The Melka Kunture complex consists of a cluster of prehistoric sites that extends over tens of square kilometers in the Upper Awash, on the Ethiopian plateau at ?2000 m above sea level (asl) (Fig. 1A). At this high altitude, the Pleistocene climate would have been cooler and wetter than at the lower elevations of the Rift Valley, from where most fossil evidence for early species of Homo derives. The paleovegetation belonged to the Afromontane complex, ranging from forest to grassland and bushland (1), and the plant species were distinct from those of the African savanna, which developed at lower elevations in drier and warmer environments. The degree of topographic relief of the region meant that the highlands were relatively isolated, leading to the appearance of endemic mammal subspecies (2). In 1981, an infant mandible was discovered in level E of the Garba IV site, although which species of hominin it represents has been a subject of debate (3). In this study, we review the geochronological context of the Garba deposits, characterize the Oldowan and Acheulean lithic assemblages, present the paleoecological context of the site on the basis of analysis of the faunal assemblage and palynology, and reassess the taxonomic affinity of the mandible. Our aim is to determine when, how, and which hominin species was first able to adjust to the high-altitude environment of the highlands of Melka Kunture during the Early Pleistocene and the associated transition from the Oldowan to the Acheulean technocomplex. Broadening our knowledge of the environment at the time and not limiting it to the savanna and to lower altitudes is relevant to understanding how H. erectus was able to expand beyond Africa...

...Level E at Garba IV (now dated to ~2.00 Ma) was first tested in 1981, and 34 m2 were eventually exposed (fig. S4 and figs. S8 to S10), with an additional exposure of 12 m2 of underlying level F (now dated to ~2.02 Ma) (fig. S4 and figs. S8 to S10). Both yielded abundant Oldowan tools (7), and the associated mandible represents one of the only hominin remains directly associated with artefacts in the Early Pleistocene (table S1). It was excavated in level E, a sealed level within a well-established stratigraphic sequence (Fig. 1, C and D; fig. S2; and figs. S9 to S11). The artefacts were mostly produced on obsidian cobbles and pebbles preferentially selected from the rocks available in the local alluvial deposits (Fig. 2A and figs. S12 and S13). Many of these artefacts are made from small flakes, mostly 20 to 50 mm in length, with ~30% retouched and transformed into small, pointed tools (Fig. 2A, 3 to 5, and fig. S13)...

...The vegetation of the Garba IV site belonged to the dry evergreen Afromontane forest and grassland complex, which currently develops on the mountains of East Africa above 1800 m asl (9, 10). The palynology indicates the presence of bushy woodlands alternating with patches of grassland in the area of Melka Kunture at around 1.8 Ma or possibly earlier. (1). A more open vegetation and a mountain grassland followed, which further expanded during the deposition of level D at Garba IV. Afromontane vegetation develops under a mountain climate with large diurnal temperature ranges, resulting in plant species that are distinct from those of the lowland savanna or woodland...

Fig. 1. Location, magnetostratigraphy, and chronostratigraphy of Garba IV.
(A) Location map of the Garba IV site (Melka Kunture, Upper Awash, Ethiopia). (B) The stratigraphy of the Garba gully, with both Garba IV and Garba XIII, a middle Acheulean site (42). Geomagnetic polarity timescale is from (43), 40Ar/39Ar dates are from (5), and K/Ar dates are from (44). (C and D) The stratigraphy of Garba IV and the paleomagnetic sequence of samples with normal (small black squares) and reverse polarity (small white squares) (6) (fig. S3).

Fig. 2. Garba IV artifacts.
(A) Levels E and F (2.00 Ma to 2.06 Ma), Oldowan. Images show obsidian cores (1 and 2) and obsidian pointed tools (3 to 5). (B) Level D (1.95 Ma), Early Acheulean. Images show large retouched flakes shaped on basalt or obsidian (6 to 8) and handaxes shaped on lava, basalt, or obsidian flakes (9 to 12).