Darwin turned his attention towards this point and accumulated data. In the 'Descent of Man' he brought together many of the chief facts then known concerning variation in man and woman. All the evidence that he could find pointed in the same direction, and he concluded (Part II., Ch. 8) that there is a 'greater general variability in the male sex.'
Some twenty years later in a summary study of human secondary sexual characters entitled 'Man and Woman,' written as a brief introduction to a more elaborate study of the sexual instinct in man, I devoted a chapter to this question, dealing with it more comprehensively than had previously been done and drawing data from a much wider field, but finding no reason to differ fundamentally from the conclusions of Hunter, Burdach and Darwin. I could not indeed assert that as regards man the greater variability of the male is 'general,' but all the facts available since Darwin's day indicated that a greater variability of the male occurred in the majority of the groups of data investigated. And when I considered that this greater organic variational tendency of men is apparently true of psychic variations also—of genius, of idiocy and other mental anomalies having an organic basis—it seemed to me that in the greater variational tendency of man we are in the presence of a fact that has social and practical consequences of the widest significance, a fact which has affected the whole of our human civilization. Although the greater variational tendency of men is balanced by the more equable level of women, we have to recognize that the existence of the exceptional men who have largely created the lines of our progress is based on natural law. It is a conclusion which does not yet appear to me to be fundamentally affected.
There was, however, one important omission in my statement of this question, and I wish to emphasize the importance of the omission because its significance will subsequently become apparent to the reader. I said little or nothing as to the variability of men and women in size, either as regards total stature and weight, or the dimensions of parts of the body. The reason for that omission is clearly indicated in various parts of the volume and we shall encounter it in due course.
Three years later, in a volume of miscellaneous essays entitled 'The Chances of Death,' Professor Karl Pearson published a lengthy paper entitled 'Variation in Man and Woman.' This writer started with the assertion that in 'Man and Woman' I had 'done much
- I did not consider that such evidence must be absolutely rejected—I admitted it in one or two cases (printed in smaller type)—but simply that as it was liable to a discount of unknown extent it could not be placed in the first rank of evidence.