The problem of old-age is as old as hills. In the early centuries, finding old people of past 60 years of age used to be as rare as hen’s teeth. The longevity used to be short no matter you are Alexander the Great or Swami Vivekananda. Reasons could be many. It could be genetical, in-breeding, unhygienic living conditions, poor quality of food, both vegetarian and non-vegetarian, it could be the deadly diseases like plague and epidemics that led to mass death of millions over a period, as it happened in Europe which suffered the scourge of black death.
