This objection is very simple to explain and even simpler to dismantle, because it boils down to a gross misunderstanding.
Whoever raises this objection generally says that with ageing comes experience, that later in life people are generally happier, more accomplished, and so on. I have nothing to object to that, except that all those nice things are a (possible) consequence of chronological ageing, most definitely not of biological ageing. It is not very often that people mix the two up, but at times they do, so let us clarify once and for all what the difference is.
Chronological ageing is nothing more, nothing less than the passing of time. Becoming chronologically older simply means that the time you’ve existed for is getting longer. There’s nothing wrong with it, and no one (to my knowledge) wants to stop, ‘cure’, or reverse chronological ageing—especially because that would be a bit complicated to do and it would have annoying side-effects, such as time freezing or rewinding your life back to your elementary school years, possibly dragging the entire universe along, and would do nothing to eliminate the ill health of old age. Doesn’t sound like a lot of fun—and I speak as a chap with a thing for time travel.
Biological ageing is, simply put, a process of damage accumulation in your body as time goes by. While chronological age is a measure of how long you’ve been around, biological age is a measure of how badly your body is doing. Biological ageing depends on chronological ageing: Without the passing of time, nothing at all would happen, and in particular your body would not suffer any damage. (The downside is that the processes keeping you alive wouldn’t happen either, so your life wouldn’t be especially exciting.) However, chronological ageing does not cause biological ageing. Biological ageing is a side-effect of how our bodies work. If they worked differently (as in the case of negligible senescing animals), we would not age biologically despite the passing of time. As a matter of fact, chronological and biological ageing don’t even have to go at the same pace. If you lost the genetic lottery, or if you lead an unhealthy lifestyle (for example if you smoke, stuff your face in junk food or sugar, or get little-to-no exercise), you might actually age faster, biologically speaking, than you otherwise would. That is because you’d be speeding up the creation of age-related damage and/or adding other damage on top of it. You might be 30 chronological years old and 50 biological years old. In other words, you would carry around at age 30 the same amount of damage of a typical 50-year-old. Conversely, if you won the genetic lottery, or if you are a fanatic of healthy lifestyles, you might be 40 years old and yet be biologically 30. (Unfortunately, it is not as easy as you might think. Since there’s no real limit to the amount of extra damage you can cause to your body, it’s easy to be biologically much older than your chronological age. However, even the luckiest player of the genetic lotto, leading the healthiest of the lifestyles, cannot undo the amount of damage their body has already suffered—not without rejuvenation at least, because our bodies are simply not equipped to do so. So don’t expect to be biologically much younger than your chronological age, regardless of how much effort you put into it.)
In case you hadn’t figured it out yet, biological ageing is the one of the two which we’d like to undo.
Now that we have cleared the difference between the two types of ageing, it’s easy to see a few things:
- Experience, sense of accomplishment, and all the other good things mentioned at the beginning of this article can be consequences of chronological ageing. As your life goes on, you have the chance to do more things, accrue experience, accomplish more good things and thus feel happier. This doesn’t necessarily have to be the case, though: If you spent your entire life sitting on your arse doing nothing at all, none of these things would happen and you probably wouldn’t be much more happy or accomplished at age 80 than you were at age 20.
- Biological ageing does not help you to accomplish any of the things in point 1, and it is certainly not necessary to accomplish any of them. As a matter of fact, the opposite is true: Since biological ageing makes you gradually more sick, it makes it increasingly difficult to do anything at all, and to top it all, you need to add the suffering caused by being sick. When you’re 80, you may feel accomplished for the things you did when you were younger and healthier, but you can’t expect to do many other things, nor to enjoy the feeling of accomplishment too much, because you’re too busy being sick.
- Eliminating biological ageing would give you the chance to continue doing the things you love, make more experiences, and feel even more accomplished and happy. If the ill health of old age was taken out of the equation, your health as an 80-year-old would be the same as a 25-year-old or so, and you’d have the possibility to accomplish much more than you already had. You could be just a regular 80-year-old who’s led a happy life, but is now very sick and with not much life left ahead, or you could be a perfectly healthy 80-year-old, who’s led a happy life and has all the time in the world left ahead, ready for more challenges, accomplishments, and all the happiness that they can bring.
In short, the answer to this objection is that rejuvenation would not take away the good sides of chronological ageing; it would not undo your life experience and it would not take your accomplishments from you. All it would do is eliminating biological ageing and all the diseases and suffering that come with it, letting you enjoy the pluses of chronological ageing for longer and more intensely.