Sociologists are particularly interested in gender identity and how (or if) it determines gender roles. Gender identity appears to form very early in life and is most likely irreversible by age 4. Although the exact causes of gender identity remain unknown, biological, psychological, and social variables clearly influence the process. Genetics, prenatal and postnatal hormones, differences in the brain and the reproductive organs, and socialization all interact to mold a person's gender identity.
Biological influences on gender identity
Sexual differentiation, which encompasses the physiological processes whereby females become females and males become males, begins prenatally. The differences brought about by physiological processes ultimately interact with social‐learning influences postpartum (after birth) to establish firmly a person's gender identity.
Genetics is the scientific study of heredity. Geneticists study genes, the basic units of heredity that determine inherited characteristics. Genes are composed of deoxyribonucleic acid (DNA). Three primary patterns of genetic transmission are dominant (expressed trait that is visibly apparent), recessive (unexpressed trait that is not visibly apparent), and sex‐linked inheritance (trait carried on one of the sex chromosomes, usually X).
Determination of an embryo's chromosomal sex is genetic, occurring at conception. This process involves chromosomes, which are the biological structures containing biological “blueprints,” or genes. The egg, or ovum, always carries an X chromosome, and the sperm carries either a Y or an X chromosome. A zygote is the product of conception: a fertilized egg. A male zygote (XY) is the product of the fusion of an egg with a sperm carrying a Y chromosome; a female zygote (XX), the product of the fusion of an egg with a sperm carrying an X chromosome. The X chromosome provides valuable genetic material essential to life and health. The Y chromosome is smaller than the X, and carries little more than directions for producing a male.
Psychological and social influences on gender identity
Gender identity is ultimately derived from both chromosomal makeup and physical appearance, but this does not mean that psychosocial influences are missing. Socialization, or the process whereby a child learns the norms and roles that society has created for his or her gender, plays a significant role in the establishment of her or his sense of femaleness or maleness. If a child learns she is a female and is raised as a female, the child believes she is female; if told he is a male and raised as a male, the child believes he is male.
Beginning at birth, most parents treat their children according to the child's gender as determined by the appearance of their genitals. Parents even handle their baby girls less aggressively than their baby boys. Children quickly develop a clear understanding that they are either female or male, as well as a strong desire to adopt gender‐appropriate mannerisms and behaviors. This normally occurs within two years, according to many authorities. In short, biology “sets the stage,” but children's interactions with the social environment actually determine the nature of gender identity.
Some people are unable to merge the biological, psychological, and social sides of their gender. They suffer gender dysphoria, or emotional confusion and pain over their gender identity. Specifically, some believe they were born into the wrong‐gender body, that their internal sense of gender is inconsistent with their external sexual biology. This condition is termed transsexualism. Transsexuals may desire to be rid of their primary and secondary sexual structures and acquire those of the other sex by undergoing sex‐reassignment surgery. Transsexuals should not be confused with transvestites, who enjoy wearing the clothing of the other gender.