The epidemiology of life and death: a critical commentary.

It is now approximately three billion years since the first appearance of life and death on this planet. Early studies identified life and death as major causes of morbidity and mortality, respectively, but further advances did not occur until recent times, when the tools of epidemiology were developed. The goals of this brief overview are to discuss the important studies that have led to our current concepts of life and death, to highlight deficiencies in existing knowledge, and to suggest directions for future research.