I take good care of my teeth. I have required only two, maybe three, small fillings since I was eight. But a couple of years ago a shard fell off one of my lower incisors when I took a bite. When I visited the dentist, he told me the same thing was about to happen to two others, and that he would need to cap them, just as he once capped my canines, which had been worn level to the incisors over the years.
"My teeth are getting old," I said. "They've been biting for the almost fifty-five years."
That got me thinking about the eternal quest for an elixir of youth, or some formula for the great extension of human life, and how the inventors of these schemes never think about teeth and brains.
First of all, so complex is the human body that it is hardly imaginable that ageing can be fought with a simple, one-off treatment, or even a simple periodic treatment. "Youth therapy", as I shall call it would have to entail a carefully managed cocktail of drugs, and possibly physical therapies, applied over the whole of one's life, and replete with a whole raft of side effects.
The causes of ageing are not known, but some hypotheses include the shortening of telomeres with each cell division, damage caused by free radicals produced by that essential poison, oxygen, the accumulation of wastes, and so forth. No doubt many factors are involved. But all of them boil down to the same truism: no system is perfect. The chemical composition of your body changes with every breath you inhale or exhale, every bite you take, and any movement you perform. Your body is like a waterfall: forever changing, and forever attempting to maintain its form. It is constantly wearing out and constantly repairing itself. But because the process is not 100% perfect, the wear and tear will eventually overtake the repair.
It is important to understand that not all non-infectious disorders are due to ageing. When wear and tear overtake repair in the joints, we call it arthritis. Youth therapy would slow it down, but obesity, long term heavy lifting, and a severe injury to the joint will all tip the scales towards arthritis; if you live long enough, it will catch up with you. Age will weaken the heart, but so will obesity, lack of exercise, smoking, and hypertension. Youth therapy may prevent hypertension under normal circumstances, but if you consume too much alcohol or salt it will catch up with you. Ageing thins the skin and leads to wrinkles, but so does sun exposure. No matter how well youth therapy slows it down, eventually the cumulative effect of the sun will have its effect. Sun exposure will also eventually lead to skin cancer; if you live long enough, you will get it. The same, for that matter, goes for other carcinogens: radiation, chemicals, and viruses. You can never avoid them altogether, and the longer you live the more exposure you will get. Hopefully, by the time youth therapy becomes a reality, they will have found a cure for cancer.
What about teeth and brains?
Teeth. After your baby teeth fall out, you get only one set. They don't grow. They just wear down with constant biting and chewing, and fall out due to decay or accidents. Will everybody over the age of (say) 150 be reduced to chewing on their gums, or getting false teeth? Or perhaps science will find a way to make new teeth grow - by cloning, maybe. Writers practically never think of that.
Brains. This is a bit more serious. In once Gary Larsen cartoon, a schoolboy puts up his hand and says, "Please, miss, may I be excused? My brain is full." But it might be true. Writers always seem to assume that the Methuselahs can go on thinking and remembering forever. But both activities require the growth and expansion of neurons (nerve cells), and the brain has only a finite capacity. Under hypnosis and other altered states people have been shown to activate memories - which can be proved to have been correct - of things they thought they had forgotten. It would appear that overlooked memories are not discarded, but simply buried, as if shelved in a folder marked, "Not obviously needed, but keep for possible future use." But what will happen after (say) 300 years? Will it simply become impossible to add anything more to the memory file? Will the brain become so cluttered that relevant information becomes difficult to access, so that thinking becomes bogged down? Or will the brain find some way to overwrite the old memories, and if so, will the new information get mixed up with what is left of the old, so that the mind malfunctions? Is it, in fact, possible for the brain to become full? It is worth considering.
There are also problems with bionics, as the next article will show.
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