Myths, mysteries, & facts about primate tool use

( revised, 03/13/12)

  • "tool use by non-primates?"

  • References
  • Primate tools

    Primates are generalists. While other species have evolved very specialized forelimb "tools" like claws, wings, hooves, primates have a very flexible hand and brain that lends itself to many uses. (This lack of specialization may stem from our very neotenous mammal origins?).

    Tools, then, may be considered artifacts that potentially enhance the fitness of those who use them. Some of these tools may be said to extend the intelligence of their users -- enabling them to solve problems otherwise beyond their grasp. (Artifacts are objects modified or created by individuals, usually as part of a culture. Here I include both material objects-- knives, spears, levers -- and abstract objects-- words, numbers-- in the category of artifacts. Just as a lever increases prying power, numbers increase computing power.


    The practical value of tools --from clubs, knives, and needles, and fire to computers and science -- even language and the decimal system --needs little comment. Primates --and humans in particular -- have brains that like their hands can be adapted to many uses in themselves or with "tools." (See my notes on "mind-tools.")
    The obvious differences between the universal use of tools by humans and their sparse and static use by non-human primates (NHP) suggests understanding tool use may reveal much about human nature and its origins.

    Darwin not Goodall or Boesch

    mythology of tool-use

    One might get the impression from some recent writers that NHP use of tools was a recent and surprising--even dismaying discovery. Savage-Rumbaugh (1995) says, for example, "The belief that man alone can make tools had gone by the wayside in the first years of Jane Goodall's observations in the field. p. 201"
    Despite such suggestions to the contrary, tool use in NHPs has been known at least since Darwin (1871). He noted about 130 ago, for example:

    "It has often been said that no animal uses any tool; but the chimpanzee in a state of nature cracks a native fruit, somewhat like a walnut, with a stone." The recent video of wild orangs using stick tools would not be surprising to Darwin nor Wallace-- who observed this himself.

     

    Some of the earliest research on apes involved their grasp of tools-- Kohler's (1925) work, in part a reaction to Thorndike (1901), triggered considerable experimental follow-up on conditions involved in acquiring tool use. (See Spence, 1937; Birch, 1945; Schiller, 1949/1957). Schiller concluded that the chimps he studied at the Yerkes Laboratories of Primate Biology in Orange Park, Florida. had an innate set of motor responses that showed up in their play as they matured. These actions included pulling, stacking, and manipulating sticks. The actions themselves are unlearned-- associations between acts and chance outcomes lead to problem solving. "Play and work for food were separate sphere of activity, that became correlated with repeated experience (p.277).

     

    Given the reports published in Darwin and the extensive experimental work on the topic, it should be no surprise to find chimps using tools in their own environments. Jane Goodall (1986) was one of the first to observe and report on this issue.

    What is the extent of chimp tool use in their natural habitats? Boesch and Boesch (2000) recently tallied up chimp tool observation from the Tai forest and defined a number of types of tool use and construction:: extracting food, probing or exploring, cleaning, and displaying. Others might break this down into threats and displays for dominance effects. Clearly the situation is a factor in NHP tool use -- whether it is termite fishing, nut-cracking or tuber digging with sticks. See below.

    Some chimps have been filmed hunting busshbabies with spears. (Or at least poking them dangerously hard.)

     

    Recently it has been claimed that chimps used stone nut crackers at least 4300 years ago. There are lots of uncertainties about this research, e.g. were chimps really the creators of these tools? However the real question is why there appears to be no progress in the chimp tool construction industry over the last 5000 years?! Lack of language? No need?

     

    Several reports, both from human and natural environments, suggest female NHPs are more involved in tool use and perhaps spread of tool-using. (Recall Imo the Japanese macaque, the Boeschs' reports, and the CHimp Minds video.) Perhaps female juveniles are more observant of their moms?

    Recently orangs have been filmed using sticks to extract honey from tree holes and seeds from shells. In captivity they can be seen using all sorts of human objects. They like to use their mouth as adjunct tool holder.

    What about bonobos? Other than a few reports, bonobos haven't been known for natural tool use. The young ones play with objects and in captivity are very skilled. Perhaps their natural environment doesn't require tools as their cousins, common chimps, use.

    We might also expect monkeys to be potential tool users; recall Imo in "life in the trees." She started several creative fads among Japanese macaques. Smart little monkeys like capuchins also known to be somewhat sophisticated tool users.

    Human tool use

    Primates were using tools before the advent of modern humans.. Neanderthal's precision grip appears to be as capable as modern humans. Neanderthals and their ancestors produced cutting tools and probably spears. It is worth reviewing the human hand advantages for griping and throwing. See the video clip from Sci Am Frontiers. "handmade humans."

     

    1. Hand axes

    Flaked hand axes are at least 1.5 to 2 millions old. This is some 2 million years after bipedalism and at time when brain size is increasing. Patterns in flaking suggest these hominid tool makers already were primarily right-handed. (EHE, 343). Recent analysis of flaked stone cutting tools indicate these may as old as 2.6 mya and were a factor in improved diet leading to brain expansion.

    Ambrose, S. H. (2001). Paleolithic technology and human evolution. Science, 291, 1748-1753.

    2. fire

    Controlled use of fire may be only several hundred thousand years old -- much less in some regions. Fire may have been used by early homo Erectus some 1.8 million years ago but it remains unclear if they really controlled it. The most recent estimates, based on analyses of 800,000 year old hearths in the middle-east, suggest controlled fires may be at least that old. Cooking was probably a major breakthrough as a kind of tool enabling access to foods (tubers and meat) not easily obtained otherwise. Similar to the hand as a very general tool, cooking enables lots of diverse foods to be converted to the large number of calories humans require-- even more so in colder climates.

    Recently (2009), sharp stone blades, dating to about 500k years ago have been found in Kenya. These may foreshadown cerebral specialization and language evolution. Stone blade tools have recently been found in the Arabian peninsula, dated at 106,000 years old.

    3. Weapons, needles, etc. and art

    Coincident with the earliest modern human fossils, evidence of their skills shows up increasingly in the last 30-40,000 years. Throwing is a distinctly human skill, perhaps surpassing neanderthals in regard to accuracy.

    4. "mind-tools" -- language and other modes of representation

    Our minds have been extended by our use of language, maps, drawings, logic and mathematics. In the context of scientific inquiry these tools are used to extract information from nature analogously to our ancestors extracting nuts from their shells or marrow from bones. Just as levers extend the power of our muscles, these tools extend the power of our naïve minds.

    Language -- < 100,000 years ?

    Counting -- >30,000 years ago

    The oldest counting tools are the numerous animal bones found in western Europe and marked with one or more sets of notches. These tally sticks are between 20 and 35,000 years old. They possibly served to tally hunting kills. Ifrah (2000, p.xix) notes these notched bones are probably the oldest human invention apart from fire in use today.

    Context of tool use in non-human primates

    (See Tomasello and Call's (1997) extensive review of NHP tool use in Primate Cognition (T&C).. See many examples in my tool video sampler if we have time for it.) There also is evidence that crows and other birds use tools -- one claim is ""Crows are more competent tool users than even chimpanzees," says zoologist Alex Weir of the University of Oxford, who led the study published in Proceedings of the Royal Society of London1. They also appear to have a different set of rules for handedness than people and chimps, he says." (reported in March, 2004, Nature.) See the corvid (crow-like birds) videos online!

    situations for chimp tools: get food including water, grooming/hygiene, and threat/display/intimidation

    See video for examples.

    tool making is limited in extent and species

    Chimps and some orangs, but not bonobos, nor gorillas show widespread tool construction in nature.
    "Perhaps the natural environment of (other apes) does not challenge their cognitive capacity enough to stimulate a need for tools." EHE 342 I don't doubt all apes --even clever monkeys-- can have some tool use comparable to chimps if circumstances called for it. Recently orangutans have been observed getting food with tools and using leaves as an umbrella. In captivity of course orangs are excellent tools users and show curious imitative skills as we have seen. Darwin (1871) recounted a number of reports of monkey tool use. We have seen or read about Imo, the famous Japanese macaque's "inventions."

    It is likely that variation in ape tool use-- especially chimps and orangutans-- is due to local factors and subsequent observational learning. Broadly considered, this would be a kind of culture or local habit.

    natural vs human and lab settings

    From a few non-natural situations -- Kohler's apes, orangs at Galdikas' station -- it is clear and no surprise that apes can acquire skills not normally exhibited. Why should they display abilities for which they have little use in their natural condition?

    Free time, motivation, availability of human artifacts and human models?

    These are important differences between natural and human settings that might account for some of these differences between nature and laboratory. These considerations suggest that maybe human tool proficiency not only was driven by greater food availability, but also that free time was made available by those tools that worked recursively to enable even more and better tools to be created.

     

    Orangs provide many examples of animals with little tool use observed in nature but who look like the Ace Hardware Primate among humans, e.g. Duhong, Chantek, many in Galdikas' care, and the Alda-Tomasello video clip.

    theoretical framework

    In Piaget's stages

    (See Tomasello & Call's book for a critique. P.57. Also Gomez, 2004 Fig.3.1, similar to link above.)

    The sensorimotor stages

    This stage largely concerns construction of representations of objects and manipulation of objects and their representations. The middle stages are the beginnings of trial and error learning -- the law of effect. The last stage is the beginning of "insight." Tool-use in Piaget's theory is illustrated by the use of one object to obtain anothe -- e.g. pulling a blanket to get an object on the blanket. ("means-end" processes).

    Other more advanced stages: figurative, logical, formal

    There is very little evidence that apes go beyond sensorimotor processes though Kohler's apes with insight might be at the "figurative" stage, manipulating images. But these are problematical interpretations.. T&C say, p.70, while human raised great apes engage in some of the same kinds of behaviors with toys and other artifacts as do human infants, the symbolic or representational status of these behaviors is unclear." They can say that again!
    The human mind-tools (above) all rely on mental representations characteristic of the advanced stages (including insight) in Piaget's theory.

    Do all primates have the means-end potential for tools use?

    See T&C, p.88. The answer may be "yes" -- and so do many other species in limited domains. (Remember this is typical behavior at substages 3-5 in Piaget.)

    Who has causal understanding?

    Some like Tomasello & Call distinguish between "insight" and "foresight" -- the former a recognition of how a problem can be solved, the latter reserved for a situation where the individual sees ahead of time what is needed and goes about to obtain those items -- a shopping list. P.89
    Both require some mental representations of causal relationships of objects to solutions -- substage 6 or better. See the comparison between capuchin and chimp tool use assessment in T&C. (~p,90 report on the Visalberghi (1993) findings.) Essentially apes seem to rely less on pure trial and error.

    In nature, chimps show quite different behavior toward hidden termites than do baboons who also like to eat termites. (See video clip). It is natural to interpret this as a difference in object permanence and/or foresight.

    Novel use of objects as tools

    Writers (T&C, Gomez) discuss novelty and flexibility as requiring mental representations. And while that discussion seems reasonable, it seems that lots of trial and error-like experience (and/or perhaps, "play") underlies the availability of those flexible representations. P.98

    Biological Factors in tool use

    Dexterity

    The hand

    The ultimate general tool -- see EHE 346. and "handmade human" video. Don't overlook human-ape differences in grip -- humans but not apes have a flexible opposable thumb capable of touching all the other four digits. We also have a flexible pinky for stabilizing our grip on tools and weapons and golf clubs.

    These precision forelimb/hands enable controlling tools as an extension of those biological limbs.

    (See http://sciencenow.sciencemag.org/cgi/content/full/2008/128/2 )

    The mouth

    For humans, its role in speech is obvious -- yet even other primates, notably chimps and orangs, also birds utilize it as a holding tool (See video examples.)

    Brain -eye coordination

    All of the brain regions below have been enhanced in humans relative to non-humans of the same body weight. (Passingham, 1982) Their relationship to tool use is obvious. See the recent paper on brain laterality in NHP and tools use in Psychological Science, 2007.

    Prefrontal cortex --planning -- "foresight"

    Hippocampus -- storage

    Some "brain record" of prior trials -- errors and successes -- need to be available.

    Cerebellum -- learning and executing rapid skilled movements

    "mirror neurons" -- cells that transduce sensory input into motor output enabling an automatic "monkey-see monkey do" (See video.)

    (See Ramachandran's online discussion and also.)

    Left hemisphere specialization for tools and language?

    It is an old idea that tool use prepared human ancestors for language; some put it the other way around. In any case, knowledge of tool use can be lost with damage to the left hemisphere.

    Origins of tool using ability

    In most cases we must observe the ontogeny of the skill in individuals and NOT just the performance. Thus while humans have a language "instinct -- dogs and apes may work very hard and never figure out our hierarchical syntax. It is a big mistake to assume because juvenile apes hang out with mom, that mom is "teaching" them anything -- despite what some say. Overall, all tool use --like anything else-- is acquired through a combination of (1) inherited capabilities, (2) fundamental trial and error processes which can be considerably reduced by (3) social priming including explicit teaching where possible.

    Instinct

    Often all this means is that the number of "trials" any member of the species must engage in to solve a problem is extremely limited, thus guaranteeing that almost everyone solves it -- chickens getting out their egg by moving and their big beak cracks the shell.

    Learning

    Individual effort -- trial and error, play, chance

    Each organism builds a repertoire of actions and experiences that can be applied to new situations.

    Social extraction of information from others

    This is perhaps the most important and difficult issue in understanding primate behavior. While human culture is obvious (though its mechanisms largely not fully understood), there are many questions surrounding claims that NHPs have culture too. Some of this is definitional; what is culture, anyway? For now we can limit ourselves to questions about if and how one primate "extracts" information from another. (Recall this was one of Thorndike (1901) basic questions, too). Recent investigations show lots of species, including chimps, will acquire solutions to problems according to a group norm or "culture."

    Whiten A, Horner V, de Waal FBM. 2005. Conformity to cultural norms of tool use in chimpanzees. Nature 437:737–40

    Varieties of "social priming"

    For example in cracking nuts, mothers may prime certain objects as stimuli for their offspring, prime certain actions, that together with trial and error reduce the "trial space" considerably facilitate acquiring the skills without any teaching on the mothers part or direct imitation on the young chimps part. (Recall Tomasello's comments regarding the rake experiment in the video.) Read about some of the cultural variation in chimp activities.

    Priming -- increasing the probability of some activity (presumably by activating some brain regions) can focus on several aspects of what might be informally called "imitation." The following sketch is taken after Byrne (1995).

    Emulating a model

    This can include imitation of the accomplishments or the intentions -- the latter is rare in nonhumans.

    Teaching

    Systematic teaching is probably limited to humans. Boesch claims mother chimps may act to modify their infant's nut cracking activity as if teaching. There's lots of room for anthropomorphism here. Premack (2004) notes something one can observe in many videos - chimp mothers rarely monitor the details of their offspring's efforts to acquire skills. As Premack concludes, this helps explain why it takes young chimps many years to acquire skills humans could teach in a few weeks.

    Japanese primatologists come to a similar conclusion:

    Regarding tool use, juveniles watch their mothers intensively and try those behaviors themselves-- but the mothers "do not actively teach infants 647"

    "..it is very rare for mothers and infants to interact triadically in the context of tool use." 647 "the mothers did not model, guide, mold, punish, or praise the infant's behavior. The infants paid attention to the mother's behavior, but the attention was not shared." "The appparent inability of chimpanzees to understand the mental state of another ..therefor may be due to the lack of shared attention." 648

    Tomonaga, M., & et al. (2007). Chimpanzee Social Cognition in Early Life: Comparative-Developmental Perspective. In E. A. Wasserman & T. R. Zentall (Eds.), Comparative cognition. New York: Oxford University Press. (639-650).

    Language plays a huge role in human acquisition of all sorts of knowledge, including tool use. Even 13-18 month old children can modify their concepts by language. Language and joint attention conspire to produce the characteristic and perhaps unique development of teaching in homo Sapiens.

    Ganea, P. A., Shutts, K., Spelke, E. S., & DeLoache, J. (2007). Thinking of things unseen: Infants' use of language to update mental representations. Psychological Science, 18(8), 734-739.

    "Imitation" -- is this a useful term?

    This is open to lots of interpretations -- what is imitated? Maybe "emulation" is better when appropriate.Recent "mirror-neuron" discoveries will soon make this clearer to us. They are found in monkeys and probably all primates including us. In any case, imitation suggests a close correspondence between model movements and learning movements. And again it doesn't appear chimps do this as well as humans (Premack, 2004).

    Sex differences in learning

    Some time ago, the Boeschs reported that chimp females seemed more interested and perhaps adept at cracking nuts than the males. And everyone has heard about the innovations of Imo, the female Japanese monkey. Now a report in Nature, April 15, 2004 indicates female chimps learn termite fishing much more rapidly than their male peers. (Also see "Chimp Minds" video and recent observations of 'spear' use by female chimps..) There are sex related differences in acquisition of skills in humans as well.

    tool use -- explained?

    It may be that the acquisition of tool-use, like learning in general, is a process of trial & error, within a varied context of instinct and body limitations, insight, and imitation understood as a variety of socially mediated information transfer or priming. These social factors, like environmental factors and biological ones, serve to limit the possible trial failures (errors) and thus greatly facilitate success. In humans, we call this part of culture; is it reasonable to call non-human primate social traditions culture too? See the Chimpanzee culture exhibit and read the Nature paper available there -- at least look at the figures..

    Of course part of human culture includes explicit teaching (cf. Piaget's ideas on formal thinking ) and the massive dependence on 'mind tools' which provide a foundation for the progressive development and transfer of culture in human society but barely noticeable at all in ape cultures.

     

    Non-primate tool use?

    A number of other species -- particularly birds (parrots, corvids) -- have been observed to use tools. Whether much "understanding" accompanies these observations remains to be seen.

     

    References (in progress)

    .

    Ambrose, S. H. (2001). Paleolithic technology and human evolution. Science, 291, 1748-1753.

    BECK, B. B. (1978). Ontogeny of tool use by nonhuman animals. In G. M. Burghardt & M. Bekoff (Eds.), The development of behavior Comparative and evolutionary aspects (pp. 405-419). New York: Garland.
    Birch, H. G. (1945). The relation of previous experience to insightful problem solving. Animal problem solving. A. J. Riopelle. Baltimore, Penguin Books: 116-136.
    Boesch, C. and H. Boesch-Achermann (2000). The chimpanzees of the Tai forest: Behavioral ecology and evolution. Oxford, Oxford University Press.
    Current Biology 17(5): 412-417.
    Frith, U. (1998). "Editorial: Literally changing the brain." Brain 121: 1051-1052.
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    Ganea, P. A., Shutts, K., Spelke, E. S., & DeLoache, J. (2007). Thinking of things unseen: Infants' use of language to update mental representations. Psychological Science, 18(8), 734-739.

    Garcia y Robertson, R. and J. Garcia (1988). Darwin was a learning theorist. Evolution and learning. R. C. Bolles and M. D. Beecher. Hillsdale, NJ, Erlbaum Publishers.

    Goodall, J. (1986). The Chimpanzees of Gombe: Patterns of Behavior. Cambridge, Belknap Press of Harvard University Press.

    Ifrah, G. (2000). The universal history of numbers. New York, John Wiley & Sons.
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    Tomasello, M. (1990). Cultural transmission in the tool use and communicatory signalling of chimpanzees? "Language" and intelligence in monkeys and apes. S. T. Parker and K. R. Gibson. Cambridge, Cambridge University Press: 274-311.
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