A 1.4-million--old bone handaxe from Konso, , shows advanced tool in the early

Katsuhiro Sanoa, Yonas Beyeneb,c, Shigehiro Katohd, Daisuke Koyabue, Hideki Endof, Tomohiko Sasakig, Berhane Asfawh, and Gen Suwaf,1

aCenter for Northeast Asian Studies, Tohoku University, Aoba-ku, Sendai 980-8576, Japan; bAssociation for Conservation of Culture Hawassa, Addis Ababa, Ethiopia; cFrench Center for Ethiopian Studies, Addis Ababa, Ethiopia; dDivision of Natural History, Hyogo Museum of Nature and Human Activities, Yayoigaoka, Sanda 669-1546, Japan; eJockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon 999077, Hong Kong; fThe University Museum, The University of Tokyo, Tokyo 113-0033, Japan; gKyoto University Museum, Kyoto University, Kyoto 606-8501, Japan; and hRift Valley Research Service, Addis Ababa, Ethiopia

Contributed by Gen Suwa, June 1, 2020 (sent for review April 6, 2020); reviewed by John A. J. Gowlett and Nicholas Toth) In the past decade, the early Acheulean before 1 Mya has been a A prepared core technology, including roughly executed cen- focus of active research. Acheulean lithic assemblages have been tripetal core preparation, was practiced in producing early shown to extend back to ∼1.75 Mya, and considerable advances in Acheulean large cutting tools (LCTs) at Peninj at 1.5 to 1.1 Mya core reduction are seen by 1.5 to 1.4 Mya. Here (30), Melka Kunture at ∼1.5 to 0.85 Mya (31), EF-HR of Olduvai we report a bifacially flaked bone fragment (maximum dimension Gorge at ∼1.4 Mya (32), and Konso at ∼1.4 to 1.25 Mya (14, 15). ∼13 cm) of a hippopotamus femur from the ∼1.4 Mya sediments In addition, a striking of the Konso ∼1.4 to 1.25 Mya as- of the Konso Formation in southern Ethiopia. The large number of semblages is the occurrence of the Kombewa method (15) nearly flake scars and their distribution pattern, together with the high half a million y earlier than previously known (31). This is a frequency of cone fractures, indicate anthropogenic flaking into specialized technique that produces flakes with two ventral faces, handaxe-like form. Use-wear analyses show quasi-continuous alter- inferring predetermination of blank shape. The nate microflake scars, wear polish, edge rounding, and striae seen in the Konso ∼1.4 to 1.25 Mya assemblages also show ad- ∼ patches along an 5-cm-long edge toward the handaxe tip. The vanced workmanship in tip thinning, reduced edge sinuosity, and striae run predominantly oblique to the edge, with some perpen- increased cross-section and planform symmetry. However, there dicular, on both the cortical and inner faces. The combined evidence is is high interassemblage variability at Konso (14, 15) and among consistent with the use of this bone artifact in longitudinal motions, the other East African early Acheulean sites of this time period such as in cutting and/or sawing. This bone handaxe is the oldest (3, 13, 30–33). known extensively flaked example from the Early . De- At Konso, the ∼0.85 Mya Acheulean assemblages show fur- spite scarcity of -shaped bone tools, its presence at Konso ther technological innovation. A substantial reduction of LCT shows that sophisticated flaking was practiced by ∼1.4 Mya, thickness was routinely attained by detaching thinner blanks (or not only on a range of lithic materials, but also occasionally on by using thin cobbles) and by shallower invasive flaking of the bone, thus expanding the documented technological repertoire of African Early Pleistocene . blank surfaces. These additional levels of advanced flaking technology enabled achievement of the 3D symmetry of the Acheulean technology | bone handaxe | use-wear | core preparation | LCTs (14, 15). Other assemblages in the 0.8 to 1.0 Mya time Early Pleistocene period known to exhibit LCTs with advanced planform and

Significance he Acheulean is the most widespread technolog- Tical tradition in the Old World, characterized by handaxes, cleavers, and sometimes picks, as well as a range of other smaller We report a rare example of a 1.4-million-y-old large bone frag- artifacts (1–9). An additional important hallmark of the Acheulean ment shaped into handaxe-like form. This derives from the Konso Formation in southern Ethiopia, where abundant early lithic technology is use of large flake blanks accompanied by hier- – Acheulean stone artifacts show considerable technological pro- archical and spatial structuring of tool production (2, 7, 8, 10 13). gression between ∼1.75 and <1.0 Mya. Technological analysis of Large flake blanks were not used in the preceding and are the bone tool indicates intensive anthropogenic shaping. Edge ∼ first seen in the 1.75 to 1.6 Mya East African Acheulean as- damage, polish, and striae patterns are consistent with use in semblages at Konso in Ethiopia (14, 15), west of in longitudinal motions, such as in butchering. The discovery of this (16, 17), in (18–20), and Gona in bone handaxe shows that advanced flaking technology, practiced Ethiopia (7, 21). Many researchers consider the recurrent, if not at Konso on a variety of lithic materials, was also applied to bone, preconceived, form of the Acheulean stone tools to be related to thus expanding the known technological repertoire of African advanced cognition of the makers relative to earlier Homo (7, 10, Early Pleistocene Homo. 12, 22–26). The Acheulean is also known as a long-term lithic tradition (duration of >1.5 million y) and shows considerable Author contributions: K.S., Y.B., S.K., B.A., and G.S. designed research; K.S., Y.B., S.K., D.K., H.E., T.S., B.A., and G.S. performed research; K.S., Y.B., S.K., B.A., and G.S. analyzed data; conservatism until diversification in the late Acheulean (4, 6, 27). and K.S., Y.B., S.K., B.A., and G.S. wrote the paper. This has in turn been interpreted to stem from the comparatively Reviewers: J.A.J.G., University of Liverpool; and N.T., Institute. restricted capacities of the manufacturers in hierarchical per- The authors declare no competing interest. ception (12), working memory (28), and/or cognitive fluidity for Published under the PNAS license. technological invention (29) relative to later Homo. However, 1To whom correspondence may be addressed. Email: [email protected]. technomorphological investigations of East African early Acheulean This article contains supporting information online at https://www.pnas.org/lookup/suppl/ assemblages indicate considerable temporal advances between ∼1.75 doi:10.1073/pnas.2006370117/-/DCSupplemental. and 0.8 Mya in multiple technological aspects, as summarized below. First published July 13, 2020.

www.pnas.org/cgi/doi/10.1073/pnas.2006370117 PNAS | August 4, 2020 | vol. 117 | no. 31 | 18393–18400 Downloaded by guest on September 25, 2021 biconvex cross-sectional symmetry are from Melka Kunture in much later in these regions. This may be because they were Ethiopia (31), several sites in Kenya ( Members 6/7, produced only rarely, as was the case at Olduvai Gorge Beds II Kilombe, Kariandusi, and possibly Isenya) (2, 34–37), and Bed to IV (3, 38). Except at Castel di Guido in Italy (64), only single IV of the Olduvai Gorge (37, 38). From tuff correlation with or two bone handaxes have been reported from these sites, Olorgesallie Member 4, Isenya has recently been considered to mostly made from elephant bones. Due to the scarcity of bone be as old as 0.97 My (39). However, this was based on major handaxes as well to as the remarkable preference for elephant element compositions of a single tuff and this is not conclusive. bones, ritual or symbolic purposes rather than functional pur- Biochronological assessments (40) suggest that Isenya is broadly poses have been suggested, especially in Europe (61). coeval with site HEB of Olduvai Bed IV at >0.8 Mya, an age that As with Olduvai Gorge Bed II, at Konso, only one bone remains an alternative possibility. The scarce hominin fossil re- specimen exhibited a clear handaxe-like form, whereas a con- cord of this time period (31, 41–47) needs to be substantially siderable number of bones were modified (65). Therefore, it is improved to unravel how the emergence of enhanced LCT important to exclude the possibility that taphonomic processes technology related to the poorly understood transition of late produced the handaxe-like long bone fragment at Konso. Based to Homo rhodensiensis/heidelbergensis sensu lato. on a technological flake scar analysis, we examined whether or From the ∼1.4 Mya time horizon of the Konso Formation (SI not the bifacially flaked long bone exhibits attributes of anthropic Appendix, Fig. S1 provides a chronostratigraphic summary), modification. Moreover, a use-wear analysis was undertaken to there is an additional outstanding biface made on bone (14). A determine whether the piece shows evidence characteristic of use. mammalian long bone fragment collected at locality KGA13 Finally, we evaluated the significance of the bone handaxe in the shows bifacial flake scars with extensive overlap of removals, context of technological advances seen in the Acheulean lithic resulting in a pointed handaxe-like form. The use of bone tools assemblages. by early hominins has long been a subject of debate as to whether they were intentionally used and/or modified or were mimics The Konso Research Area made by a variety of taphonomic agencies (48–51). The flaked The Konso (or Konso-Gardula) research area is located at the large mammal bones from Olduvai Gorge Beds I and II (∼1.9 to southwestern extremity of the Main Ethiopian Rift, south of 1.3 Mya) (52, 53), reported by Mary Leakey in 1971 (3), indeed Lake Chamo, ∼180 km northeast of the fossiliferous Plio- seem to have been intentionally modified (54, 55). In South Pleistocene deposits of the northern Turkana Basin (Fig. 1). Africa, since the report of a single smoothed pointed metapodial The Paleoanthropological Inventory of Ethiopia provided the shaft fragment from Sterkfontein Member 5 West (∼1.7 to 1.4 Mya) first discoveries of ∼1.4 Mya H. erectus fossils and early Acheu- (56), numerous bone shaft fragments and horn cores from lean artifacts at Konso (66). The Konso Formation spans the Swartkrans (∼1.8to1.0Mya)andDrimolen(∼2.0 to 1.8 Mya) time period from ∼1.95 Mya to ∼0.8 Mya (14, 67–69) and con- are now considered to have been used for digging in termite tains rich vertebrate fossils (70, 71), including fossil remains of nests or tuber extraction; these were infrequently shaped by boisei (1.44 to 1.43 Mya at Konso) (72) and H. grinding and not by flaking (57–60). erectus (∼1.45 to 1.25 Mya at Konso, species allocation based on However, bone artifacts were much less frequently produced mandibular and dental morphology) (63). Although a diversity of by early hominins than stone tools, and finely shaped bone tools taxonomic interpretations surrounds Early Pleistocene Homo like bone handaxes are extremely rare (38, 55, 61). To date, only (73, 74), we follow the interpretation of a single variable species one bone handaxe has been reported from the pre-1 Mya African lineage of early Homo (63, 75, 76); we consider it probable that early Acheulean, at Olduvai Gorge Bed II (Table 1). This is a H. erectus-like morphologies emerged between ∼1.9 and 1.7 Mya fragment of a large limb bone (considered elephant) which was and intensified thereafter, with limited chronological overlap bifacially flaked into a handaxe-like form (3, 54, 55). There is with H. habilis sensu lato. some uncertainty regarding the recovery context of this bone At Konso, a total of 21 paleontological collecting localities handaxe; Mary Leakey cites it as coming “from FC” (plate 40 in have been identified, and the chronologic range of the Acheulean ref. 3) or tabulates it with other specimens as “FC and FC West assemblages spans the ∼1.75 to 0.85 Mya time period (14, 15, 71) (middle Bed II)” (p. 247 in ref. 3), while other authors refer it to (SI Appendix,Fig.S1). We previously reported on surface col- FC West (55). Assuming that it was recovered from the FC site, lected and excavated bone assemblages of the ∼1.75 to 1.4 Mya it would derive from the upper levels of Bed II, at ∼1.3 to 1.4 levels at Konso and established a range of human-induced bone Mya (53). On the other hand, the larger FC West assemblage lies marks and fractures (65): cutmarks, percussion marks and frac- stratigraphically above Tuff IIB (3), corresponding to an age of tures, rare digging tools reminiscent of the South African forms, ∼1.6 Mya (20, 53). and flaked bone, as seen in Olduvai (55). A handful of modified Bone handaxes are also known from the large bone flakes is best considered to be shaped by human- sites of the Levant and Europe (Table 1). Although Acheulean induced removals (65), but none are of handaxe-like form. The lithic technology dispersed to the Levant by 1.2 to 1.5 Mya (62, bone handaxe specimen (Fig. 2) was discovered at the KGA13-A1 63) and to Europe by ∼0.7 Mya (9, 62), bone handaxes occur site, located within approximately 5 km of similarly aged sites that

Table 1. Lower Paleolithic sites with bone handaxes Site Country Chronology Lithic No. of BHs Material Reference(s)

KGA13-A1 Ethiopia ∼1.4 Mya Early Acheulean 1 Hippopotamus femur This study Olduvai Bed II FC or FC West Tanzania 1.65 to 1.3 Mya Dev. Oldowan B (early Acheulean) 1 Elephant bone (3, 55) Olduvai Bed IV HEB Tanzania >0.8 Mya Late Acheulean 1 Elephant bone (38) Revadim Israel 500 to 300 Kya Late Acheulean 2 Elephant bone (107) Fontana Ranuccio Italy 458 Kya Late Acheulean 1 Elephant bone (108, 109) Vértesszölös Hungary ∼400 Kya Small tool industry 1* Elephant tibia (110, 111) Bilzingsleben ∼400 Kya Small tool industry 1 Elephant bone (112, 113) Gastel di Guido Italy 327 to 260 Kya Late Acheulean Many Elephant bone (64, 114)

*This piece can alternatively be classified as a pick.

18394 | www.pnas.org/cgi/doi/10.1073/pnas.2006370117 Sano et al. Downloaded by guest on September 25, 2021 A pointed tip. In particular, the cortical side is intensively flaked toward the tip, including several invasive flake scars. Near the tip, the inner side also shows semi-invasive flat flake scars. Four B large flake scars (one possibly a break) occur at the dorsal butt, 1 contributing to a rounded basal shape. A total of 44 flake scars KGA12-A1 KGA13-A1 were counted, 28 on the cortical face and 16 on the inner face. 2 KGA4-A2 (~1.6 Ma) These range in size from ∼30 mm to <10 mm (the majority; n = H. erectus A. boisei mandible skull 28), including a few possible taphonomic removals. Most of the 3 KGA8-A1 flake scars are not isolated but rather are continuous, suggesting 4 5 KGA7-A2 KGA10-A6,A11 KGA6-A1 (~1.75 Ma) deliberate retouch. In addition, bifacial flake scars near the tip KGA7-A1,A3 exhibit an alternate distribution, a pattern hardly attributable to depositional processes. Thus, the Konso bone handaxe is much 6 more extensively flaked than the Olduvai Bed II example, which 7 Konso Formation, main archaeological sites 0 500 km has only eight flake scars (55). between 1.25 Ma and 1.75 Ma As with lithic fractures, it has been experimentally confirmed Fig. 1. Locations of the Konso Acheulean sites. (A) Konso and other early that intentional flaking on bone creates a negative bulb of per- Acheulean sites in East Africa: 1, Gona; 2, Melka Kunture; 3, Konso; 4, cussion (55, 78, 79), and should predominantly produce cone Kokiselei; 5, ; 6, Peninj; 7, Olduvai Gorge. (B) Locations of the fractures (80, 81). However, Backwell and d’Errico (55) found main archaeological sites at Konso. Digital elevation map of A from the that pseudoretouch resulting from accidental breakage of bone National Geophysical Data Center. The aerial photograph composite of B is did not leave a negative bulb of percussion, but that bending based on 1/50,000-scale prints of runs taken in 1984, available at the Map- fractures were common. While 18 out of the 44 flake scars on ping Authority, Addis Ababa. KGA13-A1 ZA1 are cone fractures, only 7 are bending fractures (Table 2). Some of the bending fractures occur as small over- lapping removals on the cortical butt (Fig. 2 and SI Appendix, have yielded substantial Acheulean lithic assemblages and the Figs. S3–S5); however, the large number of invasive or semi- modified bones (SI Appendix, Figs. S1 and S2). invasive flake scars with a negative bulb and their distribution pattern (e.g., continuous alternate removals) are strong indica- Results tors of deliberate shaping. Technological Analysis. The blank of the bifacial bone specimen ANTHROPOLOGY (KGA13-A1 ZA1) appears to have been detached from a hip- Evidence for Use. Use-wear analysis (82–87) of KGA13-A1 ZA1 popotamid femur (Materials and Methods). Much of the dorsal provided a range of evidence consistent with use. The right-side face retains the outer surface of the cortical bone (Fig. 2 and edge (in the outer cortical view) of the bone handaxe shows SI Appendix, Figs. S3 and S4) with matrix partially covering both distinctive edge damage (Fig. 2, area indicated by DE and VE). the cortical surface and flake scars. The inner face shows an Microflake scars or damage occur alternately (Fig. 3 A–E), which elongated fracture surface on the left lateral side presumably is consistent with this edge having been used in longitudinal – created in blank detachment, albeit exhibiting some secondary motions, such as in cutting and/or sawing (88 90). Along this flake scars. On the right side of the base is a concavo-convex edge, the edge and flake scar ridges are extensively rounded on fracture surface running parallel to the left side fracture, also both the cortical and inner faces, especially near the tip probably formed when the bone blank was knocked off. A circa (Fig. 3D). This is attributable to intensive contact with worked 5-mm-diameter pit occurs on the middorsal cortical surface, rep- materials. The bifacially observed rounding is consistent with resenting a probable percussion mark (55, 77). The dimensions of cutting and sawing activities. In contrast, the opposite side edge retains sharper margins and shows minimal edge damage or the bifacially flaked long bone are 127.5 × 74.5 × 45.8 mm. rounding (SI Appendix, Figs. S4 and S6), suggesting that this side The KGA13-A1 ZA1 specimen bears extensive secondary was largely unused. flake scars on both the cortical and inner faces (Fig. 2 and Microwear traces of KGA13-A1 ZA1 provide further clues SI Appendix, Figs. S3 and S4). Both lateral edges show bifacial (Fig. 4). Microscopic analysis revealed that polish and micro- flake scars from the middle to the upper end, producing a rounding are developed on the high spots of the micro- topography. The polished surfaces are frequently associated with striations. The polish, microrounding, and striations were ob- AB CD served on both the cortical and inner faces, suggesting longitu- DE VE dinal motions (91–94). Most of the striations run slightly oblique to the lateral edge, with some oriented more perpendicular, a pattern compatible with mixed actions, including cutting, sawing, and some chopping (95, 96). Thus, a likely task for the Konso bone handaxe would be butchery; similar use-wear patterns have been observed on stone handaxes (91). The polish exhibits a bright appearance, including patchy dull spots. While a series of

E Table 2. Initiation types of flake scars on KGA13-A1 ZA1, the 0 5 cm Konso bifacially flaked long bone Initiation type No.

Cone 18 Fig. 2. KGA13-A1 ZA1, a large mammal long bone shaft fragment shaped Bending 7 ∼ into handaxe form, recovered from the 1.4 Mya KGA13-A1 site. (A) lateral; Indeterminate 19 (B), dorsal (outer); (C), lateral; (D), ventral (inner); (E) lower (basal) views. DE Total 44 and VE indicate the edge shown in Fig. 3.

Sano et al. PNAS | August 4, 2020 | vol. 117 | no. 31 | 18395 Downloaded by guest on September 25, 2021 A D D 1500 μm

A

B

1500 μm

B E 5c 1500 μm 1500 μm

C

C E

5a

5b

3000 μm 3000 μm 1500 μm DE VE

Fig. 3. Detail of the right lateral edge (DE and VE of Fig. 2) of the bone handaxe. (A–E) Alternate edge damage along the ventral and dorsal faces. The edge and flake scar ridges on the ventral and dorsal faces show rounding (D). The alternate edge damage and bifacially formed rounding are consistent with use in longitudinal motions (cutting, sawing). White rectangles 5a to 5c show selected spots of microwear traces seen in Fig. 4.

systematic experimental use-wear studies on stone tools have use-wear analysis suggests that their functional roles may also confirmed a correlation between polish type and worked mate- have been similar. However, bone handaxes are found only rials (91–94, 97), little is known about polish patterns of bone rarely (3, 38, 55, 61), in contrast to the abundant stone handaxes. tools, and thus the materials worked by the bone handaxe remain This may be due in part to taphonomic reasons, but probably uncertain. also to the accessibility of suitable blanks and the difficulty of controlling bone percussion (55, 79). Acheulean stone knappers Discussion used a large cobble or a large flake to produce LCTs (11, 15). As The KGA13-A1 ZA1 bone handaxe is superbly preserved, en- with production, Acheulean bone tool manufacture abling a range of macroscopic and microscopic evaluations. was based on flaking, in contrast to the much later Upper Pa- Morphological comparisons suggest that the raw material was a leolithic bone tool technology based on the groove-and-split shaft fragment of a hippopotamid femur. Both the distribution method with polishing. Thus, a bone handaxe would have re- pattern of flake scars and the high frequency of cone fractures quired a large bone blank, which perhaps was not often available are strong indicators of deliberate flaking. The Konso bone to the makers of the Acheulean LCTs. Backwell and d’Errico handaxe that we report here is made with substantial sophisti- (55) speculated that at Olduvai, bone might have been used as an cation as evidenced by, for example, the large number of small, alternative to stone only when lithic raw materials were not well-controlled cortical side removals in forming the handaxe- available. like shape. The finer bifacial flaking made a relatively straight The rarity of modified bone tools in general, and handaxe edge in a side view, which enables efficient cutting. Use-wear forms in particular, precludes a definitive assessment of the analysis shows that one of the main edges was probably used in significance of the ∼ 1.4 My-old well-modified bone handaxe. cutting and sawing, as has been inferred for stone LCTs. This However, at Konso, this is the time period when significant bone handaxe shows that at Konso, not only in lithic technology, technological developments in lithic technology were occurring. but also in bone modification, H. erectus individuals were suffi- The Konso bone handaxe can be interpreted within this context ciently skilled to make and use a durable cutting edge. as an additional indicator of the high level and varied repertoire Although only few use-wear studies have been undertaken on of hominin skill attained by that time. In generating large flake Acheulean stone handaxes, it is generally believed that handaxes blanks, a variety of prepared core techniques have been reported were used in butchery tasks (91, 95, 96, 98–100). KGA13-A1 from several East African sites between ∼1.5 and 1.0 Mya (15, ZA1 shows that bone handaxes were produced by bifacial flaking 30–32). At Konso, we see a diversity of prepared core techniques in a manner similar to that used for stone tools; furthermore, as early as ∼1.4 to 1.25 Mya, (15). A considerable number of

18396 | www.pnas.org/cgi/doi/10.1073/pnas.2006370117 Sano et al. Downloaded by guest on September 25, 2021 ACB

Fig. 4. Microwear traces. (A–C) Polish and striations. Most of the striations run slightly oblique to the lateral edge, but some are more perpendicular. Microrounding is developed along the ridges (B and C). The polish exhibits a bright appearance with some patchy dull spots (A and B). The polished surfaces are associated with striations and rounding.

Konso cleavers show dorsal flake scars that indicate centripetal thought to have reached the Konso area at or before ∼1.5 Mya (70, core preparation. With these cleavers, trimming was performed

106). Such a biotic environment might have prompted H. erectus ANTHROPOLOGY only on the lateral sides to produce a trapezoidal planform populations to refine Acheulean tool manufacture had they contin- (Fig. 5, upper row). The bit was unretouched and ued to access and process large mammal carcasses. The abundance retained its original sharp edge. In addition to the centripetal core preparation technology, Kombewa flakes, defined as flakes detached from the ventral face of a large flake core (101, 102), are also seen at the same Konso sites (Fig. 5, lower row). Sharon (102) suggested the presence of two ventral faces and two identifiable striking platforms as criteria for the Kombewa method sensu stricto; that is, bifacial core preparation can create dorsally plain flakes that can mimic a Kombewa flake. While most of the large flakes at Konso with two ventral faces exhibit only one , this can be attributed to the removal of the striking platform by secondary flaking. The Kombewa method creates a standardized ovate planform comprising a long edge and a biconvex section and predetermines blank morphol- ogy (102, 103). Whereas the Kombewa method has long been considered a late Early Pleistocene to Middle Pleistocene tech- nology (102), its occurrence at ∼1.4 Mya attests to a much earlier attainment. The ∼1.4 to 1.25 Mya Konso sites also show refined 1 blank shaping (15). The stone handaxes of this time period sometimes exhibit planform symmetry and a thinner tip that required fine flaking (Fig. 6). This was achieved in part by more intensive edge flaking; the ∼1.4 to 1.25 Mya Konso handaxes bear a greater number of flake scars (15). The advanced lithic technology enabled the production of comparatively straight edges, although still retaining considerable sinuosity compared with later handaxes (14, 15). The better-shaped and straighter edges provided functional enhancements for butchering and cutting activities, suggesting an increased demand for animal carcass processing at ∼1.4 to 1.25 Mya at Konso. 2 It has been suggested that humid environments extended north of the central-Saharan watershed at the ∼1.4to1.3Myatimeinterval 0 5 cm (104, 105). This closely corresponds with the Konso paleoenvir- onmental evidence of a transition from a dry grassland-dominated Fig. 5. Cleavers from KGA8-A1 (1.4 to 1.3 Mya) showing blank pre- landscape before ∼1.4 Mya to an episodically expanding lake ac- determination technologies. 1. KGA8-A1c 43: this cleaver exhibits centripetal flake scars that were made to prepare the core surface before detaching the companied by a mosaic of dry grassland, wet grassland, and wood- blank. 2. KGA8-A1c 2: this cleaver has a convex dorsal face, indicating re- land settings thereafter (68, 70, 106). Throughout this time period, moval from the ventral face of a large flake core (Kombewa method). The the Konso large mammalian fauna was dominated (∼70 to 80%) by cleavers were scanned using a 3D handy scanner Artec Spider, and meshes grassland-adapted bovids and suids, many of them immigrant taxa were generated by Artec Studio 12.

Sano et al. PNAS | August 4, 2020 | vol. 117 | no. 31 | 18397 Downloaded by guest on September 25, 2021 Ethiopia. The KGA13-A1 site, which yielded the specimen, is situated close to KGA4-A2 the fault boundary between the Karat Member and the Turoha Member (or underlying Precambrian crystalline rocks) and is stratigraphically placed close to 1.4 Mya (SI Appendix, Fig. S1). The Karat Member section at KGA13-A1 is dominated by massive or parallel-laminated lacustrine clay, including di- atomite and diatomaceous layers, which thickens to the southeast close to the fault boundary. One of the Konso marker tuffs, the Bright White Tuff (BWT), intercalates the middle horizon of the clay beds (SI Appendix,Fig.S2). Two gravelly and pebbly sand beds occur immediately and ∼4 m above the BWT, respectively, and the upper pebbly sands contain bone fragments. The bone handaxe (KGA13-A1 ZA1) was discovered by one of us (B.A.) during a surface survey and is considered to have derived from this layer. This clay-dominant Karat Member section extends westward to KGA12, where it is overlain by the silty/sandy clay sequence containing the PST2 and HGT tuff units (67, 68). We compared the KGA13-A1 ZA1 long bone fragment with the long bones of elephant, rhinoceros, giraffe, and hippopotamus. Based on the combina- tion of the following features, the bone fragment is most probably an an- 1 terior proximal shaft fragment of a hippopotamus left femur. The fragment has a relatively even circular cross-section with a cortical thickness of 22 mm on one end and 18 mm toward the other end (handaxe tip), the latter with a finer trabecular structure internally. The complete shaft diameter would have been ∼80 mm, matching large modern and fossil Plio-Pleistocene hippopot- KGA12-A1 amid femoral shafts in both size and shape. Additional details that further support the attribution are the presence of a nutrient foramen at midanterior position, traversing the cortex steeply, and a rugose ridge on the anterosuperior part of the preserved fragment running obliquely (SI Appendix,Fig.S7). As the mechanics of flake formation on bones in intentional retouch and accidental breakage are not identical (55), their flake scar morphology dif- fers. There are two basic types of flake initiation that reflect flaking modes. Cone initiation occurs when a hard percussion is perpendicularly loaded onto the surface of a brittle material (81). The cone fracture is determined by the concave profile in the area of initiation (80). A bending fracture is formed owing to bending stress away from the point of force application (81) and is characterized by a straight or convex profile at the area of initiation 2 (80). Therefore, intentional flaking basically produces a cone fracture. On the 0 5 cm other hand, as accidental breakage often occurs due to stress away for the point of force, it is frequently initiated with bending. To evaluate whether observed flake scars on the Konso bifacial bone specimen were derived from intentional Fig. 6. Advances in blank shaping technology. While the handaxes from retouch or accidental agencies during depositional processes, the flake initiation KGA4-A2 (∼1.6 Mya) were roughly made (specimen KGA4-A2 2 is shown), types were analyzed based on the methods of the Ho Ho Classification and some of the KGA12-A1 handaxes (∼1.25 Mya) show more intensive and finer Nomenclature Committee (80) and Cotterell and Kamminga (81). flaking, leading to a symmetric planform, a thinner tip, and comparatively The microscopic use-wear analysis was undertaken using a digital micro- straight edges (specimen KGA12-A1a 50 is shown). scope (Keyence VHX-5000) with a dual objective zoom lens (VH-ZST) at magnifications ranging from 20× to 2,000×. As microwear polish on bone artifacts is quite different from that on stone tools, and only limited ex- of raw lithic material locally available at Konso (15) might have perimental studies on microwear on bone artifacts have been conducted enabled such refinement in large blank manufacture and shaping. (but see refs. 82–87), it is difficult to identify materials worked by bone tools. The Konso bone handaxe is only the second bone tool rec- However, the distribution patterns of use-wear can be considered more or ognized as a handaxe from the early Acheuelan, and it is more less equivalent between bone and stone artifacts. Thus, for the purpose of extensively worked than the tool found at Olduvai Bed II. The this study, we focused on inferring potential motions based on experimental large number of fine bifacial removals resulted in the pointed studies conducted on stone tools (82, 88–94). handaxe form with shaped tip and relatively straight edges. Our systematic use-wear analysis furthermore indicates that the Data Availability. All data needed to evaluate the conclusions of this paper are Konso bone handaxe was probably used, possibly for butchering. presented in the main text and SI Appendix. The KGA13-A1 ZA1 specimen is The scarcity of bone handaxes may signify the difficulty in pro- housed in the Laboratory at the Authority of Research curing large bone blanks and the difficulty of flaking bone and Conservation of Cultural Heritage of Ethiopia. compared with stone (55, 79). Despite the scarcity, discovery of ∼ the finely made Konso bone handaxe from the 1.4 Mya time ACKNOWLEDGMENTS. We thank the Authority for Research and Conserva- period shows that refinement of flaking technology in the early tion of Cultural Heritage, Ministry of Culture and Tourism of Ethiopia for Acheulean involved both stone and bone and provides additional permissions and facilitation and the South Nations, Nationalities, and People’s evidence of the technological and behavioral sophistication of Regional State (SNNPRS), the Culture and Tourism Bureau of SNNPRS, and the African H. erectus through Acheulean times. Konso Administrative Zone for supporting the project. We also thank all those who participated in the fieldwork, especially the Konso people, who were essential to the success of the project. We also thank the reviewers for helpful Materials and Methods comments and suggestions. This work was supported primarily by the Japan The KGA13-A1 ZA1 specimen is housed in the Paleoanthropology Laboratory Society for the Promotion of Science (KAKENHI Grants 24000015, to G.S., and at the Authority of Research and Conservation of Cultural Heritage of 18K18532, to K.S.).

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