Alhough transhumanism is currently largely theoretical, the philosophy has numerous supporters... and numerous detractors, who regard said supporters as overly optimistic and misguided at best, and dangerous cultists masquerading as scholars at worst.
One of the main issues in executing transhumanism in reality is due the human body being a bunch of biological systems that are not only incredibly complex, but also made up of organs and other building blocks that have been built upon and modified by natural selection through millions of years. While so far there haven't been any discoveries that show the practice of transhumanism to be impossible, the human body has been proven to be a very fickle thing indeed.
Take the brain, for example. Even as Moore's Law's obituary is all but writen
, the brain still reigns as the ultimate computing machine, with its absurdly low 20 watt power consumption and enough memory to hold the internet. We currently don't know exactly why the brain is so powerful, but a good theory is that, seeing as it's a (bio)chemical machine instead of an electrical one, it's more or less immune to data corruption due to EM interference. This doesn't just protect it from EMPs, it also means it doesn't have to work with binary. Rather, the brain (possibly) works with analog, which drastically reduces the number of components needed to process data. This lets you cheat past Moore's Law's death, as it enables the processing of massive amounts of data without requiring impossibilities such as subatomic transistors. The brain is, essentially, the holy grail of computers, which is why the most powerful and innovative computers being developed right now have resorted to mimicking it. But if the only way to make computers that can perform on par with the brain is to just build another brain, and the idea of building a computer that surpasses the brain is right out, then that whole Brain Uploading thing seems pretty silly, doesn't it? Of course, if you told a man little more than a century earlier that one day we'll be building heavier then air machines that outperform birds, he'd have probably laughed in your face as well. Never underestimate science's capability to march ever forward.
In fact, it is actually the rapid pace of technological advancement that makes up some of the greatest challenges transhumanism has to overcome. Consider one of the genre-favorites — a cybernetic brain implant. Now imagine a new model with twice the capacity coming out every 12-16 months. Now imagine if every three to five years an entirely new hardware standard appears that is not backwards compatible. Added to which we have the inevitable bugs, security glitches and hardware failures — think Windows Vista, Xbox 360's RROD, etc. How many times would it be practical, ethical, or even sane for the average person to undergo brain surgery to replace or upgrade their implants? Far more convenient to put that chip in something like a wristwatch, or a cellphone; some device which can be easily and conveniently upgraded and replaced, and won't fry your brain in the event of an unexpected glitch. At most, we could use external augmentations connected to the brain through some sort of universal interface — preferably a wireless one — rather than directly implanting the entire thing. The idea isn't entirely crazy: no matter how fast computer technology advances, barring radical advances in bioengineering, the Human brain will always have an upper limit on the amount of input/output it can handle at one time. Once you have a brain/computer interface that can handle that level of I/O with perfect fidelity, just implant one with options for external hardware connections and you shouldn't need any more surgery. Show of hands — who wants an Unusual User Interface?
However, even if we manage to successfully upgrade the human brain, that's still only half the equation. To have a proper transhuman utopia one needs to also figure out how to upgrade the rest of the human body. And these are not minor upgrades, either — we're talking about gaining superhuman abilities and/or getting rid of those pesky needs of the flesh, like food, water and oxygen, all through the magic of technology. But to do so, one needs to one-up millions of years of evolution dedicated to tackling the fundamental limiting factor of life: energy.
Incresing energy efficiency is not an option, as the human metabolism is already capable of converting 40% of the energy in carbohydrates and oxygen into ATP. This is more than what street-legal car engines can pull off, and is the reason why the human body has an insanely low average power consumption of 100 watts. Increasing energy density of your bodily fuel reserves is also a tough sell, seeing as carbohydrates are already some of the most energy-dense forms of chemical energy storage out there. How else do you think the human body can go 3 weeks without food? To be fair, other hydrocarbons, like gasoline, are more energetic than sugars or lipids. But do you know what they also are? Highly flammable and annoyingly prone to evaporating into the atmosphere. To turn the average man into Super Man, it'd be most practical to implant a nuclear power plant into people's bodies and have them somehow feed off of that like those fungi from Chernobyl. That'll certainly solve the energy issue, but it'll lead to quite a few new problems that people may find even more objectionable. Really, for those who want Super-Strength, it's much simpler to put on a suit of Powered Armor, where all that fuel guzzling high-power machinery and its dangerous power source is outside of your body. And for those who want to evolve past the need to eat and breathe... eh, sorry. Future technology might expand society's energy budget, but you'll still have to resort to using that energy to produce food, ship it to people and then have the good old human metabolism — or, if we're optimistic, a disease-resistant, aging-proof version of it — turn that food into back into usable energy.
But still, just because it seems implausible or even flat-out impossible now, doesn't mean we shouldn't research it. Consider information technology: once problematic, unreliable and surrounded by naysayers, it now controls everything from critical infrastructure to nuclear weapons. From this point of view, there is still reason to believe that following one or two unexpected breakthroughs in technology, the human body may be next. There are setbacks, as there always will be for new technology, but in the end, the reward typically outweighs the risk.
This isn't exactly an open invitation to jump in head first, but delaying too much can put you years behind the competition, ethical considerations aside. If it does work, groups that green light transhumanism will leave the others in their dust. Transhumanism is potentially a significant game-changer. More capable people can make better technology, faster and more efficiently, allowing people to become more capable. In a world with transhumans, communities that do not adopt can be left without much of a fighting chance, either on the battlefield, or in the marketplace. The new technology may be unpredictable, but if it vastly outperforms the old, the alternative to embracing it may be having it sweep you aside. Take early guns for example: near as dangerous to the shooter as they are to the target, but a combination of sheer battlefield effectiveness and eventual improvements made everything else obsolete. An army cannot choose to only use swords and arrows today.
Some people regard this scenario with misgivings. They see the potential gap between enhanced and unenhanced people as turning into a combination of classism and racism. We have a history of this happening when a group gains an advantage. The enhanced humans, they fear, will become a new oppressive, ruling elite over the unenhanced masses.
What transhumanism supporters tend to predict will happen (or has already started to happen) is that the various sciences required will start their way for both prevention and repair of otherwise permanent damage (such as pacemakers or cybernetic replacements). These will encounter relatively little opposition due to their medical nature, and will in turn force their foot in the door, paving the way for ever greater advances, both from a technological and public relations standpoint.
