In the beginning, the baby in the womb possesses the physical characteristics of both female and male children. For the first seven to ten weeks of life, everyone has female and male internal sex organs. Then, at round about week ten, one set of the organs predominates over the other and the baby takes on the physical sex of either girl or boy.
In most cases, this comes about quite simply. At the point of conception, the chromosome structure of the baby is decided: if the chromosomes are XX, then the baby is genetically female; if they are XY, then the baby is genetically male. It is the Y chromosome that instructs the babies body to produce chemicals called androgens, which diminish the female sex organs and stimulate growth of the male ones. So, at about twelve weeks old, the baby has either developed ovaries or testes: it is, at that point, biologically either a girl or a boy. And as the baby develops, so external sex organs develop to match the internal ones, and baby girls develop a womb, vagina and clitoris, while baby boys develop testes, penis, scrotum and prostate gland.
It all sounds so simple: and in 99 percent of cases, it is just as simple as that. But not always. Some babies are conceived with a syndrome called "Klinefelter`s Syndrome", in which their genetic structure is XXY A surprisingly high number of people - perhaps one in 400 - have this ambiguous genetic sexuality. As well, about one in 2,500 girls is born with "Turner's Syndrome", in which one X chromosome is absent or imperfect, so that the ovaries do not develop, although the external sex organs are quite normal.
The development of male external sex organs depends on the baby's body producing male hormones, especially one called testosterone. Some babies who are genetically male, therefore, may suffer from a syndrome known as "testicular feminisationn" in which, although their body produces normal amounts of testosterone, it does not trigger off the correct development of external sex organs: such children will be genetically male, but their appearance at birth will be female, and their genetic sex may not be discovered until they fail to menstruate at puberty.
Other babies which are genetically female may have "congenital adrenal hyperplasia", a syndrome in which their adrenal glands produce large amounts of hormones similar to testosterone. At birth, the external sex organs of these children will look ambiguous, or perhaps even male, although they are genetically female, usually with normally developed ovaries. A similar syndrome has occurred in the babies of some women who took synthetic forms of the hormone progesterone during pregnancy, which turned out to have similar effects to male hormones. Other girls may be born with a condition known as "Androgen Insensitivity Syndrome" in which they actually have an XY genetic structure but develop as normal girls because they are not sensitive to the male hormones which the body produces.
Just to make things more complicated, recent medical research has indicated that areas of the brain are affected by hormone development while the baby is in the womb, and that these developments influence the way in which the person will prefer to act all of their lives. Such research indicates that, irrespective of their genetic sex and their internal and external sex organs, people with a female brain development will prefer female play and activities and people with a male brain development will prefer male play and activities.
So even from the point of conception, the commonest question asked about a new baby - "Is it a boy or a girl?" may not have quite such an easy answer as at first appears. We have to recognise the existence of four ways of describing the baby's sex - genetic sex; biological sex according to internal sex organs; biological sex according to external sex organs; and brain sex. And although, in most cases, all four of these ways match the same description - male or female -there are ample cases where they do not.
The New Scientist of 18th January 1992 carried an article about the use of "sex-tests" at the Olympic Games. Since 1968 the International Olympic Committee has tested the sex of competitors by taking a smear from the inside of their cheek {the Buccal Smear test) and analysing its genetic structure. Only a conventional XX result was accepted as evidence of female status. Obviously, this meant that women either with Turner's Syndrome, or with Androgen Insensitivity Syndrome, were defined as being men and were excluded. The personal emotional suffering and professional humiliation which this caused to women who had never been regarded before as anything else other than female can be imagined As one such athlete, the Spanish hurdler Mario Patino, put it, "In the eyes of God and medicine I am a woman." Campaigners against this practice have now won agreement from the International Olympic Committee that, from 1992 onwards, this test will be dropped.
Source: New Scientist18th January 1992, p.14
