NUTRITION AND LONGEVITY

Heredity, external environment, and nutrition are significant factors in determining the length of life. The significance of heredity is emphasized when the mode of inquiry is that of gathering data relating to persons who, at the time of selection, have already attained to noteworthy longevity. Without necessarily questioning the conclusion thus reached that heredity is probably the dominant factor in longevity, the thoughtful student will not fail to reflect that this method of investigation is fitted primarily to bring to light any correlation which may exist between the longevity of the individual and that of his parents and grandparents, whose ages at death will usually stand out as clear-cut quantitative data in such an inquiry. The method is less able apparently to establish correlations with the factors of external environment and of nutrition or food habit, because the environmental conditions of a lifetime cannot, in normal human experience, be ascertained