The tendency of the fair energetic type, the type of the northern European man, to sexuality may be connected with the fact that the violent and criminal man who commits sexual crimes tends to be fair even amid a dark population. Criminals on the whole would appear to tend to be dark rather than fair; but Marro found in Italy that the group of sexual offenders differed from all other groups of criminals in that their hair was predominantly fair. (Caratteri del Delinquenti, p. 374.) Ottolenghi, in the same way, in examining 100 sexual offenders, found that they showed 17 per cent., of fair hair, though criminals generally (on a basis of nearly 2000) showed only 6 per cent., and normal persons (nearly 1000) 9 per cent. Similarly while the normal persons showed only 20 per cent. of blue eyes and criminals generally 36 per cent., the sexual offenders showed 50 per cent. of blue eyes. (Ottolenghi, Archivio di Psichiatria, fasc. vi, 1888, p. 573.) Burton remarked (Anatomy of Melancholy, Part III, Section II, Mem. II, Subs. II) that in all ages most amorous young men have been yellow-haired, adding, "Synesius holds every effeminate fellow or adulterer is fair-haired." In folk-lore, it has been noted (Κρυπτάδια, vol. ii, p. 258), red or yellow hair is sometimes regarded as a mark of sexuality.
In harmony with this fairness, sexual offenders would appear to be more dolichocephalic than other criminals. In Italy Marro found the foreheads of sexual offenders to be narrow, and in California Drähms found that while murderers had an average cephalic index of 83.5, and thieves of 80.5, that of sexual offenders was 79.
On the other hand, high cheek-bones and broad faces—a condition most usually found associated with brachycephaly—have sometimes been noted as associated with undue or violent sexuality. Marro noted the excess of prominent cheek-bones in sexual offenders, and in America it has been found that unchaste girls tend to have broad faces. (Pedagogical Seminary, December, 1896, pp. 231, 235.)
It will be seen that, when we take a comprehensive view of the facts and considerations involved, it is possible to obtain a more definite and coherent picture of the physical signs of a marked aptitude for detumescence than has hitherto been usually supposed possible. But we also see that while the ensemble of these signs is probably fairly reliable as an index of marked sexuality, the separate signs have no such definite significance, and under some circumstances their significance may even be reversed.
See Biérent, La Puberté; Marro, La Pubertà (and enlarged French translation, La Puberté), and portions of G. S. Hall's Adolescence; also Havelock Ellis, Man and Woman (fourth edition, revised and enlarged).