In the very early embryo there is little visible evidence of what he or she will eventually look like. At this stage of life all individuals look the same. Nevertheless, the genetic material in the chromosomes, which have come from the mother’s egg and father’s sperm cells, is beginning to work and whether or not an individual will become a superb athlete or a slightly built dancer is already decided. Environmental factors, both during the time in the womb and after birth, may cause changes in the eventual appearance of a mature adult but, in the main, the pattern is fixed and is already taking shape.
Although the sex of the baby is decided at conception, the foetus is not recognizably male or female until the seventh week. By this stage the germ cells, which make up the sex glands, have come together to form the testes in the male child and the ovaries in the female. During the remaining months of life in the uterus, the testes make their way slowly down the body of the male foetus into the groin and eventually into the scrotum. The final descent into the scrotum is sometimes delayed until well after birth. This condition is known as undescended testes. The female ovaries likewise descend in the developing body cavity, but they stop in the pelvic region where they remain for the rest of the individual’s life.
The importance of the sex glands is that they produce hormones-chemical substances-which bring about the formation of the external sexual characteristics of male and female. The male hormones, mainly testosterone, are produced by the adrenal gland and by the testes. The female hormones, oestrogens, are also produced by the adrenals and by the ovaries. Male and female hormones arc not present in any significant quantity at the beginning of life. They make their appearance at puberty when the ovaries and the testes become active. Whether a baby is to be a male or female child is decided by the fact that, in the case of a boy, male hormones bring about the development of the scrotum.
The female child, lacking male hormones, is born with unfused labia instead of a scrotum and a small clitoris instead of a penis. These differences apart, the physical form of a male and female child is identical. For this reason, although doting parents may feel that their infant looks just like the boy (or girl) he (or she) is, the unbiased observer may be forgiven for mistaking the baby’s gender. The similarity in external physical appearance continues in early childhood. With the onset of puberty, however, physical changes begin to take place. The actual age of puberty varies widely but, in any given population, tends to be earlier in girls than in boys. The mechanisms by which these changes arc brought about are shown below.
The speed with which puberty changes take place also varies a great deal. The earlier physical development of girls in their early teens is often reflected in their mental attitudes, which tend to be more mature than boys of equal age. Interest in the opposite sex usually starts earlier in girls, but, here again, individuals vary considerably. A group of normal fourteen-year-old girls, for example, may vary from a physically and emotionally immature girl-child to full-blown voluptuousness.
Environment plays an important part in both physical and mental development. Good nutrition encourages the growth of good physique, whilst education and parental influence play an important part in psychological attitudes. Puberty is a time of change and is often a time of trial for the individual concerned. A knowledge of the changes that are taking place and an understanding approach by older members of a family help to smooth the sometimes difficult path from childhood, through the turbulence of adolescence, to adulthood.