The Hunting Apes: Meat Eating and the Origins of Human Behavior 9780691222080, 0691088888, 0691011605, 9780691088884

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THE HUNTING APES

Meat Eating and the Origins of Human Behavior CRAIG B. STANFORD

PRINCETON UNIVERSITY PRESS PRINCETON AND OXFORD

Copyright © 1999 by Princeton University Press Published by Princeton University Press, 41 William Street, Princeton, New Jersey 08540 In the United Kingdom: Princeton University Press, 3 Market Place, Woodstock, Oxfordshire OX201SY All Rights Reserved Second printing, and first paperback printing, 2001 Paperback ISBN 0-691-08888-8 The Library of Congress has cataloged the cloth edition of this book as follows Stanford, Craig B. (Craig Britton), 1956The hunting apes: meat eating and the origins of human behavior / Craig B. Stanford. p. cm. Includes bibliographical references and index. ISBN 0-691-01160-5 (cloth: alk. paper) 1. Apes—Behavior. 2. Apes—Food. 3. Human evolution. 4. Hunting and gathering societies. I. Title. QL737.P96S73 1999 599.88153-75%

Meat in Diet?

Small mammals eaten regularly

*Lowland and mountain gorillas are presented separately because of their differences and because molecular evidence suggests they should be considered separate species. The same may be true for eastern and western chimpanzees and Sumatran and Bornean orangutans.

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Chapter 3

CHIMPANZEES

An early September morning in Gombe National Park in western Tanzania. A party of chimpanzees is on the move, traveling up a steep mountain slope toward a stand offruit trees. The group often animals had nested in the same trees the night before. As they approach the crest of the ridge and reach the ripe fruit, they begin to pant-hoot, the loud calls reverberating off the valley walls. These calls are answered from the valley below by another party also headed this way. The party contains four adult males plus females and their infants. One female carries a huge pink sexual swelling, a billboard of her sexual state. After twenty minutes of gorging on the fruits, the second party arrives, containing five more adult males including Wilkie, the current top-ranking alpha. An excited greeting display follows between the males, and Wilkie charges time and again up and down the slope dragging branches, his hair bristling as he chases other lower-ranking males out of his path. Meanwhile, another high-ranking male approaches the swollen female, a recently arrived immigrant from the adjacent community. When she does not immediately present herselffor mating, the male attacks her, chasing her to the top of a tree where they mate. Later, some members of the combined party depart, leaving a new mixture of chimpanzees behind. The parties continue to depart and recombine, making and remaking a jigsaw puzzle of associations throughout the day.

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Our understanding of chimpanzee society has evolved very slowly because of the difficulty in obtaining a clear portrait of their complex mating system. During the early 1960s it was widely held that chimpanzees, unlike other group-living primates that had been studied, had no group structure whatever and that relations among individuals were constantly changing. Jane Goodall had been conducting research in Gombe since 1960 and had pioneered the observational study of wild chimpanzees, discovering meat eating and tool use in the process. Working in the Mahale Mountains of Tanzania some 100 kilometers south of Gombe, the Japanese primatologist Toshisada Nishida described a chimpanzee society based on the "unitgroup" (later called the "community" by Western primatologists).3 The community is a local breeding population of anywhere from twenty to over one hundred chimpanzees; it occupies an area that is defended against intruders and has a stable membership within which there are no consistent grouping patterns except mothers and their immature offspring. The community members come together and depart unpredictably all day long. This complex sort of primate society is called fission-fusion, and it serves an ecological purpose for its members. The smallest irreducible unit of chimpanzee society is mothers and their infants, and foraging parties form to provide females with optimal fruit foraging

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opportunities. Small parties allow females to maximize their food intake by avoiding competition for fruit from other chimpanzees. Females who are sexually receptive seek out males or are sought by them to form larger parties. Party size in chimpanzees is therefore a function of both food patch size and the presence of sexually receptive females. It was learned through the slow accumulation of life histories that female chimpanzees, upon reaching puberty at about age twelve, usually migrate from the community of their birth into other communities to take up life as resident adult females. These females, when sexually swollen, mate with multiple males. The view that chimpanzee social systems are characterized by casual promiscuity thereby became entrenched, in spite of Goodall's early observations of intensely aggressive competition among males for estrous females. Maturing males, meanwhile, remain in their native land for life, bonding with other males to whom they are often related. Male chimpanzees tend to socialize with one another, and these alliances patrol the community's territorial borders and try to control females as well. At both Gombe and Mahale, lethal territoriality between neighboring communities, often called warfare (though the observed pattern was more a series of commando raids into neighboring communities), reinforced the view that chimpanzee society is male controlled from both

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