Sileshi Semaw

2.6-Million-year-old stone tools and associated bones from OGS-6 and OGS-7, Gona, Afar, Ethiopia

CRAFT Research Center, 419 N. Indiana Avenue, Indiana University, Bloomington, IN, 47405, USA Department of Anthropology, Southern Connecticut State University, 501 Crescent Street, New Haven, CT 06515-1355, USA Department of Geosciences, University of Arizona, Tucson, AZ, 85721, USA Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA Department of Earth and Planetary Science, University of California, Berkeley, CA 94709, USA Departmento de Prehistoria y Arquelogia, Facultad de Geografia, e Historia, Universidad Complutense de Madrid, Ciudad Universitaria 28040, Madrid, Spain Department of Anthropology and CRAFT Research Center, 419 N. Indiana Avenue, Indiana University, Bloomington, IN, 47405, USA Sterkfontein Research Unit, University of Witwatersrand, WITS 2050, Johannesburg, South Africa Department of Anatomy, Case Western Reserve University-School of Medicine, 10900 Euclid Avenue, Cleveland, OH, 44106-4930, USA Laboratory of Physical Anthropology, Cleveland Museum of Natural History, Cleveland, OH 44106, USA

A Female Homo erectus Pelvis from Gona, Ethiopia

Analyses of the KNM-WT 15000 Homo erectus juvenile male partial skeleton from Kenya concluded that this species had a tall thin body shape due to specialized locomotor and climatic adaptations. Moreover, it was concluded that H. erectus pelves were obstetrically restricted to birthing a small-brained altricial neonate. Here we describe a nearly complete early Pleistocene adult female H. erectus pelvis from the Busidima Formation of Gona, Afar, Ethiopia. This obstetrically capacious pelvis demonstrates that pelvic shape in H. erectus was evolving in response to increasing fetal brain size. This pelvis indicates that neither adaptations to tropical environments nor endurance running were primary selective factors in determining pelvis morphology in H. erectus during the early Pleistocene.

Isotopic evidence for Plio-Pleistocene environmental change at Gona, Ethiopia

Abstract A 4.5 Ma record of fluvial and lacustrine deposits is well exposed at Gona, in the Afar Depression of Ethiopia. We use isotopic values of pedogenic carbonate and fossil teeth to reconstruct Plio–Pleistocene environmental change at Gona. An increase in δ13C values of pedogenic carbonates since 4.5 Ma points to a shift from woodlands to grassy woodlands in the early Pliocene, −10.4 to −3.9‰ (VPDB), to more open but still mixed environments in the late Pleistocene, −3.0 to −1.4‰ (VPDB). This pattern is also seen in isotopic records elsewhere in East Africa. However, at 1.5 Ma the higher proportion of C4 grasses at Gona is largely a result of a local facies shift to more water-limited environments. The wide range of δ13C values of pedogenic carbonate within single stratigraphic levels indicates a mosaic of vegetation for all time intervals at Gona that depends on depositional environment. Elements of this mosaic are reflected in δ13C values of both modern plants and soil organic matter and Plio–Pleistocene soil carbonate, indicating higher amounts of C4 grasses with greater distance from a river channel in both the modern and ancient Awash River systems. δ18O values of pedogenic carbonates increase up-section from −11.9‰ in the early Pliocene to −6.4‰ (VPDB) in the late Pleistocene. The wide range of δ18O values in paleovertisol carbonates from all stratigraphic levels probably reflects short-term climate changes and periods of strong evaporation throughout the record. Based on the comparison between δ18O values of Plio–Pleistocene pedogenic carbonates and modern waters, we estimate that there has been a 6.5‰ increase in mean annual δ18O values of meteoric water since 4.5 Ma. δ18O values of pedogenic carbonate from other East African records indicate a similar shift. Increasing aridity and fluctuations in the timing and source of rainfall are likely responsible for the changes in δ18O values of East African pedogenic carbonates through the Plio–Pleistocene.

Early Pliocene hominids from Gona, Ethiopia

Comparative biomolecular studies suggest that the last common ancestor of humans and chimpanzees, our closest living relatives, lived during the Late Miocene–Early Pliocene. Fossil evidence of Late Miocene–Early Pliocene hominid evolution is rare and limited to a few sites in Ethiopia, Kenya and Chad. Here we report new Early Pliocene hominid discoveries and their palaeoenvironmental context from the fossiliferous deposits of As Duma, Gona Western Margin (GWM), Afar, Ethiopia. The hominid dental anatomy (occlusal enamel thickness, absolute and relative size of the first and second lower molar crowns, and premolar crown and radicular anatomy) indicates attribution to Ardipithecus ramidus. The combined radioisotopic and palaeomagnetic data suggest an age of between 4.51 and 4.32 million years for the hominid finds at As Duma. Diverse sources of data (sedimentology, faunal composition, ecomorphological variables and stable carbon isotopic evidence from the palaeosols and fossil tooth enamel) indicate that the Early Pliocene As Duma sediments sample a moderate rainfall woodland and woodland/grassland.

Paleoenvironments of the earliest stone toolmakers, Gona, Ethiopia

Fluvio-lacustrine sediments of the Hadar and Busidima Formations along the northern Awash River (Ethiopia) archive almost three million years (3.4 to <0.6 Ma) of human evolution, including the earliest documented record of stone toolmaking at 2.5–2.6 Ma. This paper brings together sedimentologic and isotopic evidence for the paleoenvironmental context of early hominids from both formations, but with particular emphasis on the setting for the early toolmakers. The pre–2.92 Ma record (Hadar Formation) is characterized by low-gradient fl uvial, paludal, and lacustrine deposition in an undissected topography most analogous to reaches of the modern middle Awash River near Gewane. The Gona area experienced repeated deep dissection and aggradation by the Awash River, starting between 2.92 and ca. 2.7 Ma and continuing through the top of the record at <0.6 Ma (Busidima Formation). Each aggradational succession is 10–20 m in thickness and fi nes upward from wellrounded conglomerates at the base to capping paleosols at the top. During this period the ancestral Awash represented by these fi ning upward sequences was dominantly meandering and fl owed northeast, as it does today. Smaller channels tributary to the axial Awash system are also extensively exposed in the Busidima Formation. Compared to the axial-system conglomerates, the tributary channels transported fi ner, less mature volcanic clasts mixed with abundant carbonate nodules reworked from adjacent badlands. Stone artifacts (Oldowan; 2.6–2.0 Ma) at the oldest archaeological sites are only associated with the axial Awash system, in the bedded silts or capping paleosols of the fi ning upward sequences. The implements were made from rounded cobbles from the channels, but manufacture and use of the tools was always away from the channel bars, on the nearby sandy banks and silt-dominated fl oodplains. Archaeological sites higher in the record (Acheulian; <1.7 Ma) occur in similar axial river contexts, as well as along tributary channels further removed from artifact raw material sources. Mature paleosols in the Hadar and Busidima Formations are mostly pale to darkbrown Vertisols typifi ed by abundant clay slickensides, pseudo-anticlinal and vertical fracturing, and carbonate nodules. Such calcic Vertisols are common in the region today, demonstrating that the paleoclimate over the past 3.4 m.y. has been semi-arid and strongly seasonal. Carbon isotopic results from pedogenic carbonates in the Vertisols allow reconstruction of the proportion of C 3 plants (trees and shrubs) to C 4 plants (grasses) through time. The δ 13

The Oldowan-Acheulian Transition: Is there a “Developed Oldowan” Artifact Tradition?

The phrase “Developed Oldowan” (DO) was originally coined by M. Leakey to describe a technologically “advanced Oldowan” artifact tradition, that preceded the Acheulian Industry. M. Leakey further identified three stages of the DO which she labeled as the DOA, DOB and DOC. The DO (sensu lato) has been generally recognized as transitional to the Acheulian, but the status of the DOB and the DOC remains unclear. In addition to a lack of clarity in terms of classification, the DO also suffers from a lack of secure radiometric dates, even at Olduvai where it was first identified. Despite such shortcomings, archaeologists still assign assemblages into the DO, as supposedly “intermediate” or transitional between the Oldowan and the Acheulian. However, a closer look at the DO assemblages from Olduvai Gorge and other sites in Africa and the Middle East shows that the artifacts assigned into this tradition are not technologically drastically different from the preceding Oldowan. Probably the flaking characteristics of the raw material types (e.g., quartzite and limestone, and to a lesser extent basalt) and the original shape of the cobbles used by hominins may have played a major role in the final shape of the “distinctive” artifact types (such as spheroids/subspheroids) used for assigning assemblages into the DO. Further, both the DOB and the Acheulian appeared ˜1.7 million years ago (Ma) in the archaeological record, making it unlikely that the DO is a transitional artifact tradition that preceded the Acheulian. Our preliminary evaluation of the archaeological record at Gona, Ethiopia and elsewhere suggests a fairly abrupt appearance of the Acheulian after a temporally rapid transition from the Oldowan.

The female Homo pelvis from Gona: Response to Ruff (2010)

Department of Anatomy, Case Western Reserve University School of Medicine, 10900 Euclid Avenue, Cleveland, OH 44106-4930, USA b Institute for the Science of Origins, Case Western Reserve University, Cleveland, OH 44106, USA c Laboratory of Physical Anthropology, Cleveland Museum of Natural History, Cleveland, OH 44106, USA Department of Geosciences, University of Arizona, Tucson, AZ, USA Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD, USA Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), Sierra de Atapuerca s/n, 09002 Burgos, Spain g The Stone Age Institute, 1392 West Dittemore Road, Gosport, IN 47433, USA CRAFT, Indiana University, Bloomington, IN 47405, USA

From Nothing to Something: The Appearance and Context of the Earliest Archaeological Record

Before 2.6 million years ago (Ma), no archaeological record has been securely documented, and therefore there is no evidence of hominin tool use. Then, at 2.6–2.58 Ma, there is widespread evidence for tool manufacture and use at several archaeological sites, with undisputed stone tools and fossil fauna at Gona, Ethiopia. Additionally, the evidence from the earliest archaeological sites at Gona shows that the earliest stone tool makers were skilled flintknappers and were able to select high quality stone raw materials. The possible reasons behind this seeming abrupt transition from the absence of stone tools to the presence thereof include sampling biases, paleogeographic influences, gaps in the geological record, paleoenvironmental change, and changes in the record of hominin evolution.

Eurygnathohippus woldegabrieli, sp. nov. (Perissodactyla, Mammalia), from the Middle Pliocene of Aramis, Ethiopia

ABSTRACT Eurygnathohippus is a genus of hipparionine horse that evolved in and was confined to the African continent from the late Miocene to Pleistocene interval. Eurygnathohippus woldegabrieli is a new species from Aramis, Ethiopia, dated between 4.4 and 4.2 Ma. The hypodigm is currently restricted to 157 specimens from 14 Aramis localities and one nearby Gona locality. We nominate a mandible as the type and a maxillary dentition and two complete metacarpal IIIs as paratypes. Our analysis reveals that Eurygnathohippus woldegabrieli is derived compared with late Miocene Eurygnathohippus feibeli in its overall size, cheek tooth crown height, mandibular symphysis length, and robusticity of distal limb elements. It is primitive in mandibular symphysis length and robusticity of distal limb elements compared with the more advanced medial Pliocene species Eurygnathohippus hasumense. A study of Eurygnathohippus woldegabrielis paleodiet as measured by two mesowear methods, corroborated by carbon isotope studies, reveals that it was a dedicated grazer with a coarse C4 diet akin to that of modern zebras, wildebeests, and white rhinoceroses. SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP

The Early Acheulean ~1.6–1.2 Ma from Gona, Ethiopia: Issues related to the Emergence of the Acheulean in Africa

Konso in Ethiopia and Kokiselei in Kenya, both dated to ~1.7 million years ago (Ma), and FLK West, a recently reported site from Olduvai dated to 1.7 Ma, are the earliest Acheulean sites known in East Africa. Ongoing archaeological investigations at Gona, in the Afar Depression of Ethiopia, have also produced early Acheulean stone assemblages at several sites, estimated to ~1.6–1.2 Ma. A number of sites, including BSN-12 and OGS-12, have yielded archaeological materials comparable to the earliest Konso artifacts. The stone assemblages from the Gona sites consist of crudely made handaxes, cleavers, and picks, as well as Mode I (Oldowan) cores, and debitage. A variety of raw materials were exploited at Gona, with trachyte, rhyolite, and basalt being the most common.