If there is one thing people like to feel certain about it is whether a newborn child is a girl or a boy. Until we have that piece of information it is difficult to think about a baby as a person at all and we do not know how to treat ‘it’. How people think about a new human being immediately depends on the sex of the baby. The incredibly important decision about sex is made, in most cases, by a midwife or doctor taking a quick look at the newly arrived person to see if they have a penis or a vagina.

Having either a penis or a vagina is usually seen as the fundamental difference between sexes. Other parts of the reproductive system, such

as wombs, ovaries, testes and scrotums, also supposedly separate women (female) from men (male). In addition, there are arguments about sex differences in skeletons, amounts of fat, muscles, ribs, bodily hair and physical strength. Men and women apparently also differ chromosomally and, to a slight degree, hormonally (Hird, 2004; Oudshoorn, 1994). But what you can see on the outside does not always match up with the other indicators of sex and there is a lot more biological variation than the simple categories ‘male’ and ‘female’ describe. To understand this it helps to begin by looking at how present scientific accounts of sex have developed.