Problems concerning the study of the age of a skeletal population are explored.  Five factors are considered including environmental pressures, the initial age structure of the population, migration, epidemics and other natural disasters, and fertility.  "The analysis has been carried out by means of the simulation method, using 3 age structures of living individuals observed several hundred years in the light of various disturbances, 6 life tables and several fertility rates.  Values of expectancy of life calculated by means of the demographic method and that used in anthropology are compared."  The populations considered are from Poland. (SUMMARY IN ENG)