Technological Origins: Primate Perspectives and Early Hominin Tool Use in Africa
Summary and Keywords
The origin of technology is believed to have marked a major adaptive shift in human evolution. Understanding the evolutionary process(es) underlying the first human adaptation to tool use, and the subsequent process(es) that led Homo sapiens to become the only extant primate fully dependent on technology, is one of the most stimulating topics of research of present-day archaeology. New fields of research have been founded (e.g. primate archaeology, Pliocene archaeology) during the quest to find out how old technology is, where it originated, and who were the first tool users. Historically, the vast majority of the information on this topic comes from the study of lithic (stone) tools, tools whose manufacture was generally believed to be a uniquely human characteristic until well into the 1960s. The production of lithic technology was linked first to the origin of the earliest hominins (the taxonomic group comprising modern humans, extinct human species, and all immediate human ancestors), being thought to have co-evolved with traits such as bipedalism or hunting/scavenging, and later to the evolution of the genus Homo and accompanying increases in brain size. As a result of breakthroughs in the field of primatology, and greater interdisciplinary work between archaeologists and primatologists, a paradigm shift in beliefs surrounding the uniqueness of human technology is underway. Following discoveries from the second half of the 20th century and the early 21st century, habitual tool use, tool manufacture, and the production of flakes are now known to occur in extant non-human species, firmly decoupling brain size expansion, bipedalism, and the origins of technology. Knapped stone tools and cut-marked bones have been discovered dating to ca. half a million years before the earliest evidence of Homo, giving rise to the possibility that earlier, previously unconsidered hominins, or even other extinct non-human primates, could have been responsible for the inception of tool use and manufacture. Following these advances, it is reasonable to hypothesize that the origins of technology may lie much further back in time than the earliest discovered modified stone tools—perhaps as far back as the late Miocene with the last common ancestor of Homo and Pan. Moreover, discoveries of lithic technology in more distantly related species, where convergent evolution is the most parsimonious explanation, strongly suggest the existence of multiple evolutionary pathways for technological emergence. While there is still much to unearth, the extension of the antiquity of modified stone tools, combined with the increased focus on interdisciplinary studies between archaeologists, primatologists, and paleoanthropologists, has gone a long way in overturning outdated beliefs by demonstrating that the development of technology is unlikely to have been a simple, linear process resulting from a single event or factor in the evolutionary history of humans.
Not All Is Set in Stone: A Brief Introduction to the Evolving Picture of Technological Origins
While behavior itself does not fossilize, certain behaviors can be inferred from the traces they leave behind. Two interconnected behaviors that are of great interest to paleoanthropologists are the advent of tool use (defined as “The external employment of an unattached environmental object to alter . . . another object . . . when the user holds or carries the tool during or just prior to use”) and tool manufacture (implying the deliberate modification of materials for use as tools), with the latter being heralded as perhaps “one of the most important adaptive shifts in human evolution.”1 Archaeological discoveries of the remnants of modified stone tools and the damage they have inflicted on fossil remains have long been used to offer insight into the origins of tool manufacture. While the durability of these invaluable resources has allowed the antiquity of technology to be placed at a minimum of 3.3 million years ago (mya), through studying the few and far between traces of stones and fossils alone, only a very small part of the story is revealed.
Adoption of this limited and one-sided approach has led to the perpetuation of false beliefs regarding the uniqueness of Homo sapiens and our hominin ancestors in possessing the ability to make tools. Historical ideas surrounding the early discoveries of flaked stone tools focused primarily on postulated connections between the manufacture of stone tools and the evolution of the earliest hominins, with the former seen as driving the separation of humans from the rest of the animal kingdom. When this theory grew out of favor, tools were tied to the emergence of the genus Homo and the spread of savanna grassland environments during the early Pleistocene. Tool-making was seen as a defining characteristic of “man,” and “man” alone.
But this myth was soon to be dispelled. Observations of chimpanzees making and using tools meant that the production of technology could no longer be used to distinguish humans from the other apes. In time, the fields of archaeology and primatology, once quite separate, began to find an interdisciplinary common ground, as the insight which extant non-human primate technological behavior and site accumulation could bring to the study of hominin tool manufacture and use was recognized.
This, combined with discoveries such as the unearthing of modified stone tools predating the emergence of the genus Homo (placed at 2.8 mya), and the revelation that small-bodied and small-brained monkeys deliberately break stones, producing by-products that mimic early hominin lithics, is resulting in an overturning of long-held beliefs and the instigation of a shift in paradigm that could see the antiquity of tool manufacture extended as far back as the Pan–Homo split.
In this article, the current state of knowledge regarding the origin of stone tool manufacture is reviewed, providing the reader with a historical understanding of the shifts in belief and paradigm that have occurred in the field of paleoanthropology (see Table 1 for an overview) and are likely to occur in the future.2
Table 1. The Key Milestone References at a Glance
1859: Bifacial stone tools of great antiquity discovered in Saint Acheul, France (later given the name of the Acheulean)—the antiquity of humankind recognized to undeniably extend beyond the temporal framework outlined in the Bible
1931: Announcement of the discovery of “pre-Chellean” stone tools at Olduvai Gorge (formally described as the “Oldowan” in 1934)
1950s: Proposal of a bone tool industry employed by South African australopithecines, the osteodontokeratic, which would mark a new beginning of technology (later discredited)
1959: Discovery of Zinjanthropus (now Paranthropus) boisei at Olduvai Gorge in association with the Oldowan culture
1960: Discovery of a new species, Homo habilis (“handy man”), at Olduvai Gorge, deemed to be the maker of the Oldowan
1963: Jane Goodall reports observations of chimpanzees making tools in the wild
1997: Date of the emergence of stone tools is pushed back to 2.5–2.6 mya by the discovery of a new Oldowan assemblage in Gona, Ethiopia
1999–2005: Older than the Oldowan? Revelations suggest that the makers of the oldest known tools were surprisingly skilled—possibility that stone tool manufacture may predate the evidence from the archaeological record is seriously considered
2007: Landmark study in chimpanzee archaeology reports the excavation of 4,300-year-old stone artifacts in Côte d’Ivoire believed to be used by chimpanzees, leading to the recognition of a chimpanzee Stone Age
2008–2009: First field studies in primate archaeology (i.e., directly recording primate tool use while using archaeological methodologies) report similarities between Oldowan and Pan strategies for resource exploitation, suggesting that accidents during the use of percussive technology lead to the unintentional production of by-products such as flakes
2010: ~3.4 mya stone tool-produced cut and percussion marks discovered on fossilized bones in Dikika, Ethiopia
2015: Discovery of 3.3 mya stone tools in Lomekwi 3, West Turkana, Kenya, belonging to a new stone tool industry, the Lomekwian
2016: Capuchin monkeys are discovered to unintentionally flake stones, producing by-products that appear indistinguishable from some hominin stoneflakes and cores; capuchin assemblages are dated c. 700 years old
“Man” the Tool-Maker: A Historical Overview of Ideas Regarding the Earliest Emergence of Lithic Technology
Identifying the antiquity of stone tool manufacture is a key area of research within the study of prehistoric archaeology and human evolution. In fact, instrumental to the origin of these two disciplines was the mid-19th-century discovery of early stone tool remains which demonstrated that the existence of humankind extended much further back in time than indicated by the Bible—from which the previously predominant understanding of human origins had derived.16 The stones that in effect shattered the time barrier consisted largely of distinctive teardrop-shaped hand-axes which would later come to be known as the Acheulean (named after the site of Saint Acheul in northern France): a lithic technology heralded at the time of its description, and for several subsequent decades, as marking the inception of the Stone Age.17
The first half of the 20th century saw the proposal of two new lithic technologies that were believed to predate the Acheulean and mark a new beginning of the archaeological record. In the 1920s, Wayland discovered an assemblage of crudely made “pebble tools” in Uganda, from what was named the “Kafuan Culture”; however, these supposed tools were later rejected after re-evaluation suggested they were naturally produced through geological processes.18 The second stone tool industry discovery of the century proved much more fruitful and did indeed come to signify a new starting point of the archaeological record: the Oldowan.19 Following the initial discovery by Louis Leakey during fieldwork at Olduvai Gorge, Tanzania in 1931, the Oldowan was formally described in 1934 as a simple pebble industry comprising sharp-edged stone tools that had been produced by the removal of a few flakes—though subsequent work has shifted the focus to the flakes themselves as cutting implements and the goals of the production sequence rather than the by-products, a more consensual view is that both objects, the modified core and the by-product, would have been used as multipurpose tools.20 In the literature of the time, tool use was being classed as a defining feature of humans, and while it was acknowledged that apes sometimes made use of natural objects as tools, “man” alone was afforded the title of tool-maker.21 The adoption of tool use and the way of life that accompanied it was proposed to have kick-started human evolution and led to the emergence of modern “man” with his bipedal gait and large brain, in a similar vein to the initial suggestion by Darwin that tool use prompted early humans to walk upright to free the hands to better carry and manipulate tools.22 Questions of human antiquity became intrinsically linked to questions of the age of the earliest artifacts, and the identity of the earliest tool-makers was a hot topic of debate.23
In the 1950s, the South African australopithecines received considerable attention as potential tool users following their association with a proposed new tool industry in the Makapansgat assemblages, the osteodontokeratic, which consisted primarily of the bones of other animals.24 Dart suggested that the bones were used by the australopithecines as tools, perhaps for hunting and processing carcasses. Regarding the Makapansgat assemblages, this theory was later disproved when re-examination led to the conclusion that the proximity of australopithecine and animal bones resulted from carnivore activity, with the australopithecines being among the prey, rather than the predators.25 Nevertheless, the possibility of bone tool use by South African australopithecines remains an open debate.26
In 1959, a potential breakthrough was made when the fossilized skull of an early hominin was discovered at Olduvai in association with Oldowan stone tools and fossilized broken animal bones.27 The interpretation was that the skull represented one of the makers of the Oldowan stone tools whose diet, as evidenced by the associated broken animal bones, would have been derived, at least partially, from animal protein. The skull was assessed to be sufficiently morphologically different to both Australopithecus and Paranthropus to warrant its inclusion in a distinct genus where it received the classification of Zinjanthropus boisei. In addition to the creation of a new genus in its honor, it was proposed that Zinjanthropus may have been ancestral to the genus Homo—a phylogenetic link that was in part drawn from the association of Zinjanthropus with stone tool manufacture and use, and the advanced mode of life this was suggested to represent.28
However, in 1960 the discovery of a new species of hominin at Olduvai pertaining to a more gracile and human-like branch of our evolutionary tree led to a reformulation of events that resulted in Zinjanthropus boisei being stripped of its title as tool-maker, transformed from the hunter to the hunted, and reassigned to the genus Paranthropus. The newly discovered species became the recognized maker of the Oldowan stone tools and, as such, was granted a place within our own genus where it was awarded the name Homo habilis (meaning “handy man”), becoming the earliest recognized species of Homo.29 Upon examination of this new evidence, the previously held assumption that Zinjanthropus produced the Oldowan stone tools was abandoned in favor of the more fitting (but equally as sensational) proposition that the Zinjanthropus skull represented “an intruder (or a victim) on a Homo habilis living site.”30 Following criticism of the classification of the Zinjanthropus skull discovered at Olduvai, subsequent reanalysis found insufficient evidence to warrant the justification of a new genus, and so the skull was reclassified as belonging to the Australopithecus/Paranthropus lineage.31
The earliest evidence of Homo was now coincident with the earliest evidence of stone tools, and so naturally links were made between the two.32 The innovation of stone tool manufacture was suggested to be the adaptive shift that differentiated the genus Homo from Australopithecus, and this adaptive shift was, in turn, hypothesized to be tied to a change in climate—notably a reduction in rainfall resulting in more arid conditions and the spread of savanna grasslands.33 The close association and potential link between the origin of stone tool manufacture and marked hominin brain expansion was once again a popular point of discussion, this time with reference to the possibility of shared novel behaviors, such as meat eating and hunting, which resulted in the coincidence of the inception of the visible archaeological record and the appearance of larger-brained hominins attributed to the genus Homo.34 It was thought that our genus alone accomplished the feat of manipulating objects in the environment for personal gain, ultimately leading to our evolutionary success.
From early attempts to link the advent of lithic technology and the origin of hominins, to the justification of Zinjanthropus as a new genus and potential ancestor to modern humans on the basis of its spatial association with manufactured stone tools, and then the later reformulation of events that saw the emergence of the genus Homo and the inception of stone tool manufacture become intrinsically linked, the paradigm of “man the tool-maker” heavily influenced early hominin phylogenetic classification and the study of human evolution.
“Man” and Pan the Tool-Makers: A Contemporaneous and Conflicting Finding in the Field of Primatology
Despite the persistent popularity of “man the tool-maker” as a paradigm well into the 1960s, in 1960 observations were made and later published of a non-human primate species manufacturing tools in the wild—clearly communication between the fields of archaeology and primatology was not commonplace.35 Following fieldwork in Gombe National Park, Tanzania, the young primatologist Jane Goodall reported observations of wild chimpanzees (Pan troglodytes) using natural objects as tools for a variety of tasks, including the use of sticks to harvest insects for consumption, leaves to wipe the body or collect water for drinking, and stones and various other materials as projectiles during displays of aggression and excitement.36 In addition to the reports of abundant tool use, on occasion tools were seen to be “carefully prepared,” that is, manufactured.37 Such manufactured tools included termite fishing sticks that were created by picking a stem or twig and then using the mouth or hands to strip it of its leaves. This was the first reported instance of tool manufacture in a non-human primate and it contradicted the main school of thought at the time that only humans possessed the capability to make tools. Upon learning of the groundbreaking observations, Louis Leakey, who had mentored Goodall and was instrumental in getting her to Gombe, famously responded, “Now we must redefine tool, redefine Man, or accept chimpanzees as humans.”38 Others were less quick to acknowledge the findings. Oakley, who had previously contended that “It is in making tools that man is unique,” was forced to revise his argument.39 The tool-making capabilities of non-human apes were acknowledged but downplayed on the basis of the assumed rarity of tool production occurrences. Meanwhile, “man” became the skilled tool-maker, and tool manufacture an integral part of human behavior.40
While there is no doubt that recent advances in human technology are unrivalled within the animal kingdom, following the initial observations of wild chimpanzee tool manufacture, increased focus on the technological behavior of non-human primates revealed patterns of habitual tool use and manufacture among populations of chimpanzees.41 Another behavior that was historically connected exclusively with humans and our ancestors, the use of lithic technology for food processing, was reported among chimpanzees in West Africa who were subsequently recorded to frequently use stone tools to crack open nuts.42 Immediately the connection between early hominin tools and the primate lithics was made, with researchers going so far as to suggest that “if they had been found at excavation sites, archaeologists almost certainly would have judged them as human stone tools.”43 Nevertheless, the full extent of the benefit that studies of primate technological behavior could offer the field of human technological origins took time to be fully recognized.
Older Than the Oldowan: Speculation and Archaeological Evidence
Fast-forward a few decades and new discoveries in the fields of archaeology and paleoanthropology were favoring a shift in paradigm in the understanding of stone tool origins. The finding that the first hominins were roaming (and perhaps walking) the earth as far back as six to seven mya saw that theories linking the inception of tool manufacture to hominization and bipedalism were well and truly laid to rest.44 Nevertheless, connections continued to be made between the advent of tool manufacture, the emergence of the genus Homo, and the changing climate of the Plio-Pleistocene.45
However, in 2002, incorporating indirect evidence from primatology, functional anatomy, and molecular phylogenetics, as well as direct evidence from more traditional sources, Panger and colleagues argued that hominins may have used and possibly also manufactured stone tools prior to the date suggested by the earliest traces of technology in the archaeological record.46 They noted that the date associated with the earliest evidence of the modification of stone tools marks only the first time this behavior became archaeologically visible and so may underestimate the inception of tool use and manufacture by “millions of years”—along similar lines to the argument put forward by Schick and Toth that “there may be an even earlier stage of stone technology in the archaeological record, perhaps rare and difficult for the archaeologists to identify.”47 Using the principle of parsimony, it has been postulated that, because tool use is known to occur habitually in all chimpanzee and human populations, the last common ancestor of Pan and Homo may also have used tools.48 Although this is not supported directly by the fossil record, the fact that the brain size estimations of early fossil hominins are similar to those seen in tool-using apes, and that their hand morphologies are suggestive of even greater manipulative ability, does imply that the capacity to use tools was present prior to the earliest evidence of tool use.49
Meanwhile, the archaeological record was being extended further and further back in time. Discoveries in Gona, Ethiopia of the oldest known Oldowan assemblage placed the earliest archaeological evidence for the manufacture of stone tools at 2.5–2.6 mya.50 The date for the earliest emergence of Homo rested at around only 2.4 mya, inciting speculation that the first stone tool-makers may not have been members of the genus Homo after all.51
Furthermore, analyses were suggesting that the early Oldowan tools appeared too sophisticated in their manufacture to represent the first instances of hominin knapping. Even the very earliest Oldowan stone tools from Gona were noted to display sophisticated control strongly suggestive of an earlier inception of stone tool manufacture.52 Other often-cited examples are the Oldowan lithics from the site of Lokalalei 2C dated to 2.34 mya, which appear to have been formed following a highly controlled sequence of flake removals requiring foresight and planning on the part of the knappers that would not be expected so early in the inception of this new behavior.53 As well as being capable of elaborate and advanced debitage, the Oldowan-producing hominins also appeared to be selective with their choices of raw materials, suggesting an advanced understanding of the knapping process and the advantages of raw material selectivity.54
The discovery of fossilized bones bearing stone tool-produced cut and percussion marks, found in Dikika, Ethiopia and dated to approximately 3.4 mya, added considerable weight to the argument that hominins may have been using and manufacturing stone tools prior to 2.6 mya and that the first knappers may not have been a species of the genus Homo.55 The fossils—a rib fragment of a large ungulate and a femur shaft fragment of a bovid—were found to display cut marks consistent with flesh removal using a sharp-edged stone and percussion marks suggestive of strikes to the bone using a blunt stone to access the marrow. Since the age of the fossil remains precludes the Homo species as the agents, the processing and assumed subsequent consumption of these remains has been attributed to Australopithecus afarensis, though it has not thus far been possible to determine whether this species was using purposefully knapped stone tools or rather making use of naturally sharp but unmodified stones. Either way, the remains from Dikika represent the earliest indirect evidence of stone tool use among hominins; and, while this cannot be taken as direct evidence that Australopithecus afarensis made stone tools (though this is certainly one explanation), at minimum it shows that pre-Homo hominins had the cognitive and manual capabilities required to use stone tools to exploit carcasses for nutritional gain.56
Then in 2015, after what was a long time coming, evidence was published of the discovery of a new stone tool industry, the Lomekwian, which predates the oldest known Oldowan tools by 700,000 years.57 This lithic assemblage—discovered in Lomekwi 3, West Turkana, Kenya and dated to 3.3 mya—consists of a minimum of 149 modified stone artifacts (75 percent of which are associated with percussive activities) and currently represents the first direct evidence of stone tool manufacture in the archaeological record. In the same year, the earliest known fossil evidence of the genus Homo was also pushed back in time, but only to 2.8 mya, half a million years too late for the manufacture of stone tools to be unique to members of the genus Homo as was once thought.58 Unless earlier evidence of the Homo lineage is found, it would appear that the first stone tool-makers far predated members of the genus Homo.59
Primate Archaeology: The Origin and Evolution of the Discipline and Its Contribution to Our Understanding of Technological Origins
Against the backdrop of these discoveries, a new field of research was evolving: primate archaeology. Traditionally, archaeology has been an anthropocentric discipline, concerning only the material remains of past humans and our hominin ancestors.60 However, once it was recognized that humans were not the only primates to habitually use stone tools and thus leave behind a potentially observable material record of behavior, the possibility of expanding the discipline of archaeology to encompass the study of non-human species arose. In the decades following the pioneering work of Goodall, the advantages of the study of great ape stone tool use in regard to the evolution of hominin technology were recognized, leading to considerations of the human material evidence from an ape’s view, and interdisciplinary studies such as the attempt by Paleolithic archaeologists and cognitive psychologists to teach Kanzi, the well-studied captive bonobo, to make and use stone tools.61
By the mid-1990s, real interest had begun to develop in the archaeology of non-human primate material culture, and with the turn of the century came the first archaeological excavation of a non-human lithic site.62 Researchers employed conventional techniques used in the recovery of early hominin archaeological sites to excavate a recently occupied chimpanzee nut-cracking site in Taï National Park, Côte d’Ivoire, and found a detectable record of buried unintentionally fractured stones resulting from tool use and plant consumption which was comparable to some Oldowan occurrences.63 Building on this work, the same techniques were utilized to investigate the possibility of identifying the existence of ancient chimpanzee nut-cracking sites in order to make inferences about the origin of percussive material culture and shed light on the antiquity of tool-assisted nut-cracking in chimpanzees, which at the time was completely open to speculation (so much so that, for all that was known, the behavior may just as well have emerged sometime within the last hundred years as within the last million).64 As has been remarked, despite primatology’s strong focus on behavioral studies of primates in the present, “The primates that happened to be alive during the geologically recent birth of primatology as a science are very probably not the only ones that used or potentially even made stone tools.”65 Lo and behold, behaviorally modified stones dated to 4,300 years of age and bearing evidence of food residues suggestive of chimpanzee nut-cracking were retrieved from the site in Taï National Park, proving that long-lasting records of material culture are not only produced by humans. This important finding prompted speculation that the roots of hard-hammer percussive technology could lie in the last common ancestor of chimpanzees and humans.66 However, it is important to note that stone tool use is not known to be ubiquitous among all chimpanzees—rather it appears to be restricted to West African populations—and therefore the specific use of stones as tools is unlikely to be an ancestral trait.
Following this initial work, there was an intensification of interdisciplinary studies whereby archaeologists began branching out of their traditional areas of research involving the analysis of tools and their by-products and started investigating the formation of non-human primate archaeological sites in real time and relating this to behavior and the origins of technology.67 In addition to chimpanzees and humans, wild Burmese long-tailed macaques in Thailand (Macaca fascicularis aurea) and bearded capuchin monkeys in Brazil (Sapajus libidinosus) have also been observed to routinely use stone tools, the former for extractive foraging in the form of shellfish pounding, and the latter for nut-cracking and stone-on-stone percussion.68 Archaeological techniques have been used to investigate the stone tool assemblages produced by these behaviors, adding New and Old World monkeys to the list of primates for whom there now exists an ancient record of tool use behavior, and resulting in, among other interesting developments, capuchin stone tool-assisted nut-cracking in the Serra da Capivara National Park of Northeast Brazil being dated back at least 700 years.69
In addition to minimizing the temporal uncertainty of non-human technological behaviors and establishing a prehistory of primates, studies falling under the umbrella of primate archaeology have shed light on the innovation and potential loss of technological behavior and the spread of cultural tool-use traditions within and between groups, helping to inform the understanding of these topics with regard to the evolution of hominin technology.70 Because habitual stone tool use occurs only in some populations of chimpanzees, and among New and Old World monkeys has only been observed in capuchins and macaques, respectively, parsimony suggests that a common origin of stone tool use among these species and humans is highly unlikely. Moreover, a greater focus on the importance of the comparative perspective for studying hominin technology has led to a wealth of observations of non-human animal tool use. From crows to cetaceans, a variety of non-primate species are known to use tools; in addition to being widely recorded in chimpanzees, tool manufacture has also been observed in wild orangutans (Pongo spp.), capuchin monkeys (Sapajus libidinosus), and the far more distantly related New Caledonian crow.71 Therefore, neither the behavior of tool use (including the special case of lithic technology), nor that of tool manufacture, is unique to humans, our hominin ancestors, or species belonging to the primate order. The newly emerging evidence from primate archaeology, and the discoveries of tool use outside of the primate order, both indicate that the story of hominin tool use is unlikely to be as straightforward as a single invention of technology followed by a linear evolution. The ancestral diversity of species associated with lithic technology and tool use suggests that convergent evolution of independent technological innovations may have occurred in several different lineages and individual species where ecological conditions favored the use of tools.72 This interpretation suggests that the loss and reinvention of tool use throughout the evolutionary history of the primate order was a real possibility.73
Adding another layer to the debate, following excavations in 2015 and behavioral records in primate archaeology, it has been found that the deliberate stone-on-stone percussion performed by capuchin monkeys leads to the unintentional production of sharp-edged flakes and cores that resemble early hominin lithics.74 Prior to this observation, only humans and their hominin ancestors were believed to possess the ability to sequentially remove flakes from a core. The morphological features of a flake have been traditionally used to recognize hominin intentional behavior.75 Use of the modified stones as cutting or scraping implements has not been observed among capuchins—the makers appear to be breaking the stones in order to produce powdered quartz or lichens which are licked or sniffed (perhaps related to ingestion of nutritional components such as the essential trace nutrient silicon), a process that inadvertently leads to the production of flakes as by-products.76 The capuchin data demonstrates a number of things that are of particular importance in the present context. Firstly, human-like advanced cognition, coordination, and manual dexterity are not prerequisites for lithic flake production; therefore, caution should be practiced when lithics alone are used to interpret characteristics of the species that produced them. In a similar vein, attributing intentionality of behavior based solely on findings in the archaeological record is difficult and may not be accurate. As commented by the authors, if found in a hominin archaeological context, the capuchin-modified stones may well have been wrongly interpreted as purposefully knapped stone tools.77 Lastly, the discovery that wild monkeys produce sharp-edged stone flakes removes yet another behavior from the list of uniquely human traits and adds considerable support to the ongoing paradigm shift.
A Show of Hands: Who Were the Earliest Tool-Makers?
While Homo habilis and later human species were likely responsible for some of the discovered Oldowan assemblages, the chronology of stone tool emergence created by the Lomekwian findings suggests that the first stone tool-makers may have predated the genus Homo. So, if Homo habilis was not the first stone tool-maker after all, then who was? A number of cores found at the site of Lomekwi 3 show evidence of hinge and step flake terminations consistent with knapping accidents, suggesting that the makers’ techniques and understanding of stone fracture mechanisms were inferior to that of the makers of the Oldowan.78 Nonetheless, they must have possessed relatively well-developed hand motor control and precision grip in order to manufacture stone tools.79 The team responsible for the discovery of the Lomekwian have put forward two possible candidates: Australopithecus afarensis and Kenyanthropus platyops.80
The first, Australopithecus afarensis, is a match for both the temporal and spatial range, and has been suggested to be the producer of the cut-marked bones from Dikika which represent the earliest indirect evidence of stone tool use among hominins.81 While these fossilized faunal remains no doubt represent a valuable discovery in the search for the earliest stone tool-makers, more indirect evidence—such as results of comparative functional anatomy analyses—can also be informative.82 The hand of Australopithecus afarensis displays a number of features distinct to modern humans that are believed to enable human-like precision grip, and could have granted Australopithecus afarensis the ability to use tools with greater force, control, and enhanced manipulative function compared with that of extant non-human primates.83 However, morphology also suggests that Australopithecus afarensis had less thumb mobility than modern humans, which could have compromised their ability to manufacture stone tools.84 In addition, biomechanical simulations suggest that the hand of Australopithecus afarensis may have struggled to exert the level of force sufficient to produce the Lomekwian stone tools.85 Though specific data is not available for Australopithecus afarensis, an analysis of metacarpal trabecular bone (which is known to remodel in response to mechanical loading throughout an individual’s lifetime) suggests that capabilities for habitual human-like forceful opposition of the thumb and fingers, typically associated with tool-related behaviors, may have existed in the australopithecines.86 The trabecular structures of Australopithecus africanus and several younger Pleistocene hominins were found to be distinct from that of extant non-human apes, but closely resembled patterns seen in committed tool-makers (humans and Neanderthals), providing morphological support for committed tool use and possibly manufacture in the australopithecines.87 While these studies provide some support for the use of tools, possibly including modified stone tools, by Australopithecus afarensis, derived adaptations of the hand suggestive of tool use may also be linked to other manipulative tasks, meaning the current morphological evidence alone is inconclusive.88
In addition, Kenyanthropus platyops remains—specifically the remains of the paratype (KNM-WT- 38350), as well as various other fossils considered to belong to this species—have been discovered in close geographic and temporal proximity to the Lomekwian tools.89 Thus, Kenyanthropus platyops is also a strong candidate. Unfortunately, no postcranial remains of Kenyanthropus platyops have currently been discovered, ruling out morphological analysis of their potential tool-making capacities at present. There is also a further complication: the paratype for Kenyanthropus platyops has been closely compared to a different fossil hominin species, Australopithecus deyiremeda. This relatively newly discovered species—found in central Afar, Ethiopia and dated to 3.3–3.5 mya—shares with Kenyanthropus platyops several features that were originally used to classify the paratype (a partial left maxilla).90 The features that distinguish the two species from one another are not preserved in the paratype and so the possibility that Australopithecus deyiremeda was also in the right place at the right time cannot be ruled out.91
Nevertheless, associating stone tools with the specific species that may have produced them is notoriously challenging, and while researchers can make informed guesses concerning the tool-using capabilities of a species based on its hand morphology, evidence that a species possesses hand morphology consistent with tool use, alone, does not automatically equate to tool use in this species.92 Furthermore, it must be remembered that the makers of the tools at Lomekwi 3 and the makers of the first stone tools may not have been one and the same. While archaeologists have yet to find older stone tools, absence of evidence is not evidence of absence. Long before the discovery of the Lomekwian, Panger and colleagues suggested that the earliest archaeological evidence for stone tool manufacture may not align with the emergence of this behavior, but instead may mark the first time that it became archaeologically visible.93 Arguably the same logic still holds: stone tool manufacture prior to 3.3 mya could have occurred, but evidence of this behavior in the archaeological record may be as yet undiscovered or indeed more difficult to trace; this is particularly the case if the tools have only a minimal number of flakes removed and are not concentrated in time and space, as would be expected at the emergence of the behavior. The same logic also overwhelmingly applies to the emergence and extinction of distinct species. Therefore, when attempting to identify the earliest stone tool-makers, the list of potential candidates should not be tightly constrained by the ages attached to the oldest current evidence of modified stone tools in the archaeological record, or indeed the currently held dates of first and last appearance of a species as evidenced by the fossil record.
Moving towards an interdisciplinary approach to questions of technological origins, comparative evidence places the advent of technology much further back in time than does direct evidence from the archaeological record. It is now widely known that our closest living relatives, chimpanzees, habitually use and manufacture tools to perform a number of tasks including termite fishing, hunting, nut-cracking, and honey extraction, and both tool use and tool manufacture have been observed and reported in all chimpanzee populations studied to date.94 Parsimony would thus suggest that the last common ancestor of chimpanzees and humans also used and manufactured tools, meaning that the origin of technology is unlikely to be linked solely to hominin evolution.95 However, this hypothesis has been met with some skepticism.96 Chimpanzees are not the only non-human primates (or more broadly animals) known to use and modify tools. Research in the field of primate archaeology has demonstrated that technology can evolve independently, as is the most parsimonious case for stone tool use occurring in extinct hominin species, capuchin monkeys, and macaques despite the vast evolutionary distances that separate them and the rarity of stone tool use within the primate order. This same principle of convergent evolution could reasonably be invoked for chimpanzee and human shared technological behaviors, and could even be extended to inventions of modified stone tools in geographically and temporally distinct populations of hominins from the same or closely related species. In summary, the story is not a simple one.
Discussion of the Literature
Over the course of the last sixty years, our knowledge of technological origins has expanded greatly: from the establishment of “man the tool-maker” and the belief that stone tool use was a defining characteristic of the genus Homo, to the decoupling of stone tool origins and the emergence of Homo, and the recognition of and interest in non-human primate (and, more broadly, animal) tool use and manufacture as a model for studying the evolution of human behavior.97 The accumulation of recent discoveries in primatology and the archaeology of human origins has helped to dispel outdated hypotheses and ways of thinking about our own lineage. Despite being the predominant view in the 1960s, it is now known that neither tool use, nor tool manufacture, nor even the production of stone flakes, sets humans or our hominin ancestors apart from the rest of the animal kingdom.98 Furthermore, no longer can stone tool manufacture be credited to the genus Homo alone; nor can support be given to theories that rely on the timing of the development of lithic technology, the transition to Homo, and the spread of savanna grassland environments being coincident and intrinsically linked.99
Comparative studies of non-human primates have illustrated that technology can develop independently of human characteristics such as bipedalism, large brain size, and advanced manual dexterity; and that the adoption of tools is unlikely to have been the driving factor for the earliest transitions in human evolution. While the adept tool use and manufacture performed by our closest living relatives suggests that technological behavior may have been established in the last common ancestor of chimpanzees and humans, the use of stone tools by more distant primate relatives, the capuchins and macaques, suggests that convergent evolution may also explain the emergence of technology in several species or populations of species. These observations lead to a complex view of technological origins that certainly does not follow a simple linear pattern.100
In order to advance our knowledge of technological origins, the search for early hominin stone tools must continue, particularly focused on surveying Pliocene deposits once thought not to bear any archaeological sites. However, just as important is the search for early primate stone tools. Researchers in the field of primate archaeology are only just beginning to scratch the surface with regard to the origins of non-human primate technology. The oldest evidence of non-human tool use rests at 4,300 years ago.101 Judging by the history of discoveries of hominin stone tools, this date is unlikely to remain unchanged for long. By studying tool use in extant non-human primates, through both behavioral observation and archaeological excavation, important information can be gained on assemblage formation and methods for recognizing minimally modified tools and lithics that may only be altered through use, and not prior to use. Since the first instances of hominin stone tool use are likely to fall into these categories, this will greatly improve chances of refining the antiquity of hominin tool use in addition to determining the phylogenetic position of this behavior in relation to the tool-using behaviors of other primates.102
This departure from the human uniqueness of technology and recognition of the importance of the archaeology of non-human species is reflective of a greater trend within the field of human evolution that is seeing increased emphasis placed on both the similarities and the differences between humans and other extant apes (and primates more broadly), and recognition of the positive impact that studies of non-human primate behavior can have on our understanding of human origins.
Although much research has been taking place in Africa since the 1930s, collections pertaining to the earliest Oldowan are relatively scarce, especially when compared with the subsequent techno-cultural complex of the Early Stone Age (i.e., Acheulean). This is explained both by the lower density and the distribution of archaeological sites from this time period (2.6 to 1.7 mya) and by the smaller number of archaeologists and research teams that have devoted themselves to investigating the earliest technologies. Key collections are housed at the National Museums of Kenya in Nairobi, the National Museum of Ethiopia in Addis Ababa, and the Arusha National Natural History Museum in Tanzania. Iconic Oldowan specimens such as the products of Louis Leakey’s first expedition to Olduvai Gorge in 1931 are housed in the British Museum, London. The Smithsonian National Museum of Natural History in Washington, DC, United States, exhibits some of the Lokalalei (Kenya) tools, and offers a resourceful online platform to explore examples of Early Stone Age tools. The scarcity (and novelty) of the pre-Oldowan and non-human primate tools makes them even more difficult to access. The Lomekwian tools are deposited in the National Museums of Kenya. A small display of non-human primate stone tools is currently available at the Oxford University Museum of Natural History in Oxford, United Kingdom, but the vast majority of the non-human primate stone tool assemblages are housed at the institutions where researchers carrying out the primate archaeology studies have been working, for example the University of Oxford in the United Kingdom and the Max Planck Institute in Germany. At Oxford, the Primate Models for Behavioural Evolution Lab is undertaking the creation of the first Primate Digital Library, which will include a virtual collection of non-human primate tools available by 2020.
Campbell, Rolian, and Susana Carvalho. “Tool use and manufacture in the last common ancestor of Pan and Homo.” In Chimpanzees and Human Evolution. Edited by M. Muller, R. Wrangham, and D. Pilbeam, 602–644. Cambridge, MA: Harvard University Press, 2017.Find this resource:
Carvalho, Susana, and William C. McGrew. “The origins of the Oldowan: Why chimpanzees (Pan troglodytes) still are good models for technological evolution in Africa.” In Stone Tools and Fossil Bones: Debates in the Archaeology of Human Origins. Edited by M. Domínguez-Rodrigo, 222–244. Cambridge: Cambridge University Press, 2012.Find this resource:
Delagnes, Anne, and Hélène Roche. “Late Pliocene hominid knapping skills: the case of Lokalalei 2C, West Turkana, Kenya.” Journal of Human Evolution 48 (2005): 435–472.Find this resource:
Harmand, Sonia, Jason E. Lewis, Craig S. Feibel, Christopher J. Lepre, Sandrine Prat, Arnaud Lenoble, Xavier Boës, Rhonda L. Quinn, Michel Brenet, Adrian Arroyo, Nicholas Taylor, Sophie Clément, Guillaume Daver, Jean-Philip Brugal, Louise Leakey, Richard A. Mortlock, James D. Wright, Sammy Lokorodi, Christopher Kirwa, Dennis V. Kent, and Hélène Roche. “3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya.” Nature 521 (2015): 310–315.Find this resource:
Isaac, Glynn L. “Foundation stones: early artifacts as indicators of activities and abilities.” In Stone Age Prehistory. Edited by Geoff N. Bailey and Paul Callow, 221–241. Cambridge: Cambridge University Press, 1986.Find this resource:
McPherron, Shannon P., Zeresenay Alemseged, Curtis W. Marean, Jonathan G. Wynn, Denné Reed, Denis Geraads, René Bobe, and Hamdallah A. Béarat. “Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia.” Nature 466 (2010): 857–860.Find this resource:
Panger, Melissa A., Alison S. Brooks, Brian G. Richmond and Bernard Wood. “Older than the Oldowan? Rethinking the emergence of hominin tool use.” Evolutionary Anthropology 11 (2002): 235–245.Find this resource:
Proffitt, Tomos, Lydia Luncz, Tiago Falótico, Eduardo B. Ottoni, Ignacio de la Torre, and Michael Haslam. “Wild monkeys flake stone tools.” Nature 539 (2016): 85–88.Find this resource:
Semaw, Sileshi, Paul Renne, John W. K. Harris, Craig S. Feibel, Raymond L. Bernor, Nardos Fesseha, and Kenneth Mowbray. “2.5-million-year-old stone tools from Gona, Ethiopia.” Nature 385 (1997): 333–336.Find this resource:
Stout, Dietrich, Nicholas Toth, Kathy D. Schick, and Thierry Chaminade. “Neural correlates of early Stone Age toolmaking: technology, language and cognition in human evolution.” Philosophical Transactions of the Royal Society B 363 (2008): 1939–1949.Find this resource:
Thompson, Jessica, Susana Carvalho, Curtis Marean, and Zeresenay Alemseged. “The origins of the human predatory pattern: The transition to large animal exploitation by early hominins.” With series of comments. Current Anthropology (2018).Find this resource:
(1.) Benjamin B. Beck, Animal Tool Use: The Use and Manufacture of Tools by Animals (New York, NY: Garland, 1980), 10; Lawrence Barham and Peter Mitchell. First Africans: African Archaeology from the Earliest Tool Makers to Most Recent Foragers (Cambridge World Archaeology) (Cambridge University Press, 2008); and Thomas Plummer, “Flaked Stones and Old Bones: Biological and Cultural Evolution at the Dawn of Technology,” American Journal of Physical Anthropology 125, no. S39 (2004): 118.
(2.) For more details, see Ignacio De la Torre, “The Origins of Stone Tool Technology in Africa: A Historical Perspective,” Philosophical Transactions of the Royal Society of London B: Biological Sciences 366, no. 1567 (2011): 1028–1037.
(3.) de Mortillet, Classification Des Diverses Pé riodes de l’â Ge de La Pierre, Par Gabriel de Mortillet.
(4.) Leakey, Hopwood, and Reck, “New Yields from the Oldoway Bone Beds, Tanganyika Territory.”
(5.) Dart, “Makapansgat Australopithecine Osteodontokeratic Culture.”
(6.) Leakey, “A New Fossil Skull from Olduvai.”
(7.) Leakey, Tobias, and Napier, A New Species of the Genus Homo from Olduvai Gorge.
(8.) Goodall, “My Life among Wild Chimpanzees”; and Goodall, “Tool-Using and Aimed Throwing in a Community of Free-Living Chimpanzees.”
(9.) Sileshi Semaw et al., “2.5-Million-Year-Old Stone Tools from Gona, Ethiopia.”
(10.) Roche et al., “Early Hominid Stone Tool Production and Technical Skill 2.34 Myr Ago in West Turkana, Kenya”; Panger et al., “Older than the Oldowan?”; and Delagnes and Roche, “Late Pliocene Hominid Knapping Skills.”
(11.) Mercader et al., “4,300-Year-Old Chimpanzee Sites and the Origins of Percussive Stone Technology.”
(12.) Carvalho et al., “Chaînes Opératoires and Resource-Exploitation Strategies in Chimpanzee (Pan Troglodytes) Nut Cracking”; and Carvalho et al., “Tool-Composite Reuse in Wild Chimpanzees (Pan Troglodytes).”
(13.) McPherron et al., “Evidence for Stone-Tool-Assisted Consumption of Animal Tissues before 3.39 Million Years Ago at Dikika, Ethiopia.”
(14.) Harmand et al., “3.3-Million-Year-Old Stone Tools from Lomekwi 3, West Turkana, Kenya.”
(15.) Proffitt et al., “Wild Monkeys Flake Stone Tools.”
(16.) Donald K. Grayson, The Establishment of Human Antiquity (New York, NY: Academic Press, 1983).
(17.) Clive Gamble and Robert Kruszynski, “John Evans, Joseph Prestwich and the Stone That Shattered the Time Barrier,” Antiquity 83, no. 320 (2009): 461–475; and Gabriel de Mortillet, Classification Des Diverses Périodes de l’âGe de La Pierre, Par Gabriel de Mortillet: Extrait Du Compte Rendu Du Congrès International d’anthropologie et d’archéologie Préhistoriques 6me Session, Brux: 1872 (Typ. de Weizenbach, 1873).
(18.) Edward J. Wayland, “Rifts, Rivers, Rains and Early Man in Uganda,” The Journal of the Royal Anthropological Institute of Great Britain and Ireland 64 (1934): 333–352; W. W. Bishop, “Kafu Stratigraphy and Kafuan Artifacts,” South African Journal of Science 55, no. 5 (1959): 117–121; and John Desmond Clark, “The Natural Fracture of Pebbles from the Batoka Gorge, Northern Rhodesia, and Its Bearing on the Kafuan Industries of Africa,” Proceedings of the Prehistoric Society 24 (1958): 64–77.
(19.) Louis Seymour Bazett Leakey, Arthur T. Hopwood, and Hans Reck, “New Yields from the Oldoway Bone Beds, Tanganyika Territory,” Nature 128 (1931): 1075.
(20.) Louis Seymour Bazett Leakey, Stone Age Africa: An Outline of Prehistory in Africa (London, U.K.: Oxford University Press, H. Milford, 1936); Louis Seymour Bazett Leakey, “The Sequence of Stone Age Cultures in East Africa,” in Essays Presented to CG Seligman, ed. Edward E. Evans-Pritchard, Raymond Firth, Bronislaw Malinowski, and Isaac Schapera (London, U.K.: K. Paul, Trench, Trubner & Co., ltd., 1934), 143–146; Glynn L. Isaac, “Foundation Stones: Early Artefacts as Indicators of Activities and Abilities,” in Stone Age Prehistory: Studies in Memory of Charles McBurney, ed. Geoff N. Bailey and Paul Callow (Cambridge, U.K.: Cambridge University Press, 1986), 221–241; Kathy D. Schick and Nicholas Patrick Toth, Making Silent Stones Speak: Human Evolution and the Dawn of Technology (New York, NY: Simon and Schuster, 1994); and Nicholas Toth, “The Oldowan Reassessed: A Close Look at Early Stone Artifacts,” Journal of Archaeological Science 12, no. .2 (1985): 101–120.
(21.) Kenneth Oakley, “The Earliest Tool-Makers,” Antiquity 30, no. 117 (1956): 4–8; and Kenneth Page Oakley, “Man the Tool-Maker,” Proceedings of the Geologists’ Association 55, no. 2 (1944): 115–118.
(22.) John T. Robinson, “Adaptive Radiation in the Australopithecines and the Origin of Man,” in African Ecology and Human Evolution, ed. Francis Clark Howell and François Bourlière, vol. 36 (Chicago, IL: Aldine Pub. Co., 1963), 385–416; Sherwood L. Washburn, “Tools and Human Evolution,” Scientific American 203, no. 3 (1960): 62–75; and Charles Darwin, The Descent of Man; and Selection in Relation to Sex (London, U.K.: John Murray, 1871).
(23.) Oakley, “The Earliest Tool-Makers.”
(24.) Raymond A. Dart, Makapansgat Australopithecine Osteodontokeratic Culture (Pan-African Congress, 1955).
(25.) Charles Kimberlin Brain, The Hunters or the Hunted? An Introduction to African Cave Taphonomy (Texas, TX: University of Chicago Press, 1983).
(26.) Francesco d’Errico and Lucinda R. Backwell, “Possible Evidence of Bone Tool Shaping by Swartkrans Early Hominids,” Journal of Archaeological Science 30, no. 12 (2003): 1559–1576.
(27.) Louis Seymour Bazett Leakey, “A New Fossil Skull from Olduvai,” Nature 184, no. 4685 (1959): 491–493.
(28.) Louis Seymour Bazett Leakey, “Africa’s Contribution to the Evolution of Man,” The South African Archaeological Bulletin 16, no. 61 (1961): 3–7.
(29.) Louis Seymour Bazett Leakey, Phillip V. Tobias, and John Russell Napier, “A New Species of the Genus Homo from Olduvai Gorge,” Nature 202 (1964): 7–9.
(30.) Leakey, Tobias, and Napier, A New Species of the Genus Homo from Olduvai Gorge, 9.
(31.) John T. Robinson, “The Affinities of the New Olduvai Australopithecine,” Nature 186, no. 4723 (1960): 456–458; and Phillip V. Tobias, Olduvai Gorge, vol. 2 (Cambridge, U.K.: Cambridge University Press, 1967).
(32.) Glynn Isaac, “The Food-Sharing Behavior of Protohuman Hominids”, Scientific American 238, no. 4 (1978): 90–108.
(33.) Leakey, Tobias, and Napier, A New Species of the Genus Homo from Olduvai Gorge; René Bobe and Anna K. Behrensmeyer, “The Expansion of Grassland Ecosystems in Africa in Relation to Mammalian Evolution and the Origin of the Genus Homo,” Palaeogeography, Palaeoclimatology, Palaeoecology 207, no. 3 (2004): 399–420; and John W. K. Harris, “Cultural Beginnings: Plio-Pleistocene Archaeological Occurrences from the Afar, Ethiopia,” African Archaeological Review 1, no. 1 (1983): 3–31.
(34.) Harris, “Cultural Beginnings.”
(35.) Jane Goodall, “My Life among Wild Chimpanzees,” National Geographic 124 (1963): 273–308.
(36.) Jane Goodall, “Tool-Using and Aimed Throwing in a Community of Free-Living Chimpanzees,” Nature 201 (1964): 1264–1266.
(37.) Goodall, “Tool-Using and Aimed Throwing in a Community of Free-Living Chimpanzees,” 1265.
(38.) Jane Goodall, “Essays on Science and Society: Learning from the Chimpanzees: A Message Humans Can Understand,” Science 282, no. 5397 (1998): 2184–2185.
(39.) Oakley, “Man the Tool-Maker,” 115.
(40.) Kenneth P. Oakley, “Man the Skilled Tool-Maker,” Antiquity 43, no. 171 (1969): 222.
(41.) Andrew Whiten, Jane Goodall, William C. McGrew, Toshisada Nishida, Vernon Reynolds, Yukimaru Sugiyama, Caroline E. G. Tutin, Richard W. Wrangham, and Christophe Boesch, “Cultures in Chimpanzees,” Nature 399, no. 6737 (1999): 682–685.
(42.) Osamu Sakura and Tetsuro Matsuzawa, “Flexibility of Wild Chimpanzee Nut-Cracking Behavior Using Stone Hammers and Anvils: An Experimental Analysis,” Ethology 87, nos. 3–4 (1991): 237–248; George H. Whitesides, “Nut Cracking by Wild Chimpanzees in Sierra Leone, West Africa,” Primates 26, no. 1 (1985): 91–94; Bethan J. Morgan and Ekwoge E. Abwe, “Chimpanzees Use Stone Hammers in Cameroon,” Current Biology 16, no. 16 (2006): R632–R633; and Yukimaru Sugiyama and Jeremy Koman, “Tool-Using and -Making Behavior in Wild Chimpanzees at Bossou, Guinea,” Primates 20, no. 4 (1979): 513–524.
(43.) Sugiyama and Koman, “Tool-Using and -Making Behavior in Wild Chimpanzees at Bossou, Guinea,” 522.
(44.) Michel Brunet, Franck Guy, David Pilbeam, Hassane Taisso Mackaye, Andossa Likius, Djimdoumalbaye Ahounta, Alain Beauvilain, Cécile Blondel, Hervé Bocherens, Jean-Renaud Boisserie, Louis De Bonis, Yves Coppens, Jean Dejax, Christiane Denys, Philippe Duringer, Véra Eisenmann, Gongdibé Fanone, Pierre Fronty, Denis Geraads, Thomas Lehmann, Fabrice Lihoreau, Antoine Louchart, Adoum Mahamat, Gildas Merceron, Guy Mouchelin, Olga Otero, Pablo Pelaez Campomanes, Marcia Ponce De Leon, Jean-Claude Rage, Michel Sapanet, Mathieu Schuster, Jean Sudre, Pascal Tassy, Xavier Valentin, Patrick Vignaud, Laurent Viriot, Antoine Zazzo, and Christoph Zollikofer, “A New Hominid from the Upper Miocene of Chad, Central Africa,” Nature 418, no. 6894 (2002): 145–151.
(45.) Bobe and Behrensmeyer, “The Expansion of Grassland Ecosystems in Africa in Relation to Mammalian Evolution and the Origin of the Genus Homo”; and Nicholas Patrick Toth, Kathy Diane Schick, and Sileshi Semaw, The Oldowan: Case Studies into the Earliest Stone Age (Gosport, IN: Stone Age Institute Press, 2006).
(46.) Melissa A. Panger, Alison S. Brooks, Brian G. Richmond, and Bernard Wood, “Older than the Oldowan? Rethinking the Emergence of Hominin Tool Use,” Evolutionary Anthropology: Issues, News, and Reviews 11, no. 6 (2002): 235–245.
(47.) Panger et al., “Older than the Oldowan?,” 243; and Schick and Toth, Making Silent Stones Speak, 139.
(48.) Robert Foley, “Hominid Species and Stone-Tool Assemblages: How Are They Related?,” Antiquity 61, no. 233 (1987): 380–392; and Panger et al., “Older than the Oldowan?”
(49.) Panger et al., “Older than the Oldowan?”
(50.) Sileshi Semaw, Michael J. Rogers, Jay Quade, Paul R. Renne, Robert F. Butler, Manuel Dominguez-Rodrigo, Dietrich Stout, William S. Hart, Travis Pickering, Scott W. Simpson, “2.6-Million-Year-Old Stone Tools and Associated Bones from OGS-6 and OGS-7, Gona, Afar, Ethiopia,” Journal of Human Evolution 45, no. .2 (2003): 169–177; and Sileshi Semaw, Paul Renne, John W. K. Harris, Craig S. Feibel, Raymond L. Bernor, Nardos Fesseha, and Kenneth Mowbray, “2.5-Million-Year-Old Stone Tools from Gona, Ethiopia,” Nature 385, no. 6614 (1997): 333–336.
(51.) Susan C. Antón, Richard Potts, and Leslie C. Aiello, “Evolution of Early Homo: An Integrated Biological Perspective,” Science 345, no. 6192 (2014): 1236828; Frederick E. Grine, John G. Fleagle, and Richard E. Leakey, The First Humans: Origin and Early Evolution of the Genus Homo (Dordrecht: Springer Science & Business Media, 2009); Andrew Hill, Steven Ward, Alan Deino, Garniss Curtis, and Robert Drake, “Earliest Homo,” Nature 355, no. 6362 (1992): 719–722; William H. Kimbel, Robert C. Walter, Donald C. Johanson, Kaye E. Reed, James L. Aronson, Zelalem Assefa, Curtis W. Marean, Gerald G. Eck, René Bobe, Erella Hovers, and Yoel Rak, “Late Pliocene Homo and Oldowan Tools from the Hadar Formation (Kada Hadar Member), Ethiopia,” Journal of Human Evolution 31, no. 6 (1996): 549–561; and Friedemann Schrenk, Timothy G. Bromage, Christian G. Betzler, Uwe Ring, and Yusuf M. Juwayeyi, “Oldest Homo and Pliocene Biogeography of the Malawi Rift,” Nature 365, no. 6449 (1993): 833–836.
(52.) Semaw et al., “2.6-Million-Year-Old Stone Tools and Associated Bones from OGS-6 and OGS-7, Gona, Afar, Ethiopia”; and Dietrich Stout, Sileshi Semaw, Michael J. Rogers, and Dominique Cauche, “Technological Variation in the Earliest Oldowan from Gona, Afar, Ethiopia,” Journal of Human Evolution 58, no. 6 (2010): 474–491.
(53.) Anne Delagnes and Hélène Roche, “Late Pliocene Hominid Knapping Skills: The Case of Lokalalei 2C, West Turkana, Kenya,” Journal of Human Evolution 48, no. 5 (2005): 435–472; and Hélène Roche, Anne Delagnes, J-P. Brugal, Craig Feibel, Mzalendo Kibunjia, Vincent Mourre, and P-J. Texier, “Early Hominid Stone Tool Production and Technical Skill 2.34 Myr Ago in West Turkana, Kenya,” Nature 399, no. 6731 (1999): 57–60.
(54.) Dietrich Stout, Jay Quade, Sileshi Semaw, Michael J. Rogers, and Naomi E. Levin, “Raw Material Selectivity of the Earliest Stone Toolmakers at Gona, Afar, Ethiopia,” Journal of Human Evolution 48, no. 4 (2005): 365–380.
(55.) Shannon P. McPherron, Zeresenay Alemseged, Curtis W. Marean, Jonathan G. Wynn, Denné Reed, Denis Geraads, René Bobe, and Hamdallah A. Béarat, “Evidence for Stone-Tool-Assisted Consumption of Animal Tissues before 3.39 Million Years Ago at Dikika, Ethiopia,” Nature 466, no. 7308 (2010): 857–860; and Jessica C. Thompson, Shannon P. McPherron, René Bobe, Denné Reed, W. Andrew Barr, Jonathan G. Wynn, Curtis W. Marean, Denis Geraads, and Zeresenay Alemseged, “Taphonomy of Fossils from the Hominin-Bearing Deposits at Dikika, Ethiopia,” Journal of Human Evolution 86 (2015): 112–135.
(56.) Though, see Manuel Domínguez-Rodrigo, Travis Rayne Pickering, and Henry T. Bunn, “Experimental Study of Cut Marks Made with Rocks Unmodified by Human Flaking and Its Bearing on Claims of 3.4-Million-Year-Old Butchery Evidence from Dikika, Ethiopia,” Journal of Archaeological Science 39, no. 2 (2012): 205–214.
(57.) Sonia Harmand, Jason E. Lewis, Craig S. Feibel, Christopher J. Lepre, Sandrine Prat, Arnaud Lenoble, Xavier Boës, Rhonda L. Quinn, Michel Brenet, Adrian Arroyo, Nicholas Taylor, Sophie Clément, Guillaume Daver, Jean-Philip Brugal, Louise Leakey, Richard A. Mortlock, James D. Wright, Sammy Lokorodi, Christopher Kirwa, Dennis V. Kent, and Hélène Roche, “3.3-Million-Year-Old Stone Tools from Lomekwi 3, West Turkana, Kenya,” Nature 521, no. 7552 (2015): 310–315; and Erella Hovers, “Archaeology: Tools Go Back in Time,” Nature 521, no. 7552 (2015): 294–295.
(58.) Brian Villmoare, Brian, William H. Kimbel, Chalachew Seyoum, Christopher J. Campisano, Erin N. DiMaggio, John Rowan, David R. Braun, J. Ramón Arrowsmith, and Kaye E. Reed, “Early Homo at 2.8 Ma from Ledi-Geraru, Afar, Ethiopia,” Science 347, no. 6228 (2015): 1352–1355; Harris, “Cultural Beginnings”; and Leakey, Tobias, and Napier, A New Species of the Genus Homo from Olduvai Gorge.
(59.) Jason E. Lewis and Sonia Harmand, “An Earlier Origin for Stone Tool Making: Implications for Cognitive Evolution and the Transition to Homo,” Philosophical Transactions of the Royal Society B 371, no. 1698 (2016): 20150233.
(60.) Michael Haslam, R. Adriana Hernandez-Aguilar, Tomos Proffitt, Adrian Arroyo, Tiago Falótico, Dorothy Fragaszy, Michael Gumert, John W. K. Harris, Michael Huffman, Ammie Kalan, Suchinda Malaivijitnond, Tetsuro Matsuzawa, William McGrew, Eduardo Ottoni, Alejandra Pascual-Garrido, Alex Piel, Jill Pruetz, Caroline Schuppli, Fiona Stewart, Amanda Tan, Elisabetta Visalberghi, and Lydia Luncz, “Primate Archaeology Evolves,” Nature Ecology & Evolution 1, no. 10 (2017): 1431.
(61.) Geza Teleki, “Chimpanzee Subsistence Technology: Materials and Skills,” Journal of Human Evolution 3, no. 6 (1974): 575IN13585–584IN16594; Thomas Wynn and William C. McGrew, “An Ape’s View of the Oldowan,” Man 24 (1989): 383–398; and Nicholas Toth, Kathy D. Schick, E. Sue Savage-Rumbaugh, Rose A. Sevcik, and Duane M. Rumbaugh, “Pan the Tool-Maker: Investigations into the Stone Tool-Making and Tool-Using Capabilities of a Bonobo (Pan Paniscus),” Journal of Archaeological Science 20, no. 1 (1993): 81–91.
(62.) Frédéric Joulian, “Comparing Chimpanzee and Early Hominid Techniques: Some Contributions to Cultural and Cognitive Question,” in Modelling the Early Human Mind, ed. Paul A. Mellars and Kathleen A. Gibson (McDonald Institute for Archaeological Research, University of Cambridge, 1996), 173–189; Frédéric Joulian, “Culture and Material Culture in Chimpanzees and Early Hominids,” Current Primatology. Strasbourg, Université Louis-Pasteur 2 (1994): 397–404; and Julio Mercader, Melissa Panger, and Christophe Boesch, “Excavation of a Chimpanzee Stone Tool Site in the African Rainforest,” Science 296, no. 5572 (2002): 1452–1455.
(63.) Mercader, Panger, and Boesch, “Excavation of a Chimpanzee Stone Tool Site in the African Rainforest.”
(64.) Julio Mercader, Huw Barton, Jason Gillespie, Jack Harris, Steven Kuhn, Robert Tyler, and Christophe Boesch, “4,300-Year-Old Chimpanzee Sites and the Origins of Percussive Stone Technology,” Proceedings of the National Academy of Sciences 104, no. 9 (2007): 3043–3048; and William Clement McGrew, Chimpanzee Material Culture: Implications for Human Evolution (Cambridge, U.K.: Cambridge University Press, 1992).
(65.) Haslam et al., “Primate Archaeology Evolves,” 1432.
(66.) Mercader et al., “4,300-Year-Old Chimpanzee Sites and the Origins of Percussive Stone Technology.”
(67.) Lydia V. Luncz, Roger Mundry, and Christophe Boesch, “Evidence for Cultural Differences between Neighboring Chimpanzee Communities,” Current Biology 22, no. 10 (2012): 922–926; Michael Haslam, “Towards a Prehistory of Primates,” Antiquity 86, no. 332 (2012): 299–315; Susana Carvalho, Cláudia Sousa, and Tetsuro Matsuzawa, “New Nut-Cracking Sites in Diecké Forest, Guinea: An Overview of the Surveys,” Pan Africa News 14, no. 1 (2007): 11–13; William C. McGrew, Takuya Matsumoto, Michio Nakamura, Caroline A. Phillips, and Fiona A. Stewart, “Experimental Primate Archaeology: Detecting Stone Handling by Japanese Macaques (Macaca Fuscata),” Lithic Technology 39, no. 2 (2014): 113–121; Susana Carvalho, Eugénia Cunha, Cláudia Sousa, and Tetsuro Matsuzawa, “Chaînes Opératoires and Resource-Exploitation Strategies in Chimpanzee (Pan Troglodytes) Nut Cracking,” Journal of Human Evolution 55, no. .1 (2008): 148–163; Michael Haslam, Adriana Hernandez-Aguilar, Victoria Ling, Susana Carvalho, Ignacio de La Torre, April DeStefano, Andrew Du, Bruce Hardy, Jack Harris, Linda Marchant, Tetsuro Matsuzawa, William McGrew, Julio Mercader, Rafael Mora, Michael Petraglia, Hélène Roche, Elisabetta Visalberghi, and Rebecca Warren, “Primate Archaeology,” Nature 460, no. 7253 (2009): 339–344; Lydia V. Luncz, Roman M. Wittig, and Christophe Boesch, “Primate Archaeology Reveals Cultural Transmission in Wild Chimpanzees (Pan Troglodytes Verus),” Philosophical Transactions of the Royal Society of London B 370, no. 1682 (2015): 20140348; and Susana Carvalho, Dora Biro, William C. McGrew, and Tetsuro Matsuzawa, “Tool-Composite Reuse in Wild Chimpanzees (Pan Troglodytes): Archaeologically Invisible Steps in the Technological Evolution of Early Hominins?,” Animal Cognition 12, no. 1 (2009): 103–114.
(68.) Suchinda Malaivijitnond, Chariya Lekprayoon, Nontivich Tandavanittj, Somsak Panha, Cheewapap Cheewatham, and Yuzuru Hamada, “Stone-Tool Usage by Thai Long-Tailed Macaques (Macaca Fascicularis),” American Journal of Primatology 69, no. 2 (2007): 227–233; and Dorothy Fragaszy, Patricia Izar, Elisabetta Visalberghi, Eduardo B. Ottoni, and Marino Gomes de Oliveira, “Wild Capuchin Monkeys (Cebus Libidinosus) Use Anvils and Stone Pounding Tools,” American Journal of Primatology 64, no. 4 (2004): 359–366.
(69.) Michael Haslam, Lydia Luncz, Alejandra Pascual-Garrido, Tiago Falótico, Suchinda Malaivijitnond, and Michael Gumert, “Archaeological Excavation of Wild Macaque Stone Tools,” Journal of Human Evolution 96, no. 13 (2016): 4e138; Tomos Proffitt, Lydia Luncz, Tiago Falótico, Eduardo B. Ottoni, Ignacio de la Torre, and Michael Haslam, “Wild Monkeys Flake Stone Tools,” Nature 539 (2016): 85–88; and Michael Haslam, Lydia V. Luncz, Richard A. Staff, Fiona Bradshaw, Eduardo B. Ottoni, and Tiago Falótico, “Pre-Columbian Monkey Tools,” Current Biology 26, no. 13 (2016): R521–R522.
(70.) Haslam et al., “Primate Archaeology”; Luncz, Wittig, and Boesch, “Primate Archaeology Reveals Cultural Transmission in Wild Chimpanzees (Pan Troglodytes Verus).”
(71.) Christian Rutz and James J. H. St. Clair, “The Evolutionary Origins and Ecological Context of Tool Use in New Caledonian Crows,” Behavioural Processes 89, no. 2 (2012): 153–165; Eric M. Patterson and Janet Mann, “The Ecological Conditions That Favor Tool Use and Innovation in Wild Bottlenose Dolphins (Tursiops Sp.),” PLoS One 6, no. 7 (2011): e22243; Robert W. Shumaker, Kristina R. Walkup, and Benjamin B. Beck, Animal Tool Behavior: The Use and Manufacture of Tools by Animals (Baltimore: JHU Press, 2011); Whiten et al., “Cultures in Chimpanzees”; Carel P. van Schaik, Elizabeth A. Fox, and A. F. Sitompul, “Manufacture and Use of Tools in Wild Sumatran Orangutans,” Naturwissenschaften 83, no. 4 (1996): 186–188; Massimo Mannu and Eduardo B. Ottoni, “The Enhanced Tool-Kit of Two Groups of Wild Bearded Capuchin Monkeys in the Caatinga: Tool Making, Associative Use, and Secondary Tools,” American Journal of Primatology 71, no. 3 (2009): 242–251; Gavin R. Hunt, “Manufacture and Use of Hook-Tools by New Caledonian Crows,” Nature 379, no. 6562 (1996): 249–251; and Gavin R. Hunt and Russell D. Gray, “Diversification and Cumulative Evolution in New Caledonian Crow Tool Manufacture,” Proceedings of the Royal Society of London B: Biological Sciences 270, no. 1517 (2003): 867–874.
(72.) Rolian Campbell and Susana Carvalho, “Tool Use and Manufacture in the Last Common Ancestor of Pan and Homo,” in Chimpanzees and Human Evolution, ed. Martin N. Muller, Richard W. Wrangham, and David R. Pilbeam (Cambridge, MA: Harvard University Press, 2017).
(73.) Haslam et al., “Primate Archaeology.”
(74.) Proffitt et al., “Wild Monkeys Flake Stone Tools.”
(75.) Hélène Roche, Robert J. Blumenschine, and John J. Shea, “Origins and Adaptations of Early Homo: What Archeology Tells Us,” in The First Humans: Origin and Early Evolution of the Genus Homo, ed. Frederick E. Grine, John G. Fleagle, and Richard E. Leakey (Dordrecht: Springer Science & Business Media, 2009), 135–147.
(77.) Proffitt et al., “Wild Monkeys Flake Stone Tools.”
(78.) Harmand et al., “3.3-Million-Year-Old Stone Tools from Lomekwi 3, West Turkana, Kenya.”
(79.) Though, see Proffitt et al., “Wild Monkeys Flake Stone Tools.”
(80.) Harmand et al., “3.3-Million-Year-Old Stone Tools from Lomekwi 3, West Turkana, Kenya.”
(81.) McPherron et al., “Evidence for Stone-Tool-Assisted Consumption of Animal Tissues before 3.39 Million Years Ago at Dikika, Ethiopia”; and Domínguez-Rodrigo, Pickering, and Bunn, “Experimental Study of Cut Marks Made with Rocks Unmodified by Human Flaking and Its Bearing on Claims of 3.4-Million-Year-Old Butchery Evidence from Dikika, Ethiopia.”
(82.) Panger et al., “Older than the Oldowan?”
(83.) Mary W. Marzke, “Precision Grips, Hand Morphology, and Tools,” American Journal of Physical Anthropology 102, no. 1 (1997): 91–110; Mary W. Marzke, “Joint Functions and Grips of the Australopithecus Afarensis Hand, with Special Reference to the Region of the Capitate,” Journal of Human Evolution 12, no. 2 (1983): 197–211; and Panger et al., “Older than the Oldowan?”
(84.) Marzke, “Precision Grips, Hand Morphology, and Tools.”
(85.) Mathieu Domalain, Anne Bertin, and Guillaume Daver, “Was Australopithecus Afarensis able to make the lomekwian stone tools? Towards a realistic biomechanical simulation of hand force capability in fossil hominins and new insights on the role of the fifth digit,” Comptes Rendus Palevol 16, no. 5–6 (2017): 572–584.
(86.) Matthew M. Skinner, Nicholas B. Stephens, Zewdi J. Tsegai, Alexandra C. Foote, N. Huynh Nguyen, Thomas Gross, Dieter H. Pahr, Jean-Jacques Hublin, and Tracy L. Kivell, “Human-like Hand Use in Australopithecus Africanus,” Science 347, no. 6220 (2015): 395–399.
(87.) Though, see Sergio Almécija, Ian J. Wallace, Stefan Judex, David M. Alba, and Salvador Moyà-Solà, “Comment on ‘Human-like Hand Use in Australopithecus Africanus’,” Science 348, no. 6239 (2015): 1101.
(88.) Panger et al., “Older than the Oldowan?”
(89.) Meave G. Leakey, Fred Spoor, Frank H. Brown, Patrick N. Gathogo, Christopher Kiarie, Louise N. Leakey, and Ian McDougall, “New Hominin Genus from Eastern Africa Shows Diverse Middle Pliocene Lineages,” Nature 410, no. 6827 (2001): 433–440; and Bernard Wood and Meave Leakey, “The Omo-Turkana Basin Fossil Hominins and Their Contribution to Our Understanding of Human Evolution in Africa,” Evolutionary Anthropology: Issues, News, and Reviews 20, no. 6 (2011): 264–292.
(90.) Yohannes Haile-Selassie, Luis Gibert, Stephanie M. Melillo, Timothy M. Ryan, Mulugeta Alene, Alan Deino, Naomi E. Levin, Gary Scott, and Beverly Z. Saylor, “New Species from Ethiopia Further Expands Middle Pliocene Hominin Diversity,” Nature 521, no. 7553 (2015): 483–488.
(91.) Fred Spoor, “Palaeoanthropology: The Middle Pliocene Gets Crowded,” Nature 521, no. 7553 (2015): 432–433.
(92.) John Napier, “Fossil Hand Bones from Olduvai Gorge,” Nature 196 (1962): 409–411; and Campbell and Carvalho, “Tool Use and Manufacture in the Last Common Ancestor of Pan and Homo.”
(93.) Panger et al., “Older than the Oldowan?”
(94.) Goodall, “Tool-Using and Aimed Throwing in a Community of Free-Living Chimpanzees”; Jill D. Pruetz and Paco Bertolani, “Savanna Chimpanzees, Pan Troglodytes Verus, Hunt with Tools,” Current Biology 17, no. 5 (2007): 412–417; Sugiyama and Koman, “Tool-Using and-Making Behavior in Wild Chimpanzees at Bossou, Guinea”; Christophe Boesch, Josephine Head, and Martha M. Robbins, “Complex Tool Sets for Honey Extraction among Chimpanzees in Loango National Park, Gabon,” Journal of Human Evolution 56, no. 6 (2009): 560–569; William Clement McGrew, The Cultured Chimpanzee: Reflections on Cultural Primatology (Cambridge, U.K.: Cambridge University Press, 2004); and Campbell and Carvalho, “Tool Use and Manufacture in the Last Common Ancestor of Pan and Homo.”
(95.) Foley, “Hominid Species and Stone-Tool Assemblages”; Panger et al., “Older than the Oldowan?”; and Campbell and Carvalho, “Tool Use and Manufacture in the Last Common Ancestor of Pan and Homo.”
(96.) John J. Shea, Stone Tools in Human Evolution: Behavioral Differences Among Technological Primates (New York, NY: Cambridge University Press, 2016).
(97.) Harris, “Cultural Beginnings”; Leakey, Tobias, and Napier, A New Species of the Genus Homo from Olduvai Gorge; and Haslam et al., “Primate Archaeology.”
(98.) Shumaker, Walkup, and Beck, Animal Tool Behavior; and Proffitt et al., “Wild Monkeys Flake Stone Tools.”
(99.) Harmand et al., “3.3-Million-Year-Old Stone Tools from Lomekwi 3, West Turkana, Kenya.”
(100.) Haslam et al., “Primate Archaeology Evolves.”
(101.) Mercader et al., “4,300-Year-Old Chimpanzee Sites and the Origins of Percussive Stone Technology.”
(102.) Panger et al., “Older than the Oldowan?”; and Shea, Stone Tools in Human Evolution.