Recognizing Hominoid-Modified Bones: The Taphonomy of Colobus Bones Partially Digested by Free-Ranging Chimpanzees in the Kibale Forest, Uganda MARTHA TAPPEN 1 * AND RICHARD WRANGHAM 2 1 Department of Anthropology, University of Minnesota, Minneapolis, Minnesota 2 Department of Anthropology, Harvard University, Cambridge, Massachusetts KEY WORDS: meat-eating by chimpanzees; bone modification ABSTRACT We present a taphonomic study of bones that have passed though the digestive tracts of free-ranging chimpanzees from the Kibale Forest in Uganda. The bone assemblage can be characterized as having a very low species diversity; low number of identifiable specimens (NISP) per scat; bones extremely broken up (very small size range); skeletal part fre- quencies similar in some ways to those resulting from carnivore partial digestion; and sometimes articulated specimens. Modifications to the bones include corrosion, tiny tooth scores and pits, cracking, and fraying of bone edges. Together, these characteristics suggest that hominoid bone digestion may be recognizable, despite some similarities with leopard-, canid-, and eagle-modified bone. Chimpanzees are well-documented hunters of medium- sized vertebrates such as monkeys. This is significant in the study of human evolution if, as it seems, the last common ancestor of chimpanzees and humans was chimpanzee-like. It suggests there was a pre–stone-tool-using hunting phase in human evolution, perhaps by australopiths or the last common ancestor. Taphonomically, pre–stone tool meat eating has been very difficult to detect in the fossil record. However, if chimpanzees leave a recognizable taphonomic signature on the bones of their prey, we will be able to look for analogous signatures in fossil bones associated with fossil homi- noids and hominids. Am J Phys Anthropol 113:217–234, 2000. © 2000 Wiley-Liss, Inc. Across their geographic range, chimpan- zees have been found to prey on mammals. Although meat makes up a small percent- age of their diet, the fact that chimpanzees are hunters of vertebrates is significant in the study of human evolution, especially in light of the proposal that the last common ancestor of chimpanzees and humans was in many ways chimpanzee-like (e.g., Wood, 1994; Moore, 1996; Pilbeam, 1996; Wrang- ham and Peterson, 1996). Because chimpan- zees and humans are both hunters, the last common ancestor of the two also may have hunted (vertebrate predation would be ple- siomorphic for our clade (Tooby and DeVore, 1987; Foley, in press). Lately, most paleoan- thropologists have not regarded australo- piths as frequent hunters or meat eaters. The debate regarding australopiths as “the hunters or the hunted” is considered by many to have been basically resolved by the Grant sponsor: The University of Minnesota Grant in Aid of Research and McKnight Land-Grant Professorship provided funding for this research. *Correspondence to: Dr. Martha Tappen, Department of An- thropology, University of Minnesota, 395 HHH Center, 301 19 th Ave. S, Minneapolis, MN 55411. E-mail: tappe004@tc.umn.edu Received 12 July 1999; accepted 4 May 2000. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 113:217–234 (2000) © 2000 WILEY-LISS, INC.