The study investigated the factors responsible for compression of mortality usually observed in human survival curves. The concept of rectangularisation was adopted to study the changes that occur in human survival curves at the older ages under the assumption that the basic mortality table is occurring in time zero. Simulations were carried out to examine the behavior of survival and cumulative death curves under varying conditions. The result revealed that the survival curve shifts to the right of the base mortality survival curve as mortality situation improves. Furthermore, the study indicated that expansion of mortality spectrum will occur if mortality curve is allowed to flow smoothly throughout the human life.