cleaning the blood which is mainly caused by other organs and nothing in your head.

A few years ago there were experiments of attaching and integrating animal brain cells to robots which if I remember right was extremely successful, but it was a short term experiment so not sure the life span on that.

So yeah, everything but head(and neck) things and even that's coming along...

The main issues that cybernetics face are different aspects of the same problem and that is incoming data and sensing things. Incoming data is simple to explain, we're making strides, but according to what I've heard it's a matter of trying to speak to someone who can only hear in English, but can speak any language, and we can only speak in Japanese. The strides are crude at best in my opinion, but life changing according to the people who have received the implants. The maximum capabilities is akin to a giant black board with light bulbs and the sensor implant can detect light and dark and light a bulb up in your brain so that you can "see" light/dark and that's your "sight". I recently came across an article that seemed to be saying that they're now able to make people see crude topographical renders, but I didn't read it. I just got that from the headline and image.

The other problem is "sensing" and that is basically when we say "touch" we're actually describing several senses such as pressure, heat, smoothness, etc. I'm not sure we can faithfully replicate many of those let alone all in one full body suit. For some this wouldn't be so bad, and if you had to take this option or die, when push came to shove they'd take this option, but ultimately without touch sensitivity you will have to learn to judge everything by sight and hearing which is very dangerous, but there is also the fact that if we can't master this, even if we can master every other aspect, it would not be a viable option as it would likely have a high probability of the person going nuts from sensory deprevation of some sort.

Side note: The technology to plug yourself into a computer exists. It just takes a while for your brain to learn how to control the computer and this is determined by your brain plasticity, so someone old might not be able to partake in this technology if they haven't already trained on it. Again, the main problem though is input into the brain rather than output. If we could work out input to a higher degree I imagine true VR would be incredibly easy (although with some major dangers).

I expect that full body cybernetic technology will be available in 10-20 years, or rather prosthesis cybernetics. For non-necessary medical uses I'd expect it to be available in 40 to 50 years and widely used by all people within 60 to 80.

  • $\begingroup$ "As early as the 1500s " - do you mean 1950, don't you? $\endgroup$ – enkryptor Aug 25 '16 at 12:24
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    $\begingroup$ "full body cybernetic technology will be available in 10-20 years" - we are still decades from a decent nanotechnology comparable with a simple cell, how can we expect the full body replacement in 20 years? $\endgroup$ – enkryptor Aug 25 '16 at 12:28
  • $\begingroup$ @enkryptor The earliest of these experiments that I can think of is DesCartes who successfully kept a dog's head alive with a machine for a short time. He was doing this in the 1500s. When I say "available" I mean it will exist. We've had the tech to plug ourselves directly into computers for the last decade, but it's not commercially available yet. You have to understand that what is 'available' and what is 'commercial or ethical' are different. We made huge leaps with Nazi science because they put aside ethics, likewise a crazy evil scientist could likely use current tech to do Robocop 2day $\endgroup$ – Durakken Aug 25 '16 at 14:39
  • $\begingroup$ Just being curious, I know about Descartes vivisecting dogs, but I'm not aware of any machines he used to keep them alive. Could you give a link for a further reading? $\endgroup$ – enkryptor Aug 25 '16 at 14:45
  • $\begingroup$ I might be misremember things, but I remember it being attributed to DesCartes, but I can't find it... These experiments I know Frankenstein is largely based on them getting out of hand. Instead I did find something similar to how I remember it being shown that DesCartes did... The dog head in this video youtube.com/watch?v=KDqh-r8TQgs $\endgroup$ – Durakken Aug 25 '16 at 15:00

Not much.

If you don't want to replace the body part with something significantly worse, then nothing, maybe except the teeth and the lens in the eye. And none of these are moveable or have any need for electronics, so they would not really be truly "cybernetic".

Even with teeth, modern implantology barely got to the level to make dental implants which last for a considerable amount of time and have a fairly low rejection rate, but rejection rate is still a thing and they only guarantee 10 years, even if it might last somewhat longer. The bone will slowly but gradually degrade around the implant, so a healthy natural tooth still has advantages over dental implants. And remember, it doesn't need any moving parts or any power supply, but we still only can do so much, using the best available technology.

About the rest of your body?

  • Although functional, motor-driven prosthetic limbs do exist, they are less agile than normal limbs.

  • Although artificial organs, like heart, lungs, kidneys etc. do exist, they are bulky, less efficient, and require constant medication for the rest of your life to prevent infection and prevent your body from rejecting them.


A full body prosthetic (i.e. a remote controlled robot) would probably be the most practical way to go, with the brain being kept at some sort of medical facility. Then it doesn't matter how bulky the life support machinery is or how much electricity it needs, and the robot isn't burdened with the weight of a brain and life support system.

No one really knows how long a brain can be kept alive on life support, there's a lot of engineering challenges and we don't understand the brain's needs well enough to support them entirely & properly.

As for the brain-machine interface there's a lot of work being done on that right now, worst case scenario you're a head in a jar with a screen, headphone and eye-tracking technology, it would be a terrible interface but it would work.

A few decades from now things are going to be interesting.

  • $\begingroup$ The question asked about today's technology. $\endgroup$ – vsz Aug 26 '16 at 6:12

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