Man as a Sexually Dimorphic Species

  • Susumu Ohno
Part of the Monographs on Endocrinology book series (ENDOCRINOLOGY, volume 11)


Sexual dimorphism is quite pronounced in two of the three closest relatives of man: gorillas and orangutans. Males are noticeably larger and more powerfully built than females and a few masculine display characteristics are also evident: i.e., large canine teeth. Indeed, they are said to be the practitioners of polygamy, although befitting their intelligence, the practice is said to be quite subtle in that a dominant male manages to placate subordinate males by allowing them to copulate with females in heat when these females are either at the beginning or at the end of estrus, so that while they are receptive to males, they are in no danger of being impregnated. While sexual dimorphism became less obvious in chimpanzees, it became very pronounced once again in man. Mature males, if left unshaven, grow luxuriant beards and the penis and scrotum are extraordinarily conspicuous and large, suggesting that they are not merely for reproductive function but that they once served as a symbolic display of masculine supremacy. The abundant use of phallic symbols by many cultures appears to substantiate this idea. Although the practice of polygynous matings has apparently been uncommon in human history, the inclination to do so appears to have always been there; notice the inclusion of such words as “harem” and “seraglio”, or their equivalents, in human vocabularies. Those human genes awakened at puberty by androgens, must have been whispering to the ears of the sexually mature man that he ought to behave as bulls or lions do. It has been observed that when a rival lion takes over a pride of lionesses, the first royal decree issued is often to kill off the youngest cubs (Bertram, 1975). By so doing, the male has eliminated the progeny of his supplanted rivals and has speeded up the female s return to estrus and hence the first opportunity to propagate his own seeds.


Sexual Dimorphism Mature Male Subordinate Male Royal Decree Dimorphic Species 
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Copyright information

© Springer-Verlag Berlin · Heidelberg 1979

Authors and Affiliations

  • Susumu Ohno
    • 1
  1. 1.Department of Biology, City of HopeNational Medical CenterUSA

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