COMMENTARY

Searchingfortheemergenceofstonetoolmakingin eastern Africa COMMENTARY Ignacio de la Torrea,1

Modern rely entirely on for their complementing the indirect evidence of stone subsistence, and the interaction between technolog- use proposed for Dikika. ical and biological adaptations has played a key role in While the evidence >3 Ma is not exempt of contro- the evolution of our lineage. When exactly technology versy (see recent reviews in refs. 8 and 9), Braun et al. (1) emerged in the fossil record and thus started to shape compare the assemblage of BD 1 with that of evolution has appealed to researchers since and conclude that differences are significant the beginnings of as a discipline enough to maintain a separation between the Lomekwian and, as Braun et al. (1) show in PNAS, is still today a culture—the name given to the new discovery in source of important discoveries. (7)—and the , for which BD 1 is now the earliest Our closest relatives at present, the , site. Acceptance of this scenario would imply reconsider- have a rich material culture that varies geographically ing some long-standing paradigms in paleoanthropology. (2) and comprises the use of a wide variety of , For instance, an influential view established co- including leaves, clubs, sticks, stones, and others. Al- alescence among the emergence of the genus , though our ancestors most likely also used an array of the earliest stone tools, and the climatic change toward organic materials, stones are usually the only artifacts aridification at 2.9 to 2.6 Ma (10). The earliest fossils of preserved in the record and, therefore, are key to Homo have been recently discovered in the same area trace the emergence of technology in evolu- of Ledi-Geraru as the Oldowan site reported by Braun tion. For nearly a century, the Oldowan defined by et al. (1) and, although such human remains are Louis Leakey (3) at in has 200,000 y older (11) than BD 1, given the fragmen- remained the most solid evidence of earliest stone tary character of the paleoanthropological record, tool making in our lineage. Originally thought to be they do not necessarily challenge the scenario as- around half a million years old, the age of the Oldowan sociating climate changewithspeciationand has been pushed back steadily (4) since the 1960s, with cultural responses. Accepting the validity of archaeo- the Gona sites in at 2.58 million years ago (Ma) logical evidence at ∼3.4 Ma, however, changes sub- being, until Braun et al.’s (1) discovery, the oldest evi- stantially the scenario and decouples such association, dence of this technology (5). The new site of Bokol as no significant climate changes have been detected in Dora 1 (BD 1) at the paleoanthropological area of Ledi- that particular time span, and hominins in both the Dikika Geraru, also in Ethiopia, is slightly older than Gona at ( afarensis)andLomekwi(Kenyanthro- 2.61 to 2.58 Ma (1) and contributes to establishing pus platyops) areas are less derived than early Homo. ∼2.6 Ma as a firm date for the earliest Oldowan. Another intriguing implication is the ∼0.7-Ma gulf But the Oldowan might have not been the first between Lomekwi and BD 1. Basic lithic archaeologically visible technology in the paleoan- such as the Lomekwian and the Oldowan may have thropological record. In recent years, two discoveries— been discovered and then disappeared and reinvented Dikika and Lomekwi—have sparked fresh debate about again in the course of (12)—in a frag- the potential existence of technologies further mented sequence of cultural gains and losses that back in time, at ∼3.4 Ma. At Dikika, Ethiopia, some could potentially explain why no archaeological evidence bones bear traces interpreted as cut marks (6), which is found between 3.3 and 2.6 Ma. In my view, how- would evidence that hominins were using ever, a scenario of independent inventions, disap- stone tools to process carcasses. Although no pearance, and rediscovery of stone tool flaking does stone tools have yet been reported in Dikika, the site not fit with the evidence available for the Oldowan of Lomekwi 3 (Kenya) has yielded several lithic artifacts record from 2.6 Ma onward, because the tight chronological that are attributed to 3.3-Ma sediments (7), thus clustering among Ledi-Geraru (1), Gona (5), and all of

aInstitute of , University College , London WC1H 0PY, Author contributions: I.d.l.T. wrote the paper. The author declares no conflict of interest. Published under the PNAS license. See companion article on page 11712. 1Email: [email protected]. Published online June 4, 2019.

www.pnas.org/cgi/doi/10.1073/pnas.1906926116 PNAS | June 11, 2019 | vol. 116 | no. 24 | 11567–11569 Downloaded by guest on October 1, 2021 Fig. 1. Earliest archaeological sites in eastern Africa (Upper) and techniques used to produce sharp-edged stone flakes (Lower). Block-on-block technique: the core is struck against a stationary anvil. Bipolar technique: a core resting over a stationary anvil is struck with a . Freehand technique: a handheld core is knocked off with a hammerstone.

the eastern African sites that follow in the temporal sequence And which are those patterns? All early archaeological assem- (Fig. 1) indicates continuity in the archaeological record and blages contain clusters of stone tools in lake margins or riverine consistency in the patterns involved. settings, which often correspond to more open environments than

11568 | www.pnas.org/cgi/doi/10.1073/pnas.1906926116 de la Torre Downloaded by guest on October 1, 2021 those inhabited by earlier hominins and the majority of nonhuman for now, it might be safest to highlight that there is indeed tech- living . Most early archaeological assemblages also yield nological variability among the earliest Oldowan sites, without fossils, although in many, like the one reported by Braun et al. (1), their attributing time trends to such variability. association with lithic artifacts is only spatial and not necessarily con- From that perspective, the overarching features shared by textual (e.g., in the form of anthropogenic marks on fossils demonstrat- most of the earliest sites in Fig. 1 would be the clustering of ing an effective link between stone tools and bones). In some other artifacts (and often also bones) obtained through conchoidal frac- assemblages, lithics are abundant while fossils are not present (Fig. 1), ture. Mastering of the has long stood as a but their absence may be due to taphonomic bias against bone pres- defining character of human technology (17), and clustering ervation. In some rare—and controversial (8)—instances, reported cut has been associated with behavioral changes by early hominins marks in bones without a clear association with lithic assemblages (e.g., that enable archaeological visibility of their activities (18). Dikika and Bouri) serve to emphasize the main purpose of early stone But are these features truly unique to hominins and their tools, which is deemed to be the production of cutting edges (13), earliest archaeological sites? Findings in the brand-new discipline most likely to aid early humans accessing carcasses. of primate archaeology (19) seem to say otherwise; for example, In addition to producing cutting edges, stones were most likely nut-cracking activities are now observed to produce used in other tasks; percussive activities involved in processing significant concentrations of artifacts, in many ways mimicking organic materials are common among various primates (14) and spatial patterns typical of the record (20). Even more may potentially have preceded stone tool during the surprisingly, capuchin monkeys have recently been shown to ob- initial stages of hominins’ exploitation of animal resources (9). tain conchoidally fractured flakes through recurrent use of ham- However, most early archaeological sites from Fig. 1 contain few merstones (21). Even though capuchins produce such lithic battered artifacts other than those related to flake production, assemblages unintentionally, the technological behavior of these with such production being the primary goal in all assemblages. distant relatives in our evolutionary lineage indicates that large As Braun et al. (1) emphasize, nonetheless, technological variabil- brains and humanlike hands are not, after all, indispensable re- ity associated with flake production may have been considerable. quirements for stone knapping. When the Gona assemblages were thought to be the earliest Primate archaeology findings are blurring the line of what is evidence of stone tool knapping, researchers were puzzled about exclusive to early human technology and opening new perspec- the high quality of flaking production, as parsimony dictated that tives into the comparative analysis of archaeological assemblages there would be an incremental process of skill acquisition through made by hominins and nonhuman primates. It now seems clear the Oldowan. Braun et al. (1) indicate that the slightly older as- that has appeared independently in various semblage of BD 1 is also slightly less technologically sophisticated lineages of primates and may potentially have been discovered than Gona, which makes it tempting to return to a gradualist view and disappeared several times through the Pliocene and Early of technological evolution during the Oldowan. As shown in Fig. ; by pushing the emergence of the Oldowan a bit 1, 3 main techniques were employed to produce flakes in the further back in time, Ledi-Geraru (1) contributes both to exploring earliest archaeological sites. The block-on-block technique has the roots of lithic technology and to characterizing the internal only been reported in Lomekwi, involves the production of much variability of early stone tool assemblages. It is hardly an exagger- larger flakes than the ∼2- to 5-cm-long products typical of the ation to state that today, the field remains as vibrant as when Oldowan, and is one of the features put forward to differentiate Leakey (3) defined the Oldowan nearly a century ago. the Lomekwian from the Oldowan (7). However, bipolar and free- hand techniques are found across the early Oldowan record (Fig. Acknowledgments 1), and the quality of flaking products may be strongly influenced I thank Dongdong Ma and Xin Ding for their help in preparing Fig. 1. I.d.l.T.’sre- by raw-material constrains (15) and site particularities (16). Thus, search was supported by the European Research Council (Starting Grant 283366).

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