material technologies that we know today. But many animals, especially primates, also use inanimate objects to manipulate or affect things in their environment in ways that can be seen as precursors to similar activities in human beings. Over 20 different types of tool use have been identified in primates and other species—Common Chimpanzees, for example, employ objects as weapons, as levers, and as drinking and feeding implements of various sorts (such as the well-known example of sticks being used to capture and eat termites or ants). Tools can also be used to affect an animal’s own (or another’s) body, for example as part of a “hygiene” or grooming regimen. Chimpanzees and other primates, for example, often use leaves, twigs, straw, rags, or other objects to clean themselves and wipe away bodily secretions (such as saliva, blood, semen, feces, and urine). Chimps and Savanna Baboons have also been observed using sticks, twigs, and stones to clean their own or each other’s teeth (and even perform dental extractions). Chimps also sometimes tickle themselves with various items such as stones or sticks, and Japanese Macaques occasionally use similar items to groom one another.60
Less well known, however, is the use of objects for purposes of sexual stimulation. A number of primates employ various implements as masturbatory aids (in both the wild and captivity), and this aspect of tool culture has not received widespread attention in discussions of the development of animal and human object manipulation. Female Orang-utans, for instance, sometimes masturbate by rubbing objects on the clitoris or inserting them into the vagina; tools used for this purpose include pieces of liana bitten off to an appropriate size or (in captivity) pieces of wire. Male Orangs also use objects to stimulate their genitals, including one individual who ingeniously fashioned an implement by pushing a hole through a leaf with his finger. He inserted his erect penis into this “orifice,” then rubbed the leaf up and down the shaft to stimulate himself. Males also sometimes hold a piece of fruit (such as an orange peel) in their hand and masturbate against it.61
Common Chimpanzees have also developed several innovative masturbation techniques using a variety of different tools. One female gathered a small collection of sticks, pebbles, and leaves, from which she would carefully select a particular item to stimulate herself with. By placing a leaf underneath her vulva, for example, and flicking the stem with her knuckle, she made the leaf vibrate and thereby externally stimulate her genitals. She also repeatedly inserted the stem into her vagina, often lubricating it with saliva and manipulating it with her hand so as to stimulate herself internally. In one instance, she rocked back and forth with the stem inserted, rubbing the leaf against a vertical surface so that the stem actually vibrated inside her. On other occasions, she repeatedly inserted and withdrew a pebble from her vagina or used a small stick to stimulate her genitals. Other female Chimps have also been observed rubbing or tickling their external genitals with items or inserting them into the vagina, including pieces of mango, twigs, and leaves, as well as man-made objects such as small boxes or balls. Similarly, several young males assembled collections of stones, fruits, or even pieces of dried dung, which they would thrust against to stimulate their genitals. Male and female Bonobos occasionally employ inanimate objects for masturbation as well, stimulating themselves with (or thrusting against) branches, wood shavings, and other items.62
Like Orang-utans, one female Bonnet Macaque invented some relatively sophisticated techniques of tool manufacture, regularly employing five specific methods to create or modify natural objects for insertion into her vagina. For example, she stripped dry eucalyptus leaves of their foliage with her fingers or teeth and then broke the midrib into a piece less than an inch long. She also slit dry acacia leaves in half lengthwise (using only a single half) and fashioned short sticks by breaking longer ones into several pieces or detaching portions of a branch. Implements were also sometimes vigorously rubbed with her fingers or between her palms prior to being inserted into her vagina, and twigs, leaves, or grass blades were occasionally used unmodified.63
The use and manufacture of tools by primates is considered an important example of cultural behavior in animals, and a forerunner of the activities that are so widespread among human beings. Although many different forms and functions are evident in animal tool use, these examples show that nonreproductive sexual activities are part of the overall behavioral pattern: the primate capacity for object manipulation extends seamlessly into the sexual sphere. Apes and monkeys use a variety of objects to masturbate with and even deliberately create implements for sexual stimulation by cutting or forming materials such as leaves or twigs (often in highly creative ways). Similar types of activities occur among people, of course, and sexual implements of various sorts have a long and distinguished history in human culture. Dildos or phalli made of stone, terra-cotta, wood, or leather, for example, were used in ceremonial “deflowering” and fertility rites—as well as for masturbation and inducing sexual pleasure in a partner—in ancient Egypt, Rome, Greece, India, Japan, and Europe. Examples have been recorded from at least as far back as the Paleolithic through medieval times—including some biblical references—as well as in the ongoing traditions of many indigenous peoples throughout the world.64 However, few (if any) anthropologists have ever considered the possibility that sexual stimulation may have been a component of tool use among early humans or even played a part in the origin and elaboration of material culture. Of course, technological complexity is not the only measure of cultural development—some of the most complex linguistic and oral history traditions, for example, are to be found among the South African San peoples and the Australian Aborigines, whose material culture is relatively simple. And certainly many more “utilitarian” functions can be identified in the development of tool use among our human, protohuman, and primate ancestors. Nevertheless, the pursuit of sexual pleasure may have contributed, in some measure, to our own heritage as creatures whose tool-using practices are among the most polymorphous of any primate.
Taboo
The vast majority of human cultures prohibit sexual relations between people who are related. There is still ongoing debate among scientists as to whether this prohibition—commonly known as the incest taboo—is instinctual or learned. Regardless of the extent to which biological factors are involved, there are clearly strong social and cultural components to incest avoidance. Different human cultures and societies vary widely in how they define incestuous relations and to what extent such activities are both stigmatized and practiced. For example, although parental incest (father-daughter, mother-son) is prohibited in virtually all societies (yet still occurs, despite such prohibition, with varying frequencies), there is wider latitude regarding other blood relations. Cousin marriage is considered acceptable in some cases, unacceptable in others, while some societies make a further distinction between relations with cross cousins as opposed to parallel cousins—a biologically arbitrary distinction, since there is no evidence of any greater genetic “harm” in one form of cousin marriage than another. Brother-sister marriage was widely practiced in ancient Roman Egypt, and among the royal families of some central African and Balinese societies, ancient Incans, Hawaiians, Iranians, and Egyptians—in fact, Cleopatra is thought to have been the product of 11 generations of incestuous marriages within the Ptolemaic dynasty.65
Further evidence of a learned or cultural component to incest prohibitions relates to the role played by social familiarity as opposed to genetic relatedness in choice of partners. In our culture, sexual relations between adoptive or stepfamily members are generally frowned upon even though the individuals involved are not related by blood. Conversely, people who are genetically related but, because of social circumstance (e.g., separation at birth), are unaware of their biological connection may develop a relationship (at least until they learn of their relatedness). Other societies vary considerably in this regard: in the Israeli kibbutzim, for instance, unrelated individuals who are brought up together hardly ever marry one another. In contrast, a traditional form of Taiwanese marriage involved girls being adopted into families as children and then, on reaching adulthood, marrying their stepbrothers, although such marriages were considered less preferable than other arrangements. Among the Arapesh people of New Guinea, a similar practice of stepsister marriage was widely accepted and preferred.
The fact that homosexual relations are usually prohibited between related individuals also points to the importance of nonbiological factors in the incest taboo. In most human cultures that “permit” some form of same- sex eroticism, from contemporary America to indigenous tribes of New Guinea, the choice of homosexual partners is subject to distinctions of “kin” and “nonkin.” This is in spite of the fact that no children, and hence no potentially harmful genetic effects, can result from such unions. Typically the same restrictions are applied to homosexual as to heterosexual relations. In a number of New Guinean societies, however, slightly different kinship constraints regulate the choice of same-sex and opposite-sex partners. In fact, homosexual partners in some tribes are actually required to be
