A very remarkable phenomenon in the course of human evolution has been the =diminution in the hairy covering of the body=. As compared with the other mammalia, especially those most nearly allied to man--the anthropoid apes--man is relatively bald. This baldness has been =gradually acquired=, and seems likely to progress further in the future. Numerous hypotheses have been propounded regarding the purpose and true cause of this progressive atrophy of the hairy covering which originally extended over the entire surface of the body. The effect of tropical climate will not suffice to account for the change, for in the tropics the hairy covering is useful for a covering against the rays of the sun--witness the thick hairy coat of the tropical apes. More apt is the idea of sexual selection, advanced by Darwin in explanation of the loss of hair. According to this theory, the comparatively balder women were preferred by the men to those with a thicker covering of hair. Helbig raises the objection that primitive man in sexual intercourse would observe only the genital organs and the parts in their immediate neighbourhood. Yet in this region the sexually mature woman has retained a portion of the hairy covering of the body. We must therefore, in order to rescue the idea of sexual selection as an explanation of the increasing baldness of the human race, assume that primitive man had cultivated æsthetic tastes, and was not an extremely sensual person, and that in his choice of a partner he would be guided by the appearance of the woman’s entire body. This, however, is a very questionable assumption. Very doubtful also is the suggested connexion between largely developed dentition and the baldness of the skin (Helbig). More apposite is W. Bölsche’s view that the atrophy of the human hairy covering is related to the adoption of an =artificial covering=. Since that time the thick hairy covering of the skin was felt to be burdensome, since it hindered perspiration beneath the clothing, and also favoured the harbouring of parasites, fleas, lice, etc., which play so large a part in the annoyance of all hair-covered mammals. In these circumstances bareness of skin became an ideal to primitive man. By rubbing away the hair beneath the clothes, by cutting it short, and by pulling it out by the roots, an artificial baldness was produced; this then became an ideal of beauty. Thus it happened in the choice of a partner that those individuals less hairy than others were preferred, and thus gradually by this process of sexual selection the race became continually less hairy, until ultimately the relative baldness of the present day was attained.