1. THE PROCESS OF SEXUAL DIFFERENTIATION
The sex of a human being is determined at the time of fertilization. However, for the first few weeks of their lives the unborn males and females are indistinguishable. Their maleness or femaleness manifests itself only gradually over a period of time.
We are all used to identifying newborn children as either boys or girls according to their different external sex organs. Still, apart from these organs, they look very much alike. The typical male or female appearance of men or women results from developments that do not begin until many years later. The full extent of human sexual differences appears only after both males and females have reached sexual maturity, i.e., when they can have children of their own.
Most of us think of sex as the simplest and most fundamental of all human distinctions. Indeed, this very assumption is implied in our language. The word "sex" is derived from the Latin sexus which, in turn, has its roots in the verb secare: to cut, separate, or divide. In the strict sense of the term, therefore, "sex" simply refers to that which divides the human race (and most higher animal and some plant life) into two distinct groups—males and females. Every individual belongs to either one of these groups, i.e., to one of the two sexes. A person is either of male or female sex.
All of this seems plain enough. However, recent scientific research has shown that the traditional simple definitions of maleness and femaleness are quite inadequate and that, in some cases, the matter can actually be very complicated. When a modern scientist is asked to identify a person as either male or female, he takes at least seven different factors into account:
1. Chromosomal Sex
The cells of the male body contain one X and one Y chromosome, while those of the female body contain two X chromosomes. However, recently several other chromosomal combinations have been discovered.
2. Gonadal Sex
The male has testicles (male gonads); the female has ovaries (female gonads). However, in rare cases both testicular and ovarian tissue may be present in the same body.
3. Hormonal Sex
The hormones secreted by the testicles or ovaries play an important part in developing the male or female body before birth and during puberty, A lack, imbalance, or oversupply of these hormones has a decisive influence on a person's anatomy and physiology.
4. Internal Accessory Reproductive Structures
The male has sperm ducts, seminal vesicles, a prostate gland, etc., while the female has Fallopian tubes, a uterus, a vagina, etc. In rare cases, some or all of these organs may be underdeveloped or missing.
5. External Sex Organs
The male has a penis and a scrotum; the female has a clitoris, major and minor lips, etc. In rare cases, some or all of these organs may be underdeveloped or missing.
6. Sex of Assignment and Rearing
A child with a male body will usually be raised as a male. However, it is possible to raise such a child as a female, and vice versa.
7. Sexual Self-identification
A child with a male body who is taught to assume the role of a male will usually learn to consider himself male. However, it is possible that in spite of parental suggestions he nevertheless ends up identifying himself as female. Conversely, a child with a female body who is taught to assume the role of a female may nevertheless identify herself as male.
Scientists now realize that these seven variables may be independent of each other. For example, a newborn child may have the internal sex organs of a female while the external sex organs appear to be those of a "sexually unfinished" male. On the basis of this deceptive appearance, the child may then be declared a boy and raised as such. (See also "Sexual Malformations.") Another example is a person whose sexual self-identification is at odds with the sex that has been assigned to him. (See "Transsexualism.") Such possible incongruities can, of course, create many medical and social problems. Fortunately, most people are clearly male or female by all seven criteria and therefore require no special professional help during their sexual development.
However, even where maleness and femaleness are not in doubt, there still may be some uncertainty about the proper social roles of males and females. Thus, in the past men and women were often assumed to have very little in common. They were not only expected to look different, but also to behave differently. Based on this expectation, most societies developed different social roles and different moral standards for the two sexes.
Modern research has raised a great deal of doubt about these traditional assumptions, although one major difference between males and females remains undisputable: that which concerns their reproductive functions. While both sexes are needed to make the creation of new human life possible, only women actually conceive, bear, and nurse children. In most other respects, however, the sexual differences are not as fundamental as it might seem. Indeed, many male and female characteristics that were formerly considered inborn and unchangeable have been shown to be inbred, i.e., the result of cultural influences. It is, of course, not always easy to draw a dividing line between biological inheritance and social conditioning. The scientific study of these matters is still in its beginnings. In the meantime, it seems useful to remember the many similarities between the sexes. Generally speaking, men and women would far better understand each other if they realized that they are alike in their basic anatomy and physiology.
The following pages summarize the physical differences between the sexes as they emerge during the process of sexual maturation. For sexual differences in behavior and social status, see "The Development of Sexual Behavior'' and "The Social Roles of Men and Women."