I am not a biologist: Far be it from me going into the details of a field I don’t fully understand. There are different theories about the causes of ageing, and not everyone agrees on which is the ‘right’ one, or how to go about solving the problem. However, based on what I have read, I have made my mind up about which theory and approach to the problem are the most convincing. In this article, I’m going to try and explain ageing in simple terms, according to the theory of accumulated metabolic damage. There are two example that help me understand the concept better, and maybe you’ll find them enlightening as well. Anyway, the bottom line is always the same: Ageing is the result of the life-long accumulation of cellular and molecular damage that the body inflicts to itself as a side-effect of its normal operations. (Note: I used to call this ‘wear-and-tear’, but it is a bit inappropriate, because the body also renews itself. There is stuff the body cannot repair, but anyway if and when I use the term ‘wear-and-tear’, I mean loosely speaking.)
As a first example of this kind of process, imagine a clean, tidy room. Books are on the shelves, the bed is made, the floor is clean and washed, everything smells nicely and is exactly where it is supposed to be. However nice this may be, we all know it’s not going to last very long. If you lock the room when it’s still clean and you never set foot in it, it’s probably going to stay clean for quite a while, but if you use it regularly, you will end up leaving pens and books out of place, scattering papers all over the desk, spilling the occasional drop of coffee on the floor, and so on. They’re just tiny little things that don’t seem much of a trouble if considered individually, but they are very sneaky: They happen all the time as a side-effect of using the room, and little by little they’re going to turn your room from an immaculate, spotless retreat into the circle of Hell where slobby people go when they die.
You can of course try a preventative approach: never leave anything around, never spill anything, and so on, but let’s face it: It’s not gonna work. If you keep using your room without ever cleaning or tidying it up, it will get to a point where it’s so filthy and messy you’d rather French-kiss a wildboar than set foot in it. The room will become unusable.
Another good example of a wear-and-tear process—which I shamelessy stole from Aubrey de Grey’s repertoire—is that of cars. A car is a machine with moving parts; as you use it, these parts will wear out because of friction, oxidation, mechanical stress, and what you have. The daily amount of damage the car inflicts on itself as a consequence of its use isn’t much, but it piles up day by day. Without proper, regular maintenance, your car will eventually become a useless piece of junk.
These are both a pretty good analogies for ageing: As you ‘use’ your body—and by use I mean simply ‘being alive’—you constantly cause some damage to it (or rather, your metabolism does). The damage occurring in a day is pretty much insignificant, but it piles up throughout your life. The good news is, your body is set up to tolerate a certain amount of that damage, and it possesses biological, self-repair machinery that fixes you up to an extent; the bad news is, your body can tolerate only a certain amount of damage, after which even your self-repair machinery will start falling apart. This is the point where the damage produced by your metabolism starts piling up faster and faster, until your body goes south on you and all kind of age-related diseases and disabilities will begin manifesting themselves. Of course, this is not all: Even if your room gets insanely messy, it’s hardly going to crumble to dust because of that, and you’ll always be able to clean it up. Too bad this is not true of humans: If your body’s inner workings get too ‘messy’, you die. (Without maintanance, your car will also fall apart beyond repair, too.) Now, I don’t really mean to burst any bubbles, but I’ve heard people comparing ageing to ‘slowly walking into the sunset’, and it seems to me it’s actually more like being tied to a wheelchair as you dash down a really steep hill overlooking a scorpion pit. With or without sunset—I don’t care, really.
Of course, there’s an obvious way of preventing your room from becoming unusable: periodic maintenance. Way before the level of untidiness of the room reaches critical levels, you arm yourself of brooms, mops, detergents, and patience, and give it a good clean. The room will be back to its ancient splendour, and the more often you clean it, the easier cleaning will be; additionally, using the room will be more practical than it would be if you cleaned it more sporadically. The same goes for cars: There are working classic cars a hundred years old around, even though they were designed to last maybe fifteen years. The reason they’re still working is because someone has done comprehensive, periodic maintenance on them.
It’s no matter of controversy that the human body is just a machine; it’s an extraordinarily complicated one, and unlike cars, it’s biological in nature, but it is still just a machine. The idea behind the SENS approach is that, just like you can tidy up your room before it turns into a jungle and you can repair your car before it exhales its last exhaust, you can repair the human body before it’s too late. Our self-repair machinery mentioned above is pretty good already—which is why humans live so much longer than other animals—and a balanced diet accompanied by exercise can definitely help with the maintenance, but this isn’t going to be enough. Those things can perhaps help slow down the rate at which metabolism wreaks havoc in your body’s tiny machinery, but it won’t eliminate the damage that’s already been done. In order to perform really comprehensive maintenance, we need to attack the problem of ageing on a much more fundamental level.