Platform

150 Lithic Technology, volume 22, no. 2

PLATFORM VARIABILITY AND FLAKE MORPHOLOGY:A COMPARISON OF EXPERIMENTA L AND

ARCHAEOLOGICAL DATA ANDIMPLICATIONS FOR INTERPRETING

PREHISTORIC LITHIC TECHNOLOGICAL STRATEGIES

Harold L. Dibble

INTRODUCTION

At the heart of research on prehistoric lithicassemblages are two fundamental questions. First,what were the processes by which prehistoricflintknappers produced their implements? Andsecond, why did they produce the forms they did?In the current literature a great deal of attentionis paid to the factors that govern the design ofvarious retouched types (e.g., Binford 1980;Torrence 1983, 1989: Bamforth 1986: Bleed1986; Bousman 1993; Andrefsky 1994; Kuhn1994), their production (e.g., Sollberger 1977:Flenniken 1978; Bradley and Sampson 1986;Whittaker 1994: Shott 1996). and their mainte-nance (e.g., Gallagher 1977: Hayden 1977, 1979:Dibble 1984, 1987, 1995b; Barton 1988, 1990,1991; Neeley and Barton 1994). Increasingly,however, attention is being paid to the technologyof blank production: in fact, many believe thatthis is the most potentially informative avenue ofresearch (e.g., Tixier et al. 1980; Inizan et al.1992; Sellet 1993).

Most technological studies, whether based onarchaeological materials (e.g., Collins 1975: Marksand Volkman 1983; Volkman 1983: Sullivan andRozen 1985: Baumler 1988: Cziesla et al. 1990) orreplicative (flintknapping) experiments (e.g.,Crabtree 1966; Bordes and Crabtree 1969; New-comer 1971; Mauldin and Amick 1989: Ohnuma1995). have focused on core reduction sequences.While these frequently tend to be heavily descrip-

. tive, i.e., simply documenting variability in reduc-tion patterns (e.g., Boda 1994; Delagnes 1995),there is also a concern for explaining technological

variability in terms of its adaptive significance,whether relating it to raw material variability(Bietti and Grimaldi 1995; Dibble et al. 1995).overall intensity of utilization (Baumler 1988:Dibble 1995b). or other factors (e.g., Munday1979: Marks 1983; Henry 1989, 1995; Shea1995). The focus of this article is on the relation-ship between certain platform variables and flakemorphology, drawing on data from actual prehis-toric flake assemblages and controlled experi-mental studies.

While it is undeniable that core reductionsequences represent a significant aspect of lithic _technological variability, the attention paid themhas resulted in a shift away from even morefundamental processes of flaking. Some of theearliest works on physical properties of flakedstone were those of Goodman ( 1944) and Bourdier(1963), while Kerkhof and Mller-Beck (1969)were the first to discuss concepts of Hertzianfracture and its application to stone tools. Soonafter there was a virtual explosion of interest infracture mechanics, with the works of Speth(1972,1974), Faulkner (1972). Bonnichsen (1977).Cotterell and Kamminga (1979,1986,1990),Cotterell et al. (1985), Tsirk (1974, 1979). andBertouille ( 1989). However, the direct applicationof these results to archaeological materials hasnot yet enjoyed a great deal of success. There havealso been controlled experiments designed not tofocus on fracture mechanics, but to documentrelationships between particular independentvariables controlled by the flintknapper and other,dependentvariables that are observable on flakes.While many relationships have been found (Speth

Harold L. Dibble, Department of Anthropology, University of Pennsylvania. Philadelphia, PA 19104 I

Dibble - Platform Variability and Flake Morphology 151

1975, 198 1; Dibble and Whittaker 198 1; Pelcin1986; Dibble and Pelcin 1995; ), this approachhas not, in general, had a great impact on lithicstudies, either.

One of the major problems in such experimentsis that the experimental designs have not allowedfor the production of very realistic-looking flakes.For example, in a series of experiments performedby the present author (Dibble and Whittaker198 1: Dibble and Pelcin 1995), flakes were re-moved along the sides of plate-glass cores. Theflakes themselves more closely resembled burinspalls than normal archaeological flakes or blades,and platform width and flake width were alwaysconstant, equaling the thickness of the plateglass. The design of the cores and the nature of theflakes produced from them, plus the fact that somany variables were held constant, resulted invery artificial products that bore little resem-blance to most archaeological lithic materials.Moreover, it is a fact that many variables --platform morphology, core morphology, variousaspects of the delivery of force when striking thecore, and the flaking qualities of the raw materialitself -- interact during the production of a flake.Many of these are invisible when analyzing reallithic artifacts. Legitimate questions can there-fore be raised regarding the applicability of theseresults to archaeological materials. What is clearlyneeded -- and this is the purpose of the presentpaper -- is to demonstrate that the relationshipswhich became apparent in these controlled ex-periments hold true for archaeological materialsand, moreover, that they represent a significantaspect of prehistoric technological variability.

This article deals primarily with the relation-ship between certain platform variables -- plat-form thickness, platform width, and exteriorplatform angle -- and flake morphology. A num-ber of interesting findings come from the studiespresented below. First, it is shown that theseplatform variables have a tremendous effect onflake size and morphology, in spite of the fact thatso many other potential factors are uncontrollablein dealing with archaeological samples. Thus,platform variation and its effects on flake mor-phology are fully applicable to archaeological in-vestigation. Second, these platform variables areunder the direct control of the flintknapper andpresumably are intentionally varied to achieveparticular results. By focusing on these variableswhen analyzing prehistoric assemblages, we can

add a new dimension to reconstructions of lithictechnology that goes beyond core reduction pat-terns based on the sequencing and direction offlake removals. Third, it is likely that some of thealternative ways of preparing platform morphol-ogy have effects that are both interpretable andexplainable in terms of current models of techno-logical efficiency, resource economy, and mobil-ity. Thus, attention to platform variation may con-tribute to an overall understanding of technologi-cal variability in terms of prehistoric adaptations.

MATERIALS AND METHODS

Two primary sources of data, derived from bothexperiments and archaeological samples, are pre-sented here. Data from controlled experimentsare drawn from a previously published study(Dibble and Pelcin 1995) designed to assess thesignificance of harnmer mass and velocity on flakemass. This sample contains a total of 177 com-plete flakes, produced from half-inch plate glasscores; the flakes were removed along one edge bydropping steel ball bearings on an adjacent edge.The two adjacent edges (one representing theplatform surface and the other the exterior sur-face of the core) were cut so as to produce exteriorplatform angles of 55, 65, and 75 degrees. Angleof blow was held constant, but different sized ballbearings were dropped from varying heights.

The archaeological data used in this paperrepresent many different industries and technolo-gies. Chronologically they include the Lower,Middle, and Upper Paleolithic: geographically theyrepresent Africa, the Near East, and Europe; andtechnologically they express varying emphases onLevallois, flake, biface, and blade production (seeTable 1). Only complete, unretouched flakes areused in this analysis and in all cases the total flakepopulation above 3 cm in maximum dimensionfrom a given assemblage was studied. While thetotal sample size is high (over 12,000 completeflakes), the data sets are not completely compa-rable: they were collected over a period of morethan fifteen years in several different studies, andfor some of them not all of the variables of interesthere were recorded. Thus sample sizes for anyparticular analysis vary considerably. In addi-tion, sample sizes for extreme values, when bro-ken down by other variables, tend to get smallquickly. In the analyses presented here, samplesizes of less than 5 cases were eliminated.


For all of this material, including the experi-mental flakes, measurements were taken in aconsistent manner even though the actual record-ing was done by several different individuals.Length is the distance from the point of percus-sion to the most distal point on the flake. Widthis taken perpendicular to and at the midpoint ofthe length axis: thickness, at the point where thelength and width axes cross. Platform width is themeasurement along the platform from one lateraledge to the other. Platform thickness is measuredfrom the interior to the exterior surface of theplatform at the point of percussion. It representsneither maximum platform thickness nor theshortest distance from the point of percussion tothe exterior surface. Bulb length was taken on theinterior surface from the point of percussion to thebase of the bulb. All measurements are expressedin mm.

Exterior platform angle, or the angle betweenthe platform surface and exterior surface, is mea-sured with a goniometer directly behind the plat-form, and expressed in degrees. On flakes withcurved exterior surfaces, the measurement of thisangle can vary depending on the point on theexterior surface at which the measure was taken.For the sake of consistency, the angle used wasthat formed by two lines -- one represented by theplatform thickness, the other extending down theexterior face directly in line with the axis ofpercussion to a distance equal to the platformthickness. Weight was variously taken to thenearest 1 or 2 grams, depending on the precisionof the scales being used. For the experimentalflakes, platform width and flake width are con-stant (one-half inch) and only three values ofexterior platform angles are represented.

A very conservative approach was taken withregard to all of these measurements: if landmarkswere unclear, or if it looked as though a portionwere missing, then the measurement was re-corded as missing. Such problems were mostapparent for the platform measurements, exteriorplatform angle, and bulb length. The measure-ment of exterior platform angle is especially diffi-cult if the platform surface was markedly curvedin the interior-exterior plane just behind the pointof percussion or if the exterior surface of the flakewas too irregular. Again, such cases were omittedfrom consideration. On two separate occasionsthe level of inter-observer reliability on this mea-sure was checked and the results found to be

satisfactory. Both the definitions of these observa-tions and the general conservatism in their re-cording should be kept in mind when verifyingthese results with independent data.

Throughout this paper two words -- effect andassociation -- are used seemingly interchangeablyto describe relationships amongvariables, but it isimportant to recognize the difference in theirmeanings. When the word effect is used, as inthe effect of platform thickness on flake weight, itis because it is believed that there is a trueindependent-dependent, i.e., causal, relationshipbetween the two variables. Association, on theother hand, means that two variables co-vary, butnot necessarily because changes in one directlycause changes in the other. Many of the analysesthat follow are based on showing relationshipsbetween variables. By themselves, these relation-ships do not demonstrate causal relationships,but only associations. In flintknapping, however,many clear independent-dependent relationshipsdo exist, given that the knapper can change suchfactors as how the blow is delivered or the mor-phology of the core surface before the flake isstruck. If other relevant variables are held con-stant, and increases in platform thickness arecorrelated with increases in flake weight, for ex-ample, then it is clear that the relation is causal:platform thickness was determined prior to theformation of the flake and, because other poten-tial variables were not factors in producing vari-ability in weight, platform thickness is left as thesole independent variable. Admittedly, when deal-ing with archaeological assemblages there are agreat number of potentially relevant variables thatcannot be controlled, so it is difficult to assume acausal relationship between any two variables.This is why controlled experiments, in whichmany variables are held constant, are necessary,and it is one more reason why a comparisonbetween experimentally-derived results and thosebased on archaeological materials is crucial. None-theless, there are still many instances in which ademonstrated relationship cannot be assumed tobe causal.

Although there is a great deal of variation in thekinds of assemblages represented here, the flakes,both experimental and archaeological, representprimarily hard-hammer direct percussion tech-niques in which the hammer struck a platformsurface. No claim is made that the relationshipsfound here are directly applicable to other tech-

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niques, such as bifacial thinning, bipolar, pres-sure flaking, etc.

One final clarification is needed to facilitateinterpretation of the analyses that follow. Invirtually every example except Figure 1, the indi-vidual data points shown on the graphs do notrepresent individual cases, but rather averagevalues of the Y-axis variable for all of the caseswithin a given interval of the X-axisvariable. Thusthe probability statistics given in the figure leg-ends are based on Analysis of Variance of thedifferences among the means and not correlationsbased on individual flakes. This approach wastaken because individual variability, especially inthe archaeological data, is quite high; in fact, thereis often so much individual variability that it tendsto obscure real relationships. This variability is aresult of two things. First, it is a fact that manyvariables contribute to flake morphology. If weare interested in examining just the relationshipbetween platform thickness and flake weight, forexample, it is impossible to choose flakes that areconstant in every other measure. Thus individualflake variability is high because of the varyingeffects of those other variables, but the use ofaverages can help to isolate significant trends.The second source of variability is measurementerror, a result of either the difficulty of takingcertain measurements or of problems in oper-ationalizing certain attributes. An example of thesecond problem is platform area, which is theproduct of platform thickness and platform width.This is a fine measure if the platform surface isrectangular in shape, but it will vary from the truearea if the platform surface is round, triangular, orvirtually any other shape. To the extent that theseare random and not systematic errors, individualvariability may be high, but the average values willaccurately represent the central tendency.

RESULTS

Various controlled experiments have demon-strated that two aspects of flake platforms --platform thickness and exterior platform angle --have significant effects on flake size (Speth 1972,1974, 1981; Dibble and Whittaker 1981; Dibbleand Pelcin 1995). This has been shown (Dibbleand Pelcin 1995) by plotting flake weight againstplatform thickness for three different exteriorplatform angles (see Figure 1). For each value ofexterior platform angle, increasing the platform

thickness resulted in heavier flakes. Likewise, theslope of the relationship between platform thick-ness and weight differed among the three values ofexterior platform angle, such that higher exteriorplatform angles resulted in increasingly heavyflakes for the same value of platform thickness.

Another way of presenting these relationships,in the format that will be used throughout theremainder of this paper, is shown in Figures 2 and3. In Figure 2, for example, the average weights ofthe experimental flakes with various platformthicknesses are plotted and it is clear that in-creased platform thickness results in larger flakes.In Figure 3, the relationship between exteriorplatform angle and weight is shown broken downby different values of platform thickness. Withineach interval, increasing the exterior platformangle results in larger flakes. Note that the largestaverage flake weights result from high values ofboth platform thickness and exterior platformangle. In the archaeological sample, increases inplatform thickness have a similar effect on flakeweight, as shown in Figure 4.

Although the effect of platform width on flakeweight was not addressed in the experiment be-cause of the design of the cores, it is possible toexamine this relationship with the archaeologicalsample. As can be seen in Figure 5, platform widthexpresses a similar association with flake weight.However, the relationship shown here is possiblymisleading: since platform thickness tends to behighly correlated with platform width, it could bethat the platform width-to-weight relationship isreally only a reflection of the relationship betweenplatform thickness and weight. In order to deter-mine the effect of platform width alone, Figure 6displays the average weights of flakes by intervalsof platform width within particular intervals ofplatform thickness. In this way it can be seen that,for a particular interval of platform thickness,increases in platform width result in larger flakes.Given, then, that both platform thickness andplatform width directly affect flake size, it shouldbe no surprise that platform area (the product ofplatform thickness and platform width) also showsa clear relationship with weight (Figure 7). Sinceplatform area reflects the combined influence ofboth platform thickness and platform width, all ofthe remaining analyses of archaeologicbe based on it.

al data will

To demonstrate the effects of exterior platform


angle on weight, it is necessary to control for thecompeting effects of platform area. Again, theclearest way to do this is to plot exterior platformangle against weight by particular intervals ofplatform area, which allows us to hold platformarea relatively constant and thereby isolate theeffects of exterior platform angle alone. When thisis done (Figure 8) the effects of exterior platformangle on weight, for particular platform areas, areclear and follow patterns similar to those seen inthe experimental data (refer to Figure 3).

Since exterior platform angle and platform areaeach have a direct relationship with overall weight,it would be expected that increasing either or bothof these platform variables would also increaseflake dimensions, i.e., length, width and thick-ness. This is generally the case in both the experi-mental (Figure 9) and archaeological (Figure 10)data. In comparing these two figures, bear inmind that the experimental cores had a constantplatform width, so that on these cores platformarea is directly and linearly related to platformthickness (in other words, doubling the platformthickness doubles the platform area). Thus theplatform thickness of the experimental flakes isdirectly comparable to the platform areas usedwith the archaeological data. Likewise, the widthsof the experimental flakes was also constant, sotheir surface areas are directly reflected by lengthalone.

Platform morphology alone is thus a significantfactor affecting flake size, whether size is ex-pressed in terms of weight or dimensions. Obvi-ously, flake weight is a direct function of the threedimensions, but the importance of separatingthese two aspects of size (weight versus dimen-sions) will be addressed in more depth later in thepaper. For now, it is clear that a flintknapper hastwo options for increasing overall flake size: pre-pare either higher exterior platform angles orbigger platform areas. While these are not mutu-ally exclusive options over a range of differentflake sizes, to produce a flake of a given size thereis the possibility of having a high platform areaand low exterior platform angle, or conversely, alow platform area and high exterior platform angle.Thus, using weight as a reflection of size, when welook at the data for any single weight, these twovariables should be inversely related to eachother. As shown in Figure 11, this is the case forboth the experimental (uppergraph) and archaeo-logical (lower graph) data. Thus, adjusting plat-

form area or exterior platform angle representstwo alternatives open to the flintknapper.

It should be clear that, in every case in whichdirect comparisons can be made, the archaeologi-cal data show the same relationships betweenplatform morphology and flake size that are seenwith flakes produced under controlled experi-ments. This is important for a couple of reasons.First, it helps to validate the results obtained fromsuch experiments. In spite of their artificialconditions, they are useful for isolating and objec-tifying relationships that are relevant to archaeo-logical materials. Some of these relationships aredifficult to observe in normal flintknapping simplybecause so many variables are operating simulta-neously. Second, looking at it from the oppositepoint of view, the successful extension of theexperimental results strongly suggests that a largenumber of potentially significant independentvariables (hammer type, angle of blow, etc.), whichwere controlled in the experimental situation,exert only minor, if any, effects on these relation-ships (see also Pelcin 1996).

Other factors can be examined in the archaeo-logical data to see what effects they may have, ifany. Three types of comparisons that reflectaspects of overall core reduction technologies arepresented here: scar morphology, technologicalcategory, and industry. In Paleolithic research(e.g., Dibble and Bar-Yosef 1995) attention iscurrently focused on these kinds of variables asrepresenting a major source of inter-assemblagevariability. Thus it is important to see whether ornot different core reduction technologies affect therelationships under investigation here.

In order to save space, the comparisons pre-sented here are based on only two of the relation-ships shown above: platform area-to-flake weight,and exterior platform angle to the ratio of surfacearea to platform area. The first (Figure 12) is theeffect that scar morphology has on these relation-ships, which appears to be minimal. The second(Figure 13) examines the role that basic technol-ogy plays, as recorded on flakes that are clearlydiagnostic of one or another of three major tech-nological categories -- Levallois, blade, and nor-mal (or non-diagnostic). Admittedly, these tech-nological classes are very superficial and probablyencompass a tremendous amount of variability.Nonetheless, they all show the same general rela-tionships.

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The third comparison (Figure 14) is brokendown by industry. Here the number of potentialfactors that may affect the relationships in ques-tion is quite high. Raw material is one of the moreimportant of these. While most of these industriesare made on local flint, the Nubian Khormusanpeople utilized ferracrete sandstone, while theflints used at the other sites also differed in termsof size and abundance. However, good data on theraw materials used in these assemblages are notavailable in a way that could be systematicallyincorporated into the present analysis. There arealso clear technological differences among theseindustries, which result in different core mor-phologies. The Khormusan, Levantine Moust-erian, and Biache are all considered Levalloisindustries, though the specific reduction sequencesvary considerably (cf. Boda 1988: Meignen andBar-Yosef 1988, 1991, 1992; Dibble 1995a; Sellet1995). The Levantine Upper Paleolithic sample iscomposed of both Ahmarian and LevantineAurignacian, which have varying emphases onblade production. Level F4 from Pech de 1Az isMousterian of Acheulian tradition and includessome biface manufacture, while Combe-Capellehas relatively little Levallois production and nobifaces. Although the various industries aresomewhat separate from each other, which pre-sumably reflects the effects of these uncontrolledvariables, the basic relationships are still appar-ent within any one of the assemblages.

What these figures suggest is that, while corereduction technologies differ among Paleolithicassemblages, they do so independently of thekinds of relationships examined here. Thus plat-form morphology and its effects on flake morphol-ogy represent a completely separate dimension oflithic technology and flake assemblage variability.

technological importance for the production offlakes. The aspects of the platform that wereaddressed here (platform thickness, platformwidth, and exterior platform angle) are all underthe direct control of the flintknapper, and they aretrue independent variables in that they directlyaffect flake morphology. This is not to say thatthey represent the only factors affecting flakemorphology, and they are certainly not the onlyimportant factors giving rise to lithic assemblagevariability. But they do have major effects andundoubtedly reflect strategies employed by theflinknapper to produce different results. Theyrepresent aspects of lithic technology that arerelevant to behavior and should not be ignored inreconstructing prehistoric technologies.

It should be emphasized again that these re-sults have relevance only for flakes produced bydirect percussion on a platform surface. Theextent to which they are applicable to flakesproduced by pressure is not known, though it islikely that the relationships would remain essen-tially the same. The results obtained from othertechniques, such as bifacial flaking (in which theexterior edge of the platform is struck) or bipolarflaking, are probably not directly comparable. Italso bears repeating that, as clear as these rela-tionships are, there is a great deal of variabilityamong individual flakes. It is quite easy to findlarge flakes with small platforms and small flakeswith large platforms. Many factors interact incomplex ways to give rise to flake morphology andresults are not always completely predictable. Onthe other hand, even with only a moderate amountof experience, a flintknapper can achieve a signifi-cant degree of control over flake variability. Byisolating the contribution that platform morphol-ogy makes on flake variability, our understandingof different flaking strategies is enhanced, even ifthat contribution is less than 100 percent.

DISCUSSION AND CONCLUSIONSBeyond the demonstration of the relationships

between platform morphology and flake morphol-ogy, what is interesting is that prehistoric knappersadopted different strategies with respect to howthey set up platform morphology. For example,among the assemblages included here, there is ahigh degree of variability in terms of platform areaand exterior platform angle (Figure 15). Someassemblages -- for example, the Levantine Mous-

Platform area alone has been utilized for sometime as a means to control for original flake size inassessing the degree of reduction that took placeon a flake tool from retouching (Dibble 1987,1995b). The results presented here support suchan approach, though they also suggest that exte-rior platform angle should be taken into accountas well, in assessing flake size. The implicationsof these results go beyond attempts to reconstructor control for original flake dimensions. Theysuggest that platform characteristics are of major

terian from the site of D40 -- seem to maximizeboth exterior platform angle and platform area.Others appear to minimize platform area but


exhibit relatively high exterior platform angles, orvice versa. Although the choice of adopting onestrategy over another may simply reflect differenttechnological traditions, it may also be related toa number of other factors.

As shown above, increasing either platformarea or exterior platform angle increases overallflake size. Industries that have, on average, highvalues for both probably reflect an attempt tomaximize the size of the resulting blanks. Thismay reflect conditions in which raw material waslarge and plentiful. But differences also resultfrom increasing platform area, on the one hand,and exterior platform angle, on the other.. Thesemay reflect different flintknapping strategies thatmay also be related to either raw material or otherconsiderations.

The choice of one or the other of these ap-proaches is related to differences in flake mor-phology, especially with respect to flake dimen-sions relative to platform size. If flakes are madebigger by increasing the size of their platforms,then there is a general decrease in flake dimen-sions relative to platform size (Figures 16 and 17).Adjusting the exterior platform angle shows theopposite association: flake dimensions in relationto platform size increase with higher exteriorplatform angles. For the archaeological sampleonly the ratio representing flake area to platformarea is shown, but there is a similar effect for bothlength and width individually. Thus, increasingthe exterior platform angle results in larger flakesrelative to their platform areas.

This difference, which is illustrated schemati-cally in Figure 18, has a couple of importantimplications. First, there is a consideration of coremaintenance. By producing larger flakes withlarger platforms, more of the edge is removed asthe striking platform for a given flake area. If theexterior platform angles are increased instead,then the striking platform of a core is conservedlonger, thereby extending the usefulness of thecore in relation to the size of the flakes taken fromit.

Second, platform area represents, for mostpurposes, wasted material on a flake blank: itprovides no cutting edge, and is rarely retouched,and its overall size may constrain hafting. Fur-thermore, it can be shown in the archaeologicaldata that bulb length is also associated with

platform area (Figure 19), though it is likely thatplatform width contributes more than platformthickness to bulb length. Given that the bulb isitself a function of platform size and it, too, repre-sents a less desirable portion of the total flakeweight, it would not always be advantageous fora flintknapper to follow a strategy of increasingflake size by increasing platform size. By produc-ing flakes with higher exterior platform angles,however, s/he can increase flake dimensions whilesimultaneously holding down the size of both theplatform and bulb. This would help maintain corestriking platforms and, at themore efficient flake blanks.

same time, produce

On the other hand, employing higher exteriorplatform angles has disadvantages. As shown bySpeth (1981) and Dibble and Pelcin (1995), therange of both force and angle of blow that willproduce a flake is considerably less with higherexterior platform angles than with lower ones.Therefore, it is generally easier to produce flakeswith lower exterior platform angles. If raw mate-rial is abundant, then core maintenance may notbe a significant consideration and smaller exteriorplatform angles may be employed. If it is scarce,then increasing flake exterior platform angleswould help both to economize cores and to pro-duce more efficient flake blanks, though the de-gree of control necessary in flaking is increased.With these considerations in mind, it is interest-ing to note that both D40 and Combe-Capelle areprimary exploitation sites in the immediate vicin-ity of raw material (Munday 1976; Marks, per-sonal communication; Dibble and Lenoir 1995).and both are among those sites with the highestplatform areas. There may also be considerationsinvolved with the maintenance of high platformangles through faceting or other methods of coreplatform rejuvenation.

Certain aspects of platform variability de-scribed here also have implications for recentdiscussions of flake size and group mobility, inwhich it has been argued (Kuhn 1994, 1996; cf.Morrow 1996), based fundamentally on surfacearea to weight ratios, that smaller flakes are moreefficient in terms of transport costs. It is true thatallometry alone would predict that smaller flakeshave greater surface area to weight, since surfacearea increases as the square, while weight in-creases as the cube. If all dimensions increaseequally, then larger flakes, even though they couldsustain more resharpening because of their abso-

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lute size and thus have higher potential use-lives,would necessarily have smaller surface area toweight ratios and thus would represent less effi-cient objects for transport. It has been repeatedlydemonstrated, however, that larger blanks wereconsistently selected for tools and transportedduring the Paleolithic, at least (Geneste 1985;Dibble 1988, 1995a, Dibble and Holdaway 1993;Meignen 1993; Dibble et al. 1995;). If larger flakesare less efficient, then why are they consistentlythe ones being selected and transported?

Assuming that flakes will be reduced until theyreach some minimum size (Dibble 1995b, Kuhn1994), larger flakes do have an advantage in thata smaller proportion of their overall size is simplywaste. As pointed out by Kuhn (1996), however,the real issue is not overall size, but shape: forflakes with the same weight, thinner flakes withlarger surface areas are more efficient (in terms ofresharpening potential) than thicker flakes thathave less surface area. Such a change overcomesthe predicted allometric relationship, and thusrepresents a possible technological strategy thatcould be advantageous under certain circum-stances. In fact, it has been shown at Combe-Capelle (Roth et al. n.d.) that transported flakes(those imported into the site) do exhibit highersurface area to weight ratios than those that weremanufactured from immediately available mate-rial and left behind. So it seems likely that at leastsome Paleolithic peoples recognized the advan-tage of such flakes when they selected them fortransport.

The archaeological data presented here alsosuggest that knappers influence such differencesin flake shape by changing their platform mor-phology. In these data, varying ratios of platformwidth to platform thickness are associated withdifferent ratios of flake surface area to thickness.When both exterior platform angle and platformarea are controlled, the ratio of platform width toplatform thickness does not have a significantassociation with overall flake weight (Figure 20,upper graph). However, producing larger plat-form widths relative to platform thicknesses clearlychanges the distribution of weight, expressed byflakes with increasingly higher ratios of surfacearea to thickness (Figure 20, lower graph). Thus,one way to increase a flakes surface area tothickness, and therefore make it more efficient,would be to increase platform width relative toplatform thickness. Moreover, even when we look

at assemblage averages (Figure 2 l), the relation-ship between platform width to thickness andflake surface area to thickness is clear. Thedistribution shown here may indicate that some ofthese industries were intentionally providing moreefficient flakes for transport.

These are just two examples to show thatunderstanding platform morphology and its ef-fects on flake morphology may relate to an overallunderstanding of the adaptive significance of lithictechnological variability. Further research isneeded in this area, and it would be premature toclaim that flake platform variability is more impor-tant than other aspects of lithic technology. Onthe other hand, it cannot be denied that it repre-sents a significant factor, and one with potentialfor interpreting assemblages in terms of pastbehavior and adaptation. What must be kept inmind is that platform variability reflects actionsthat a flintknapper takes prior to the removal of asingle flake, presumably to achieve certain de-sired effects. Understanding what those effectsare should help in recognizing particular strate-gies employed by prehistoric flintknappers.

Knowing the effects ofvarious platform charac-teristics on flake morphology, however, is onlyone aspect of the problem. There is also a need tounderstand and recognize different options forcontrolling them. There are probably many differ-ent ways to change platform angles, for example;and likewise, platform shape can vary as a resultof many different actions. Moreover, there is anobvious need to understand more of the effects ofcore surface morphology on flake variation, espe-cially lateral and longitudinal convexity. This ismore than just a question of scar patterns, sincesimilar core morphologies can be produced indifferent ways. .

As stated at the beginning of this paper, pat-terns of core reduction sequences represent animportant aspect of lithic technology, and theidentification of particular reduction patterns is ajustifiable goal in lithic research. It is hoped,however, that a case has been made here thatunderstanding even more fundamental aspects offlintknapping also can provide insights into howand why lithic assemblages vary. By adding thisdimension to our analytical arsenal, our under-standing of prehistoric lithic technologies willimprove.


ACKNOWLEDGMENTS

For access to collections I would like to thankArthur Jelinek, Anthony Marks, Denise deSonneville-Bordes, Alain Tuffreau, and the JerseyMuseum: for help in data collection, and forvarious discussions about flake variability, thanksgo to Joshua Beeman, Philip Chase, SimonHoldaway, Shannon McPherron, April Nowell,Andrew Pelcin, Barbara Roth, Helen Sanders-Grey, and reviewers of this manuscript; for fund-ing I thank the National Science Foundation (Grant#s BNS 8804379 and DBS 92-20828), the De-partment of Anthropology, Research Foundation,the University Museum of the University of Penn-sylvania, and private donors.

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Figures on pages 163 - 170

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