Copulatory postures

Anthropological studies indicate that face-to-face copulatory positions predominate among the majority of human societies for which reliable information exists. Usually, the woman lies on her back with the man on top of her; the ventro-ventral or so-called missionary position (Figure 5.1). In their study of Sexual Behavior in the Human Male, Kinsey, Pomeroy, and Martin (1948) reported that 70 per cent of North Americans used only the missionary position during sexual intercourse. Setting aside the sexual inhibitions and reluctance to explore different positions in some of these subjects, there appears to be a fundamental human preference for face-to-face copulatory behaviour. In China, it is the major pattern used, although 54 per cent of couples may sometimes try other positions (Liu et al. 1997). Ford and Beach (1951) found that face-to-face postures are widespread in many indigenous societies, and represent the most frequently recorded position among the 185 societies they examined worldwide. Variations of such positions involve the man squatting or kneeling before the woman, with her legs straddling his thighs. The man may then pull the woman up, so that the couple embraces, face-to-face. Ford and Beach noted that this behaviour is characteristic of Pacific Island peoples, such as the Trobrianders and the Balinese. It appears to be a common pattern among those peoples who colonized the South Pacific, beginning more than 40,000 years ago. Marquesan Islanders, for example, have a term for this position, haku noho (sitting style), as distinct from other positions used for intercourse (Suggs 1966).

Another type of copulatory posture, the female superior position, involves the woman sitting astride the man, as he reclines on his back (Figure 5.1). Kinsey, Pomeroy, and Martin (1948) record that this is the most common alternative to the missionary position among North American couples. It also occurs as a secondary posture in many other societies around the world (Ford and Beach 1951).

Finally, there are variants of the dorso-ventral copulatory posture (Figure 5.1). These are typical of the great majority of mammals, in which the male mounts the female from the rear. Copulatory positions involving

Figure 5.1 The principal human copulatory positions: Ventro-ventral ('missionary position'), female superior, and dorso-ventral. Source: Author's drawings from photographs in LeVay and Valente (2002).

rear entry did not represent 'the usual practice' among the societies considered by Ford and Beach. However, they noted twelve examples in which intercourse occasionally takes place while the couple lies side by side, with 'the man entering the woman from the rear.' In eight societies (the Crow, Dobuans, Hopi, Kurtatchi, Kuroma, Lepcha, Marshall Islanders, and Wogeo) full dorso-ventral positions are sometimes used, 'with the man standing behind the woman as she bends over or rests on her hands and knees'. Suggs (1966) also records this position for the Marquesans, who refer to it as patu hope. The Mar-quesans also use a position in which the female lies on her back, and the man faces her while lying on his side. They refer to intercourse in this side position, as haka ka'aka or 'in the gecko-lizard manner'. How frequently dorso-ventral copulatory postures are used by people of the various western cultures is not known. However, such positions are frequently depicted in sex manuals and in the literature on sexual behaviour in North America and Europe.

Ford and Beach (1951) speculated that the evolution of ventro-ventral and female superior copula-tory positions in human beings might be connected with the requirement to achieve maximum stimulation of the clitoris during intercourse, and thus to facilitate female orgasm. The evidence available to Ford and Beach indicated that, among the primates, the occurrence of female orgasm is unique to human beings. Moreover, it was thought that all the non-human primates copulate in dorso-ventral positions, and that postures involving rear entry by the male might not be conducive to clitoral stimulation and the occurrence of female orgasm. Ventro-ventral copulatory postures had been observed in orangutans and in immature chimpanzees, but only in captive animals. It seemed to Ford and Beach that the natural sexual behaviour of free-ranging apes might well be different, and more typical of the situation observed in other primates.

It is now known that neither female orgasm nor ventro-ventral and female superior copulatory postures are unique to Homo sapiens. In the last chapter, orgasm in female stump-tail macaques, Japanese macaques, chimpanzees, and other species was discussed, and compared to putatively homologous responses in the human female. A ventro-ventral copulatory position is not a prerequisite for the expression of such responses, as they occur in female monkeys and chimpanzees during dorso-ventral contacts with males. The capacity for female orgasm appears to be an ancient trait among anthropoid primates, and would most likely have been present in ancestral hominids, such as the australopithecines. This capacity is not equally expressed among females, however, so that some women report that additional (e.g. manual) stimulation by the partner is required for them to attain orgasm. In one study of 300 married American women, more than 90 per cent of them had orgasms during intercourse but, for 95 per cent of these women, orgasm was only achieved as a result of additional manual stimulation of the clitoris, either before or after intercourse (Fisher 1973).

Foreplay or post-coital manipulation of the clitoris therefore plays a substantial role in enhancing orgasmic responsiveness in women. The missionary position alone provides no guarantee that female orgasm will be more likely to occur. In human societies where attitudes towards sexual intercourse are repressive, the incidence of female orgasm is probably low. For example, among the Yolngu of Arn-hem Land, in northern Australia, it is customary to arrange marriages between young women and much older men. Among the Sambia of Papua New Guinea, men frequently marry women from other villages, and these 'in marrying' women are often not trusted or treated affectionately by their husbands. In both these cultures, intercourse is said to be peremptory in nature and often lacking in orgasm for the female partners. We saw in the last chapter that female orgasm serves no established function in sperm transport or fertility in human beings. Rather, it is most likely to represent a non-adaptive homologue of orgasm during ejaculation in the male (Symons 1979; Lloyd 2005). Thus, when the sexual relationship lacks sufficient rapport, or where psychological factors such as sexual guilt interfere with such rapport, then women may be inhibited from displaying orgasms. This kind of inhibition also occurs in some men who, despite prolonged copula-tory stimulation, are unable to achieve orgasm and to ejaculate intra-vaginally. Inhibition of orgasm in the female also has its (rarer) male counterpart, therefore (Masters and Johnson 1970).

If the ventro-ventral and female superior copula-tory postures depicted in Figure 5.1 did not evolve to enhance the likelihood of female orgasm, what is the origin of such behaviour in human beings? To answer this question, it will be helpful to conduct a comparative survey of the copulatory postures used by the non-human primates, and to enquire whether distinctive postures have arisen in particular families or genera of the lemurs, monkeys, and apes.

Although all the non-human primates make use of typical mammalian copulatory postures, involving rear entry by the male and dorso-ventral positioning, there are some interesting variations around this basic theme. For example, among the nocturnal prosim-ians, the lorisines, including the African potto and angwantibo as well as the slender and slow lorises of south east Asia, all copulate in an 'upside-down' position. This unusual copulatory posture is still basically a dorso-ventral one, but the female usually suspends herself beneath a branch before the male mounts her (Figure 5.2). However, among the closely related galagines (bushbabies), mating occurs with the pair resting above the branch in the usual, upright position. The bushbabies are highly mobile animals; they use vertical clinging and leaping to traverse their home ranges and to avoid potential threats. The lorisines are very different, being anatomically specialized for slow-moving and cryptic behaviour. Their inverted mating postures may, therefore, represent part of their adaptations for gripping tightly to substrates and avoiding detection by predators. Despite the large geographical separation between the African and Asian lorisines, their copulatory postures are as distinctive, in evolutionary terms, as their locomotor and other anatomical specializations.

A similar diagnostic test of evolutionary relationships may be made by examining in detail the cop-ulatory postures of certain New World monkeys. Among the spider monkeys and woolly monkeys, which belong to the sub-family Atelinae, a remarkable 'leg-lock' posture occurs during copulation. The male mounts the female from the rear, but then places his legs over the female's thighs (Figure 5.3).

Mounts are prolonged in these monkeys, lasting 6-35 min in spider monkeys, for up to 18 min in woolly monkeys, and more than 8 min in muriquis (woolly spider monkeys). The evolution of the leglock may be connected with prolonged patterns of copulation in these large-bodied monkeys. The posture allows the male to sit snugly behind the female, holding her in position. Both sexes also use their prehensile tails to anchor themselves to branches during extended copulatory bouts. The howler monkeys also belong to the Atelinae but they do not

Otolemur crassicaudatus O. garnettii Galagoides demidovii G. zanzibaricus G. alleni

Galago elegantulus G. moholi G. senegalensis Nycticebus coucang 0 N. pygmaeus Loris tardigradus Perodicticus potto £ Arctocebus calabarensis Lepilemur ruficaudatus L. mustelinus Cheirogaleus medius C. major Mirza coquereli Microcebu rufus M. murinus Allocebus trichotis Avahi laniger

Daubentonia madagascariensis Tarsius bancanus T. spectrum T. dianae T. syrichta

Figure 5.2 Relationships between phylogeny and copulatory postures in nocturnal prosimian primates. The inverted copulatory posture occurs in the lorisines of Africa and Asia and is likely to represent an ancient behavioural trait for this group. One of the Malagasy lemurs (the aye-aye, Daubentonia) may also copulate in an inverted ('upside down') position. Source. The phylogeny is adapted from Kappeler (1995). The illustration of slender lorises mating is from Schulze and Meier (1995).

Alouatta palliata (including coibensis)

Alouatta pigra

Alouatta seniculus

Alouatta sara

Alouatta macconelli

Alouatta caraya

Alouatta belzebul

Alouatta guariba

Ateles paniscus

Ateles belzebuth (including marginatus and chamek)

Ateles geoffroyi (including fusciceps)

Ateles hybridus

Brachyteles arachnoides

Brachyteles hypoxanthus

Lagothrix cana

Lagothrix lagotricha

Lagothrix lugens

Lagothrix poeppigii

Figure 5.3 Phylogeny of the South American ateline monkeys, and occurrences of the specialized 'leg-lock' copulatory posture in members of three genera (Ateles, Brachyteles, and Lagothrix). Source: The phylogeny is from Di Fiore and Campbell (2007). The illustrations of copulation in Ateles are from Dixson (1998a), after Klein (1971).

copulate for prolonged periods, nor do they exhibit the leg-lock mating specialization (Figure 5.3). None of the other New World primates has been observed to use leg-lock mounting postures.

As regards the hominoids, it is significant that although the apes often copulate in the typical primate (i.e. dorso-ventral) manner, ventro-ventral or female superior copulatory postures have also been recorded in various species, both in the wild or in captivity. Few records are available for gibbons; however, Koyama (1971) observed ventro-ventral copulation in free-ranging siamangs (Hylobates (Symphalangus) syndactylus) at Fraser's hill, in Malaysia. Among the great apes, there have been numerous accounts of ventro-ventral or female superior mating postures. Rijksen (1978), for example, recorded wild Sumatran orangutans mating in a variety of such positions, in association with their versatile quadrumanous climbing and suspensory behaviour. The male orangutan sometimes reclines on his back, with his penis erect, as a sexual invitation to the female. The female may then initiate intromission, by sitting in the male's lap, facing towards him, and making pelvic thrusting movements (Figure 5.4). Schurmann (1982) has observed this kind of behaviour in wild orangutans. In captive Bornean orangutans, Nadler (1977; 1988)

Figure 5.4 The pre-copulatory penile display and female superior copulatory posture of the orangutan (Pongo pygmaeus). Source: From Dixson (1998a), after Nadler (1988).

found that the male pattern of reclining and penile display occurs most often in situations where females have some control over mating interactions. Nadler fixed a barrier between the male and female cages, such that only the smaller female orangutan could pass underneath and gain access to her partner. During these restricted access pair tests, females were much more likely to initiate copulation at mid-menstrual cycle, and males reclined, displayed, and invited females to approach and mount them.

Turning to the African apes, the pigmy chimpanzee (bonobo) mates in both dorso-ventral and ventro-ventral positions. The common chimpanzee mates only in the dorso-ventral position, at least as far as is known from field observations of several populations in eastern and western Africa (Goodall 1986; Boesch and Boesch-Achermann 2000). Ventro-ventral copulations have been observed in both freeranging and captive bonobos; the ventro-ventral pattern may be more typical of sub-adult or young adult animals (Figure 5.5). In studies conducted in the Lomako forest (in what was formerly Zaire), 26 per cent of the seventy copulations observed by Thompson-Handler et al. (1984) took place with the partners facing each other. The majority of the matings were of the usual, dorso-ventral type. Takayoshi Kano's (1992) more extensive field studies of bonobo behaviour, at Wamba, revealed that every copulation is invariably preceded by female presentation, which takes two forms. In one form the female stands quadrupedally; this is followed by dorso-ventral copulation. In the other form, the female lies on her back in front of the male, spreads her thighs, raises her buttocks, adjusts herself and shows her sexual organs; the male approaches and copulates ventro-ventrally.

Kano also found that ventro-ventral copulations were less frequent (29.1 per cent of observations) than dorso-ventral ones, and 'more frequent in male and female adolescents than in full adults'. Ventro-ventral mounts also occurred frequently between female bonobos, the partners embracing face to face and thrusting their genitalia together (the so-called G-G rubbing display: Figure 5.5).

Western lowland gorillas have occasionally been observed to mate face-to-face, although the majority of their copulations take place in the dorso-ventral position (Figure 5.6). Thus, a number of authors, including Schaller (1963), Hess (1973), and Nadler

Figure 5.5 (A). Ventro-ventral copulatory posture of the bonobo (Pan paniscus). (B). Two female bonobos embrace, and engage in 'G-G rubbing'.

Source: Author's drawings, from photographs by De Waal (2003).

Figure 5.5 (A). Ventro-ventral copulatory posture of the bonobo (Pan paniscus). (B). Two female bonobos embrace, and engage in 'G-G rubbing'.

Source: Author's drawings, from photographs by De Waal (2003).

How Gorillas Mate

(1980) provide descriptions and illustrations of captive western lowland gorillas mating in these ways. Although Schaller observed only two copulations in mountain gorillas, he supplemented his study by observing the behaviour of captive western lowland gorillas at the Columbus Zoo. These animals occasionally exhibited ventro-ventral patterns of copulation. More recently, it has been possible to observe western lowland gorillas in the Congo, in an area where groups emerge into open, swampy areas to feed. Copulation in a face-to-face, seated posture has recently been photographed there. For the mountain gorilla, detailed information has been provided by Harcourt et al. (1980). All sixty-nine copulations recorded by Harcourt and his colleagues in the Virungas National Park involved dorso-ventral postures, 'although twice one pair briefly assumed the ventro-ventral position before turning to copulate normally.' Same-sex mounting has also been described in male mountain gorillas and Yamagiwa (2006) includes illustrations of both dorso-ventral and ventro-ventral postures adopted by these males. Overall, 16 per cent of male-male mounts were of the ventro-ventral type.

The phylogenetic distribution of various types of copulatory postures among the extant prosimians,

Copulatory Man Photo

Figure 5.6 Copulatory postures in captive western lowland gorillas (Gorilla g. gorilla). Left: A female invites mating by backing towards a male, and the male mounts in a dorso-ventral position. Right: The less-frequently used ventro-ventral position. Source: Photos by Dr. R.D. Nadler.

monkeys, apes, and humans is shown in Figure 5.7. The greater versatility of copulatory positioning, and use of ventro-ventral positions by the apes (and especially by the great apes) and humans probably springs from several causes. Firstly, as was suggested long ago by Bingham (1928), the increased brain development and intelligence of apes may be associated with a reduced reliance upon stereotyped cop-ulatory patterns and a closer resemblance to human patterns of behaviour. The progressive enlargement of the brain which has occurred throughout homi-nid evolution has already been discussed in Chapter 1 (see Figure 1.10). A reduced reliance upon stereotyped copulatory patterns would likely have occurred in the australopithecines and in forms such as Homo ergaster. Secondly, it may also be important to consider that face-to-face patterns of copulation facilitate eye contact and continued facial communication between partners during mating. Eye contact plays an important role during pre-copulatory behaviour in many anthropoids. Female monkeys of various species frequently attempt to look back at males during dorso-ventral copulations (Dixson 1998a). Such communication is greatly facilitated during ventro-ventral copulation, however, as has been noted for orangutans, bonobos, and gorillas (Nadler 1980; 1988; Schurmann 1982; Kano 1992).

Finally, I suggest that the propensity for apes and humans to engage in face-to-face copulatory postures has been greatly facilitated by anatomical specializations which originated in arboreal ancestors. The apes have a long evolutionary history of using suspensory postures, as well as arm-over-arm swinging forms of locomotion (brachiation) in arboreal environments. Although brachiation is best developed in the gibbons, the orangutan also brachiates slowly and the African apes occasionally do so, although they are specialized for terrestrial patterns of locomotion (knuckle walking). Homo sapiens descended from arboreal, ape-like ancestors, and shares with apes many anatomical features of the shoulder joints, rib cage, and fore-limbs. Australopithecus afarensis, for example, had long arms and curved fingers; this ape-like hominid probably climbed and suspended itself below the branches efficiently, as well as walking bipedally on the ground. Humans, like the apes, have broad, flat chests and mobile shoulder joints allowing a greater range of arm movement than is possible for quadrupeds, such

Primate copulatory postures

Primate copulatory postures

| | Dorso-ventral J Modified dorso-ventral Ventro-ventral

Figure 5.7 Phylogenetic relationships between the six extant superfamilies of the Order Primates, together with the distribution of various copulatory postures throughout the order. The basic mammalian dorso-ventral copulatory posture occurs in all six superfamilies. Specialized variants of this position occur in the lorisines, and in the aye-aye (inverted postures) and the atelines among the cebid monkeys (leg-lock postures). Ventro-ventral postures have been recorded in the great apes, in humans, and (much less frequently) in gibbons.

as monkeys. The use of flexible, suspensory postures may have facilitated the emergence of ventro-ventral and female superior copulatory positions during hominoid evolution. Animals which habitually hang, or swing by their arms whilst foraging might also suspend themselves in this way during mating. This is frequently the case in orangutans, and may explain the retention of ventro-ventral postures in apes which are now more terrestrial, such as the bonobo. Human beings may therefore have inherited a propensity to mate in face-to-face positions from remote ape-like ancestors. Add to this predisposition the marked lengthening of the lower limbs which occurred during human evolution, and a shift from dorso-ventral to more frequent use of ventro-ventral positions during intercourse might then have become established.

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