The following have been considered as probable factors of longevity. (1) Heredity: The significance and the influence of heredity in longevity are self-evident. There are families whose members have been observed to live longer than the average human life expectancy, except in cases where death occurs because of an accident. In this connection it is relevant to mention the research done by Raymond Peril. In a book that he co-authored with his daughter, he studied a family that had a record of longevity going back seven generations. The total number of years going back seven generations in that family was 699 years, including two persons who were killed in an accident. In addition, in more recent statistics conducted by insurance companies it has been proven that longevity in the progenitor has a direct influence on longevity in the progeny.
The heredity factor can be neutralized by other factors such as environment and bad habits. However, heredity can explain the reason why certain individuals living under unfavorable circumstances, such as alcoholics, can live longer. An offspring inherits strong and healthy body parts and organs from parents, including the nervous system and blood circulation. The famous proverb, "The age of a person can be gauged from the shape of his arteries," is based upon recognition of this heredity factor. In other words, for a number of people, when they reach their old age, their arteries become blocked because of hereditary traits. Moreover, the majority of the people who die before the age of ninety because of a heart attack or stroke have been found to suffer from arteriosclerosis.
(2) Environment: This is the second most important factor in longevity. The environment that offers moderate climate and clean air, is free of harmful microbes and poisons, and contains safe and peaceful living conditions has a bearing upon the well being and longevity of its inhabitants. (3) Profession: The type of work and the working conditions as well as the duration in hours, in addition to spiritual and psychological activities, have an impact upon longevity. It appears that when a person enjoys good physical health and mental tranquility, it affects their life span significantly. On the other hand, a stressful life accompanied by a lack of physical respite and mental peace, even more so than hard physical and psychological labor, reduces life span. It is for this reason that there are more persons enjoying longevity among religious scholars and prime ministers than among ordinary people. This longevity is directly related to their style of working and managing their stress under the constant pressure that is exerted by their profession. It is for this reason that joblessness and early retirement at a younger age might actually lead to the shortening of one's life span.
(4) Nutrition: The kinds of food and the amount we consume have an impact upon our life span. The majority of the people whose life span exceeded more than a hundred years have been found to be dieters. There are numerous proverbs that signify the harm caused by overeating. Among these are: "A person digs his grave with his own teeth." To be sure, overeating requires the entire body to work harder and is a cause of digestive disorders, heart and kidney diseases, and other ailments. Unfortunately, these overeaters enjoy enormous energy by which they are deceived until symptoms of disorders begin to surface. During World War I, it was observed that death as a result of diabetes had significantly declined in some countries. The main reason was the shortage of food in those areas. Hence, it appears that poverty as a cause of reduced intake of food is a blessing in disguise. Moreover, consumption of large amounts of meat after the age of forty is extremely harmful.
Dr. McCay's experiments on mice at Cornell University have demonstrated that thin mice were able to overcome fat ones. A mouse reaches physical maturity at the age of four months; becomes old at two years, and dies before three. Dr. McCay's experiments involved keeping a group of mice under a strict low calorie diet that was enriched with vitamins and minerals. After some time he came to this conclusion: The period of their physical maturity could be prolonged to a thousand days instead of four months. Further, he observed that the oldest mice who were fed on a regular diet died after 965 days. But the mice who were kept under strict diet remained young and full of energy for a longer than usual time. In relative comparison to a human life span, this latter group had lived a life of a hundred or a hundred and fifty years. More importantly, this group remained healthier, suffering no ailments, and smarter than those who were on a regular diet. Such experiments have been conducted on fish and amphibians with similar results.
It is important to bear in mind that just as overeating can become a cause for a shorter life span, poor eating can lead to a surge in illness and a shortening of life span. That is, dieting must be accompanied with proper nourishment, otherwise it could lead to one being afflicted with diseases.
The Twelfth Imam Endeavors to Defend Islam during the Occultation
