In addition to these mouth, hand and general body contacts, there is also a tendency at high intensities of pre-copulatory activity to rub the genitals rhythmically against the partner’s body. There is also a considerable amount of twining and inter-twining of the arms and legs, with occasional powerful muscle contractions, so that the body is thrown into a state of clinging tension, followed by relaxation.
These, then, are the sexual stimuli that are given to the partner during bouts of pre-copulatory activity, and which produce sufficient physiological sexual arousal for copulation to occur. Copulation starts with the insertion of the male’s penis into the female’s vagina. This is most commonly performed with the couple face-to-face, the male over the female, both in a horizontal position, with the female’s legs apart. There are many variations of this position, as we shall be discussing later, but this is the simplest and most typical one. The male then begins a series of rhythmic pelvic thrusts. These can vary considerably in strength and speed, but in an uninhibited situation they are usually rather rapid and deeply penetrating. As copulation progresses there is a tendency to reduce the amount of oral and manual contact, or at least to reduce its subtlety and complexity. Nevertheless these now subsidiary forms of mutual stimulation do still continue to some extent throughout most copulatory sequences.
The copulatory phase is typically much briefer than the pre-copulatory phase. The male reaches the consummatory act of sperm ejaculation within a few minutes in most cases, unless deliberate delaying tactics are employed. Other female primates do not appear to experience a climax to their sexual sequences, but the naked ape is unusual in this respect. If the male continues to copulate for a longer period of time, the female also eventually reaches a consummatory moment, an explosive orgasmic experience, as violent and tension-releasing as the male’s, and physiologically identical with it in every way except for the single obvious exception of sperm ejaculation. Some females may reach this point very quickly, others not at all, but on the average it is attained between ten and twenty minutes after the start of copulation.
It is strange that there is this discrepancy between the male and female as regards the time taken to reach sexual climax and relief from tension. This is a matter that will have to be discussed in detail later when the functional significance of the various sexual patterns is being considered. Suffice it to say at this point that the male can overcome the time factor and arouse the female to orgasm either by prolonging and heightening the pre-copulatory stimulation, so that she is already strongly aroused before penis insertion takes place, or he can employ self-inhibitory tactics during copulation to delay his own climax, or he can continue to copulate immediately after ejaculation and before he loses his erection, or he can rest briefly and then copulate for a second time. In the latter case, his reduced sex drive will automatically ensure that he takes much longer to reach his next climax and this will give the female sufficient time on this occasion to reach hers.
After both partners have experienced orgasm there normally follows a considerable period of exhaustion, relaxation, rest, and frequently sleep.
From the sexual stimuli we must now turn to the sexual responses. How does the body respond to all this intensive stimulation? In both sexes there are marked increases in pulse rate, blood pressure and respiration. These changes begin during pre-copulatory activities and rise to a peak at the copulatory climax. Pulse rates which, at normal level, stand at 70 to 80 per minute, rise to 90 to 100 during the earlier phases of sexual arousal, then climb to 130 during intense arousal and attain a peak of about 150 at orgasm. Blood pressure that starts at about 120 rises to 200 or even 250 at the sexual climax. Breathing becomes deeper and more rapid as arousal develops and then, as orgasm approaches, develops into prolonged gasping often accompanied by rhythmic moaning or grunting. At climax the face may be contorted, with mouth wide open and nostrils expanded, in a manner similar to that seen in an athlete in extremis, or someone fighting for air.
Another major change that occurs during sexual arousal is a dramatic shift in the distribution of blood, from the deeper regions to the surface areas of the body. This overall forcing of additional blood into the skin leads to a number of striking results. It produces not only a body that feels generally hotter to the touch – a sexual glow, or fire – but also certain specific changes in a number of specialized areas. At high intensities of arousal a characteristic sexual flush appears. It is most commonly seen in the female, where it usually begins in the region of skin over the stomach and upper abdomen, then spreads to the upper part of the breasts, then the upper chest, then the sides and middle region of the breasts and finally the undersides of the breasts. The face and neck may also be involved. In very intensely responding females it may also spread over the lower abdomen, the shoulders, the elbows, and, with orgasm, to the thighs, buttocks and back. In certain cases it may cover almost the whole body surface. It has been described as a measles-like rash and appears to be a visual sexual signal. It also occurs, but in fewer cases, in the male where, again, it starts in the region of the upper abdomen, spreads over the chest and then the neck and face. It occasionally also covers the shoulders, forearms and thighs. Once orgasm has been reached, the sex flush rapidly disappears, vanishing in reverse order to its sequence of appearance.
In addition to the sex flush and general vaso-dilation, there is also marked vaso-congestion of various distensible organs. This blood congestion is caused by the arteries pumping blood into these organs faster than the veins can carry it away. The condition can be maintained for considerable periods of time because the engorgement of the blood vessels in the organs itself helps to close off the veins that are attempting to carry the blood away. This occurs in the lips, nose, ear-lobes, nipples and genitals of both sexes and also in the breasts of the female. The lips become swollen, redder and more protuberant than at any other time. The soft parts of the nose become swollen and the nostrils expanded. The ear-lobes also become thickened and swollen. The nipples become enlarged and erect in both sexes, but more so in the female. (This is not due to vaso-congestion alone, but also to nipple muscle contraction.) Female nipple length increases by as much as one centimetre, and nipple diameter as much as a half a centimetre. The areola region of pigmented skin around the nipples also becomes tumescent and deeper in colour in the female, but not in the male. The female breast also shows a significant increase in size. By the time orgasm has been reached the breast of the average female will have increased by anything up to 25 per cent of its normal dimensions. It becomes firmer, more rounded and more protuberant.
The genitals of both sexes undergo considerable changes as arousal proceeds. The vaginal walls of the female experience massive vaso-congestion leading to rapid lubrication of the vaginal tube. In some cases this may occur within seconds of the beginning of pre-copulatory activity. There is also a lengthening and distension of the inner two-thirds of the vaginal tube, the overall length of the vagina increasing up to ten centimetres at the phase of high sexual excitement. As orgasm approaches, there is a swelling of the outer one-third of the vaginal tube, and during orgasm itself there is a two- to four-second muscle-spasm contraction of this region, followed by rhythmic contractions at intervals of 0.8 of a second. There are from three to fifteen of these rhythmic contractions in each orgasmic experience.
During arousal the external female genitals become considerably swollen. The outer labia open and swell, and may show size increases of up to two or three times the normal proportions. The inner labia also become distended to two or three times their normal diameter and they protrude through the protective curtain of the outer labia, adding as they do so an extra centimetre to the overall vaginal length. As arousal progresses there is a second striking change in the inner labia. Having already become vaso-congested and protuberant, they now change colour, turning bright red.
The clitoris (the female counterpart of the male penis) also becomes enlarged and more protuberant as sexual arousal begins, but a
s higher levels of excitement are reached, the labial swelling tends to mask this change and the clitoris is retracted under the labial hood. It cannot at this later stage be stimulated directly by the male’s penis, but in its swollen and sensitive condition can still be affected indirectly by the rhythmic pressures applied to that region by the thrusting movements of the male.
The penis of the male undergoes a dramatic modification with sexual arousal. From a limp, flaccid condition it expands, stiffens and erects by means of intensive vaso-congestion. Its normal, average length of nine and a half centimetres is increased by seven to eight centimetres. The diameter is also considerably increased, giving the species the largest erect penis of any living primate.
At the moment of male sexual climax there are several powerful muscle contractions of the penis that expel the seminal fluid into the vaginal tube. The first of these contractions are the strongest ones and occur at intervals of 0.8 of a second – the same rate as the orgasmic vaginal contractions of the female.
During arousal the scrotal skin of the male becomes constricted and the mobility of the testes is reduced. They are elevated by a shortening of the spermatic cords (as, indeed, they are in states of cold, fear and anger) and are held tighter against the body. Vaso-congestion of the region results in a testicular size increase of up to fifty or even a hundred per cent.
These, then, are the principal ways in which the male and female bodies become modified by sexual activity. Once the climax has been reached, all the changes noted are rapidly reversed and the resting, post-sexual individual quickly returns to the normal quiescent physiological state. There is one final, post-orgasmic response that is worth mentioning. There may be a copious sweating by both male and female immediately following sexual climax and this may occur regardless of how much or how little physical effort has been put into the preceding sexual activities. However, although it is not related to total physical expenditure, it does bear a relationship to the intensity of the orgasm itself. The film of sweat develops on the back, the thighs and the upper chest. Sweat may run from the armpits. In intense cases, the whole of the trunk, from shoulders to thighs, may be involved. The palms of the hands and soles of the feet also perspire and, where the face has become mottled with the sexual flush, there may be sweating on the forehead and upper lip.
This brief summary of the sexual stimuli of our species and the responses given to them can now serve as a basis for discussing the significance of our sexual behaviour in relation to our ancestry and our general way of life, but first it is worth pointing out that the various stimuli and responses mentioned do not all occur with equal frequency. Some occur inevitably whenever a male and female come together for sexual activity, but others appear only in a proportion of the cases. Even so, they still occur with a sufficiently high frequency to be counted as ‘species characteristics’. As regards the body responses, the sex flush is seen in 75 per cent of females and about 25 per cent of males. Nipple erection is universal for females, but only occurs in 60 per cent of males. Copious sweating after orgasm is a feature of 33 per cent of both males and females. Apart from these specific cases, most of the other body responses mentioned apply in all cases, although, of course, their actual intensity and duration will vary according to the circumstances.
Another point that requires clarification is the way in which these sexual activities are distributed throughout the individual’s lifetime. During the first decade of life no true sexual activity can occur in either sex. A great deal of so-called ‘sex-play’ can be observed in young children, but until the female has begun to ovulate and the male to ejaculate, functional sexual patterns obviously cannot occur. Menstruation begins for some females at the age of ten and by the age of fourteen 80 per cent of young females are actively menstruating. All are doing so by the age of nineteen. The development of pubic hair, the broadening of the hips, and the swelling of the breasts accompanies this change and, in fact, slightly precedes it. General body growth proceeds at a slower rate and is not completed until the twenty-second year.
The first ejaculation in boys does not usually occur until they have reached eleven years, so that they are sexually slower starters than the girls. (The earliest recorded successful ejaculation is for a boy of eight, but this is most unusual.) By the age of twelve, 25 per cent of boys have experienced their first ejaculation and by fourteen 80 per cent have done so. (At this point, therefore, they have caught up with the girls.) The mean age for the first ejaculation is thirteen years and ten months. As with the girls, there are characteristic accompanying changes. Body hair begins to grow, especially in the pubic region and on the face. The typical sequence of appearance of this hairiness is: pubic, armpit, upper lip, cheeks, chin, and then, much more gradually, the chest and other parts of the body. Instead of a broadening of the hips, there is a widening of the shoulders. The voice becomes deeper. This last change also takes place in the girls but to a much smaller extent. In both sexes there is also an acceleration of the growth of the genital organs themselves.
It is interesting that, if one measures sexual responsiveness in terms of frequency of orgasm, the male is much quicker to reach his peak of performance than the female. Although males begin their sexual maturation process a year or so behind the girls, they nevertheless attain their orgasmic peak while they are still in their teens, whereas the girls do not reach theirs until their mid-twenties or even thirties. In fact, the female of our species has to reach the age of twenty-nine before she can match the orgasm rate of the fifteen-year-old male. Only 23 per cent of fifteen-year-old females will have experienced orgasm at all, and this figure has only risen to 53 per cent by the age of twenty. By thirty-five it is 90 per cent.
The adult male achieves an average of about three orgasms a week, and over seven per cent experience daily or more than daily ejaculation. The frequency of orgasm for the average male is highest between the ages of fifteen and thirty, and then drops steadily from thirty to old age. The ability to achieve multiple ejaculation fades, and the angle at which the erect penis is carried also drops. Erection can be maintained for an average of nearly an hour in the late teens, but it has fallen to only seven minutes at the age of seventy. Nevertheless, 70 per cent of males are still sexually active at the age of seventy.
A similar picture of waning sexuality with increasing age is found in the female. The more or less abrupt cessation of ovulation at around the age of fifty does not markedly reduce the degree of sexual responsiveness, when the population is taken as a whole. There are, however, great individual variations in its influence on sexual behaviour.
The vast majority of all the copulatory activity we have been discussing occurs when the partners are in a pair-bonded state. This may take the form of an officially recognized marriage, or an informal liaison of some sort. The high frequency of non-marital copulation that is known to take place should not be taken to imply a random promiscuity. In most cases it involves typical courtship and pair-formation behaviour, even if the resulting pair-bond is not particularly long-lasting. Approximately 90 per cent of the population becomes formally paired, but 50 per cent of females and 84 per cent of males will have experienced copulation before marriage. By the age of forty, 26 percent of married females and 50 percent of married males will have experienced extramarital copulation. Official pair-bonds also break down completely in a number of cases and are abandoned (0.9 per cent in 1956 in America, for example). The pair-bonding mechanism in our species, although very powerful, is far from perfect.
Now that we have all these facts before us we can start to ask questions. How does the way we behave sexually help us to survive? Why do we behave in the way we do, rather than in some other way? We may be helped in these questions if we ask another one: How does our sexual behaviour compare with that of other living primates?
Straight away we can see that there is much more intense sexual activity in our own species than in any other primates, including our closest relations. For them, the lengthy court
ship phase is missing. Hardly any of the monkeys and apes develop a prolonged pair-bond relationship. The pre-copulatory patterns are brief and usually consist of no more than a few facial expressions and simple vocalizations. Copulation itself is also very brief. (In baboons, for instance, the time taken from mounting to ejaculation is no more than seven to eight seconds, with a total of no more than fifteen pelvic thrusts, often fewer.) The female does not appear to experience any kind of climax. If there is anything that could be called an orgasm it is a trivial response when compared with that of the female of our own species.
The period of sexual receptivity of the female monkey or ape is more restricted. It usually only lasts for about a week, or a little more, of their monthly cycle. Even this is an advance on the lower mammals, where it is limited more severely to the actual time of ovulation, but in our own species the primate trend towards longer receptivity has been pushed to the very limit, so that the female is receptive at virtually all times. Once a female monkey or ape becomes pregnant, or is nursing a baby, she ceases to be sexually active. Again, our species has spread its sexual activities into these periods, so that there is only a brief time just before and just after parturition when mating is seriously limited.
Clearly, the naked ape is the sexiest primate alive. To find the reason for this we have to look back again at his origins. What happened? First, he had to hunt if he was to survive. Second, he had to have a better brain to make up for his poor hunting body. Third, he had to have a longer childhood to grow the bigger brain and to educate it. Fourth, the females had to stay put and mind the babies while the males went hunting. Fifth, the males had to co-operate with one another on the hunt. Sixth, they had to stand up straight and use weapons for the hunt to succeed. I am not implying that these changes happened in that order; on the contrary they undoubtedly all developed gradually at the same time, each modification helping the others along. I am simply enumerating the six basic, major changes that took place as the hunting ape evolved. Inherent in these changes there are, I believe, all the ingredients necessary to make up our present sexual complexity.
The Naked Ape Page 6