As early as 1960, published reports attested to the fact the people were sexually active in the seventh, eighth, and ninth decades. With good health and an available sex partner, older people were able to enjoy sexual relationships. Drives appeared to remain constant throughout life, with blacks being more active than whites, men more than women, and those of lower socioeconomic status more than those from upper classes.

In a sample of aging males whose average age was 71 years, 90% had satisfying sexual experiences, 75% retained persistent libido, and 60% remained potent. This study also attested to the constancy of the sex drive throughout life.

The adolescent is faced with a new status in society, has new demands made on him, and is subject to moral proscriptions that are in conflict with the changes in his physiology. Society attributes new status to the adolescent: at 16 years of age he may obtain a driver's license and at age 18 he is allowed to vote. Although the adolescent is physiologically mature and experiences intense sexual drives, society does not sanction adolescent premarital sexual behavior. Sexual privilege does not necessarily derive from rites of passage. In many states a girl who is less than 18 years old, but consents to intercourse, would technically be considered to have been raped.

There is perhaps no period in the life cycle during which changes in sexual anatomy and physiology are as profound as during adolescence. Immediately prior to and coincident with puberty, the genital organs develop rapidly, finally reaching their adult maturity.

Among the complex biologic changes seen during puberty are the budding of the breasts in girls and the beginning growth of pubic hair. These events occur at about age 10 or 11 years (but may occur between the ages of 8 and 13 years) and usually predate menstruation, which begins between the ages of 11 and 13 years. In boys, the comparable events of testicular enlargement and growth of pubic hair occur between the ages of 12 and 16 years. Ejaculation and enlargement of the penis tend to occur later, between the ages of 13 and 17 years.

In a review of a number of studies of sexual differences among children during the first year of life, Bardwick points out that even at birth there are significant differences between male and female infants. Males tend to be larger, to have more muscle mass, and to be more active. Females tend to be more passive in their motor responses and more sensitive to tactile stimuli and pain. At 6 months the female infant has a long attention span for visual stimuli, has a better fixation response to a human face, and is more responsive to social stimuli. She prefers complex stimuli such as jazz music, whereas the male infant has a better fixation response to a helix of light and is more attentive to an intermittent tone.

From the beginning of life, the human organism is indeed a sexual being. At conception, when sex is genetically determined, the individual is destined for specific and sex-related concept of herself or himself as well, as fulfillment of certain socially approved roles.

Much of the literature about sexuality deals largely with adult sexuality or problems of sexuality specific to the older population, as if to ignore the sexual nature of infants and children. It is important to recall that the beginning of the life cycle also is shaped by sexuality: long before birth, characteristics of sex are evident. During the first moments after birth, it is customary for the parents inquire first about the sex of their child, and later about his condition.

Between the ages of 2 and 3 years the child becomes more interested in his excretory functions. This period is usually characterized by some ambivalence toward the mother and is often termed the "pregenital" or "anal" period. Usually these years coincide with toilet training and are characterized by an increased awareness on the child's part of his genitalia.

Freud theorized that an Oedipal period exists that roughly coincides with the child's ages of 4 to 6 years. During this period, marked intensification of the sex drive occurs and the genitalia supercede other organs as the main source of pleasure. Masturbation that began earlier in infancy now occurs more frequently and is more sustained. Specific fantasies that drive from the child's intense desires toward his parents, his curiosity about the sexes, and theories about his conception and birth may accompany masturbation.

During the transition period from infant to toddler, core gender identity is solidified. The child can look at a picture and clearly differentiate sexual differences. She or he can distinguish between male and female by means of the differences in hair and clothing. The child continues to be able to identify body parts, and especially areas responsible for excretion. The child also develops distinct pride and pleasure in his or her own body, sometimes specifically in the genital area. Pleasurable genital self-stimulation also enhances this self-satisfaction. At about 21 months, the child can refer to the self by her or his own name, an event pivotal in the emergence of identity. By 2 years of age, the child is able to categorize people into boy and girl and has some awareness of the anatomic differences if she or he has had an opportunity to view them.