CONCEPTS IN BIOLOGY
PART VI. PHYSIOLOGICAL PROCESSES
27. Human Reproduction, Sex, and Sexuality
27.2. The Sexuality Spectrum
Although we tend to think of our species as being clearly divided into two genders, male and female, sexuality really is a spectrum that includes anatomical and behavioral components. Both anatomy and behavior are the result of a complex interplay between genetic and developmental processes that are influenced by environmental factors.
Hermaphrodites are organisms that have both ovaries and testes in the same body. This condition is extremely rare in humans. However, incidences of partial development of the genitalia (sex organs) of both sexes in one individual may be more frequent than most people realize. About 1% of births show some level of ambiguity related to sexual anatomy. These people are referred to as intersexual because their sexual anatomy is not clearly male or female. Sometimes, this abnormal development occurs because the hormone levels are out of balance at critical times in the development of the embryo. This hormonal imbalance also may be related to an abnormal number of sex-determining chromosomes, or it may be the result of abnormal functioning of the endocrine glands.
When children with abnormal combinations of sex organs are born, they are usually assessed by a physician in consultation with the parents to determine which sexual structures should be retained or surgically reconstructed. The physician might also decide that hormone therapy might be a more successful treatment. These decisions are not made easily because they involve children who have not fully developed their sexual nature. An increasingly vocal group advocates that children who are diagnosed with this condition not be surgically “corrected” as infants, recommending that, if the parents can cope with the unusual genitalia, they allow the child to grow older without having the surgery. They believe that people should choose for themselves once they are more mature. However, few long-term studies have examined whether delaying reconstructive surgery presents fewer social and psychological adjustment issues than performing reconstructive surgery in children.
A person’s gender is his or her sexual identity based on anatomy. However, a person also has a psychological gender. More and more frequently, we are becoming aware of individuals whose physical gender does not match their psychological gender. These individuals are often referred to as transgender persons. A male with normal male sex organs may “feel” like a female. The same situation may occur with structurally female individuals. Because some of these individuals might dress as a member of the opposite sex, they are sometimes called cross-dressers or transvestites. Some of these individuals may dress as the other sex in private but dress and behave in public appropriate to their anatomical sex. Others completely change their public and private behaviors to reflect their inner desire to function as the other sex. A male may dress as a female, work in a traditionally female occupation, and make social contacts as a female. Tremendous psychological and emotional pressures develop from this condition. Frequently, many of these individuals choose to undergo gender reassignment surgery—a sex-change operation. Their goal is to interact with society without being detected as having been a different gender at one time. This surgery and the follow-up hormonal treatment can cost tens of thousands of dollars and take several years.
Homosexuality is a condition in which a person desires romantic and sexual relationships with members of their own sex. However, it is a complex behavioral pattern with many degrees of expression. Some individuals are exclusively homosexual, while others can be considered bisexual because they form sexual relationships with either males or females. Some are transgender individuals while others clearly accept their biological sex but prefer relationships with others of the same sex. However, it is becoming clear that sexual orientation in most cases is not a simple choice or a learned behavior. There appear to be differences in brain function and genetic makeup that are important. For example, certain studies suggest that genetic regions on chromosomes 7, 8, and 10 may influence homosexuality. Some regions on chromosome 7 and 8 have been linked with male sexual orientation, regardless of whether the male receives the chromosomes from his mother or father. The regions on chromosome 10 appear to be linked with male sexual orientation only if they were inherited from the mother.
Sexuality ranges from strongly heterosexual to strongly homosexual. Human sexual orientation is a complex trait, and evidence suggests that there is no one gene that determines where a person falls on the sexuality spectrum. It is most likely a combination of various genes acting together and interacting with environmental factors (figure 27.2).
FIGURE 27.2. The Sexuality Spectrum
A person’s sexuality involves both anatomical and psychological components. This figure shows how behavioral and physical sexual characteristics interrelate. At the ends of the behavioral spectrum, individuals can be strongly heterosexual or strongly homosexual, or (in the center) they might be bisexual, attracted to both sexes. On the anatomical spectrum they may be clearly anatomically male or female or be intersexual.
27.2. CONCEPT REVIEW
3. What does the term intersexual mean? How does it differ from the term transgender?
4. How is homosexuality different from transgender behavior?