From Towards a Science of Consciousness 3
Section 6: Evolution and
the Function of Consciousness CogNet
Proceedings
As an archaeologist my interest is not with consciousness as raw sensation, but with high level, access or reflective consciousness-consciousness in terms of thoughts about our own thoughts and about our feelings; consciousness in terms of knowing about one's own mind. This is quite different from consciousness in terms of being and feeling that I guess is the root the matter: those roots are buried much too deep in our evolutionary past for an archaeologist to find; they may go back way before the first hominid like creature appeared on the earth perhaps as Stuart Hameroff (1998) suggests to the Cambrian explosion itself. As an archaeologist concerned with just the last 6 million years of evolution I have what might be the trivial problem to address, no more than the twigs, the buds and then the final flowering of consciousness.
To address this, the first task is to rid our own minds of the idea that the evolution of consciousness is something that can be considered in isolation from that of thought, language, behavior and material culture. These were inextricably linked to each other during cognitive evolution, although the role they played changed as they themselves evolved. This is, of course, quite familiar and obvious. Consider language and thought, for instance. There is a long intellectual history stretching back to Plato's Theateteus of considering the relationship between these (Preston 1997); more recently in the work of psychologists such as Vygortsky (1962 [1934]), philosophers such as Dennett (1991) and Clark (1996), linguists such Lock (1993) and Bickerton (1996), and neuroscientists such as Calvin (1997), the notion of language as a tool for thought as much as a tool for communication has gained much support. I am in absolute agreement with this and think that there has been too much stress on language as a tool for communication in the recent work on the evolution of language (e.g., Dunbar 1996). As such, the evolution of reflexive consciousness appears most likely to be entwinned with that of modern language.
The content of the archaeological record suggests that material culture may play a similar role to that of language in terms of structuring, perhaps forming, our thoughts and consciousness. The artefacts from the prehistoric and modern worlds were/are not just tools for hunting animals or using the internet; nor for just decorating bodies or our homes. Material artefacts are as much tools for thought as is language: tools for exploring, expanding, and manipulating our own minds and by that process ridding ourselves of the shackles imposed on our thinking by our evolutionary past. In this regard the evolution of material culture is inextricably linked with the evolution of consciousness. At least, that is the argument I would to pursue in this short chapter.
Homo sapiens sapiens is closely related to the great apes, having shared a common ancestor with the chimpanzee between 5 and 6 million years ago. It is, of course, usual practice, to assume that cognitively this common ancestor was much like the chimpanzee today. That may be true; or it may be a grave mistake as the chimpanzee mind has also undergone 6 million years of evolution since the common ancestor. But the most reasonable assumption is that the mind of the common ancestor was similar to that of the chimpanzee today, and consequently is likely to lack a fully modern form of reflexive consciousness. As such, this evolved at sometime during the last 6 million years and as the majority of behavior during that period is documented by the archaeological record inferences should be possible as to when, where and within which species this occurred.
Between 4.5 and 1 million years ago, there are several australopithecine species known to us, and probably several more that remain undiscovered. The most famous is Lucy, A. afaraensis, with her joint arboreal and terrestrial adaptation. The emergence of large brained hominids after 2 million years ago, who were manufacturing Oldowan stone tools and eating greater quantities of meat seems likely to be tied up with significant cognitive developments. The most important of these species is H. ergaster, best represented by the fossil skeleton known as the Nariokotome boy, which displays various preadaptations for linguistic abilities (Aiello 1996). H. ergaster appears to have been the species that diversified and dispersed throughout the Old world soon after 2 million. In Asia distinct species such as H. erectus and archaic H. sapiens evolved, while in Europe we find H. heidelbergensis and then the Neanderthals. All of these species were evidently capable of making complex stone artefacts, such as handaxes, and after 250,000 years ago, levallois flakes and points. They lived in a variety of challenging environments, were able to hunt big game and to live in large, socially complex groups. After 250,000 years ago, several hominid species had brains as large as ours today. But their behavior lacks any sign of art or symbolic behavior beyond pieces such as the engraved Bilzingsleben bones with a few parallel incisions, the purpose of which are quite unknown, and the so-called Berekhat Ram figurine just a few centimetres high but apparently intentionally incised by stone artefacts. This is claimed to be a female figurine (Marshack 1997) and, as such, the earliest piece of representational art.
If we follow the Out of Africa origins for modern humans (Stringer and McKie 1996), then we see H. sapiens sapiensfirst appearing in Africa sometime before 100,000 years ago with the earliest traces being found at Omo Kibish and Klasies River Mouth, and soon after at the caves of Qafzeh and Skhul in the Levant. Modern humans then dispersed throughout the Old and New Worlds replacing all other types of humans so that by 28,000 Homo sapiens sapiens was the only surviving member of our genus on the planet. After 50,000 years ago we have unambiguous traces of art and symbols, notably the cave paintings from France first found 30,000 years ago; prior to this we have a few ambiguous traces for art, ritual and symbolic behavior by anatomically modern humans, such ochre crayons from Klasies (Knight et al. 1995).
It is at some time during this evolutionary history that modern forms of consciousness evolve: whether catastrophically or gradually is unknown, whether restricted to just our species or common to all Early Humans remains unclear.
With regard to consciousness handaxes provide us with a dilemma, indeed a paradox. On the one hand there can be no question that these artefacts are very challenging to make. This has been demonstrated by many replicative studies and we now have detailed understanding of the knapping procedures used by early humans (e.g., Pelegrin 1993). Often nonarchaeologists speculate that handaxes are equivalent to the complex artefacts made by other animals, such as a beaver's dam, a honeycomb or a spiders web: all complex artefacts with degrees of symmetry but which require neither intelligence nor conscious thought to produce. Well such comparisons are ill founded. A reductive technology is necessary to make a handaxe. One must begin with a nodule of stone and employ a range of different hammers and methods of fracture to achieve the final product. There is a great deal of unpredictability involved: unexpected contingencies arise, plans need to be continually modified. One simply cannot iterate a fixed action routine to produce a handaxe as a spider or a beaver might use for their artefacts. Making a handaxe is a completely different mental ball game. It is one that requires a degree of consciousness, one needs thoughts about thoughts.
The paradox is that the remarkable technological stasis that endured during the Middle Pleistocene (Mithen 1996) suggests that the technical intelligence these hominids possessed was quite unknown to them; that it was something excluded from whatever higher level consciousness that they did possess. So while the form of handaxes tells us that hominid were conscious about their technical knowledge, the distribution of these artefacts in space and time tells us the opposite. Let me suggest how this paradox may be resolved.
First we must be a bit more specific and recognised that there are at least four types of knowledge that need to be brought together in the mind for handaxe production (figure 24.2). Each of these four mental components appear to have become part of an evolved psychology long before the first handaxes were manufactured.
First one needs a high degree of sensory motor control. Nodules, pre-forms, and near finished artefacts must be struck at precisely the right angle with precisely the right degree of force if the desired flake is to be detached. It seems unlikely that such sensory-motor control would have been selected for making handaxes themselves. A more likely origin is related to encaphalization and bipedalism. As Leslie Aiello (1996) has discussed, with a large brain there can be a relatively high degree of complex sensory-motor control of the body owing to the increased number of nerve tracts and the increased integration between them allowing for the firing of smaller muscle groups. According to Aiello, bipedalism that requires a more complex integrated system of balance than quadrupedal locomotion, presupposes a complex and highly fractionated nervous system, which in turn presupposes a larger brain. As substantial encaphalization and bipedalism had arisen prior to theappearance of handaxes in the archaeological record, it is evident that Early Humans were preadapted for the sensory motor-control required to make handaxes.
The earlirst hominids prior to the appearance of handaxes also appear to have had a sufficient degree of understanding about fracture dynamics to allow the manufacture of handaxes. This is evident from both the production of Oldowan tools, and from tool use by chimpanzees. As has been made clear by the experimental work of Toth (1985) and Pelegrin (1993), Oldowan tools makers were not simply bashing rocks together (or at least not always). Many choppers and flakes provide distinct traces that Oldowan knappers 2.5 million years ago were able to identify appropriate natural platforms for striking and were selecting hammerstones of appropriate weight and striking at appropriate angles and force. It is also evident from studies of nut cracking by chimpanzees (Boesch and Boesch 1983), that with sufficient experience the direction and power of striking by these animals can be adjusted to crack nuts without destroying the kernel.
A third feature of handaxe manufacture is planning: flake removals happen in a sequential fashion to allow one to move from a nodule to a roughout to a finished artefacts. Each removal both detaches a flake and paves the way for removal of future flakes, perhaps those of a different type. To make a handaxe one must plan; but one must also be flexible, able to modify the plan and react to contingencies, such as unexpected flaws in the material and miss-hits.
Again we can see evidence of planning in the minds of Oldowan tool makers, and in chimpanzees today. With regard to the early hominids there is clear evidence of the transport of artefacts and parts of carcasses around the landscape; these may not have been for great distances but planning with flexibility is clearly required (Potts 1988). We can also see this to some degree in chimpanzee tool use: artefacts such as termite sticks are trimmed to appropriate lengths, sequential uses of tools have been observed, and hammers carried to nut cracking sites in anticipation of use (McGrew 1992). So as with fine-sensory motor control, the ability for planning ahead is likely to have been selected for reasons unrelated to handaxe manufacture and to have already been part of an evolved psychology prior to the first production of handaxes.
The fourth significant feature of handaxe manufacture is the imposition of symmetry. In many handaxes, especially the early protobifaces, this may be no more than an unintentional by-product of the bifacial knapping technique. But in others, the removal of fine trimming flakes is a clear indicator that symmetry was deliberately imposed (Wynn 1995). Now an attraction toward symmetry is also likely to have been part of an evolved psychology, stretching way back in evolutionary time. Many animal species appear to use symmetry as a clue to the genetic health of potential mates (e.g., Møller 1990, Manning and Chamberlain 1993, Manning and Hartley 1991). Also, an evolved ability to perceive and pay attention to symmetry may have been crucial in social interaction and predator escape, as it may allow one to recognise that one is being directly stared at (Dennett 1991). Hominid handaxe makers may have been keying into this attraction to symmetry when producing tools to attract the attention of the other hominids, especially those of the opposite sex. But what is important with regard to consciousness, is that this attraction to symmetry is likely to have evolved for reasons quite unrelated to handaxe manufacture.
It is apparent, therefore, that the four mental resources for handaxe manufacture evolved independently, and were present in the minds of hominids long before the first handaxes were produced. How were these resources combined to produce what I would call the technical intelligence (Mithen 1996) of the Early Human mind? And how does this relate to language and consciousness.
The argument I would like to make is that private speech played a critical role, and here I want to draw directly on Dennett's (1991) arguments for auto-stimulation, or speaking to oneself. He has described this as functioning to "blaze a new trail through one's internal components." Such private speech seems to me as the only means by which that trail between planning, fracture dynamics, motor control and symmetry could have been forged in the early human mind. His figure from Consciousness Explained,which can be modified quite easily to relate to handaxe production to suggest how several modules were bundled together to create a cognitive domain within the early human mind (figure 24.3). Here, therefore, we return to the relationship between language and thought. There are many studies and ideas that could be invoked to develop this argument. The most relevant for the evolution of thought and consciousness at 2 million years ago seem to be those by Andrew Lock (1980), arguing that for the child, language makes explicit what is already implicit in his abilities, and by Laura Berk (1994) that a child's private speech is a crucial cognitive tool for problem solving.
So my argument is that when our ancestors made handaxes there were private mutterings accompanying the crack of stone against stone. Those private mutterings were instrumental in pulling the knowledge required for handaxe manufacture into an emergent consciousness. But what type of consciousness? I think probably one that was fleeting: one that existed during the act of manufacture and that did not then endure. One quite unlike the consciousness about one's emotions, feelings, and desires that were associated with the social world and that probably part of a completely separate cognitive domain, that of social intelligence, in the early human mind (Mithen 1996).
Using private speech in handaxe manufacture is but one instance, I would argue, of how early humans began to manipulate, explore and expand there own minds by clever tricks. This clever trick probably evolved hand in hand with another: talking to each other. Both private and public language act as tools for thought and play a fundamental role in the evolution of consciousness: in the opening up of our minds to ourselves. But during the course of the latter stages of human evolution, another tool was found that may have had even greater consequences for the evolution of consciousness: material culture itself.
Now the modern human mind overcame the barriers between domains so that different types of knowledge and ways of thinking became integrated (figure 24.5). Public language was instrumental. As I discuss in Mithen (1996) he capacity for this is likely to have co-evolved with social intelligence and once public language was used for talking about the nonsocial world, such as about making artefacts and hunting animals, the barriers between those the worlds of society, nature and artefacts collapsed. But I now see that this argument was wrong; or rather not as right as it could have been. For I now see that the material culture itself was not just a product of a massive cognitive change, but also a cause of it. An evolved psychology cannot be so easily escaped as I had imagined and the clever trick that humans learnt was to disembody their minds into the material world around them: a linguistic utterance might be considered as a disembodied thought. But such utterances last just for a few seconds. Material culture endures.
To illustrate my argument consider the first, unambiguous representational art, that from the last ice age about 30,000 years ago. Specifically, consider the carving of what most likely is a mythical being from the last ice age, a half human/half lion figure carved from mammoth ivory found at Hohlenstein Stadel, Germany (figure 24.6). An evolved mind is unlikely to have a natural home for this being, as such entities do not exist in the natural world: so whereas evolved minds could think about humans by deploying content rich mental modules moulded by natural selection, and about other lions by using other content rich modules from the natural history cognitive domain, how could one think about entities that were part human and part animal? Such entities had no home in the mind. Indeed how can one come up with the idea in the first place.
As I have previously argued a cognitively fluid mind can come up with such entities (figure 24.7), as I show here, but where then to store that entity? The only option is to extend the mind into the material world. Dispense with a reliance on brain stuff and get into rocks and painting, ivory and carving. So artefacts such as this figure, and indeed the cave paintings of the last ice age, functioned as anchors for ideas that have no natural home within the mind; for ideas that take us beyond those that natural selection could enable us to possess. So a better representation of how thoughts about supernatural beings are maintained and manipulated is that of figure 24.8. Without the material culture to disembody such thoughts, they would simply dissipate, there could be no fidelity in transmission to another individual or when the idea is recreated within one's own mind (Mithen 1997).
More generally the remarkable developments of material culture after 50,000 years ago should not be seen simply as the manifestation of a new level of consciousness. They are as much a cause as a product. They allowed people to explore, expand, manipulate and simply play with their own knowledge in ways that other humans, even those with private and public language, were unable to do. By doing this, humans loosened, perhaps cut, those shackles on our minds imposed by our evolutionary past. Shackles that always bound the minds of other humans types, such as the Neanderthals.
Aiello, L. 1996. Hominine preadaptations for language and cognition. In Modelling the Early Human Mind, Ed. P. Mellars and K. Gibson, pp. 89-99. Cambridge: McDonald Institute for Archaeological Research.
Berk, L. 1994. Why children talk to themselves. In Scientific American 271, no. 5:78-83.
Bickerton, D. 1996. In Human Behavior and Language. London: UCL Press.
Boesch, C., and H. Boesch. 1983. Optimization of nut cracking with natural hammers by wild chimpanzees. In Behavior 83:265-86.
Calvin, W. 1997. How Brains Think: Evolving Intelligence, Then and Now. London: Weidenfeld and Nicholson.
Clark, A. 1996. Being There: Putting Brain, Body and World Together Again. Cambridge, Mass.: MIT Press.
Dennett, D. C. 1991. Consciousness Explained. London: Penguin
Dunbar, R. 1996. Gossip, Grooming and the Evolution of Language. London: Faber and Faber.
Hameroff, S. 1998. Did consciousness cause the Cambrian evolutionary explosion? In Toward a Science of Consciousness II: The Second Tucson Discussions and Debates. Ed. S. R. Hameroff, A. W. Kaszniak and A. C. Scott, pp. 421-437. Cambridge Mass.: MIT Press.
Isaac, G. 1977. Olorgesailie. Chicago: Chicago University Press.
Jones, S., R. Martin, and D. Pilbeam. (Eds.) 1992. The Cambridge Encyclopedia of Human Evolution. Cambridge: Cambridge University Press.
Kohn, M., and S. Mithen, S. (no date) Handaxes as products of sexual selection. Unpublished manuscript.
Knight, C., C. Powers, and I. Watts. 1995. The human symbolic revolution: A Darwinian account. In Cambridge Archaeological Journal 5:75-114.
Lock, A. 1980. The Guided Reinvention of Language.London: Academic Press.
Lock A. 1993. Human language development and object manipulation: Their relation in ontogeny and its possible relevance for phylogenetic questions. In Tools, Language and Cognition in Human Evolution Ed. K. R. Gibson and T. Ingold, pp. 279-298. Cambridge: Cambridge University Press.
Manning, J. T., and M. A. Hartley. 1991. Symmetry and ornamentation are correlated in the peacock's train. In Animal Behavior 42:1020-1021.
Manning, J. T., and A. T. Chamberlain. 1993. Fluctuating asymmetry, sexual selection and canine teeth in primates. In Proceedings of the Royal Society of London, Series B, 251:83-87.
Marshack, A. 1997. The Berekhat Ram figurine: A late Acheulian carving from the Middle East. In Antiquity 71:327-37.
McGrew, W. 1992. Chimpanzee Material Culture. Cambridge: Cambridge University Press.
Mithen, S. 1996. The Prehistory of the Mind. London: Thames and Hudson.
Mithen, S. 1997. Cognitive Archaeology, Evolutionary psychology and cultural transmission with particular reference to religious ideas. In Rediscovering Darwin: Evolutionary Theory in Archaeological Explanation, Ed. C. M. Barton and G. A. Clark, pp. 67-86. Archaeological Papers of the American Anthropological Association, no. 7.
Møller, A. P. 1990. Fluctuating asymmetry in male sexual ornaments may reliably reveal male quality. In Animal Behavior 40:1185-1187.
Pelegrin, J. 1993. A framework for analysing prehistoric stone tool manufacture and a tentative application to some early stone industries. In The Use of Tools by Human and Non-human Primates, Ed. A. Berthelet and J. Chavallion, pp. 302-14. Oxford: Clarendon Press.
Potts, R. 1988.Early Hominid Activities at Olduvai Gorge. New York: Aldine de Gruyter.
Preston, J. 1997. Introduction: Thought as Language. In Thought and Language Ed. J. Preston, pp. 1-14. Cambridge: Cambridge University Press. Royal Institute of Philosophy Supplement, 42.
Roe, D. 1981. The Lower and Middle Palaeolithic Periods in Britain. London: Routledge and Kegan Paul.
Schick, K., and N. Toth. 1993. Making Silent Stones Speak: Human Evolution and the Dawn of Technology. New York: Simon and Schuster.
Stinger, C., andR. McKie. 1996. African Exodus: The Origins of Modern Humanity. London: Pimlico.
Toth, N. 1985. The Oldowan reassessed: A close look at early stone artefacts. In Journal of Archaeological Science 12:101-20.
Villa, P. 1983. Terra Amata and the Middle Pleistocene Record from Southern France. Berkeley: University of California Press
Vygotsky, L. S. 1962 (1934). Thought and Language. Cambridge: MIT Press.
Wynn, T. 1995. Handaxe enigmas. In World Archaeology 27:10-23.
Wynn, T., and F. Tierson. 1990. Regional comparison of the shapes of later Acheulian handaxes. In American Anthropologist 92:73-84.