chromosomes & hormones

• The chromosomes involved in determining gender are the 32rd pair. XX for females but XY for males.
• The Y chromosome determines male sex because it carries the SRY gene, which triggers the synthesis of androgens (male hormones) without which the embryo develops into a female.
• there are 3 hormones involved in developing sex and gender: testosterone, oestrogen and oxytocin
• Testosterone is the male sex hormone which determines male primary and secondary characteristics.
• Nanne van der Poll et al (1988) showed female rats who’d been injected with testosterone became more physically and sexually aggressive, proving there is a link between testosterone and aggression.
• Oestrogen is the female hormone which determines female primary and secondary characteristics and can cause increased irritability during the menstrual cycle.
• Oxytocin is also a female hormone which causes the uterus to contract in labour and produce milk for breastfeeding. It’s known as the love hormone because it promotes attachment between mother and infant.
• SUPPORT for the role of chromosomes and hormones in sex and gender comes from the David Reimer case study. After a botched circumcision when he was around 7 months old, a psychiatrist (Dr Money) convinced his parents to raise him instead as a girl “Brenda”. However, when he reached puberty and the hormones in his body were causing the expected male changes, they were forced to tell him the truth and he immediately went back to living as a man.
• In a double-blind study by Tricker et al (1996), 43 males were given either a weekly testosterone injection or a placebo. No significant differences in aggression were found.
• Slabbekoorn et al (1995) demonstrates that sex hormones had no consistent effect on gender neutral behaviour.
• Many studies of biological factors in gender involve small samples of unusual people or conducted on animals, limiting the extent to which meaningful generalisations can be made, like the David Reimer case.
•  Explanations suggesting gender development is down to genes and hormones are accused of being reductionist and ignoring other plausible explanations.