«To your beginning as a cell, egg and sperm had each contributed 23 chromosomes, each chromosome carrying its hundreds of genes like beads on strings. The sperm’s 23 chromosomes paired up with the egg’s 23 chromosomes, giving the new cell 23 pairs, or a total of 46 chromosomes. Only one pair determined your genetic sex. Mothers always contribute an X to the sex-regulating pair, so everybody gets at least one X. Fathers contribute either an X or a Y. If an X-carrying sperm won the swimming race, you are a chromosomal female; if a Y won, you are a chromosomal male.A few real differences between boys and girls affect their attitudes and sexual behavior with each other. One of the most striking differences is that boys are more oriented toward their genitals, generally speaking, and are a little more concerned with genital activity. A girl is more interested in the things surrounding sex than with sex itself. If girls and boys understood this simple fact, they’d be better able to get along with each other. They learn to be partners of each other, with equal needs, responses, and responsibilities.
From your beginning as a single fertilized cell that multiplied rapidly, your cells soon clustered to form the rudimentary organs of an embryo. Sexually, it was an allpurpose embryo with the growth buds — embryologists call them anlagen—of either male or female organs. First there’s a pair of gonads, which can develop into either testicles or ovaries. Then there are two sets of internal genital ducts or tubes. One of these sets of structures, called wolffian after Kaspar Wolff, the eighteenth-century anatomist who identified it, develops into seminal vesicles, prostate gland and the long tubes, one on each side, called the vasa deferentia, for a male. The other structure, called mullerian for the nineteenth-century anatomist, Johannes Muller, develops into a uterus, fallopian tubes, and upper vagina in a female. There is also a tiny, protruding bud of tissue called a genital tubercule, which can adapt itself for either sex, becoming either a penis or a clitoris. Below the genital tubercule is an opening that fuses together in a male, or stays open in a female.
For six weeks after conception, XX and XY embryos proceed along the same neutral road of sex development. At the end of the sixth week there’s a fork in the road, one branch leading in the male direction. At that point, the Y chromosomes of a male embryo send a message somehow, nobody yet knows how, to the two gonads, left and right, ordering them to proliferate, develop tubular structures, and become testicles. If you had no Y to divert you, you went on for another six weeks before the primitive, undifferentiated gonads began to develop definitely into ovaries packed with egg cells, enough to last you a lifetime. If you got a second X from your father to go with the one from your mother, the double-X chromosomes steered you onto this female branch.
Although the XX or XY chromosomal pattern you had when you were only one cell is duplicated in every cell of your body even now, the sex chromosomes’ influence ended once their sex-determining message was dispatched to your gonads. So far as is known, the sex chromosomes have never again played any direct part in programming your sex life.
When it has differentiated as a testicle, the gonad starts manufacturing sex hormone. Cholesterol, a chemical relative of fat, is the raw material for the sex hormone production line. From cholesterol the testes first synthesize progesterone, a progestin known as the pregnancy hormone; then androgen, the masculinizing hormone; and finally estrogen, the feminizing hormone. Testicles carry the process through to make some estrogen, but nothing like as much as ovaries produce. Chemically speaking, they are all closely related, but each hormone has its specific functions and each takes various forms. Progestin is called the pregnancy hormone because a woman’s progestin level goes up during pregnancy (and also after ovulation during the course of the menstrual cycle in preparation for a possible pregnancy). While androgen is called the male hormone, estrogen the female hormone, and progestin the pregnancy hormone, these names are somewhat misleading since everybody normally keeps all three sex hormones in circulation. The difference is in the proportion of the mixture. Testicles produce enough androgen to dominate the estrogen in a male, while ovaries produce enough estrogen to dominate the androgen in the female. With the sex hormones, it’s a question of threshold — of more or less rather than either-or.
The amount of sex hormones produced and the proportion of each in the mixture are not the same in all men or in all women, nor do they stay the same in any one individual. Variation normally stays within limits, however. Variation beyond the normal limits, especially at a critical period of prenatal life, can have dramatic consequences.
Your hormone mix steered you at the fork in the prenatal road where your embryonic internal genital structures, wolffian and mullerian, found their destiny. One set of structures began to develop, the other to wither away. If you are a man, your testicular hormone production during that critical prenatal period stimulated your wolflian structures to develop as seminal vesicles, prostate, and vasa. The mix also contained a special temporary substance that stopped your mullerian structures in their tracks. If your prenatal hormone mix was not masculine, your mullerian structures went ahead in the normal female way and developed as a uterus, fallopian tubes, and upper vagina, while your wolflian structures began to atrophy. Note that in this second case you didn’t need a female hormone mix. Ovarian hormone production appears to be irrelevant to prenatal female sex differentiation. It takes a male hormone mix to make the wolflian structures develop, and it takes that special temporary hormone called simply “mullerian-inhibiting hormone,” which is secreted during this period by testicles, to keep the mullerian structures from pursuing their ambition to become a uterus, fallopian tubes, and upper vagina, but it takes no hormonal push at all for this stage of development to proceed in feminine fashion. While the absence of a Y chromosome and the presence of at least two X chromosomes are needed to make a gonad become an ovary, as soon as the gonad fork is passed, the neutral road and the female road converge. Unless there is a sufficient push in the male direction, the fetus will take the female turn at any subsequent fork, whether there is a female push or not. Nature’s first choice is to make Eve. Everybody has one X chromosome and everybody is surrounded by a mother’s estrogens during prenatal life. Although not enough for full development as a fertile female, this gives enough momentum to support female development. Development as a male requires effective propulsion in the male direction at each critical stage. Unless the required “something more” is provided in the correct proportions and at the proper times, the individual’s subsequent development follows the female pattern.
Males are generally more vulnerable to sexual differentiation errors than females. If any one of your sexual systems fail, you can coast down the female road, but not down the male. Population statistics support the general proposition of male vulnerability. Males lead at conception by something like 140 to 100, but at birth that lead has been whittled down to 105 to 100. While many factors obviously influence the statistics, nevertheless the trend continues throughout life. The forty-year-old population of the United States is now divided almost evenly between men and women, but in the older age groups women outnumber men, and among those sixty-five and older there are only 70 men left for every 100 women still living.
After your chromosomal sex and your gonadal sex were settled, your hormone mix established, and after one set of your reproductive organs had begun to develop, the other to atrophy, you came to the last fork in the sexual differentiation road before birth, namely, the molding of your external genitals. Here, too, the sex hormones called the turn. “Molding” is the right word because the materials for fashioning either model are the same. Beside the genital tubercule and single opening, the materials are a fold or strip of skin and a small swelling on each side of the opening.
Female molding needs no hormone stimulus, only the absence of male hormone. If your hormone mix was not male, the genital tubercule stayed small to become your clitoris; the two folds of skin did not fuse but stayed separate as the two labia minora and the hood of the clitoris; and the two swellings remained separate as the two labia majora. The opening developed a dividing wall to separate the entrance of the vagina leading to your uterus from the urethra connecting with your bladder.
If your hormone mix was masculine, the genital tubercule became your penis, and the two folds of skin, fusing in a seam on the underside, wrapped themselves around the penis to form a urethral tube. The two swellings fused together and formed a scrotum to receive your testicles when they descended, which they probably did about seven months after you were conceived. The urethral tube connected with your bladder and your prostate gland, vasa deferentia, and testicles. (It is the vasa deferentia that are cut in a vasectomy, an operation that more and more men are electing as a birth control method, for the vasa carry the sperm from the testicles to mix with fluid from the prostate to form semen.)
This last turning point, the molding of your external genitals, got you an M or an F on your birth certificate.»
(Money, John and Patricia Tucker. Sexual Signatures: What it Means to be a Man or a Woman)
Comparison of observable sexual behaviors of children and adults | |
Developmentally expected Moral, social or familial rules may restrict, but these behaviors are not abnormal, developmentally harmful, or illegal when private, consensual, equal, and non-coercive. | |
Prepubescent | Postpubescent |
• Genital or Reproduction conversations with peers or similar age siblings | • Sexually explicit conversations with peers |
• Show me yours/I'll show you mine with peers, playing "doctor" | • Interest in erotica |
• Imitating seduction (i.e., kissing, flirting) | • Sexual innuendo, flirting and courtship |
• Simulating foreplay with dolls and peers | • Foreplay (petting, making out, fondling) |
• Simulating intercourse with dolls and peers | • Monogamist intercourse (stable or serial) |
• Dirty words or jokes within cultural or peer group norm | • Obscenities and jokes within cultural norm |
• Hugging, kissing, holding hands | |
• Solitary masturbation | |
• Mutual masturbation | |
• Group masturbation | |
Requiring Attention |
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• Sexually explicit conversation with peers, sexual innuendo, teasing | • Polygamist sexual intercourse (promiscuity) |
• Preoccupation with masturbation | |
• Preoccupation with sexual themes | |
• Sexual anxiety (interfering in daily functioning) | |
• Sexual aggressiveness/obscenities | |
• Mooning and obscene gestures |
|
• Pornographic interest |
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• Sexual graffiti (especially chronic or impacting individuals) | |
• Violation of other’s body space (pulling other's skirt up or pants down, intervention into bathing and sleeping) | |
• Embarrassment of others with sexual themes | |
• Precocious sexual knowledge | |
• Peeping | |
• Exposing | |
• Public frottage, petting, humping, French kissing | |
• Sexual contact with significant age difference (child sexual abuse) | |
• Simulating intercourse with animals | |
Requiring Correction |
|
• Sexually explicit conversations with significant age difference | |
• Touching genitals of others without permission (i.e. grabbing, goosing) | |
• Degradation/humiliation of self or others with sexual themes | |
• Attempting to expose others' genitals | |
• Inducing sexually explicit fear |
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• Sexually explicit proposals/threats of force including written notes | |
• Chronic peeping/exposing/obscenities/pornographic interests/frottage | |
• Compulsive masturbation (especially chronic or public)/task interruption to masturbate | |
• Masturbation which includes vaginal or anal penetration | |
• Sexual contact with animals (bestiality) | |
Requiring Prohibition |
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• Oral, vaginal, anal penetrations | |
• Obscene phone calls, voyeurism, exhibitionism, frottage, sexual harassment |
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• Forced exposure of other's genitals | |
• Forced sexual contact (sexual assault) | |
• Forced penetration (rape) | |
• Genital injury to others | |
• Any genital injury of bleeding not explained by accidental cause | |
Stable monogamy is defined as a single sexual partner throughout
adolescence. Serial monogamy indicates long-term (several months or years) involvement with a single partner which ends and then others follow. Polygamist intercourse is defined as indiscriminate sexual contact with more than one partner during the same period of time. |