One biological influence on gender is the role of genes in gender development. Everybody has 23 pairs of chromosomes in their body which contain genes. Each of these chromosomes carries hundreds of genes containing instructions about physical and behavioural characteristics, such as eye colour and predisposition to certain mental illnesses. One pair of these chromosomes is called the sex chromosomes as they code for which sex you are. Males are XY and females are XX. It is the XY in a male that distinguishes between the two sexes. Chromosomes are found to have an impact on a person’s external and internal genitalia. There is usually a direct link between an individual’s chromosomal sex and their external genitalia and internal genitalia.
At the start of prenatal development all individuals start out the same. A few weeks after conception both male and female embryos have external genitalia that look essentially feminine. Then, around 3 months into the pregnancy if it is to develop as a male, the testes will begin to produce testosterone which causes the external male genitalia to develop. Genetic transmission explains how individuals acquire their sex and it may also explain some aspects of gender (whether a person feels male or female) because of the link between genes and genitalia and hormones.
Even though chromosomes initially determine a person’s sex, most gender development is actually governed by hormones. The development of genitalia and the development of the brain is affected by hormone influences. The role of hormones in gender development can be seen by studying individuals who have been exposed prenatally to abnormal hormone levels.
Male brains are different from female brains in many ways. GESCHWIND ET AL were the first to suggest that such sex differences may be caused by the effects of testosterone levels on the developing brain. Hormones can also be used to explain the differences between sexes with brain development. Male brains are normally exposed prenatally to more testosterone than females. When this is not the case and girls are exposed to high levels of testosterone then they will often develop a “masculine” brain.
The effects of testosterone on the brain have been confirmed by animal studies. QUADANGO ET AL (1977) found that female monkeys who were deliberately exposed to testosterone during prenatal development engaged in more rough and tumble play and were more aggressive, suggesting the importance of hormones.
YOUNG (1966) gave male hormones to female mice and vice versa and found that there was a reversal in normal gender related behaviour.
Obvious and subtle differences between humans and animals in terms of out physiological, anatomy and metabolism make it difficult to apply data derived from animal studies to human conditions. However animal studies provide the opportunity to gain more information as with a topic like this, humans cannot be used for conducting research.
There are many studies that support the effect of hormones on gender development. For example DEADY ET AL found that high levels of salivary testosterone were linked with low scores on measures of maternal personality in biological females. This suggests that testosterone makes the brain more masculine. Although some suggest that the testosterone may affect the levels of other hormones which many affect maternal personality. Therefore the relationship may not be causal.
REINER suggested that our biology plays a vital role in determining out gender development. He studied 16 genetic males born with almost no penis. Two were raised as males and the remaining 14 were raised as females. Of these 14, eight has reassigned themselves as males by the age of 16.
KNICKMEYER ET AL (2005) studied the foetal testosterone levels in amniotic fluid in 35 males and 23 females. When their mothers were questioned about their development at 3 years old, foetal testosterone had a negative correlation with quality of social relationships and positively correlated with restricted interests in males. This suggests that testosterone may negatively affect social relationships and so may have an impact on the male gender role.
A methodological criticism is that much of the research into the impact of hormones on gender development has been based on the use of case studies. Case studies are often unique cases and are based on only one individual. This suggests that the research cannot be generalised to the wider population.
An over-emphasis on biological influences in determining behaviour could be a problem for many reasons. Firstly it is a reductionist approach as it does not account for social and cultural factors. There is also a tendency to assume that biologically determined characteristics are hard-wired and cannot easily be changed which research into hormonal influences has shown is not necessarily true.
However, not all the evidence is in favour of the role of genes in gender development. For example, COLLER ET AL (1995) reviewed studies into biology and gender and found inconsistent findings. This suggests that research into the role of genetics is unreliable and more research needs to be done. If findings are inconsistent then there must be other factors involved in gender development such as nurture.
However, there is evidence that biological sex is not the main factor in gender development. Money et al claimed that the sex that the child is reared as is more important than their chromosomal sex. His theory was disputed by the case of David Reimer who was genetically male but was raised as a girl. Despite being given hormone treatments in order to develop an outwardly female appearance, Reimer became isolated and depressed and reverted back to being male immediately after finding out his true sex. This suggests that chromosomal sex is crucial to gender development, conflicting with Money’s claim.
DIAMOND believed that humans, like animals are born with an instinctive set of behaviours to act like male or female. Pregnant rats were injected with testosterone and thus the female off springs had genitals which were male like in appearance and they tried to mate with other female rates.
Biological determinism: effects of nurture were attenuated eventually by hormones (nature). This suggests that our behaviour and mental experiences related to gender are not changeable, with the hold of genetics over our development being too powerful.
This research has real-world applications. For a long time, the Olympic Committee ruled that people with XX chromosomes must compete in female events while people with XY chromosomes must compete in male events. However, due research on gender development there was a ruling in 1991 that genetic sex would no longer determine entry into the Olympics.
Another problem is that much of the research in this area is done to people with intersex conditions. The results of these studies should therefore only be applied to the general population with caution as they may only be applicable to people with intersex conditions. Research into such personal and potentially painful issues has the potential to cause psychological harm, an ethical issue which should be avoided.