The Role of Chromosomes And Hormones In Gender

Man up! Be more ladylike! You've probably heard these phrases a million times telling us how to be more masculine or feminine, but have you ever considered that sex and gender is largely influenced by biological factors such as chromosomes and hormones? In this article, we will explore how these factors influence sex and gender.

The role of chromosomes in sex and gender

Let's begin with a quick recap on chromosomes and genetics. Chromosomes are made of DNA, whilst genes are short sections of DNA that determine the characteristics of living things. Chromosomes come in pairs. There are 23 pairs in the human body (so 46 chromosomes overall). The last pair of chromosomes is what influences our biological sex. In females the pair is XX, and for males it is XY.

All normal eggs produced in the ovaries have an X chromosome. Half of the sperm have an X chromosome and the other half have a Y chromosome. The sex of a baby is thus determined by the sperm that fertilises the egg cell.

XX and XY chromosome, Yzabelle Bostyn - StudySmarter Originals

If the sperm carries X chromosomes, the baby will be a girl. If it carries Y chromosomes, it will be a boy. This is because the Y chromosome carries a gene called the 'sex-determining region Y' or SRY. The SRY gene causes tests to develop in an XY embryo. These then produce androgens: male sex hormones. Androgens cause the embryo to become a male, so without them, the baby develops as a female.

The role of hormones in sex and gender

Chromosomes initially determine a person's sex, but most biological sex development comes about as a result of hormones. In the womb, hormones encourage the development of the brain and reproductive organs. Then, during adolescence, a burst of hormones induces the development of secondary sexual characteristics such as pubic hair and breast development. Males and females have the same types of hormones but in different concentrations.

Testosterone

Male developmental hormones are known as androgens, the most prominent of which is testosterone. Testosterone controls the development of male sex organs and begins to be produced at around eight weeks of fetal development.

Many psychological studies have researched the behavioral effects of testosterone, the most notable of which is aggression. For example, Van de Poll et al. (1988) demonstrated that female rats became more aggressive when injected with testosterone.

Estrogen

Estrogen is the hormone that influences the development of female sex organs and menstruation.

Besides physical changes, the hormone can cause mood changes in women during menstruation, including increased irritability and emotionality. If these effects become severe enough to be considered a diagnosable disorder, they can be referred to as pre-menstrual tension (PMT) or pre-menstrual syndrome (PMS).

Oxytocin

Although both men and women produce oxytocin, women produce it in much larger quantities than men. It plays a crucial role in female reproductive function, including childbirth. Oxytocin stimulates lactation for breastfeeding. It also reduces the stress hormone, cortisol, and facilitates bonding, especially during labour and after childbirth. That is why this hormone is often referred to as the 'love hormone.'

Some have used the fact that men produce less oxytocin to support stereotypes that men are less romantic and interested in love. However, research has shown that men and women produce the hormone in equal amounts during activities such as kissing and sex.

Oxytocin stimulates lactation for breastfeeding

How can we evaluate the role of hormones and chromosomes in sex and gender?

Many psychologists have conducted research into the role of hormones and chromosomes in sex and gender. Many have also evaluated and criticized this approach to explaining sex and gender. Below w will outline the role of chromosomes and hormones in sex and gender.

Pre-menstrual syndrome supports stereotypical views of women

The suggestion that women become emotional and irritable during their menstrual cycle due to hormones gives a biological explanation to women's feelings and moods. This could allow people to dismiss women's emotions as merely the result of biology. Therefore, many authors such as Rodin (1992) have argued that the medicalization of PMS supports patriarchal views.

Contradictory evidence

In a double-blind study, Tricker et al. (1996) gave 43 times an injection of testosterone or a placebo. Over a ten-week period, no significant differences were observed between the experimental condition (testosterone) and the control group (placebo). This suggests that hormones do not significantly influence behavior.

Oversimplified and reductionist

If biology was the only influence on behavior, we would expect a lot more differences between male and female behavior. For example, Maccoby and Jacklin (1974) found that there were significantly more differences within genders than between them.

Learning theory

Approaches such as behaviorism and social learning cite environmental factors as the driving force of gender-related behavior. This could explain cross-cultural differences in cultural behavior and transgender individuals.

The psychodynamic approach

This approach suggests that gender is a result of early childhood experiences. For example, Ovesey and Person (1973) suggested that males who exhibit female characteristics do so because of separation anxiety in early childhood. This anxiety they experienced makes them want to identify with their mother.

Cognitive explanations

The cognitive approach suggests that biological explanations of sex and gender oversimplify a complex concept. It suggests that thought processes influence gender development. But although these could be linked to the changing state of the developing brain, it remains clear that gender is not sufficiently explained through biology.

The failure to consider these alternative influences on gender and sex makes the biological approach reductionist, as it reduces gender and sex down to one factor: biology.

Research evidence

Below are a few studies which explore the role of chromosomes and hormones in gender.

Dabbs et al (1995)

Dabbs and his colleagues studied the levels of testosterone in the prison population and found that offenders with high levels of testosterone were more likely to have committed violent or sexually motivated crimes. These suggests that hormones are linked to behavior.

The Bruce Reimer case study

Brian and Bruce Reimer were twin boys born in Canada in 1965. Following a botched circumcision, Bruce was left without a penis.

Bruce's parents were directed to John Money, a psychologist pioneering his 'gender neutrality' theory, which suggests that gender is determined more by the environment rather than biological factors.

As a result, Money encouraged the Reimers to raise their son as a girl. 'Bruce', known as Brenda, played with dolls and wore girls' clothes. Although Money wrote extensively of the 'success' of this case, Bruce suffered from psychological problems, leading their parents to disclose the truth of their identity. Following this, Bruce returned to life as a male, 'David'. Unfortunately, David suffered deeply as a result of their hidden identity and committed suicide in 2004.

This case study suggests that there is some biological basis to sex and gender because despite being raised socially as a girl, David still felt uncomfortable in this gender, probably as a result of the truth of his biological sex.

What determines gender?, Yzabelle Bostyn - StudySmarter Originals (Made in Canva)

Van Goozen et al. (1995)

Van Goozen studied transgender individuals who were undergoing hormone therapy as part of their transition. This means they were injected with hormones of the opposite sex. Transgender women (men transitioning to women) showed a decrease in aggression and visuo-spatial skills, whilst the opposite was true for transgender men (women transitioning to men). This suggests that hormones influence the behavior of men and women differently.