Bertolt Meyer's amazing bionic hand controlled by an iPhone app is a glimpse of the advances being made in prosthetics. But in years to come, will everyone want one?

Bertolt Meyer is used to being viewed as not fully human. Born with a stump where his left hand should have been, he spent his childhood wearing a hook connected to an elaborate pulley and harness. "To open the hook and grasp things I had to flex my shoulders like this," he says, striking a he-man pose. "The harness was very uncomfortable. To stop it chafing my skin, I had to wear a shirt underneath it at all times. I was always sweating."

Even when, at the age of 19, Meyer exchanged his body-powered hook for a myoelectric prosthesis with a more realistic plastic hand, he kept his disfigured left arm hidden from view. "It wasn't simply a question of aesthetics," he explains, proffering the plastic hand, now grubby and discoloured with use. "You have to understand, this is a stigma. People think it's weird and that is how you come to perceive it. You walk around with a sense of shame."

Today, that shame is gone. In 2009 Meyer, a social psychologist at the University of Zurich, was fitted with an i-limb, a state-of-the-art bionic prosthesis developed by a Scottish company, Touch Bionics, that comes with an aluminium chassis and 24 different grip patterns. To select a new suite of gestures, Meyer simply taps an app on his iPhone.

"This is the first prosthesis where the aesthetics match the engineering," he says, balancing a Biro between his purring electronic fingers. "It's part of me and I'm proud of it."

Since appearing in the Channel 4 documentary How to Build a Bionic Man, in which he allowed engineers to build a robotic replica of the rest of his body complete with artificial heart, lungs and an alarming prosthetic likeness of his face, Meyer has become something of a poster boy for "transhumanism". Encompassing everything from robotic limbs to memory-enhancing neural implants to gene therapies that slow ageing, transhumanism (or posthumanism) concerns the technologies and drugs that are rapidly altering the limits of human performance, as well as notions about what we might look like in future.

As Nick Bostrom, the head of the Future of Humanity Institute at the University of Oxford and a leading transhumanist thinker puts it, transhumanism "challenges the premise that the human condition is and will remain essentially unalterable". "It seems to me fairly obvious why one might have reason to desire to become a posthuman in the sense of having a greatly enhanced capacity to stay alive and healthy," he writes. "I suspect that the majority of humankind already has such a desire implicitly."

But while some medical interventions such as organ transplants to replace malfunctioning livers and kidneys, or vaccines to boost the immune system, command wide social acceptance, others invite moral approbation. This is particularly the case where the enhancement is regarded as a vanity or may be detrimental to health, as was the case with substandard silicon breast implants.

Then there is the question of access – an i-limb costs £30,000, while an artificial heart will set you back £70,000 – and whether it is OK to turn a blind eye to the "off-label" use of drugs such as Ritalin, which was developed as a treatment for attention deficit hyperactivity disorder, but is increasingly being used to enhance cognitive performance.

Even more ethically fraught is the line between restorative therapy and elective surgery. Last year, for instance, an Austrian man who damaged his hand in a motorcycle accident opted for an amputation and had a bionic replacement fitted.

At the moment, bionic hands are poor substitutes for the real thing – they can grasp and manipulate objects, but cannot feel. But what if in the future we could make bionic hands with a sense of touch that were also capable of enhanced performance? Would we be happy if a struggling concert pianist elected to amputate his hand so that he could perform Rachmaninoff's infamously difficult third concerto?

For the moment, the answer is almost certainly no, but that may change as people become more comfortable with posthuman technologies and the opportunities they afford for improved health and function. "What's crucial about these technologies is they don't just repair us, they make us better than well," says Andy Miah, director of the Creative Futures Institute and professor of ethics and emerging technologies at the University of the West of Scotland. "The human enhancement market will reveal the truth about our biological conditions – we are all disabled. This is why human enhancements are here to stay and likely to become more popular."

A good example of the way that these technologies are already changing our perception of human identity and notions of disability comes from the world of sport. When Oscar Pistorius donned a pair of carbon-fibre blades to compete alongside able-bodied athletes at the 2012 Olympics, he had ceased to be a disabled athlete; instead, he offered us a glimpse of a "superhuman" future where Paralympians aided by bionics or performance-enhancing drugs might set hitherto unimaginable sporting records. At the moment, such enhancements are considered unfair and athletes who seek to evade anti-doping regulations are pilloried as cheats. But in a posthuman future where everyone has access to these technologies, such objections may become moot. As Bostrom puts it: "If every athlete takes a lot of dangerous performance-enhancing drugs, there will still only be one gold medallist."

Future prosthetic limbs will be immersed within our flesh, rather than being outside it or replacing it. Athletes will also be able to use 3D printing to create new limbs perfectly tailored to their bodies, or grow replacement body parts when their old ones wear out.

Nor is bionics the only technology transforming norms of health and human performance. For example, in search of enhanced cognitive performance, many people are experimenting with modafinil, a treatment for narcolepsy, while others routinely take selective serotonin reuptake inhibitors (SSRIs) such as Paxil and Zoloft to regulate their moods and sense of wellbeing. These drugs are but the forerunners of a new generation of neuroenhancers and brain stimulation devices that promise shortcuts to even greater intellectual heights – and all without the social awkwardness we usually associate with superior cognitive functioning (think Bradley Cooper in Limitless, rather than Dustin Hoffman in Rain Man).

In Switzerland, which leads the way in many of these technologies and therapies, concerns about the health and ethical impacts are leading to calls for greater regulation. Currently, there are three proposals before the Swiss legislature, many of them focusing on Ritalin, which is manufactured by the Swiss pharmaceuticals firm Novartis. In June the Swiss public health service reported that adolescent use of methylphenidate, the generic name for Ritalin, had increased by 40% between 2005 and 2008, mirroring trends in the US where off-label use is rife among high-school and college students. There is similar concern about the wide uptake of anti-anxiety drugs as pharmaceutical companies seek to redefine social pathologies as treatable psychiatric conditions and aggressively market the therapies to consumers. Meanwhile, Martial Saugy, the head of Switzerland's anti-doping laboratory, remains under fire over US allegations that he helped Lance Armstrong evade doping tests before the 2002 Tour de France – a row that has highlighted the scope for sporting figures to abuse anabolic steroids and other performance-enhancing supplements.

The problem is that as technology blurs the distinction between illness and optimal health, it becomes increasingly difficult to distinguish normal from abnormal. "It's not only question of human enhancement," says Anne Eckhardt, the author of a recent report on the opportunities and risks of the human enhancement market for the Swiss Centre for Technology Assessment. "It's also about medicalisation and changing definitions of disease and disability."

Like Siegfried tasting the blood of the dragon, people have long dreamt of acquiring superhuman powers. The difference today is that it is no longer enough to manipulate our external environment by, for instance, donning a pair of Nikes or boarding a plane. Instead, enhancement increasingly focuses on the re-engineering of bodies and minds themselves.

For the moment, this posthuman future still lies some way off. We don't need a brain implant to use Google – Google's glasses, iPads and mobile phones are, at the moment, more than sufficient for most people's needs. "In the long run, technology will surpass our biological nature, but we should not underestimate the technical challenges in getting to that stage," says Bostrom.

It is an assessment with which Meyer concurs. Since being fitted with his i-limb, Meyer says that actions that used to be unimaginable – such as wheeling a suitcase through duty free while talking on his mobile phone – he now performs with confidence and ease. However, although the i-limb has enabled him to transcend his feelings of inadequacy and shame, he is a long way from considering himself transhuman, let alone superhuman.

"It's a question of standards," he says. "Compared to the normal human standard, I wouldn't describe myself as transhuman, but compared to my own standard, then yes."

That could soon change however. Meyer is already on his fourth generation i-limb and during the filming of the Channel 4 documentary he saw how US military-funded research is resulting in ever more sophisticated developments, including robotic legs with articulated joints that can negotiate stairs and give the appearance of a natural walking gait. "The question is, as the technology gets better, will it become the norm to have one of these, and what will people go through to get one?" asks Meyer, indicating his i-limb with his "good" hand.

The only point in the Channel 4 documentary at which Meyer appeared to balk at the brave new transhuman future was when he came face to face with "Bionic Bertolt" – the robot bearing his hand and a prosthetic version of his face. He was clearly appalled by the transformation. "It was a face version of this," he says tapping his old plastic prosthesis. "It really freaked me out."

Indeed, Meyer's visceral reaction drove home the extent to which these posthuman technologies provoke visions of dystopian futures or what Miah pithily calls "the yuck factor".

Ultimately, however, these are technical issues and Meyer recognises that it is only a matter of time before engineering companies are in a position to offer us products that not only look human but offer functionality way beyond the human. "That is the point where we may need to find a larger set of ethical criteria, because, from what I have seen, we cannot rely on engineers and business people to come up with them," he warns.

Bertolt Meyer will talk about cyborgs and the future of biotech, at the Saturday morning session of FutureFest

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