The Biological Explanation of Gender

Evolutionary theory offers a biological explanation for the consistent differences between females and males. Human beings have evolved so that males and females possess different chromosomes that trigger the production of different levels of certain hormones.

Hormonal differences between the sexes lead to differences in behaviour. This allows males and females to perform different roles in reproduction, thus ensuring the survival of their genes and their species

Women have evolved physiologically, anatomically and psychologically to be the carers of their young, whilst males have evolved in a similar way to be the main providers for the mothers and her young.

Each cell in the human body contains 46 chromosomes arranged as 23 pairs. Twenty-two of these are matched and are the same in males and females. However, the 23rd pair differs between the sexes. Females have two similar chromosomes, known as ** chromosomes,and males have two dissimilar chromosomes, known as XY chromosomes.

An individual's sex is determined by the chromosomal make up of the sperm that fertilises the egg. If the sperm carries an X chromosome, the embryo will be female. If it carries a Y chromosome, the embryo will be male.

In the first weeks after conception, a male and female embryo appear the same. There is no difference in their gonads. At six weeks, however, the gonads begin to develop differently . A gene on the Y chromosome is responsible for triggering the events that transform the male embryo's gonads into testes. In the absence of the gene, the gonads will automatically develop into ovaries.

Once the testes and ovaries begin to develop, they begin to release their own sex hormones. Male hormones are known as androgens. Female hormoes are mainly oestrogens.

Biological explanations state that sex hormones have an effect on the pre-natal develovpment of the brain. Since male and female foetuses produce different amounts of certain hormones, this could imply that the male and female brain develop differently. Research does show that there are key structural and functional differences in the brains of males and females.

This could account for the psychological differences between the sexes (Maccoby and Jacklin, 1974). For example, baby boys show more interest in mechanical objects, while baby girls show more interest in faces (Connellan et al, 2000). Since such differences occur in the irst few months of life, they are unlikely to be the result of socialisation.

Involve the hypothalamus. It has two specific regions - the BST and the SDN-POA, which are larger in adult heterosexual males than adult heterosexual women.

One biological theory is that these differences in brain structure may relate to the differences in male and female sexual behaviour (for example, women tend to be more coy, while males are more promiscuous).

Sex differences have also been found in the strucutre of the cerebral hemispheres(two halves of the brain which specialise in different functions - left half, language, right half, spatial ability) of the brain.

Biological theorists suggest that this could explain the consistent finding that females develop superior language, emotional and fine motor skills, whilst males develop superior visual-spatial and mathematical skills.

Females with adrenogenital syndrome (a set of symptoms associated with excessive secretion of adrenal hormones) have ** chromosomes, but are exposed to excessive androgens in the womb from a malfunctioning of the adrenal glands.

Despite having male-like genitals, these babies are normally identified as females at birth and raised as such. Although studies have shown, a significant number of these girls later identify themselves as 'tomboys' (Money and Ehrhardt, 1972). These findings suggest that hormones have a pre-natal effect on the brain which later affects gender-related behaviour.

Sex hormones may not just have an effect on brain organisation in the womb. Hormones are produced throughout an individual's life time and so may continue to affect behaviour. For example, there is evidence that boys experience a surge in testosterone around four and this is responsible for the fact that boys are more active and boisterous than girls at this stage of development.

• Investigated the effects of sex hormones on adult behaviour
• They used the experimental method to study transsexuals of both sexes who were undergoing hormone treatment, that were being injected with hormones of the opposite sex. They were given a range of tests to complete before treatment and then three months later
• Male-to-female ttranssexuals show decreases in aggression and visual-spatial skills but increases in verbal fluency. Female-to-male showed the opposite.
• This suggests that sex hormones do affect gender-related behaviours
• This was not a controlled experiment, so the changes may have been due to other uncontrolled variables, such as the transsexual's own expectations.

Slabbekoorn et al (1999) question these findings, and demonstrated that sex hormones do not have consistent effects on gender-related behaviour. Critics also argue that we should be careful about generalising from such an unusual sample. 

Hormones may not be having the same effect on a typical population of men and women. Additionally, there is always a debate about how we reliably measure aggression, verbal fluency and visual-spatial ability.

Hampson and Kimura (1988) - investigated the fluctuations in oestrogen and progesterone that occur during women's menstrual cycles. They found when these hormone levels were high, women performed better in fine motor task and worse in visual-spatial tasks compared to when levels were low

Galligani et al (1996) - investigated the effects of steroids which are known to increase levels of testosterone. Using a variety of measures, they found that male athletes who used steroids showed higher levels of aggression than a control group

Waber (1976) - investigated the effects of sex hormones in puberty of verbal ability. She found late maturing boys had better verbal ability than boys who were early developers.

We have considered a range of evidence suggesting that chromosomes and, in turn, hormones affect gender development. However, it is difficult to establish cause and effect in psychology and gender in no exception. 

It may be easier to establish the real effects of chromosomes if researchers could manipulate them in some way - atypical chromosome patterns do occur naturally. Although it can potentially cause difficulties for people born with these disorders, it does offer useful insight into gender development.

People with Turner's syndrome identify themselves as female and have similar interests and behaviours to biologically normal females.

This suggests that a feminine gender identity can develop in the absence of ovaries and the oestrogens they produce.

Atypical chromosome pattern: XO

Frequency: 1 in 2,000 births

Sex Identity: Female

Physical Characteristics: No ovaries, do not menstruate at puberty and are sterile. Don't get breasts. Unusually short stature. Short, webbed neck. Low set ears.

Psychological characteristics: Higher than average verbal ability, lower than average spatial ability,visual memory and mathematical skills. Difficulties in relating to peers

Individuals with Klinefelter's have the ** combination associated with associated with females, yet anatomically they are male. Theis shows the importance of the Y chromosome in triggering formation of male structures.

Atypical chromosome pattern: **Y

Freqency: 1 in 500 births

Sex Identity: Undescended testes and undersized penises. Some breast develpment at puberty and 'rounding' of body contours. Little body hair. Long limbs, clumsy.

Psychological characteristics: Lack of interest in sex, tend to be passive, shy and lacking in ambition, poor language skills and reading ability, poor judgement and handle stress badly, higher than normal level of gender identity confusion

• Critics often question the evidence of the biological approach. A lot of the research on the effects of hormones is demonstrated on animals, which may not be generalisable on humans. Do animals really have a sense of being masculine and feminine like humans do? Even when humans are studied, they are often unusual cases which do not represent typical gender development.
•  A number of findings have not been replicated. This questions the reliability of an approach which claims to be objective
• It would follow that in cases of atypical gender development, there should be evidence of chromosomal or hormonal abnormalities, but this does not always appear to be the case
• As we move through the generations, more individuals from both sexes are identifying themselves as androgynous rather than strictly masculine or feminine. However, these have them same patterns of chromosomes and hormone production as their ancestors. This would indicate that society and culture are having an effect as they do change over time.

• SLT would dispute the fact that gender is a product of nature. If men are biologically similar and women are, why do the two sexes not behave in exactly the same way? SLT would argue that men and women display a range of gender-related behaviour depending on their unique learning experiences. This would also explain why different cultures seem to have different gender roles, and why men and women's typical behaviours have changed over time. 
• The cognitive approach would argue the biological approach is too reductionist as they attempt to explain complex behaviours simply in terms of chromosomes and hormones. The cognitive approach qould argue we have to understand the thought processes between gender development. Although thinking is more abstract and more difficult to study, it doesn't mean it should be avoided. Cognitive would also accuse the biological explanations as being too deterministic. The approach would question the idea that we are 'at the mercy' of our biolgy and would argue we have some choice in how with think of our gender and behave.
• The psychodynamic approach would agree there are innate elements to gender development and they are related to the sexual differences between males and females. But it would also emphasise the importance of childhood experiences and familial relationships in gender development. The approach would object to the biological idea that gender develops in isolation from society.