# Background

This is a sci-fi setting. People there have advanced biotechnologies, being able to edit the genetic code of embryos (governmentally enforced to be strictly regulated and only for medical purposes as like curing some genetic disease), and a range of tech that allows them to grow organs in a vat (Mainly used for artificial meat production).

# My question is:

While the technology allows for growing limbs and organs to replace those that were lost due to accidents, why do many in the setting still prefer to fix themselves with cybernetic augmentations rather than grow a new leg in a vat?

Those cyber limbs are not of a Hollywood variety, and while can be better than their organic counterparts, require some maintenance and do not grant superhero abilities. No, you can't punch through a concrete wall or lift a car with one, but you can have fingers that have micron-level precision and can bend backward, for example.

• you answered your own question mechanical limbs can do things biological ones cannot, full rotary motion is just one example
– John
Dec 16, 2021 at 0:43
• “There is no truth in flesh, only betrayal. There is no strength in flesh, only weakness. There is no constancy in flesh, only decay. There is no certainty in flesh but death.” Dec 17, 2021 at 3:31
• Aesthetics? That'd be my reason anyway. Dec 17, 2021 at 4:14
• Because steel?. Dec 17, 2021 at 11:40
• Biotechnology gets tired. Dec 17, 2021 at 14:45

The answer is there in the question: Micron-level precision of fingertips isn't something you get from meat.

Biologics have a superior user experience/look & feel. There are likely some things that will never be replaced with hardware. But hardware has a number of advantages over squishware:

1. Consistency - Biologics are notoriously dynamic things (evolution only works because of this). While they're able to actively maintain themselves, they're also notoriously susceptible to environmental conditions, infectious agents, and other threat vectors that you can't ever truly escape as long as you're building with meat. Hardware has to worry about corrosion and erosion... and that's basically it. Sure, I could get my arm replaced with meat, but odds are I'd end up needing to do that more than once. If I don't care about the aesthetics, maybe I just want a piece of polymer with some carbon-fiber 'bones' to it so I can set it and forget it? That micron-level precision sounds great if I'm an artist designing sculptures at the microscopic level. When we're able to replace virtually anything with either meat or machine, then the body becomes a tool and we upgrade it according to the demands of use.

2. Aesthetics - Maybe I do care about how it looks? Maybe I've got ideological problems with foreign meat being attached to my meat? Maybe I think everyone who's using biologics "because it feels natural" is kidding themselves and I want to be punk about it? Maybe I grew up idolizing Darth Vader?

3. There are a few places where machines simply are superior to meat, most of them involve hazardous environments or dangerous jobs.

4. Finally, it's entirely possible that artificial organs and limbs have to be specifically tailored to my body/genetics. That could be expensive, whereas mechanicals are basically an off-the-shelf solution. There's PLENTY of room for juicy classism there.

• While it's not a mundane level of dexterity, non-mechanically aided micrometer precision is achievable by (some) actual humans. I offer you 249 character written on a strand of human hair - the typical thickness of a human hair is 70 microns. Dec 16, 2021 at 1:15
• Maybe I grew up idolizing Darth Vader - i don't get it.. are you saying there are people that didn't do that? Dec 16, 2021 at 11:50

My own take is based mainly on adding plausible issues to the bio-side of the equation:

## Growth time

You can't just assemble a new complex organ or limb that has all the blood vessels, ligaments, bones, and muscles in it. Those things require being grown naturally, and you can't rush that process too much, so a new limb can take up to several years to become fully mature for transplantation. Cyberlimb can be installed on the same week the accident happened.

## Accidents during production

The growing process is long and can have a number of accidents that ruin it (it spontaneously gets a cancer tumor, slight hiccup of the supply of the nutrients or error in genetics causes it to grow deformed, an infection finds its way into the vat, etc), in which case you have no choice but to scrap it and begin from a single cell again.

## Immune system response

The body's immune system can still reject the new limb, because it was grown from a tampered DNA that was changed for it to grow to adult size in a couple of years instead of a couple of decades.

## Rehabilitation process

Regaining control of your new limb requires lengthy rehab that can span anything from months to years, just like it does in real life, and might never become fully complete. Cyberaugs, in contrast, are controlled via a self-learning brain-interface implant, that takes only several weeks to adapt to the neural patterns of the user, and after that can function with any cyberlimb model that has compatible control I\O protocols.

• This also opens up the possibility of temporary cybernetics: While your new hand is growing in a vat somewhere, why not at lease enjoy having some sort of hand in the form of a robotic one. And maybe by the time your organic replacement has grown they got so used to the additional features / the feel etc. of the robotic one that they refuse the transplant Dec 16, 2021 at 14:47

## Mechanical is simply better

Biology is in many ways incredibly efficient and perfect. Yet there are limitations on what you can do in structural or muscle strength. In contrast, any mechanical part can have far better limits, be purpose build, have more features and can potentially be replaced in a very short while.

Now the question is, why not? We see that in our daily lives efficiency is only so so important for us. Many examples can be shown, like lots of the personal transport business, where we definitely aren't efficient. So if you offer someone a mechanical upgrade that is stronger and better in every way, but power hungry. Will they say yes? If power is abundant, why not?

And again, you have a ton of potential options. As an (unlikely) example, a smith with fireproof hands might have the power together with the feel to incredibly accurately finish some details on a red hot glowing piece of metal. Integrated plasma torches, a light, different optical usages on a whim and so much more. With genetics, a little imagination and some sci-fi you can go a long way, but never as far or as quickly as with mechanical upgrades.

Besides, if you need to wait a month before you have your arm back or have it immediately (with possibly a month of revalidation ironically) many would choose instant gratification.

• Mechanical parts also get the possibility of software upgrades and future improvement. Biological parts will at best stay the same over their lifetime, but mechanical ones can be upgraded over time. You see this in real life with things like cochlear implants - as most people with biological ears age, their hearing gets worse, but people with electronic "ears" can have their hearing get better as they age due to improvements in signal processing software over time. Dec 15, 2021 at 22:23

Why not be both?

The flesh is weak, but steel is cold. Biological material is susceptible to many environmental conditions that robotics are not. It takes time to develop, to grow and heal. Robotics is strong, resilient, reliable and can be repaired quickly. However, biological components have certain properties that would be beneficial, such as the ability to have sensation and the ability to communicate with the brain.

You can have a full robotic body, but it may be beneficial to have biotech/mechanical interface components to allow control over the body. biological components are also harder to hack than a artificial system.

You can also have synthetic biologics, basically biotech growing mechanical components that simulate how the body works, such as synthetic muscles or circulatory system. You could substitute more robust materials in place of natural, such as silicone coolant/hydraulic (blood vessels) and nano-fiber actuators (muscle tissue). Cybernetics could also give sensory advantages that just does not occur in nature, such as telescopic vision in multiple wavelengths, audio magnification and detection of energy such as radiowaves.

Biology has created perfect systems. Robotics can make such systems beyond perfect.

No time

The best artificial limb is yours, biologically your genes. It should just grow back, to fit you.

But the inhabitants of your planet have busy jobs, they don't have time to wait for slow biology. The growing needs medication, takes months.. they just buy a metal limb that fits, works and looks good.

Avoid medical procedures

Many people prefer contact lenses instead of a laser operation: you may choose to get your eye lasered in a hospital, or you can just order a box of 50 lenses online and put in a new lens (a prosthetic) in the morning.

Same with good quality metal prosthetics on your planet: some will have the money to buy a metal prosthetic for a few months and meanwhile grow their bio-replacement limb in a reactor. This technology can breed a perfect prosthetic limb, in due time. But the result would have to be stitched, using classical medical procedures. Also, intense revalidation procedures are needed. On your planet, engineering and smart sensor control is preferred over complications and therapy !

# Competition:

Your Futurians live in a world where there are lots of pressures to live in new environments. The same laws preventing bio-enhancement also forbid the governments of the world to use mandatory birth control. Because of cheap biological parts, no one dies, no one is infertile, and custom-made organisms and machines do all the work people do. The population grows and grows, while opportunities to advance shrink and shrink. 95% of the world's population is on the dole.

Biological bodies are also poorly interfaced with machinery and virtual environments. To get a really convincing virtual experience, you need microchips implanted in your skull/brain/sensory tissues so you can experience convincing virtual realty. Trust me, with population pressures and overcrowding, you WANT to escape reality. And the jacked up have a competitive advantage over those who aren't.

Maintaining a full-scale biological body in the deep ocean or deep space is resource-intensive. But machine parts are able to tolerate high or low pressures and temperatures. So if you aren't fantastically rich, if you want to live in something better than a tin can in an overpopulated city, it's time to get the cyborg conversion.

Sure, you are basically a brain with life support in a can. But if you want kids, those parts are kept in a storage facility. And companies WANT people who can swap limbs, interface with space shuttles, or go out in mini-subs the size of a normal human, because they are basically a dedicated cyborg body. The company gives you a chance to get ahead, and if you get rich enough, you can simply grow a new biological body and retire to someplace nice.

As I'm surprised that no-one has mentioned either of these as main factors yet:

## Cost

Growing things in vats takes time and costs money. Detailed surgical procedures to attach new limbs and organs correctly requires money. Even once things are attached, you will need regular check ups from a skilled doctor and probably physio-therapy as well for appendages which again costs money. Spending all this time doing that will make a dent in your regular work pattern i.e. indirectly costing you money again. Any slip-ups in the procedure may cause you to have to go back to the start of the process and try again.

For prosthetics, they need little, if any, customisation, roll off a factory production line so can be purchased "off the shelf" and are essentially plug and pray. Yes, you might need a doctor of some kind to hook you up but once that's done, the rest is just an occasional lube and re-charge/refuel.

## Regulation

governmentally enforced to be strictly regulated and only for medical purposes as like curing some genetic disease

Although the question states that is for embryo editing, let's think realistically. If I want a new organic arm, do I want the same one as I had before or do I want one that is genetically tweaked to build more muscle mass? How about one that's less hairy or a slightly different skin tone? Maybe I fancy an extra finger? Perhaps an extra joint? Maybe two arms linked to the same shoulder joint? Finger-tips that glow in the dark?

Bear in mind that people have the ability to grow meat in a vat. It's quite possible that people have such a vat in their homes, so they can harvest meat at their convenience, much like people grow their own herbs or vegetables today. By having this technology available in the home, it won't be too long before some bright spark realises that with a little reprogramming, you can use a home meat vat to create other items by changing the DNA seeding.

As soon as people start to get creative, what began as a little vanity for some and a bit of practicality for others will soon be abused before too long and that will result in government regulations as well.

Initially a little regulation to ensure basic safety is a good idea but once people start using non-regulated parts to get around this, the level of regulation will become increasingly heavy-handed. Imagine that the trade in non-regulated parts gets so bad that the regulations state any replacement body parts have to be an absolute minimum of 99.8% identical to the part it replaced and your genetic code. Failure to comply results in the replacement part being removed on the spot without anesthetic, a lifelong ban on organic parts and a hefty fine.

Given that organic body parts can age and deteriorate, this would soon render the replacement body part market an extreme luxury as finding production facilities good enough to ensure regulation compliance for the expected lifespan of the replacement body part will become increasingly challenging and you will have to pay accordingly.

Prosthetics, on the other hand, are simpler to regulate as they can only be produced by licensed factories. The power source/actuator/processor/neural connector from prosthetics gives off a signature that is really easy to trace and any third party tampering will change the signature from the factory one.

## Conclusion

Essentially, it's cheaper, faster and less risky to get kitted out with prosthetics, so that's where the money goes. Once portable body scanners start to be issued to undercover police agents as part of the crack-down on non-regulated organic body parts, the above becomes even more true and everybody who gets caught out once will be on prosthetics for life.

In a country with free vaccines, why do so many people choose not to get vaccines and perpetuate a global pandemic?

In a country with a readily available supply of insulin to manage diabetes, why do so many people ration insulin, or die from lack of insulin?

In a country with billions of pounds of food wasted every year, why do so many people starve to death?

In a world with genetically modified crops that produce 10x the yield, why do countries reject those crops and allow their people to starve trying to grow "traditional" crops?

As you can see, people and societies do not always (do not often?) behave in rational ways.

People do not have the means to access certain resources because those more greedy and powerful than them decided to hoard and/or destroy those resources for their own gain.

People live in societies awash with propaganda.

People are prejudiced against technologies that they don't understand, making them even more susceptible to propaganda against those technologies.

The real question is not, "Why do people use mechanical prosthetics when bio-replacements are available?" The question is, "What rich segment of society benefits from most people using mechanical prosthetics instead of bio-replacements, and how are they using propaganda to exploit the masses?"

# Rejection of new limbs.

New organs often have some rejection issues, because they have minor differences from the original organs. This requires a geneticist to work on them and fix them, or reclone the limb.

It's certainly doable, and in the short run it's fine, but it's not an easy or a quick process. This drives the price up, and the time to make such organs.

Mechanical limbs, you just slap them on. Quick, cheap, and easy. Making sure the body doesn't reject a small interface is easy, and it's easy to swap out the limbs if they're damaged or you want a new kind.

While the technology allows for growing limbs and organs to replace those that were lost due to accidents, why do many in the setting still prefer to fix themselves with cybernetic augmentations rather than grow a new leg in a vat?

Money.

OEM limbs and organs are a luxury. Might as well ask "Why do people eat ramen noodles if filet mignon exists?"

The masses receive the cheaper mechanical option because it is cheaper, can be found on the second-hand market, and readily upgraded/repaired.

If you get a new biological arm and get it ripped off again then you're gonna be pretty upset that you have to shell out for a new one again.

If this is some factory worker then it's not feasible to wait for the growth of a new one; bread has to be on the table every night. The mortgage man always cometh!

Other answers deal well with technological concerns. Along with Azuaron, I would offer sociological concerns. This society might consider biological manipulation unethical, while mechanical manipulation is simply another tool.

This debate is currently playing out in military technology development. Some experiments in the 20th century (and likely continuing into the present) experimented on soldiers to chemically improve their capabilities. Imagine these experiments were successful in some way or another. Side effects aside (such as with steroids or methamphetamines) many people were and are horrified by the idea of biologically manipulating people to improve their skills.

The same debate plays out regarding creating designer babies. Even if we could remove diseases from their genetics, some people would disagree, whether for religious reasons, or avoiding the slippery slope down the road to eugenics.

Mechanical improvements, however, are almost universally accepted in military technological development. Creating new body armor, night vision goggles, full exo-skeletons-- there is little debate about the ethics of these mechanical improvements.

So even if biological manipulation was possible, people might be freaked out about it, grossed out by it, concerned that it would lead to eugenics, or just believe that it is plain wrong. Mechanical improvement could have similar concerns, but generally less so than biological.

Prosthetics are ancient status items.

In our world, an analogy would be a Stradivarius violin.

According to their reputation, the quality of their sound has defied attempts to explain or equal it, though this belief is disputed. The many blind experiments from 1817 to as recent as 2014) have never found any difference in sound between Stradivari's violins and high-quality violins in comparable style of other makers and periods, nor has acoustic analysis.

The fame of Stradivarius instruments is widespread, appearing in numerous works of fiction.

Playing a Stradivarius is special. In your world that is how prosthetics are. They are useful and functional, but are also status items. They are very old, and the method of their make has been lost. Most have many prior users and some have their own names. Such an item is for the very rich, or are passed down as family heirlooms. Any commoner can have a new biolimb grown but if you are the person in this generation who is using the LongClaw leg, that means something.

Some specific augmentations cannot be feasible using just biotechnology or they are just easier using electronics:

• Having telephoto lenses with variable zoom, while being sensible to UV or IR light is a cheap feature using electronics and you don't need lubrication (you can still see even if the wind creates a dust cloud).
• You could improve your resistance to frostbite with a better blood irrigation in your limbs, but you'll need also eat a lot to generate that extra heat. Mechanical limbs just don't care about being at 5ºC, they still work and you can spare that energy for other needs.

So people tend to prefer to have a "normal" body, but for some jobs you want a real upgrade

Biological Security

The motivation is similar to how some people prefer to use more primitive phones and computers for privacy reasons. These simpler devices have fewer ways to secretly gather data about the user.

If you are worried about the smartphone recording everything you say, even when you are not making a call, and you don't know enough about smartphones to take it apart and decode what information your smartphone is recording (and to whom it gets sent), then the solution might be to not use a smartphone at all.

Likewise you don't know what hidden features that new arm or liver might have and what hormones it is pumping into your immune system. Perhaps the company that makes the arm is part of an umbrella corporation and it releases a chemical that makes you drink more Coco-Cola? The genetic code is of course patented and you cannot see it. Even then you would not understand.

A mechanical arm on the other hand does not have room for such nefarious schemes. The arm has exactly 2 interfaces. One with the nerve endings and one where you plug the arm into the wall to charge at night.

Biology is its own limitation

There are material limitations, and what you might choose depends which you prioritise. Do you want the advantages of bio tissue, or the advantages of inorganic fabrication? Or some kind of blend?

Other answers have suggested temperature range and scale of touch as benefits to inorganic. But really, organic tissue is its own limitation. It damages readily, has limits on strength, pressure, tension/compression, sensory detection, form and shape (hence functionality), options for swapping between accessories as may exist with inorganic, .....

And we don't know what exactly they can do with biotech. Maybe just crude gene fixes, maybe entire new body forms.

Depends which features you value.