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This paper considers a number of key concepts relevant to biological determinants of human sexuality, including sexual differentiation, brain mechanisms involved in sexual response, the role of sex hormones, and the sexual effects of drugs. The paper concludes with consideration of how little is known about the interaction between biology and culture in shaping human sexuality, and the need for research in this area.
In most species sexual behavior principally serves the purposes of reproduction. In humans, and in some other primates, other purposes for sexual behavior in addition to reproduction have evolved. In the human such purposes have been shaped and influenced by cultural factors, so that human sexuality has been expressed in many different ways, varying across cultures and over history. In spite of these powerful cultural influences, biological factors involved in sexual arousal and response remain fundamental to human sexual experience and need to be taken into account in our attempts to understand and explain the complexities and problems as well as the positive aspects of the human sexual condition. The relevant literature is vast and this paper makes no attempt to provide a comprehensive review; rather, it should be considered an overview of a number of key concepts relevant to understanding the role of biology and its interaction with culture in shaping human sexuality.
SEXUAL DIFFERENTIATION
Biological differentiation into male and female makes sexual reproduction possible. Males have two sex chromosomes, an X and a Y; females have two X chromosomes. Sexual differentiation is determined by the presence or absence of the Y chromosome. If there is no Y chromosome, development is along female lines. A specific part of the Y chromosome, the SRY (sex-determining gene region of the Y chromosome) is responsible for male differentiation (Haqq & Donahoe, 1998). This results in the differentiation of the primitive gonad into a testis rather than an ovary during early fetal development. The resulting testis produces not only testosterone but also Mullerian Inhibiting Factor (MIF) which actively suppresses any further development of those parts of the embryo which would otherwise develop into internal female reproductive organs. The testosterone stimulates development of male genitalia and reproductive organs: It also has organizing effects on the central nervous system which are not well understood but...