©1978 International Journal of African Historical Studies, Boston University, All Rights Reserved.
Glynn Isaac, Pope Valley, CA, March, 1969
|Review Article: OLORGESAILIE
by Charles M. Nelson
OLORGESAILIE: ARCHAEOLOGICAL STUDIES OF A MIDDLE PLEISTOCENE LAKE BASIN IN KENYA
by Glynn Ll. Isaac, assisted by Barbara Isaac
Chicago: The University of Chicago Press, 1977. Pp. xiv, 272.
In Olorgesailie, the Isaacs recapitulate and critically evaluate the data and ideas generated by one of the most productive research projects into early human behavior to be completed in the last decade. This project began in 1962 and was concluded in 1968 with the acceptance of Glynn Isaac's Ph.D. dissertation at Cambridge University.l The evidence and lines of inference which emerged from the research are clearly evident in a series of five earlier essays written to explore the implications of early human diet, the character and tempo of technological change among ancient human communities, and the identification of cultural phases and patterns during the Pleistocene.2 Isaac refers to these essays repeatedly in the presentation and interpretation of the data from Olorgesailie and urges his readers to turn to them for a broader comparative perspective.3 Students of ancient African history and human evolution who turn to Isaac's account of the research at Olorgesailie to better understand the archaeological contributions to these fields, would also do well to review the ideas presented in these five essays. Those already familiar with Isaac's general contributions to the field of palaeolithic archaeology will find the volume under review an invaluable critique of the limitations and uses of archaeological data in depicting the development of human cultural behavior.
Olorgesailie is a complex of archaeological sites situated in an arid section of the Gregory Rift in southern Kenya, East Africa. This complex of living sites is unusual because of its Middle Pleistocene age, dating to approximately 450,000 years ago. Sites of this age are uncommon, taking on particular importance because they refer to a period, associated with the Acheulean Industry and the hominid Homo erectus, during which many authorities4 believe culturally controlled patterns of adaptive behavior may have evolved for the first time. Olorgesailie is an especially important Middle Pleistocene locality because it contains a number of well-preserved living sites. The structure and contents of these sites can be compared systematically to document the range of recurrent behavior patterns of our ancient hominid ancestors and to test ideas about the rate and direction of behavioral change in early human communities.
Contributions to Palaeolithic Archaeology
Breadth of the Contributions. Through the research reported in this volume, Isaac has made basic contributions to the methodology of describing and interpreting flaked stone technology, and to the interpretation of technological variation through time, within a well delimited biosocial tradition. Highly focused studies of this nature are especially welcome because stone implements are the single most abundant source of direct evidence of early human behavior (pp. 97-98). Only by understanding the total context of the manufacture and use of stone tools can we hope to assess their meaning in broader human terms. This volume contributes to such an understanding in five important areas:
1) the critical appraisal of the imperfect nature of the evidence from which we facilely extrapolate the story of early human history and evolution (ch. 3),
2) the meaning of stone tools in their Lower Palaeolithic context (pp. 97-104),
3) the character of technological change during the Lower Palaeolithic over periods of long duration (pp. 208-217),
4) the understanding of technological variation in temporal clusters of closely related archaeological sites (pp. 208-217),
5 ) the first convincing quantitative analysis of general Acheulean tool morphology (chs. 5-8).
Understanding the Palaeolithic. Our conventional understanding of the Palaeolithic is best reflected by the copious chapters given over to this period in introductory texts dealing with human evolution and world prehistory. These interpretive summaries are often written by cultural or biological anthropologists with little direct knowledge of Lower Palaeolithic archaeology or technology. Available discussions of the limitations inherent in archaeological materials of this age are few and couched in very general terms.5 For this reason, it is not surprising to find numerous examples in which such information is uncritically over-interpreted6 or passed by in favor of more familiar data and concepts.'
All those writing, reviewing, or using such broad summaries in human evolution, world prehistory, or African history, will find that Isaac has made an extremely useful contribution in delimiting the character and applicability of the archaeological information, both from the excavated sites at Olorgesailie and for early Palaeolithic sites in general. Most useful is his evaluation of those limitations which are imposed by (1) the geological context of sites, (2) the precision of current dating techniques, (3) the palaeogeographic distribution of sites and significant economic activities, (4) the differential preservation of associated materials, such as the bones of economically important animals or the fossil pollen which is so important to reconstructing prehistoric climate and vegetation, and (5) the comparative technique of stone tool analysis. By discussing these factors explicitly, he is able to set clear and attainable goals for the study of the archaeological remains from Olorgesailie. As a result, the analysis grows naturally out of a body of well understood facts and the reader can understand the significance of the study and its conclusions without being an expert in African prehistory.
The Meaning of Stone Tools. Stone tools, manufactured by flaking a wide variety of fine grained rocks,8 constitute one of the chief lines of evidence customarily employed to infer the changing character and significance of behavior in ancient human communities. The importance which prehistorians attach to understanding stone tools derives, in part, from their consistently excellent state of preservation and great abundance in the buried sites which preserve past traces of human activity. Other equally important products of human activity, such as food remains and implements of bone, wood, shell, hide and fiber, are far less frequently preserved. Thus, like other important suites of early man sites in Africa,9 the prehistoric record at Olorgesailie is reduced to a single common denominator: flaked stone tools and the debris produced in their use and manufacture. This unavoidable situation would pose insurmountable difficulties for archaeological interpretation were it not for three facts. First, flaked stone implements have played a major role in human technology for roughly 2.5 million years, until stone was replaced widely by metal beginning some four thousand years ago. As a result, the evolution of human technology is recorded in detail by the myriad of stone implements recovered from thousands of archaeological sites throughout the world. Second, technology and the behavioral patterns which can be inferred from its existence, are an integral part of numerous other behavioral domains such as subsistence adaptations, the structure of productive labor and consumption, the identification and function of social institutions, and cultural interaction through trade and diffusion. And third, other important remains, such as the environmental distribution of sites, food remains, structures and perishable implements, are preserved frequently enough to expand our understanding of the associated technologies.
For all of these reasons, archaeologists tend to overemphasize stone tools (p. 207). On the one hand, all too many archaeological reports devote much space to highly detailed descriptive analyses of stone implements or the debris which is a byproduct of their manufacture. All too frequently, these descriptive studies reach no conclusions whatever regarding the meaning or significance of the implements so scrupulously measured, pictured, and verbally described. On the other hand, prehistorians are often all too eager to leap to conclusions about the significance or supposed potential significance of technology.10 A classic example of this occurred during the early 1960s with the substantiation of the very early occurrence of flaked stone tools from hominid sites at Olduvai Gorge and elsewhere in Africa. Archaeologists, along with many other anthropologists, argued strongly that the presence of stone tools indicated cultural behavior based on traditions passed from generation to generation through a socialization process dependent on language as a primary means of communication. Though plenty of available archaeological information could have been used to question this conclusion, it was anthropologists interested in comparative primate behavior and the evolution of speech who first strongly challenged this point of view.ll
In this regard, Isaac's work at Olorgesailie is both refreshing and stimulating because he (1) explicitly discusses the aspects of human behavior which are reflected in Lower Palaeolithic flaked stone tool technologies (p. 97-98), and (2) demonstrates subsequently how the technological assemblages from the Acheulean sites at Olorgesailie can be studied productively in order to document and elucidate significant behavioral patterns (ch. 9).
These conclusions arise from the quantitative analysis of the morphology of Acheulean tools which is, without a doubt, the most elegant and significant of its kind. No other extant analysis of a Lower Palaeolithic technology so clearly documents the design norms which underlie the typological categories commonly employed in the description and analysis of early stone tools. Indeed, it demonstrates, in direct and specific terms, the abilities and limitations of Homo erectus in the manufacture and use of flaked stone tools. This information assumes importance far beyond a mere wrinkle of detail in the history of technology. Changes in the quality of early hominid technological behavior provide a yardstick against which we can measure the evolution of cultural behavior itself.
Technological Change in the Lower Palaeolithic. The rate and character of technological change during the Lower Palaeolithic are central to our understanding of the emergence of cultural patterns of behavior and their relationship to the biological evolution of man. In Olorgesailie, Isaac examines two traditional views of Lower Palaeolithic technological change: (1) the idea that change occurred in progressive, incremental steps along a specific developmental pathway, and (2) the assumption that the rate of change followed a regular, geometric progression (pp. 2-3, 98-104, 206-213).l2 His analysis shows that there was little, if any, short- or long-term developmental change in Acheulean technology over a period of many thousands of years (p. 101). Coupled with a wide range of other data from Lower Palaeolithic Africa, this suggests that the first two million years of technological history was characterized by occasional periods of slow change and behavioral reintegration separated by longer periods during which technological behavior was remarkably stable.
While the meaning of these findings will require careful consideration to elucidate adequately, I would like to suggest that they will lead us to a radically different interpretation of human technological history, an interpretation which views early human technological behavior as an aspect of biological rather than cultural evolution.
Evolution of Cultural Behavior in the Human Line
Introduction. In his concluding remarks, Isaac states:
One million years ago, there existed upright, bipedal, tool making hominids. They seem to have lived in cooperating groups and to have hunted and shared food, but the archeological record suggests that by our standards their capacity for culture was slight. Very probably they lacked effective language and did not have the mind-brain configuration that we regard as human. By the end of the Middle Pleistocene, some fifty to one hundred thousand years ago, both the archeological and osteological evidence attest the emergence of hominids with fully human capabilities (p. 219).
The significance of this statement is enormous, for it places early human technological behavior in a radically new perspective which is destined to reshape our view of human history.l3 Traditionally, anthropologists have equated technology with culture and language; this is still true to a considerable extent. In this context, culture is considered a body of patterned behaviors shared by the members of a society and passed down by them from generation to generation as a complex body of tradition. The learning of this traditional body of knowledge and behavior occurs in the process of socialization, or enculturation, and is understood and imparted mainly through the abstract, symbolic system of communication and thought we call language. Changes in this complex body of tradition and the technological system which it supports occur in a systematic fashion through the process of innovation.l4 This process relies, in the first instance, on the uniquely human ability to think in and facilely manipulate complex abstract symbols. When expressed and acted upon in a social context, these symbols, and many of the rules by which they are manipulated, are referred to as language. Language is so intimately bound up with our ability to think creatively and to innovate, that all of our analytical paradigms for the analysis of technological innovation and change in cultural systems are linguistic by nature. For this reason, it was perfectly natural for anthropologists to think of the first emergence of technology, some 2.5 million years ago, as linguistic and cultural in character. Thus, the emergence of cultural behavior was seen in terms of (1) a dietary shift to include meat acquired through hunting, (2) the manufacture and daily use of technology in subsistence adaptations, and (3) the concurrent development of language as a means of thought and communication. This combination of patterns, which conforms to the definition of culture, was thought to be made possible by the evolution of changes in the structure and size of the human brain approximately 3 million years ago. Subsequent enlargement of the brain over the next 2.9 million years was thought of as a biological response to selective pressure for more elaborate forms of cultural behavior.15
Isaac's data from Olorgesailie, his conclusions about technological change during the Acheulean, and his concluding statement all call this model of human history into question by suggesting that patterns of technological behavior in early human communities may not have been passed and modified from generation to generation through the cultural mechanisms of symbolic language and innovation. Though this tantalizing point is left undeveloped by Isaac, the inescapable implication is that there were severe biological constraints, based in the size and complexity of the brain, which controlled much of the evolution of human technological behavior during Lower Palaeolithic times.
This line of reasoning is supported by the manner in which technology is integrated into the behavioral patterns of nonhuman primates, recent hunting and gathering societies, and our early hominid ancestors. In the wild, nonhuman primates do not employ technology in their behavioral adaptations on a day-to-day basis, though some species, such as the chimpanzee, use simple tools regularly in seasonally-spaced activities such as termite hunting.16 In captivity, many primates can be taught to make and use simple tools through imitative behavior. Some have been taught to manufacture stone tools similar to those employed by our Lower Palaeolithic ancestors.17 In contrast, our early hominid ancestors manufactured and used stone tools in prolific quantities from day to day in activities intimately connected with the food quest such as butchering the carcasses of animals. This heavy reliance on technology at the core of early hominid adaptations has always implied to anthropologists that the appearance of technology itself marks the evolution of behavioral patterns significantly more complex than anything in the potential repertory of the Old World monkeys and the great apes. For a time, it was assumed that this emerging complexity in early human behavior represented the appearance of culture itself.18 Yet a close comparison of early hominid and recent hunter/gatherer technologies demonstrates that this conclusion was incorrect.
Isaac's analysis of the Acheulean sites at Olorgesailie suggests that patterns of technological behavior for Homo erectus were very stable over periods of tens of thousands of years. This observation is confirmed by Mary Leakey's work19 on the Oldowan technology associated with Homo habilis and by numerous other studies of the Early Palaeolithic period, between 2.5 million and 250,000 years ago.20 In contrast, a review of hunting and gathering technologies throughout the world over the last 50,000 years21 reveals extremely rapid change and great regional specialization. Why should the technologies of recent hunters and gatherers change so rapidly while those of our early hominid ancestors remained stable for periods of hundreds of thousands of years? To answer this question, we must consider the role of recent hunter/forager technologies in the context of their cultural systems. In such technologies, tools are classified and manipulated as abstract linguistic symbols. Their structure, use and interrelationships are thought about and consciously modified. In real life terms, this means that technology is easily altered in response to changing social and environmental requirements. In dealing with recent technologies, archaeologists commonly deal with two broad arenas of change: style and function.
Technological Function in Cultural and Biological Systems. By function, archaeologists mean to emphasize economic function, or the manner in which a tool is physically manipulated and used. Functional changes occur as technologies are tailored to economic and environmental requirements, including improvements in the technology itself which make it more efficient. The specific economic relationships between any human society and its environment change continually. As this happens, the individuals in the society manipulate these changing relationships in the form of abstract concepts, seeking ways to improve their situation by changing the nature of their cultural adaptation in small but significant ways. These changes are frequently reflected in the character of the technology itself, and are described by archaeologists as functional.
In communities of recent hunter/foragers, small-scale functional changes are occurring continually, while large-scale functional reintegrations of technology are more episodic, with intervening periods of stability ranging from a few hundred years to as much as ten thousand years. In analyzing the technological assemblages from Olorgesailie, Isaac fails to find any conclusive evidence for continual small-scale functional readjustments in Acheulean tool kits. Moreover, large-scale reorganizations of the technology do not occur, even over many tens of thousands of years, despite significant environmental changes in the Olorgesailie region. This suggests that technological functions are not being integrated culturally into the subsistence behavior of Homo erectus.
However, if we adopt the broader perspective gained by looking at the entire Lower Palaeolithic, it is quite obvious that at least one such functional reintegration of technology took place when Acheulean technology developed from Oldowan technology. If this large-scale reintegration of human technology depended on cultural behavior, then it is fair to question our interpretation of the Olorgesailie evidence, since that site was occupied 300,000 to 600,000 years after the emergence of Acheulean technology. Here the central question is a simple one. Does a large-scale technological reorganization involving basic subsistence activities require symbolic, cultural behavior? The answer is no. Innumerable species of insects, reptiles, birds, and mammals incorporate behaviors which involve and are dependent on technology. In many cases, these behavioral patterns are highly structured and controlled by genetic programming at the cellular level. In many mammals, however, such specific genetic controls give way to more flexible systems in which individuals are capable of learning a wide variety of technological, behavioral patterns within constrained limits set by the physiology and function of the cerebral cortex of the brain. These functions are controlled by complex genetic structures which we are very far from understanding. It is clear, however, that changes in the physiology and function of the brain must, at first, have involved increasing the ability to integrate more complex technological behavior in routine subsistence activities through the processes of natural genetic selection characteristic of biological evolution. We know that brain size in the hominid line changed rapidly and systematically between 3 million and 100,000 years ago, suggesting that this biological process was slow indeed. Since technology was first perceptibly integrated in this process some 2.5 million years ago, it is virtually certain that technological change was integrated into the biological process of natural selection long before culture, as we understand it, came into being. Potentially, then, technology at Olorgesailie during the Acheulean period some 450,000 years ago could conceivably be the product of a narrowly controlled biological system involving severe constraints on innovative behavior. Or, alternatively, we might already be dealing with symbolic cultural behavior in which the processes of innovation, as we understand them from modern cultural systems, played an important role.
How can we distinguish between these possibilities when viewing artifacts, the products of technological behavior, in the archaeological record? The key to this problem, as Isaac clearly points out (pp. 98-104), is measuring the rate and character of technological change. If technological change is integrated in a cultural system of behavior, minor functional readjustments will be continual and major functional reintegration of technology will be relatively frequent. Technology will become differentiated according to broad environmental needs reflecting regional dietary adaptations, variable climatic conditions, and diverging subsistence strategies. These variables will come to be reflected in regional culture areas.22 On the other hand, if technological change is integrated in a biological system of behavior, change will be slow and episodic,23 and individual technologies will be integrated over much larger geographic areas. These are precisely the characteristics of the Lower Palaeolithic in general and the technological series from Olorgesailie in particular. Hence, we must conclude that cultural behavior does not appear in the hominid line until sometime after the end of the Lower Palaeolithic, some 150,00~200,000 years ago. This conclusion can be verified by studying the stylistic component of technology.
Style as a Property of Culture. In contrast to functional change, stylistic changes involve characteristics of the technology which have no obvious, direct economic function. In recent human societies of all types, stylistic changes in technology are closely bound up with social values, aesthetics, ideology, and the dynamics of craft traditions. Such characteristics tend to change continuously along complex unidirectional or cyclical vectors.24 For this reason, they form the principal basis for the seriation of archaeological materials into periods of short duration. Close comparison of these periods reveals many of the internal dynamics of social change.25
Unlike functional changes in technology, which may be based in whole or in part on biological processes of evolution and adaptation, stylistic changes exist solely in the domain of cultural adaptation. The reasons for this are clear. The recognition and manipulation of style in the manufacture of any technology requires symbolic investment in every artifact which is made. Tools must be manipulated in a complex matrix of abstract, symbolic concepts so that they can be invested with social and ideological meanings quite apart from their everyday economic functions. In modern human societies, this matrix of style concepts is fully integrated with and interdependent on the beliefs and concepts structuring social institutions, cultural values, and the roles of individuals in society.26 Together, these are manipulated, discussed, and passed by means of language from generation to generation as the traditional heritage of a people. Such traditions are dynamic and plastic because they are based on our ability to employ and manipulate symbols in the process of innovation.27 Even the most minor fluxes within the social environment, including the ever-changing juxtaposition of individuals with different levels and kinds of symbolic ability, will create the intellectual tension and interest which impels all humans to manipulate their symbolic environment, changing it in subtle ways. Because many of these changes are reflected in the modification of stylistic attributes on individual artifacts, the analysis of style in technology is an extremely sensitive indicator of the creation and manipulation of symbolic matrices in the human mind. The presence of stylistic change in early hominid technologies would demonstrate that such matrices were being employed and communicated using language. They would demonstrate the presence of culture.
Isaac speculates that the highly individual character of many of the Olorgesailie assemblages may reflect the styles developed by individual bands of Homo erectus using the area over a period of thousands of years (p. 211). This seems highly unlikely for three reasons.
First, the creation and maintenance of a series of interrelated technological styles involves the transmission of knowledge, attitudes, values, and goals from generation to generation through the use of language. Changes in such a system are systematic and directional in nature. These kinds of directional stylistic changes link individual archaeological assemblages of slightly different age to one another in any given geographic region. The unique qualities of the Olorgesailie assemblages are not tied together by any systematic tendencies through time. They are random and do not suggest systematic stylistic change.
Second, we know from the size and structure of Acheulean base camps that hominid groups were small, usually less than thirty individuals. Such groups could not survive in a fixed territory with stable resources for more than a few generations. In order to insure the reproductive continuity of such a small group, the necessary proportion of adult fertile women must be maintained by exchanging individuals between adjoining groups. Relying on ethnographic information for modern hunter/foragers,28 Isaac speculates that complex social rules governing the social interaction of adjacent groups may extend even back as far as the Acheulean period (pp. 9596). If this were so, then technological styles would be shared widely by groups in locales of high intercommunication and uniform functional adaptations in the technology. Such local and regional stylistic integration of technology is typical among recent hunter/foragers, but apparently absent at Olorgesailie and other Lower Palaeolithic sites.
Third, larger-scale, systematic, unique geographic variation among sites of widely varying ages does, however, occur. Despite the flavor of individual local assemblages, a recent study of Acheulean sites from the eastern and western rifts in eastern Africa shows that there is a direct correlation between overall similarity and geographic distance among sites separated by tens of thousands of years in time, periods much too long to successfully maintain closely related styles in adjacent regions.29 Such variation makes perfect sense, however, in terms of biologically controlled systems of technological behavior. Such behavior will vary regionally in systematic ways over long periods of time because of differences in the underlying gene pools which are stable over larger areas and much longer periods than specific cultural adaptations.
If the highly idiosyncratic nature of individual Acheulean assemblages from Olorgesailie cannot be accounted for by the development and maintenance of local styles, then how is it produced? If no cultural content is assumed to be present in Acheulean technological behavior, it is easy to see how such stochastic variation can be built into the system. In such a biologically controlled system, the bulk of technological learning would be imitative and a substantial portion of it would be concentrated in peer groups or cohorts involved in technological activities with one another from day to day. In small groups, such as those which typified the Lower Palaeolithic, the idiosyncratic motor habits and design modes of individuals with forceful personalities could easily come to dominate the details of many artifacts produced by the group over short periods of time, spanning one to three generations. Such styles would shift erratically, reflecting the recombination of genetic structures from generation to generation, while slowly accreted, systematic, directional changes would continue to be incorporated in response to selective pressures. Thus the random variation we see in Lower Palaeolithic technologies reflects the expected norm of reaction, the pool of recombinant genetic variability, which is drawn upon in periods of selective stress in hominid populations.
The Evolution of Technological Behavior. This line of reasoning suggests that periods of reintegration of human technology must also mark periods of selective stress and behavioral evolution in the hominid line. Such periods of reintegration occur (1) 2.5 million years ago with the appearance of flaked stone tool technology (Oldowan technology), (2) during the 200,000-400,000 year period around a million years ago when Acheulean technology appears, (3) at the end of the Lower Palaeolithic, between 250,000 and 150,000 years ago, when Acheulean technology evolves into a series of large-scale regional geographic technologies characteristic of the Middle Palaeolithic, and (4) when regional Middle Palaeolithic technologies evolve into smaller-scale culture areas around 50,000 years ago. These periods of technological reintegration span and delineate the period during which fossil evidence indicates the brain was evolving,30 together with our ability for vocal communication.3l Within this framework, the living sites from Olorgesailie span a considerable portion of the long period of stability identified with Acheulean technology. Since the processes of change which bring the Acheulean into existence and eventually terminate it are episodic, it is possible to compare the rate of technological change with the rate of biological change in the central nervous system, measured by brain size, in order to determine the relative importance of technology in the process of human evolution.
Many authorities have maintained that technology itself, or hunting as a subsistence strategy based on technology, was a prime mover in human evolution and the emergence of cultural behavior in the hominid line.32 If this is indeed so, then expansion of the human brain and changes in its complexity should be episodic, correlating closely with the periods of technological integration cited above. Though not conclusive, the fossil evidence at hand suggests that the evolution of brain size was continuous, following an exponential curve between 3 million and 50,000 years ago.33 If this reconstruction is correct, what selective pressures were causing the brain to expand during periods of prolonged technological stability, such as the Acheulean? Certainly not technological or interdependent subsistence adaptations.
In a recent, thought-provoking article, Isaac has suggested that food sharing may have been an important behavioral component underlying this process.34 I would like to enlarge on this line of reasoning by arguing that food sharing was only one of several behavioral domains in which sexual selection operated to produce ever more complex systems of social interaction. My reasoning is as follows. Behavioral students of nonhuman primates demonstrate that monkeys and apes living in groups in savannah and open savannah woodlands, such as those occupied by our early hominid ancestors, employ complex dominance hierarchies to maintain social control and deal with external threats, such as predators. It is likely that our earliest hominid ancestors utilized similar hierarchies, prior to 3 million years ago. The emergence of Oldowan technology and the concomitant shift towards hunting could not have occurred unless such an hierarchy was drastically modified to accommodate food sharing, the division of labor by age and sex, and the daily dispersal and geographic isolation of group activities. These changes produce a greater variety of interpersonal relationships and require individuals to manipulate their social surroundings in more complex ways as the structure of the group changes in a diurnal cycle.
If men are given sexual access to fertile women because they manipulate their social environments with greater skill, then sexual selection for such skills will be maintained indefinitely. Since these skills involve more complex decisions, forethought, memory, and the ability to predict the consequences of subtle psychological byplay, they would naturally select for larger and more complex forebrains. The development of such social skills is a prerequisite to hunting as an adaptive strategy in the hominid line and explains why the initial transition to a hunting/foraging subsistence strategy required such a long period of adaptation in the savannah. Moreover, it also explains how brain size could continue to increase in hominid populations during periods in which there is no evidence for stress in technological or subsistence domains per se. The larger and more complex forebrain, in its turn, made possible much of the episodic change we observe in technology and subsistence by providing greater flexibility and range in closely related behavioral responses. In other words, it provided the staging area and proving grounds for the evolution of technological behavior.
Using this model, the emergence of the Acheulean begins to make a great deal more sense. Evidence from Olduvai Gorge35 and East Turkana36 suggests that the Acheulean was the outcome of 200,000 to 400,000 years of evolution during which Homo habilis evolved into Homo erectus, and two separate genera of Australopithicines became extinct. Competition between these three groups of hominids, as Homo habilis expanded into the ecological niches occupied by the Australopithecines, may have provided the needed selective pressure on systems of technological and subsistence behavior, while social interaction provided the competitive arena in which new adaptations were tested and integrated into the increasingly more complex patterns of social behavior of our hominid ancestors.
Numerous other problems of change and stability in prehistoric technology can be approached in a rewarding fashion when we recognize, fully and explicitly, the biological component of ancient human behavior. The significance of the chopper/chopping tool complex in Southeast Asia, technological deviance at the ecological limits of hominid range, the origin and development of Middle Palaeolithic technologies, and technical variability in the Mousterian technology are all examples of phenomena which can be explained more credibly from this point of view.
The Transition to Cultural Behavior. A close analysis of technological variation in technologies of different ages suggests that technology was not fully integrated into cultural patterns of behavior completely dependent on the symbolic transmission of tradition through language until the end of the Middle Palaeolithic period, between 50,000 and 75,000 years ago. It is the Middle Palaeolithic period which corresponds with the final transition to patterns of cultural behavior. The character of this transition period is still poorly understood and should provide a fascinating arena for further research and discovery.
Ethnographic and Ethological Analogy
In interpreting the remains from ancient archaeological sites such as those at Olorgesailie, prehistorians often rely on models based in whole or in part on observation of behavioral patterns in modern hunter/forager communities or groups of nonhuman primates which have been studied in the wild.37 These models are used as analogs to reason from fragmentary archaeological remains to more detailed reconstructions of hominid behavior. In interpreting the archaeological remains from Olorgesailie, Isaac frequently cites ethnographic analogs,38 and in commenting on the significance of his research in this review I have utilized both ethological and ethnographic analogs. Such analogies tend to depict our hominid ancestors as absolutely cultural or noncultural in their behavioral patterns. Each of these views is equally erroneous. The archaeological evidence demonstrates beyond all doubt that early hominid adaptations and behavioral patterns were significantly different from those of any living species of primate, human or nonhuman. The reliance on technological adaptations, the incorporation of hunting in subsistence strategies and food sharing are uniquely human characteristics beyond the scope of behavioral adaptations observed in monkeys and apes. Thus, over reliance on ethological models portrays early hominid behavior in much too simplistic a fashion. Likewise, the limited ecological range, technological stability, and ponderous adaptive responses observed in early hominid populations is far less complex than the simplest adaptive responses and histories recorded among recent human societies. Heavy reliance on these ethnographic models, which is all too common these days, portrays hominid behavior as far more complex than it was in reality. Analogies of both kinds must be used with caution. At the bottom line, there must be solid archaeological data to take us beyond the uncertainties inherent in their facile assumptions. It is here that Isaac's exemplary work at Olorgesailie has its most basic and substantial meaning, for the information marshaled from this locality is of such high quality that it will be integrated and reintegrated into our changing understanding of the past long after the issues discussed here have ceased to be significant.
The Future of Olorgesailie
Archaeological sites are perishable. Archaeological excavation is therefore the art of systematic destruction, undertaken cautiously when there is a reasonable expectation that the knowledge so obtained will justify the expenditure of a particular portion of the resource base. Isaac's work at Olorgesailie has posed a series of highly significant questions about the character of hominid behavior and adaptations during the Middle Pleistocene. A number of these questions can still be fruitfully pursued at Olorgesailie. Of these, four seem of particular importance.
l ) The information from Olorgesailie would be made more precise and valuable if the sediments from which it came could be dated more accurately (pp. 24 25). Further geological reconnaissance and potassium/argon dating might help here, but the greatest potential lies in the use of the diatomaceous lake beds which are interstratified with the archaeological sites. The diatoms found in these sediments have exoskeletons of silica which may preserve fission tracks from the breakdown of radioactive trace elements such as uranium. When irradiated in a reactor, the delicate exoskeletons of diatoms are shattered, but if a suitable rigid mounting medium could be found, it might well prove possible to obtain accurate dates for the very heart of the archaeological succession at Olorgesailie, as well as many other sites of Pleistocene age. The issue of dating is important at Olorgesailie since it affects our perceptions of both short- and long-term technological change during the Acheulean. More precise dates would allow the more accurate measurement of change and stability, improving the quality of the data we already possess from Olorgesailie.
2) Isaac's quantitative analysis of the morphological field occupied by Acheulean tools needs to be repeated using other Acheulean assemblages. Systematic shifts in the modes within this field may allow us to measure rates of evolutionary change, regional divergence and gene flow in the behavioral and genetic systems underlying the manufacture and use of Acheulean technology. Once developed, such an analytical technique would prove fruitful in the analysis of early periods of technological stress and change, especially those at the beginning and end of the Acheulean period.
3) Recently, Isaac has turned his attention towards another long-standing problem in the interpretation of Palaeolithic artifact assemblages.39 Stone tools occur not just in the context of established home base, butchery, and quarry sites, but also as a thin, diffuse scatter between these sites. This scatter is thought to represent geographically unfocused, recurrent activities possibly associated with foraging. Preliminary analysis of such widely scattered surface finds dating from the Oldowan/Acheulean transition in East Turkana suggest that there may be significant differences in the tool kits used at home bases and those used in these more diffuse foraging activities. The excavated assemblages and miles of exposures at Olorgesailie form an ideal situation in which these patterns can be defined for the Acheulean proper. Assemblages collected from this diffuse scatter between the recognizable sites would also provide a set of valuable comparative data which could be used to interpret further the complex succession from Olorgesailie itself.
4) The significance of the analysis of short-term technological change in the Acheulean at Olorgesailie could be extended greatly if more living floors could be excavated, particularly ones with well preserved faunal remains. Such sites probably exist at Olorgesailie, but locating them will be a difficult and expensive chore. Fortunately, Isaac has established a close correlation between home bases and the preference for a sandy substrate such as that provided along ephemeral streams (pp. 8l-84). The sandy lenses left in the earth by such streams can be mapped using a suitable coring device and then sampled systematically with the aid of power equipment such as back hoes. Though expensive, such a program would be worthwhile because of the density of Acheulean sites at Olorgesailie and because of the great expense and time required duplicating the work already completed in Isaac's monumental analysis.
The dissertation, monograph, and thoughtful essays which have grown out of the Isaacs' work at Olorgesailie provide the modern paradigm for Lower Palaeolithic studies in Africa. They also constitute, in my opinion, a major turning point in our understanding of human evolution and the role which technology played in that still mysterious and fascinating process. All students of human history should find Isaac's work equally fascinating.
1 Glynn Ll. Isaac, "The Acheulean Site Complex at Olorgesailie, Kenya: A Contribution to the Interpretation of Middle Pleistocene Culture in East Africa.' (Ph.D. dissertation. Cambridge University, 1968).
2 Glynn Isaac, "The Diet of Early Man: Aspects of Archaeological Evidence from Lower and Middle Pleistocene Sites in East Africa," World Archaeology, 2 (1971), 278-298; "Chronology and Tempo of Cultural Change during the Pleistocene," in W. W. Bishop and J. A. Miller, eds., Calibration of Hominid Evolution (Edinburgh, 1972), 381 430; "Early Phases of Human Behavior: Models in Lower Palaeolithic Archaeology," in D. L. Clarke, ed., Models in Archaeology (London, 1972),167-199; "Identification of Cultural Entities in the Middle Pleistocene" in H. J. Hugot, ed., Congress Panafricain de Prehistoire, Dakar 1967, Actes de 6e Session (Paris, 1972), 556-562; "Middle Pleistocene Stratigraphy, and Cultural Patterns in East Africa," in K. W. Butzer and G. Isaac, eds., After the Australopithecines: Stratigraphy, Ecology and Culture Change in the Middle Pleistocene (The Hague, 1975), 495-542. Also of interest is Isaac's more recent popular article, "The Food-Sharing Behavior of Protohuman Hominids," Scientific American, 238 4 (1978), 90 108.
3 For example, Isaac, Olorgesailie, 98,101, 211.
4 For example, J. B. Birdsell, Human Evolution: An Introduction to the New Physical Anthropology, 2nd ed. (Chicago, 1975), and Chester S. Chard, Man in Prehistory (New York, 1969)
5 For example, Chard, Man in Prehistory, chs. 6-10, and J. Desmond Clark, The Prehistory of Africa (New York, 1970), ch. 1.
6 See the discussion of sexual division of labor by Roger Pearson, Introduction to Anthropology (New York, 1974), 90 91; and the discussion of cannibalism by William A. Hsviland, Anthropology (New York, 1974), 123. This problem is brought into particularly clear focus if we compare the interpretations of the baboon remains from Olorgesailie made by Isaac in Olorgesailie, 51-57, and by Bernard G. Campbell in Humankind Emerging (New York, 1976), 25 1-25 2. Campbell suggests that more than forty giant baboons were killed in a single, well-organized night-time hunt, being butchered and eaten where they fell. Isaac builds a pattern of evidence which suggests the baboons were hunted repeatedly, killed in small numbers in each hunt, and returned to a home base, where they were butchered and eaten. Since the baboon remains provide the earliest known evidence for hunting practices as complex as those which Campbell envisions, these differences in interpretation are critical to our assessment of the evolution of human economic and social behavior.
7 For example, David Pilbeam, The Ascent of Man: An Introduction to Human Evolution (New York, 1972).
8 Those unfamiliar with the process by which stone tools are manufactured should consider viewing one of the many motion pictures which depict stone flaking. Films such as The Flint Worker (lnformational Materials Incorporated, Burbank. Ca.), featuring Don Crabtree, are widely available and depict the making of common Acheulean tools.
9 Isimila, Kalambo Falls, Olduvai Gorge. See Clark, Prehistory of Africa, for an overview of these.
10 For example, John E. Pfeiffer, The Emergence of Man, 2nd ed. (New York, 1972), on the relationship between hunting and technology in human evolution.
11 Jane B. Lancaster, "On the Evolution of Tool-Using Behavior," American Anthropologist, 70(1968),56 66, was one of the first to question the traditional views.
12 See also Isaac, "Chronology and Tempo of Cultural Change"; "Early Phases of Human Behavior"; and "Identification of Cultural Entities."
13 This statement seems curiously at odds with many of the detailed interpretations in his monograph.
14 Homer G. Barnet, Innovation: The Basis of Cultural Change (New York, 195 3 ).
15 For example, Pilbeam, Ascent of Man.
16 Lancaster, "Evolution of Tool-Using Behavior."
17 R. V. S. Wright, "Imitative Learning of a Flaked Stone Technology: The Case of an Orangutan," in S. L. Washburn and E. R. McCown, eds., Human Evolution: Biosocial Perspectives (Menlo Park, 1978),115-138.
18 For example, Pfeiffer, Emergence of Man.
19 Mary D. Leakey, Olduvai Gorge: Excavations in Beds I and 11, 196~1963 (London, 197 1).
20 Reviewed in Clark, Prehistory of Africa.
21 Reviewed in Grahame Clark, World Prehistory in New Perspective, 3rd ed. (London, 1977).
22 For example, Alfred L. Kroeber, "Cultural and Natural Areas of North America," Publications in American Archaeology and Ethnology, 38(1939),1-242; and Clark, World Prehistory.
23 Steven J. Gould, Ontogony and Phylogony(Cambridge, Ma., 1977).
24 For example, Kroeber, Anthropology: Cultural Patterns and Processes (New York, 1963).
25 For example, James Deetz, The Dynamics of Stylistic Change in Arikara Ceramics (Urbana, 1965).
26 Barnett, Innovation.
27 Leslie A. White, The Science of Culture (New York, 1949).
28 R. C. Owen, "The Patrilocal Band: A Linguistically and Culturally Hybrid Social Unit," American Anthropologist, 67 (1965), 675-690.
29 J. Desmond Clark and Hiro Kurashina, "New Plio-Pleistocene Archaeological Occurrences from the Plain of Gadeb, Upper Webi Shebele Basin, Ethiopia, and a Statistical Comparison of the Gadeb Sites with Other Early Stone Age Assemblages," in Union Internationale des Sciences Prehistoriques et Protohistoriques, IX~ Congress, Colloque V, The Earlier Industries of Africa, directed by J. Desmond Clark and Glynn Ll. Isaac (Nice, 1976).
30 Pilbeam, Ascent of Man.
3I Philip Lieberman, On the Origins of Language: An Introduction to the Evolution of Human Speech (New York, 1975)
32 For example, compare Pfeiffer, Emergence of Man, and Isaac, ''Food Sharing Behavior. '
33 Pilbeam, Ascent of Man, 71-82, Fig. 40.
34 1saac, "Food-Sharing Behavior."
35 Leakey, Olduvai Gorge, III.
36 J. W. K. Harris and Glynn Ll. Isaac, The Karari Industry (in press); Richard Leakey and Roger Lewin, Origins (New York, 1977), 103.
37 Robert Acher, "Analogy in Archaeological Interpretation," Southwestern Journal of Anthropology, 17 (1961), 317-321.
38 For example, Isaac, Olorgesailie, 87-89,91,96-97,211-212.
39 See Ibid, 8~81, and Isaac, The Scatter Between the Patches (in press).