At the age of twelve years, the human body is at its most vigorous. It has yet to reach its full size and strength, and its owner his or her full intelligence; but at this age the likelihood of death is least. Earlier, we were infants and young children, and consequently more vulnerable; later, we shall undergo a progressive loss of our vigour and resistance which, though imperceptible at first, will finally become so steep that we can live no longer, however well we look after ourselves, and however well society, and our doctors, look after us. This decline in vigour with the passing of time is called ageing. It is one of the most unpleasant discoveries which we all make that we must decline in this way, that if we escape wars, accidents and diseases we shall eventually 'die of old age', and that this happens at a rate which differs little from person to person, so that there are heavy odds in favour of our dying between the ages of sixty - five and eighty. Some of us will die sooner, a few will live longer - on into a ninth or tenth decade. But the chances are against it, and there is a virtual limit on how long we can hope to remain alive, however lucky and robust we are.
Normal people tend to forget this process unless and until they are reminded of it. We are so familiar with the fact that man ages, that people have for years assumed that the process of losing vigour with time, of becoming more likely to die the older we get, was something self - evident, like the cooling of a hot kettle or the wearing - out of a pair of shoes. They have also assumed that all animals, and probably other organisms such as trees, or even the universe itself, must in the course of time 'wear out'. Most animals we commonly observe do in fact age as we do if they survive long enough; and mechanical systems like a wound - up watch, or the sun, do in fact run out of energy in accordance with the second law of thermodynamics (whether the whole universe does so is a moot point at present). But these are not analogous to what happens when man ages. A run - down watch is still a watch and can be rewound. An old watch, by contrast, becomes so worn and unreliable that it eventually stops working altogether. It is rather like the engine of a car, which can be repaired and even remade, but which eventually is replaced by a new engine. But a human body is not a car, no matter how much you may like to think so. There is no sudden change in the human body which marks the oncoming of old age. The changes are gradual and, at first, are often scarcely perceptible. It is often said that age is a state of mind, and this is true in part. If you feel young, you will be young, but this does not mean that you can avoid the ageing process. The ageing process is a biological process which cannot be avoided, no matter how much you may like to think you can.
The best current medical opinion seems to be that we are born with a sort of 'clock' inside us which determines how long we can live. This 'clock' is thought to be in the genes, and it is believed that we inherit it from our parents. The idea is that the 'clock' starts ticking at birth, and that it keeps on ticking until it runs out of time. Some people believe that this 'clock' can be 'reset' by things like diet, exercise, or drugs, but there is no real evidence for this at present. It is also believed that the rate of ageing can be slowed down by diet, exercise, or drugs, but again, there is no real evidence for this at present. The fact that some people live longer than others may be due to differences in their genes, or it may be due to differences in their lifestyle. It is likely that both factors play a role. But whatever the cause, the fact remains that we all age, and that we all die.
The ageing process has many implications for society. For example, as the population ages, there will be more and more people who are no longer able to work, and who will need to be supported by society. There will also be more and more people who are ill, and who will need medical care. This will put a strain on the resources of society, both in terms of money and in terms of manpower. Another implication is that as people age, they will become more and more different from each other. Some people will age gracefully, while others will age badly. Some people will be able to cope with the ageing process, while others will not. This will make it more difficult for society to deal with the ageing population as a whole.
In conclusion, the ageing process is a complex and unavoidable biological process which has many implications for society. We need to understand it better if we are going to be able to deal with it effectively.