1. Biological Influences
On Gender

2. Genes Genes Hormones and Brain Development
genetic sex is determines by inheritance of chromosomes, one from the mother and one from the father.
each gamete only contains one chromosome. Egg – X and Sperm – X/Y
it is the combination of these chromosomes which determines sex. XX- female and XY – male
The combination of these is our genotype, which is expressed to our phenotype
depending on the combination chromosome depends on how the gonads will develop and which sex hormone will be dominant
Money and Ehrhardt – sex of rearing more important than biology, however David Reimer case study of which this theory is based didn’t support this with Bruce becoming Brenda returned to David suggesting genetics are important
The importance of genes in gender development is shown when mutations can affect gender which doesn’t correspond with biological sex
Bernard et al F: looking at 112 male-females and 258 male controls, a large association between a mutation on the androgen receptor(AR) and trans-gender individuals

3. Hormones Genes Hormones and Brain Development
Hormones are specific, either protein or steroid based released via the endocrine or exocrine system
sex hormones affect the gonads pre-nattily, and during puberty
During embryonic development the gonads develop(same for each sex), the SRY gene on the Y chromosomes prevents the default development of ovaries, and turns the gonads into testes
Koopman F: when female mouse embryos had the SRY gene implanted they developed into males
The male hormones-androgens develop external male genitals
Androgen insensitivity syndrome(AIS) is were males cant respond to androgens therfore develop female external genitalia at both the embryonic level and during puberty
Family in the Dominican Republic F: 4 children born with AIS developed external female genitalia
Reiner et al F: 16 M born almost no penis, 2 raised XY, 14 raised XX, at the age of 16 8/14 raised females had reverted back to males

4. Brain Development Genes Hormones and Brain Development
female and male brains differ
Hoag F: XX more social and talkative
Geschwind F: prenatal exposure to high levels of testosterone led to developing a make brain
Quadano F: XX monkeys pre-natitily exposed to high levels of testosterone were more aggressive : control XX monkeys
The importance of brain development being responsible for gender is seen when brain development doesn’t correspond to genetic sex
Pool F: That biological males had more somatostatin neurones than females, and in transsexuals the number of neurones corresponded to their gender choice not their biological sex
Swaab F: Studies brain structures known to differ in males and females, and that 6 trans-females had female brain structures
Zhou F: Trans-females had a similar brain development to normal females in the part of the brain known at the BSTc responsible of sexual behaviour

5. Evolutionary Explanations
Division of labour is responsible for enhancing reproductive success and avoiding starvation
Kuhn et al F: explains why homosapiens survived and Neanderthals because extinct, as both M+F were hunters and their living depended on success of the hunt
Division of labour is based on society and in pre-industrial societies biology was the determining factor
Wood and Eagly F: Men are more physically strong better suited to hunting, whilst females have to be flexible due to childrearing
Wood and Eagly F: support for division based on biology, sampled 100’s societies, men did more physical tasks whilst women took the task of childcare
Zeller F: disproving evidence that the children did most of the childrearing in pre-industrial societies
Adaptive behaviour increases reproductive success, therefore gender role behaviours are linked to reproductive strategies
Williams and Best F:in 30 different cultures the males were more aggressive and females more nurturing
Singh
Schmitt
Buss
David
Fisher
Zahavi
Trivers
Fisher
Zahavi

6. Biosocial approach to Gender Development
interraction of biology and psychology
Money and Ehrhardt
biological factors have a large influence before birth but after it is mainly social factors which are dominant, interacting with the biological to determine a child’s gender identity
in most cases the biological sex matches the gender identity
Intersex children are not obviosly one sex/other
If sex of rearing is decided before the 3rd birthday then social factors will be so influential that the child will accept their assigned gender identity
The 3rd birthday is when gender identity is fully established and cant be changed without psychological harm
Early research supported the biosocial theory, that children would accept their sex of rearing and learn appropiate gender role behaviours
Goldwyn F: the case study of Mrs DW. Had AIS, biologically XY brought up female. When 16 told she was biologically male. Stayed female got married, adopted 2 kids. At no point did she ever feel masculine
Diminican Republic F: 4 siblings all AIS raised as females, and stayed as females

7. Biosocial approach to Gender Development
However biological factors are important, and conflicting evidence shows that they can outwiegh sex of rearing, decreasing the reliability of this theory
Money and Ehrardt F: Case study of David Reimer - penis disfigured and raised as a girl Brenda, felt increasingly unhappy as a girl and always thought he a was a male. Eventually got a sex change back to a male
Reiner F: 16XY AIS. 2 raised XY, 14 raised XX. 8/14 re-assigned themselves XY by 16yrs