This book is focused on the principals and methods of using growth layers formed in teeth and bones of mammals and to make a judgement on essential traits of the animal's life history. Nearly in all mammalian species including man, the age of individuals can be determined from the number of growth layers and, at least in some of them, it is possible to estimate the season of an animal's birth and death, the age of sexual maturation, periodicity of reproduction, certain feeding habits and other aspects of the individual's biology. It is also possible, from tooth enamel analysis, to assess dose of radiation accumulated by animals and human beings during their lifetime. The book is intended mainly for zoologists, wild-game biologists, and zoo-archaeologists, but some of the sections can also be of interest for anthropologists, radio-ecologists and conservation biologists.