Biology in Gender and Sexual Identity Formation


Several studies have been conducted to establish the relationship between biology and the formation of gender and sexual identities. The findings of the studies have shown that gender identity is hard-wired into the brain, and its formation does not depend on psychology or other factors such as environment even though they have considerable influence. The studies have also shown that many people live with gender identity disorders. As a result, instead of identifying themselves with real gender, they choose a different one. For instance, many people are born male but identify themselves as female. In certain cases, they undergo surgery and hormone treatment in order to help them come to terms with their identities. Psychotherapy alone is not sufficient in helping individuals with gender disorders accept their gender and sexual identities. Biology plays a key role in the formation of gender and sexual identities. However, other factors, such as environment and socialization, play a significant role. Biology is the primary factor while environment, psychology, and socialization are secondary factors.


Gender can be defined as the state of being either a male or a female. On the other hand, sexuality can be defined as the capacity of an individual to have erotic experiences and responses (CTS lecture: sexuality 2017). Gender identity has a great impact on personal well-being because it determines an individual’s romantic/sexual inclination (Fausto-Sterling 2012). For instance, if an individual identifies as a man, he will be attracted to women, and if she identifies as a woman, she will be attracted to men. However, some people are attracted to people belonging to their gender, while others are attracted to both genders. Heterosexual, homosexual, lesbian, bisexual, and asexual are terms used to describe people’s sexual inclinations (CTS lecture: gender and feminism 2017). Transgender individuals are people whose gender identities are different from their biological sex. Many theories have been proposed to explain why some people are transgender. However, none of them has offered a solution to the issue that has been studied by researchers for many years.

Biology and Formation of Gender Identity

The formation of gender identity has not yet been completely understood especially in the medical field. Nonetheless, many factors that influence its formation have been proposed and discussed. One such factor is biology. Biological factors that influence the formation of gender and sexual identities include genetic make-up, pre-and post-natal hormone levels, and chromosomes (Fausto-Sterling 2012). The biological theory of gender formation proposes that there is no difference between sex and gender. Therefore, biological sex determines gendered behaviour (CTS lecture: sexuality 2017).


The bodies of men and women contain similar hormones in different quantities. Testosterone is in higher quantities in men than in women. Scientists have established that it influences behaviour before and after birth. In men, it results in the development of male sex organs and facilitates the masculinisation of the brain (Fausto-Sterling 2012). In women, the levels of testosterone are relatively low. The high quantities of this hormone in men explain why they exhibit behaviours such as aggression, competitiveness, and higher sex drive. Testosterone also affects the development of the brain. The sexually dimorphic nucleus is an area of the brain responsible for the aforementioned behaviours because it is larger in males than in females (Fausto-Sterling 2012). The hormone also influences the lateralisation of the brain into left and right hemispheres. Research has found out that women use both hemispheres while men use the left hemisphere in accomplishing most tasks.

Congenital adrenal hyperplasia (CAH) is a condition caused by gene mutations that alter the development of sex characteristics (Saraswat, Weinand & Safer 2015). Girls with this disease have excessive androgens in their bodies. Therefore, they display more gender-stereotypic male behaviours that contradict their sexuality. They have external genitalia even though they identify themselves as females. That is proof enough that gender is determined genetically and not anatomically (Saraswat, Weinand & Safer 2015). Many girls with CAH undergo surgery to transform their external genitalia in order to look female. However, they still exhibit masculine traits such as aggression and competitiveness because of the high levels of androgens in their bodies.


A chromosome is a structure that contains genetic material called genes. Humans contain 23 pairs of chromosomes that carry heredity material that determines biological sex. Each pair of chromosomes governs a specific aspect of development. The 23rd chromosome pair is responsible for determining biological sex (Fausto-Sterling 2012). Chromosomes are represented by the letters X and Y. Males are XY, while females are XX. The SRY gene is the sex-determining region of the Y chromosome (Saraswat, Weinand & Safer 2015). Its presence results in the development of male sex organs while its absence results in the development of ovaries. In certain cases, the Y chromosome lacks the SRY gene. In that case, the foetus develops as a girl even though its chromosomes are XY. In other cases, there is an additional X on the sex-determining chromosome leading to an XXY arrangement. The additional X chromosome leads to the development of traits that cause gender confusion.

Social Factors Influencing Formation of Gender Identity

Studies have shown that social environment play a key role in influencing the formation of gender identity (CTS lecture: sexuality 2017). The interests, behaviours, attitudes, and preferences that children exhibit originate from the influence of parents and authority figures (Saraswat, Weinand & Safer 2015). The influence is primarily based on societal sexual stereotypes that define what it means to be either male or female. Many children are influenced by the teachings of their parents and the behaviours of their peers. For instance, children who are taught to avoid certain actions and behaviours because they are inappropriate for their gender internalize the teachings and adopt them as they grow into adulthood.

Sexual Identity/Orientation

Sexual orientation refers to the sexual inclination towards one or both genders (CTS lecture: sexuality 2017). As mentioned earlier, heterosexual, homosexual, lesbian, bisexual, and asexual are terms used to describe the various forms of sexual orientation (CTS lecture: gender and feminism 2017). Science supports the argument that certain sexual behaviours such as homosexuality are biological based on research that documents same-sex sexual behaviour in all cultures and sexual animals. For example, studies have identified same-sex sexual behaviour among sheep and penguins (CTS lecture: gender and feminism 2017). This implies that sexual identity is neither psychological nor social. It is biological. The fact that sexuality varies across the cultures and through time is the proof that sexuality is a social construct. In that regard, there is no significant biological influence on sexuality. This argument explains why many countries have laws against homosexuality (CTS lecture: gender and feminism 2017). Trans-gendered people develop gender identities that are contrary to their physical gender.

The early fixation hypothesis suggests that sexual identity is predominantly determined by the masculinisation of the brain. Sexual identity is largely determined by hormone exposure during prenatal development (Saraswat, Weinand & Safer 2015). Differences in brain structures and cognitive processing between homosexual and heterosexual males can be attributed to variances in the exposure to hormones during the development of the foetus. Studies have shown that other than biology, factors such as environment influence the formation of gender and sexual identities (Saraswat, Weinand & Safer 2015). Temperament determines the activities and behaviours that children prefer. For instance, some boys will prefer to play games that girls play while some girls will prefer to play the games that boys play. Temperament is determined by biological variables. This will make the children feel different from their peers and develop psychological arousal that gradually transforms into sexual arousal. This proposed theory has not yet been proven scientifically.


In the past three decades, researchers have studied the relationship between biology and gender/sexual identity. Several studies have revealed that biology plays a significant role in determining gender identity and sexual orientation. Gender/sexual identity formation is determined by two main biological factors namely, hormones and chromosomes. The release of testosterone in the womb stimulates the development of male sex organs and behaviours such as aggression and competitiveness. Chromosomes are units of heredity that determine a baby’s sex. Biological sex is determined chromosomes. Males have XY chromosomes while females have XX chromosomes. Biology plays a significant role in the formation of gender and sexual identities. However, environment and social factors also influence their formation. Gender and sexual identities can be attributed to a combination of biology (genetics) and environment.


CTS lecture: gender and feminism 2017, PowerPoint slides.

CTS lecture: sexuality 2017, PowerPoint slides.

Fausto-Sterling, A 2012, Sex/gender: biology in a social world, Routledge, New York.

Saraswat, A, Weinand, J, & Safer, J 2015, ‘Evidence supporting the biologic nature of gender identity’, Endocrine Practice, vol. 21, no. 2, pp. 199-204.

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