Fracture

Fracture refers to a cleavage plane that forms when a brittle material breaks. Most Paleolithic and Neolithic stone tools were shaped by controlled conchoidal fracture. Conchoidal fractures form when compressive loading stress exceeds the tensile and compressive strength of a brittle material (Cotterell and Kamminga Reference Cotterell and Kamminga1987). Conchoidal fractures occur in rocks that are both brittle and isotropic. Isotropy is the quality of responding to load equally in any direction.

Glass is a brittle isotropic material often used to research conchoidal fracture. Much of what we know about the mechanical basis of stone tool production comes from experiments investigating aspects of conchoidal fracture mechanics in glass (for an overview, see Dibble and Rezek Reference Dibble and Rezek2009). Most of the conchoidally fracturing rocks shaped by prehistoric humans were cryptocrystalline silicates, rocks consisting mainly of quartz crystals that are too small to be seen with the naked eye. The most common such rocks used in the Levant were chert and flint, but prehistoric humans also used nonsilicate rocks (limestone and basalt), as well as noncrystalline rocks (obsidian or volcanic glass) and minerals (quartz crystals). Most lithic materials used as hammerstones are tough rocks, such as varieties of basalt, limestone, and quartzite that resist fracture initiation.

Much of the variability in conchoidal fracture arises during the initiation and termination of the fracture (Figure 2.1.a–b). Hertzian initiations begin when compressive force from an indenter creates a cone-like fracture (a “Hertzian cone”) on the surface of the core. This fracture propagates under the side of the core, detaching itself with the resulting flake. Bending initiations occur when the edge of a stone artifact is loaded in such a way that the points of maximum compressive and tensile stresses are separate from one another. When this happens, a fracture can form in an area under tensile stress located some distance from the point where the indenter comes in contact with the objective piece. Shear initiations occur when compressive stress creates a flat planar fracture directly under the indenter. Termination occurs when an expanding flake intersects the surface of the core. Fracture terminations are classified as “feather,” “step,” “hinge,” and “plunging/overshot,” depending on their trajectories and shapes in profile view. Fracture propagation (its length and trajectory) depends on many factors, including the structure of the rock (large versus small crystals, inclusions, and bedding planes) the morphology of the core surface, the amount of load and the rate at which it is applied, and the physical properties of the indenter and the degree to which the rock sample was immobilized during fracture propagation.

Archaeologists employ two main sets of contextual clues when reconstructing the specific patterns of fracture used in prehistory. The first of these involves reconstructing fracture propagation trajectories from the fissures, undulations, and other phenomena left on the fracture surfaces. The second is refitting analysis in which archaeologists reassemble artifacts split by fractures. Complex sets of such “refits” can shed light on the sequence by which a rock was modified by successive fractures.

Abrasion

Abrasion is damage that results from sliding contact between a rock and another surface. This sliding contact creates compressive and bending stresses on the small projections (“asperities”) on the stone surface (Cotterell and Kamminga Reference Cotterell and Kamminga1990: 151–159). As these projections are dislodged, they are dragged across the stone surface, creating pits and scratches (“striations”) that in turn create additional asperities (Figure 2.1c). Abrasion can be accelerated by several methods: (1) by sliding the stone tool surface against harder, coarser materials; (2) by introducing hard, angular grit or sand between the tool and another surface; and (3) by using percussion or some other shaping process to roughen and weaken the surface of the tool. Abrasion processes can be altered by the addition of lubricating agents (e.g., water or oil) so that a smoothed or “polished” surface is created. Such polished edges lose less energy to friction during contact with worked materials, improving their cutting effectiveness. In many parts of the world, the edges of stone tools were (ground) polished to improve their cutting effectiveness.

Flintknapping

Many of the terms archaeologists use to describe stone tool production are borrowed from flintknapping. Historic flintknappers were craftsmen who produced gunflints, but flintknapping now refers to efforts to make and use replicas of prehistoric stone tools (Whittaker Reference Whittaker1994). François Bordes (Reference Bordes1969), Louis Leakey (Reference Leakey1960), Don Crabtree (Reference Crabtree1972), and other twentieth-century archaeologists often described their own flintknapping and tool use experiments and used their impressions of the results to guide archaeological interpretations (Johnson Reference Johnson1978). The most archaeologically important flintknapping terms refer to different methods for initiating fractures (Figure 2.2). Hard-hammer and soft-hammer percussion refer to fracture initiation achieved by striking a core with an indenter made of either stone or metal (“hard-hammer”) or bone, antler, or wood (“soft-hammer”). Pressure flaking refers to fracture initiation by slowly increasing loading with either a hard or soft indenter. Indirect percussion is a technique in which a knapper initiates a fracture by using a punch to focus energy from a hammerstone or some other percussor. Bipolar percussion involves initiating shear fractures by crushing a core between two stones. The anvil technique involves a knapper striking a core against a stationary stone percussor.

Modern-day flintknappers often use thermal alteration (“heat treatment”) to improve the fracture and abrasion properties of a rock. Heating crystalline silicate rocks to 400–500°C and then slowly cooling them causes cracks to form in quartz crystals (Beauchamp and Purdy Reference Beauchamp and Purdy1986, Inizan and Tixier Reference Inizan and Tixier2000). These cracks weaken the rock, reducing the amount of force necessary to initiate and propagate a fracture. When such heat-treated rocks are knapped, fractures that would otherwise have passed around rock crystals instead propagate through them. Consequently, freshly knapped surfaces of heat-treated rocks are more brightly reflective (lustrous) than samples of the same rock that have not been thermally altered. Thermal alteration also usually changes the color of the rock, but this quality varies with rock chemistry. Until recently, thermal treatment was thought to be a recent (i.e., Late Pleistocene or Holocene age) phenomenon, but the practice is now known from later Middle Pleistocene contexts in southern Africa (Brown et al. Reference Brown, Marean, Herries, Jacobs, Tribolo, Braun, Roberts, Meyer and Bernatchez2009).

Basic Terms for Lithic Artifacts

Most stone tools are created by initiating a fracture in a piece of rock by striking it with a hammerstone (Figure 2.3). The pieces of rock detached by conchoidal fracture are called flakes, and the rock from which they are detached is called a core. Archaeologists often use the French term débitage to refer collectively to unretouched flakes and flake fragments. Retouched tools are flakes or other detached pieces whose edges feature contiguous and overlapping clusters of small flake scars (retouch). Flintknappers retouch edges either to change the shape of the edge or to resharpen an edge dulled from use. Many archaeologists use the terms “tools” and “retouched tools” synonymously, even though ethnography and microwear analysis of archaeological specimens all show that people used flakes without retouching them. Some archaeologists also distinguish cores with seemingly use-related retouch and/or wear on some part of their circumference as “core-tools.”

To depict stone tools, lithic analysts have preferred to use line art or drawings instead of photography. This is because many stone tools are either highly reflective or partly translucent. Digital image processing is leading to the increased use of photography, but the overwhelming majority of stone tools are shown in the archaeological literature as line drawings (see Box 2.1).

The major categories of archaeological stone tools are pounded pieces, cores, flakes and flake fragments, retouched tools, or groundstone tools.

Pounded Pieces

Pounded pieces are artifacts shaped by percussion. The damage caused by this percussion is called comminution – multiple overlapping, intersecting, and incompletely propagated fractures. Hammerstones and pitted stones are the most common archaeological pounded pieces. Hammerstones are usually spherical or subspherical and weigh less than 2 kg. Their most distinctive features are convex or flat concentrations of crushing and other damage resulting from their use as indenters against other rocks. Hammerstones used by modern

BOX 2.1 LITHIC ILLUSTRATION

All of the artifact illustrations in this book are redraftings of original artwork from other sources. The literary source and (where possible) original archaeological provenience of each illustrated artifact are indicated in the figure caption. To interpret these drawings, one must understand basic archaeological conventions for drawing and orienting lithic artifacts.

Conventions for drawing lithic artifacts follow most of the principles set forth in Addington (Reference Addington1986) (see Figure 2.4). Cortex-covered surfaces of cores and flakes are indicated by patterns of ink dots called stippling. The edges of fracture scars on core and flake surfaces are indicated by solid lines. These lines begin and end at either the edge of the artifact, another fracture scar outline, or the edge of a cortical surface.

In schematic drawings of cores and flakes, fracture directionality is indicated by placing arrows on the flake scars. Arrows with a circle at the bottom indicate a flake scar that retains the negative impression of a Hertzian cone. Simple arrows indicate that a flake scar lacks a visible point of fracture initiation, but that its propagation trajectory can be inferred from undulations and fissures. Cross-section drawings are indicated in outline and by a solid gray filling. In some cases, a hybrid profile/section drawing on which the working edge is indicated by a thick black line running across the section view is used. Lateral breaks are indicated by sets of short lines at either end of the break and extending away from the drawing in the direction that the complete artifact would have extended. Solid black filling indicates ground and polished surfaces on cores and retouched flakes. Burin removals (see main text) are indicated by arrows pointing to their point of fracture initiation.

This work differs from most conventional drawings of lithic artifacts in that it does not fill flake scars with radial lines. Most formal drawings of cores and flake points use a series of concentric radial lines to indicate the direction of fracture propagation. The convex sides of these lines bulge away from the inferred point of fracture initiation. The extent and spacing of radial lines are also used to convey an impression of shading and three-dimensionality. Radial lines are not used in this book for three reasons. First, scar directionality can usually be indicated when necessary by a single arrow. This follows Edward Tufte's (Reference Tufte1990) guiding principle for scientific illustration: “maximum information, minimum ink.” Secondly, by not cluttering artifact drawings with radial lines, the resulting images are more similar to how lithic artifacts actually appear. Finally, there is so much variability in the ways in which different artists use radial lines, not using them establishes a stylistic consistency for the illustrations in this book.

Stone tools are shown in standardized orientations in drawings and photographs. This allows lithic analysts to use a standard set of terms (i.e., dorsal, ventral, distal, proximal, medial, lateral, etc.) for analogous parts of tools. Unretouched flakes are shown with their striking platform in the proximal position (see main text). Cores are shown with their longest axis usually treated as the distal-proximal axis and the least modified of their surfaces treated as the ventral surface. Retouched tools that still retain remnants of their dorsal and ventral surfaces are oriented the same way as unretouched flakes. Retouched tools that no longer retain evidence of a striking platform are oriented with their longest morphological axis aligned disto-proximally. A few exceptions to these orientations reflect pre-existing archaeological conventions. In the illustrations for this book, the proximal part of the tool is placed in the lowermost (“6 o'clock”) position.

Most artifacts are drawn in at least two views. Minimally, these usually are a plan view of the dorsal face and either a profile (side) view or a cross-section. This is done to give an impression of the artifact's three-dimensional shape. Short lines positioned at either the sides or ends of drawings indicate different views of the same object. Profile/section views are arranged around plan views so that the dorsal face remains closest to the corresponding edge of the plan view (i.e., the “American” convention) (Aprahamian Reference Aprahamian2001). Ventral flake surfaces are rarely illustrated unless they are retouched and unless they differ from the dorsal surface in some significant way. A five- or ten-centimeter scale indicates artifact size. Though drafted at 100% scale, the artifact illustrations for this book had to be reduced for publication. All objects shown in the same figure are at the same scale unless noted otherwise.

The particular artifacts illustrated in this work were selected for their representative value. That is, a conscious effort was made to find objects that were typical for a given artifact-type and for artifacts from a wide range of contexts.

Figure 2.4. Conventions for illustrating flaked stone artifacts.

flintknappers often exhibit one or more discrete patches of comminution. Hammerstones used for repetitive pounding on flat surfaces (as occurs when shaping non-conchoidally fracturing rocks by percussion) often exhibit a ring of comminution running around their circumference. This damage is the result of the hammerstone being rotated axially during use. Pitted stones (also called “anvils”) are usually tabular or plano-convex in cross section. Their most distinctive features are one or more sizeable concavities formed by repeated percussion and the resulting crushing damage.

Higher-Order Groupings of Lithic Artifacts

Higher-order groupings of stone tools consist of a hierarchy of technological and typological characteristics, artifact-types, assemblage-groups/industries, and industrial complexes.

Groups of lithic artifacts that share similar morphological characteristics are called artifact-types. The attributes and variables archaeologists use to define artifact-types are usually divided into technological and typological characteristics. Technological characteristics are those related to choices of techniques and methods used in tool production. For example, the overall size of an artifact, the degree to which it has cortex, and its retouch reflect the choices of the raw material and the extent to which it has been modified. Typological characteristics reflect the imposition of arbitrary shape. Whether the tool is round, square, or triangular in plan view; whether retouch is unifacial or bifacial; and whether there are any patterns in the alignment of scars on the surfaces of the tool reflect choices toolmakers made among a range of functionally equivalent design options. Technological variables are generally thought to reflect differences in human adaptation, whereas typological variables are thought to reflect cultural differences among prehistoric toolmakers. This technology/typology dichotomy, however, is a false one. Technological choices (such as whether to use a particular tool or to retouch it) can reflect cultural differences, and variation in knapping techniques can influence tool morphology.

Lithic assemblages are groups of stone tools found in the same archaeological context. When more than one assemblage share similar inventories of artifact-types, they are often described as assemblage-groups or “industries” (Clarke Reference Clarke1978). Industries from more than one major geographic region that differ typologically but share similar technological characteristics are called “industrial complexes.”

Prehistorians use the term “culture” for lithic assemblage groups very sparingly. It is more common in Epipaleolithic and Neolithic periods when either (1) patterns of lithic typological variation are paralleled in other kinds of archaeological evidence, such as ceramics, architecture, bone tools, or personal adornments; or (2) variation in these other lines of evidence carry greater analytical weight than the lithic evidence. Archaeologists also use the term “tradition” for chronologically sequential assemblage-groups between which they perceive strong typological similarities. The terms “culture” and “tradition” imply that archaeological assemblage-groups correspond closely to social divisions among prehistoric humans. The terms “industry” and “industrial complex” have no such implications; they merely indicate similarities in prehistoric human adaptation related to stone tool technology.

Artifact-types and industries are often given proper names, usually derived from the site at which they were first identified. For example, the terms “Mousterian point” and “Mousterian Industry” are both derived from the French rockshelter, Le Moustier, where examples of Mousterian tools were first identified. Less commonly, the name for an artifact or an assemblage-group may be taken from a region in which the artifact or industry occurs, such as “Nubian core” or “Levantine Mousterian Industry.”

Prehistorians often use type-lists and a variety of technological and typological indices to quantify inter-assemblage lithic variability. Type-lists differ between time periods. Appendix 1 provides type-lists for each of the major prehistoric periods discussed in this book. Most indices of lithic variability are simple ratios of one or more groups of artifact-types divided by some larger number of artifacts in an excavated lithic assemblage. These indices vary from period to period, and there are significant differences among researchers both in how these indices are computed and in how heavily they are weighted in debates about inter-assemblage variability. There are also indices based on metric variation among artifacts, also varying in computation and analytical use.

Ratio-scale measurements increase the quality of archaeological data and improve the kinds of hypotheses about prehistoric behavioral variability one can test with this evidence. Appendix 2 provides a guide to common measurements made on major groups of artifacts.

Raw Material Procurement

In writing about the procurement of lithic raw materials, archaeologists usually distinguish between local materials (those available within a day's walk of a site), and exotic materials available from further afield. Strategies for procuring lithic raw materials are discussed in terms of embedded and direct procurement (Binford Reference Binford1982, Kuhn Reference Kuhn1995). In embedded procurement, small quantities of raw materials are gathered in the course of daily foraging activities. In direct procurement, lithic materials are gathered in bulk from specific sources and transported to sites where they are modified and used. Archaeologists often equate local lithic materials with embedded procurement and exotic lithic materials with direct procurement. Reality can complicate these dichotomies. It is reasonable to assume that transporting lithic materials over great distances increased selective pressure for collecting high-quality materials. Consequently, archaeologists often assume that high-quality rocks represented in small quantities in a lithic assemblage are exotic. Although this might be correct, one needs to be alert to the possibility that they are local materials available only in small quantities. Similarly, embedded and direct procurement do not exhaust the range of strategies humans use to acquire lithic raw materials. Predictable patterns of residential site location and stable social relationships create incentives for more complex trade and exchange patterns, such as emissary trade and down-the-line exchanges. The Neolithic and later phases of Southwest Asian prehistory offer abundant evidence for such complex exchange strategies (Cann, Dixon, and Renfrew Reference Cann, Dixon and Renfrew1969).

In recent literature, archaeologists often draw a distinction between strategies for provisioning places and provisioning people with tools and raw materials (Kuhn Reference Kuhn1993). Provisioning places involves transporting artifacts and lithic materials to habitation sites. The benefits of this strategy are contingent, delayed, and transferable. They accrue with prolonged and recurrent site occupations and persons other than those transporting materials can benefit from them. Provisioning people involves the creation and transport of personal gear. Provisioning people yields immediate benefits, and they are to a limited degree transferable, but they also entail costs, such as designing tools with high potential utility and functionally versatile designs. Archaeologists sometimes link particular types of stone tools to one or another of these strategies, but the actual relationship is almost certainly more complex. In large part, this is because strategic costs and benefits are continuously variable. An artifact that might make an appropriate choice as transported personal gear in one context might be prohibitively costly under a different set of circumstances. For example, while it might make sense to transport a two-kilogram core of high quality rock into a region impoverished in flint, this would be a poor strategic choice for a residential movement into a region where flint is underfoot nearly everywhere. Further complicating matters, traditional archaeological lithic systematics rarely distinguish artifacts on the basis of their size or mass, variables that are clearly germane to assessing their potential utility. Similarly, it is rare to see lithic raw materials described to greater precision than major rock types, such as flint/chert, limestone, basalt, or obsidian. There is, however, tremendous variation within each of these rock types, which affects their suitability for stone tool production.

Tool Production

Stone tools with useful cutting edges can be made in a matter of seconds or carefully knapped over the course of hours or longer periods. Archaeologists use the term “expedient” for the former tool-pro-duction strategy and “curated” for the latter. “Curation” can be confusing because it conflates optimization and intensification (Shott Reference Shott1996). Unnecessarily prolonged effort in tool production is a kind of intensification. Knapping in the service of recovering more potential utility from a given mass of stone is a form of optimization. It can be difficult to distinguish between the effects of intensification and optimization in the lithic record, because one can curate a stone tool by carefully shaping it to improve its functional efficiency, by resharpening it, by modifying it for novel uses, by transporting it, or by some combination of these activities.

In thinking about stone tool production, it is also crucially important to be alert to projecting modern-day habits of thought onto prehistory. For example, proponents of operational chain approaches to lithic analysis often dichotomize stone tool production in terms of façonnage (shaping a core-tool) and débitage (the production of flakes intended for use as tools) (see Inizan et al. Reference Inizan, Reduron-Ballinger, Roche and Tixier1999). No matter how well this dichotomy describes the thought processes of modern-day flintknappers and lithic analysts, it is a false dichotomy. The flakes detached in the course of shaping a core tool remain potentially useful tools (with or without subsequent modification) and the cores produced by flake production retain potentially useful cutting edges and surfaces.

That the stone tools we find are overwhelmingly ones made by adults in the service of their various economic and ecological adaptations is probably another backward projection of a recent (and largely Western) categorical distinction between adult work and child's play (Shea Reference Shea2006a). Children are involved in tool production in many parts of the world today, and even where they are not, children learn many technical skills by imitation. Although it may be possible to differentiate the lithic output of children and other novice knappers in more complex lithic production sequences (Pigeot Reference Pigeot1990), its presence may remain undetectable in simpler aspects of stone tool production.

Similarly, and although it is the case that ethnographic stone tool production is done mainly by men, the notion that prehistoric stone tool production was a gender-specific activity seems improbable (Gero Reference Gero1991). Again, whether or not we can credibly detect gendered structuring of prehistoric lithic variation remains an open question.

Much of the “culture history” of the Stone Age reflects perceived differences in stone tool designs and production techniques. Using these variables to construct quasi-historical entities, such as stone tool industries or archaeological cultures, potentially underestimates prehistoric toolmakers versatility and behavioral variability. Ethnographic stone-tool-makers vary their production techniques widely in response to seasonal differences in demands for tools (Thomson Reference Thomson1939) and other factors, including shifts in their cultural landscape (see Shackley Reference Shackley2000). Many modern-day flintknappers can shift between widely differing modes of stone tool production (Whittaker Reference Whittaker2004). Behavioral variability is a hallmark of hominin adaptation, particularly Homo sapiens adaptation (Potts Reference Potts1998, Shea Reference Shea2011b, Reference Shea2011c). It is only logical to expect that such behavioral variability influenced variation in the archaeological lithic record from the earliest times onward.

Tool Use

When archaeologists speak of stone tool use, or function, they do so at differing levels of specificity. At the most basic level archaeologists often differentiate between “tools” (cores and retouched artifacts) and “waste” (unretouched flakes and flake fragments). Numerous ethnographic studies, however, describe the use of unretouched flakes (Holdaway and Douglas Reference Holdaway and Douglas2012). Experimental studies verify their utility (Crabtree and Davis Reference Crabtree and Davis1968, Jones Reference Jones1980), and microwear analysis report evidence for their use in the past (Keeley Reference Keeley1980). This tool/waste dichotomy projects conventions of industrial-scale mass production back into the Stone Age.

At a further level of specificity, archaeologists speak of stone tool use as involving either extractive activities (food acquisition and other forms of energy capture) or maintenance activities (tool production and repair) (Binford and Binford Reference Binford and Binford1969). They may also write of specialized versus multipurpose tools (Odell Reference Odell1981). These categorical distinctions are also false dichotomies. Butchering an animal can both acquire food (meat and fat) and tool materials (bone, hide, or sinew). A tool designed for one narrow purpose can be co-opted into different purposes as circumstances require. For example, metal arrowheads used by Southwest African hunter-gatherers are also used as drills, knives, chisels, and woodworking tools (Wiessner Reference Wiessner1983).

The expectation of strong form/function correlations among stone tools is a further obstacle to the development of archaeological theory about stone tool use (Odell Reference Odell2001). Many of the names archaeologists have given to specific artifact-types (such as “scraper,” “burin,” “projectile point,” and the like) imply specific and consistent modes of use. This expectation makes sense in terms of present-day tool use. Most archaeologists live in sedentary societies and work in environments bristling with specialized tools. In more mobile ethnographic societies, tool designs place a greater emphasis on portability and functional versatility. Prior to agriculture, all hominin and most human societies likely practiced land-use strategies involving high residential mobility. For this reason, functional variability was likely the rule, and not the exception, for most of prehistory. Among residentially mobile groups, the main factor that constrains functional variability in stone tool use is hafting, which removes portions of tool edge from possible use (Keeley Reference Keeley1982).

Sedentism may have reduced stone tool functional variability (Kelly Reference Kelly1992, Wallace and Shea Reference Wallace and Shea2006). Among sedentary groups, or ones with low residential mobility, fixed residential sites encourage the production of heavy specialized tools, such as seed-grinding equipment, because they are likely to be re-used at those sites. If stable residential sites were provisioned with large quantities of flaked stone, the wide range of stone tools’ available sizes and shapes ought to have encouraged prospective tool users to select artifacts whose sizes, shapes, and edge configurations were better fits for particular tasks – leading to stronger form/function correlations.

Discard/Recycling

Archaeologists have long been aware that reuse and recycling influence lithic variability, particularly with variability among retouched tools and cores (Cahen, Keeley, and Van Noten Reference Cahen, Keeley and Noten1979, Dibble Reference Dibble1995, Frison Reference Frison1969). Nevertheless, there persists in the archaeological literature a kind of “finished artifact fallacy,” an assumption that the forms in which stone tools are preserved in the archaeological record reflect specific designs held in the minds of their makers (Davidson and Noble Reference Davidson and Noble1993). In contrast, re-use, recycling, and allied phenomena affect nearly every dimension of recent human material culture (Schiffer Reference Schiffer1987). All but indestructible stone tools persist on exposed surfaces and in the vicinity of habitation sites, available for use, for more prolonged periods. If anything, one might expect the effects of recycling/reuse to be even more pronounced among stone tools than in other dimensions of material culture.

Social and Cultural Aspects of Lithic Variation

In addition to these more pedestrian aspects of lithic technology, archaeologists have developed interpretive concepts linked to more esoteric aspects of social identity. Because the technological choices recent humans make are conditioned by factors relating to their social context, such as learned patterns of behavior and the social use of symbols, it is reasonable to expect similar factors to be at work in the prehistoric lithic record.

Style is a crucial concept in this regard. In its original formulation, style referred to cultural differences in technological choices, but the concept has since been parsed into iconological and isochrestic styles (Sackett Reference Sackett1982). Iconological style refers to information overtly incorporated into artifact designs for the purpose of broadcasting a specific message. Isochrestic style refers to patterned choices among functionally equivalent designs arising from learned patterns of behavior. They are not intended to actively broadcast a symbolic message, but they can provide clues about cultural similarities and differences among the people making those choices. Stone tools have the potential for both iconological and isochrestic stylistic variability. Conspicuous use of visually distinct exotic raw material might be a plausibly iconological aspect of stylistic variability. Backing the edge of a flake bifacially, as opposed to unifacially, might be a plausibly isochrestic style variant. Hypotheses that one or another stone tool is a stylistic marker of some prehistoric social entity have to be weighed against the simplicity of the technology involved and the improbability that identical patterns of variability could arise independently of one another. These probabilities are intuitively lower in earlier stages of tool production (in raw material choice and tool fabrication), and higher in later stages (in tool use and discard/recycling).

Archaeologists read many things into the lithic record – chronicles of evolutionary progress, landscapes of cultural variation, and patterns of behavioral variability. At its core, however, the lithic record reflects variation in the habits of stone tool production and use. Archaeological lithic analysis seeks to reconstruct those habits and to explain their variability.

Table 2.1. Essential Concepts in Fracture Mechanics, Flintknapping, and Lithic Analysis

Table 2.2. A Simplified Core Taxonomy (After Conard et al Reference Conard, Soressi, Parkington, Wurz and Yates2004, 14, Table 1)

Figure 2.1. Conchoidal fracture initiation (top) and termination (middle), and abrasion mechanics (bottom).

Figure 2.2. Knapping techniques.

Figure 2.3. Knapping basics: flake production (top), retouch (bottom).

Figure 2.5. Core landmarks.

Figure 2.6. Working edges of major core types (inclined, parallel, platform) viewed in cross-section.

Figure 2.7. Flake landmarks.

Figure 2.8. Major flake types. a. non-cortical flake, b. cortical flake, c. core-trimming flake-lateral, d. core-trimming flake-distal, e. core-trimming flake-medial, f. blade, g–h. prismatic blades.

Figure 2.9. Retouch types.

Figure 2.10. Retouched tool types and problematical pieces. a. scraper, b. truncation, c. backed knife, d. awl/perforator, e. point, f. limace, g. foliate point, h. notch, i. denticulate, j. burin, k. core-on-flake, l. “Janus”/Kombewa flake, m. ad hoc hammerstone on flake, n. “scaled piece,” o. “utilized” flake.