Aging describes physical, psychological, and social changes that take place over time. Aging in humans initially brings benefits, such as being able to get in to R-rated movies and bars, but tends to end rather badly, with a deterioration in physical and mental abilities.
It is estimated that 100% of humans suffer from aging, with most cases resulting in death. This unpleasant conclusion motivates efforts to understand and alter the aging process. Also, it's rich territory for those who seek to extend life through religion, pseudoscientific "elixirs of life", and, of course, the cosmetics industry.
 Why do humans physically age?
Leonard Hayflick, a Professor of Medical Microbiology at Stanford University School of Medicine, proposed an inbuilt life-span for cells. In 2009 the Nobel Prize in Physiology or Medicine was awarded jointly to Elizabeth Blackburn, Carol Greider and Jack Szostak for their work in establishing that telomeres were part of the mechanism that prevented chromosomal deterioration, forming a kind of biological clock. Telomeres decrease in number as the cell ages, over time increasing the likelihood of deterioration.
Not all cells are subject to this biological clock, a failure of this mechanism being a reason why cancer cells can multiply out of control. Cells are split in to two categories in this regard: mortal and immortal. Immortal cells maintain their number of telomeres, while mortal cells have a finite number of divisions.
This limit on cell division is believed to be the reason why humans physically age, and, in their autumn years, deteriorate in physical condition.
Other explanations involve evolutionary theories, such as the disposable soma theory.
 Religious explanation
We age and deteriorate because:
- God is powerless to prevent it.
- God can prevent it, but wants us to suffer.
- The Devil did it.
Pick any two.
 See also
- ↑ Other symptoms include regular reading of The Daily Mail, use of racist language in casual conversation, and a wish that the younger generation be required to do national service.
- ↑ PubMed:14315085 THE LIMITED IN VITRO LIFETIME OF HUMAN DIPLOID CELL STRAINS.