Reference:
Gabora, L. (2007). Mind. In (R. A. Bentley, H. D. G. Maschner, & C. Chippendale, Eds.) Handbook of Theories and Methods in Archaeology, Altamira Press, Walnut Creek CA, (pp. 283-296).
Chapter 17: Mind
Liane Gabora
University of British Columbia[1]
Introduction: What Can
Archaeology Tell Us about the Mind?
What can relics of
the past tell us about the thoughts and beliefs of the people who invented and
used them? Recent collaborations at the frontier of archaeology, anthropology,
and cognitive science are culminating in speculative but nevertheless
increasingly sophisticated efforts to unravel how modern human cognition came
about. By considering objects within their archaeological context, we have
begun to piece together something of the way of life of people who inhabited
particular locales, which in turn reflects their underlying thought processes.
Comparing data
between different sites or time periods tells us something about the horizontal
(within generation) or vertical (between generations) transmission of material
culture. In addition to patterns of transmission of existing kinds of
artifacts, we are also interested in novel artifacts that might be indicative
of new cognitive abilities, belief structures, or levels of cooperation. An
archaeological period marked by the sudden appearance of many kinds of new
objects may suggest the onset of enhanced creative abilities. By corroborating
archaeological findings with anthropological data (evidence of sudden change in
the size or shape of the cranium, for example) with knowledge from cognitive
science about how minds function, we can make educated guesses as to what kinds
of underlying cognitive changes could be involved, and how the unique abilities
of Homo sapiens arose.
In
this chapter, we consider three questions about human cognition that can be
addressed through archaeological data: (1) How did human culture begin? (2) Where,
when, and how did humans acquire the unique cognitive abilities of modern Homo
sapiens? and (3) What role do artifacts play in the evolution of these
cognitive abilities?
(1) The Origin of Human
Culture
The earliest known
artifacts, referred to as Oldowan -- after Olduvai Gorge, Tanzania,
where they were first found -- were simple stone tools, pointed at one end
(Leakey 1971), and widely associated with Homo habilis, although it is
possible that they were also used by late australopithecenes (de Baune 2004).
The oldest of these Oldowan tools, from Kada Gona and Kada Hadar, date to
approximately 2.5 million years ago (Semaw et al. 1997). The earliest use of stone tools was probably
to split fruits and nuts; "the moment when a hominin ...produced a cutting
tool by using a thrusting percussion ...marks a break between our predecessors
and the specifically human" (de Baune 2004:142). With sharp edges, Lower
Palaeolithic tools could be used to sharpen wood implements and occasionally
butcher small game. Using the sharp flakes associated with these tools, Homo
habilis butchered animals for meat, as these tools are found in context with
cut-marked bones at the FLK Zinj site (1.75 Ma) in the Olduvai Gorge (Leakey
1971; Bunn and Kroll 1986). Although it has been debated whether they were
scavenging, hunting, or “power scavenging” by scaring carnivores away (e.g.,
Binford 1977; 1983, 1988; Bunn and Kroll 1986; Selvaggio 1998), it is clear
that these hominids were capable of acquiring the richer, more meat-rich portions
of a kill (Bunn and Kroll 1986). This may have introduced a positive feedback
cycle, in that meat eating, by allowing a smaller gut, provided metabolic
support for a larger brain (Aiello and Wheeler 1995) which, in turn, would
improve cognitive ability for group hunting using mental landscape maps,
interpretation of visual clues such as animal tracks, and knowledge of predator
behavior.
With the arrival
of Homo erectus by
1.8 Ma, we see sophisticated, task-specific stone hand axes, complex stable seasonal
habitats, and long-distance hunting strategies involving large game. The size
of the Homo erectus brain was approximately 1,000 cc, about 25% larger
than that of Homo habilis, and 75% the cranial capacity of modern humans
(Aiello 1996; Ruff et al.
1997; Lewin, 1999). By 1.6 Ma, Homo erectus had dispersed as far as
Southeast Asia (Swisher et al. 1994), indicating the ability to migrate and
adapt to vastly different climates (Cachel and Harris 1995; Walker and Leakey
1993; Anton and Swisher 2004). In Africa, West Asia, and Europe, Homo erectus
carried the Aschulean handaxe, which was present by 1.4 Ma in Ethiopia (Asfaw
et al. 1992). A do-it-all tool that may even have had some function as a social
status symbol (Kohn and Mithen 1999) these symmetrical biface tools probably
required three stages of production, bifacial knapping, and considerable skill
and spatial ability to achieve their final form. The handaxe persisted as a
tool of choice for over a million years, spreading by 500 ka into Europe, where
was it used by H. heidelbergensis until the Mousterian at about 200 ka. This
period also marks the first solid evidence for controlled use of fire, by 800
ka in the Levant (Goren-Inbar et al. 2004). A 400,000 year-old,
fire-hardened wooden spear found at Schöningen, Germany (Thieme 1997) shows
beyond doubt that Middle Pleistocene Homo were sophisticated big-game
hunters (Dennell 1997).
Cognitive
Theories of How Culture Began
By a half million
years ago the complexity of Homo culture was already beyond that of any
other species (Darwin 1871; Plotkin 1988). What got the ball rolling, enabling
the process of enculturation to take hold? One suggestion
is a theory of mind (Cheney and
Seyfarth 1990; Premack and Woodruff 1978), which refers to the capacity to reason about the mental states of others,
such as interpreting the intentions of another through his/her actions. However, there is abundant evidence that many
species are capable of social attribution and deception, indicating that theory of mind is not unique to humans (Heyes 1998).
Moreover, the invention of tools, taming of fire, and conquering of new
habitats could not have been achieved solely through enhanced social skills; it
would have required enhanced mastery of the physical environment.
Another suggestion is that culture arose due to onset of the
capacity for imitation (Dugatkin 2001; Richerson and Boyd 1998).
However, imitation is widespread among animals such as dolphins, dogs, primates, and
birds (Bonner 1980; Byrne and Russon 1998; Lynch and Baker 1994; Robert 1990;
Smith 1977). Moreover there is no evidence, empirical
or theoretical, that imitation-like social learning processes (or simple
manipulations of them such as a bias to copy high prestige individuals) are
sufficient for cultural evolution. To get the kind of adaptive modification and
diversification of stable form found in culture (and biology) requires entities
that possess an integrated, self-modifying structure wherein changes to one
part percolate to other parts with context-sensitive effects, such that
different structures can potentially result. Artifacts, habits, and other
socially acquired elements of culture do not on their own possess such a
structure.
A third proposal
is that Homo underwent a transition from an episodic mode of
cognitive functioning to a mimetic mode (Donald 1991). The early
hominid, functioning in the episodic mode, was sensitive to the significance of
episodes, could encode them in memory, and coordinate appropriate responses,
but not voluntarily access them independent of environmental cues. Thus
awareness was dominated by what was happening in the present moment. Donald
maintains that with encephalization (brain enlargement) Homo acquired
the capacity for a ‘self-triggered recall and rehearsal loop’. which basically
amounts to the capacity for a stream of thought in which one idea evokes
another which evokes another and so forth recursively. This
process, sometimes referred to by psychologists as representational
redescription (Karmiloff-Smith, 1992), allowed hominds to direct
attention away from the external world toward internal thoughts, planned
actions, or episodes encoded in memory, and access
them at will. This gave rise to a mimetic mode of cognitive functioning.
The term comes from the word ‘mime’ or ‘pantomime’, and indeed Donald stresses
onset of the ability to act out events that may have occurred in the past or
could occur in the future. Thus the mimetic mind is able to not only escape the
here and now, but through gesture facilitate a similar temporary escape from
the present in other minds. This provided a way of sharing knowledge and
experience without language, and may have been our earliest means of cultural
transmission. Self-triggered thought also enabled hominids to evaluate and improve skills through repetition or rehearsal.
The
Underlying Memory Structure: Fine-grained Distributed Representations
The
mimetic mode rests heavily on the capacity to generate previous or imagined
episodes or motor acts and adapt them to the present situation. How might it
have come about, and why would it be enhanced by encephalization? To answer
this we look briefly at the structure of memory. Episodes etched in memory are distributed
across a cell
assembly (a bundle of brain cells) that contains many locations, and likewise,
each location participates in the storage of many items. Thus the same memory
locations get used and reused (neural re-entrance). Each memory location
is sensitive to a range of subsymbolic microfeatures: primitive
attributes of a stimulus or situation. This kind of architecture is said to be content-addressable
because similar or related items activate, and get encoded in, overlapping
memory regions. Now
imagine a hominid observing various features of the landscape. Memory location A
may respond preferentially to lines oriented at say 45 degrees from the
horizontal, neighboring location B to lines at a slightly different
angle, say 46 degrees, and so forth. However, although A responds maximally to lines of 45 degrees, it
responds to a lesser degree to lines of 46 degrees. This kind of organization
is referred to as coarse coding. Thus for example, location A
participates in the storage of all those memories involving lines at close to
45 degrees, and a particular episode affects not just A but many other
locations. We refer to this constellation of locations as the cognitive receptive field (CRF) for
that episode.
As brains size
increased, CRFs became larger. This enables more fine-grained encoding
of episodes in memory, which
makes the memory more prone to self-triggered thought. Consider, for example, an episode that involves getting
pricked by a thorny cactus. A small brain might encode this episode in terms of
a few features (Figure 1a), such as perhaps the pain involved, and some
recognizable feature such as its overall shape or color. This would aid
avoidance of contact with this cactus in the future, and perhaps similar cacti.
However, that would be the extent of this episode’s usefulness. A larger brain,
though, might include in the CRF additional features (Figure 1b), such as the
sharp point of the thorn. The encoding of an episode constituted by both
pointed shape and torn flesh means that there is an association between these
properties. Some time later, the need to kill prey may activate the memory
locations involved in the encoding of torn flesh, leading to the retrieval of
the entire episode, including the pointed shape, and thereby aid in the
invention of a spear. Hence the transition from coarse coding, wherein
episodes tend to be encoded separately, to fine-grained coding, whereby
episodes overlap and can thereby be associated, may have brought the capacity
for abstract relationships. Such relationships constitute the stepping
stones via which abstract streams of thought occur (through representational redescription), and by which an
internal model of the world is acquired and thereafter honed as new information
is continually integrated. Abstraction thereby imparts the capacity to reason
about anything including, but not limited to, the mental states of
others.
Figure 1. (a) Schematic representation of
activation of portion of (a) less fine-grained memory, left and (b) more
fine-grained memory, right. Each vertex represents a possible memory
location. Each black ring represents an actual location. Ring with circle inside
represents actual location with previously encoded item. Degree of whiteness
indicates degree of activation in current thought, which concerns the need to
kill prey for food.
(2) Cognitive Modernity
The European
archaeological record suggests that a profound cultural transition occurred
between 60,000 and 30,000 ka at the onset of the Upper Paleolithic (Bar-Yosef
1994; Klein 1989a; Mellars 1973, 1989a, 1989b; Soffer 1994; Stringer and Gamble
1993). The Upper Paleolithic
has often been referred to as a “revolution”. Considering it “evidence of the modern human mind at work,” Richard
Leakey (1984:93-94) describes the Upper Palaeolithic as “unlike previous eras, when stasis dominated, ... [with]
change being measured in millennia rather than hundreds of millennia.”
Similarly, Mithen (1996) refers to the Upper Paleaolithic as the
‘big bang’ of human culture, exhibiting more innovation than in the previous
six million years of human evolution. This marks the beginning of a more
organized, strategic style of hunting involving specific animals at specific
sites, elaborate burial sites indicative of ritual, the colonization of
Australia, and replacement of Levallois tool technology by blade cores in the
Near East. In Europe, many forms of art appeared, including naturalistic cave
paintings of animals, decorated tools and pottery, bone and antler tools with engraved
designs, ivory statues of animals and sea shells, and personal decoration such
as beads, pendants, and perforated animal teeth, many of which may have
indicated social status (White 1989a, 1989b). White (1982:176) also writes of a
“total restructuring of social relations.” Clearly the Upper Palaeolithic was a
period of unprecedented cultural change. Was it strictly a cultural explosion,
or a major event in the biological evolution of our species? In either case,
how and why did it happen?
The Upper Palaeolithic as a
Cultural Transition
Although the
tradition has been to view the Upper Palaeolithic transition as a “revolution,”
a more appropriate null hypothesis might well be that it was not a “revolution”
at all, and that Lower and Middle Palaeolithic symbolism should be reassessed
without our modern expectations about iconography (Bednarik 1992). Henshilwood
and Marean (2003) argue that many of the diagnostic traits (such as art, burial
of the dead, personal ornaments, blade technology, complex hearths, and
seasonal hunting in harsh environments) used to identify behavioral modernity
are based on the European Palaeolithic record and lack relevance to African
Stone Age. In fact, models being proposed for the gradual development of
cognitive modernity well before the Upper Palaeolithic transition are
substantially supported by archaeological evidence (Bahn 1991; Harrold 1992;
Henshilwood and Marean 2003; White 1993; White et al. 2003). McBrearty and Brooks (2000), for
example, argue that most of the features associated with a rapid transition to
behavioral modernity, at 40–50 ka in Europe, are actually found in the
African Middle Stone Age tens of thousands of years earlier, including blades
and microliths, bone tools, specialized hunting, long distance trade, art and
decoration. Some important examples include the Berekhat Ram figurine from
Israel (d’Errico and Nowell 2000), and an anthropomorphic figurine of quartzite
from the Middle Ascheulian (ca. 400 ka) site of Tan-tan site in Morocco
(Bednark 2003).
If modern human
behaviors were indeed gradually assembled as early as 250–300 ka, as
McBrearty and Brooks (2000) argue, it would push these changes back into
alignment with the most recent spurt in human brain enlargement, between
600,000 and 150,000 ka (Aiello 1996; Ruff et al. 1997), well before the Upper Paleolithic. Indeed, an earlier cultural
transition might be easier to explain if it coincided with an increase in brain
size (Bickerton 1990; Mithen 1998).
As Henshilwood and Marean (2003:630) point
out, “there is no anatomical evidence (and there may never be any such
evidence) for a highly advantageous neurological change after 50,000 years
ago.” What can be gleaned from skeletal anatomy is that many modern behaviors
were at least anotomically possible by earlier dates. For example, the hyoid
bone (which connects to the larynx) of a Neanderthal from Kebara Cave (63,000
BP) indicates the anatomically capacity for language (Arensburg et. al. 1989),
and the inner-ear structures of Middle Pleistocene humans from the Sierra de
Atapuerca (ca. 800 ka) is indicative of the capacity to hear language properly
(Martinez et al. 2004). Based on skeletal anatomy, we cannot even rule out the
possibility that Homo erectus used some sort of pre-syntactic vocal communication
(Wynn 1998).
From DNA evidence it now seems very
likely, although not indisputable (Eswaran 2002; Wolpoff et al. 2004), that
Neanderthals were a separate lineage and not the ancestors of modern humans
(Caramelli et al. 2003; Krings et al. 1997; Ovchinnikov et al. 2000; Tattersall
1998). If Neanderthals possessed cognitive abilities on par with modern humans,
it would suggest that their abilities evolved independently during their
500,000 years of separate lineage from humans (Mithen 1996:141). Neanderthals
had an average brain size of 1,520 cc (Klein 1989b:272), which is actually
slightly larger than the modern human average. In Europe from 130 ka until at
least 50 ka but possibly 30 ka (Klein 2003), Neanderthals survived glacial
cycles with fluctuations in game populations, climate, and plants. Particularly
in their hunting of large mammals (Marean and Kim 1998), their knowledge of
cave location, hoof prints, animal behavior, and potential carcass locations
was essential to their survival.
The technical intelligence of Neanderthals was
considerable; the Levallois technique of tool making requires 5 stages and
technical thinking throughout the process, such that a fixed set of rules would
be insufficient to do it and even most students today can't learn to make a
Levallois point (Mithen 1996). Neanderthal burials indicate that they at least
occasionally buried their dead, and that the sick and elderly were cared for
(Bahn 1998; Bar-Yosef et al. 1986; Klein 2003; Mithen 1996:135). As for an aesthetic
sense, whether Neandethals were capable of art has become a hotly debated issue
(e.g., Davidson 1992; D’Errico et al. 2003 and associated comments). Bednarik
(1992) compiled a list of published evidence for pre-Upper Palaeolithic
symbolic behavior, including the use of ochre or hematite, crystal prisms and
fossils, perforated portable objects, engraved or notched bone fragments, and
rock art. While some (Davidson 1992; Chase and Dibble 1992) considered this
evidence to be spread too sparsely over time and continents to show any
convincing pattern, certain individual cases beg explanation, with the higher
profile cases including the decorated bone from Bilzingsleben (see Mithen
1996:161), or the musical flute of bone from Divje Babe I cave (D’Errico et al.
1998b).
More recently the
debate has focused on whether Neanderthals are responsible for the
Chatelperronian industry, which appears to be the early Upper Palaeolithic
descendent of the Mousterian industry (Klein 1989b:335). The site of Grotte du
Renne, Arcy-sur-Cure, dated at about 34,000 BP, where a Neanderthal temporal
bone (Hublin et al. 1996) is found near Chatelperronian artifacts, has become
central to the debate over Neanderthal’s cognitive capacity for art and
symbolism. Based on arguments of the archaeological context within the Grotte
du Renne, d'Errico et al. (1998a, 2003) argued that the Chatelperronian ivory
beads, pierced bear incisors and wolf canines, and ivory rings were made by
Neanderthals, and made distinctively enough so as to not be mere imitations of
Aurignacian ornaments made by contemporary modern humans. The Chatelperronian
predates the oldest Aurignacian (both stratigraphically and in 14C)
almost everywhere they are found (d’Errico et al. 2003; Klein 2003) and that
the Chatelperronian lithics show stylistic continuity from the preceding
Neanderthal Mousterian. If their argument is true, and the Neanderthals really
did make simple bone tools, decorate themselves with perforated animal teeth,
and put red ochre on their living floors, then their considerable cognitive
capacities would require a reexamination of the causes of cognitive modernity
(d’Errico et al. 2003; Mellars 1998b).
It has been
hypothesized that modernity arose at different times and places (Bahn 1998;
Mellars 1998b), though this has become exceedingly unlikely on the basis of
recent genetic evidence (Prugnolle et al. 2005). Another problem with this
scenario is the apparently extraordinary coincidence that these Neanderthal
behaviors would have begun just as modern humans were spreading into Europe
(Demars 1998; Hublin 1998; Mellars 1998a; 1998b; Toscano 1998). If Neanderthals
survived in southern Iberia for 5,000 - 10,000 years after the arrival of
anatomically modern humans in northern Spain, it seems likely that they
imitated the Aurignacian objects of the newcomers, possibly with some
(intentional or unintentional) modification (Klein 2003). However, D’Errico et
al. (2003) counter that the Iberian Neanderthals maintained their
traditional culture long after modern humans arrived, indicating they were not
simply acculturated through contact.
Even if we accept
biological ability for “modern” behaviors developed gradually over hundreds of
thousands of years, the question remains about why the development in these
behaviors accelerated at or after 60,000 BP. What is perhaps most impressive about this period is
not the novelty of any particular artifact but that the overall pattern of cultural
change is cumulative; more recent artifacts resemble
older ones but have modifications that enhance their appearance or
functionality. This is referred to as the ratchet effect (Tomasello
1993), and it appears to be uniquely human (Donald 1998). It may have
involved an underlying biological
change, as discussed in below. Note however that many dramatic cultural revolutions,
such as the Holocene transition to agriculture or the modern Industrial
Revolution, occurred long after the biological changes that made them
cognitively possible. Thus all that can be said for certain is that by
somewhere within the vicinity of 50,000 or more years ago, the hominid mind had
not only had acquired the potential for cognitive modernity, but its
environment (social, cultural, and physical) enabled it to capitalize on or
actualize that potential.
The
Upper Paleolithic as an Event in the Biological Evolution of Cognition
Advent of syntactic language in modern humans: While earlier
Homo and even Neanderthals may have been capable of primitive language, the syntactic
aspects appear to have emerged at the start of the Upper Palaeolithic (Aiello
and Dunbar 1993; Bickerton 1990, 1996; Dunbar 1993, 1996). Syntax enabled
language to become general-purpose, put to use in all kinds of situations,
whereas previously it had been reserved for social situations.
Carstairs-McCarthy (1999) presents a modified version of this proposal,
suggesting that although some form of syntax was present in the earliest
languages, most of the later elaboration, including recursive embedding of
syntactic structure, emerged in the Upper Paleolithic. Another proposal is that
at this time humans underwent a transition from a predominantly gestural to
vocal form of communication (Corballis 2002). It is indeed possible that the
syntactic elements of language emerged at this time, and language can transform
cognition (Tomasello 1999). However, we are still left with the question of
what made possible the kind of complex thought processes that sophisticated
language requires. Furthermore, we may never know exactly when syntactic
language began, due the ambiguity of the archaeological evidence. (Bednarik
(1992:30), for example, refer to Davidson and Noble’s (1989) argument on the
cognitive origins of language and iconic graphic art “a house of cards” with no
supporting evidence.)
Connection
of domain-specific modules: The notion that the mind is modular
refers to the view that many cognitive functions are served by innately
channeled domain-specific systems, whose operations are largely independent of and
inaccessible to the rest of the mind (Fodor, 1983). It has been suggested that
what might appear to be unequivocal evidence of modernity might merely reflect
the evolution of cognitive competence restricted to particular domains governed
by particular modules (e.g. Renfrew and Zubrow, 1994). Another proposal
is that modern cognition arose through the connecting of domain-specific
brain modules, enabling cross-domain thinking, and particularly analogies and
metaphors (Gardner, 1983; Rozin, 1976). Mithen (1996) suggests that in the
Upper Paleolithic, modules specialized to cope with domains such as natural
history, technology, and social processes became connected, giving rise to
conceptual fluidity. One problem with this proposal is that although there is
evidence that certain abilities are handled by different modules (e.g.
different brain areas specialized for, say, vision and speech), there is no
evidence that different modules handle different domains of life e.g. no
religion module or tool module. Moreover, the logistics of physically
connecting these modules (whose positions in the brain evolved without
foreknowledge that they should one day become connected) would be formidable.
Sperber’s (1994)
solution is that the modules got connected not directly, but indirectly, by way of a special
module, the ‘module of meta-representation’ or MMR, which contains ‘concepts of
concepts’. Sperber’s proposal is consistent with there being more general
purpose or ‘association cortex’ by the onset of the Upper Palaeolithic,
although the timing of this cultural transition does not coincide with the
increase in cranium size.
Symbolic
Reasoning: Deacon (1997) has suggested that the Upper Paleaolithic
‘revolution’ was due to the emergence of an ability to represent complex,
internally coherent abstract systems of meaning, consisting of representations
and their properties and relationships. Some of these are grounded in concrete
experience, but many are instead processes of systematic abstraction or
symbolic reasoning. Thus Deacon’s account focuses on the ability to
systematically reason with abstract symbols and thereby derive causal
relationships. It does not deal with the intuitive, analogical, associative
processes through which we unearth relationships of correlation.
Cognitive
Fluidity: In contrast, Mithen (1998) proposes that the cultural transition
of the Middle/Upper Paleolithic reflects enhanced cognitive fluidity,
resulting in the ability to map, explore, and transform conceptual spaces.
Mithen refers to Boden’s (1990) definition of a conceptual space as a ‘style of
thinking—in music, sculpture, choreography, chemistry, etc.’ As for why hominids suddenly became good
at transforming conceptual spaces, he is rather vague:
There is unlikely to be one single change in the human mind that
enabled conceptual spaces to become explored and transformed. Although creative
thinking seems to appear suddenly in human evolution, its cognitive basis had a
long evolutionary history during which the three foundations evolved on largely
an independent basis: a theory of mind, a capacity for language, and a complex
material culture. After 50,000 years ago, these came to form the potent
ingredients of a cognitive/social/material mix that did indeed lead to a
creative explosion (Mithen 1998:186).
Although the
capacity for a theory of mind, language, and complex artifacts could
conceivably have arisen at different times, it is hard to imagine how
each could have evolved independently. It is possible they have a common
cause fact; a single, small change within a complex interconnected system can
have enormous consequences (Bak et al. 1988; see also chapter 15 of this volume
by Bentley and Maschner). The possibility that the Upper Paleolithic revolution
was triggered by a small cognitive change is consistent with scientific
understanding of abrupt phase transitions and with the sudden ‘breakthroughs’
that appear in the archeological record back to the Lower Palaeolithic (de
Baune 2004; Tattersall 2003). However, Mithen’s basic point—that it is
related to the capacity to explore and transform conceptual spaces—holds
promise. A similar proposal is that it was due to onset of the capacity to
blend concepts, which greatly facilitated the weaving of experiences into
stories or parables (Fauconnier and Turner 2002). The question we are left with
is: what sort of change in cognitive functioning would enhance the blending of
concepts and exploration of conceptual spaces?
Contextual focus: The above proposals for what kind of cognitive change
could have led to the Upper Paleolithic transition stress different aspects of cognitive modernity.
Acknowledging a possible seed of truth in each of them we begin to converge
toward a common (if more complex) view. Conceptual blending is
characteristic of associative thought, which is quite different from the
logical, analytic thought stressed by Deacon. The modern human mind
excels at both. Hence the Paleolithic transition may reflect a fine-tuning of
the genetics underlying the capacity to subconsciously shift between these
modes, depending on the situation, by varying the specificity of the activated
cognitive receptive field (Gabora 2003). This is referred to as contextual
focus[2]
because it requires the ability to focus or defocus attention in response to
the situation or context. Defocused attention, by diffusely activating a
diversity of memory locations, is conducive to associative thought; obscure
(but potentially relevant) properties of the situation thus come into play
(Figure 2a). Focused attention is conducive to analytic thought because memory
activation is constrained enough to zero-in and specifically operate on the
most defining properties (Figure 2b). Thus in an analytic mode of thought, the
concept ‘giant’ might only activate the specific concept of bigness, whereas in
an associative mode of thought, the giants of various fairytales might come to
mind. Once it was possible to shift between these modes of thought, cognitive
processes requiring either analytic thought (e.g. mathematical derivation),
associative thought (e.g. poetry) or both (e.g. technological
invention) could be carried out more effectively.
Figure 2. (a) Schematic representation of region
of memory activated and retrieved from during (a) associative thought, left and
(b) analytic thought, right. The activation function is flat in associative
thought and spiky in analytic thought. Encoded items in memory locations in
whitened region blend to generate next instant of thought.
When
we take into account how memory works, the lag between the second rapid increase
in brain size approximately 500,000 years ago, and the cognitive transition of
the Upper Paleolithic begins to make sense. A larger brain provided more space for episodes to be
encoded, but it doesn’t follow that this increased space could straightaway be
optimally navigated. There is no reason to expect that information from
different domains would immediately be compatible enough to coexist in a stream
of thought, as in the production of a metaphor. It is reasonable that once the
brain achieved sufficient capacity for modern cognition, it took time to
fine-tune how its components ‘talk’ to each other such that different items
could be blended together and recursively revised
(and recoded) in a coordinated manner. Only then could the full
potential of the large brain be realized. Thus the bottleneck may not have been sufficient
brain size but sufficient sophistication in the use of the memory already available,
which could have come about through onset of contextual focus. With it the modern mind could
both (1) intuitively combine concepts, and adapt old concepts to new contexts,
and (2) logically analyze these new representations and how they fit together.
Together these abilities would lead to the development of more fine-grained
internal model of the world, which through language could be expressed and
revised. Hence it may not be language per se that made the
difference, as Bickerton (1990, 1996) maintained, but rather capacity to shift
between analytic and
associative processing --- such that the fruits of one mode
provide the ingredients for the other --- that not only made language possible,
but other aspects of the cultural life of modern humans such as art, science,
and religion as well.
(3) Minds,
Artifacts, and Evolution
The cumulative nature
of artifact change since the Middle Paleolithic tempts one to refer to culture
as an evolution process.
Like organisms, artifacts become more complex, more finely honed, and more
adapted to the constraints and affordances they impose on one another over
time. They also create niches for one another; for example, the invention of
cars created niches for seatbelts and gas stations. However, artifacts do not
evolve by means of a genetic code, and do not change through a process of
random mutation and natural selection. So culture does not evolve in the same
sense as biological organisms. In this section we examine in what sense the
word evolution applies to artifact change.
Evolutionary
Archaeology
As discussed by Bentley
and Maschner in chapter 10 of this volume, “evolutionary archaeology” (EA) is
one school among an array of evolutionary approaches that attempt to analyze
culture change in terms of concepts borrowed from population genetics such as
selection or drift -- changes in the relative
frequencies of variants through random sampling from a finite population (O’Brien
1996, 2005; O’Brien and Lyman;
for critiques see Boone and Smith, 1998; Gabora, 2006). EA distinguishes itself from other evolutionary
approaches by its strong maintenance that artifacts constitute part of an
organism’s phenotype (defined in biology as the physical manifestation of an
organism’s genotype) and should be subjected to the same kind of analysis as
other phenotypic traits. O’Brien
and Lyman (2004: 179) see human artifacts as phenotypic in the biological
sense, analogous to “a bird’s next, a beaver’s dam, or a chimpanzee’s twig
tools as phenotypic traits.” However, their assumption, that
heritable behavior is the major determinant in the form of a human-made
artifact, is rather easily falsified. Colin Renfrew (1982) succinctly
characterized the difference between adaptations that are accumulated
genetically and adaptations that are passed on culturally:
The genetic inheritance, itself the
product of environmental selection, may itself be regarded as environmental
‘memory’... humans [are not] alone in communicating [their experience of the
environment] to others of the species: the dance of the bees, where individuals
can indicate the direction and distance of suitable supplies of pollen, fulfils
precisely this function. The essence of human culture, however, is that it is
an ‘acquired characteristic’, which, unlike the dance of the bees, is not
genetically determined (Renfrew 1982:18).
As Renfrew points
out, much of human culture is not genetically determined, meaning that it can
evolve in a Lamarckian fashion by inheriting acquired characteristics. Beaver
dams and bird’s nests, however, cannot evolve this way: if a particular
beaver were taught, perhaps by humans, to build a window in its dam, and its
offspring still built normal windowless dams, we would see that only the dam,
and not the window, belongs in the beaver’s biological phenotype, to be passed
on via genetic inheritance.
Do Artifacts Evolve?
Culture has many
attributes of an evolutionary process. That is, phenomena such as transmission
and drift can operate on cultural variants themselves regardless of the
Darwinian (genetic) evolution among humans who carry these variants. In
computer simulations (see Costopolous, chapter 16 of this volume), culture
evolves through drift or a combination of invention and imitation, without
genomes at all (e.g., Gabora 1995; Neiman 1995; Madsen et al. 1999; Bentley et
al. 2004). But although culture has attributes of an evolutionary process, it
does not operate through the same underlying mechanisms as biology. When it
comes to human-made artifacts, inheritance of acquired characteristics is not
just the exception but the rule. Once we learned how to build dwellings with
windows, dwellings with windows were here to stay. Something is happening
through culture that is prohibited in biology.
Some cultural
theorists assume that the basic units of this second evolution process are
mental representations or ideas, or the tangible products that result from them
such as artifacts, language and so forth (Aunger, 2000; Durham, 1991; Lake,
1998). Sometimes these elements of culture are referred to as ‘memes’, a term
that usually implies that they are not only basic elements of culture but also replicators:
entities that make copies of themselves (Dawkins 1976). What does that entail?
The mathematician and computer scientist John von Neumann (1966) postulated
that a replicator, or ‘self-replicating automaton,’ could
be code consisting of (1) a description of itself, or
self-description, and (2) a set of self-assembly instructions.
After it is passively copied from
one replicant, the self-description is actively deciphered via the
self-assembly instructions to build the next replicant. In this case, the code
functions as interpreted information. Interpreting the code makes a body, while the uninterpreted use of the code makes
something that can itself make a body. In biology, the DNA code is
copied—without interpretation—to produce new strands of DNA during
meiosis. In successful gametes these DNA strands are
decoded—interpreted—to synthesize the proteins necessary to
construct a body. However, an artifact (or idea) is
not a replicator because it does not consist of self-assembly instructions. It
may retain structure as it passes from one individual to another. But it
does not replicate it. Like a broadcast signal received by a
radio, an idea has no self-assembly code and needs external apparatus to be
replicated – it cannot self-replicate in the biological sense. Thus the
meme perspective is widely believed to be flawed.
Essentially
assuming that von Neumann’s definition holds for cultural information, Lake
(1998) differentiates between its expression versus its symbolically coded representation.
Speaking aloud or singing, for example, both express what is represented by a
text or written musical score. Singing expresses what can be represented by
written music. However neither expression nor representation is equivalent to
interpretation or (uninterpreted) copying of a self-assembly code. A
musical score does not, on its own, produce little copies of itself. Symbolic
coding is not enough to be a replicator; there must be a coded representation
of the self. In sum then, artifacts are not replicators and not the
basic unit of an evolutionary process.
Mind
as primitive replicator
This does not mean
however that nothing in culture is a replicator. Another
possibility is that the modern mind itself constitutes a replicator. Not a von Neumann replicator, which
replicates with high fidelity using self-assembly instructions as described above, but a primitive replicator
(Gabora 2004), which replicates in an autopoietic sense.An autopoietic structure is one in which the parts
reconstitute one another and thus the structure as a whole is self-mending or
self-replicating. For example, Kauffman
(1993) proposed that the earliest life forms were autopoietic; that is,
that pre-DNA life initially replicated
through a process
in which simple molecules each catalyze the reaction that generates some other
molecule in the set and thus as a whole they self-replicate. The proposal arose
in response to the well-known ‘chicken and egg’ problem: which came first, the
nucleotides that make up a genetic self-assembly code which through
transcription and translation leads to proteins, or the proteins that are
necessary to many stages of the transcription/translation process? His answer
is neither; a sloppy form of self-replication is possible without any code.
Kauffman’s
proposal draws upon the topological notion of a closure space: a set of points sufficiently
connected such that it is possible to get from any one point to another by
following the edges (connections) between them. Closure can be visualized as
follows. Imagine you spill a jar full of buttons on
the floor. You tie two randomly chosen buttons with a thread, and repeat this
again and again. Occasionally you lift a button and see how many connected buttons
get lifted, and you find that clusters start to emerge. When the ratio of
strings to buttons reaches about 0.5, you pass a threshold where, suddenly, a giant cluster of
connected buttons forms, containing most of the buttons. The giant cluster is a
closure space because any two buttons within it are connected through strings
and other buttons. With primitive replicators the
chicken-and-egg problem is solved because self-replication occurs through
happenstance interactions of molecules more primitive than either DNA or
proteins. Since replication proceeds not through following a code but through
happenstance interactions, inheritance of acquired characteristics is
possible, and replication has a low fidelity because of it.
Similarly, it is
proposed that the enculturated modern human mind constitutes a primitive
replicator that emerges through a self-organized process of conceptual closure
(Gabora, 2000;
Gabora and Aerts 2005). Indeed an analogous paradox arises in considerations of
the origin of cultural evolution as arose in consideration of the origin of
biological evolution. We know that a mind is not just a
collection of imitated cultural elements but an integrated model of how
different aspects of experience relate to one another, or worldview. But
this leads to the following chicken-and-egg situation: Until memories are woven into a
worldview, how can they generate the remindings and associations that
constitute a stream of thought? Conversely, until a mind can generate streams
of thought, how does it integrate memories into a worldview? How could
something composed of complex, mutually dependent parts come to be?
Much
as in biology, the chicken-and-egg
paradox can be resolved by applying the concept of
closure. To apply the concept of closure to cognition, episodes in
memory are represented as points (buttons), associative paths between them as
edges (strings), and concepts as clusters of connected points. Retrieval of an
item from memory evokes another retrieval, which, in turn, evokes yet another.
This increases the density of associative paths, and the probability of concept
formation. Concepts facilitate streams of thought, which forge connections
between more distantly related clusters. The ratio of associative paths to
concepts increases until it becomes almost inevitable that a giant cluster
emerges and the episodes form a connected closure space. Eventually for any one
episode or concept there exists a possible associative path to any other, and
together they constitute an integrated conceptual web.
The idea is that,
like the self-organized autocatalytic sets postulated to be the earliest forms
of life, a mind reach a stage in which it is conceptually integrated when it
becomes a primitive replicator. Integrated structure enables it to reason about
one thing in terms of another, adapt ideas to new circumstances, frame new
experiences in terms of previous ones, or combine information from different
domains (as what happens with a joke). It should be stressed that it is not the
presence of but the capacity for an integrated worldview that the
human species came to possess. An infant may be born predisposed toward
conceptual integration, but the process must begin anew in each young mind. The
manner in which a worldview replicates is not all-at-once but piecemeal,
through social exchange, often mediated by artifacts. Worldviews are therefore
not so much replaced by as transformed into (literally) more evolved ones. Like
cutting a fruit at different angles exposes different parts of its interior, different
situations expose different facets of a mind, and the production of artifacts
is one way a mind reveals its current evolutionary state. The process is
emergent rather than dictated by self-assembly instructions, and therefore characteristics acquired over a lifetime are heritable. One
individual modifies the basic idea of a cup by giving it a flat enough bottom
to stay put when not in use, and another individual adds a handle, making it
easier to grasp. With each instantiation, the basic idea remains the same but
the details change to make it more useful or adapted to specific needs.
Thus while brains
were evolving through biological evolution, integrated minds began evolving
through cultural evolution. The associative or relational structure of the mind
manifests as a capacity to define one element in terms of others, predict how a
change to one element will affect another, compare the present state of an idea
or artifact with its previous state, or desired state, and thereby refine or
improve it. Two necessary steps toward conceptual closure would have been (1)
that representations were sufficiently distributed to allow concept formation
and self-cued retrieval, and (2) that contextual focus enabled the capacity to
shift between associative thought (conducive to bridging domains) and
analytical thought (conducive to logical operations within a domain). Thus the
notion of conceptual closure fits well with the explanations put forth to
underlie the two cultural transitions examined earlier, though at present this
is speculative.
Artifacts
and the Extended Mind
In
contradiction to the meme perspective, neither a painting nor the ideas that
went through the artist’s mind while painting it constitute a replicator. Instead, a painting
reveals some aspect of the artist’s mind (which is a primitive
replicator) and thereby affects the minds (other replicators) of those who
admire it. As minds become increasingly complex, the artifacts they
manifest become increasingly complex, which necessitates even more complex
cognitive structure, et cetera. This suggests that artifacts are not the
basic unit of either biological or cultural evolution, but that they a crucial
if indirect role in the evolution of the integrated mind.
As Renfrew (1982)
suggests, artifacts function as external memory storage, which affects both
the biological and cultural fitness of their makers and users (see also Donald
1991, 2001). Retrieving information from the depiction of bison on a cave wall
or calendrical notches in a log is not so different from retrieving knowledge
from memory. Note that elements of the natural world functioned as a form of
memory long before there were symbolic artifacts; a look of disapproval on a
mother’s face could remind a child not to eat a poisonous mushroom as readily
as retrieval of a memory of doing this and getting sick. The look on the
mother’s face is not a material artifact, yet it functions as an external
memory source, in much the same way as notches in a log. This corresponds to
Clark and Chalmers’ (1998) extended mind perspective, in which individual
experience is woven together through interaction between the internal and
external world, and in which the brain and its social cultural environment
co-evolve, mutually provoking change in one another (Deacon, 1997; Durham,
1991; Lumsden and Wilson, 1981).
Conclusions
There are many
ways in which human cognition differs from that of other species, such as our
ability to generate and understand complex languages and other symbolic structures
appearing in art, science, politics, and religion. The appearance of stone
tools (2.5 Ma), strategic big game hunting (1.6 Ma), controlled fire use (0.8
Ma), and complex habitats suggests that prior to the onset of complex language
and symbolism, hominid cognition already differed profoundly from that of other
species. It has been suggested that this reflects onset of the capacity to
imitate, or onset of a theory of mind enabling attribution of mental states to
others. However, since these abilities are also present in other social
species, a more likely suggestion is that it reflects onset of the capacity for
self-triggering of thoughts or motor patterns such that one evokes the next.
This underlies abilities ranging from refinement of skills for tool production
to enactment of events. A plausible explanation for how it came about is that
encephalization enabled mental representations of events and skills to become
more broadly distributed and thus the resulting memory was more fine-grained,
facilitating the retrieval or reminding events that recursively reiterated
constitute a self-triggered thought process.
Many, but not all,
archaeologists believe that these distinctly human abilities likely arose about
fifty thousand years ago, or perhaps somewhat earlier, during the Middle/Upper
Paleolithic. Although encephalization has been occurring throughout the last
two million years, a second spurt occurred between 600,000 and 150,000 ka, well
before the cultural transition of the Middle/Upper Paleolithic. Thus this
second cultural transition cannot be attributed to something so simple as the
sudden appearance of a ‘language module’; a feasible explanation must involve
not new brain parts or increased memory but a more sophisticated way of using the available memory. The advent of
language or symbol use may be part of the answer, but begs the question what
sort of cognitive functioning is capable of producing and using language or
symbols. A more in-depth examination of spatiotemporal
patterns in the archaeological record, however, reveals not just the
pronounced appearance symbolic artifacts, but evidence that they build on one
another in cumulative fashion; that is, exhibit the ratchet effect. Indeed some
believe this to be the most distinctly human characteristic of all. It is
indicative of conceptual fluidity, which involves combining ideas in new ways
and adapting old ideas to new circumstances, and requires both the complex
mental operations characteristic of analytic thought, and the intuitive, analogical
processes characteristic of associative thought. Thus it has been
proposed that culture was brought about by onset of the capacity to adapt
others' ideas to ones' own circumstances, and this requires (1) an integrated
internal model of the world, and (2) a sophisticated way of navigating that
model of the world, such that relationships can be retrieved and creatively
elaborated. This provides a
possible cognitive explanation for the explosion of task-specific decorated
tools, beads, pottery, and so forth during the Middle/Upper Paleolithic: they
reflect onset of the capacity to spontaneously shift between these two forms of
thought depending on the situation. Together, analytical thought allowing
calculation within a domain, and associative thought forging connections
amongst seemingly disparate domains. This paved the way for episodes encoded in
memory to become integrated through the formation of a dynamical network of
concepts to yield a self-modifying internal model of the world.
The last section of
this chapter looked at the relationship between minds, artifacts, and
evolution. Evolutionary archaeologists view artifacts as part of the human
phenotype, which increase biological fitness through their functionality.
However we saw that although there may be a genetic component to the capacity
to produce a well-crafted artifact it is not the only or even dominant
influence; culture appears to play a formidable role. We also saw that
artifacts themselves do not constitute replicators, and are thus not the basic
unit of a cultural evolution process. However it is possible that integrated
worldviews evolve in the same primitive sense as the first living organisms,
through an emergent, self-organized process, resulting in a structure that can
be mathematically described as a closure structure. Because no self-assembly
code is involved, the evolution of such emergent structures is Lamarckian;
acquired characteristics are inherited.
In this brief
chapter it has been possible only to sketch out some ideas about the evolution
of human cognitive abilities. We have a long way to go before we arrive at a
complete picture, but it is an exciting journey ahead.
Acknowledgements
I would like to acknowledgement the support of Foundation for the Future.
I would also like to thank Alex Bentley for many helpful comments and additions, and Merlin Donald
for comments on portions of this chapter.
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