Interdisciplinary Study Of Nonhuman Primates Gains Ground

Date: May 11, 1998 Author: Steve Bunk Do apes have feelings? Do they recognize and understand emotions? Behavioral and biomedical scientists are beginning to put aside old differences concerning such questions and combine their efforts to shed new light on what nonhuman primates may reveal about human evolution. A national leader in this emerging interdisciplinary approach is the Yerkes Regional Primate Research Center at Emory University in Atlanta. In September of 1977, the university established a Living Links Center (LLC) at the Yerkes field station in Lawrenceville, Ga. Relying on the expertise of Emory faculty and visiting scientists in such fields as ethology, comparative psychology, molecular biology, anthropology, and neuroscience, the center examines evolutionary connections between humans and their closest living relatives. The origins of sociality, self-awareness, numeracy, language, and even morality in nonhuman primates are being investigated. Work is under way on sequencing the chimpanzee genome, and studies of great ape brains draw on such technology as MRI and PET scans, as well as electron and confocal microsocopy. PRIMAL BONDS: University of Pennsylvania psychologist Ryne A. Palombit, a specialist in nonhuman primate bonding, introduces his child to some research subjects. The center's director, C.H. Candler professor of primate behavior Frans B.M. de Waal, is fond of pointing out that human nuclear DNA appears to be 98.4 percent identical to chimpanzee DNA. Part of the reason for the establishment of the center, he suggests, is that advances in behavioral research have helped to radically change scientific opinion in recent years about differences between humans and nonhuman primates. "In the 1970s," he recalls, "you would get beaten up as a scientist if you said anything about sex differences in animal behavior, for instance, because humans were cultural and everything in animals was instinctive." Nowadays, "we know chimpanzees have warfare, some form of political system, and democracy--so that low-ranking individuals can determine to some extent who will be the high-ranking individuals." With a nonhuman primate population of about 3,000, Yerkes is the largest of seven regional primate centers funded by the National Institutes of Health. The other regional centers, each of which specializes in different aspects of biomedical research on primates, are the New England Regional Primate Research Center in Southborough, Mass., the Oregon Regional Primate Research Center in Beaverton, Ore., the University of California at Davis, Tulane University in New Orleans, the University of Washington in Seattle, and the University of Wisconsin at Madison. The other centers must restrict their studies of ape behavior primarily to chimpanzees, because Yerkes is the only research institute that owns representatives of all four great ape species: chimps, bonobos, gorillas, and orangutans. A relative oversupply in the United States of chimpanzees, combined with declining interest on economic and ethical grounds in using the animals for invasive research, have contributed to increased emphasis on noninvasively studying the great ape family. All the Yerkes LLC's research is noninvasive. Lisa Parr, an Emory University doctoral candidate in psychobiology, is following up the observational behavioral work of Frans de Waal and others by taking chimpanzees into the laboratory and devising decision-making experiments that will provide empirical evidence concerning their cognitive capabilities. She earned her master's degree last year with a thesis on the cognitive and perceptual mechanisms underlying recognition of faces and facial expressions in chimpanzees. A paper on these experiments is now in press for the Journal of Cognitive Science. Her research used a "matching-to-sample" format developed at Emory University's Yerkes Regional Primate Research Center in Lawrenceville, Ga. A photo of a chimpanzee unfamiliar to test subjects was projected, then replaced by two other chimp images, one of which was a different photograph of the first animal shown. The subjects used a joystick to point to the animal that had been shown twice, a task they achieved without difficulty. For her doctoral work, Parr is revising this method to develop a paradigm involving video clips that will determine if chimpanzees understand the meaning of their own facial expressions. Her method will go beyond merely requiring the subjects to match screaming faces. A video clip might show chimpanzees fighting, followed by asking the subjects to match screaming expressions with the image of a veterinarian approaching with a dart gun as opposed to, say, associating the screams with a picture of food. "It's a representational association because, normally, when the vet comes with a dart gun, there wouldn't be other screaming faces around," Parr explains. "This definitely will raise questions about the emotional lives animals have, and whether they are able to reflect on them." --SB A specialist in conflict resolution and reciprocity among chimpanzees, de Waal has authored several popular books on primate behavior. In one, he describes the first chimpanzee birth he ever witnessed. Unexpectedly, the entire Yerkes chimp colony of about 200 animals gathered in silence around the mother-to-be, who soon squatted and delivered the newborn into her own hands. The mother's closest companion, an elder female named Atlanta, screamed in reaction to the birth, embraced two other chimpanzees, and spent the next several weeks closely attending the mother and offspring. "It is quite possible that the emotional reaction of Atlanta (who has had quite a few infants of her own) reflected empathy, that is, identification with the understanding of what was happening to her friend," he concludes (F. B.M. de Waal, Good Natured: Origins of Right and Wrong in Humans and Other Animals, Harvard University Press, Cambridge, Mass., 1996, pages 19-20). If that observation seems to carry a hint of anthropomorphism, de Waal doesn't mind. "Anthropomorphism should be the default position," he declares. "If a chimpanzee is sitting in a corner looking sad after the loss of a child, we would call it depression in humans. So why not in chimpanzees? They're so close to us [genetically] that the assumption should be the default position, that we're more alike than different." Similarities between humans and nonhuman primates also are being pursued in interdisciplinary research at the NIH Laboratory of Comparative Ethology (LCE), part of the Bethesda, Md.-based National Institute of Child Health and Human Development. In the early 1980s, the lab began cooperating with the National Institute of Mental Health in developing animal models for psychopathological states such as anxiety and depression. This was followed by biological and behavioral studies of normal primate development, led by LCE chief Stephen J. Suomi. A body of evidence was compiled to show that levels of aggression in rhesus macaques covaried significantly with chronic cerebrospinal fluid (CSF) concentrations of 5-HIAA, the primary central metabolite of serotonin. "If you look developmentally, in terms of living conditions, sex differences, or individual differences, there's a correlation between aggression and levels of serotonin at certain times," Suomi says. He then discovered that researchers in the National Institute on Alcohol Abuse and Alcoholism had made similar findings concerning humans, showing that aggression is accompanied by relatively low serotonin levels. This led to cooperation between the organizations on a four-year, longitudinal study to produce a rhesus monkey model for behavioral features of early-onset alcohol abuse (J.D. Higley et al, Alcohol Clinical Experimental Research, 20:629-42 and 643-50, 1996). Suomi notes that emotion in animals is primarily noticeable in their bodily postures and expressions. "You see monkeys when they look happy or sad or excited or bored, and their behavior seems to parallel those emotions." He says the lab's researchers have shown pictures of infant monkeys to people who had never seen monkeys, and they were able to identify such elemental emotions as sadness, fear, and joy in the expressions and postures of the animals. "That speaks pretty strongly for the evolutionary basis of these early emotions," he thinks. However, more complex emotions such as guilt and envy do not appear in humans until age two or three, and it is not known if monkeys ever develop the capacity for these feelings. "There are two basic competing theories [about emotion] and at the risk of oversimplifying, one theory is that all the emotions you need are what you see at birth, and they only get more complex or elaborate," Suomi says. The second theory is that some emotions, such as anger, change substantially with the development of cognition from infancy to adulthood. Determining which theory is more accurate may have "interesting implications for the measurement of emotion," he suggests. "It may drive the search for commonality or for differences in the physical concomitants of that emotion." He adds that measuring the physical states accompanying emotion is much easier with current technology than in the past. And he thinks that major advances yet to come in understanding the interrelationship between genes and behavior will build even stronger bridges between the biomedical and behavioral disciplines. "It's one thing to identify genes involved in some forms of behavior, but in many cases, what's turning them on and off are environmental influences," he remarks. A key aspect of environmental influences on nonhuman primates is the social relationships of females. Analysis of cooperation or competition between them, and of the quality of their relationships with their offspring and with males, is essential to understanding the societal dynamics of each species. A socioecological model of study now gaining wide acceptance is based on the combined importance of ecological factors, habitat saturation and competition for food, and the need for mothers to prevent infanticide by males other than the fathers of their young (E.H.M. Sterck et al., Behavioral Ecology and Sociobiology, 41:291-309, 1997). Ryne A. Palombit, a psychology postdoc researcher at the University of Pennsylvania in Philadelphia, studies the evolutionary bases of variation in male-female social relationships, including gibbons and siamangs in Indonesia, chacma baboons in Botswana, and titi and sati monkeys in South America. He says the classic economic model for human pair-bonding, based on mutually cooperative provisioning, has predominated in studying nonhuman primates. But various field studies over recent years have led to the anti-infanticide hypothesis. "Males and females may differ in how they maximize their reproductive success," Palombit notes. Based on work by other researchers and his own field studies, he believes that gibbon bonding probably is not motivated by protection from infanticide, but that baboon bonding probably is. During a two-year study of a chacma baboon population, he found that infanticide accounted for at least 38 percent of infant mortality. All the observed killings were by newly immigrant adult males that had attained the alpha position in the hierarchy. The death of an infant speeded the resumption of the mother's menstrual cycle, thus enabling the new alpha male to copulate with her (R.A. Palombit et al., Animal Behavior, 54:599-614, 1997). Living Links Center Yerkes Regional Primate Research Center Emory University 954 N. Gatewood Rd. Atlanta, GA 30329 Tel: (404) 727-7721 * Fax: (404) 727-7845 http://www.emory.edu/LIVING_LINKS Laboratory of Comparative Ethology National Institute of Child Health and Human Development Bldg. 31, Room B2-B15 9000 Rockville Pike Bethesda, Md. 20892 Tel: (301) 496-9550 * Fax: (301) 496-0630 http://www.nih.gov/nichd/ He says of the infanticide theory, "The value of this framework will be to help explain what people do." Although most infanticide in humans is done by a parent and therefore does not correspond to the animal model, Palombit says the primate work can help to fit human characteristics such as sexual jealousy and suppression of infidelity into a similar model of conflict. However, he cautions, "We need to be careful not to accept what seems intuitively obvious without looking carefully at data to support it." Data is something of a sore point with Barbara King, an associate professor of anthropology at the College of William and Mary who researches primate behavior and the evolution of communication and cognition. "I have felt very pushed as an anthropologist to get lots of quantitative information," she says. "We do need that, but I'm concentrating first entirely on observing natural patterns unfolding." By videotaping a captive bonobo and her infant in the Language Research Center at Georgia State University in Atlanta, King has identified structured movements, touches, and gestures that she calls "patterned interactions." Through these repeated routines, she believes the mother structures her infant's experience of the world and thereby creates meaning. This process of "social information donation" occurs in the great apes and rarely in the lower nonhuman primates, she says. "After 1,013 hours of watching baboons in the wild, I know the mothers did not structure their infants' learning." Such observations have led King to a theory that the roots of human language are not found in the vocalizations of nonhuman primates but in their socially directed body movements and actions. The patterned interactions she has found in bonobos may be an evolutionary forerunner of the structured routines in human learning behavior, she thinks. King emphasizes that she is not challenging the dominant scientific view of language as a biological specialization unique to humans. "It's vital not to get stuck on the question of whether other primates have language. That's a sexy topic and it provides good media headlines, but it is a polarizing question, and we don't need to stop there. If we go beyond that topic, then people on different sides of the question might really be able to talk."

Interdisciplinary Study Of Nonhuman Primates Gains Ground

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