Early hominid hunting, butchering, and carcass-processing behaviors: Approaches to the fossil record

JOURNAL

OF ANTHROPOLOGICAL

ARCHAEOLOGY

2, 57-98 (1983)

Early Hominid Hunting, Butchering, and CarcassProcessing Behaviors: Approaches to the Fossil Record PATSHIPMAN

AND JENNIE

ROSE

Department of Cell Biology and Anatomy, The Johns Hopkins Universiiy School of Medicine, 725 North Wolfe Street, Baltimore, Maryland 21205 Received October 12, 1982 A major aim of paleoanthropology is to learn what ancient behaviors were related to the acquisition, processing, and consumption of meat and when these behaviors arose. For this reason, studies focusing on purported early hominid hunting and butchery sites are important if rigorous criteria for recognizing such sites are used. Different criteria currently used as evidence of hominid involvement with ancient bones are reviewed and it is concluded that the presence of cutmarks, verified by scanning electron microscope (SEM) inspection, is the most reliable. Successful application of this criterion depends upon a thorough knowledge of the normal variations in microscopic morphology of different types of marks that are found on bones. Therefore, variations in microscopic and gross morphology within and among a large sample of known stone tool cutmarks, carnivore tooth scratches, and rodent gnawing marks are documented. The effects of sedimentary abrasion, as caused by fluvial transport of bones, are also presented. Guidelines are presented for using microscopic criteria to identify unknown marks on fossils and possible applications of this approach are discussed. Further, it is suggested that evidence of hominid carcass-processing activities can be placed into one of three ranked categories of certainty according to the type of data used. Explicitly stating the category and type of evidence used to deduce hominid activities, and by extension to defme site types (i.e., butchery, kill, base camp), may improve the clarity of hypotheses about and interpretations of early hominid behaviors.

INTRODUCTION

The origins and early practices of hunting and butchering by hominids are of central importance in paleoanthropology. From evidence of and ideas about these topics, a wealth of controversial theories have arisen. These have ranged from Dart’s interpretation of the intrinsically aggressive nature of man (Dart 1959, 1957; popularized by Ardrey 1976, 1961), to theories about the basal hominid diet (Jolly 1970; Szalay 1975; Walker 1981, 1980; Washburn and Lancaster 1968), to hypotheses about the impact of such behaviors on social organization and the development of the hominid complex (Holloway 1967; Isaac 1978; Lovejoy 1981; Washburn 57 0278-4165183 $3.00 Copy&.ht @ 1983 by Academic Press, Inc. All rights of rrpmduction in my fom reserved.

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1960). A closely related problem, that of establishing whether or not preClovis sites in North America contain butchered animal remains and therefore attest to the early peopling of North America (Bonnichsen 1979, 1973; Bryan 1978; C. V. Haynes 1974, 1971; G. Haynes 1981; MacNeish 1978; Morlan 1980; Stanford 1979), has recently received much attention as well. A major problem with assessing early hominid hunting and butchering practices lies in the difficulty of recognizing sites where these activities have occurred. Virtually all explicit and implicit criteria for recognizing such sites include the co-occurrence of stone tools and bones. Clark and Haynes (1970:407-408) summarize the features of purported Paleolithic butchery sites into five categories: (1) . . semi-articulated skeletons with minimal evidence of disturbance. . . . (2) Partly broken up skeletons of a single animal with only a small degree of bone dispersal and . . comparatively few stone artifacts. . . . (3) Extensive disarticulation and dispersal of the bones of one, sometimes more than one, large animal . with a comparatively small number of stone artifacts. . (4) Multiple kill or “occupation” sites . . . considerable quantities of large cutting, heavy duty and light duty tools and waste [are present] . . bones are broken up and dispersed. . . . (5) “Occupation” sites with numerous . . . tools . . . but very little bone.

As Clark and Haynes observe, these criteria are usually inexplicit and are certainly likely to lump natural deaths or predators’ kills with hominid sites. Leakey (1971:258) is one of the few who offer an explicit definition of butchery sites: “artefacts are associated with the skeleton of a large mammal or with a group of smaller mammals.” Isaac (1978, 1977, 1976) and Howell (1966) largely adhere to this definition, although Isaac and Harris (1975) suggest that the density of stones and bones needs to exceed that of normal background scatter. Klein (1975), in discussing why Swartklip I is probably not a butchery site, adds two more criteria: (1) the number of carnivore individuals is low in butchery sites as compared with carnivore accumulations; and (2) the larger ungulates are better represented by cranial, rather than postcranial, remains at butchery sites. Binford (1981) echoes this point in suggesting that the less useful body parts are likely to be left at the butchery site. Although these criteria would seem to add up to a workable definition (see also Wendorf and Hester 1962), they can only be applied to sites at which it can be demonstrated that there is a causal, functional association of stone tools with bones rather than an accidental one. Bonnichsen (1979, 1973), Dart (1959, 1957, 1949), Morlan (1980, 1978), Stanford (1979), and others raise an additional problem: how can butchery sites be recognized if there are few or no stone tools? Dart’s analysis of breakage patterns, skeletal representation, and fauna1 representation

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proved inconclusive in the light of more recent knowledge of carnivore accumulations (e.g., Brain 1981, 1976, 1970; Shipman and Phillips-Conroy 1977). Bonnichsen (1979) relies on the presence and frequency of spiral fractures and flaking to distinguish hominid-broken bones, but both types of damage do occur in other types of assemblages (see Binford 1981; Morlan 1980; Myers et al. 1980; Shipman and Phillips-Conroy 1977). Morlan (1980) suggests that, if point loading can be shown to have occurred, green bone fractures of adult proboscidean bones are indicative of hominid breakage; this hypothesis remains to be tested. Stanford (1979: 108) explicitly suggests four criteria: (1) (2) (3) (4)

the the the the

presence presence presence presence

of of of of

apparent “expediency tools” made of bone; flaked bones; bone apparently processed for the removal of marrow; stone artifacts.

He further suggests that tiny step fractures, polish, and striations on the proximal end of spiral fractures will distinguish bone expediency tools. However, both Mot-Ian’s and Stanford’s criteria remain controversial at present. APPROACHES

TO THE PROBLEM

It is generally agreed that the resolution of such problems will come from an improved knowledge of the characteristic effects of nonhominid causes of bone damage so that these can be identified, isolated, and removed from further concern, save for the paleoecological and taphonomic information they yield (Binford 1981; Gifford 1981; Schiffer 1978; Shipman 1981a). In short, if we are to recognize early hominid butchery patterns and related behaviors with certainty, we must be able to eliminate mimics caused by nonhominids that obscure the information on these behaviors preserved in the fossil or archaeological record. To this end, a wide range of studies of modem taphonomic and site formation events has been carried out. For example, Brain (1980, 1976, 1974, 1970), Binford and Bertram (1977), G. Haynes (1982, 1981, 1980), Hill (1980, 1975), Miller (1975, 1%9), Mills and Mills (1978, 1977), Shipman (1981b; Shipman and Phillips-Conroy 1977), Sutcliffe (1970), and others have examined the effects of carnivore damage on bones. Behrensmeyer (1978; Behrensmeyer et al. 1979; Behrensmeyer and Dechant-Boaz 1980), Gifford (1978, 1977), Toots (1965), Myers et al. (1980), and others have studied the attrition of modern bone assemblages on land surfaces due to weathering, trampling, and microorganisms. The hydraulic transport of bones has been examined by a variety of workers (Behrensmeyer 1975, 1973; Boaz and Behrensmeyer 1976; Hanson 1980; Shipman et al. 1981b;

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Voorhies 1969). Butchery practices of recent peoples and replicative butchery experiments have also been investigated (e.g., Aguirre and Biberson 1965; Binford 1981, 1978; Bonnichsen 1979, 1973; Bunn 1983a; Crader 1983, 1974; Frison 1978; Gifford 1977; Guilday et al. 1962; Jones 1980; Stanford et al. 1981). For the most part, such studies have explicitly or implicitly aimed at developing criteria to identify the agent responsible for the accumulation of or damage to an assemblage. These studies have yielded an impressive body of data on the frequencies of various types of damage or breaks, the survival rates of different skeletal elements, and the proportions of various prey species collected under different circumstances. As a result of such studies, several older interpretations of early hominid sites have been challenged and new interpretations offered (e.g., Binford 1977, contra Isaac 1977; Binford 1981, contra Leakey 1971; Binford and Bet-tram 1977, contra Dart 1957; Brain 1981, 1967, contra Dart 1957; Klein 1975, contra Dart 1957; Potts 1982, contra Leakey 1971; Shipman et al. 1981c and Shipman 1982, contra Leakey 1968). These challenges have often taken the form of documented resemblances between the fossil assemblage and those formed by hydraulic forces or carnivores. However, since many fossil assemblages have been exposed to multiple agents of damage, these resemblances are not entirely satisfactory evidence for identifying the predominant agent of damage or accumulation. Taphonomic overprinting may confuse or obscure many of the diagnostic features or signatures of the various events that have shaped an assemblage. In other cases, new support for previously published interpretations has been offered (e.g., Bunn 1981 and Bunn et al. 1980, pro Isaac 1978; Potts and Shipman 1981, pro Leakey 1971; Shipman et al. 1981a, pro Isaac 1977). The problem of identifying the agent of damage is most acute in the more remote periods of human evolution. It is tempting, but surely illconsidered, to envision our earliest ancestors as less intelligent versions of living human groups. Nonindustrial peoples, such as San Bushmen, Eskimos, and Australian aborigines, are favorite models for reconstructing early hominid behavior and lifestyle. Unfortunately, using this presumed resemblance as a basis for interpreting the fossil record incorporates a substantial element of risk. In other words, such an assumption may spur a misleading search for familiar patterns, while genuine but unhumanlike patterns are ignored because they are both unexpected and unfamiliar. Moreover, some of the information of greatest value in identifying taphonemic agents at work in the past is related to the sedimentary envi-

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ronment in which deposition occurred, yet good sedimentological data are too rarely recorded. Too, many fossil assemblages are surface-collected and sedimentary context is often unknown. Therefore, it is apparent that techniques which extract a maximum amount of taphonomic information directly from the fossils or bones themselves, and which rely on analytical rather than purely descriptive approaches, are needed. IDENTIFYING

HOMINID

ACTIVITIES

In recognition of this need, new approaches to dietary and behavioral information in the fossil record have been devised. For example, Walker (1981, 1980; Walker et al. 1978) has pioneered the study of tooth microwear as an indicator of diet. Isaac and Harris (1975) have refocused attention on the means by which sites themselves are recognized, by investigating the background densities of bones and stone artifacts. Dietary practices have also been extracted from fossils by trace element and isotope analysis (De Niro and Epstein 1978; De Niro and Schoeninger 1982; Schoeninger 1982; Van der Met-we and Vogel 1978) and from evidence of pathologies related to diet (Walker et al. 1982). Finally, several workers have reported the presence of cutmarks on fossils as evidence of hominid activity (Bunn 1983b, 1981; Bunn et al. 1980; Potts and Shipman 1981; Shipman 1981a, b; Clark 1982). To eat meat, hominids must have access to dead animals, whether these carcasses are obtained by hunting or scavenging. Availability of edible animals is easily demonstrated by the co-occurrence in space and time of hominids and expected prey species. Access to those animals is more difficult to prove. Schaller and Lowther (1969) tried to demonstrate access by documenting the number of animals they were able to catch by hand or obtain by scavenging while on foot in the Serengeti National Park. Their study indicates clearly that modem humans are capable of obtaining reasonable quantities of meat in such an environment without using advanced technology. Unfortunately, this study shows little about the capabilities of Australopithecus or early Homo, which differed in many ways from modem humans (Shipman 1982). Others (Bonnichsen 1979, 1973; Bunn 1981; Dart 1959, 1957, 1949; Morlan 1980; Shipman et al. 1981a) have tried to identify particular types of breakage unique to hominid activities, with varying success, Since any particular taphonomic agent is probably capable of making at least one of any type of break or damage, such analyses are best confined to statistical comparisons of overall breakage patterns in assemblages of known and unknown taphonomic history. The burning of bones may also be indicative of hominid access, if it can be

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shown that similar effects do not occur as a result of natural fires (Gowlett et al. 1981; but see Isaac 1982). We are currently investigating this topic in detail. The logic behind using cutmarks as evidence of hominid activities is straightforward. Cutmarks, as evidence, have the advantage that they must be made by tools the likes of which have never been produced by nonhominids under natural conditions. Thus the presence of cutmarks is excellent and direct evidence that hominids had access to a particular bone and that they used this access. However, cutmarks do not demonstrate that hominids indulged in meat eating (contra Bunn 1981). Cutmarks indicate only that hominids used artifacts on the tissues of animals. It is entirely possible that animal carcasses represented resources from which a variety of useful materials could be obtained by early hominids. Later hominids and humans used many different materials derived from carcasses, such as (1) meat, marrow, and fat for eating; (2) bones, horns, and teeth for tool making; (3) skin, fur, and tendons for use in making shelters, clothing, carrying devices, and ropes; (4) skulls as containers or ceremonial objects; (5) blood for drinking. Because all, some, or none of these may have been utilized by early hominids, we can see no justification for favoring meat as the primary objective in carcass processing in the absence of supporting evidence. It is apparent that tools would be useful or necessary in obtaining many of these materials and, thus, cutmarks can be made on animal bones for a variety of reasons. Cutmarks cannot be facilely equated with the practice of meat eating. Furthermore, since many studies of marks on bones from early hominid sites show that carnivores have also damaged the bones (e.g., Bunn, 1981; Potts and Shipman 1981; Shipman 1981a), the presence of cutmarks cannot be taken as indicating that hominids were the only or primary taphonomic agent at work. Nevertheless, cutmarks do constitute a signature for hominid involvement with carcasses, regardless of the intent of that involvement. This observation, in turn, raises a new major issue: can cutmarks be recognized reliably without being confused with other like marks? If techniques cannot be devised that enable the positive identification of cutmarks, then this new criterion represents no substantive advance over the co-occurrence of bones and artifacts as a means of identifying butchery or other types of sites. Elsewhere, Shipman (1981a:365) has proposed two criteria that must be met if hominid activity is to be used as an explanation for the features of a site or assemblage. Posed as questions, these are

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(1) Do the features of the unknown mark show the same features as bones damaged by a single, known cause? (2) Are those features demonstrably distinct from those produced by other known taphonomic agents? In other words, both similarity and distinctness are important. In that same paper, Shipman has shown that known cutmarks and toothmarks do not always differ substantially in gross appearance. Thus, other criteria and methods of examination are needed to identify unknown marks with certainty. CRITERIA

FOR IDENTIFYING

UNKNOWN

MARKS

Various criteria useful for distinguishing cutmarks from toothmarks have been explicitly or implicitly stated in the literature. Studying bones from Olduvai Beds I and II, Bunn (1981) reports that marks he interprets as being cutmarks are about one-third the width of those he interprets as being carnivore tooth scratches. Data presented elsewhere (Shipman 1983) indicate that, in a measured sample of 166 known stone tool butchery marks and 103 known carnivore tooth scratches, mark width is a poor criterion on which to identify the agent of damage. The mean maximum width of cutmarks in that sample does not differ significantly from that of tooth scratches using either the student’s t test or the KolmogorovSmirnov test.* The mean minimum width of these cutmarks is signiticantly narrower than that of tooth scratches, using the same sample and the same tests 0, < 0.05 in both cases). Unfortunately, this fact is of negligible usefulness in interpreting marks on fossils since the ranges of minimum widths overlap extensively (cutmark range: 0.05-4.2 mm; tooth scratch range: 0.05 - 3 mm). Cross-sectional shape, suggested by Potts and Shipman (1981) and Bunn (1981) to be a useful criterion for recognizing marks, has proved to be highly variable, at least in slicing marks and toothmarks (Shipman 1983). Therefore, we now reject this criterion. Microscopic criteria have also been suggested as a means of identifying various types of unknown marks, including cutmarks, carnivore toothmarks, rodent gnawing marks, weathering, sedimentary abrasion, burning, root etching, and trampling (Potts and Shipman 1981; Shipman 1981a, b, 1983). * Walker (personal communication) has argued that neither of these statistical tests can be applied validly in the case of artificial populations such as collections of toothmarks made by different species. An anonymous reviewer of Shipman (1983), in which the fuller description of these data and their significance appears, feels the Kolmogorov-Smirnov text is valid but the student’s t test is not. Our initial assessment was that the student’s t test was the most appropriate one. In short, we tind ourselves in a boggy, statistical morass and leave the readers to accept or reject these tests at their discretion.

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The technique compares the functional features of marks of known origin with those of unknown origin, using a scanning electron microscope @EM) to inspect bone surface replicas. Replicas are used because original specimens are often not available on loan and because originals will not usually fit into the chamber of the SEM. An SEM offers several advantages over a binocular microscope for inspection of replicas: easier specimen manipulation, superior resolution, yielding higher magnification, and greater depth of field. Features apparent during SEM inspection of replicas may be obscure or invisible under a binocular microscope (see Fig. 1 in Shipman 1981a). The methodology we used is described more fully in the Appendix. In summary, then, microscopic criteria are the most reliable means of identifying marks of unknown origin. But if these criteria are to be used widely to document the effects of particular hominid behaviors, a thorough knowledge of the features and normal variations in known marks is essential. We present here detailed information on the microscopic appearance of replicas of a large sample of known slicing marks, carnivore tooth scratches, and rodent gnawing marks. These three types of marks are functional equivalents (see Potts and Shipman 1981 and Shipman 198Ia for discussion) and thus possess the greatest potential to be confused with each other. Our experiments and their results will be given in three separate sections below. FEATURES

OF SLICING

MARKS

Without exception, every one of a sample of over 300 experimentally made slicing marks shows the diagnostic microscopic criteria described elsewhere (Potts and Shipman 1981; Shipman, 1981a, b). In brief, a slicing mark is an elongate groove containing within its edges multiple, fine, parallel striations oriented longitudinally. Slicing marks sometimes appear to be V-shaped in section, especially when viewed from above, but their actual cross section is of variable shape. Ancient slicing marks appearing on fossils share the same microscopic features as experimental ones (Potts and Shipman 1981; Shipman 1981a, b). In addition, they are of similar color to the rest of the external bone surface, in contrast to preparator’s marks which are frequently, but not invariably, lighter in color. Preparator’s marks sometimes show microscopic striations, like true slicing marks, but often show one or more other microscopic or gross features by which they can be identified: light color; jagged edges to the main groove, produced by flaking on a miniature scale; and other features, such as crossing over matrix, running up the side of a postfossilization thrust fault on the bone surface, or main-

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taming a straight course while crossing postfossilization cracks that have displaced the original bone fragments. The striations typical of slicing marks are not present in any one of our entire sample of known carnivore tooth scratches (N > 200; see below). Rodent gnawing marks occasionally show superficially similar linear striations, but these can be distinguished from the striations of slicing marks by means described below. While the constancy of these microscopic morphological features in slicing marks is heartening, other types of variation do occur in slicing marks that may aid in their identification. We carried out a set of experiments using newly manufactured tools and fresh bones that were designed to investigate six possible sources of variability in slicing marks: (A) the raw material from which the tools are made; (B) the interposition of soft tissues between the tool and the bone surface; (C) the repeated use of a single, unretouched edge; (D) the direction of the stroke used to make the mark (or directionality of the mark); (E) the intersection of slicing marks (or sequence); (F) the abrasion of cutmarked bones by waterborne sedimentary partitles . Each set of experiments and its results will be discussed separately. (A) Raw Materials Stone tools were manufactured by us or by colleagues using flint, chert, lava, obsidian, basalt, and quartzite. These tools were used in two ways: (1) to mark clean or periosteum-covered bones, using a slicing motion; (2) to remove flesh, ligaments, joint capsules, and periosteum from partial animal limbs, using a variety of motions. In addition, bone expediency tools (Frison 1974) were manufactured by us or by others from long bones of large bovids, or, in one case, elephant bones (Stanford et al. 1981). Bone tools were not intentionally shaped or flaked; sharp edges produced by breaking the bones were utilized without further modification. Bone tools, like stone tools, were used to mark cleaned bones and to deflesh intact anatomical units. Cleaned bone surfaces were replicated prior to cutting, after cutting, and after boiling, which removes the last traces of soft tissues but does not alter the bone surface morphology. Over 300 experimentally produced marks were replicated and inspected as described above, using the SEM. As with all parts of this study, results were documented in our notes and in photographs made during SEM inspection.

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No distinction was apparent between marks made with different raw materials (Fig. 1). Bone tool marks as a group seemed to be generally shallower and broader than stone tool marks, but this observation is of no use in identifying an individual, unknown mark. Without exception, all stone or bone tool slicing marks showed the typical, multiple, fine striations within and parallel to the long axis of the main groove. Although no systematic experiments were performed with metal tools, a few examples of metal tool marks were accidentally created. These showed similar features. Some marks revealed features directly related to the morphology of the tool that made them. Both stone and bone tools occasionally produced grooves with two distinct low tracks rather than a single nadir (Fig. 2). This phenomenon makes the groove look as if it has two corners connected by a flat bottom, although the actual cross-sectional shape is variable. Such squared-off grooves are produced by tools with two distinct peaks on the cutting edge and almost invariably result if the peaks are offset from the midline of the cutting edge. A second phenomenon functionally related to edge morphology is the shoulder effect (Fig. 3). Shoulder effects are short marks which accompany slicing marks and which are made with the same stroke as the slicing mark. Shoulder effects may parallel or diverge from the main groove for part of its length. We believe that shoulder effects are produced by contact between the tool’s shoulder and the bone during cutting. Shoulder effects were abundant in our sample which can, in part, be explained by the muscular actions involved in slicing. As the tool is drawn across the bone towards the person using it, the triceps muscle contracts to exert downward pressure on the tool. Simultaneously, the biceps, brachioradialis and brachialis muscles are used to draw the hand and tool towards the body. However, both the brachioradialis and the biceps tend to supinate the hand slightly, producing a lateral rolling motion of the hand that may bring the shoulder of the tool into contact with the bone. Alternatively, a slicing motion can be achieved by abducting the arm and extending the shoulder while drawing the hand and tool across the bone. In this case, there is a tendency to rotate the forearm and hand medially from a pronated position, thus bringing the other shoulder of the tool into contact with the bone. Not all shoulder effects are found at the tail end of slicing marks, so their presence cannot be used to assess directionality. Features we call barbs were present on a small number of experimentally made slicing marks (Fig. 4). Barbs occur on both heads and tails of slicing marks. They are apparently caused by small, inadvertent motions of the hand either in initiating or in terminating a stroke. Features similar to barbs have not been observed on any of several hundred known tooth marks.

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a

I b FIG. 1. Slicing marks made by tools of different raw materials, such as flint (a) and bone @I, shIOW similar microscopic features; they are elongate grooves with multiple, fine, parallel sl triations in the main groove.

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FIG . 2. This squared-off groove is a dual track produced by a single slicing motion. The tool edge had offset points.

FIG. 3. The shoulder effect (sh) deviates from the main groove (g) in this slicing mark created with a single stroke.

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a

b FIG. 4. Barbs, like the one shown in this micrograph (a), occur at both heads and tails of slicing marks. A tracing of the barb (b) emphasizes its outlines.

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Another important result of this study is that stone tools leave more cutmarks than do bone tools. Two sheep elbows of comparable size and fleshiness were processed to a comparable state of cleanness. One elbow was butchered and cleaned of soft tissues for approximately 20 minutes using a single obsidian flake; the other was butchered with several bone flakes and required approximately 80 minutes to reach a similar state. The elbows were boiled to remove all remaining tissue; the marks were then replicated. The marks on the two elbows were morphologically identical However, in this experiment, nearly three times the number of cutmarks appeared on the obsidian-butchered joint as on the bone-butchered joint, even though less time was spent cutting up the former. While it would be unwise to expect this 3:l ratio to persist at archaeological sites, it is clear that bone tool marks are much less common than stone tool marks. (B) Soft Tissues The only experiment in which we could monitor the effects of soft tissues interposed between the tool edges and the bone surfaces were those in which bones had been cleaned down to the periosteum prior to the experiment. We replicated these bone surfaces with the periosteum intact, with the periosteum cut, and with the periosteum removed by boiling. This procedure enabled us to control for the presence of marks made during cleaning. It also enabled us to compare the features of individual slicing marks with the periosteum present and absent, to determine the extent to which the periosteum shielded the bone from damage. We found that many of the apparent features of any single cutmark are actually features on the periosteum rather than on the bone itself. Figure 5 (a, b) shows the same marks with and without periosteum. The widths of the marks without periosteum are consistently narrower than those with periosteum, demonstrating that even this thin (less than 1 mm) layer of soft tissue serves to shield the bone from marks. Logically, the presence of additional soft tissue, as in actual butchering, will protect the bone from marks to an even greater degree. (C) Repeated

Use

Because it is well known that stone tools become progressively duller with use, we investigated the extent to which slicing marks made with a single, unretouched edge changed with use. In this study, three variables that might change with repeated use were considered: (1) presence or absence of the diagnostic microscopic features; (2) maximum and minimum width of the slicing marks; and (3) details of the microscopic features.

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b FIG. 5. This series of slicing marks was replicated and photographed with the periosteum intact (a) and removed by boiling (b). Notice that the width of the marks on the bone surface is narrower than it appears to be with the periosteum in place.

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A flint tool with an edge angle varying between 78 and 90”, as measured from points 1 mm to either side of the edge, was used to make 10 slicing marks on a cleaned bovid innominate. The first 8 marks paralleled each other; the last 2 marks intersected those at right angles. The same flint tool was also used to make 250 additional slicing marks on cleaned bovid ribs, making a total of 260 marks with one tool. One area was cut with a sawing motion, so that the tool was not lifted from the bone surface between strokes. We recorded the sequence of all 260 marks and the direction of each stroke as it was made. These data were used in other parts of this study (see below). All resultant marks were replicated and inspected under the SEM. During this part of the study, we attempted to keep the edge of the tool roughly perpendicular to the bone surface at all times. The flint edge used for this part of the study was replicated before and after use. Inspection of these replicas showed that the edge was used enough to acquire a localized polish, such as described by Keeley (1980) for working bone. Without exception, all of the slicing marks created in this study-and, indeed, all of the known slicing marks inspected by the authors for any reason-revealed the diagnostic features described previously (Potts and Shipman 1981; Shipman 1981a, b, 1983). A sample of 70 marks, including marks made at all stages of the experiment, was measured using an ocular micrometer. Table 1 presents the data on the maxima and minima of these marks. The widths of the 260 marks made with a single tool edge showed considerable variability. Surprisingly, there is no discernable trend in width variability; mark width has no regular relationship to sequence. In assessing these data, it is important to realize that only slicing marks were considered here; the variability in width would undoubtedly be greater if chopping and scraping marks had been made and were included in the sample. Further, the variability in widths is probably reduced because all of the marks were made with the same tool by the same individual, using similar motions and held at similar angles to the bone surface. Therefore, these data probably represent the minimum variability in cutmark width that might be expected to occur under normal conditions . The details of slicing marks made in this experiment showed relatively little change with repeated use. For example, Fig. 6 compares the first slicing mark with the 250th in the rib series. They are remarkably similar in terms of frequency and spacing of fine striations within the main groove. This suggests that the microscopic features of cutmarks might be used to identify the particular tool that made them, if the tool edge had not been retouched and if the motion used were similar throughout. To identify the

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a

I b

IG.6.

F (b) iin

The first slicing mark (a) in a series of 250 is remarkably similar to the last mark 1:hat series.

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tool responsible for a given mark, a new cutmark would have to be made experimentally and then its features matched to those of the mark in question, in an approach analogous to the identification of the gun that fired a particular bullet in ballistics. (0) Directionality

The direction in which cutting strokes were made is information that would be useful in detailed reconstructions of carcass processing and butchery patterns. It is also possible that, if directionality could be determined for marks on bones from early hominid sites, such data might constitute proof of handedness among early hominids. The determination of handedness would, in turn, show that specialization of the two hemispheres of the brain for different tasks had already occurred. This would represent a major advance in our understanding of brain evolution (see Kimura 1979, 1976; LeMay 1975; LeMay and Culebras 1972; Passingham 1981). Because the implications of deduced directionality are so farreaching, we examined our experimental slicing marks for consistent and reliable indicators of the direction of the strokes that produced them. The primary data for this aspect of the study came from the set of 260 slicing marks made with a single tool (see above). Data on the directionality of marks made by tools of different raw materials were also used. As in other parts of this study, the search for microscopic features was conducted using replicas of marked surfaces and the SEM. Contrary to our expectations, we found no features that consistently and accurately identified either the head or tail end of slicing marks. Progressive and gradual narrowing of cutmarks occurred at both ends or either end, as did abrupt truncation of slicing marks. Neither shoulder effects nor barbs occurred at only one end (Fig. 7). Unfortunately, we have found no criteria for deducing directionality yet. Q

Intersecting

Marks

(Sequence)

Earlier work (Potts and Shipman 1981; Shipman 1981a) suggests that when marks overlap, the sequence in which they were made is detectable. When intersecting marks are of different types, such as cutmarks and toothmarks, sequence may indicate which agent had first access to a carcass-and thus, presumably, which was the hunter and which the scavenger. When intersecting marks are all cutmarks, determining the sequence may be useful in reconstructing butchery practices. To develop criteria for deducing the sequence in which marks are made, we made 20 intersecting marks on cleaned cow innominates, using flint and chert tools. We recorded the sequence and directionality of each

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FIG. 7. In this series of slicing marks, shoulder effects (sh) occur at both heads and tails of the different marks. The large arrow indicates the directionality of the marks.

mark and replicated the bone surfaces before and after cutting, so that we could document and discount any extraneous butchers’ marks. We examined each replicated intersection under the SEM and deduced sequence on the basis of morphology as a blind test, consulting our notes only after inferred sequences had been recorded. Inspection of the areas of intersection at high power revealed that the fine striations of the second mark overlie and partially obliterate those of the first mark (Fig. 8). This generalization is not useful if one mark is substantially deeper than the other, since the striations at the nadir of the deeper mark are unlikely to be affected by those of a shallower mark. Our experiments show that the second mark, regardless of its depth, will draw periosteum and bone fragments across the groove left by the first mark (Fig. 9a). When the periosteum is intact, this action walls off the originally continuous segments of the first mark. Once the periosteum is removed, the effects are more subtle (Fig. 9b). In fresh bone, there is still sufficient elasticity for bony material to be drawn into a partial wall across the earlier groove. It is possible, then, that this criterion of sequence will survive fossilization if preservation is good and if the bone were fresh when cut. If, however, preservation is poor, if the bone were

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E3. %I FIG. 8. The fine striations of the second mark (2) overlie and partially obscure those of the first slicing mark (1). (Arrows indicate direction of stroke).

dry when cut, or if they are of different depths, there may be no way to establish the sequence in which overlapping marks were made. (F) Sedimentary Abrasion

Serious problems in distinguishing between hominid-formed assemblages and hydraulic accumulations of bones have been raised by Binford (1981, 1977) and others. The presence of cutmarks on bones from some early sites (Olduvai, Potts and Shipman 1981; Koobi Fora, Bunn 1981) provides proof that hominids damaged those bones. But in ignorance of the effects of sedimentary abrasion on cutmarks, it is still possible to argue that the bones were accumulated hydraulically, after being damaged by hominids. To document the effects of sedimentary abrasion on cutmarked bones, we performed two experiments. Bones were cut using metal and stone tools and then replicated. The bones were then placed in a geologic tumbling barrel with 700 ml of water and 300 ml of poorly sorted sand. The mixture was tumbled at a rate of 1800 t-pm. At intervals, the bones were extracted from the barrel and replicated. We hesitate to translate hours of abrasion in our tumbling barrel into linear units (miles or kilometers) of hydraulic transport under natural

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a

b FIG. 9. The second stroke in this pair of overlapping marks has drawn periosteum and fragments of bone across the groove left by the first stroke (a). With the periosteum removed (b), the fragments of bone still block the first groove.

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conditions for several reasons which are explained more fully elsewhere (Shipman and Rose 1983). In brief, bones in a tumbling barrel are exposed to the impact of sedimentary particles more continuously than are bones in natural stream conditions; tumbled bones are also subjected to a more constant velocity than is likely to be realistic. We can estimate the distance traveled by our bones in this experiment: one hour equals approximately 0.72 kilometers of tumbler distance. However, we caution readers strongly against taking tumbler distance as the equivalent of actual distance of transport under natural conditions. Sedimentary abrasion removes all diagnostic, microscopic features of cutmarks in as little as five hours of tumbling. Figure 10 shows that the line striations of slicing marks are completely obliterated, leaving a smooth, rounded indentation, after very little abrasion. In contrast, more extensive lab experiments on abrasion that will be reported elsewhere (Shipman and Rose 1983) show that grossly apparent changes in bone surfaces occur after about 35 hours of abrasion. Thus, a substantial discrepancy exists between the actual onset of abrasion, which can be detected only when pre-abrasion control replicas are available, and the appearance of abrasion visible at a gross level. In our experiments, sedimentary abrasion rarely produced scratches or other elongate grooves, regardless of the sediment size, the inclusion or exclusion of water, the condition of the bones (fresh, weathered, fossilized, whole, or broken), and the duration of tumbling. None of the grooves produced in our abrasion experiments contained the fine, parallel striations typical of slicing marks. These results suggest that (1) sedimentary abrasion of any significant duration will obliterate slicing marks; (2) sedimentary abrasion will not produce marks that mimic slicing marks; and (3) sedimentary abrasion will occasionally produce marks that mimic carnivore tooth scratches. Of course, complex situations not recreated in our experiments may occur and these may yield results different from ours. A problematic situation may occur if slicing marks are made through a layer of soft tissue, most of which remains in place and which might be expected to shield the marks from obliteration during sedimentary abrasion. In such a situation, the clearest evidence that the bones had been transported will derive from sedimentological studies, not those of the microscopic morphology of the bone surface. It is clear that all possible sources of information about the depositional environment and site formation events must be utilized if an accurate and meaningful reconstruction of the taphonomic history of the assemblage is to be made. FEATURES

OF CARNIVORE

TOOTH

SCRATCHES

Our sample includes over 200 known toothmarks on modern bones. These have been made by feral and captive carnivores that range in size

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a

b FIG. 10. Two experimentally made slicing marks show typical fine striations prior to abrasion (a). After five hours of tumbling with water and poorly sorted sand (b), the same marks have lost their striations and are broad. rounded indentations.

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from very small (raccoon) to very large (Kodiak bear). Because our interests lie primarily in the interpretation of African materials, all major extant families of African carnivores are represented by several species. Both juvenile and adult individuals chewed on the bones in our sample. An expected source of variation in tooth scratches is the difference in basic tooth or cusp morphology. Carnivores use incisors, canines, premolars, and molars in chewing bones, teeth which obviously differ in their size, shape, and acuteness of cutting edges. Further, there are obvious differences in the morphology of any one type of tooth between species. For example, the cheetah’s premolars are elongated, carnassial blades for slicing whereas those of the spotted hyena are heavy, blunt cones for crushing. If the teeth used in any given chewing bout could be identified, the relevant features of those teeth could be compared with the resultant marks. We attempted to explore this presumed link between tooth and mark morphology by filming zoo animals as they chewed on bones. Unfortunately, it proved impossible to keep the animal’s mouth in view, much less in focus, during the chewing episode. Even zoo animals, accustomed to the presence of observers, became disturbed by our presence and either hid or abandoned the bones, so this aspect of our project was terminated. We were able to document variations in the types of toothmarks left by carnivores on bones in our sample. The three categories of marks described earlier (Potts and Shipman 1981; Shipman 1981a, b)-tooth scratches, incisal gnawing marks, and punctures-are adequate to describe the marks we have observed on carnivore-chewed bones. Another category of damage, produced by licking and sucking of bones, produces eroded-looking areas of bone but no distinct marks. None of the carnivore tooth scratches in our sample showed multiple, tine, parallel striations like those seen in slicing marks. Although isolated or scattered tooth scratches resemble slicing marks at a gross level, multiple toothmarks on a single bone are usually readily recognizable without magnification. Areas that have been subjected to repeated gnawing and chewing show many tooth scratches interspersed with obvious punctures. The tooth scratches frequently intersect each other and are more irregular and sinuous in course than multiple slicing marks usually are. It should be noted, however, that individual tooth scratches are frequently short, straight, and narrow, thus conforming to some researchers’ concepts of typical slicing mark morphology, and require microscopic inspection if they are to be identified with certainty. FEATURES

OF RODENT

GNAWING

MARKS

We have inspected over 175 known rodent gnawing marks under the SEM. Much of the sample was originally collected by Gary Haynes, who

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observed the African crested porcupine (Hystrix), the red squirrel (Tumiasciurus), the brush-tailed porcupine (Atherurus), and an unidentified mouse that was probably Peromyscus gnawing the bones. We also collected bones gnawed by the red squirrel (Sciurus carolinensis) and additional porcupine-gnawed bones. Upon gross inspection, the rodent gnawing marks can be characterized as broad, flat-bottomed grooves often occurring as a series of parallel or subparallel marks. Fine, parallel striations running longitudinally in these grooves can be observed in some specimens; these are infrequently present and result from repeated gnawing in a small area. Thus, striated rodent gnawing marks superficially mimic scraping marks but not slicing marks. This resemblance is discussed in greater detail below. Two general patterns of gnawing marks occurred on our sample. We have called these patterns fan-shaped and chaotic, according to the orientation of the marks. The fan-shaped pattern is apparent without magnification (Fig. 11). It is caused by the way some rodents chew, using the upper incisors as a fixed pivot. The animal reaches out repeatedly with its lower incisors, striking the bones with those teeth and then drawing them back towards the uppers. Thus the point of impact of the lower incisors changes each time, creating the outer edge of the fan, but the

FIG. 11. An example of the fan-shaped pattern of rodent gnawing. This bone was gnawed by a mouse. The apex of the several overlapping fans visible in this micrograph is towards the bottom.

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end point of each gnaw is fixed, creating the apex of the fan. We have observed fan-shaped gnawing patterns often on squirrel-chewed bones. The second or chaotic pattern is produced by a different mode of gnawing, in which both upper and lower incisors are drawn across the bone surface towards each other. As the animal moves its head, the point of impact of the incisors shifts slightly with each gnaw, producing a broad, depressed area traversed by many intersecting or overlapping marks (Fig. 12). This pattern is more typical of porcupine- or mouse-gnawed bones and more closely resembles scraping marks than does the fan-shaped pattern. Under the SEM, both patterns seem to be the result of repeated gnawing actions within a confined area. There is a considerable overlap of individual gnawing marks, making it difficult to identify the edge of any particular mark with confidence. The red squirrel, in particular, produced deep grooves (up to 1 mm in depth: Fig. 13) by persistent gnawing. The width of the individual grooves, insofar as this can be determined, is a poor indicator of the size of the incisors of the species involved. Even species that gnaw repeatedly in the same place move their teeth laterally to a small degree with each gnaw. Thus the resultant mark may be much wider than the actual tooth width and much deeper than any single gnaw. If the lateral movement is of an intermediate degree, the marks may be narrower than the incisors, since the actual cutting edge of the tooth is

FIG. 12. An example of chaotic gnawing. Multiple gnawing marks cross and overlap on this bone that was gnawed by a porcupine.

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FIG. 13. An example of deep grooves caused by repeated gnawing in a restricted area. This bone was gnawed by a red squirrel. Each deep groove is actually the result of several gnaws and is wider than any single gnaw. The linear striations in the bottom of the grooves are parts of marks overlain by others (see Fig. 15).

narrower than the overall width of the tip (Fig. 14) because the tip is rounded. Finally, if the lateral movement is large, the high points between marks will be obliterated by later marks, so that the net effect is one of wider marks than could be made by any single gnaw (Fig. 15). This latter situation creates striations, but these are actually the original edges of individual marks that are now overlaid and enlarged by later gnaws. Too, some rodents have ridged incisors or small cuspules on their enamel which might be expected to leave striations. Anatomical features, such as ridges or cuspules, can be expected to occur at regular intervals on the incisors; their presence would be suggested by a regular spacing of the resultant striations within the groove. Another common feature observed in gnawing marks are chattermarks: small ridges perpendicular to the long axis of the groove produced by variations in the resistance of the bone surface to gnawing (Fig. 16). These are also present in some carnivore tooth scratches. Scraping marks share many of the characteristics of gnawing marks, yet are fundamentally distinct in several ways (Fig. 17a, b). Both types of marks can be described as broad, usually shallow grooves; both may create a wide area traversed by striations; both frequently intersect other such marks. As can be seen by comparing Figs. 17a and b, scraping marks

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. t& FIG. 14. Rodent incisors may produce marks narrower than the incisor width. Because the tip of an incisor is rounded, the cutting edge (a) may be narrower than the actual incisor width (b).

have a crisper appearance because their edges are better defined. In contrast, gnawing marks have a softer, more rounded and less well-defined edge. The impact point of gnawing marks is often readily identifiable (Fig. 18), whereas those of scraping marks are not. At a microscopic level, the scraping marks are linear and appear to be either straight or smoothly curving; gnawing marks are more wavy, tightly curved, and irregular in their course. Finally, chattermarks are common in gnawing marks and are rare or absent in scraping marks. Thus, although functionally similar, rodent marks can be readily distinguished from hominid-caused marks using SEM inspection and the knowledge of normal mark variations gleaned from our studies. SUMMARY

AND CONCLUSIONS

The observations on the features of slicing marks, carnivore tooth scratches, and rodent gnawing marks can be summarized under seven major points. First, microscopic criteria are usell and reliable in distinguishing among the types of marks discussed here. Each of these types of marks shows some variation yet retains a distinctive set of characteristics identifiable under SEM inspection. Thus, this technique can be used to identify individual bones processed by hominids using stone or bone tools or by carnivores or rodents using their teeth. Bones damaged by a combination

*

b

FIG. 15. Diagrammatic representation of the effects of repeated gnawing. The two gnawing marks made by the incisors in one stroke (a) are initially separated by a slight gap. A second gnawing action, displaced slightly to one side of the first, obliterates this gap and leaves a single, broad mark (b). Repeated gnawing creates a still wider gnawed area, containing linear striations that are remnants of earlier marks (c).

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FIG. 16. Chattermarks are produced when teeth encounter variations in hardness in the bone’s surface. Chattermarks (indicated by arrows) are perpendicular to the long axis of the groove.

of these three agents can also be identified. Ambiguous marks, the features of which are obscured by later events (such as weathering, postfossilization erosion, preparator’s treatments, etc.), occur and must be discounted in further analyses. Second, the raw material of which a tool is manufactured has little or no effect on the microscopic features of the resultant marks. Indeed, these microscopic features are remarkably constant on tool marks of all types. Thus, particular marks are only subtly linked to the tool that made them, making detailed reconstructions of the function of particular tools or tool types in carcass processing difficult. However, the morphology of the tool’s cutting edge, and probably its sharpness (i.e., the acuteness of its edge angle), are related to raw material and these factors do directly affect mark morphology. Squared-off marks and marks with shoulder effects directly reflect the morphology of the cutting edge and the angle at which the tool is held during use. Third, soft tissues have an important ability to shield bones from being marked by bone or stone tools. This observation explains the low percentage of cutmarks found on bones of known butchered animals (e.g., Crader 1983; Guilday et al. 1962). It is possible to butcher an entire animal without leaving any cutmarks, especially if bone tools are used. Therefore, it is unrealistic to expect that many fossils from a genuine butchery

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a

I

b 17. Comparison of rodent gnawing marks and stone tool scraping marks. An experimentally made scraping mark (a) appears to be more crisply defined and linear under magnification than an example of the chaotic gnawing pattern (b). Although both show similar features, such as broad, shallow grooves traversing a depressed area and containing microscopic striations, the rodent gnawing marks are rounder and softer in appearance and tend to be more wavy and irregular in course than the scraping marks. In addition, only gnawing marks and tooth scratches show chattermarks. FIG.

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FIG. 18. Impact points of rodent gnawing marks are readily discernible (arrows), unlike cutmarks, which may taper at both ends.

site will show cutmarks. In contrast, relatively more bones from carnivore-chewed or rodent-gnawed assemblages will show toothmarks, because these animals chew the same area repeatedly. This assertion is borne out by studies of assemblages accumulated by rodents and carnivores. For example, between 47 and 80% of the bones in striped hyena assemblages are damaged (Maguire et al. 1980; Shipman 1981b; Skinner et al. 1980); 80-94% of bones in spotted hyena lairs are damaged (Bearder 1977; Maguire et al. 1980); 68% of bones from brown hyena lairs are damaged (Maguire et al. 1980); and 22-100% of bones from porcupine lairs are gnawed or damaged (Brain 1981; Hendey and Singer 1965; Maguire 1976). Fourth, repeated use of a single, unretouched edge may produce progressive dullness but does not alter the morphology of the resultant slicing marks much, if the state of the bone and the angle at which the tool is held are kept reasonably constant. Thus it might be possible to match individual marks in an assemblage with the particular tools that made them if extensive experiments are carried out, but the process is likely to be time-consuming and tedious. Such a study might resolve controversies about some of the Paleolithic carvings suggested by some (Marshack 1972) to be calendars, since the argument rests on whether or not all of the marks were made at one time with one tool. In theory, at least, SEM analysis of the marks in question might show that they were all made by a single tool. However, as our experiments showed, one tool

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may produce slicing marks that vary if the angle of use varies. This fact means that the similarity of two marks is meaningful, indicating that they were made by one tool, but the dissimilarity of two marks does not indicate that they were made by different tools. Mar-shack’s argument will hold up only if the shape of a tool tightly restricts the position in which it can be used effectively and comfortably for incising a bone surface. Fifth, directionality of slicing marks is difficult to assess accurately on the basis of microscopic features. We are not optimistic that a means of determining directionality will be developed. Sixth, the sequence in which overlapping marks were made can be deduced in some circumstances. If the depths of the intersecting marks are reasonably similar, then the fine striations of the later mark will overlie and obscure those of the earlier mark. Therefore, if overlapping cutmarks and toothmarks are found on fossils, the sequence of access to that carcass can be deduced. A consistent pattern of first access by carnivores would suggest that hominids obtained carcasses predominantly by scavenging; a consistent pattern of first access by hominids would suggest that the hominids obtained carcasses predominantly by hunting. Sequence is not always easily determined, however, because marks of different depths are difficult to assess, as are marks on poorly preserved bones. Seventh, both stone tool and bone tool slicing marks lose their microscopic features after brief exposure to sedimentary abrasion. Thus, fossils bearing marks that retain microscopic features have probably undergone little or no fluvial abrasion. Whether or not this means that the bones have undergone hydraulic transport is another issue. Our experimental results lead us to expect that visible sedimentary abrasion and slicing marks possessing all of the microscopic criteria would infrequently cooccur. However, this conclusion must be tempered with due caution, since soft tissues shield bone surfaces from abrasion and might prevent the obliteration of cutmarks. Therefore, evidence of transport and fluvial activity must be sought from other sources before firm conclusions can be reached. The implications of these findings are far-reaching. Our work demonstrates that bones and carcasses damaged by hominids can be isolated from an assemblage, using microscopic criteria. Thus, the taphonomic history of individual bones can be reconstructed with reasonable certainty. However, the issue of reconstructing the taphonomic history of the assemblage as a whole or the site formation events is different. The techniques we have developed and employed in this study will permit an assemblage to be partitioned into components damaged by diEerent agents and thus presumably, but not necessarily, collected by those agents. One

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or even many cutmarks is not adequate evidence that hominids have been the major taphonomic agent affecting a site or assemblage. An assumption that is even more tenuously related to the evidence itself is that the spatial distribution of in situ fossils and artifacts reflects hominid behaviors simply because some of the fossils bear cutmarks. We caution against such facile and potentially misleading leaps of faith. Bunn (1983b) and others have observed that the roughly 20% cutmarked bones found in recent butchered assemblages is reasonably well matched by the 5-20% cutmarked bones found in some fossil assemblages. Although this observation is accurate, it is also accurate that the same proportion of cutmarked bones might occur in assemblages of complex taphonomic history. Therefore, we urge that a conservative approach be taken to the evidence. We suggest that hominid activity can be used as an explanation for the damage, spatial distribution, or other attributes of an assemblage only when alternative explanations can be ruled out and when positive evidence of hominid activity can be found. We conceive of three categories of evidence that might be found in support of the hominid hypothesis. In decreasing order of certainty, these are (1) Cutmarks, verified by SEM inspection or by the presence of barbs or shoulder effects, are evidence of maximum certainty that hominids have had access to and processed those individual bones. We would also include in this category bones articulated with cutmarked bones or other specimens reasonably supposed to belong to the same carcass. If it can be shown that some other type of damage, such as green bone fractures of proboscideans, can be caused only by hominids, then such bones also constitute first category evidence. (2) The second, less certain, category of evidence is that groups of bones can be shown to have an overall pattern of breakage that is statistically different from carnivore-broken bones derived from the same or similar species (see Shipman et al. 1981a for a fuller discussion). (3) As a least-certain category of evidence, simple spatial association with hominid remains, artifacts, or cutmarked bones will suffice, This category includes materials with no demonstrable functional link to hominids and their peculiar behaviors. An improvement in the clarity of hypothesis formation and interpretation of early hominid sites might result from the explicit statement of the category of certainty into which the evidence of hominid activity falls. Finally, we reiterate a caution stated earlier. In interpreting evidence of man’s past behavior, it is common practice to rely on analogies drawn from the behavior of recent, nonindustrial peoples. By looking for resemblances to the present, we may blind ourselves to the differences that actually existed. In fact, there is reason to suppose that the behavioral

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differences between ourselves and early hominids are substantial if not overwhelming, since there are obvious differences in stature, brain size to body size ratio, environment, animal community, and above all technological capabilities (Shipman 1983). The uniformitarian principle can be applied appropriately only to processes believed to remain constant over time, such as those involving physical, mechanical, or chemical laws (Shipman 1981b: 1I-12). It is not only inappropriate but also foolhardy to treat complex, learned behaviors like hunting, butchering, or meat eating as if they were either genetically programmed constants or immutable laws. It is time to create new hypotheses and testable interpretations of early hominid behaviors based on rigorously collected data rather than on possibly spurious and false analogies. APPENDIX:

METHODOLOGY

AND REPLICATION

TECHNIQUE

The replication methodology used in this study is a variation of one developed by Walker (Walker 1980; Walker et al. 1978). Bone surfaces are cleaned thoroughly using alcohol and acetone applied with a soft brush. Fossils must, in addition, be cleaned of matrix, glue, and preservative prior to replication. Cleanness is usually checked with a light microscope after the specimens have dried and have been blown free of dust with canned air. Small molds of bone surfaces are made by applying a cold-cure silastomer (Xantopren Blue manufactured by the Unitek Corp.) with a syringe. Once the molds have cured (setting time is usually about six minutes), they are peeled carefully from the bone surfaces. The molds are filled with a low viscosity epoxy (Epo-Tek #301, manufactured by Epoxy Technology, Inc.) after a rim or wall of silicone-based, moldable impression material (Optosil, manufactured by the Unitek Corp.) has been made to keep the epoxy on the mold. The epoxy positives are left to polymerize overnight and are then removed from the molds, mounted with glue onto SEM stubs, and sputter-coated with an extremely thin (200 A> layer of gold or gold-palladium to render them conductive (Hayat 1978). Silver paint is used to bridge the glue and create a conductive contact between the stub and the replica. Replicas made using this technique and these products have been compared to originals under the SEM; they routinely give a resolution of 0.1 to 1 micron and are usually indistinguishable from the originals at magnifications up to about 1500 x . Artifacts are occasionally produced by this replication technique, but they are readily recognizable and do not mimic cutmarks. The most common artifacts are bubbles, which appear on the replicas as spherical objects with smooth or lightly dimpled surfaces. Because the surface morphology of different pieces of bone is so vari-

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able, we do not use a standard specimen tilt or orientation in examining replicas under the SEM. Our experience has shown that rotating a specimen or changing its tilt often reveals previously unobserved features. Therefore, we routinely vary tilt from 0 to 45” and the orientation from 0 to 360”. Specimens are examined at magnifications ranging from about 10x to 1000x. Mark widths can be measured by using either a micron-marker bar attachment on the SEM or an ocular micrometer. Because marks are often small, measurements are most accurately made at magnifications of 50x or more. As reported elsewhere (Shipman 1983), mark width is highly variable along the length of a single mark, regardless of the agent that produced the mark. Therefore, as standard procedure, we measure both maximum and minimum mark width. Calipers do not give accurate measurements of indented features such as cutmarks or toothmarks. ACKNOWLEDGMENTS We thank the butchers at Eddie’s Supermarket for providing bones for this study and the Baltimore Zoo for letting us observe their animals. Blaire Van Valkenburgh and David Senie attempted to film animal feeding for us. Dennis Stanford, Rick Potts, Glynn Isaac, Gary Haynes, Henry Bunn, and Dan Fisher contributed cutmarked bones and advice. Mark Teaford, Robert Whallon, and some unknown reviewers contributed helpful comments on the manuscript. The National Science Foundation (BNS 80-1397 and BNS 80-2-1397), the National Institutes of Health Biomedical Research Program (5 S07RR07041-13), and the Boise Fund provided grants to support this work. Our appreciation goes to all, and to our husbands, Alan Walker and Ken Rose, for moral support and advice.

REFERENCES Aguirre, E., and P. Biberson 1965 Experiences de taille d’outils prehistoriques dans des OS d’elephant. Quaternaria 7:165-183. Ardrey, Robert A. 1961 Micnn genesis: A personal investigation into the animal origins and nature of man. Dell, New York. 1976 The hunting hypothesis: A personal conclusion concerning the evolutionary nature of man. Atheneum, New York. Bearder, Simon K. 1977 Feeding habits of spotted hyenas in a woodland habitat. East African Wildlife Journal 15:263-280. Behrensmeyer, A. K. 1973 The taphonomy and paleoecology of the Plio-Pleistocene vertebrate assemblages east of Lake Rudolf, Kenya. Unpublished Ph.D. thesis, Department of Geology, Harvard University. 1975 Taphonomy and paleoecology of the Plio-Pleistocene vertebrate assemblages east of Lake Rudolf, Kenya. Museum of Comparative Zoology Bulletin 146:473578.

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Taphonomic and ecologic information from bone weathering. Paleobiology 4: 150162. Behrensmeyer, A. K. and D. E. Dechant-Boaz 1980 The recent bones of Amboseli Park, Kenya, in relation to East African paleoecology. In Fossils in the making, edited by A. K. Behrensmeyer and A. P Hill, pp. 72-93. University of Chicago, Chicago. Behrensmeyer, A. K., David Western, and D. E. Dechant-Boaz 1979 New perspectives in vertebrate paleoecology from a recent bone assemblage. Paleobiology

5: 12-21.

Binford, Lewis R. 1977 Olorgesailie deserves more than the usual book review. Journal logical Bones:

of Anthropo-

Research 33:493-502. Ancient men and modern

1981 myths. Academic Press, San Francisco. Binford, Lewis R., and J. Bertram 1977 Bone frequencies and attritional processes. In For theory building in archeology, edited by L. R. Binford, pp. 77-156. Academic Press, New York. Boaz, Noel T., and A. K. Behrensmeyer 1976 Hominid taphonomy: Transport of human skeletal parts in an artificial fluviatile environment. American Journal of Physical Anthropology 45:53-60. Bonnichsen, Robson 1973 Some operational aspects of human and animal bone alterations. In Mammalian osteoarchaeology: North America, edited by B. M. Gilbert, pp. 9-24. Missouri Archaeological Society, Columbia. 1979 Pleistocene bone technology in the Beringian Refugium. Archaeological Survey of Canada,

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Brain, C. K. 1967 Hottentot food remains and their bearing on the interpretation of fossil bone assemblages. Scientific Papers of the Namib Desert Research Station 32: l-l 1. 1970 New finds at the Swartkrans australopithecine site. Nature (London) 225: 11121119. 1974 Some suggested procedures in the analysis of bone accumulations from southern African Quaternary sites. Annals of the Transvaal Museum 29(1):1-8. 1976 Some principles in the interpretation of bone accumulations associated with man. In Human origins, edited by Glynn Ll. Isaac and Elizabeth McCown, pp. 97-116. W. A. Benjamin, Menlo Park, Calif. 1980 Some criteria for the recognition of bone-collecting agencies in African caves. In Fossils in the making, edited by A. K. Behrensmeyer and A. P. Hill, pp. 108-130. Univ. of Chicago Press, Chicago. 1981 The hunters or the hunted? An introduction to African cave taphonomy. Univ. of Chicago Press, Chicago. Bryan, A. L. 1978 An overview of Paleo-American prehistory from a circum-Pacific perspective. In Early man in America from a circum-Pacific perspective, edited by A. L. Bryan, pp. 306-327. Archaeological Researches International, Occasional Paper #I of the Department of Anthropology, University of Alberta. Bunn, Henry T. 1981 Archaeological evidence for meat-eating by Plio-Pleistocene hominids from Koobi Fora and Olduvai Gorge. Nature (London) 291:574-577. 1983a Bones from a modem hunter-gatherer camp in Botswana. British Archaeological Reports, in press.

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