Development of Sex

• The 23rd pair of chromosmes which determine our biologicall sex. Biological females have two X chromsomes whereas biological males have an X and a Y.
• For 6-8 weeks, male and female embryos develop identically, including their reproductive systems. Eventually, a gene on the Y chromosome called the SRY gene causes testes to develop in males instead of ovaries.
• Once testes develop in males, they produce androgens, which are male sex hormones. They cause the male embryo to start developing a penis instead of a vagina.
• Hormones affect sex development again during puberty. Males start to produce testosterone in greater quantities, and females produce more oestrogen. These hormonal differences cause differences in physical appearance. These are called Secondary Sex Characteristics.
• It is a scientific fact that chromosomes and hormones cause sex differences between males and females. Chromosomes and hormones can be directly observed in males and females, and the differences between males and females have been reliably demonstrated.
• Studies of individuals with androgen insensitivity syndrome also show that hormones influence sex differences. These are XY males who lack receptors for testosterone to attach to, meaning it cannot take effect. Consequently, they develop a feminine appearance, including a vagina