I’m not rethinking the desirability of immortality. That’s best left to those far from death and lacking perspective. I still think the pursuit of human immortality is a worthy cause (see here). But the more I think about it, the more I think it simply isn’t possible to radically extend lifespans for humans as we know them.
The insurmountable hurdle in the quest for immortality is going to boil down to an evolutionary box canyon where, because of all the good-enough-for-reproductive-work “choices” made before, you just can’t get there from here. Evolution rewards expediency and economy, making do with what’s at hand and finding multiple, often opposing, uses for everything biological. Because of this, attempted improvements in the workings of the body at some point lead to a problem elsewhere. Pharmaceutical development is always an attempt to improve the benefits and reduce the costs, but the tradeoffs can never completely be eliminated. When man finds a new use for a wheel it could be a table top. When evolution finds a new use for a wheel it’s likely to be the table legs, chairs, half the fireplace, the front door, and part of the driveway too.
A counter argument can be made that there are some creatures on earth that live extraordinarily long lives, and by discovering their secrets we’ll be able to emulate them. While that research no doubt will lead to some improvements in longevity, those other species aren’t us. Different evolutionary histories lead to different box canyons (e.g. trees aren’t that smart and tortoises have to bear the indignity of petting zoos). We’ve been social animals for far longer than the last decade, and as a result our immune systems may be the most complex in the world. This has allowed us to survive domesticating animals and sending kids to daycare to trade secretions, but targeting all manner of pathogens over a lifetime inevitably results in false positives. Systemic inflammation and an early demise is one of the likely results. Being warm-blooded, with a far higher metabolic rate than a bristlecone pine or tortoise, is another example of a beneficial trait that imposes a significant set of hurdles to immortality. Biology is a package deal composed of millions of interrelated pieces. Because of this evolutionary baggage, picking and choosing the traits we’d like and putting them together doesn’t mean they will work the way we intend.
Reduce/reuse/recycle engineering isn’t the only issue. Once reproduction stops, anything that sends you to an early grave after that can accumulate in the genes virtually unmolested. To a large extent, aging is the result of that genetic neglect. In theory, that category of defect should be fixable with little downside. The bad news is that there are likely millions of such defects that would need to be identified and changed. The even worse news is, once altered, many of them will turn out not to have been deleterious junk after all – which leads back to the Rube Goldberg engineering problem.
This doesn’t mean that immortal biological beings couldn’t be created someday. Unfortunately it would require a complete re-engineering from the ground up, and the final result would be something quite different from the original. It’s the same problem as with the Transhumanists’ idea of uploading our minds: Human mind and body are an inseparable, integrated whole. In fact, if you look at human behavior objectively, the body is clearly in charge of the mind. Much of what we do revolves around simply maintaining homeostasis, with emotions created to motivate us to action, and most of the rest is a direct or indirect attempt to enhance reproductive success (e.g. buying a Ferrari). What would be left if that were removed or radically altered? I’m not sure, but it definitely wouldn’t be recognizably human. Even if the technical problems of uploading a brain could be solved, once separated from the bodily milieu it would cease to be you, and that’s hardly immortality.
Though immortality may be beyond our reach, it doesn’t mean increased longevity is a lost cause. While our evolutionary heritage may have screwed us on a grand scale, increasing healthy lifespans by a significant percentage is a near certainty. If markets are allowed to operate, it could happen well within those filthy daycare tots’ lifetimes. But I’m afraid that will have to do, you lucky little bastards. Wetware life will always be too short.