Immortality

To live forever. Can we do it? Do we want to do it?

In medieval Britain, life expectancy was 30; in the early 20th century it was 45 and now in 2010, the world average is around 67 years. Of course there are currently big regional differences. The United States shows 77 to 80 while in Canada it is over 80. Macau, a special administrative region of China apparently has the world's longest life expectancy of 84.4 years. In contrast to that, there are a few countries in Africa listed as being under 40.

Such statistics show that life expectancy is definitely going up. There are several obvious factors to explain this: better nutrition, better medical care and better public health. Nevertheless, there has to be physical limits to what all this can achieve.

In 1961, Leonard Hayflick, an American scientist, discovered that human cells divide a finite number of times, usually between 40 to 60 times then stop. After that, the cell just ages and dies. This discovery refuted the contention by Alexis Carrel, a Nobel Prize winning French surgeon, made at the beginning of the 20th century that cells were immortal and would divide forever. The "Hayflick limit" is now known as the maximum length of time a cell will live or successfully divide before division stops and the cell dies.

It has been discovered that this limit corresponds to the length of telomere at the end of a strand of DNA. The end of a DNA strand, the telomere cannot be fully copied during cell division. As a consequence, part of the telomeres is lost with each cell division until the point is reached where the telomere is gone and the cell stops dividing. At this point, the cell eventually dies. Cancer cells, on the other hand, seem to possess an enzyme which can restore the telomere length and these cells are not governed by the Hayflick limit. They continue to divide indefinitely.

For the moment, it seems, we humans cannot physically live forever because our cells cannot divide forever. Eventually, the imperfect cell division we all have slowly fails; we age and we die. This is right now for all of us an inescapable fact of life.

Even if we could live forever, would we be able to do it? Psychologically, it strikes me that we seem to be built for only a certain period of time. I suppose this is very much tied to our physical limitations, the current length of our longevity. We lead, for lack of a better word, a productive life then we retire. We stop being, well, productive. Yes, I understand the exceptions but I'm referring to productive in the sense of a job, family and such.

Of course, I am sure that our "desire to live" is very much tied to our physical well being. As we get older, we begin to suffer from various health problems; the wheels start falling off the wagon, so to speak. We just get tired. In that sense, we just eventually give up the ghost; we run out of gas. I actually heard an elderly man, who was suffering from a physical decline, say that he was tired and he was ready to go. Yes, he had run out of gas.

Psychologically, are we built to live longer? I have actually heard people, elderly people point out that all of their friends are gone. They have outlived everybody else and there is nobody of their peer group left. It's curious that they have not made new friends; they haven't developed a new peer group. Or is a peer group more a function of at what age did one make those friends? A friend made at the age of 20 is a friend while a friend made at the age of 70 is not quite the same thing?

Living longer is tied to health. Wanting to live longer may also be tied to health. The old saying is "health is everything" for without it, living may just not be worthwhile. I am certain that people from even just 100 years ago would be envious of our life expectancy. I wonder how envious we would be of the people living 100 years from now.

2010-06-25