The origins of stone tool reduction and the transition to knapping: An experimental approach

Journal of Archaeological Science: Reports 2 (2015) 51–60

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The origins of stone tool reduction and the transition to knapping: An experimental approach Shelby S. Putt ⁎ Department of Anthropology, 114 Macbride Hall, The University of Iowa, Iowa City, IA 52242, USA

a r t i c l e

i n f o

Article history: Received 28 August 2014 Received in revised form 5 January 2015 Accepted 9 January 2015 Available online 19 January 2015 Keywords: Pre-Oldowan Projectile percussion Bipolar flaking Lithic technology Plio-Pleistocene

a b s t r a c t A reassessment of many of the archaeological assemblages older than two million years has resulted in a general consensus that the earliest Oldowan artifacts were made by skilled toolmakers who had a clear understanding of the fracturing mechanics of different toolstone materials. This has led several researchers to propose a simpler lithic reduction stage that occurred prior to 2.6 Ma. Three lithic reduction techniques that are within the behavioral repertoire of our closest living relatives in the genus Pan are proposed as potential intermediate stages between the percussion behaviors of the last common ancestor of chimpanzees and humans and the skilled knapping of the Oldowan toolmakers. These include direct and indirect projectile percussion and bipolar flaking techniques. Measures of productivity, expediency, and efficiency were obtained and compared between these three reduction techniques and novice freehand knapping in order to better understand some of the factors that influenced how early hominins with little to no understanding of lithic fracturing mechanics achieved sharp flake tools. The provisional results of this proof-of-concept experiment indicate that, of these four conditions, dropping or throwing a large hammer stone on a brittle core is the most efficient way to exploit a core, while bipolar flaking is the most expedient method; however, novice freehand knapping creates the most productive flakes with large, sharp cutting edges. Thus, the transition to knapping in the late Pliocene may have been due to a shifting emphasis on productive toolmaking over expediency or efficiency. © 2015 Elsevier Ltd. All rights reserved.

1. Introduction Since the initial discoveries in the 1970s of Oldowan assemblages that pre-date 2 Ma, such as those from Omo (Chavaillon, 1970, 1976; Merrick, 1976; Merrick et al., 1973) and Gona (Corvinus, 1975; Corvinus and Roche, 1980), archaeologists had argued that late Pliocene stone tools represent the earliest and simplest attempts at lithic reduction by hominins (Leakey, 1971; Wynn, 1981). Over several millennia, this “pre-Oldowan” stage underwent cumulative technological improvements to become the classic Oldowan of the lower Pleistocene (Leakey, 1971). The discovery of technologically sophisticated stone tools from Gona, dated to 2.6–2.5 Ma (Semaw et al., 1997), and reassessments of many of the late Pliocene assemblages (Ludwig and Harris, 1998; Semaw, 2000; de la Torre, 2004; Delagnes and Roche, 2005; Stout et al., 2005; Toth et al., 2006; Braun et al., 2009), however, have led to the realization that the oldest stone tool artifacts demonstrate selectivity of raw materials and technological complexity just as sophisticated as the early Pleistocene Oldowan assemblages. This demonstrable skill exceeds that of modern non-human apes (Toth et al.,

⁎ Department of Anthropology, 114 Macbride Hall, The University of Iowa, Iowa City, IA 52242, USA. Tel.: +1 319 335 0522; fax: +1 319 335 0653. E-mail address: [email protected].

http://dx.doi.org/10.1016/j.jasrep.2015.01.004 2352-409X/© 2015 Elsevier Ltd. All rights reserved.

2006; de la Torre, 2010). The sudden complexity at 2.6 Ma in the archaeological record implies an evolutionary leap, not only in technology, but also in cognition, which defies traditional ideas of Darwinian gradualism. This has led several researchers to propose that hominins had been modifying stone tools prior to 2.6 Ma and that older artifacts will be found that represent a previous technological phase when hominins recognized the benefits of sharp tools but were unaware of the mechanisms of knapping (Semaw et al., 1997; Dennell, 1998; Panger et al., 2002). Panger et al. (2002: 243) argue that “the available direct evidence of tool use in the archaeological record potentially underestimates the origin of hominin tool use by millions of years.” There is indirect, albeit controversial and not conclusive, evidence for modified stone tool use prior to 2.6 Ma: faunal bones dating to 3.4 Ma bear cut marks incised by sharp-edged stone tools (McPherron et al., 2010; but see Domínguez-Rodrigo et al., 2010, 2011). What would this previous technological stage look like? Humans' closest primate relatives provide the best evidence for alternative lithic reduction techniques to freehand knapping that hominins could have employed, which would have required little to no knowledge of conchoidal fracture. Conchoidal fracture produces flakes with a distinct bulb of percussion and concentric ripples, giving them the resemblance of a unionid shell. While it is usually associated with controlled knapping, conchoidal fracture can also occur unintentionally (Cotterell and Kamminga, 1987).

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S.S. Putt / Journal of Archaeological Science: Reports 2 (2015) 51–60

Percussive behaviors using ‘power tools,’ those tools whose functionality requires forceful action (Whiten et al., 2009), are not unique to humans and their ancestors; the Pan clade also exhibits percussive technology behaviors using power tools that are culturally transmitted. For example, in the wild, Pan troglodytes has been witnessed to club prey, potential threats, and competitors with woody materials (Whiten et al., 2009), stab sharp sticks into tree holes to wound prey (Pruetz and Bertolani, 2007), and some groups in West Africa are known to use the anvil-and-hammer technique to crack nuts (Nishida, 1987; McGrew, 1992, 2004; Matsuzawa, 1994; Boesch and Boesch-Aschermann, 2000; Matsuzawa et al., 2001; Biro et al., 2003, 2006). Chimpanzees usually carry out this task by sitting in front of an anvil and striking the nut with a hammer in one or both hands. This nut-cracking behavior has been noted to be very similar and possibly even a precursor to knapping and bipolar flaking percussion (Sugiyama and Koman, 1979; Wynn and McGrew, 1989; Joulian, 1996; Marchant and McGrew, 2005; Wynn et al., 2011). Bipolar flaking involves placing a core atop an anvil and striking it repeatedly in a perpendicular plane, producing two opposing points of impact on either end of the core (Kobayashi, 1975; Barham, 1987; Cotterell and Kamminga, 1987; Jeske and Lurie, 1993; Zaidner, 2013). The common ancestor of chimpanzees and humans likely employed percussive technology similar to that of modern chimpanzees to obtain food items, which could have led to the discovery of the utility of sharp stone flakes. There are currently no recorded cases of chimpanzees making intentional stone flakes in the wild, but several experimental studies have explored the potential knapping behaviors of modern bonobos in captivity (Pan paniscus; Toth et al., 1993; Schick et al., 1999; Roffmann et al., 2012). Kanzi, the first bonobo to be studied, was encouraged to produce flakes by striking a hammer stone held in one hand against the edge of a core held in the other hand. Overall, Kanzi had difficulty producing enough force to consistently produce successful flakes, and he did not seem to grasp the idea of finding acute angles on the edge of the core. Kanzi also discovered on his own that throwing the core against a hard floor (i.e. direct projectile percussion) could produce multiple flakes upon impact, which led him to shift to this technique as his primary method of making flakes over freehand knapping. He also invented the method of throwing one cobble against another on the ground (i.e. indirect projectile percussion), which could effectively create flakes from both stones. These throwing methods allowed him to “impart a much greater impact force between the stones than by hand-held percussion” (Toth et al., 1993: 86). Roffmann et al. (2012) have found that bonobos trained in freehand knapping continue to demonstrate preferences for hammering and aimed throwing techniques over knapping to extract food rewards hidden in wooden logs. Aimed stone throwing has also been observed among wild chimpanzees (Beatty, 1951; Goodall, 1964; Boesch and Boesch, 1990; Whiten et al., 2001; Nishida et al. 2009). Parsimony supports the hypothesis that early hominins probably had similar cognitive and anatomical knapping restrictions to modern Pan (Wynn and Mcgrew, 1989; Tocheri et al., 2008; Wynn et al., 2011). It seems unlikely that hominins would have initially discovered the process of making sharp flakes through freehand knapping and even more unlikely that they would have become such highly skilled knappers rapidly and independently across populations in East and South Africa. In fact, there is currently no evidence for wild chimpanzees smashing a rock or wooden implement against a nut or fruit held in their other hand. Chimpanzees are known to adapt their tools to the level of risk presented by a situation (Humle and Matsuzawa, 2002); therefore, it is likely that they assess the risk of hammering a heavy item into one's own hand to be too high for the potential reward and thus rely on other safer techniques. A more likely scenario for the discovery of lithic reduction involves early hominins, perhaps Australopithecus, discovering that hitting a brittle rock atop an anvil, or the anvil itself, with a hammer stone produces sharp tools useful for foraging activities (Sugiyama and Koman, 1979; Wynn and McGrew, 1989;

Marchant and McGrew, 2005; Wynn et al., 2011). Likewise, the same could have been discovered by throwing a brittle rock directly against an anvil or by throwing a hammer stone at a brittle rock. These behaviors are all within the realm of the last common ancestor's behavioral repertoire and would not require the necessary cognition or skill to understand and initiate purposeful conchoidal fracture. And, as Bril et al. (2012) have pointed out, throwing techniques allow chimpanzees to produce greater kinetic energy upon the point of contact than they would be able to achieve with the knapping gesture. Thus, a hominin with a comparable anatomy to a chimpanzee could in theory produce flakes more efficiently and expediently by throwing than by hammering or knapping techniques. When deciding on how to break a rock to obtain sharp tools, a variety of factors likely played into a hominin's decision-making process, including the productivity or functionality of the tools resulting from the reduction technique, how quickly and easily they could be obtained, how efficient the technique was at preserving raw material and the individual's energy, and the level of risk of each method presented to the toolmaker. To investigate this problem further, a proof-of-concept experiment was devised to compare these factors between four different lithic reduction techniques using medium to large cores (Fig. 1 and Supplementary material): 1) novice freehand knapping, where blows dealt by a hammer stone in the dominant hand are directed towards the edge of a core setting either in the less dominant hand or on the thigh; 2) bipolar flaking, where a hammer stone held uni- or bimanually is used to strike a core setting on top of a stone anvil; 3) direct projectile percussion, where a core is thrown directly at a stone anvil; and 4) indirect projectile percussion, where a hammer stone is thrown at a core setting on a stone anvil. This paper contributes to a broader understanding of the benefits and drawbacks of freehand knapping and alternative hammering and throwing methods that may have been available to hominins during the Plio-Pleistocene. 2. Methods 2.1. Experimental design and procedure The experiment was comprised of four different lithic reduction conditions carried out by novices: freehand knapping, bipolar flaking, direct projectile percussion, and indirect projectile percussion. A total of 40 nodules of Burlington chert, in the form of large to medium chunks and pre-made spalls, were procured for the study. Chert was used as a raw material to make Oldowan tools at times (Kimbel et al., 1996; Kimura, 1997; Goldman-Neuman and Hovers, 2012), though it should be noted that the chert used in this study is local to parts of the Midwestern United States. The average mass of the cores used in each condition was similar (ANOVA, F = 0.734, p = 0.539). Two individuals with no previous experience in flintknapping or breaking rocks (1 male, 1 female) participated in each condition, each person breaking 5 cores per condition. Individuals with no prior experience fracturing stones were included in this study rather than trained or expert individuals because they better approximate the skill level of an early hominin that would have had little experience or knowledge of lithic fracturing mechanics. An a priori power analysis was performed for sample size determination, based on data from a pilot study. With α = 0.05 and power = 0.80, the maximum projected sample size needed for variables measuring expediency and efficiency was 9 cores per experimental condition (Soper, 2014). Therefore, a sample size of 10 rocks per condition should be sufficient to detect a significant effect between the different reduction techniques for variables measuring expediency and efficiency. Due to the restrictions of this study, productivity could not be adequately powered (see Section 2.2 for more information on expediency, efficiency, and productivity). All participants were healthy adults between 22 and 29 years of age. The participants who took part in the bipolar and throwing conditions were different from those in the flintknapping condition because it

S.S. Putt / Journal of Archaeological Science: Reports 2 (2015) 51–60

Fig. 1. The four lithic reduction techniques tested: (a) indirect projectile percussion; (b) direct projectile percussion; (c) knapping; and (d) bipolar reduction.

was important that those participating in the bipolar and throwing techniques have no previous knowledge of stone fracturing mechanics in order to provide a more accurate analog to early hominins that would have had no flintknapping experience. Inter-subject variability was calculated for each measure using Tukey's HSD if there were equal variances and Games–Howell if there were unequal variances. These statistical tests reveal whether any difference exists between two means that is greater than the expected standard error. For every measured variable, the variability between the two subjects in the knapping condition was not significantly different. The level of intersubject variability between the two subjects in the bipolar and throwing techniques was also low overall, except for one of the variables measuring productivity (flake size/mass) and one of the variables measuring efficiency (% core unexploited). With all this said, the sample size of this study is acknowledged as small, and future replicative studies should consider including a larger number of trials and more individuals,

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perhaps even some small, athletic individuals who may better approximate Pliocene hominins. For each lithic reduction technique, the participants wore gloves and safety goggles for their protection and were instructed to work at a comfortable and safe pace with the goal of producing many large, sharp flakes until they could no longer reduce the core any further. The reduction of each core was video recorded with a Sony DCR-SX44 Handycam digital video camera recorder for coding purposes (see Supplementary material), and the remaining debris was bagged after the completion of each core for further analysis. In the novice freehand knapping condition, participants arrived for individual sessions, sat in a chair, and knapped on their thigh or in their hand. They were presented with hammer stones of various sizes, which they selected at different points during the reduction process. The debris created while knapping fell on a large tarpaulin to be collected after the complete reduction of a core. Because of safety concerns, the individuals who participated in the novice knapping condition received instructions prior to the start of the experiment for how to hold the core and how to strike the core so that a flake would run parallel with their hand or thigh. They were also shown a 10-minute-long, silent instruction video that demonstrated simple flake production which exploited much of the core with hard hammer percussion. The knapping participants had less than 90 min of experience when data were collected. In the bipolar and throwing conditions, a granite anvil was placed in shallow sand inside a large box with tall walls to congregate the debitage. One wall of the box was removed so that the toolmaker would have easy access to the anvil. A variety of hammer stones of different sizes were provided for the bipolar flaking and indirect projectile conditions. Both participants preferred to use the same large hammer stone (1400 g) for the duration of both of these conditions. This was probably due to the large size of many of the cores. The weight of this hammer stone is comparable to the 1100 g hammer stone used in the bipolar experiment by Jeske and Lurie (1993). The participants occasionally used the smaller stones as wedges to make the top surface of the anvil level or as stabilizers to keep the anvil in place. The participants received brief, spoken and pantomimed instructions before starting each condition. For the bipolar flaking technique, they were instructed to squat or kneel in front of the core placed on the anvil, to always keep the hammer stone in one or both hands, and strike the core at a perpendicular angle with the hammer stone until they considered the core completely exploited. For the direct projectile condition, they were told to pick up the core and drop or throw it, depending on how much force they deemed necessary to break it, and to repeat this process as many times until they were satisfied that the core was completely exploited. Finally, the participants were instructed to place a core on the anvil for the indirect projectile condition and drop or throw the hammer stone at the core as many times as needed to exploit the core. Participants were instructed to make their own decisions regarding whether a reduction task was completed. While modern humans are not a perfect analog for early hominins in the Pliocene and early Pleistocene, investigations into their toolmaking behaviors could prove to be quite valuable in interpreting the past (Toth and Schick, 1993). The measurements of time obtained from this experiment are most likely not an accurate portrayal of Pliocene hominin toolmaking abilities; however, the patterns that exist when comparing measures of productivity, expediency, and efficiency in a controlled setting among modern humans can help researchers make more informed inferences about earlier hominin species and their motivating factors for choosing a method of lithic reduction. The differences between the knapping and non-knapping conditions may have been even more exaggerated in early hominins because of their anatomical and cognitive knapping restrictions. It should also be noted that only one type of raw material was used in this experiment. Results may vary based on the type of raw material used, and raw material availability may also have affected the types of reduction techniques that were used by hominin toolmakers (Gurtov

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S.S. Putt / Journal of Archaeological Science: Reports 2 (2015) 51–60

Table 1 Descriptive statistics of lithic elements produced during the experiment. Size (cm2)

Reduction technique

Novice freehand knapping Bipolar flaking Indirect projectile percussion Direct projectile percussion

Mass (g)

n

Mean

S.D.

Mean

S.D.

993 1481 1998 1207

3.04 2.60 2.42 2.66

1.3 1.71 0.98 1.23

5.86 4.17 3.51 5.65

15.26 10.85 10.03 15.20

and Eren, 2014). Others are encouraged to replicate this experiment using other materials that would have been available to early hominins, such as quartz, quartzite, and basalt. 2.2. Data collection and analysis Data were collected from the video recordings and lithic debris from each core. Every bag of debitage was gently screened through a 1/4″ mesh, and the remaining pieces were individually labeled. Each piece was weighed to the nearest tenth of a gram and allocated to a metric size category continuum as defined by the smallest of a series of nested squares on centimeter graph paper into which the piece would completely fit (i.e., 1, 2, 3 cm2, etc.; Table 1). The measurements recorded were divided into three categories for easier interpretation of the results. These categories included productivity, expediency, and efficiency (Table 2). Productivity measures the output of usable, functional tools. For the purposes of this paper, only tools that would be useful for cutting tasks were considered to be usable flakes, as there is plentiful evidence for Oldowan tools being used for butchery purposes (Keeley and Toth, 1981; de Heinzelin et al., 1999; Semaw et al., 2003; Sahnouni et al., 2013; Lemorini et al., 2014). Doubtless, many of the flakes, debris, and cores not useful for cutting could have been useful for other activities, such as chopping, hammering, or drilling. To determine the productivity of each lithic reduction technique, a number of attributes were measured, including the total number of usable flakes per core, the number of usable flakes per core mass, cutting edge length (measured with calipers), cutting edge length per flake mass, and the ratio of usable flake size to mass. Following Gurtov and Eren (2014), “usable” flakes were defined for this specific experiment as such: a dimension no smaller than 2 cm2 and at least one edge with an angle no more than 50o, as determined by a goniometer. Flakes smaller than 2 cm2 were excluded from this category because of the difficulty of gripping them, though it should be noted that there are some examples of flakes this small being used as cutting tools during the Pleistocene (Dibble and McPherron, 2006; Zaidner, 2013; Agam et al., in press). Fifty degrees is a common upper threshold for edge angle based on ethnoarchaeological, archaeological, and experimental studies (Gould et al., 1971; Jensen, 1988; Prasciunas, 2007). Because it was not possible to find cores of uniform size and shape, several measurements were divided by the original core's mass to control for this problem (e.g. usable flakes per core mass). Similarly, cutting edge length was divided by its flake's mass (Braun and Harris, 2003). The ratio of size to mass was included to determine which condition is the most successful at producing flakes that are both large and thin (Dibble, 1997).

Expediency measures the ease and time it takes for productivity to occur. The average number of flakes produced per second and the total duration it took to exploit a core divided by the original core's mass were calculated to obtain a measure of expediency. The number of flakes created at each strike was recorded from the video footage. This was usually a conservative number, as debris could fly out of the shot so rapidly that it was at times difficult to observe all the flakes produced. The final series of data collected were meant to evaluate efficiency, which measures the relationship between the effectiveness of raw material exploitation and conservation of energy. Conservation of energy is known to be an important selective pressure in human evolution, where those individuals who use their energy efficiently will have better fitness than those who are inefficient with their energy expenditure (Aiello and Wells, 2002). Raw material exploitation is an indirect measure of energy efficiency because a poorly exploited core may necessitate travel to a quarry locale to acquire additional raw material to process for stone tools. To determine the efficiency of raw material use, the percentages of core mass used to create usable flakes, non-usable flakes and dust, and the unexploited core were calculated. Additionally, energy expenditure was measured more directly by the number of strikes required to reduce each core, made possible by the video footage. From there, the average number of strikes per minute was calculated. A “strike,” while different between reduction techniques, was defined as any increase in velocity initiated by the toolmaker's hand(s) that imparted its energy on another object. This means that misses also counted towards the total number of strikes. The total number of debris elements, as well as usable flakes alone, produced from each core were divided by the core's total number of strikes to demonstrate how many flakes were produced per strike. An analysis of variance (ANOVA) was used to detect significant differences between the novice freehand knapping, bipolar flaking, direct projectile, and indirect projectile group means for any variable with equal variances and a normal distribution, while a non-parametric Kruskal–Wallis one-way analysis of variance was used for variables with a non-normal distribution or unequal variances (α = 0.05). Bonferroni's method was applied as a post-hoc test for pairwise comparisons between individual conditions when equal variances were assumed, while Games–Howell was applied in cases when equal variances could not be assumed. These tests were undertaken using SPSS v. 21. 3. Results 3.1. Productivity Overall, the flakes produced by the novice flintknapping group were the most productive tools (Table 3; Fig. 2). A total of 5855 lithic elements were produced during the course of the experiment, 1742 of which were classified as usable flakes based on the determination factors described in Section 2.2; these numbers include cores, flakes, flake fragments, and shatter that did not pass through a 1/4″ screen. It was discovered that the throwing techniques also conveyed enough force to regularly fracture the anvil, often producing large, sharp flakes, which were also included in the above counts. Excluding the anvil

Table 2 List of measurements recorded for each category. Productivity

Expediency

Efficiency

Total number of usable flakes per core

Number of flakes produced per second

Usable flakes/core mass Maximum cutting edge length Cutting edge length/flake mass Flake size/flake mass

Total time duration to exploit the core/core mass

% core mass into usable flakes % core mass into non-usable elements % core mass into unexploited core Number of strikes per minute Number of strikes/core mass Number of lithic elements produced per strike Number of usable flakes produced per strike

S.S. Putt / Journal of Archaeological Science: Reports 2 (2015) 51–60

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Table 3 Summary statistics of experimental variables examined to measure productivity. NFKa

BF

DPP

IPP

Experimental variable

Mean

S.D.

Mean

S.D.

Mean

S.D.

Mean

S.D.

Prob

Usable flakes per core massb (g) Flake cutting edge length (mm) Cutting edge length per flake mass Ratio of usable flake size to flake mass

0.078 30.22 8.99 1.22

0.018 2.65 2.40 0.26

0.060 24.93 8.05 1.11

0.015 2.97 1.14 0.18

0.055 27.46 7.42 1.00

0.018 3.45 1.93 0.24

0.056 23.98 7.14 0.98

0.016 3.74 2.33 0.28

0.014c 0.001c 0.192 0.117

a b c

NFK = Novice freehand knapping; BF = Bipolar flaking; DPP = Direct projectile percussion; IPP = Indirect projectile percussion. Excludes anvil flakes. Significant at α = 0.05.

flakes, the novice freehand knapping condition produced the largest number of usable flakes (n = 488), accounting for 28% of the usable flakes produced during the experiment, even though they had the least amount of rock mass to break of all the conditions (6066.3 g). Indirect projectile percussion produced 447 usable flakes from 8081.5 g of chert (26%), bipolar flaking produced 413 usable flakes from 6922.1 g of chert (24%), and direct projectile percussion produced the least number of usable flakes, 372, from 7445.3 g of chert (22%). The number of usable flakes the novice freehand knapping condition produced per gram was significantly more than that produced by direct projectile percussion (p = 0.019) and indirect projectile percussion (p = 0.044), but no significant difference was found between knapping and bipolar flaking. While the novice freehand knapping condition produced flakes with a significantly longer average cutting edge than bipolar flaking (p = 0.005) and indirect projectile percussion (p = 0.001), when cutting edge length was divided by flake mass, there was no longer a significant difference between these conditions. Finally, the novice freehand knapping condition produced flakes that were combinatorially the largest and thinnest flakes of any of the other conditions as determined by the ratio of flake size to mass; however, there was no significant difference found between the conditions for this variable.

3.2. Expediency Bipolar flaking, followed closely by indirect projectile percussion, were the most expedient of all the reduction methods (Table 4; Fig. 3). Bipolar flaking consistently and significantly reduced a core in the shortest amount of time of all the conditions. This was determined by the total reduction time for each core divided by its original mass. While indirect projectile percussion produced the largest number of flakes per second, no significant difference exists between the conditions. If expediency was a major deciding factor for which reduction

technique to use for Plio-Pleistocene hominins, these results indicate that freehand knapping may have been an unlikely choice. 3.3. Efficiency The efficiency of raw material use was similar for each reduction technique (Table 5). They all reduced the core into roughly 50% usable flakes (Fig. 4). There were no significant differences between the conditions for the percentage of core left unexploited, usable flakes, or non-usable material. Otherwise, novice freehand knapping consistently performed poorly across all the measures for efficiency. By contrast, indirect projectile percussion was found to be the most energetically efficient condition tested in every measure (Table 5). Novice freehand knapping required significantly more strikes per gram of raw material than any of the other conditions (p b 0.001; Fig. 5). Similarly, freehand knapping required significantly more strikes per minute than any of the other conditions (p b 0.05). Indirect projectile percussion required the least amount of strikes per minute of all the conditions. While there was no statistically significant difference between the throwing conditions for this variable (p = 0.087), there were significantly fewer strikes per minute in the indirect projectile percussion condition than there were in the bipolar flaking condition (p = 0.001). The dichotomy between freehand knapping and indirect projectile percussion continues with the number of lithic elements and usable flakes created per strike (Fig. 6). For every strike, indirect projectile percussion created an average of 5.5 lithic elements, 1.2 of which were usable flakes, while novice flintknapping created an average of 0.81 lithic elements, 0.38 of which were usable flakes. Indirect projectile percussion resulted in significantly more lithic elements per strike than any of the other conditions (p b 0.005), as well as more usable flakes per strike than knapping (p b 0.001). Interestingly, the individuals who participated in the bipolar and throwing conditions both independently discovered that they could

Fig. 2. Comparison of the productivity of the lithic reduction conditions in terms of (a) the mean maximum flake cutting edge length and (b) the mean maximum cutting edge length per flake mass. Error bars represent 95% confidence intervals.

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S.S. Putt / Journal of Archaeological Science: Reports 2 (2015) 51–60

Table 4 Summary statistics of experimental variables examined to measure expediency. NFKa

BF

DPP

IPP

Experimental variable

Mean

S.D.

Mean

S.D.

Mean

S.D.

Mean

S.D.

Prob

Number of flakes per second Reduction time per mass

0.244 0.008

0.076 0.002

0.311 0.005

0.088 0.001

0.237 0.008

0.097 0.003

0.322 0.007

0.131 0.003

0.139 0.016b

a b

NFK = Novice freehand knapping; BF = Bipolar flaking; DPP = Direct projectile percussion; IPP = Indirect projectile percussion. Significant at α = 0.05.

throw multiple core fragments at the anvil at the same time during the direct projectile condition, as well as place several core fragments close together on the anvil to produce more flakes in one strike for both the bipolar flaking and indirect projectile conditions. The experimenter did not suggest these methods to the participants, nor were they discouraged from continuing the behaviors once they discovered them. This serves as an excellent example of how humans will find ways in which to reduce their energy expenditure and expedite a task when possible. 4. Discussion The results of this experiment suggest that freehand knapping, at least when performed by human novices, is not as expedient or energetically efficient as alternative lithic reduction techniques, such as indirect and direct throwing and bipolar flaking methods, which are similar to extractive foraging behaviors seen in chimpanzees in captivity and in the wild. Overall, bipolar flaking was determined to be the most expedient reduction technique, which comes as no surprise, as this is already generally accepted in the literature (e.g. Shott, 1989; Andrefsky, 1994; Villa et al., 2012). What is not commonly considered in the literature, however, is the generally expedient and efficient nature of projectile percussion methods for flake production; in fact, it is only ever mentioned in passing with little or no explanation as to how often it was used at Early Stone Age sites or how to identify it (e.g. de la Torre and Mora, 2010; Stout et al., 2010). In this experiment, indirect projectile percussion was clearly the most efficient reduction method and nearly as expedient as bipolar flaking. One caveat is that during the projectile conditions, the toolmaker bent down to pick up a rock after most throws, which adds to the energy expenditure of the technique; however, the participants in this study often did not add much kinetic energy to their throws but simply dropped the rock. Participants were also asked to rate perceived risk of the four tasks and indicated that freehand knapping posed the most risk of inflicting bodily harm to oneself; however, the small sample size of participants means that these risk assessment data are preliminary. It is very likely that early hominins discovered

that stones could be reduced into sharp flake tools as a result of throwing them against other hard surfaces, or possibly through pounding activities as others have suggested (Joulian, 1996; McGrew, 1992; Wynn and McGrew, 1989), before innovating the controlled freehand knapping gesture. Considering how quickly, efficiently, and innocuously sharp tools could be obtained using these alternative techniques, it is unlikely they would have been rapidly abandoned for a less efficient, lengthier, and potentially more dangerous knapping technique. What evidence is there that hominins were using projectile or pounding techniques to make stone tools prior to 2.6 Ma? In addition to the suggested cut marks made by a sharp-edged stone tool on faunal bones dated to 3.4 Ma (McPherron et al., 2010; but see Domínguez-Rodrigo et al., 2010, 2011), there is also anatomical evidence to support an earlier stage of stone tool modification. The modern features of the human hand are generally viewed as adapted for tool behaviors, especially for the production of stone tools (Marzke and Shackley, 1986; Marzke, 1992; Marzke and Marzke, 2000), but many of these modern features evolved prior to the earliest evidence for modified stone tools. Thus, it is plausible that these derived features could have evolved in response to throwing rather than knapping behaviors (Napier, 1993; Young, 2003). For example, the shorter fingers and longer thumb relative to modern chimpanzees and the expanding apical tufts of Australopithecus afarensis indicate that it had advanced throwing and clubbing grips (Bush et al., 1982; Marzke, 1983, 1992; Young, 2003). Moreover, A. afarensis possessed a suite of features that would have facilitated metacarpal cupping and control of objects with the thumb that indicate an ability to pound and throw objects, but lacked the ability to accommodate large loads across the wrist or thumb necessary for later tool behaviors, such as knapping (Marzke, 2013). Additionally, there is already a well-developed Broca's area evident in the endocast of Homo habilis (Falk, 1983; Tobias, 1987). This area is known to engage in distal motor movements of the hands (Binkofski and Buccino, 2006); thus, an enlargement of this area by 2.5 Ma implies that the ancestors to H. habilis may have already been specializing in motor movements of the hands, most likely related to tool use. One study has demonstrated that the presence of throwing

Fig. 3. Comparison of the expediency of the lithic reduction conditions in terms of the (a) reduction time per core mass and (b) the mean number of flakes produced per second.

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Table 5 Summary statistics of experimental variables examined to measure efficiency. Efficiency type

Efficient use of raw material

Efficient use of energy

a b c

Experimental variable

% core unexploitedb % usable flakesb % otherb Strikes per core mass Strikes per minute Elements produced per strike Usable flakes produced per strike

NFKa

BF

DPP

IPP

Mean

S.D.

Mean

S.D.

Mean

S.D.

Mean

S.D.

Prob

22.11 51.94 25.95 0.21 23.39 0.81 0.38

6.65 13.29 10.12 0.10 5.30 0.27 0.13

14.85 50.37 34.78 0.08 15.81 2.65 0.76

12.79 9.32 18.53 0.02 4.40 0.82 0.24

18.14 53.75 28.11 0.07 12.58 1.25 0.66

12.03 14.79 11.79 0.02 3.31 1.23 0.53

10.43 47.10 42.47 0.05 8.07 5.49 1.23

8.67 12.68 14.93 0.02 1.77 1.82 0.50

0.094 0.687 0.306 b0.001c b0.001c b0.001c b0.001c

NFK = Novice freehand knapping; BF = Bipolar flaking; DPP = Direct projectile percussion; IPP = Indirect projectile percussion. Excludes anvil flakes. Significant at α = 0.05.

skills in captive chimpanzees is correlated with increased cortical connectivity in the homologue of Broca's area and advanced communication skills (Hopkins et al. 2012). Thus, projectile percussion behaviors could have also played a role in the expansion of Broca's area in the hominin brain. Traces of these ancient techniques should also be expected even after the onset of the Oldowan and freehand knapping. In fact, de la Torre and Mora (2010) point out that at several Olduvai sites, such as TK, FLK North I, FC West, and FLK North II, percussive tasks could have been the most significant technical activities, even surpassing knapping. There is evidence for bipolar flaking at the sites of Senga (Harris et al., 1987), Sterkfontein (Kuman, 1998), and Omo (Merrick, 1976; Chavaillon, 1976). Anvils are present for the flaking of large blanks in Acheulian assemblages in the Sahara and East Africa (Alimen, 1963; Chavaillon and Chavaillon, 1981; Jones, 1994; Toth, 2001; Kleindienst and Keller, 1976). Pitted anvils in Oldowan contexts are usually associated with bipolar reduction, but direct or indirect projectile percussion could produce similar types of pitting. For example, Mora and de la Torre (2005) describe severely battered anvils at Olduvai that do not fit the pattern of bipolar reduction, the block-on-block technique, which requires that the core is held in both hands and directly struck against the anvil, nor nut cracking. “Given the major alteration by battering noticeable on many of these anvils, these fractures must have been generated by much stronger processes,” (Mora and de la Torre, 2005:186). Projectile

a

b

c

d

Fig. 4. Comparison of the differential exploitation of the core by (a) novice freehand knapping, (b) bipolar flaking, (c) direct projectile percussion, and (d) indirect projectile percussion.

reduction techniques could potentially explain this pattern of damage on the Olduvai anvils. While the same anvil was used for every condition in this experiment, future studies might consider whether anvil damage patterns vary based on throwing versus bipolar techniques so that Oldowan passive stone tools can be reconsidered in light of new knowledge on projectile reduction. A systematic comparison of projectile percussion products with pounding and knapping products should also be carried out. Nevertheless, hominins eventually began to rely more on freehand knapping rather than other reduction techniques, especially when shaped core tools were the desired products. Even during the Oldowan, when cores were mainly being exploited for sharp flakes (Toth, 1985), however, hominins were knapping. The results of this experiment indicate that, even though freehand knapping was not found to be as expedient or as efficient as the alternative techniques discussed in this experiment, it was a more productive method for creating sharp, usable flakes for cutting tasks, even when produced by novices. Thus, the shift to knapping may reflect a change in diet, dexterity, food source exploitation, social structure, or cognition when forethought and functionality became more important than expediency or energy conservation. It is important to note that this increased productivity is evident even at the beginning stages of learning to knap because this could have provided enough incentive for hominins to increase their knapping skill with more experience, which in turn could have increased the productivity and efficiency of knapping and decreased its level of risk to the toolmaker. Nonaka et al. (2010) found that expert knappers are able to predict the shape of a flake with greater accuracy and use significantly lower kinetic

Fig. 5. The relationship between the amount of time and the number of strikes required to reduce a core for each lithic reduction condition. Best fit lines reveal novice freehand knapping's inefficient use of energy in comparison to the other techniques.

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Fig. 6. Efficient use of energy measured by (a) the mean number of lithic elements produced per strike and (b) the mean number of usable flakes produced per strike. Error bars represent 95% confidence intervals.

energy than novice knappers. Geribàs et al. (2010) also note the ability of expert knappers to better identify ideal angles for percussion and use fewer behavioral units when making flakes in relation to novice knappers. This paper has sought to explore pre-Oldowan lithic reduction possibilities, as it has been suggested that even the oldest examples of knapping in the archaeological record exhibit considerable skill and are unlikely the first attempts at stone tool reduction. Other reduction techniques that were within the behavioral repertoire of the last common ancestor between chimpanzees and humans include bipolar flaking and indirect and direct projectile percussion. None of these methods would have required the cognitive sophistication necessary to understand the mechanics of conchoidal fracture as skilled knapping does, and they would have been possible to execute even with a more primitive hand structure. Indirect projectile percussion, which involves aimed throwing of a hammer stone at a core was found to be the most efficient technique, while bipolar flaking was the most expedient. Thus, this preliminary experiment provides evidence that the transition to knapping may have been the result of a shifting emphasis to productive toolmaking over expediency or efficiency. Acknowledgments I am grateful to those who took the time to participate in this study, to Elizabeth DeForest and Danielle Jones for their assistance in the lab, and to Andriana Vega and Laura DeWald for their involvement in drawing Fig. 1. A special thanks goes to Mark S. Putt and Christina Nicholas for their advice and comments on earlier drafts. References Agam, A., Marder, O., Barkai, R., 2015. Small flake production and lithic recycling at Late Acheulian Revadim, Israel. Quat. Int. 1–15 (in press). Aiello, L.C., Wells, C.K., 2002. Energetics and the evolution of the genus, Homo. Annu. Rev. Anthropol. 31, 323–338. Alimen, M.-H., 1963. Enclumes (percuteurs dormants) associées à l Acheuléen supérieur de l Ougartien. Bull. Soc. Préhist. Fr. LX, 43–47. Andrefsky, W., 1994. The geological occurrence of lithic material and stone tool production strategies. Geoarchaeology 9, 375–391. Barham, L.S., 1987. The bipolar technique in Southern Africa: a replication experiment. S. Afr. Archaeol. Bull. 42, 45–50. Beatty, H., 1951. A note on the behavior of the chimpanzee. J. Mammology 32, 118. Binkofski, F., Buccino, G., 2006. The role of ventral premotor cortex in action execution and action understanding. J. Physiol. Paris 99, 396–405. Biro, D., Inoue-Nakamura, N., Tonooka, R., Yamakoshi, G., Sousa, C., Matsuzawa, T., 2003. Cultural innovation and transmission of tool use in wild chimpanzees: evidence from Welds experiments. Anim. Cogn. 6, 213–223. Biro, D., Sousa, C., Matsuzawa, T., 2006. Ontogeny and Cultural Propagation of Tool Use by Wild Chimpanzees at Bossou, Guinea: Case Studies in Nut-cracking and Leaf Folding. In: Matsuzawa, T., Tomonaga, M., Tanaka, M. (Eds.), Cognitive Development in Chimpanzees. Springer, Tokyo, pp. 476–508.

Boesch, C., Boesch, H., 1990. Tool use and tool making in wild chimpanzees. Folia Primatol. 54, 86–99. Boesch, C., Boesch-Achermann, H., 2000. The chimpanzees of the Taï forest. Behavioural Ecology and Evolution. Oxford University Press, New York. Braun, D., Harris, J., 2003. Technological developments in the Oldowan of Koobi Fora: innovative techniques of artifact analysis. In: Moreno, J., Torcal, R., Sainz, I. (Eds.), Oldowan: Rather More That Smashing Stones. University of Barcelona Press, Barcelona, pp. 117–144. Braun, D.R., Plummer, T., Ferraro, J.V., Ditchfield, P., Bishop, L.C., 2009. Raw material quality and Oldowan hominin toolstone preferences: evidence from Kanjera South, Kenya. J. Archaeol. Sci. 36, 1605–1614. Bril, B., Smaers, J., Steele, J., Rein, R., Nonaka, T., Dietrich, G., Biryukova, E., Hirata, S., Roux, V., 2012. Functional mastery of percussive technology in nut-cracking and stone-flaking actions: experimental comparison and implications for the evolution of the human brain. Philos. Trans. R. Soc. B 367, 59–74. Bush, M.E., Lovejoy, C.O., Johanson, D.C., Coppens, Y., 1982. Hominid carpal, metacarpal and phalangeal bones recovered from the Hadar formation: 1974–77 collections. Am. J. Phys. Anthropol. 57, 651–677. Chavaillon, J., 1970. Découverte d'un niveau oldowayen dans la basse vallée de l'Omo (Ethiopie). Bull. Soc. Préhist. Fr. 67, 7–11. Chavaillon, J., 1976. Evidence for the technical practices of early Pleistocene hominids, Shungura Formation, Lower Omo Valley, Ethiopia. In: Coppens, Y., Howell, F.C., Isaac, G.L., Leakey, R.E.F. (Eds.), Earliest Man and Environments in the Lake Rudolf Basin. University of Chicago Press, Chicago, pp. 565–573. Chavaillon, J., Chavaillon, N., 1981. Galets aménagés et nucleus du Paléolithique Inférieur. In: Roubet, C., Hugot, H.-J., Souville, G. (Eds.), Préhistoire Africaine, Mélanges au Doyen Lionel Balout. ADPF, Paris, pp. 283–292. Corvinus, G.K., 1975. Paleolithic remains at the Hadar in the Afar region. Nature 256, 468–471. Corvinus, G.K., Roche, H., 1980. Prehistoric exploration at Hadar in the Afar (Ethiopia) in 1973, 1974, and 1976. In: Leakey, R.E.F., Ogot, B.A. (Eds.), Proceedings, VIIIth Panafrican Congress of Prehistory and Quaternary Studies. The International Louis Leakey Memorial Institute for African Prehistory, Nairobi, pp. 186–188. Cotterell, B., Kamminga, J., 1987. The formation of flakes. Am. Antiq. 52, 675–708. de Heinzelin, J., Clark, J.D., White, T., Hart, W., Renne, P., WoldeGabriel, G., Beyene, Y., Vrba, E., 1999. Environment and behavior of 2.5-million-year-old Bouri hominids. Science 284, 625–629. de la Torre, I., 2004. Omo revisited: evaluating the technological skills of Pliocene hominids. Curr. Anthropol. 45, 439–465. de la Torre, I., 2010. Insights on the technical competence of the early Oldowan. In: Nowell, A., Davidson, I. (Eds.), Stone Tools and the Evolution of Human Cognition. University Press of Colorado, Boulder, pp. 45–65. de la Torre, I., Mora, R., 2010. A technological analysis of non-flaked stone tools in Olduvai Beds I & II. Stressing the relevance of percussion activities in the African Lower Pleistocene. Paleo 13–34 (Numéro spécial). Delagnes, A., Roche, H., 2005. Late Pliocene hominid knapping skills: the case of Lokalalei 2C, West Turkana, Kenya. J. Hum. Evol. 48, 435–472. Dennell, R.W., 1998. Grasslands, tool making and the hominid colonization of southern Asia: a reconsideration. In: Petraglia, M.D., Korisettar, R. (Eds.), Early Human Behaviour in Global Context. Routledge, London, pp. 280–303. Dibble, H.L., 1997. Platform variability and flake morphology: a comparison of experimental and archaeological data and implications for interpreting prehistoric lithic technological strategies. Lithic Technol. 22, 150–170. Dibble, H.L., McPherron, S.P., 2006. The missing Mousterian. Curr. Anthropol. 47, 777–803. Domínguez-Rodrigo, M., Pickering, T.R., Bunn, H.T., 2010. Configurational approach to identifying the earliest hominin butchers. PNAS 107, 20929–20934. Domínguez-Rodrigo, M., Pickering, T.R., Bunn, H.T., 2011. Reply to McPherron et al.: Doubting Dikika is about data, not paradigms. PNAS 108, E117. Falk, D., 1983. Cerebral cortices of East African early hominids. Science 221, 1072–1074.

S.S. Putt / Journal of Archaeological Science: Reports 2 (2015) 51–60 Geribàs, N., Mosquera, M., Vergès, J.M., 2010. What novice knappers have to learn to become expert stone toolmakers. J. Archaeol. Sci. 37, 2857–2870. Goldman-Neuman, T., Hovers, E., 2012. Raw material selectivity in Late Pliocene Oldowan sites in the Makaamitalu Basin, Hadar, Ethiopia. J. Hum. Evol. 62, 353–366. Goodall, J., 1964. Tool-using and aimed throwing in a community of free-living chimpanzees. Nature 201, 1264–1266. Gould, R.A., Koster, D.A., Sontz, A.H.L., 1971. The lithic assemblage of the Western Desert Aborigines of Australia. Am. Antiq. 36, 149–169. Gurtov, A.N., Eren, M.I., 2014. Lower Paleolithic bipolar reduction and hominin selection of quartz at Olduvai Gorge, Tanzania: What's the connection? Quat. Int. 322–323, 285–291. Harris, J.W.K., Williamson, P., Verniers, J., Tappen, M., Stewart, K., Helgren, D., de Heinzelin, J., Boaz, N., Bellomo, R., 1987. Late Pliocene hominid occupation in Central Africa: the setting, context, and character of the Senga 5A site, Zaire. J. Hum. Evol. 16, 701–728. Hopkins, W.D., Russell, J.L., Schaeffer, J.A., 2012. The neural and cognitive correlates of aimed throwing in chimpanzees: A magnetic resonance image and behavioural study on a unique form of social tool use. Philos. Trans. R. Soc. B 367, 37–47. Humle, T., Matsuzawa, T., 2002. Ant-dipping among the chimpanzees of Bossou, Guinea, and some comparisons with other sites. Am. J. Primatol. 58, 133–148. Jensen, H.J., 1988. Functional analysis of prehistoric flint tools by high-power microscopy: a review of West European research. J. World Prehist. 2, 53–88. Jeske, R.J., Lurie, R., 1993. The archaeological visibility of bipolar technology: an example from the Koster site. Midcont. J. Archaeol. 18, 131–160. Jones, P.R., 1994. Results of experimental work in relation to the stone industries of Olduvai Gorge. In: Leakey, M.D., Roe, D.A. (Eds.), Olduvai Gorge. Volume 5. Excavations in Beds III, IV and the Masek Beds, 1968–1971. Cambridge University Press, Cambridge, pp. 254–298. Joulian, F., 1996. Comparing chimpanzee and early hominid techniques: some contributions to cultural and cognitive questions. In: Mellars, P., Gibson, K. (Eds.), Modelling the Early Human Mind. McDonald Institute Monographs, Cambridge, pp. 173–189. Keeley, L.H., Toth, N., 1981. Microwear polishes on early stone tools from Koobi Fora, Kenya. Nature 293, 464–465. Kimbel, W.H., Walter, R.C., Johanson, D.C., Reed, K.E., Aronson, J.L., Assefa, Z., Marean, C.W., Eck, G.G., Bobe, R., Hovers, E., Rak, Y., Vondra, C., Yemane, T., York, D., Chen, Y., Evensen, N.M., Smith, P.E., 1996. Late Pliocene Homo and Oldowan tools from the Hadar formation (Kada Hadar Member), Ethiopia. J. Hum. Evol. 31, 549–561. Kimura, Y., 1997. The MNK chert factory site: the chert-using strategy by early hominids at Olduvai Gorge, Tanzania. Afr. Study Monogr. 18, 1–28. Kleindienst, M.R., Keller, C.M., 1976. Towards a functional analysis of handaxes and cleavers: the evidence from Eastern Africa. Man 11, 176–187. Kobayashi, H., 1975. The experimental study of bipolar flakes. In: Swanson, E.H. (Ed.), Lithic Technology: Making and Using Stone Tools. Mouton & Co., Chicago, pp. 115–128. Kuman, K., 1998. The earliest South African industries. In: Petraglia, M.D., Korisettar, R. (Eds.), Early Human Behavior in Global Context: Rise and Diversity of the Lower Paleolithic Record. Routledge, London, pp. 151–186. Leakey, M.D., 1971. Olduvai Gorge, Excavations in Beds I and II, 1960–1963. vol. 3. Cambridge University Press, Cambridge. Lemorini, C., Plummer, T.W., Braun, D.R., Crittenden, A.N., Ditchfield, P.W., Bishop, L.C., Hertel, F., Oliver, J.S., Marlowe, F.W., Schoeninger, M.J., Potts, R., 2014. Old stones' song: use-wear experiments and analysis of the Oldowan quartz and quartzite assemblage from Kanjera South (Kenya). J. Hum. Evol. 72, 10–25. Ludwig, B.V., Harris, J.W.K., 1998. Towards a technological reassessment of East African Plio-Pleistocene lithic assemblages. In: Petraglia, M.D., Korisettar, R. (Eds.), Early Human Behavior in Global Context: The Rise and Diversity of the Lower Palaeolithic Record. Routledge, London and New York, pp. 84–107. Marchant, L.F., McGrew, W.C., 2005. Percussive Technology: Chimpanzee Baobab Smashing and the Evolutionary Modelling of Hominin Knapping. In: Roux, V., Bril, B. (Eds.), Stone Knapping: The Necessary Conditions for a Uniquely Hominin Behaviour. McDonald Institute Monographs, Cambridge, pp. 341–350. Marzke, M.W., 1983. Joint functions and grips of the Australopithecus afarensis hand, with special reference to the region of the capitate. J. Hum. Evol. 12, 197–211. Marzke, M.W., 1992. Evolutionary development of the human thumb. In: Manske, P.R. (Ed.), Hand Clinics and Thumb Reconstructions. vol. 8. W.B. Saunders, Philadelphia, pp. 1–8. Marzke, M.W., 2013. Tool making, hand morphology and fossil hominins. Philos. Trans. R. Soc. B 368, 20120414. Marzke, M.W., Marzke, R.F., 2000. Evolution of the human hand: approaches to acquiring, analysing and interpreting the anatomical evidence. J. Anat. 197, 121–140. Marzke, M.W., Shackley, M.S., 1986. Hominid hand use in the Pliocene and Pleistocene: evidence from experimental archaeology and comparative morphology. J. Hum. Evol. 15, 439–460. Matsuzawa, T., 1994. Field experiments on the use of stone tools by chimpanzees in the wild. In: Wrangham, R.W., McGrew, W.C., de Waal, F.B.M., Heltne, P.G. (Eds.), Chimpanzee Cultures. Harvard University Press, Cambridge, pp. 351–370. Matsuzawa, T., Biro, D., Humle, T., Inoue-Nakamura, N., Tonooka, R., Yamakoshi, G., 2001. Emergence of culture in wild chimpanzees: Education by master-apprenticeship. In: Matsuzawa, T. (Ed.), Primate Origins of Human Cognition and Behavior. Springer, Tokyo, pp. 557–574. McGrew, W.C., 1992. Chimpanzee Material Culture: Implications for Human Evolution. Cambridge University Press, Cambridge. McGrew, W.C., 2004. The Cultured Chimpanzee: Reflections on Cultural Primatology. Cambridge University Press, Cambridge.

59

McPherron, S.P., Alemseged, Z., Marean, C.W., Wynn, J.G., Reed, D., Geraads, D., Bobe, R., Béarat, H.A., 2010. Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia. Nature 466, 857–860. Merrick, H.V., 1976. Recent archaeological research in the Plio-Pleistocene deposits of the Lower Omo, Southwestern Ethiopia. In: Isaac, G.L., McCown, E.R. (Eds.), Human Origins: Louis Leakey and the East African Evidence. W.A. Benjamin, Menlo Park, CA, pp. 461–481. Merrick, H.V., Heinzelin, J.D., Haesaers, P., Howell, F.C., 1973. Archaeological occurrences of Early Pleistocene Age from the Shungura Formation, Lower Omo Valley, Ethiopia. Nature 242, 572–575. Mora, R., de la Torre, I., 2005. Percussion tools in Olduvai Beds I and II (Tanzania): implications for early human activities. J. Anthropol. Archaeol. 24, 179–192. Napier, J.R., 1993. Hands. Princeton University Press, Princeton, New Jersey. Nishida, T., 1987. Local traditions and cultural transmission. In: Smuts, B., Cheney, D., Seyfarth, R., Wrangham, R., Struhsaker, T. (Eds.), Primate Societies. University of Chicago Press, Chicago, pp. 462–474. Nishida, T., Matsusaka, T., McGrew, W.C., 2009. Emergence, propagation or disappearance of novel behavioral patterns in the habituated chimpanzees of Mahale: A review. Primates 50, 23–36. Nonaka, T., Bril, B., Rein, R., 2010. How do stone knappers predict and control the outcome of flaking? Implications for understanding early stone tool technology. J. Hum. Evol. 59, 155–167. Panger, M.A., Brooks, A.S., Richmond, B.G., Wood, B., 2002. Older than the Oldowan? Rethinking the emergence of hominin tool use. Evol. Anthropol. 11, 235–245. Prasciunas, M., 2007. Bifacial cores and flake production efficiency: an experimental test of technological assumptions. Am. Antiq. 72, 334–348. Pruetz, J.D., Bertolani, P., 2007. Savanna chimpanzees, Pan troglodytes verus, hunt with tools. Curr. Biol. 17, 1–6. Roffmann, I., Savage-Rumbaugh, S., Rubert-Pugh, E., Ronen, A., Nevo, E., 2012. Stone tool production and utilization by bonobo-chimpanzees (Pan paniscus). PNAS 109, 14500–14503. Sahnouni, M., Rosell, J., van der Made, J., Vergès, J.M., Ollé, A., Kandi, N., Harichane, Z., Derradji, A., Medig, M., 2013. The first evidence of cut marks and usewear traces from the Plio-Pleistocene locality of El-Kherba (Ain Hanech), Algeria: implications for early hominin subsistence activities circa 1.8 Ma. J. Hum. Evol. 64, 137–150. Schick, K.D., Toth, N., Garufi, G., Savage-Rumbaugh, E.S., Rumbaugh, D., Sevcik, R., 1999. Continuing investigations into the stone tool-making and tool-using abilities of a bonobo (Pan paniscus). J. Archaeol. Sci. 26, 821–832. Semaw, S., 2000. The world's oldest stone artefacts from Gona, Ethiopia: their implications for understanding stone technology and patterns of human evolution 2.6–1.5 million years ago. J. Archaeol. Sci. 27, 1197–1214. Semaw, S., Renne, P., Harris, J.W., Feibel, C.S., Bernor, R.L., Fesseha, N., Mowbray, K., 1997. 2.5-million-year-old stone tools from Gona, Ethiopia. Nature 385, 333–336. Semaw, S., Rogers, M.J., Quade, J., Renne, P.R., Butler, R.F., Dominguez-Rodrigo, M., Stout, D., Hart, W.S., Pickering, T., Simpson, S.W., 2003. 2.6-million-year-old stone tools and associated bones from OGS-6 and OGS-7, Gona, Afar, Ethiopia. J. Hum. Evol. 45, 169–177. Shott, M.J., 1989. Bipolar industries: ethnographic evidence and archaeological implications. North Am. Archaeol. 10, 1–24. Soper, D.S., 2014. A-priori sample size calculator for Student's t-tests [Software]. Available from. http://www.danielsoper.com/statcalc. Stout, D., Quade, J., Semaw, S., Rogers, M., Levin, N.E., 2005. Raw material selectivity of the earliest stone toolmakers at Gona, Afar, Ethiopia. J. Hum. Evol. 48, 365–380. Stout, D., Semaw, S., Rogers, M.J., Cauche, D., 2010. Technological variation in the earliest Oldowan from Gona, Afar, Ethiopia. J. Hum. Evol. 58, 474–491. Sugiyama, Y., Koman, J., 1979. Tool-using and -making behavior in wild chimpanzees at Bossou, Guinea. Primates 20, 513–524. Tobias, P.V., 1987. The brain of Homo habilis: a new level of organization in cerebral evolution. J. Hum. Evol. 16, 741–761. Tocheri, M.W., Orr, C.M., Jacofsky, M.C., Marzke, M.W., 2008. The evolutionary history of the hominin hand since the last common ancestor of Pan and Homo. J. Anat. 212, 544–562. Toth, N., 1985. The Oldowan reassessed: a close look at early stone artifacts. J. Archaeol. Sci. 12, 101–120. Toth, N., 2001. Experiments in quarrying large flake blanks at Kalambo Falls. In: Clark, J.D. (Ed.), Kalambo Falls Prehistoric Site, III: The Earlier Cultures: Middle and Earlier Stone Age. Cambridge University Press, Cambridge, pp. 600–604. Toth, N., Schick, K., 1993. Early stone industries and inferences regarding language and cognition. In: Gibson, K.R., Ingold, T. (Eds.), Tools, Language, and Cognition in Human Evolution. Cambridge University Press, Cambridge, pp. 346–362. Toth, N., Schick, K.D., Savage-Rumbaugh, E.S., Sevcik, R.A., Rumbaugh, D.M., 1993. Pan the tool-maker: investigations into the stone tool-making and stone tool-using capabilities of a bonobo (Pan paniscus). J. Archaeol. Sci. 20, 81–91. Toth, N., Schick, K.D., Semaw, S., 2006. A comparative study of the stone tool-making skills of Pan, Australopithecus, and Homo sapiens. In: Toth, N., Schick, K.D. (Eds.), The Oldowan: Case Studies into the Earliest Stone Age. Stone Age Institute Press, Gosport, IN, pp. 155–222. Villa, P., Soriano, S., Tsanova, T., Degano, I., Higham, T.F.G., d'Errico, F., Backwell, L., Lucejko, J.J., Colombini, M.P., Beaumont, P.B., 2012. Border cave and the beginning of the Later Stone Age in South Africa. PNAS 109, 13208–13213. Whiten, A., Goodall, J., McGrew, W.C., Nishida, T., Reynolds, V., Sugiyama, Y., Tutin, C.E.G., Wrangham, R.W., Boesch, C., 2001. Charting cultural variation in chimpanzees. Behaviour 138, 1481–1516. Whiten, A., Schick, K., Toth, N., 2009. The evolution and cultural transmission of percussive technology: integrating evidence from paleoanthropology and primatology. J. Hum. Evol. 57, 420–435.

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Wynn, T., 1981. The intelligence of Oldowan hominids. J. Hum. Evol. 10, 529–541. Wynn, T.G., McGrew, W.C., 1989. An ape's view of the Oldowan. Man 24, 383–398. Wynn, T., Hernandez-Aguilar, R.A., Marchant, L.F., Mcgrew, W.C., 2011. “An ape's view of the Oldowan” revisited. Evol. Anthropol. 20, 181–197.

Young, R.W., 2003. Evolution of the human hand: the role of throwing and clubbing. J. Anat. 202, 165–174. Zaidner, Y., 2013. Adaptive flexibility of Oldowan hominins: secondary uses of flakes at Bizat Ruhama, Israel. PLoS ONE 8, e66851.