Why does life seems to have a "use by" date?...
My life was a good deal simpler when the questions that arrived on my desk dealt with technical matters. Since I have branched out into philosophy I am faced with rather more slippery questions. For instance, one of my correspondents of undisclosed age wants to know why people die. I will take a whack at the subject but am not confident that I have the answer. The shallow answer is: the failure of a vital bodily system causes death. That is like saying all airplane crashes are caused by the pilot's failure to maintain control of the aircraft. The statement avoids any consideration of root causes, like a wing falling off in the case of the airplane.
In the case of human death there are some root causes that are easily disposed of. Accidental or intentional destruction of vital parts of the body will result in the death of a person at any age. Less easily understood is the effect of disease. Disease may result in the destruction of vital parts of the body but our bodies have some degree of defence against disease. In the very young those defenses may not have reached full strength. In the very old those defenses may be weakened. The result being that the same disease easily weathered by a robust adult might prove fatal to the young or old or other persons with compromised defenses.
What I think we should consider is the death of individuals where no specific injury or disease is identified, the death by "natural causes". A while back I attended the one-hundredth birthday party of my aunt, by marriage, Caroline Hawkes. She was not the oldest person in attendance. Two of her neighbors were older by a year or more. Folks say these centenarians have a combination of good genes, good habits and good luck. Caroline, a couple years after the party went to sleep one night and failed to wake up. There was essentially nothing wrong with her but a serious case of natural causes. With the best of genes, habits and luck people die at about the century mark +/- 10%. There doesn't seem to be much we can do about this. Imagine the embarrassment of the health food extremist who finds himself lying in the hospital someday dying of nothing.
Those of us of advanced years have noticed a sort of gradual decline in strength, stamina and resilience. We get "age spots", the skin sags and wrinkles, the hair and teeth fall out, the hearing and eyesight dwindle, the mind wanders. These are things that remind us that we have a built in expiration date. I suppose that the question I am supposed to answer is - "Why should human beings have an expiration date?" I have a few possibilities in mind.
Let's consider the connection between lifespan and evolution. Evolution operates on a trial and error basis. If and only if a random change in the DNA that controls the construction and operation of the living being creates an advantage in the competition for food and mates then the population carrying that changed DNA flourishes and the population without that advantage dies out. It is not clear to me that there is any evolutionary advantage in human life spans that extend much beyond fifty years when most of an individuals reproduction has been accomplished. You could argue that men should live longer than women and take new wives when the old one is worn out but that is evolution for you - it can't explain the wrongness of that argument. I think that our expiration date being so late is counter-evolutionary, leaving a large population of people with diminished capacity to be supported by the reproducing population.
What would happen if people lived a very long time, faithfully replicating the cells of a healthy adult until their luck eventually runs out or their bad habits get them? One thing pretty clear is that our reproduction would tend to overwhelm our environment's ability to provide for us. Of course scarce resources will limit the reproduction rate so populations as a whole are self limiting but the quality of life for the individuals in such a scenario is apt to be grim. A human population constantly pressing the limit of life sustaining resources is not one that has much leisure time to ponder the workings of the universe and experiment by altering causal event chains. (See the "Why Is There Life" page.) Having a built in expiration date that provides time for reproduction plus a significant reserve for leisure activities while still keeping the population well below the limit imposed by scarce resources, seems like it might just be part of a well planned universe.
Here is a speculative idea. Suppose, as I suggest on the "Why Is There Life" page, humans are contributing variety to the universe. We have pretty good evidence that the universe itself has a finite lifetime. Might there be some urgency in getting the job of exploring the possibilities of the universe done on time. If people had a potentially unending string of days ahead of them I suspect that we would live our lives quite differently than we do now. Tasks without deadlines take forever.
Here is a more speculative idea. Perhaps people die for the same reason that the U. S. Marines do not spend an entire career in boot camp at Paris Island. What if this life we live in our human bodies is preparation for the real job that must be done. Here I insert a quote from the "Why Is There Life" page:
In spite of centuries of effort by physicists, biologists, psychologists, philosophers, theologians and the common woman and man, the true nature of consciousness and existence of free will, remain open questions. Intuitively the existence of free will seems obvious to me. I feel myself making conscious choices throughout the day, some inconsequential, others portentous (full of unspecifiable significance, exciting wonder and awe); some well thought out, others less so. I am absolutely convinced that at any instant a different choice might have been made. Of course that conviction might be totally mistaken. Perhaps my causally closed brain is deceiving me. Nevertheless, there it is. I am more comfortable contemplating the "something else" that is the seat of my consciousness than confronting the futility that flows from the alternative of rigid causal closure.
Perhaps that decision making machinery which we experience as consciousness is the point of human existence. As humans we seem to spend a lot of our lives exercising our consciousness. It pleases me to think that it lives on, in some unimaginable fashion, after our work here is done.
Well all I promised was a mind dump on the subject of why people must die. I guess what I have said is all that I have at the moment. Please feel free to email me J D Jones, to explain what a fool I am to harbor these thoughts.