Laelaps

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An adult chimpanzee in Bossou, Guinea uses hammer and anvil stones to crack nuts as younger individuals look on. From Haslam et al., 2009.

ResearchBlogging.org

Before 1859 the idea that humans lived alongside the mammoths, ground sloths, and saber-toothed cats of the not-too-distant past was almost heretical. Not only was there no irrefutable evidence that our species stretched so far back in time, but the very notion that we could have survived alongside such imposing Pleistocene mammals strained credulity. Contrary to what might be immediately expected, however, it was not Darwin’s famous abstract On the Origin of Species that changed appraisals of human prehistory. Instead it was a collection of stone tools found mingled among the bones of extinct mammals found in deposits on either side of the English Channel.

The discovery of stone tools from places like Brixham Cave in England and France’s Somme Valley confirmed that industry was a very old human enterprise, and so some scholars naturally felt quite comfortable in giving out species the honorary title of “Man the Toolmaker.” The ability of our species to make and use tools clearly separated us from all other organisms, at least until it was discovered that chimpanzees, too, made and used tools. More than that, studies since the 1960′s have confirmed that different populations of chimpanzees have distinctive tool cultures affected by the contingencies of their surroundings, and a recent study published two years ago in PNAS illustrates that these cultures of tool use among non-human primates stretch back at least 4,300 years.

Since September of 1979 primatologists have studied the wild chimpanzees of the Tai National Park in the western African nation of Côte d’Ivoire, and in this particular location the chimpanzees use a variety of tools. Among the most common tools are twigs used to get at different kinds of food (be it honey in a tree or the brains of a monkey they have killed), but the Tai chimps also frequently use stone hammers and anvils to crack open nuts. Naturally this process modifies the stones used in the process, and this made some researchers wonder whether chimpanzees might have an archaeological record all their own.

To find out, scientists Julio Mercader, Huw Barton, Jason Gillespie, Jack Harris, Steven Kuhn, Robert Tyler, and Christophe Boesch looked for signs of ancient chimpanzee sites within the Tai forest. They found three, all of which were within about 200 meters of each other in an area of the park still inhabited by chimpanzees and dated to a span of time between 4,300 years ago and 2,200 years ago. From these sites the researchers gathered a large collection of modified stones, most of which (206 pieces) came from a single site, but the question was whether they were truly looking at a chimpanzee-made assemblage or one that had been artificially made by flowing water.

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A collection of stone tools created by chimpanzees and deposited between 4,300 and 2,200 years ago in what is now Tai National Forest. From Mercader et al., 2007.

In their study of the site the team found that the sediments in which the artifacts had been found were of a sort that would not be able to transport many bits of rock larger than a pebble. This suggested that the damaged stones really had been created by chimpanzees, but to make sure they were not being deceived three of the authors participated in a triple blind test in which stone tools were mixed among rocks that might look like tools but had actually been created by geological phenomena. This forced them to identify what characteristics distinguished a tool from a tool-shaped rock, and during the tests the researchers agreed on the identification of the tools 90% of the time. Based upon this test and the details of the stones it was highly likely that the identification of the tools was correct, but the proof that they had been actually used to crack nuts came from a different line of evidence.

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An young male chimpanzee in Bossou, Guinea carries a hammer and an anvil. In this way sites like the one uncovered in the Tai forest begin to be formed. From Haslam et al., 2009.

The stone tools the team found closely resembled those used by Tai chimpanzees to crack nuts today, and to investigate this idea they looked at whether any starch residues left by the nuts remained on the tools. They were in luck. Not only did the Tai tools preserve some of these residues, but many of the preserved residues matched those of nuts eaten by chimpanzees.

When put all together the evidence the team collected strongly supported the hypothesis that they had found a 4,300 year old chimpanzee nut-cracking site. The damage to the tools matched that wear inflicted on similar stones by living chimpanzees, the distribution of tools around the site was consistent with chimpanzee tool assemblages, and the residues on the tools matched nuts that chimpanzees regularly eat. Perhaps more importantly, however, the study showed that the archaeological record of non-human apes could be detected.

How far back might that record extend? It is difficult to say. Many chimpanzee tools, such as the twigs they often use, may never have made it into the fossil record, and the likelihood of identifying such tools is low. Stone tools are sturdier vestiges of ancient activities that bear tell-tale signs which distinguish them from surrounding rocks, and now that scientists know what to look for perhaps more will be discovered. Remnants of what the authors call the “Chimpanzee Stone Age” are probably waiting to be found in other African forests, and I hope that future research will be able to tell us more about prehistoric tool use in among some of our closest relatives.

[Also see this recent review in Nature about primate archaeology.]

Mercader, J., Barton, H., Gillespie, J., Harris, J., Kuhn, S., Tyler, R., & Boesch, C. (2007). 4,300-Year-old chimpanzee sites and the origins of percussive stone technology Proceedings of the National Academy of Sciences, 104 (9), 3043-3048 DOI: 10.1073/pnas.0607909104

Comments

  1. #1 Martin R
    March 1, 2010

    Many chimpanzee tools, such as the twigs they often use, may never have made it into the fossil record

    Hey hey hey hey now — that’s the archaeological record to you, Buster. (-;

  2. #2 Laelaps
    March 1, 2010

    Ah, you caught me. When I wrote that I was thinking about whether Miocene and Pliocene apes might have been using tools and what those might look like.

  3. #3 J-Dog
    March 1, 2010

    If only the chimps could teach Glenn Beck to be a reasonable animal as well.

  4. #4 Jared
    March 1, 2010

    I wonder if this was an independently developed behavior (which, on the face of it, seems likely) or if it part of human/chimpanzee MRCA culture which survived (which would be really freaking cool).

  5. #5 Laelaps
    March 1, 2010

    Jared; That is one of the questions the researchers brought up, but could not answer. I would think that tool use among prehistoric primates goes pretty far back; the trouble is that it is hard to spot. In terms of stone tool use, though, it is interesting to ponder whether the behavior evolved independently or are both derived from behaviors exhibited by the last common ancestor. We may never know, but I am glad to see more attention being paid to primate archaeology.

  6. #6 jck
    March 1, 2010

    Is there any truth to the rumors that a large, black, rectangular obelisk was found among the tools?

  7. #7 D J Wray
    March 1, 2010

    There is no reason to doubt that tools were used by other species but that in itself should not be used as confirmation of human evolution. It makes more sense to investigate the origin of language, not tools. Language is the greatest achievement of human beings (and their recent ancestors) and people have a right to question how Darwinian evolution could have given rise to this remarkable ability.

  8. #8 Paul Murray
    March 1, 2010

    A few summers ago, I watched a black-faced macaque in the National Zoo and Aquarium (Canberra, Australia) fabricate and use a tool in an attempt to get water out of a faucet. Several years of prejudice about my species blown away in 15 minutes or so of watching.

  9. #9 Mike Haubrich
    March 2, 2010

    @D J Wray –

    I am curious about why you use the specific term “Darwinian evolution.” I am also curious as to what you think can be done to investigate the use of language and how that pertains to the question at hand.

  10. #10 Christophe Thill
    March 2, 2010

    The origin of language is a tricky problem. It’s a cultural evolution rather than a “Darwinian” one (I suppose this is supposed to mean gene-based) and of course, there is no equivalent of stone tools to study. The only thing we can do is try and trace the continuity between some characteristics of human language and the vocal signals exchanged between apes. But I suspect we will be much less succesful in this kind of quest, than Darwin himself was when he traced the origins of our facial expressions back to their animal source.

  11. #11 BdN
    March 2, 2010

    @Mike Haubrich

    Because “Darwinian evolution creates primitive creatures with an ability to host visitors with language skills.”

    And of course, it happened in a parallel universe.

    And don’t forget that “An atheist, like a serial killer, can have an incredibly good memory and problem-solving skills.”

    Any other question ?

    BTW, if unclear, those come from his website…

  12. #12 amphiox
    March 3, 2010

    What about the possibility that stone tool use arose separately, but dependently in the two lineages. That is, could chimpanzee ancestors have first developed stone tool use because they observed nearby hominid groups using stone tools? (Or could early hominids been inspired to first use stone tools because they saw their chimpanzee-lineage neighbors in the local forest patch cracking nuts?)

    (Hominid hear refers to the human lineage. I am not sure what the current consensus is as to whether or not chimpanzees should also be called hominids.)

  13. #13 Laelaps
    March 3, 2010

    Amphiox; The idea that chimpanzees or humans might have learned tool use by watching the other has been floated before, but there is no hard evidence for it. I was suspect that tool use of one variety of another goes back a very long way, but since it involves elements of culture and can be dependent upon available materials in an environment it is difficult to ascertain the details as yet. Recall, too, that capuchin monkeys also use stone tools to crack open nuts, so behavioral convergence is a definite possibility.

    As for the use of the word “hominid”, it technically includes chimpanzees. The term has been used a bit loosely, but it is derived from the old idea that there was a split between living apes (members of the “Pongidae”) and humans (members of the “Hominidae”). Now we know that our species is nested within the ape group and has necessitated some changes. These days “hominin” refers to the human stem while “panin” refers to the chimpanzee stem, and together these branches make up the clade “Hominini.” The word “hominid” is still used, but today it is the name of the clade which contains the Hominini plus gorillas plus orangutans (or, roughly, the “great apes”). Go one more step down the family tree and you have the hominids plus gibbons, which comprise the group Hominoidea. This all gets a bit confusing, especially since many people are still using the “grade-based” terminology, but these days if you want to refer to one of our prehistoric relatives more closely related to use than chimpanzees, call it a hominin. I hope that helps.

  14. #14 DDeden
    March 4, 2010

    Simple tool use is not so uncommon, many species do so.
    Sea otters use stone anvils, chimps use stone anvils.
    Capuchins use hammer stones, chimps use hammer stones.
    Capuchins use oyster shells to pry open other oysters.

    But compound tool use is rare, archaic humans hafting axe, fire as tool, modern human machine age. Other species?

    Non-food procurement tool use is rare, beavers use sticks for hydrologic ecosystem management, humans used stone.

    Chimps use tools in trees or on ground but not in water.
    Humans use tools in water or on ground but not in trees.

  15. #15 film izle
    October 28, 2010

    I wonder if this was an independently developed behavior (which, on the face of it, seems likely) or if it part of human/chimpanzee MRCA culture which survived (which would be really freaking cool).

  16. #16 cihat
    February 2, 2011

    What about the possibility that stone tool use arose separately, but dependently in the two lineages. That is, could chimpanzee ancestors have first developed stone tool use because they observed nearby hominid groups using stone tools? (Or could early hominids been inspired to first use stone tools because they saw their chimpanzee-lineage neighbors in the local forest patch cracking nuts?)

    (Hominid hear refers to the human lineage. I am not sure what the current consensus is as to whether or not chimpanzees should also be called hominids.)

  17. #17 Vikipedi
    February 15, 2011

    If only the chimps could teach Glenn Beck to be a reasonable animal as well.Thank you. Benefited a lot from your site. Content for the site is very successful. After that, I will visit it often.

  18. #18 nicolas
    April 13, 2011

    If only the chimps could teach Glenn Beck to be a reasonable animal as well.

  19. #19 mp3 indir
    July 13, 2011

    I wonder if this was an independently developed behavior (which, on the face of it, seems likely) or if it part of human/chimpanzee MRCA culture which survived (which would be really freaking cool).

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