stature of individual parents is shown by the oblique line, the stature of children by the dotted curve, and the mean stature of the race in the horizontal dotted line.
One of the chief aims and results of statistical study is to eliminate individual peculiarities and to obtain general and average results.
Fig. 49. Diagram to Illustrate Three Kinds of Inheritance Described by Galton. (After Walter.)
Such work may be of great importance in the study of heredity, especially where questions of the occurrence or distribution of particular phenomena are concerned; but the causes of heredity are individual and physiological, and averages are of less value in finding the causes of such phenomena than is the intensive study of individual cases.
By observation alone it is usually impossible to distinguish between inherited and environmental resemblances and differences, and yet this distinction is essential to any study of inheritance. If all sorts of likenesses and unlikenesses are lumped together, whether inherited or not, our study of inheritance can only end in confusion. The value of statistics depends upon a proper classification of the things measured and enumerated, and if things which are not commensurable are grouped together the results may be quite misleading and worthless. Unfortunately Galton and Pearson, as well as some of their followers, have not carefully distinguished between hereditary and environmental characters.
