Friday, 24 August 2012

What Kanzi Didn't Do...Yet

If Neanderthals are the Uber Cool of hominins, then bonobos surely must be the ape equivalent. A species very closely related to the more famous chimpanzees, Pan paniscus have increasingly taken centre stage in research on primate cognition and technical abilities. This week there's been quite a bit of press coverage of some new behavioural experiments with bonobos making and using stone tools, published in PNAS, . Having read the paper, it doesn't sound like the actual technological skill displayed by the apes in the production of the tools is any more adept than we've seen before, i.e. it doesn't match that seen in even the very earliest artefacts from the archaeological record. If it was, I'd expect this to be far more obviously signposted in the paper. Instead, it seems that the bonobos have, in a much more natural task setting than normal, utilised a more diverse range of their stone products to perform a variety of specific functions. These tool-using actions left marks similar to those seen in the early archaeological record.




Bonobo using a twig to have a nice scratch at Leipzig Zoological Park. Photo: author.

This is an interesting experiment, with implications for primate cognition. Yet when I first heard of this paper, it was via mainstream media, and based on this I initially thought it was something rather more significant. Perhaps predictably, press attention has gone for the most sparky headlines: from New Scientist's "Bonobo genius makes stone tools like early humans did", to the horrible Daily Mail's "Kanzi the bonobo chimp learns to create tools by himself" which is not only totally out of date given Kanzi's long history of working stone, but is just a really poor article that manages to make a major chronological error AND calls Kanzi a monkey (hence I'm not linking to it). A better headline was in Wired "Video: Tool-Making Bonobos Give Glimpse of Human Origins", which is a more measured appraisal, and does convey the slightly eerie feeling evoked by seeing Kanzi unselfconsciously and casually perform 'human' tasks.

Although chimpanzees were the first to be observed using tools and hunting in the wild, it's now known that bonobos also do this, although not displaying the same variety of idiosyncratic tool-using cultures. Bonobos have however shown greater capacity for language and tool use/production within captive settings than chimpanzees. Pan-Banisha and Kanzi, half-sister and brother (28 and 31 years old) who were raised in a language research setting by Sue Savage-Rumbaugh and Duane Rumbaugh, now part of the Great Ape Trust, are probably the biggest celebrities in the primate cognition world. Kanzi was the first bonobo to learn to communicate with his human carers through the same natural process as babies learning language: by observing his mother, Matata. Born in the wild, she is actually Kanzi's adoptive mother, but never learned to use the specially designed system of lexigrams (symbols representing words or concepts). Kanzi however spontaneously began to communicate with lexigrams, and Pan-Banisha also learned in the same way. Both can obviously understand and respond to spoken language, and they have been observed writing lexigrams, especially in contexts where they wish to request something.

 Pan-Banisha draws "coffee"


Apart from being fascinating in terms of demonstrating very considerable language capacities and undeniable personhood, Kanzi and Pan-Banisha are very well known in Palaeolithic research thanks to their other talent: stone tool making. Although many primates have been observed using tools of varied materials in laboratory and wild settings, and chimpanzees and capuchins use stone cobbles and anvils to break open nuts, at present there are no wild observations of the production of stone tools by any apes. Even the simplest method of obtaining a sharp-edged tool-smashing a block- does not seem to occur.

Kanzi was the first ape in captivity to learn how to intentionally fracture stone to produce sharp flakes, and later Pan-Banisha also learned this skill. This was thanks to a research experiment begun in the early 1990s  by Nick Toth and Kathy Schick (archaeologists who had worked on the earliest stone artefacts from East Africa) in collaboration with Sue Savage-Rumbaugh and Duane Rumbaugh to determine the tool-making capacity of captive bonobos, and then compare the products to the oldest tools in the archaeological record, the Oldowan. In order to allow Kanzi to demonstrate his innate skill and record his development he was not directly taught to knap (make stone tools), by the researchers. Instead he followed an iterative process of being shown how useful sharp-edged flakes of stone were for accessing food in various types of containers, and picked this up immediately. He was then shown a very simple method of how you get such a sharp flake, by researchers using 'direct percussion', i.e. hitting pieces off one block with a hammer stone.

Within a month Kanzi made his first tool. He initially tried to copy what he had seen by 'clapping' together two pieces of rock. He then learned that throwing a rock onto a hard surface caused fracturing; when researchers made the floor soft, he changed tactics to throw one stone onto another. In an attempt to get him to try using his hands to make stone flakes again rather than throw the block, researchers encouraged him to do this while in a pool. He then began to use direct percussion again, and is clearly able to direct blows towards the margin of the core in a manner very recognisable to anyone familiar with knapping.

You can see some of Kanzi's tools at the Lithic Casting Lab website, and the images in the PNAS paper show some pieces that I would not hesitate to identify as intentionally removed flakes. However, what Kanzi and Pan-Banisha have not done is what was reported by major headlines: they are not knapping like early humans. If we don't worry too much about which hominin species we call human, and include the archaeological record right back to the very earliest stone tools we have yet found, this takes us to over 2.5 million years ago. Although there are major differences in approaches to studying these deeply ancient artefacts (some focusing on environmental factors as influencing behaviour, others social contexts such as individual skill), it is almost universally agreed that they are nowhere near as crude as those produced by the world's two expert bonobo knappers.

This is not to denigrate Pan-Banisha and Kanzi's achievements, or the new research demonstrating a very high degree of contextual flexibility in the bonobos' ability to use different tools for tasks that are likely to occur in natural settings such as breaking into a log or digging in earth (see video). It's difficult to say whether the variety in form of the flakes produced during the experiment reflects attempts by the bonobos to actually make different tools for different tasks. A much bigger sample would be needed to tease this out, in addition to starting each task with the same raw materials. But fundamentally it's not the case that Kanzi, Pan-Banisha or any other apes have produced stone artefacts close in complexity in terms of technological strategies of production as those from even the earliest Oldowan sites such as Gona, Ethiopia (c. 2.6 million years) and Lokalalei, Kenya (c. 2.3 mya).


Kanzi. From Great Ape Trust Media Centre gallery, used to report on PNAS paper.

Kanzi and Pan-Banisha fully comprehend what working stone is for. They know the potential held within a lump of rock: that if invested with their energy through fracturing it, they will obtain sharp-edged flakes of varying utility. They recognise better techniques when they see them, and also better tools: Kanzi apparently will chose superior flakes produced by human knappers over his own. Pan-Banisha has learned to listen to the note produced when striking the rock to see if it's a 'true' hit. But what they haven't mastered or even seem to 'see' are the geometries that are involved in systematic knapping, where the angle of flaking is the controlling factor in success, and needs to be managed. The scars created by one removal can be utilised to form new 'striking platforms', or a single platform can be maintained to preserve the correct angle (acute) for producing useable flakes, permitting subsequent removals to continue.

Sophisticated core management is seen right from the start of the archaeological record. It is demonstrated most spectacularly at the site of Lokalalei 2C, Kenya (c. 2.34 million years old), where between 60-70 cobbles were worked, producing nearly 3000 artefacts and many examples of 'refitting sequences': because the site is relatively undisturbed, knapped pieces can be fitted back together. This means researchers can trace the exact gestures and therefore the thought process as one particular hominin worked a core more than 2 million years ago. Aside from the astonishing coolness of this, it means we can almost watch these early knappers, and compare to the approaches taken by Kanzi and Pan-Banisha.

Refitting Group 2 (figure 6 within online journal article) preserves a record of a knapper identifying a usable existing striking platform, and removing some small flakes in a parallel series from it. Then, on seeing that the platform has an irregular edge where it's not yet been worked which could cause a problem, the hominin fixes this by turning the core and taking off a flake along the platform, effectively 'rejuvenating' it. The knapper turns the core back again, and continues removing a few more flakes, until they mis-hit and take off a too-deep flake. This means the core is now unworkable, and it is then abandoned. What this one group of artefacts preserves is a much more coherent approach to obtaining flakes from a core, in addition to the identification and resolution of a potential problem, and finally the understanding that there was no point investing more time and energy into the core.

Due to copyright costs, I can't put up any images of the Lokalalei or Gona artefacts. Here's a simple quartzite core I found in Kruger National Park, South Africa, that is similar in technology to Oldowan lithics, although this piece is likely much younger than 2 million years. Photo: author.
 The Lokalalei 2C site as a whole demonstrates remarkable economy and efficiency of stone tool production, which is echoed in other sites such as Gona. The repeated system for reducing a cobble involves pursuing flake removal using only appropriately angled natural platforms, either on one margin of the cobble which is followed around the core perimeter, or multiple edges. Removals occur in a systematic fashion from the platforms, with series of typically 2-5 but up to 11 flakes. Most cores have 3-5 flaking series, and up to 9, and between most of the series the hominin rotated the core to access a new platform. The strategy at Lokalalei 2C therefore maximises the flakes obtainable using the naturally available platforms on each core. Furthermore the 'workability' of cores is maintained as the removals themselves keep the main flaking surface flat (and therefore the flaking angle acute) by lowering its surface because they are roughly centripetal (aimed to the centre of the core from around it's perimeter). This last feature may not have been intentional, but the careful exploitation of only correct angled platforms, and economical removal of flakes from each one certainly was acheieved intentionally. A comparison by Toth and Schick of the artefacts produced by Kanzi and Pan-Banisha with those from Oldowan sites found that the bonobo cores had almost half the number of flakes removed, and had significant battering marks from mis-hits.


The sophistication of technology in the earliest artefacts yet found strongly suggests there had already been a period of developing techniques and skills (very similar to the situation with the oldest musical instruments). If this is the case, there should be older and presumably simpler, less accomplished artefacts. It's an interesting question to ask: would we actually recognise the 'first' stone tools? If only some of the bonobos' products are clearly identifiable as intentionally worked, perhaps we might not perceive the scant record this type of stone working would leave behind. But maybe we haven't seen all that Kanzi and his kind can do yet. Although he and Pan-Banisha have been knapping over more than two decades, they have probably not been doing it as often as you might expect if the skill was central to their survival. If we assume that the sharp-edged tools created by working stone had an adaptive advantage to early knappers in procuring food, then it's quite likely that they spent a great deal of time knapping. Motor skills are certainly improved by practice, but more experienced knappers also develop an understanding of how stone fractures in regard to the intersection between force and location of the blow and the angle between the platform and the removal face.

Truly expert tool use, if not production, can be seen in the various chimpanzee groups who habitually use cobbles and anvils to crack nuts. This is no mean feat as it requires manipulating three different 'parts' to the task, in a hierarchically organised sequence. In contrast to the way the bonobos learned to work stone, nut-cracking is learned by chimpanzees pretty much from birth as babies watch their mothers, and it occurs within a highly social setting where members of a group work alongside each other for several hours, providing a strong reinforcement. I suspect that if and Kanzi and Pan-Banisha were spending a few hours every day they might develop more systematic knapping skills themselves, although their accuracy may never reach that of Oldowan knappers due to bio-mechanical constraints in terms of the size of their hands and the force they apply.

 Chimpanzee group cracking nuts at Bossou. A very social setting.

 It's a shame that the study in PNAS was over-egged by the wider media, because it leads to the same 'story' of "Apes are just like early humans" being repeated all the time, and which is not as interesting as the reality. Kanzi, Pan-Banisha and other apes and primates will probably continue to show impressive technological skills. The archaeological record may well be extended back to include even older industries with simpler stone working technology (claimed 3.4 mya old cutmarks from Dikaka, Ethiopia which would push tool use WAY back, are currently disputed). But in any case, bonobos and other apes are just as derived, just as evolved, from our last common ancestor some 7-8 million years ago as we are. There's a large and growing family of early hominins on the branch leading to us, and as yet we are unsure whether all of these species even made tools. As our closest living relatives, chimpanzees and bonobos apes show us our shared hominini heritage, but they will never be a direct mirror of our own past.


References

Delagnes A, Roche H. 2005. Late Pliocene hominid knapping skills: the case of Lokalalei 2C,West Turkana, Kenya. Journal of Human Evolution. 48: 435–72
Schick K,Toth N, Garufi GS, Savage-Rumbaugh ES, Rumbaugh D, Sevcik R. 1999. Continuing investigationsinto the stone tool-making and tool-using capabilities of a bonobo (Pan paniscus). Journal of Archaeological Science 26: 821–32
Semaw S, Renne P, Harris JWK, Feibel CS, Bernor RL, et al. 1997. 2.5-million-year-old stone tools from Gona, Ethiopia. Nature 385: 333–36
Semaw S. 2000. The world’s oldest stone artifacts from Gona, Ethiopia; their implications for understanding stone technology and patterns of human evolution between 2.6–1.5 million years ago. Journal of Archaeological Science 27: 1197–214


Toth, Nicholas and Kathy Schick. 2009 The Oldowan: The Tool Making of Early Hominins and Chimpanzees Compared. Annual Review of Anthropology 38: 289-305.
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