A Comparison of Some Similar Chimpanzee and Human Behaviors
Description: Aggressive behavior is typical of most primates. Gorillas, humans and chimpanzees kill members of their own species. The need for social and physical contact is also characteristic of most primates. Species that live in groups need to reconcile aggression. Social groups require some form of conflict resolution. Sexual behavior is one such mechanism to overwhelm aggression.
Bonobo sex life is divorced from reproduction and also serves the functions of pleasure and conflict resolution. Females are in a sexually attractive state most of the time, and almost continuously sexually active. Sexual activity is very frequent. Males, females and juveniles all engage in erotic activity. Age and gender are not sexual boundaries among the Bonobo. A typical sexual pattern is genital rubbing between adult females. Erotic contacts in Bonobos includes oral sex, genital massage and intense tongue-kissing.
Whereas in most other species sexual behavior is a fairly distinct category, in the Bonobo it is part and parcel of social relations. Sex seems to cement Bonobo bonds. Females use sex to form alliances against males. Consequently males do not dominate females or coerce them sexually. Bonobo culture is female-centered, egalitarian and substitutes sex for aggression.
Context: Bonobos live in groups of 50 to 120 animals. Bonobo society appears to be female-dominated. Male status is linked to that of his mother. Older females occupy the highest rank. The strongest social bonds are between females. Raising offspring is an exclusively female activity.
In Bonobo society sexual excitement and aggression rates are higher at feeding times. Dominant males may delay sharing food with females who are not sexually disposed. Cofeeding takes place between intimates. Among Bonobos, embracing, friendly touching and sexual contact rates jump after an aggressive incident. According to zoologist Frans de Waal, "The majority of mounts and matings occur in tense situations." "(C)onflict resolution is the more fundamental and pervasive function of Bonobo sex." Sex in Bonobo society is definitively a mechanism for keeping the peace.
Bonobo-Human Comparisons: Human nuclear families are presumably incongruous with the sex habits found in Bonobo culture. Many of the roots of human behavior can be traced to our primate heritage, including survival through cooperation and mutual assistance. While the same mechanisms and purposes may underlie Bonobo and human social behavior, distinct solutions have evolved in these two groups. In particular, humans and Bonobos have developed different mechanisms for peacekeeping. Cultural transmission and highly developed symbolic language are particularly unique to humans. Human conflicts and aggression are typically reconciled and avoided through language.
The use of sex to reconcile or avoid conflict is present in human culture, though it is nowhere near as pervasive a factor as among the Bonobos. Conflicts are less likely to recur after body contact between aggressors. This similarity to Bonobo use of sex can be seen in the custom of adversaries shaking hands after conflict, or close friends kissing and making up after a fight. Intimate human couples engage in sexual activity after conflicts. Sexual receptivity maintains pair bonding in humans much as it does group cohesion in Bonobos.
Unlike Bonobos, sexual control is evidenced in humans. Marriage typically serves as a sexual control mechanism. Human males participate in child rearing and, due to monogamous marriages, have some assurance of paternity. In most cultures men honor proprietary rights of husbands over their wife or wives. Marriage typically involves exclusion and control over a female's sexual life. Humans also demonstrate sexual coercion and jealousy between intimates. Most human cultures are male-dominated.
Description: Apes are physically unable to produce human speech, so investigation of their ability for symbolic communication has been difficult. Gardner and Gardner taught American Sign Language (ASL) to Washoe, and subsequently to four other chimpanzees. Washoe's instruction began at age one and continued for five years. Washoe learned 132 signs and formed novel combinations of signs. Other researchers, notably Francine Patterson and Roger Fouts, also instructed Chimpanzees to use ASL. E. Sue Savage-Rumbaugh, in the Animal Model Project, improved on the ASL system with lexigrams and a symbol keyboard system (accompanied by special lighting on the keyboard, image projection and accompanying sounds to correspond to the symbols).
Savage-Rumbaugh taught two chimps, Austin and Sherman, lexigrams to symbolize tools needed to acquire food, among other symbols. Using only the lexigrams, Austin and Sherman had to communicate which tool was required to access food. Their success rate was 97 percent correct when the keyboard with lexigrams was available, and dropped to 10 percent with the keyboard turned off. This established that their communication was indeed symbolic. Sherman and Austin had learned to communicate with each other through the use of learned symbols in the setting of cooperation to obtain food. These experiments established that chimpanzees are capable of acquiring or learning symbolic communication.
Context: The benefits of communication can be learned along with an awareness of the benefits derived therefrom, such as success in food acquisition. Austin and Sherman learned to communicate symbolically in a human experimental setting. They have shown the cognitive capacity to realize that communication can alter the behavior of others, and they used this capability to obtain food. We cannot as easily ascertain if symbolic communication occurs in ape societies in the wild. We know that vocalizations are an important aspect of chimpanzee life, yet we have no proof that they are employed in a highly symbolic fashion as is the case with human language.
Human Comparisons: The human mind evolved from the earlier hominid mind, and that diverged from the ape mind. Human cognitive processes had their direct antecedent in the ape brain. Chimpanzees resemble humans more than any other animal with regard to mental processes. Except in regard to size, human brains are very alike to chimpanzee brains. The major differences between humans and apes are not anatomical, but rather behavioral. The most significant behavioral difference in humans is the complex uses of objects and language. Human children refer to items in a representational manner at an early age. Chimpanzees do not show this behavior. This does not imply a lack in apes of the cognitive abilities which facilitate this behavior in humans.
Humans definitely use symbolic communication to acquire food and other resources. We have the cognitive capacity to realize that communication can alter the behavior of others at an age before we can uttering one word sentences. We very readily understand that saying, "Please pass the salsa," alters the behavior of others.
In humans the capacity for symbolic communication has evolved to surpass the level of this capacity in our ape cousins. Our reasons for and use of symbolic communication is far greater and more diverse than in the apes, to the best of our knowledge. If symbolic vocalizations occur at all among apes, only an understanding of primate vocalizations can enlighten us of the actual degree of this important difference between our species.
A cooperative resource sharing strategy and group planning in our common ape ancestors probably fueled reproductive success and evolution to greater mental capacities related to communication and language in humans. Our very evolution evidences the ability for symbolic communication in humans.
Medicinal Plant Usage
Description: Detailed evidence for the use of medicinal plants in the chimpanzee has been recently documented (Huffman). Chimpanzees are susceptible to parasites that also infect humans. Parasite study identified nematodes, trematodes and protozoae as chimpanzee parasites. Two types of medicinal plant use, whole leaf-swallowing and bitter pith chewing are known in chimpanzees.
Sixteen plant species of possible medical use have been observed and identified to be ingested by chimpanzees across equatorial Africa. This behavior has also been observed in the Bonobo and the eastern lowland gorilla. Analysis of the feces collected from individuals observed leaf-swallowing revealed that they were suffering from parasite infections. Plant specimens were collected concurrently with observations of their use. The chemical and physical properties of the plants were analyzed. In some cases worms were expelled with leaves. Some of the worms were actually firmly stuck to the surface of the leaf. Anti-parasite activity due to chemicals produced by these plants (whole leaf swallowing) was ruled out. Short hairs located on the leaves appear to be responsible for the eviction of the parasites. Chimpanzees select these plant species for their physical, roughness properties, resulting in the physical purging action of adult parasites by the leaves. Thus whole leaf swallowing is one self-medication strategy used by chimpanzees against gastrointestinal parasites.
Bitter leaf-chewing is another method. Infection of parasites drops noticeably after chewing of Vernonia amygdalina pith. Chemical analyses has revealed sesquiterpene lactones and new steroid glucosides with antiparasitic activity against Schistosoma, Plasmodium and Leishmania.
Context: Field observations have shown that ill chimpanzees consume the remedial plants. Incidence of the medicinal plant use is higher during the rainy season when parasite infections are also at their highest. Chimpanzees have learned to distinguish between harmful plant parts and parts that contain beneficial compounds. This behavior is learned from other group members, which allows the group to benefit from the experience of an individual.
Human Comparisons: The WaTongwe people also traditionally use V. amygdalina as a treatment for similar symptoms. Among other African peoples this plant is used for stomach aches and parasite infections. The leaves of a domesticated variety is used as a food in order to restore stamina. This is one example of the pervasive use of medicinal plants among humans. The chimpanzee practice of parasite removal by use of the physical properties of leaves has not been documented among humans.
Many populations in the Amazon Basin use Banisteriopsis for its purgative and evacuative effect, an analogous activity with a somewhat different mechanism and more profound side effects. While living in the Amazon basin this author also discovered the use of a tea with anesthetic properties to be totally efficacious in curing an infection which was likely amoebic dysentery. The active ingredient was found in the root bark of a small plant.
Most interestingly, it is possible to acquire new medicines and new medical techniques for humans by watching the behavior of sick animals.
de Waal, Frans, Peacemaking among Primates, Harvard University Press, Cambridge, Massachusetts, 1989.
de Waal, Frans B. M., Bonobo Sex and Society, Scientific American, March 1995, pp. 82-88, accessed via: http://soong.club.cc.cmu.edu/~julie/bonobos.html.
Huffman, Michael A., The Medicinal Use of Plants by Chimpanzees in the Wild, Primate Research Institute, Kyoto University, Japan, http://jinrui.zool.kyoto-u.ac.jp/CHIMPP/CHIMPP.html.
Jacobs, James Q., A Brief Note Regarding Campa Medical Practices, http://www.jqjacobs.net/writing/ethnomed.html
Primate Behavior, http://www.leeds.ac.uk/chb/lectures/anthl_11.html.
Pan paniscus, Bonobo or pygmy chimpanzee, Animal Diversity Web, University of Michigan, http://www.oit.itd.umich.edu/projects/ADW/.
Pan troglodytes. Chimpanzee, Animal Diversity Web, University of Michigan, http://www.oit.itd.umich.edu/projects/ADW/.
Savage-Rumbaugh, E. Sue, Ape Language, Columbia University Press, New York, 1986.
Smuts, Barbara, Commentary - Apes of Wrath, Discover Magazine, August 1995.
The Evolution of Morality, Yerkes Regional Primate Research Center, http://www.emory.edu:80/YERKES/NEWSROOM/dewaal.html, August 30, 1996.