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Beads for a Plastic Mind: the ‘Blind Man’s Stick’ (BMS) Hypothesis and the Active Nature of Material Culture

past material culture left some other more basic and direct links between cognition and material culture unexplored.

Of course, until quite recently, one could hardly find any direct evidence for changes in the organiza-tional anatomy of the human brain resulting from a decidedly cultural cause. Consider, for instance, the property of neuroplasticity (for a good review see Pascual­Leone et al. 2003) which has a central role in understanding human embodiment and the possible links between mind, brain and culture. Although notions like that of experience-dependent plasticity go back at least to the time when D. Hebb (1949) first described the effects of ‘environmental enrichment’1 (Nithianantharajah & Hannan 2006) on the brain — simply by comparing rats that were allowed to roam freely in his home with those that had been left in laboratory cages — little was then known about the underlying causal mechanisms.

Yet over the last two decades, our knowledge about neuroplasticity and the ability of the developing brain to modify its organization escaping the restric-tions of its own genome has seen drastic advances. Not only is neuroscience now able to provide new insights into the mechanisms of experience-dependent plastic-ity demonstrated by Hebb’s experiments, but it is now

Cambridge Archaeological Journal 18:3, 401–14 © 2008 McDonald Institute for Archaeological Researchdoi:10.1017/S0959774308000449 Printed in the United Kingdom.

Lambros Malafouris

In this article I employ the example of the ‘Blind Man’s stick’ (BMS) in order to redraw the traditional boundaries that separate brains, bodies and things. It is argued that the functional anatomy of the human brain is a dynamic bio-cultural construct subject to continuous ontogenetic and phylogenetic remodelling by behaviourally important and socially embedded experiences. These experiences are mediated and sometimes constituted by the use of material objects and artefacts (like the stick) which for that reason should be seen as continuous and active parts of the human cognitive architecture. Based on the above premises I use the example of the Blombos shell beads in order to explore the role of

early body decoration in the emergence of human self awareness.

Can culture (in general) and material culture (in par-ticular) change the human brain? Is the material world causally effective in shaping the functional anatomy and structure of the human cognitive system? Above all how should the relationship between mind, brain and material culture be understood? What is the role of things in the dynamic interaction between neural growth mechanisms and environmentally derived neural activity? When, two decades ago, the argument for the ‘active nature of material culture’ advanced in archaeology (Hodder 1982; 1987; Miller 1987; Renfrew 1982; Tilley 1991; Thomas 1996) few could imagine that this could ever be explored at the level of the human brain. At that time, and for many good reasons, it was the recognition of the symbolic, ideational and social dimensions of material culture that occupied the focus of archaeological attention and theoretical controversy. Many important lessons, epistemic and other, have been learned over the last two decades, especially in the field of cognitive and social archaeology which, coupled with many new empirical findings, transformed our understanding of human cognitive evolution and the cognitive life of things. But an argument can be made that the archaeo-logical interpretive preoccupation with the symbolic, representational and communicative dimension of

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possible even to delay, through manipulating envi-ronmental enrichment, the onset and progression of brain disorders (e.g. Huntington’s disease, Parkinson’s disease (PD), Down’s syndrome) and various forms of brain injury in transgenic mice. Moreover, it has been demonstrated that enrichment enhances learning and memory, reduces memory decline in aged animals, decreases anxiety and increases exploratory activity (Nithianantharajah & Hannan 2006). Coming closer to our own species, even more impressive are findings in the case of primates. A characteristic example of current progress in this area can be found in the study of Jackson et al. (2006, see also Mavoori et al. 2005) where for the first time an implantable neurochip was designed and used for long-term recording and stimulation experiments in freely behaving primates. This enabled them to show that natural patterns of cortical spiking in vivo during normal behaviour can lead to input­specific Hebbian plasticity.2 We should also mention here the recent neuroanatomical study by Hihara and colleagues describing how two weeks of tool-use training forges a novel cortico–cortical connection linking the intraparietal area and tempo-roparietal junction (TPJ). This provides the first evi-dence for induction of novel connections in the adult monkey cerebral cortex by demanding behavioural learning (Hihara et al. 2006; see also Iriki 2005; 2006; Iriki & Sakura 2008).

Equally important are the findings in the case of humans where cognitive and social neuroscience begin to offer a whole new means for exploring the effects of culture on the human brain and the mechanisms of activity-dependent plasticity which underlie the reorganization of cortical representations during learning (Poldrack 2000; Kelly & Garavan 2005; Quartz & Sejnowski 1997). We now know that plasticity is not an occasional but the normal ongoing state of the nervous system throughout the lifespan (Pascual­Leone et al. 2003, 379). Not only do the human cortical maps exhibit strong plasticity during the early developmental period, during which synaptic densi-ties (the number of synapses per unit volume of brain tissue) in most brain regions are at their maximum, but they also appear to retain a significant degree of plasticity into adulthood (Buonomano & Merzenich 1998; Blakemore & Choudhury 2006).

Furthermore new evidence for learning-induced alterations in the brain’s macroscopic structure, which among other things contradict the tradition-ally held view that cortical plasticity is associated with functional rather than anatomical changes, becomes available. Two characteristic examples that can help us illustrate the above can be found in the

case of musical training and navigation expertise. In the first case, comparison of brain anatomy of skilled musicians with that of non-musicians indicates that prolonged instrumental practice leads to an enlarge-ment of the hand area in the motor cortex (Amunts et al. 1997). Similar plastic effects have been observed in professional pianists and violinists with respect to the size of the corpus callosum (Schlaug et al. 1995). In the second case the study of Maguire et al. (2000) concerning the navigation-related changes observed in the hippocampi of London taxi drivers is reveal-ing. The comparison of the structural MRI (magnetic resonance imaging) scans obtained from the taxi drivers and the control subjects showed on the one hand, that the posterior hippocampi of taxi drivers were significantly larger, due to their extensive train-ing and experience in navigating inside the city of London, and, on the other, that hippocampal volume correlated with the amount of time spent as a taxi driver (positively in the posterior and negatively in the anterior hippocampus).

The developments and findings discussed above bear some important implications for the archaeo-logy of mind and our conventional understanding of human cognitive becoming. Of course, plasticity, similarly with many other areas of research (e.g. brain size, or more recently mirror neurons), may not be the best place to look for signs of human uniqueness. Nevertheless, although plasticity is not the whole story it certainly points in the right direction, encour-aging new hypotheses and offering a useful analytic bridge between brain, body and culture. For indeed, if the volume of the hippocampus of a taxi driver and the corpus callosum of a pianist can be positively cor-related with the time spent taxi driving (Maguire et al. 2000) or practising the piano (Schlaug et al. 1995), then the evolutionary significance of many long­term practices in human brain anatomy, structure and function needs extensive rethinking. Stone knapping is the obvious example here with Stout et al. (2008; Stout & Chaminade 2007; Stout 2005) already offering some concrete imaging evidence about the neural correlates of the changing lithic technologies and their possible implications for long-standing evolutionary questions such as the relationship between tool use and language. Clearly the questions that the above findings raise extend beyond the domain of stone tools. They also relate to more recent processes and practices that appear well after the appearance of Homo sapiens, between 200,000 and 70,000 years ago, arguably with major implications for our conventional archaeological understanding of the origin of human cognitive modernity. Long­standing anthropological

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and archaeological debates, such as those over the nature of symbolism, the mechanisms of social memory or the effects of literacy in the human cogni-tive system — the latter more familiar as the ‘literacy thesis’ (Halvenson 1992) and more recently through the work of M. Donald (1991, 308–19) — can now be seen in a new light. For example, comparing, using positron emission tomography (PET) scan, a group of literate and illiterate people from a small town in southern Portugal, Castro­Caldas and colleagues (1998) offered the first direct evidence that literacy per-manently changes brain organization. Two years later another PET study provided additional evidence that cultural factors, as reflected in different orthographic systems (Italian vs English), can powerfully shape neurophysiological systems (Paulesu et al. 2000). More recently Tang and colleagues (2006) have found that divergent linguistic and cultural experiences (native Chinese vs native English speakers) can be associated with distinct patterns of brain activity during math-ematical processing.

Naturally exploring the effects of culture on the brain (and vice versa) over the long-term is a far more difficult task. The link between ontogeny and phylog-eny is not as straightforward as our previous parallel between taxi driving and tool making might imply. At present, learning and practice-related developmental plasticity appear as the most promising areas of research in helping us to build some analytic bridges between the short-term and long-term aspects of human cognitive becoming in ways that could become operationalized from an archaeological perspective. To this end, two recently proposed, and to a large extent complementary, hypotheses may offer some additional guidelines in our attempt to understand the nature of long-term developmental cognitive mecha-nisms between the poles of nativist, selectionist and constructivist models (Quartz 1999). On the one hand, the neural exploitation hypothesis claims, very briefly, that key aspects of human social cognition are under-pinned by the adaptation of sensory-motor-integrating brain mechanisms to serve new roles in thought and language, while retaining their original functions as well (see Gallese 2005; Gallese & Lakoff 2005). On the other hand, the hypothesis of cultural reconversion or ‘neuronal recycling’ (Dehaene 2005, 147) refers to the capacity of human cerebral architecture to transform what was initially a useful function in our evolution-ary past into another function which is currently more useful within the present cultural context.

All these prospects, I suggest, come with a clear requirement: working towards developing a neuroarchaeology of mind we need to constantly

remind ourselves that however significant the work-ings of the brain might be, they offer us only a part of the picture. The temptation to use all these rapidly accumulating neuroscientific resources for firmly situating the human mind inside the head should be resisted, I believe, for obvious reasons: human cogni-tion, as archaeology ought to know better than any other discipline, needs more than a brain (Hutchins 1995; Clark 1997; 2001; Knappett 2005; Wheeler 2005; Renfrew 2007). The real challenge facing archaeology, then, lies in reconciling and integrating our new knowledge about the functional networks of the devel-oping human brain and their possible culture­specific patterns of activity with the accumulating evidence for the extended, distributed, embodied and mediated character of human cognition (Malafouris 2004) (Fig. 1). The objective is not to translate or reduce a cultural story into a biological one but instead to integrate the two stories. The key question to ask, as philosopher Andy Clark has proposed, is how do we put brain, body and the world back together again (1997)? To this end I propose that the study of material culture can make some very important contributions.

To illustrate the above further and as a good means to put forward the main argument of this paper I will employ the classical phenomenological example of the blind man’s stick (from now on BMS) (Merleau­Ponty 1962, 143; Polanyi 1966).

The Blind Man’s Stick (BMS) hypothesis

Think of a blind man with a stick. Where does the blind man’s self end and the rest of the world begin? Where do we draw, and on what basis can we draw, as Gregory Bateson asks, a delimiting line across the extended cognitive system which determines the blind man’s locomotion? At the tip of the stick? At the handle of the stick? Or at some point halfway up the stick? (Bateson 1973, 318). More than four decades after Merleau­Ponty (1962), Polayni (1962) and Bateson (1973) first raised these questions they are still with us, maybe more timely than ever if one considers the radical innovations that are taking place in the area of neuroprosthetics. For instance, Brain­Machine

Figure 1. Mind is more than a brain.

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Interfaces (BMIs) now make it possible for a monkey or human to operate remote devices directly via neural activity (see Nicolelis 2001; 2003; Donoghue 2002).3 Of course, impressive as the ability to control a robotic hand by ‘thought’ alone might seem, it is, nonetheless, simply the most recent chapter of an old story, which archaeology knows well, and of which the first chapter was probably already written some 2.6 mya with the manufacture of the first stone tools. Indeed, from an archaeological perspective the challenge that the BMS question, or in fact any other Brain­Artefact Interface, poses is even greater. One needs simply to replace the stick with any of the numerous artefacts that constitute the diverse archaeological inventory of prehistoric material culture, from the tools and marked objects of the Stone Age to the more recent symbolic or ‘exographic’ (Donald 1991) technologies, in order to realize that there is more to the BMS question than a mere philosophical puzzle. The problem is further complicated if one considers that for archaeology the stick is not simply a ‘pathway along which differences are transmitted under transformation’ (Bateson 1973, 318), but instead a difference in itself. The stick, to use McLuhan’s formulation, is very often not the medium but the message (1964).

It may not be as obvious as it should be, but some of the most challenging questions about the emergence of human intelligence and our understanding of cultural transmission and the cognitive life of things depend on where precisely one decides, implicitly or explicitly, to draw the line between the mind and the material world and infer the direction of causality between biology and culture. Even for those of us willing to subscribe to some of the presently available relational models of embodiment recognizing that differentiations between ‘inside’ and ‘outside’ often do not apply in the context of mediated activity and material engagement, the question of the ontologi-cal status of the stick remains vague. And as long as the ontological status of the BMS remains vague it threatens not only to obscure the whole edifice of cognitive archaeology and material culture studies, but also to undermine the value and contribution of these growing research fields in the contemporary sciences of mind.

Consequently, and in order to make more clear my case in this paper, let me clarify that I will use the BMS in two major senses: on the one hand I will use the BMS as an exemplar of the Brain–Artefact Interface (BAI) — used here in the broader sense of long­term material engagement to signify the point of intersec-tion between cognition and material culture. Secondly, I will use the BMS also as a working hypothesis stating

that the functional structure and anatomy of the human brain is a dynamic construct remodelled in detail by behav-iourally important experiences which are mediated, and often constituted, by the use of material objects and artefacts which for that reason should be seen as continuous integral parts of the human cognitive architecture. Grounded upon the general framework of the Material Engagement approach (Malafouris 2004; 2007b; Renfrew 2004; 2006; 2007; Malafouris & Renfrew forthcoming; Malafouris in press) the aim of the BMS hypothesis is to help us redraw the line that separates brains, bodies and things by bringing the archaeology of mind face to face with two crucial and to a large extent neglected questions: (1) The first question concerns the causal efficacy of the material world in the human cognitive system and the functional anatomy of our brain. (2) The second question pertains to the boundaries of the human cognitive system and what became known recently as the hypothesis of extended mind (Clark & Chalmers 1998): Can things, made of wood, stone and clay, really be parts of the machinery of human thought?

I start with the former question which in the case of our BMS example can be put as follows: What does the stick do for the blind?

Our common sense would seem to favour the idea of a cognitive agent who simply exploits a tool in order to overcome a perceptual deficiency by sub-stituting vision with touch. To a certain extent this is precisely what happens as imaging studies indicate in the case of many blind subjects. Cortical areas normally underlying vision are recruited for other sen-sory modalities. Characteristic of these cross­modal plastic effects is the case of proficient Braille readers where not only do the sensorimotor representation of the reading finger become greatly developed in com-parison to the representation of other fingers (Pascual­Leone et al. 1993; Sterr et al. 1998) but tactile processing is also ‘rerouted’ to occipital visual cortex (Sadato et al. 1996; 1998; Cohen et al. 1999). In fact, using trans­cranial magnetic stimulation (TMS) Pascual­Leone et al. (1993) were able to show that modifications in the motor cortical map associated with the reading hand in Braille readers was already manifest after only a few hours of training. Recent studies have further refined and extended these findings addressing the differences between early and late blind, and the role of tactile versus verbal/linguistic aspects of the task (for review see Merabet et al. 2005).

We have already touched upon the issue of sensory substitution and neural recycling, but now, and returning to our BMS example, the question to ask is the following: What about the stick? Does the

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stick play some causal role in the above processes of cross­modal plasticity, and if it does just what role might that be? The striking effects of sensory depriva-tion or lesion in one modality in the development of the remaining modalities (Bavelier & Neville 2002, 443) have been explored in detail over recent decades, but the possible role of external mediations — at the behavioural level — in bringing about and shaping the nature of these changes has received far less atten-tion. Beyond the case of the blind, a much discussed study by Berti & Frassinetti (2000) may offer some additional insights that can prove extremely useful here. As they characteristically remark, simply hold-ing a stick causes a remapping of far space (the space beyond reaching distance) to near space (the space within reaching distance). The significance of the above findings becomes clearer if we bear in mind the unique role which tactile perception plays in combin-ing the ‘efferent’ and ‘afferent’ signals responsible for our sense of self. This process has been extensively investigated in attribution rubber hand experiments showing that ‘tactile perception plays a major role in defining the boundary between the self and the external world’ (Haggard et al. 2003, 173).

This brings us to our second of the previously posed questions: Does the biological boundary of the skin apply in the case of the blind?

Attempting to answer that question it might be useful receding into the phenomenological back-ground of the issue, which may give us a better grasp of the relation between the blind and the stick. Seen from such a phenomenological angle it can be argued that the blind person using a stick does not sense the stick, but the presence or the absence of objects in the outside environment. Although the stick offers the actual means for this exploration it is itself forgotten. As Merleau­Ponty describes:

The blind man’s stick has ceased to be an object for him, and is no longer perceived for itself; its point has become an area of sensitivity, extending the scope and active radius of touch, and providing a parallel to sight. In the exploration of things, the length of the stick does not enter expressly as a middle term: the blind man is rather aware of it through the position of objects than of the position of objects through it. The position of things is immediately given through the extent of the reach that carries him to it, which comprises, besides the arm’s reach, the stick’s range of action (Merleau­Ponty 1962, 143).

The stick, as with many other examples of prosthetic ‘phenomenological osmosis’ (Leder 1990), becomes through time and practice incorporated and thus transparent. Tactile sensation is somehow projected onto the point of contact between the tip of the stick

and the outside environment. Following what we dis-cussed above relevant to the unique role which tactile perception plays in integrating our sense of self, this extension in the body schema could also mean that the brain treats the stick as it were a part of the body. But should we go so far as to conceive of the stick as a structural part of the blind man’s living body and cognitive system?

Part of our inherent difficulty in dealing with questions of the above type stems, I believe, from the dominant representational or computational thinking that characterizes cognitive sciences, in general, and cognitive archaeology, in particular, and the major shortcomings of which I discuss extensively elsewhere (Malafouris 2004; 2007b).

An easy way to overcome this conceptual prob-lem might be by attempting to rephrase our previous question, about how to conceive of the stick as being relevant to the blind man’s living body and cognitive system, using the philosophical perspective of ‘active externalism’ and the so­called ‘parity principle’: When a part of the world — like the blind man’s stick in our case — ‘functions as a process which, were it to go on in the head, we would have no hesitation in accepting as part of the cognitive process, then that part of the world is (for that time) part of the cognitive process’ (Clark & Chalmers 1998). The implications of remov-ing or damaging that part of the world, equals that of removing or damaging a part of the brain. The question thus can be put as follows: Are we not, by removing the blind man’s stick, preventing him from seeing? Or more specifically, are we not preventing the world from touching his visual cortex? This is the point where neuroplasticity meets the extended mind and where one of the major challenges for ‘neuro­archaeology’ arises.

More specifically, this challenge, I suggest, lies in figuring out how our plastic brains and the associated patterns of reorganization, redistribution and scaffolding (Poldrack 2000; Kelly & Garavan 2005; Quartz & Sejnowski 1997) can be understood within the wider extended networks of non-biological props and scaffolds that delineate the real spatial and tem-poral boundaries of the human cognitive map. As we saw, there are many parameters that can be argued to be strongly associated with neuroplasticity and many different levels on which plastic changes can be understood. Even simple daily practice of compli-cated bimanual finger sequences can lead to detect-able gross-anatomical changes in the motor cortex organization. But the key question, at least from an archaeological long-term perspective, should concern the mechanisms that might mediate plastic changes,

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not at the individual, but at the system level. At this broader systemic level material culture competes, equally with any other brain region, for cortical space. It should be noted that there are, at present, no a priori reasons to believe that the mechanisms at play dur-ing cross­modal plasticity differ from those involved in intra­modal plasticity. From the perspective of archaeology and material culture studies it makes good sense to extend this point further, exploring cul-tural change as a form of extra-neural or extra-modal plasticity. With some refinements this is what I have been attempting to do with the BMS hypothesis in this paper. Seen from such an angle, simply to ask about how and why a taxi driver’s ‘grey matter’ enlarges in order to enable the storage of a mental map of the city of London (Maguire et al. 2000) is not enough. For neuroarchaeology and the Material Engagement approach the question that makes the difference is neither simply about brain size nor about the changes in cerebral blood flow; the question is about the ‘leaks’, if I may use the term of Andy Clark (1997; 2003), and the possible transubstantiations of this flow into the external world.

The emergence of self: beads for the body

There are many examples that one could use to illus-trate the implications of the above premises in the context of archaeological thinking. As my case study in this paper I will use the example of self­decora-tion focusing upon one of the earliest well-preserved sample of personal-ornaments in the archaeological record, i.e. the forty­one Nassarius kraussianus shells recovered at the Blombos Cave in South Africa (d’Errico et al. 2005; Vanhaeren & d’Errico 2006). This example will also bring our discussion in contact with the question about the making of modern humans (for a review of the debate see McBrearty & Brooks, 2000; d’Errico et al. 2003; Mellars 2006a,b).

There are three major questions associated with the Blombos shells in this context. First we have the question of their date, secondly we have the question of intentionality and artefactuality and then finally, the question of their representational or symbolic status. Concerning the first two questions there seems to be little doubt that the N. kraussianus shells come from around c. 75 kya and that human agency is responsible for their collection and transformation into beads. Taphonomic, morphometric and microscopic analysis of MSA, LSA, modern and experimentally modified shells provides evidence of human agency and involvement in the shells’ collection, perforation and use as beads (d’Errico et al. 2005). However, the

third question, concerning their possible symbolic function, I believe lacks the systematic treatment that it deserves. Although an emerging archaeological consensus seems to have accepted these artefacts as indexes of symbolic behaviour, I think that simply to prove the artificiality of a perforated shell, and maybe also its function as a personal ornament, does not necessarily make it a symbol — at least not in the arbitrary, representational sense that is often associ-ated with them and which could substantiate a claim for the presence of fully developed symbolic language. I have discussed some of the problems of early sym-bolism and its linguistic grounding elsewhere with special reference to Palaeolithic depictions (Malafouris 2007b). In this paper, instead of tackling directly the question about whether the MSA inhabitants of Blom-bos Cave possessed the famous ‘symbolic capacity’, I want to use the Blombos beads to look at a more basic and largely unexplored dimension of these artefacts. In particular, I want to explore the possible role of these artefacts in the emergence of self-awareness, that is, the question when and how human sense of self developed.

Self–awareness or the experience of selfhood is one of those special features of humanity that we often take for granted. Although, as we saw, archaeology may constantly question the nature of the human cognitive, and in particular symbolic or linguistic, capabilities that can be inferred from the early archaeological record, it rarely ever questions the existence of a fully developed self behind the artefact. The existence of an inner conscious self is taken as a given. However, a wealth of evolutionary, developmental and anthropological studies can easily demonstrate that this is far from the case.

To illustrate this it suffices to look at the different levels of self awareness and types of self knowledge that have been identified from the standpoint of cogni-tive neuroscience and developmental psychology in order to describe what makes up the problem of self. The great variety of conceptual and empirical distinc-tions proposed, ranging from that of a ‘minimal’, ‘pre­reflexive’, ‘bodily’ or ‘ecological’ proto­self to that of a ‘narrative’, ‘reflexive’, ‘conceptual’ or ‘representa-tional’ meta­self (Gallagher 2000; Neisser 1988; Frith 2005; Legrand 2006; Lewis 2003; Rochat 2003) clearly points out that the development of human self aware-ness is a topic far more complicated than is usually assumed in archaeology. For our purposes here, and in order to avoid unnecessary terminological confu-sion, we shall approach the problem of self employing a simple distinction between noetic awareness and autonoetic awareness. The terms noetic and autonoetic

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awareness were initially proposed by Tulving (1983; 2002) but will be used here in a slightly different sense. In particular, noetic awareness will refer to the basic sense of oneself as acting in and on the environment at a time according to one’s first person perspective (1PP). Autonoetic awareness will refer to sense of one-self as a unique individual persisting over time able not only to interact with objects and others according to one’s first person perspective (1PP) but also to reflect on one’s perspective.

Accepting the above basic distinction, the ques-tion that naturally follows is how do we proceed to explore the developmental passage from noetic to autonoetic awareness from a long-term archaeologi-cal perspective? Contrary to other comparative and developmental approaches to the question of self, we can only speculate about some of the possible answers on the basis of the archaeological record. Archaeology lacks, for obvious reasons, the ability to conduct any of the usual ‘mirror self­recognition tasks’ (Gallup 1970; 1992; 1994) and thus we have no direct empirical way to know if and how, the inhabitants of the Blombos Cave would have reacted to the view of their face and body as seen in the surface of the mirror.

However, despite the many methodological problems, the archaeological record can prove particu-larly useful in constraining some aspects of hypothesis building about the emergence of self­awareness. To illustrate this, in what remains of this paper, I will attempt very briefly to elucidate how the evidence for early body-adornment can be seen as indicative of explicit self recognition and objectification, thus offering some valuable information concerning the emergence of human autonoetic awareness. To draw out this dimension of early body-decoration we need to disentangle the referential logic that dominates archaeological thinking and the interpretation of these artefacts from the symbolic. It is precisely in this connection that the BMS hypothesis can offer a new means for approaching the Blombos data set in a way that could serve a similar function to that of the mirror self­identification task. All it takes is a small shift in perspective: instead of seeing the Blombos bead as a ‘symbol’ and thus ‘a reliable proxy for the acquisi-tion of language’ (d’Errico et al. 2005, 20), I propose that it makes better sense if we simply see the shell bead as the equivalent of a ‘Post­It’ sticker placed on a child’s forehead prior to its exposure ‘in a mirror-identification experiment’ (Rochat 2003, 721, fig. 2). In experiments of this kind the child, depending on age, discovers the sticker in the mirror and reaches to touch or remove it. This type of behaviour is taken by many developmental and evolutionary psychologists

as a major cognitive landmark indexing the emergence of a conceptual self (Rochat 2003; Gallup 1970; 1992; 1994). I propose that the perforated Palaeolithic shell bead indexes a similar landmark, only with one impor-tant difference: it does not simply reflect a passage to self-awareness, it brings forth or at least actively contributes to this passage.

A good way to illustrate this can be found in what became known in the case of numerical thinking as ‘basic number sense’, i.e. our ability to approximate large numerical magnitudes, and to identify small numbers of individual objects (oneness, twoness and threeness) (Dehaene 1997; Feigenson et al. 2004). Several lines of evidence clearly support the view that this ‘basic number sense’ can be considered to be an evolved, innate biological competence shared by pre­verbal infants and other animals. However, although we share a common numerical basis with many other animals, none of them seems to be capable of making the mental leap from this basic number sense to the possession of a concept of number — that is, the ability to manipulate large exact numerocities beyond the above­mentioned subitizing range of three or four — even after years of training in a controlled environment (e.g. Biro & Matsuzawa 2001). In fact this mental leap, from approximate to exact numerocity, is of the type that distinguishes the capabilities of the human mind from those of other species.4 The crucial question then, from a long-term perspective, is what drives humans beyond the limits of this core system of approximate numerical thinking? (Feigenson et al. 2004, 313).

I suggest that the development of self­awareness can be conceived of along similar lines. The basic noetic sense of bodily awareness can be demonstrated immediately after birth in infants (Rochat 2003). Moreover, our nearest primate relatives present a number of features indicative of such a proto-self system (Gallup 1994; Damasio 1999). But, similar to what we discussed in relation to the capacity for ‘exact’ numerical thinking, other primates never make the passage to the reflective, conceptual or ‘autonoetic’ stages of selfhood. The question that confronts us then is how did humans move beyond this basic level of ‘core’ (Northoff & Panksepp 2008) proto­self? In other words, how did humans reach this point of autonoetic self­actualization where the self is recognized and experienced not only from within, that is, from a first person perspective (1PP) (Vogeley et al. 2004; Zahavi 2005), but also from a third person’s perspective?

Most researchers dealing with developmental questions of this short — either from an ontogenetic or phylogenetic perspective — would see language as

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playing the key role. For instance in the case of numer-ical thinking there seems to be common agreement that it is language (the presence or absence of number words) that provided the necessary link that enabled humans to move beyond the threshold of approxima-tion (Gelman & Butterworth 2005; Gelman & Gallistel 2004). Without underestimating the importance of language, especially in ontogeny, it can be argued that from a long-term archaeological perspective the above premise cannot easily account for the development of numerical thinking in those early contexts where such verbal numerical competence did not yet exist. In other words, the question for archaeology is not about how you learn to associate the word ten with the quantity 10, but rather about how you conceive the quantity of 10 when you lack a number word to express it. Despite the evident association between language and exact arithmetic, language lacks in itself the necessary ‘representational stability’ (Hutchins 2005) that would have made possible such a transition. I suggest that the world of material things offers the missing link in those cases providing an unlimited recourse for enac-tive signification (For more examples see Malafouris 2007a,b; in press).

Thus, returning to the case of the Blombos beads, I propose that they should be approached and under-stood along the lines of this enactive logic that also occupies the crux of the BMS hypothesis. In particular, I propose that the bead is for the early human self-system as the stick is for the blind person’s perceptual system: The bead, like the stick, offers the necessary scaffolding or ‘surrogate material structure’ (Clark forthcoming) that by effecting an extended reorganization in the cognitive system makes possible the bringing forth of a new type of self­knowledge, i.e. autonoetic aware-ness; a hard, or even impossible process, for a naked brain to realize.

This should not be understood to imply that only shell beads or body decoration could have played that role. Tool use and manufacture, for instance, had already made important contributions to the emergence of human intentionality and the sense of agency and body ownership which are essential for the development of human self-awareness (Malafouris forthcoming). But nonetheless the kind of bodily and cognitive prosthesis that we see in the case of early body-decoration brings some additional ‘epistemic’ qualities that we don’t see — not to the same degree at least — in the case of tool use and manufacture. These special epistemic qualities emanate primarily from the ability of the beads, as material things attached to the body, to transform the phenomenological self­as­subject to a social self­as­object. That is, to make visible and

tangible what is inherently silent and transparent, i.e. the palaeolithic noetic self. This may have played an important role in the emergence of the human ability to be reflectively conscious of one’s own perspective on the world rather than simply being aware of the world.

In particular, attached to the body the bead becomes a visible, corporeal extension of the skin and modification of that body. At the same time, seen as a dual entity that both touches the body and faces outward toward the other, the shell bead can be described as a kind of ‘second’ or ‘social’ skin (Turner 1993 [1980]). However, in its capacity to reshape the body, to which it becomes attached, the shell bead extends ‘peripersonal space’ — i.e. the brain’s repre-sentation of the body and of the space surrounding the body (Holmes & Spence 2006; Holmes et al. 2004, 62; Holmes & Spence 2004; Maravita & Iriki 2004; Maravita et al. 2001; Maravita et al. 2002; Berti & Frassinetti 2000). Because of this the bead also pos-sesses the ability to cross-cut the conventional ‘body image’/‘body schema’ distinctions (Gallagher 2000) thus giving rise to one of the earliest manifestations of what we may call extended or distributed self (see also Malafouris 2008).

More simply, body decoration is capable of liberat-ing the self from the here and now of ordinary experi-ence, that is from the temporal simultaneity and spatial coincidence of the subjective body so it can now be enchained into its social surrounding (see also Knappett 2006). However, the key element or property behind this social enchainment is not the symbolic communication of social identity, such as group membership, gender etc., that many archaeologists have proposed drawing parallels with the function of personal decoration in recent human societies. In the early contexts of human prehistory the presence of reflexive self­awareness and self­other distinction should not be taken for granted. The key element or property here is not ‘symbolism’ but ‘engagement’. The shell bead is important for what it does and not for what it means. Material engagement comes before symbol and is the key to understanding the diverse ways in which agency can emanate from things (see also Gell 1998; Knappett & Malafouris in press; Gosden 2005).

In summary, I suggest that early body ornamen-tation like what we see at Blombos Cave during the MSA should not be understood at first instance as the symbolic elaboration of the hominid brain along the self-other distinction axis, but instead as a possible technique for the gradual emergence of such a distinc-tion. More simply, instead of seeing early ornaments as existing for the self we should be seeing the self as emerging through the ornament.

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We should note that from the perspective of neuroscience recent imaging studies and findings from the neuropsychology of self-disorders provide evidence that our sense of selfhood results from the aggregate of distinct specialized processes performed by a number of different and sub­conscious neuronal networks situated primarily in the right hemisphere (see for review Gusnard 2005; Frith 2005; Decety & Sommerville 2003). As Decety & Sommerville, for example, proposed recently, the self can be seen as a multi-dimensional construct that relies on a distrib-uted neural network (a collection of interconnected predominantly right-hemisphere based prefrontal, posterior temporal and inferior parietal regions) that encompasses shared self–other representations and is essential for the subjective experience of a ‘self’ (Decety & Sommerville 2003).

However, as we argued in the previous section, any intracranial conception of the human mind and by extension of self, should be resisted (see also Mala-fouris 2008). No doubt the representational properties of neural networks, like those that subserve the human sense of self, become realized inside the head, but for the BMS hypothesis the systemic properties of the cognitive structures from which they derive extend beyond skin and skull. By that I do not simply refer to an activity-dependent change in the neural archi-tecture (whether by adding new processing nodes or connections among them). Instead I am referring to an outward expansion of the cognitive system so as to include and incorporate extra-neural nodes real-ized through body and culture. In the latter view, it is the ornament itself that has partially driven and mediated the transformation of the bodily self to a self­in­context­of­the­other by effecting an extended re­organization on the neural networks that subserve the human ‘right hemisphere interpreter’ (Gazzaniga 1998).

Some concluding thoughts

But where does all this leave us when it comes to the question of the origin of human modernity? What does the BMS hypothesis add to the ongoing debate over the making of modern humans and in what way does it help us to rethink what traits mark the origin of our species? By way of concluding this paper I want briefly to summarize a few major points.

Whichever list of early modern human behav-ioural traits one chooses — Eurocentric or not (see Henshilwood & Marean 2003) — and whatever the precise model of change one subscribes to — gradu-alistic or sudden — there are two major and deeply

entrenched assumptions behind the debate over the origin of modern human intelligence. The first implicit assumption is that brain anatomy and structure stayed the same after the main speciation event, whenever and wherever we decide to situate that. The second implicit assumption is that material culture, although it can be seen to reflect possible changes (genetic or other) in human cognition, has no causal efficacy or other direct relationship with the mechanisms that underlie these changes and which should be sought in the domain of human biology.

From the perspective advanced in this paper the former assumption can no longer be sustained. At least it cannot be sustained without some further qualifica-tions or more precise definitions concerning what it is about the human brain that remains the same. For instance, although as recent DNA studies point out (Mellars 2006a,b), the human genetic structure does not seem to have changed much (Renfrew 2008), the human brain almost certainly has. If the intrinsically plastic human brain undergoes constant change subject to various developmental, environmental and cultural factors, then it cannot simply be assumed that anatomically modern human intelligence refers to a fixed and stable speciation event. It appears instead that a plastic brain is always amenable to drastic deep re­organization and thus, potentially, to a constant, ‘pre-modern’ state of change and ongoing cognitive evolution.

One should bear in mind in this context that the development in neuroscience of new theoretical frameworks such as that of ‘neuroconstructivism’ (Westermann et al. 2007; Quartz & Sejnowski 1997; Quartz 1999) and ‘probabilistic epigenesis’ (Gottlieb 2003; 2007) provides us a new, non­linear and interac-tive model for understanding the relationship between genes, the brain and behaviour that characterize human cognitive becoming. In particular, cognitive development is no longer seen as the progressive unfolding of information that is laid out in the genome. The traditional view of a one­directional flow of cause and effect from genes (DNA) to RNA to the structure of proteins which they encode gives way to a more subtle picture where physical, social, cultural aspects of environment and behaviour play fundamental role in triggering the expression of genes (Westermann et al. 2007, 76).

Thus although we can debate the usefulness of notions like cognitive or behavioural modernity which dominate archaeological thinking (see for review d’Errico 2003; d’Errico et al. 2003; Mellars 1989; 1991) and are relevant to some dimensions of human cognitive evolution (e.g. syntactical language), as far

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as the broader issue of human cognitive becoming is concerned, I suggest that the words of Bruno Latour (1993) ‘we have never been modern’ can be seen to apply well. For the BMS hypothesis the hallmark of human cognitive evolution may not to be based on the ever­increasing sophistication or specialization of a modular mind, but upon an ever-increasing extra­neural representational flexibility that allows for environmentally and culturally derived changes in the structure and functional architecture of our brain.

This brings us to the second of the previously stated assumptions concerning the epiphenomenal role of material culture in human cognition. A major methodological implication which the BMS hypothesis carries with it is that the observed changes in the mate-rial record should also be seen as indicative of possible plastic effects, that is, of effected changes in human cognition, rather than simply reflective of pre­existing cognitive or genetic changes. The direction of inferred causation must change. This does not necessarily mean that any change in the material record coincided pre-cisely with fundamental changes in human cognition. What it means, instead, is that we need to overcome the ‘representational fallacy’ that characterizes most stud-ies in human cognitive evolution and which continues to see material culture as an epiphenomenal product of the human mind. For the BMS hypothesis material culture is not simply the product of cognitive change but also one of the possible reasons behind it. The shell bead from Blombos is not a symbolic statement about the presence of a new human representational capacity and thus the origins of human modernity. Instead it is a statement about how culture shapes the brain and thus provides a concrete example of how external processes and artefacts can be seen as constitutive aspects of the constantly changing and extended anatomy of human intelligence (see also Jordan 2008). Although separating biology from culture sometimes makes good analytic sense for approaching some archaeological problems, it should not obscure the most interesting issue of how they are combined (Renfrew et al. 2008; Gibson 1996; Knappett 2005; Gamble 2007). Maybe instead of looking for clean lines and clear-cut stages in human cognitive evolution we should be seeking a more discontinuous and interactionist view; a view capable of recognizing that ‘the mental characteristics of the system are imma-nent, not in some part, but in the system as a whole’ (Bateson 1973, 316).

Acknowledgements

The author would like to thank two anonymous reviewers, as well as Colin Renfrew, Carl Knappett and John Robb

for their helpful comments and suggestions. The research presented here was funded by the Balzan Foundation and by a ‘European Platform for Life Sciences, Mind Sciences, and the Humanities’ grant (Volkswagen Stiftung).

Lambros MalafourisMcDonald Institute for Archaeological Research

Downing StreetCambridge

CB2 3ERUK

Email: lm243@cam.ac.uk

Notes

1. I should clarify that environmental enrichment refers to housing conditions, either home cages or exploratory chambers, that facilitate enhanced sensory, cognitive and motor stimulation relative to standard housing conditions (for a good review see Nithianantharajah & Hannan 2006).

2. Hebb (1949) postulated that synaptic efficacy between two neurons is strengthened if the first repeatedly contributes to firing the second.

3. We should note that the use of electrical stimulation to alter brain function by injecting a signal to monkeys and humans goes back in the 1960s, and today Deep Brain Stimulation (DBS) and the implantation of physical devices into the brain is increasingly used to treat neu-rological disorders (Donoghue 2002). But the possibility that these new hybrid BMIs seem to have realized for the first time is that of establishing an interactive communica-tion link between the functioning human brain and the outside world. For instance, BMIs are now capable of controlling a robotic hand by ‘thought’ alone, thus restor-ing or enhancing our perceptual, motor and cognitive capabilities. A characteristic example can be seen in the case of the EEG­controlled web browser based on self­regulation of slow cortical potentials (SCPs) developed by Karim et al. (2006) which enables patients with severe or total motor paralysis — often referred to as ‘locked­in syndrome’ — to browse the internet independently of any voluntary muscle control.

4. Although most people today take the notion of abstract number for granted, we should not forget the mental leap required to go from counting specific things (concrete counting) to the abstract concept of number as a representation of quantity. The making sense of an exact, large cardinal value, presupposes cognitive processes that children take many years to learn and that people may perform in different ways in different cultures or even lack altogether.

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