I’ve come across a few articles recently about how modern medicine is on the road to conquer death in the next thirty years or so. I find this to be very unlikely, and I feel that people aren’t thinking about the real issues. I’ve seen two general themes. One is that the singularity will come and change everything, which is essentially unanswerable except by rolling your eyes and backing away. The other is that death is essentially a type of disease, and we will learn to cure it.

Unfortunately, death is not a disease to be cured. It’s a fundamental aspect of life. In the competition for food and other resources necessary for life, the most significant competitors of any individual organism are the other members of its own species. They are the ones who seek to occupy exactly the same niche. Complex organisms which do not die will have more size and experience than their descendants, and will therefore tend to outcompete them. It follows that species whose organisms do not die will tend to not evolve. They will over time be outcompeted by other species which do evolve. Thus death is a key evolutionary strategy for any successful species. The fact that individuals may prefer not to die is irrelevant to long term evolutionary history.

What this means is that death is a finely tuned aspect of ourselves, just as finely tuned as our rather remarkable ability to reproduce ourselves. And it’s not just an aspect of ourselves, it’s an aspect of our evolutionary forebears for eons.

It may seem superficially that humans pass through a period of childhood, then enter a phase of stasis, and then decline and die. However, in fact humans change slowly throughout their lives. Arresting the aging process would be just as complex as arresting the growth process during the teenage years. All our bodily systems are shaped by evolution to head in a particular direction. Stopping that means changing all aspects of our bodies. It would mean a person aged 20 who does not turn into a person aged 30. That means changing a hundred different aspects of how the body grows.

The fundamental argument of the people seeking to conquer death is that the body is a machine, and that we can figure out how to fix the machine so that it does not fail. However, the bodily machine was created by an evolutionary process, not by human design. Think of the ugliest least comprehensible computer program you’ve ever seen, code which is uncommented and full of cross dependencies. Think of the hacker who wrote that code–code that works but is unmaintainable. Imagine letting that hacker work on a computer program for a million years, continually micro-optimizing and never doing a comprehensive overhaul or redesign. Now you have to reverse engineer it. That’s what figuring out the human body is like. Every system in the body has deep layers of complexity and is related to other systems in strange and surprising ways. Despite all the near-miraculous advances of modern medicine, we are still only scratching the surface of understanding how the body works. Increasing computer power will help, of course, but we don’t even know the questions to ask. This is going to be a task of many generations, and even as we start to understand it will take far more work before we have any idea how to actually change anything.

Of course I could be entirely wrong, and I do think that research on aging should continue. I just don’t see any reason for optimism. A human who does not age would really be an entirely different species. What reason do we have to think that we can create such a species any time in the foreseeable future? If we could create it, what reason do we have to think that we can somehow convert ourselves?


  1. etbe said,

    June 23, 2010 @ 12:26 am

    When people talk about preventing death, they generally mean preventing death by most diseases that are fatal nowadays. There will always be the potential for accidental death, even if it becomes increasingly rare.

    Better medical technology will probably drive more risk taking. I wouldn’t want to drive a car much faster than 130Km/h because the likely result of a crash is very bad. But if it was possible to get a cloned body without excessive expense or pain then I would probably drive in a more “exciting” manner – which of course would increase the probability of having a crash that was beyond the ability of the new medical technology to fix.

    If the life expectancy was changed from 70+ to 700+ then I don’t think that would change the evolution of society much. It seems that most changes in society don’t require a new generation. For example I can clearly recall the changes in the treatment of minority groups during my lifetime, it was significant but it was achieved through the majority of the population learning new things.

    DNA evolution has already changed a lot. Lots of people who wouldn’t have survived to breeding age or who wouldn’t have been able to breed 100 years ago are now having children. But I guess that’s not really the point of your post.

    As for a reason for optimism. I think that living to 200 is something that we can be incredibly optimistic about. Being as healthy at 150 as I am now in my 30’s would be a great thing!

    Finally the murder rate has been dropping steadily throughout recorded history. I guess that when people have hundreds of years to form grudges the incidence of murder might increase. I’m sure that no matter how good medical technology becomes people will still find ways to deliberately kill people so they can’t be revived.

  2. Simetrical said,

    June 23, 2010 @ 10:53 am

    Preventing aging is too ambitious for now, but greatly postponing death due to aging is another story. There are some body parts that consistently fail when we grow old, but many of those can be repaired, or replaced with simpler man-made versions. We already have artificial hearts, lungs, kidneys, limbs, and so on, of varying effectiveness. We can also temporarily patch up a lot of common types of organ failure by surgery or other means.

    So as long as the brain is intact, I don’t see anything that we couldn’t replace in the foreseeable future. Replacements are sometimes too clunky or expensive to be practical, but that will improve. Our identity resides in the brain, so everything else is replaceable.

    Replacing the brain with a functionally identical copy is way more difficult, because our standards are higher. An artificial heart needn’t work exactly the same as a regular one, as long as it pumps blood. An acceptable brain replacement would need to replicate every memory and detail of personality if we were to accept it, and that’s immensely harder. Plus, we probably would be afraid of that even if it were possible.

    Still, many people’s brains work well enough even late into their lives. So if you can replace most other things that fail, lifespans of a couple hundred years or more seem attainable, at least for some people. I expect that average and maximum lifespans will continue to grow longer over time without hitting any hard upper bound, although progress will sometimes be slow.

  3. Nix said,

    June 23, 2010 @ 12:26 pm

    I agree with most of what you say, but part of your argument is fallacious.

    Complex organisms which do not die will have more size and experience than their descendants, and will therefore tend to outcompete them. It follows that species whose organisms do not die will tend to not evolve. They will over time be outcompeted by other species which do evolve.

    Species do not evolve. Individuals evolve (where an individual is clearly distinguishable from others, which is generally true among the metazoa: where this is not true, e.g. in bacteria, you generally have to go back to looking at patterns of gene flow). It is perfectly possible to imagine a hypothetical organism which does not age: it has lots of offspring and outcompetes or just plain eats them (not unusual, your own offspring or better a neighbour’s are a good food source when times are tight). All those offspring will be slightly different from it: in the end, when the environment changes enough, one of them will survive where its parent does not. (A particularly likely part of the ‘environment’ here is the set of infectious diseases.)

    To me, the disposable soma hypothesis seems most plausible: there is a tradeoff between reproducing like gangbusters and staying alive. If you concentrate on one, you’re going to be really bad at the other (this is even true among wildly different things such as extremophile bacteria: the bacterium D. radiodurans, which can survive just about anything, reproduces extremely slowly).

    What’s more, making anything like present-day metazoa immortal has other problems. Among other things, as an organism ages, its gametes mutate. If an immortal organism starts out with a supply (e.g. female mammals) they’ll eventually all mutate into uselessness as they sit there waiting, or the organism will simply run out; if an organism breeds more (e.g. male mammals) they’re only experiencing selection to survive in the gamete form, so arbitrary other mutations can crop up. Eventually either of these processes will lead to an organism incapable of producing viable offspring. And once that’s happened, there can be no selective pressures for processes that elongate the organism’s life beyond that point.

    Note: there’s no ‘we must die for the good of the species’ in here. There is no ‘good of the species’. Natural selection operates on individuals and possibly small groups: there is no known mechanism by which it can apply to any larger group. ‘Species’ are a human fiction anyway.

    We can surely make ourselves last much longer: there are metazoans, even tetrapods, that do. But immortality? Not without technological assistance (i.e. medical care) as long as we breathe oxygen, are based on solute chemistry (thus dooming our DNA replication enzymes to non-perfection), and live in a universe with ionizing radiation in it. (The ‘medical care’ would need to be really extreme to extend life indefinitely, as well, e.g. something that replaces the DNA in every single cell in your body and also fixes up any other non-genetic problems that may be found. The ridiculously difficult problem of mind uploading may actually be *easier*.)

    As an aside, note that not even bacteria are immortal. Experiments have been performed in which the DNA in a haploid bacterium was radiolabelled, and the radiolabelled copy watched as the cell divided again and again. Eventually, the cell containing that mother strand gave up reproducing and died. Every time. Its daughter cells survived, but the mother was a goner. Even bacteria have a Hayflick limit!

  4. Ian Lance Taylor said,

    June 23, 2010 @ 5:14 pm

    Thanks for the comments. Y’all seem quite optimistic about significantly extending human lifespan. I’m not nearly so optimistic. Historically there have always been a few humans who lived to be 100, and that is still true today. Historically most humans have died before that point, and that is still true today. Modern medicine can certainly get a lot more people to age 90, and it can certainly make them much much healthier on the way there. But I don’t really see the evidence that it can get people past that. At a certain point all bodily systems start to fail, and I’m arguing that that is precisely what they have evolved to do. Even the brain changes with age; cognitive differences between people of different ages are well-established. Even if you could somehow replace every part of the body other than the brain, which you can’t, the brain would still die.

    Nix: I know that I was speaking loosely of evolution, but I think my argument stands nonetheless. There is no one level at which evolution works. Evolution works at several different levels simultaneously. You can speak of evolution at the level of the gene, the organism, the population, the species, and even the ecosystem. Of course the looser you get the easier it is to be led astray. But that doesn’t make the concept meaningless. Any time there is descent with modification combined with selection pressure, there is evolution. My argument does not rely on any notion of “for the good of the species,” which I agree is a canard (except possibly for our own species).

  5. Nix said,

    June 23, 2010 @ 5:33 pm

    I just ran into a description of an immortal metazoan. Turritopsis nutricula can dedifferentiate itself on demand… downside: it’s a jellyfish. Unlikely to be that helpful with making bilaterians immortal.

  6. etbe said,

    June 28, 2010 @ 6:53 pm

    Simetrical: Your brain is replaced steadily all the time. The life expectancy of any given brain cell is way less than your life expectancy. What we need to do is cause the cells to be replaced as fast as they die – this happens in relatively young people, but in old people it doesn’t. From memory I think that there’s a stage in brain development where things get trimmed at about age 18. Then from 25 or so it starts to decline.

    There has been some interesting research on brain regrowth, if you lose part of your brain you can in some situations transfer functionality to other areas. This has happened with relatively young soldiers who were shot in the head. Also sometimes when people age they gain skills that had apparently been repressed, one example was of a retired man who lost a significant part of his mathematical ability and gained artistic ability.

    The being that is you now has a quite different brain than the being that was called you 10 years ago.

    Nix: Simple reproduction is not the end of the evolutionary pressure. It’s well known that orphans tend not to do well. So a man who dies shortly after getting a woman pregnant will be less likely to have grand-children than one who stays alive to look after his children. Someone who could look out for the interests of their great-great grand-children would tend to have more descendants than someone who didn’t live so long (or didn’t live with a good quality of health). Think of the “Pak Protector” that lives for thousands of years protecting it’s descendants – it’s an interesting sci-fi concept that is based on an extrapolation of what we observe in our society.

    Ian: I think that the hardest part at the moment is dealing with cancer. Cells have a cycle count that causes them to die after a certain number of divisions. Cancers that don’t break that mechanism tend to disappear by themselves. To live for 200 years you would need to alter the cycle count in your cells but also deal with the cancer risk (which would almost be a certainty of getting cancer over that time period). There is some interesting research on animals that have a low cancer risk as well as drugs that reduce the blood flow to tumors (apparently most cancers don’t develop beyond a few cubic mm due to lack of blood – improving this mechanism would stop a large portion of the cancers that are currently fatal).

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