Evolution of Tool Use

Chapter 14

Evolution of Tool Use Nicholas Toth, Kathy Schick The Stone Age Institute, Gosport, IN, USA; Indiana University, Bloomington, IN, USA

SYNOPSIS The profound reliance of the human species on tools for its survival and adaptation is unique in the animal world. Prehistoric evidence for tool use as an adaptive strategy in human evolution extends back at least 3.3 million years, when stone tools began to be found at prehistoric sites in Africa in regions containing fossils of early bipedal ancestors. Archaeological research documents a long period of dependence on stone tools through a succession of ancestral species and a gradually accelerating pace of technological change, with emergence of large complex societies and rapid technological proliferation only within the past 10,000 years.

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Humans and many of our extinct ancestral species have been coevolving with tools and technology for millions of years. In the kingdom Animalia, our species (anatomically modern Homo sapiens) is the consummate toolmaker and tool user; our very existence is dependent on our use of tools. Humans are unique in the history of life on Earth in their ability to adapt to a large and diverse range of environments and shape their world through the use of tools and technological systems. From its origins millions of years ago, the human lineage has greatly expanded its range, increased its population size, and increasingly affected global environmental and climatic patterns at an alarming and perilous pace. Understanding how we arrived at the modern human condition is the task not only of historians but of palaeoanthropologists that discover, study, and interpret the prehistoric fossil, archaeological, and palaeoenvironmental evidence. The coevolution of technology and human biology has been an important focus of palaeoanthropology. This process has been dubbed the “biocultural feedback system” by noted anthropologist Sherwood Washburn (1960), “gene–culture coevolution” by sociobiologists Alan Lumsden and E.O Wilson (1983), and “technoorganic evolution” by the authors of this chapter (Schick and Toth, 1993). Over a century-and-a-half palaeoanthropological investigations have taken place since Charles Darwin published his Origin of Species by Means of Natural Selection in 1859. Thousands of hominin fossils representing hundreds of individuals and dozens of taxa are now documented since the last common ancestor of chimpanzee and humans, perhaps 8 million years ago (mya); the archaeological record for tools and technology is documented for the past 3.3 million years. For overviews of the human evolutionary record, see the preceding seven chapters by Sept, Hunt, Ward, Simpson, Ahern, and Holt in the current volume. Also see, for example, Boyd and Silk (2012), Broadfield et al. (2010), Cartmill and Smith (2009), Delson et al. (2000), Foley and Lewin (2004), Henke and Tattersall (2007), Johanson and Edgar (2006), Klein (2009), Stringer and Andrews (2005), Roberts (2011), Scarre (2013), Schick and Toth (1993), Tattersall (2008), and Zimmer (2005).

EVOLVING HOMININ FORMS AND TECHNOLOGIES: A REVIEW The backdrop for the evolution of technology includes a large number of evolving hominin species that predate the emergence of tools at 3.3 mya, and then continue to evolve and diversify over the past 3.3 million years of technological evolution (Table 1). (Further descriptions of technologies noted in this section will be provided in later sections of this chapter.) Between 7 and

4 mya, a number of hominin forms have been recovered from deposits in Africa that researchers consider to be closely related to our evolving lineage. These involve a number of species (Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus kadabba, Ardipithecus ramidis) that appear to be apelike in many ways, but that show also some traits indicating evolutionary characteristics that may be ancestral to later hominins (see chapter by Hunt on Earliest Hominins). These are sometimes called the “pre-australopithecines,” as they show possible relationships to the australopithecines that emerge approximately 4 mya. The australopithecines, the various fossil species placed in the genus Australopithecus, have a span of almost 3 million years, and can be grouped by time into earlier and later forms (see chapter by Ward). The earlier australopithecines emerge in the fossil record a little more than 4 mya and continue evolving and diversifying until at least 2.5 mya. They are first evident in East Africa and then also in South Africa. Taxa include Australopithecus anamensis, Australopithecus afarensis, Australopithecus garhi, and Australopithecus africanus. Another genus, Kenyanthropus, dating to 3.5 mya, has also been proposed by some researchers (Leakey et al., 2001). The later australopithecines, sometimes put into the genus Paranthropus, forms with robust jaws and large cheek teeth, coexisted with evolving forms of Homo in both East and South Africa until their extinction between 1.5 and 1.0 mya. Our ancestral lineage almost certainly stems from the earlier australopithecines, with A. afarensis, a small-brained hominin with a well-developed adaptation to bipedal walking (Johanson, 2004; Johanson and Edgar, 2006; Tattersall, 2008), widely considered to be ancestral to later hominins. Very late in this span of early australopithecines, A. garhi (Asfaw et al., 1999), a still small-brained but nonrobust form, is found in deposits of similar age to early stone tools at Gona, Ethiopia (Semaw et al., 1997; Semaw, 2006), and in the same region, and so can be considered a candidate for the earliest toolmaker. There are also fossils in the Afar region of Ethiopia attributed to early Homo, including a mandible dating to 2.8 mya in the Ledi-Geraru region (Villmoare et al., 2015) and a fossil maxilla dated to 2.3 mya in the Hadar region (Kimbel et al., 1996). We currently do not have information regarding the morphology of the brain case or the cranial capacity of these fossils, but similar fossils would also be potential candidates for the toolmakers at Gona. The robust australopithecine, A. (P.) aethiopicus (Kimbel et al., 1988), is also roughly contemporary with early stone tools, but would appear to be a less likely candidate for the maker of the first stone tools, as its massive chewing apparatus would indicate a biological adaptation with a strong emphasis on masticating hard,

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TABLE 1  Hominin Forms in the Last 7 Million Years and Contemporary or Associated Technologies Hominin Group

Species

Approximate Age

Associated/Contemporary Technological Tradition

Country/Region

PreAustralopithecines

Sahelonthropus tchadensis

7 mya

None known

Chad (Central Africa)

Orrorin tugenensis

6 mya

None known

Kenya (East Africa)

Ardipithecus kadabba

5.6 mya

None known

Ethiopia (East Africa)

Ardipithecus ramidus

4.4 mya

None known

Ethiopia (East Africa)

Australopithecus anamensis

4.2–3.9 mya

None known

Kenya and Ethiopia (East Africa)

Australopithecus afarensis

3.9–2.9 mya

(Earliest stone tools, Lomekwi, Kenya)

Ethiopia and Tanzania (East Africa)

Australopithecus africanus

3–2 mya

None known

South Africa

Australopithecus garhi

2.6 mya

(Early Oldowan)

Ethiopia (East Africa)

Australopithecus aethiopicus

2.5 mya

(Early Oldowan)

Ethiopia and Kenya (East Africa)

Australopithecus boisei

2.3–1.2 mya

(Oldowan/Acheulean)

Ethiopia, Kenya, Tanzania (East Africa)

Australopithecus robustus

2–1.2 mya

(Oldowan/Acheulean)

South Africa

Homo sp.

2.3–2 mya

Early Oldowan

East Africa

Homo rudolfensis

1.9 mya

Oldowan

Kenya (East Africa)

Homo habilis

2.0–1.4 mya

Oldowan

East Africa, South Africa

Homo ergaster/erectus

1.8 mya–200 kya

Oldowan/Acheulean

Africa, Eurasia

Homo heidelbergensis

600–250 kya

Later Acheulean/nonAcheulean

Africa, Eurasia

Homo neandertalensis

300–30 kya

Middle Palaeolithic

Eurasia

Homo helmei

260 kya

Middle Stone Age

South Africa

Early Homo sapiens

160–50 kya

Middle Palaeolithic/Middle Stone Age

Africa, Eurasia

Later Homo sapiens

50 kya to present

Upper Palaeolithic/Later Stone Age, Mesolithic, Neolithic, etc.

Africa, Eurasia, Australia, New Guinea, Americas

Earlier Australopithecines

Later Australopithecines

Early Homo

Later Homo

presumably lower energy foodstuffs. The later robust australopithecines in East Africa (A. (P.) boisei) and South Africa (A. (P.) robustus) carry on this biological adaptation until their ultimate extinction between 1.5 and 1 mya (Grine, 1988). Starting about 2.8 mya, fossil remains have been found that have been placed in our genus, Homo, largely based on dental characteristics (see chapter by Simpson). The earliest fossils do not include evidence of cranial volume, so at present it is not known when the dramatic brain expansion evidence in the Homo lineage actually began. Starting approximately 2 mya, forms of Homo showing brain

expansion appear in the fossil record in Africa (Homo rudolfensis and Homo habilis) and are presumed to be toolmakers responsible for the many Oldowan sites that have been found (Schick and Toth, 2006; Toth and Schick, 2010). By approximately 1.8 mya, a larger bodied and larger brained form appears in Africa, Homo erectus (also called Homo ergaster) and at the same time an evident expansion out of Africa is evidenced by fossils at the site of Dmanisi in the Republic of Georgia (Lordkipanidze et al., 2013). The presence of a large range of variation among the five hominin crania found at the Dmanisi site, in a single deposit and contemporary with one another,

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would indicate that hominins in this phase of human evolution constituted a quite variable species, and thus splitting Homo fossil samples into separate species based on morphological characteristics may not always be justifiable. Homo erectus is associated with both Oldowan and Acheulean sites in Africa and much of Eurasia, although the Acheulean is largely absent from eastern Europe through central and eastern Asia. As multiple hominin species are contemporary with early Oldowan as well as Acheulean industries, both in East Africa and South Africa, the question naturally arises as to which species was or, perhaps, were responsible for early stone toolmaking. It cannot be ruled out, of course, that robust australopithecines made stone tools, at least on occasion, as they were present in the same regions during the time that early stone tool sites were produced. But, in addition to the noted emphasis among the robust australopithecines on a biological adaptation involving heavy mastication, stone tool sites continue on in time after their extinction and become even more numerous and widespread, as do evolving species of Homo. Thus, it is certain that the adaptation of Homo had incorporated a technological adaptation into its evolutionary strategy, and it would appear likely that Homo species were largely responsible for early stone tool industries. In the past million years, Homo has undergone fairly rapid and dramatic evolutionary changes along with an accelerating pace of technological change. Between 1 mya and a few hundred thousand years ago, H. erectus evolved into a larger brained hominin with robust features of the cranium and face (see chapter by Simpson). In Africa, these larger brained forms included Homo heidelbergensis, Homo helmei (these two taxa were sometimes previously assigned to “archaic Homo sapiens”), and early anatomically modern humans (see chapter by Ahern). In Europe, these forms included H. heidelbergensis and Homo neandertalensis (Neanderthals). In East Asia, these forms are sometimes assigned to H. heidelbergensis and some more recent archaic form of Homo (species often not named). This later evolution of the genus Homo witnessed the technological transition from the later Acheulean to the Middle Palaeolithic (Middle Stone Age in sub-Saharan Africa) and then the Upper Palaeolithic (Later Stone Age in sub-Saharan Africa). (Note that the traditional British spelling of “Palaeolithic” is used throughout this chapter.) By at least 160,000 years ago, fossils have been found in parts of Africa and the Near East that are considered to be early anatomically modern H. sapiens (AMHS), or early H. sapiens (see chapter by Holt). Early H. sapiens were generally associated with Middle Palaeolithic and Middle Stone Age technologies. Starting between 50,000 and 40,000 years ago, H. sapiens became much more widespread in the Old World, spreading through much of

Eurasia (and coexisting with Neanderthals for some time in some regions), into the Pacific to Australia and ultimately to the Americas, and by this time are associated with Upper Palaeolithic or Later Stone Age technologies during the latter part of the Pleistocene. The emergence of food production, metalworking, complex societies, and escalating technological change are recent phenomena in our evolution (Scarre, 2013), all produced by modern H. sapiens since the end of the last Ice Age 10,000 to 12,000 years ago.

TOOLS IN THE ANIMAL WORLD Although the definition of a “tool” may vary, in behavioral studies it usually means that an organism takes an extrasomatic object (not part of one’s biology) and employs it toward some end (Schick and Toth, 1993; Shumaker et al., 2011). By this definition, a bird using a twig to probe for insects is an example of tool use, whereas a spider spinning a web (using its own biological repertoire) is not. An “artifact,” in archaeological terminology, is an object that has been modified by a human or proto-human, whether it has been used or not. Waste flakes from stone tool manufacture, for example, are artifacts. A range of animals are known to use tools in the wild. Interestingly, the wide range of animal species with tool-using behavior does not appear to correlate well with evolutionary history or neurological complexity, ranging from invertebrates such as digger wasps and octopus to fish, amphibians, reptiles, birds, nonprimate mammals, and primates (Shumaker et al., 2011; Sanz et al., 2013). In nonprimate species it is likely that these tool-using behaviors are “instinctive” rather than learned, are common to the species, and have foundations in the genetics of the species. In primates, however, many instances of tool-related behaviors have been documented in a number of species that show good evidence of having been learned rather that innate and to be shared through learning within the primate group. Such acquired tool-using and toolmaking behavior has been documented among some monkeys such as capuchins (Shumaker et al., 2011), but is observable more typically among apes, especially chimpanzees.

CHIMPANZEE TOOL USE AS A MODEL FOR EARLY HOMININS Chimpanzees have the richest tool repertoire of any nonhuman animal, and these tool behaviors are learned, often from infants watching their mothers and then going through an apprenticeship of trial and error until the tool behavior is mastered (McGrew, 1992, 2004). This includes termite and

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ant fishing with carefully shaped twigs, nut cracking with wood or stone hammers and anvils, and making sponges out of chewed leaves to collect water or for cleaning. Wild chimpanzees in West and East Africa have been documented to have over three dozen cultural traits, many involving tool use (Whiten et al., 1999). Interestingly, these cultural traits demonstrate significant geographical clustering, so that chimpanzee groups situated closer to one another share more cultural traits, with the number of shared traits decreasing significantly among groups at greater distances from one another (Toth and Schick, 2009b; Whiten et al., 2009). This pattern of geographical clustering of shared cultural traits among chimpanzee groups may serve as a model for early hominin groups, such that geographic patterning in technological characteristics might be expected among groups in closer proximity to one another. As our closest living relatives, the chimpanzees, show a diversity of tool-using and even sometimes toolmaking behaviors in the wild, it might be considered very likely that early hominin ancestors also utilized a variety of other materials before the prehistoric inception of stone tool manufacture and use. It is quite possible, or even likely in view of tool behaviors among chimpanzees, that before the advent of stone tools our ancestors also probed and manipulated materials in their environment with a variety of tools in materials other than stone, particularly in order to procure food or water. Unfortunately, materials such as wood, leaves, or bark that might readily be used or fashioned as tools are readily destroyed by natural forces, and so tools in materials other than stone would tend to be perishable and not likely preserved in the ancient prehistoric record. Thus, the beginning of a verified, documented record of tool use in the human lineage begins with the invention of flaked and battered stone tools. In an experimental setting, modern bonobos (“pygmy chimpanzees”) have learned to make and use flaked stone tools (Figure 1) and produce the rudiments of an Oldowanlike technology consisting of battered hammerstones, cobble cores, and flakes and fragments (Schick et al., 1999; Toth et al., 2006). These artifacts, however, do not show the level of skill and dexterity seen in the earliest archaeological sites (discussed below).

THE EARLIEST KNOWN STONE TOOLS The earliest known stone tools are found from sites in the Great Rift Valley of East Africa. Although there are claims of cut marks from stone tools on 3.4 million-year-old animal bones from the site of Dikika in Ethiopia (McPherron et al., 2010), there are no known stone artifacts from this site, and it is possible that these marks were, in fact, tooth marks created by crocodiles (Njau, 2012), whose teeth are numerous at this locality.

FIGURE 1  Kanzi, a bonobo or “pygmy chimpanzee” (Pan paniscus), has learned to flake stone, producing Oldowan-like artifacts including battered hammerstones, simple cobble cores, and sharp-edged flakes and fragments.

At present, the earliest probable claim for stone artifacts is at Lomekwi 3, West Turkana, Kenya (Harmand et al., 2015a,b; Balter, 2015). They are found in a geological horizon believed to be 3.3 million years old based on paleomagnetic studies. The artifacts, simple cores, flakes, and fragments, are made on large lava cobbles, with 20 artifacts reported in situ and another 130 pieces from the surface. The next earliest documented and well-dated artifacts consist of stone tools from sites dated to between 2.6 and 2.5 mya found at the locality of Gona in Ethiopia in the Afar Rift (Semaw, 2006; Semaw et al., 1997; Toth et al., 2006). These sites mark the beginnings of what is called the Palaeolithic, or “Old Stone Age,” the period of human cultural development in which stone tools constituted the preeminent components of the known tool repertoire. However, whether these very early archaeological occurrences represent the beginnings of a continuous stone tool tradition only sporadically sampled in the prehistoric record, or whether these represent early, intermittent experiments in stone knapping without the establishment of a long-term tradition (i.e., “flashes in the pan”), is not known at this time.

THE OLDOWAN (EARLIER LOWER PALAEOLITHIC/EARLY STONE AGE) The earliest stone tools are categorized as the “Oldowan,” a tool industry named after the famous site of Olduvai Gorge in Tanzania (Hovers and Braun, 2009; Isaac, 1990;

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FIGURE 2  Controlled stone fracture (conchoidal fracture), showing a battered hammerstone, a core, and a flake.

Klein, 2009; Leakey, 1936, 1971; Schick and Toth, 1993, 2006, 2009; Toth, 1985; Toth and Schick, 2006, 2009a, 2009b, 2013). Starting approximately 2.3 mya, Oldowan sites become more numerous and widespread on the African continent, with the first evidence in Eurasia by c. 1.85 mya. Besides the earlier sites noted above (Lomekwi 3 and Gona), other major Oldowan sites include Hadar, Ethiopia (Kimbel et al., 1996), the Omo Valley, Ethiopia (Howell et al., 1987), West Turkana, Nachukui Formation, Kenya (Roche et al., 1999), Kanjera, Kenya (Plummer et al., 1999), East Turkana (Koobi Fora), Kenya (Isaac, 1997), Olduvai Gorge, Tanzania (Leakey, 1971)

(all of the above in the East African Rift), Sterkfontein (Kuman, 1994) and Swartkrans (Clark, 1991) in South Africa, Ain Hanech and El-Kherba in Algeria (Sahnouni, 2006), and Dmanisi in the Republic of Georgia (Ferring et al., 2011). Oldowan tools consist primarily of cobbles and chunks of stone that have been deliberately modified by percussive flaking, that is, hitting one rock forcefully against another and striking off stone flakes. Such artifacts typically exhibit evidence of deliberate, patterned conchoidal fracture induced through repeated sharp, percussive blows of one rock against another (Figure 2).

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FIGURE 3  A range of Oldowan artifact forms, including a battered hammerstone, cores (chopper, discoid, polyhedron, heavy-duty scraper), flake, and retouched flake scraper.

Common elements of Oldowan stone tool assemblages include cores (pieces of stone that have been fractured through forceful blows with another stone), flakes (the often very sharp pieces of stone struck from these cores), and sometimes battered hammerstones that had been used to flake the cores (Figure 3). Archaeologists have over the years developed a number of classification schemes to characterize the components of early stone technologies (Schick and Toth, 2006), usually employing terms that describe the shapes of the cores as well as possible functional qualities they might have had. Thus, such terms such as “chopper,” “discoid,” “polyhedron,” and “core scraper” are often employed to describe cores in early

stone tool assemblages. Experiments have demonstrated that all of the major tool categories can be produced as a by-product of removing stone flakes from cores, with the resultant shape influenced largely by a combination of the initial shape of the stone being flaked and how extensively the core was flaked (Toth, 1985). Thus, it is uncertain that early stone tool makers were deliberately producing cores with desired, targeted shapes, as they may well have been largely focused on producing quantities of flakes from stone cores. The Oldowan is also characterized by having retouched flakes (flakes chipped on their edge to resharpen or shape them), such as “light duty scrapers” and “awls.” These retouched forms become more common as the Oldowan progresses.

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Although for many years, an emphasis had been placed by archaeologists on the stone cores as the primarily tools within early stone assemblages, experimental archaeological studies have demonstrated that the flakes struck off from such cores also have superb utility as cutting tools (Toth, 1985). Functional studies of stone tool replicas have demonstrated how the different types of early stone artifacts may have been used, for example, the usefulness of stone “choppers” to cut branches into digging sticks, probes, or spears. Such experiments have also highlighted how a simple stone flake, produced by striking a stone hammer against another stone, can produce a keenly sharp cutting edge. Such stone flakes would effectively have provided early hominins with stone knives that could be used to procure meat resources, either from scavenging carcasses on the landscape and/or from (likely smaller) animals they might have been able to hunt and kill. As early hominins were not biologically well adapted to the acquisition of meat resources, lacking the sharp teeth and claws of carnivores, such toolmaking behavior would have opened up a new and vital niche for them. It has been argued in the “expensive tissue hypothesis” that a dietary shift toward including more highquality diet components such as meat resources may have been a critical factor in allowing for the evolutionary expansion of the human brain (Aiello and Wheeler, 1995). According to this model, a higher quality diet would have allowed an evolutionary shift in the body’s energy budget, reducing energy demands for food processing in the gut and allowing a shift toward maintaining the very high energy demands of expanding brain tissue (see chapters by Little and Blumler, and Wiley in the current volume). Thus, stone tools could have been a critical factor in initially supporting the higher energy demands of brain expansion in our lineage. Interestingly, significant and rapid brain expansion is not observed in the human lineage until after the appearance of stone tools in the prehistoric record (Holloway et al., 2004; Toth and Schick, 2010). Improved adaptation through intelligent, inventive tool use may also have selected for enlarged brains, and the use of these tools to procure animal resources may have set the stage and allowed the rapid brain expansion that ensued. Of course, a circular feedback mechanism likely ensued, with the brain expansion also supporting enhanced tool-related behaviors and tool evolution, which would have been enhanced by further brain expansion, and so on. It is open for speculation how stone tools were initially invented—that is, how early hominins discovered that hitting one rock against another would produce controlled fracture, and, moreover, that the resulting products could be employed for various tasks that could be useful in their lives and adaptation. This is not an intuitively obvious

operation, and so it is very likely that it was discovered in the process of other tool-using tasks that involved the use of stones. One possible scenario is that stones accidentally fractured in the process of using stone hammers and anvils to break open hard objects, such as nuts or animal bones. The limb bones of dead animals can seasonally provide quantities of nutritious marrow, which is readily obtainable by animals such as hyenas biologically equipped with jaws and teeth that can induce fracture. A hominin using stone to venture into such a dietary niche could have accidentally discovered the basic principle of conchoidal fracture in the course of breaking open bones, and then went on to explore the properties of the artifacts so produced, for instance, in using stone flakes to cut remaining meat tissue or limbs from a carcass. It is apparent, however, from the prehistoric record, that stone tools became incorporated within hominin behavior patterns starting approximately 3.3 mya. It is also clear that hominins began very often to transport stone around the landscape, carrying stone away from their original sources within stream beds and taking them to other locations where they were flaked and/or used, the locales that appear as “sites” in the archaeological record (Leakey, 1971; Schick and Toth, 1993, 2006). Sometimes significant concentrations of stone artifacts were produced on the landscape by such behaviors (Leakey, 1971; Schick, 1987), and some of these sites also contain numbers of animal bones and bone fragments. In some instances, the formation of these large accumulations of stone artifacts ultimately involved transporting hundreds or even thousands of pounds of stone to a particular site, presumably through the efforts of a hominin group, and likely in some instances through repeated site visits (Schick, 1987). Flaked stone was also sometimes removed from such sites, presumably as a hominin group moved on from that location to another and carried potential tools with them for future use. Hominins did not take a random selection of stones locally available, as there is evidence of selectivity and preference in selection of stones better suited for flaking from within the local available sources of stone (Toth, 1985; Semaw et al., 2009). Thus, starting at least 3.3 mya, the evolving human behavioral repertoire had solidly incorporated several new and significant activities revolving around stone tools: locating sources of stone on the landscape, selecting stone that would be better suited for toolmaking, transporting of stone to and from certain favorite locales, flaking stone, and using stone tools for various tasks. This marks a significant behavioral shift in our lineage, not only in the manufacture and use of stone tools, but also in the transport of large amounts of stone resources around the landscape and the evident decision-making and planning involved in such activities. These are behavior patterns unique to our lineage, as they have not been observed in any other species.

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After its beginning at least 3.3 mya, Oldowan technology continued to develop over time, with some new tool categories added to the stone industries, including more tools made by modifying flakes (Leakey, 1971). Change was very slow, however, for several hundred thousands of years of Oldowan technology, without marked shifts in technological procedures. Stone tool sites became more numerous and widespread in Africa, particularly starting approximately 2 mya, with many Oldowan sites discovered first in East Africa and then in South Africa and North Africa. By at least 1.8 mya, hominins had spread out of Africa to western Asia, taking their Oldowan toolmaking tradition with them as evidenced by the site of Dmanisi in the Republic of Georgia (Lordkipanidze et al., 2013).

THE ACHEULEAN AND CONTEMPORANEOUS INDUSTRIES (LATER LOWER PALAEOLITHIC) Starting nearly 1.8 mya, hominins developed new stone tools, called Acheulean technology, that mark a significant departure from Oldowan stone toolmaking (Klein, 2009, 2013; Lepre et al., 2011). The Acheulean tool industry is named after a site in France, St. Acheul, which is much younger than the first Acheulean sites in Africa but is where Acheulean tools had been discovered and recognized in the nineteenth century. These new technologies centered on large flaked tools shaped into forms such as handaxes, cleavers, and picks. These tools are usually rather elongate and often somewhat flat, and very often flaked on both sides (bifacially flaked). Very early Acheulean sites often contained rather thick, trihedral pick-shaped tools (Figure 4). The manufacture of Acheulean tools requires the use of larger pieces of stone than is characteristic of most Oldowan tool industries. In the early Acheulean, tools such as handaxes and cleavers were often made on large flakes that had been struck from very large boulder cores. Such tools can also be fashioned from large, relatively flat cobbles that have been flaked around much of their entire perimeter. The production of such large tools requires acquisition of large cores, which likely reflects ranging patterns that extended greater distances than those needed to acquire cobbles for the manufacture of Oldowan tools, which were generally available in streams more local to the sites. Large boulder cores are more readily available in more upstream, higher energy areas bordering a depositional basin, closer to the bedrock outcrops that serve as the ultimate source of the rock (Isaac, 1984). Thus, the development of Acheulean technology is evidence for hominins using more upstream parts of the environment, for which we have little direct evidence prior to this period. The function of Acheulean tools has been a subject of great interest, speculation, and debate among archaeologists and others (Isaac, 1984; Schick and Toth, 1993). Some have

FIGURE 4  Early Acheulean artifact forms: three crude handaxes and a flake cleaver (bottom right).

argued that they represent cores for flake production rather than tool forms in themselves, while other arguments suggest they may represent multipurpose tools. Experiments in manufacturing Acheulean tools through replicating the technological procedures evidently followed render very unlikely the argument that they are simply cores. The production of these tool forms requires an elaborate series of steps and procedures that are far beyond those needed simply to produce useful flakes and, moreover, tend to minimize the size and number of useful flakes in the latter stages of production when final shaping is being undertaken. Based on experimental replication studies, the manufacture of Acheulean handaxe forms requires more than four times the number of cognitive decisions and procedures as those required by Oldowan toolmaking (Toth and Schick, 2009a). Acheulean tools such as handaxes, cleavers, and picks appear to represent deliberately shaped tools forms, purposefully and sometimes elaborately shaped into their forms for the functions they were to provide. Experimental studies have revealed that handaxes and cleavers are remarkably useful and efficient tools for heavy-duty butchery of large animals, that is, in

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disarticulating limbs and other bones from animal carcasses (Schick and Toth, 1993; Toth and Schick, 2009a). Acheulean handaxes tend to show an emphasis by the tool makers in producing a sharp cutting edge toward the tip end of the tool. Moreover, such tools do not tend to show heavy damage on their sharper edges, indicating that they have been used on softer, more yielding materials rather than on harder materials that would have damaged their edges in use. As they tend to be sharpened along their edges, especially toward the tip end, handaxes provide a lengthy cutting edge along much of the tool’s length, and meanwhile provide a good handle for gripping on the bottom end of the tool that also aids in applying pressure to the cutting operation. Moreover, when bifacially flaked, they essentially have a serrated edge, providing several cutting edges in tandem to allow for longer-lasting sharpness in cutting operations. Experiments have demonstrated that a handaxe not only has a longer cutting edge than a simple flake provides, but one that is useful for much longer (Toth and Schick, 2009a). Acheulean technology represents an extremely longlived tool tradition, lasting from almost 1.8 mya until approximately 250,000 years ago. As such, it is the longest tool tradition known, as subsequent tool industries became progressively shorter in duration and quicker to change over time. Interestingly, during the more than 1.5 million years of its duration, it also survived considerable expansion in geographic distribution of our lineage. The Acheulean tradition has been found from South Africa to the British Isles, from western Europe to the Indian subcontinent. The Acheulean did not, however, seem to spread for the most part throughout all of Eurasia, as it is largely absent from eastern Europe to central and far eastern Asia (Schick and Toth, 1993; Schick, 1994). The manufacture of Acheulean tools such as handaxes and cleavers becomes more sophisticated over time, so that at sites later in the Acheulean period, by one million or half a mya, for example, Acheulean handaxes and cleavers can be very refined (Figure 5). Many such later Acheulean bifaces show remarkable symmetry, both in planform and in profile, and a great deal of finesse in their manufacture. The refinement in the methods of production and in the final product of many later Acheulean bifaces would appear to exceed considerations of function and may represent a developing sense of aesthetics in toolmakers (Schick and Toth, 1993) many hundreds of thousands of years prior to the evolution of H. sapiens.

THE MIDDLE PALAEOLITHIC/MIDDLE STONE AGE Beginning around 300,000 years ago in some parts of Africa, and lasting in some parts of the Old World until approximately 30 thousand years ago (kya), this technological

FIGURE 5  Later Acheulean artifact forms: an ovate handaxe (upper left), a lanceolate handaxe (upper right), and two cleavers made on large flakes (bottom).

stage is usually called the Middle Palaeolithic in Europe, the Near East, and North Africa, and the Middle Stone Age in sub-Saharan Africa (Klein, 2009, 2013; Mellars, 1996). Hominins contemporaneous with this stage of technology include H. neandertalensis (Europe and the Near East), H. helmei and early H. sapiens (Africa), and archaic forms in East Asia (sometimes referred to as “Asian heidelbergensis” or “Asian archaic H. sapiens”). Technologies from this period are characterized by an abundance of flake tools (side scrapers, denticulates, backed knives, points) (Figure 6) that were made on flake blanks sometimes struck from special types of cores, notably radially flaked disc cores and Levallois cores. The Levallois method was used to carefully shape the morphology of the core in order to strike off one or more special flakes, such as large ovate flakes, convergent points, or occasionally blades (flakes that are at least twice as long as they are wide) (Figure 7). These “prepared core” technologies suggest higher cognitive skills and predetermination relative to earlier technologies. Microscopic use-wear analysis on Middle Palaeolithic flint tools indicates that they were used for a variety of tasks, including animal butchery, hide scraping, and woodworking (Beyries, 1988). The morphologies of some of the retouched points suggest that they could have been hafted onto shafts for thrusting or throwing

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FIGURE 6  Middle Palaeolithic/Middle Stone Age artifact forms.

FIGURE 7  Examples of prepared cores. A Levallois “tortoise core” and flake (top), and a Levallois point core and Levallois point (bottom).

spears. In North Africa, tanged points and other tanged tools of the Aterian industry also suggest a hafting technology (Clark, 1982). Such technologies are indicative of “composite tools” that employ several elements together (e.g., stone point, wooden spear shaft, binding such as sinew or vegetable cordage, adhesive mastics such as gums, resin, or pitch). Evidence of fire at habitation sites becomes much more common during this technological stage (Mellars, 1996; Roebroeks and Villa, 2011). Ethnographically, the major ways of hunter–gatherers producing fire are by creating high-temperature friction with the wooden drill/anvil technique, the wooden saw technique, or the thong technique (the latter usually creating friction with a supple strip of bamboo) (Spier, 1970; Hodges, 1995). Habitual manufacture and use of fire implies a sophisticated knowledge of the mechanical methods of production as well as the raw materials required (such as kindling of moss, dung, or some other material). The adaptive advantages of fire production (cooked food, warmth, predator avoidance) and its ultimate consequences are enormous, as the control of production and use of fire would have enabled human populations to spread to less hospitable geographic regions and climates, improve their ability to compete against predators on the landscape, and expand their access to food resources and their nutritional contents.

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FIGURE 8  Upper Palaeolithic/Later Stone Age artifact forms.

It has been argued by some researchers (notably McBrearty and Brooks, 2000) that many of the behavioral traits that we consider to be characteristic of anatomically modern humans in the past 40,000 years have their roots in earlier periods, especially in the Middle Stone Age of Africa. They argue that traits such as blade technologies, hafting, bone tools, geometric crescents, abstract design, the use of ochre, and perforated beads can be found prior to 40,000 years ago. Although this is true, much of this evidence tends to be sporadic, with little long-term patterning or widespread distribution.

THE UPPER PALAEOLITHIC/LATE STONE AGE Beginning around 50  kya, some anatomically modern hunter–gatherer groups began to have technologies that emphasized standardized blade technologies using a soft hammer or a bone or antler punch to produce long, thin blades (Klein, 2009; Pettitt, 2013). This technological stage is called the Upper Palaeolithic in Eurasia and North Africa and the Later Stone Age in sub-Saharan Africa. These blade technologies were a very efficient way of maximizing cutting edge relative to the mass of the stone. These blades could be used not only as cutting

tools unmodified, but they also served as blanks for a wide range of other retouched tool forms, including end scrapers, burins (engraving tools), unifacial and bifacial spear points, backed knives, and pointed awls (Figure 8). In some of these industries flint was heated to make it easier to flake, and pressure flaking (pressing small flakes off with a fabricator of bone or antler) helped to shape delicate stone projectile points. Over time, there is a tendency to produce smaller geometric stone tools (“microliths”) that served as elements of composite tools for points and knives. There is much more standardization of stone tools in this technological stage, as if the rules of production were becoming more codified in the cultures of these foragers. Starting in this final period of the Palaeolithic, there is a record of accelerating use of materials other than stone for various purposes, such as bone, antler, and ivory for a variety of tools such as points, harpoons, needles, and spear throwers (Klein, 2009; Pettitt, 2013). In addition, Upper Palaeolithic peoples used fibers for mats and textiles (Adovasio et al., 1996), wood and animal bones for structures, shells and animal teeth for ornaments, and a variety of materials (ivory, limestone, calcite, clay, slate, ochers, and other pigments) for figurines and various types of artwork (White, 2003; Cook, 2013). Representative art in painting, engraving, and sculpture often

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FIGURE 10  Neolithic artifact forms.

LATER DEVELOPMENTS

FIGURE 9  Upper Palaeolithic material culture and behaviors likely reflecting symbolism.

portrayed the animals of the artists’ world. The famous caves of Chauvet and Lascaux in France and Altamira in Spain are classic examples of Upper Palaeolithic creativity (Clottes and Arnaud, 2003; White, 2003; Cook, 2013) It would appear that Upper Palaeolithic hominins were expressing themselves symbolically through material culture (as well as presumably in other forms of culture such as language, music, dance, and folklore) to a much greater degree than earlier hominins (Figure 9). Architectural features, such as huts or tents, were much more common during this period, and hearths are often ringed with stones (Klein, 2009; Pettit, 2013). Long-distance trade of raw materials (e.g., flint, seashells, and amber) became much more common in this period (Mellars, 1990, 1996). It was during this time that modern humans spread to new continents: to Australia (crossing the Pacific waters from southeast Asia by boat) and to the Americas (spreading from East Asia over the land bridge that existed in the area of the Bering Straits during low sea levels or by following the southern coast by boat).

At the end of the Pleistocene and the retreat of the ice sheets, about 12,000 years ago, all of the world’s human populations were foragers. In the Old World, the postglacial Holocene epoch witnessed many blade and bladelet technologies that tended to produce smaller stone tools (geometric microliths) that were used as composite tools for such implements as arrows and knives (Burdukiewicz, 2005). This technological stage is usually called the Mesolithic. As the Holocene proceeded, hunter–gatherer groups slowly began to independently domesticate plants and animals in several areas of the world, including the Near East, Northern China, Southern China, sub-Saharan Africa, Mesoamerica, Peru, and New Guinea (see chapter by Little). These early farming communities in the Old World are called Neolithic. Societies tended to be more sedentary, with larger populations and more substantial architectural structures (including megaliths) and villages. New technological elements included ground stone axes, pottery, and grinding stones (mortars and pestles) (Figure 10). Longdistance trade of raw materials and manufactured goods (pottery, stone axes, etc.) is characteristic of this stage. As the Neolithic proceeded, there is increasing evidence of social stratification and more complex economic and political organization. Not surprisingly, most of these areas of earliest food production and those to which early food production spread also saw the rise of even more complex societies (“states” or

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FIGURE 12  Some material manifestations of complex societies: writing, monumental architecture, and currency. FIGURE 11  Early examples of metallurgy (Bronze Age).

REFERENCES “civilizations”) often characterized by kingships, a standing army, and a priest class. In the Old World, these complex societies are associated with metallurgy (Tylecote, 2011), first using copper, then bronze, and then iron, wheeled vehicles, and horse riding (Scarre, 2013). In the Americas, these complex societies were beginning to experiment with metallurgy (Figure 11), but still had a strong reliance on stone tools at the time of European contact. Other traits of these societies often included writing, standardized systems of weights and measures, monumental architecture (such as palaces, temples, and tombs), and large-scale engineering such as organized systems of roads and water irrigation (Scarre, 2013; Figure 12). Later civilizations led to the industrial revolution, including the use of fossil fuels to generate energy to power machines, as well as generate heat and light, and mass production of items with interchangeable, standardized components leading to the world we live in today. The challenges facing modern societies—overpopulation, overexploitation of resources, pollution, rise in carbon dioxide levels and world temperatures, etc.—are the end product of a long line of technological and adaptive patterns that can be traced back in the archaeological record 2.5 million years.

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