Sileshi Semaw

National Research Center on Human Evolution | CENIEH · Prehistory

The Gona paleoanthropological field project in the Afar region of Ethiopia has long been associated with the earliest Oldowan stone tools. However, over the last 20 years, ongoing research at Gona has expanded its contributions considerably, producing fossils of Ardipithecus kadabba, Ardipithecus ramidus, and Homo erectus, as well as additional arc...

The Busidima Formation in the Afar region, Ethiopia, spans the Quaternary and records the cultural evolution of the genus Homo. Yet, the Middle Pleistocene to Holocene fluvial environments in which early humans lived are undersampled in eastern Africa. This paper examines the stratigraphy, geochronology and paleoenvironments of the newly designated...

Geochemical analysis of volcanic glass shards from the Gona Project, Afar, Ethiopia. Data were obtained from University of Utah (UU, 2009) and the New Mexico Bureau of Geology and Mineral Resources (NMBGMR, 2015-2018). These data were used to correlate tephra deposits within the Odele Member of the Busidima Formation (Stinchcomb et al. accepted)

EPMA method metadata of volcanic glass shards from the Gona Project, Afar, Ethiopia. EMPA methods are from New Mexico Bureau of Geology and Mineral Resources (NMBGMR, 2015-2018).

EPMA method metadata of volcanic glass shards from the Gona Project, Afar, Ethiopia. EMPA methods are from University of Utah (UU, 2009).

The Busidima Formation in the Afar region, Ethiopia, spans the Quaternary and records the cultural evolution of the genus Homo . Yet, the Middle Pleistocene to Holocene fluvial environments in which early humans lived are undersampled in eastern Africa. This paper examines the stratigraphy, geochronology and paleoenvironments of the newly designate...

Humans evolved in the dynamic landscapes of Africa under conditions of pronounced climatic, geological and environmental change during the past 7 million years. This book brings together detailed records of the paleontological and archaeological sites in Africa that provide the basic evidence for understanding the environments in which we evolved....

Two Early Pleistocene fossils from Gona, Ethiopia, were originally assigned to Homo erectus, and their differences in size and robusticity were attributed to either sexual dimorphism or anagenetic evolution. In the current study, we both revisit the taxonomic affinities of these fossils and assess whether morphological differences between them refl...

Significance Humans have the proportionately smallest male canines among all anthropoids and little canine sexual dimorphism. However, the evolutionary emergence of this defining condition remains unclear because until now we have lacked a reliable method of determining dimorphism in weakly dimorphic fossil species. Using a probability-based method...

Significance The evolutionary study of sexual dimorphism has been hampered by the general inability to accurately estimate low levels of dimorphism in fossil assemblages with no information on sex membership. In previous estimates, accuracy decreased with lower dimorphism levels because the hidden distributions of the two sexes embedded in the samp...

The Early Pleistocene faunal record in North Africa is well known from classic localities, documented already in the 19th century and earlier part of the 20th century, such as Aïn Boucherit and Aïn Hanech. In the second half of the 20th century, radiometric dates became available and correlations were used to estimate the ages of the earliest Pleis...

Les sites pléistocènes inférieurs d’Afrique de l’Est et ceux de Gona (Éthiopie) datés de 2,6 millions d’années en particulier, ont livré les plus anciens outils oldowayens et ossements portant des traces de découpe induites par l’utilisation de ces outils taillés par les hominidés indubitablement reconnus à ce jour. Par comparaison, les artefacts l...

Understanding the Critical Zones (CZs) Anatomically Modern Humans interacted with as they dispersed out of Africa is vital towards gaining insight into what drove these migrations. Records of these Middle to Late Pleistocene CZs are abundant and well-preserved at Gona, Ethiopia in the form of fossil soils, or paleosols; well-constrained by a detail...

The Busidima Formation in the Afar region, Ethiopia, spans the Quaternary and records the cultural evolution of the genus Homo. This paper examines the stratigraphy, geochronology and paleoenvironments of the newly designated Odele Member of the uppermost Busidima Formation (<160 ka), which has received little attention despite being a critical tim...

Although stone tools generally co-occur with early members of the genus Homo , they are rarely found in direct association with hominins. We report that both Acheulian and Oldowan artifacts and Homo erectus crania were found in close association at 1.26 million years (Ma) ago at Busidima North (BSN12), and ca. 1.6 to 1.5 Ma ago at Dana Aoule North...

Environmental change is often inferred to have driven dispersals of Anatomically Modern Humans (AMH) out of Africa, yet the precise landscape context of these migrations remains unclear. Furthermore, fluvial-based archives of paleoenvironment during periods of dispersal are scarce. Gona, an area in northeastern Ethiopia with one of the most continu...

The capacity of Homo sapiens for the intergenerational accumulation of complex technologies, practices, and beliefs is central to contemporary accounts of human distinctiveness. However, the actual antiquity and evolutionary origins of cumulative culture are not known. Here we propose and exemplify a research program for studying the origins of cum...

Functional analyses of the 4.4 Ma hominin Ardipithecus ramidus postcrania revealed a previously unknown and unpredicted locomotor pattern combining arboreal clambering and a form of terrestrial bipedality. To date, all of the fossil evidence of Ar. ramidus locomotion has been collected from the Aramis area of the Middle Awash Research Project in Et...

The foot of Ardipithecus ramidus.

Early humans in northern Africa Evidence for the earliest stone tools produced by human ancestors (from ∼2.6 million years ago) has hitherto come from East Africa. Sahnouni et al. report the discovery of Oldowan stone artifacts and associated cutmarks on fossil bones excavated in Algeria, with the earliest dated to 2.4 million years ago. Thus, homi...

Gona in the Afar region of Ethiopia has yielded the earliest Oldowan stone tools in the world. Artefacts from the East Gona (EG) 10 site date back 2.6 million years. Analysis of the lithic assemblage from EG 10 reveals the earliest-known evidence for refitting and conjoining stone artefacts. This new information supplements data from other Oldowan...

The origin of Homo sapiens and their subsequent dispersal out of Africa during the Mid-to-Late Pleistocene are hallmark events in the evolution of humans and are recorded as snapshots within terrestrial sedimentary deposits in East Africa. This study uses paleosols to reconstruct paleoenvironments of those events at Gona, Ethiopia - an area with on...

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 se...

Since 2000, significant collections of Latest Miocene hominin fossils have been recovered from Chad, Kenya, and Ethiopia. These fossils have provided a better understanding of earliest hominin biology and context. Here, we describe five hominin teeth from two periods (ca. 5.4 Million-years-ago and ca. 6.3 Ma) that were recovered from the Adu-Asa Fo...

Inter-site technological variation in the archaeological record is one of the richest potential sources of information about Plio-Pleistocene hominid behavior and evolution. However, appropriate methods for describing and comparing Oldowan assemblages have yet to be agreed upon, and interpretation of the early record remains highly controversial. P...

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...

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 Ache...

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 com...

The Gona area includes many rich fossil localities that are of great consequence to the study of human evolution. The Adu-Asa Formation, containing the oldest of these fossils, consists of nearly 200 m of fossil-bearing sedimentary rocks in thin (≤30 m), laterally variable sections interlayered with abundant basaltic lava flows. These volcanic and...

Deposits in the Gona Paleoanthropological Research Project (GPRP) area in eastcentral Ethiopia span most of the last ∼6.4 m.y. and are among the longest and most complete paleoenvironmental and human fossil archives in East Africa. The 40Ar/39Ar and paleomagnetic dates and tephrostratigraphic correlations establish the time spans for the four forma...

The Gona Paleoanthropological Research Project (GPRP) area includes many rich fossil localities that are of great consequence to the study of human evolution. Genetic estimates of the divergence between human and chimpanzee lineages indicate that this split happened between 5 and 7 Mya. The sedimentary deposits at Gona range in age from .15 Ma to 4...

Published evidence of Oldowan stone exploitation generally supports the conclusion that patterns of raw material use were determined by local availability. This is contradicted by the results of systematic studies of raw material availability and use among the earliest known archaeological sites from Gona, Afar, Ethiopia. Artifact assemblages from...

Newly recorded archaeological sites at Gona (Afar, Ethiopia) preserve both stone tools and faunal remains. These sites have also yielded the largest sample of cutmarked bones known from the time interval 2.58-2.1 million years ago (Ma). Most of the cutmarks on the Gona fauna possess obvious macroscopic (e.g., deep V-shaped cross-sections) and micro...

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 disco...

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 cont...

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 woodla...

The systematic archaeological and geological survey and excavations at Gona between 1992–1994 led to the discovery of well-flaked stone artefacts which are currently the oldest known from anywhere in the world. More than 3000 surface and excavated artefacts were recovered at 15 localities documented east and west of the Kada Gona river. Based on ra...

The Oldowan Stone tool industry was named for 1.8-million-year-old (Myr) artefacts found near the bottom of Olduvai Gorge, Tanzania. Subsequent archaeological research in the Omo (Ethiopia) and Turkana (Kenya) also yielded stone tools dated to 2.3 Myr. Palaeoanthropological investigations in the Hadar region of the Awash Valley of Ethiopia, reveale...

The Paleoanthropological Inventory of Ethiopia is a long-term project designed to assess the paleoanthropological resources of the Ethiopian rift system. Inventory work completed in 1989 has established several new research areas. One of these, the Kesem-Kebena area near the northern terminus of the Main Ethiopian Rift, has now been investigated by...

In 1989 the Paleoanthropological Inventory of the Ethiopian Ministry of Culture targeted for reconnaissance the last paleoanthropologically unknown quadrant of the Turkana Basin, the Fejej area. Fieldwork here identified fossiliferous Oligocene, Pliocene, and Pleistocene deposits. Late Pliocene Oldowan archaeological occurrences were discovered bel...