By now you’ve probably heard the news: chimpanzees have been reported manufacturing, and using, spears (Gibbons 2007, Pruetz & Bertolani 2007). I’ll say that again. Chimps Pan troglodytes make and use spears….
Specifically, the chimps concerned are of the subspecies P. t. verus, a taxon that some researchers (Morin et al. 1994, 1995) have tentatively elevated to specific status. As reported in Current Biology by Jill Pruetz of Iowa State University and Paco Bertolani of the University of Cambridge, the observations concern the 35 chimps of the Fongoli site in Senegal. On more than 20 occasions between March 2005 and July 2006 the Fongoli chimps were observed to fashion wooden spears and then use them in hunting concealed bushbaby prey that were hiding in cavities in trees and branches. Unlike many of the tool-using chimps we are familiar with, such as the Gombe and Tai National Park chimps, the Fongoli chimps are not rainforest animals, but inhabit a grassland-woodland mosaic.
Tool use in chimps has been known about for several decades, and over the years the sorts of tools that chimps have been observed using have become increasingly sophisticated. Termite fishing was reported by Jane Goodall in the 1960s and the use of hammers and anvils to break open nuts became well known in the 1990s (Goodall 1968, Boesch et al. 1994). The adjacent image shows one of the Gombe chimps using a tool to catch termites: those who’ve read any of Goodall’s research will know the significance of the chimpanzee individual shown in the photo [image from here]. While there is one account in which a Tanzanian chimp was reported to use a tool to rouse a squirrel that was then killed and eaten (Huffman & Kalunde 1993), the manufacture and use of spears* is something very, very new. The chimps would break off a live branch, remove its twigs and leaves, and then form a sharpened point with their incisor teeth. The resultant tools averaged 60 cm in length.
* Some primatologists have already noted that use of the term ‘spear’ implies that the objects are thrown at prey, whereas the tools used by the Fongoli chimps are apparently used as stabbing weapons. There may, then, be some dispute over terminology.
The tools were deployed, not simply as probing devices as is the case when the chimps fish for termites, but as stabbing weapons that were thrust forcefully into the cavities. The spears were not used to extract the prey: from the description that Pruetz & Bertolani (2007) provide it seems that the bushbabies were killed within the cavity by the spear tip, and then extracted by hand. Only one successful kill was observed, and even in that case it could not be determined with certainty whether the spear was responsible for the death of the bushbaby. However, the evidence still looks pretty good.
The fact that chimps manufacture spears raises the possibility that such tools appeared much earlier within hominid history than we’ve thought until now. This ties in with recent work on archaeological sites, showing that chimps in what is now the Tai National Park have been using stone tools for thousands of years: a discovery which supports antiquity of tool use within hominids [adjacent image shows exacavated chimpanzee stone hammer, from here]. Pruetz & Bertolani (2007) draw attention to the fact that the Fongoli chimps are savannah-woodland inhabitants, apparently frequenting environments similar to those favoured by australopithecines and other close relatives of modern humans. It seems increasingly likely that the diversity of tools manufactured and used by australopithecines and other fossil hominids was higher than we can demonstrate from the fossil record, and the fact that female and immature chimps seem to be the primary makers and users of these tools suggests, significantly, that these are the animals that play the most important role in the early development of some tools.
This is pretty amazing stuff, and time constraints prevent me from writing more about it. National Geographic features the story here, and includes video clips of the chimps using their spears. The image at the top of the article is borrowed from National Geographic.
Coming next: proto-narwhals and beluwhals, and rhinogradentians (kidding).
Refs – –
Boesch, C., Marchesi, P., Marchesi, N., Fruth, B. & Joulian, F. 1994. Is nut cracking in wild chimpanzees a cultural behavior? Journal of Human Evolution 26, 325-338.
Gibbons, A. 2007. Spear-wielding chimps seen hunting bush babies. Science 315, 1063.
Goodall, J. 1968. The behaviour of free-living chimpanzees of the Gombe Stream Reserve. Animal Behaviour Monographs 1, 161-311.
Huffman, M. A. & Kalunde, S. M. 1993. Tool-assisted predation on a squirrel by a female chimpanzee in the Mahale Mountains, Tanzania. Primates 34, 93-98.
Morin, P. A., Moore, J. J., Chakraboty, R., Jin, L., Goodall, J. & Woodruff, D. S. 1994. Kin selection, social structure, and the evolution of chimpanzees. Science 265, 1193-1201.
– ., Moore, J. J. & Woodruff, D. S. 1995. Chimpanzee kinship: response. Science 268, 186-188.
Pruetz, J. D. & Bertolani, P. 2007. Savanna chimpanzees, Pan troglodytes verus, hunt with tools. Current Biology doi:10.1016/j.cub.2006.12.042