although darwin was curious about sex differences in variability throughout the animal kingdom, variability in humans was not a chief concern of his research. the first scholar to carry out a detailed empirical investigation on the question of human sex differences in variability in both physical and mental faculties, was the sexologist havelock ellis. in his 1894 publication "man and women: a study of human sexual characters", ellis dedicated an entire chapter to the subject, entitled “"the variational tendency of men"”. in this chapter he posits that "“both the physical and mental characters of men show wider limits of variation than do the physical and mental characters of women”" (p. 358). ellis documents several studies that support this assertion (see pp. 360–367), and