Sex Hormones and Behavior in Animals and Man

SEX HORMONES AND BEHAVIOR IN ANIMALS AND MAN WEIERT VELLE* The hormones are important regulators of a variety of physiological processes, including behavior. Among the hormones influencing behavior , gonadal sex hormones have attracted much attention, probably because many of their effects are conspicuous, resulting in more or less marked behavioral differences between the sexes. This fact seems to be generally accepted with regard to animals, but controversy ensues when human behavior is discussed with a view to possible hormonal or other biological influences. Influential psychologists and sociologists have for some time now propagated the view that the evolution of man has reached a stage where biological determinants of behavior play a purely marginal role, if any, and that environmental influences and the process of socialization are decisive for the establishment of interests, attitudes, sex roles, and so on. It was, therefore, perhaps not entirely unexpected that Edward Wilson 's Sociobiology: The New Synthesis [1] came under heavy fire, even from some scientists, apparently because Wilson dares to consider man within the wide context of biological evolution and to discuss possible biological determinants of behavior. On the other hand, it is embarrassing to note reactions of this type [2] in the decennium in which science has seen great triumphs. But, as Bernal pointed out [3], the biological sciences have still not obtained the same degree of immunity against attack as have other disciplines within the natural sciences. Thus in the last century disciplines such as chemistry and physics represented battlefields of violent encounters. Today biology is another such battlefield owing to the fact that man has still not been able to sever the links to magic, and certainly not when questions connected with his own body and mind are concerned. Although this may be the case, it seems nevertheless frightening that *Department of Physiology, Veterinary College of Norway, P.O. Box 8146 Dep., Oslo 1, Norway.© 1982 by The University of Chicago. AU rights reserved 0031-5982/82/2502-0277$0 1 .00 Perspectives in Biology and Medicine, 25,2 · Winter 1982 295 well-educated people, some of whom have reached the highest levels within the scientific community, demonstrate ignorance of, or else simply seem to deny, elementary biological facts [2, 4-9]. Some of these writers and researchers do not completely dismiss available data giving strong support to the significance of biology for human behavior, but they do hold the view that even if behavior differences between the sexes should be in part the result of biological differences between them, research and discussions in this field should not take place because of the risk of supplying racists and antidemocratic elements alibis for their views. From a scientific point of view, attitudes of this type should be strongly refuted for two important reasons. First, they are antiscientific. Second, in the long run they would severely hamper our sense ofjustice, the striving for which must be based on the best possible understanding of our biologically determined potentials and limitations. Only then will it be possible to approach problems in a rational way. This review is concerned mainly with mammals, and an attempt is made to integrate recent results from the fields of endocrinology, brain research, and behavior. A vast amount of literature exists in these fields, and the references given represent only a small fraction of the total. Sex Differentiation In mammals, sex is basically determined by the type of sex chromosomes present in the cells, two X chromosomes resulting in a genetic female, one X and one Y chromosome resulting in a genetic male. In general, the absence of the Y chromosome will result in the development of female genital organs (i.e., female genital sex), although ovaries may be lacking. The presence of the Y chromosome is a prerequisite for the development of the male gonad, which in turn gives rise to testosterone secretion during fetal life. Fetal testosterone secretion normally will lead to development of male genital organs whereby the male genital sex is established. Lack of fetal testosterone secretion, or lack of testosterone receptors, will always result in the establishment of the femalegenital sex, irrespective of the genetic sex. The presence or absence of fetal testosterone, in addition...