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The manufacture of flaked stone artifacts represents a major milestone in the technology of the human lineage. Although the earliest production of primitive stone tools, predating the genus Homo and emphasizing percussive activities, has been reported at 3.3 million years ago (Ma) from Lomekwi, Kenya, the systematic production of sharp-edged stone tools is unknown before the 2.58-2.55 Ma Oldowan assemblages from Gona, Ethiopia. The organized production of Oldowan stone artifacts is part of a suite of characteristics that is often associated with the adaptive grade shift linked to the genus Homo. Recent discoveries from Ledi-Geraru (LG), Ethiopia, place the first occurrence of Homo ~250 thousand years earlier than the Oldowan at Gona. Here, we describe a substantial assemblage of systematically flaked stone tools excavated in situ from a stratigraphically constrained context [Bokol Dora 1, (BD 1) hereafter] at LG bracketed between 2.61 and 2.58 Ma. Although perhaps more primitive in some respects, quantitative analysis suggests the BD 1 assemblage fits more closely with the variability previously described for the Oldowan than with the earlier Lomekwian or with stone tools produced by modern nonhuman primates. These differences suggest that hominin technology is distinctly different from generalized tool use that may be a shared feature of much of the primate lineage. The BD 1 assemblage, near the origin of our genus, provides a link between behavioral adaptations-in the form of flaked stone artifacts-and the biological evolution of our ancestors. [ABSTRACT FROM AUTHOR]

The Turkana Basin in Kenya has an extensive record of Holocene activities relating to mobility and economy of foraging and herding communities. Obsidian is only known from a few key localities in northern Kenya. As such, the use of obsidian as a toolstone material, commonly used during the mid-Holocene, provides one way to trace exchange, interaction and population movements during the transition to pastoralism. We employ X-ray fluorescence to characterize obsidian artefacts from four Pastoral Neolithic assemblages. Data reveal a highly mobile and diversified population that used watercraft to access and transport obsidian resources. Specifically, the use of the North Island obsidian source in Lake Turkana indicates that boat use was significant during this transitional period. The incorporation of watercraft transport and aquatic resources in our analyses of Pastoral Neolithic sites affords a greater understanding of subsistence, mobility and economy in this important period in East African prehistory. [ABSTRACT FROM AUTHOR]

Abstract: Understanding the influence of orbital climate cycles on hominin evolution remains a key challenge in paleoanthropology. The two major unresolved issues are: the absence of a climate proxy yielding high-resolution (<20kyr) terrestrial climate records, and the lack of age control on hominin fossil occurrences at sufficiently high resolution. Here we present a novel climate proxy, strontium isotope ratios (87Sr/86Sr) of lacustrine fish fossils from the Turkana Basin, that solves these issues by recording orbitally forced variation in summer monsoon intensity over the Ethiopian Highlands. We successfully applied the climate proxy to a ~150kyr time interval of ~2million year old paleolake deposits containing hominin fossils. Existing age control of the studied interval was improved by a new magnetostratigraphic record precisely locating the base of the Olduvai chron (C2n) near the bottom of the sequence. Spectral analysis demonstrates that 87Sr/86Sr variability is primarily determined by precession, which enables us to place hominin fossils in an astronomically-tuned climate framework. The Sr climate proxy is potentially applicable to all hominin-bearing lake deposits in the Turkana Basin, ranging in age from ~4.2 to 0.8million years ago (Ma). Our results demonstrate that between ~2 and 1.85Ma the Turkana Basin remained well-watered and inhabited by hominins even during periods of precession maxima when summer monsoon intensity was lowest. This is in contrast to other basins in the East African Rift System (EARS) that were impacted heavily by precession-forced droughts. We hypothesize that during lake phases, the Turkana Basin was an aridity refugium for permanent-water dependent fauna – including hominins – over the precessional climate cycles. [Copyright &y& Elsevier]

Research on the origins of Homo sapiens and the development of our species' unique behavior is focused on the Middle Stone Age (MSA) period in Africa (in comparison with the European Upper Palaeolithic). Although archaeological and paleontological fieldwork in the Turkana Basin in northwestern Kenya has contributed greatly to our understanding of human evolution in Africa, the Basin's MSA archaeological record remains poorly known. We report on a reconnaissance of MSA sites in West Turkana, Kenya, which included known archaeological/paleoanthropological localities at Eliye Springs and Kabua Waterhole (Kadokorinyang). A newly-discovered site, Nakechichok 1 (GdJh 5), preserves MSA tools stratified beneath Late Stone Age assemblages. The MSA lithic artifacts from Nakechichok 1 differ from those known from other MSA localities in nearby regions, and, they expand the known scope of MSA variability in the Turkana Basin, demonstrating that the MSA is not "missing" in this region, but just hard to find. [ABSTRACT FROM AUTHOR]

Abstract: In addition to the new fragments of the Omo I skeleton, renewed fieldwork in the Kibish Formation along the lower reaches of the Omo River in southwestern Ethiopia has yielded new hominin finds from the Kibish Formation. The new finds include four heavily mineralized specimens: a partial left tibia and a fragment of a distal fibular diaphysis from Awoke''s Hominid Site (AHS), a parietal fragment, and a portion of a juvenile occipital bone. The AHS tibia and fibula derive from Member I and are contemporaneous with Omo I and II. The other specimens derive from Chad''s Hominid Site (CHS), and derive from either Member III or IV, which constrains their age between ∼8.6 and ∼104ka. [Copyright &y& Elsevier]

Abstract: Cranial and skeletal remains of modern humans, Homo sapiens, were discovered in the Kibish Formation in 1967 by a team from the Kenya National Museums directed by Richard Leakey. Omo I, from Kamoya''s Hominid Site (KHS), consists of much of a skeleton, including most of the cranial vault, parts of the face and mandible, and many postcranial elements. Omo II, from Paul''s Hominid Site (PHS), is a virtually complete calvaria. Only a limited fauna and a few stone artifacts attributed to the Middle Stone Age were recovered in conjunction with the fossil hominids. The available dating techniques suggested a very early age, over 100 ka, for Member I, from which the Omo I and Omo II fossils were recovered. However, in subsequent decades, the reliability of the dates and the provenance of the Kibish hominids were repeatedly questioned. The papers in this volume provide a detailed stratigraphic analysis of the Kibish Formation and a series of new radiometric dates that indicate an age of 196 ± 2 ka for Member I and 104 ± 1 for Member III, confirming the antiquity of the lower parts of the Kibish Formation and, in turn, the fossils from Member I. Studies of the postcranial remains of Omo I indicate an overall modern human morphology with a number of primitive features. Studies of an extensive lithic record from Members I and III indicate a Middle Stone Age technology comparable to assemblages of similar age elsewhere in Ethiopia. Studies of the mammalian, avian, and fish faunas indicate overall similarities to those found in the region today, with a few distinctive differences. [Copyright &y& Elsevier]

Abstract: The Kibish Formation in southwestern Ethiopia, with an aggregate thickness of ~105m, consists of lacustrine, marginal lacustrine, and deltaic deposits. It is divided into four members numbered I to IV on the basis of erosion surfaces (disconformities) between the strata of each member. It overlies the Mursi and Nkalabong formations, the latter of which is here shown to correlate with the Shungura Formation. Tephra layers in each member allow for secure correlation between geographically separated sections on the basis of the composition of their volcanic glass. Members I, III, and IV of the Kibish Formation appear to have been deposited at the same times as sapropels S7 (197ka), S4 (104ka), and S1 (8ka) in the eastern Mediterranean Sea, respectively. We correlate the KHS Tuff of the Kibish Formation with a >154-kyr-old unnamed tuff in the Konso Formation. Tephra in Member IV may derive from Mount Wenchi, a volcano situated on the divide between the Omo and Blue Nile drainage basins. Thin-bedded sedimentary layers probably represent annual deposition reflecting rapid sedimentation (~30m/kyr) of parts of the formation. This conclusion is supported by variation in paleomagnetic inclination through a sequence of these layers at KHS. Two fossils of early Homo sapiens (Omo I and Omo II) derive from Member I. Their stratigraphic placement is confirmed by analysis of the KHS Tuff in the lower part of Member II at both fossil sites. The KHS Tuff lies above a disconformity, which itself lies above the fossils at both sites. 40Ar/39Ar dates provide an estimated age of ~195kyr for these fossils. Omo III, a third fossil H. sapiens, probably also derives from Member I of the Kibish Formation and is of similar age. Hominin fossils from AHS, a new site, also derive from Member I. Hominin fossils from CHS can only be placed between 104ka and 10ka, the H. sapiens specimen from JHS is most likely 9–13kyr in age, and a partial skeleton of H. sapiens from Pelvic Corner is most likely ~6.6kyr in age. [Copyright &y& Elsevier]

Abstract: Detailed stratigraphic analysis of the Omo I and Omo II fossil localities confirms both the relational and sequential context reported by Butzer in 1969. The two fossils derive from approximately the same level within upper Member I of the Kibish Formation. Additional features of the local stratigraphic sequences indicate a complex history of depositional events, minor erosional surfaces, and weak soil formation throughout upper Member I. [Copyright &y& Elsevier]

Recent studies suggest that differential human male investment in mating (male-male competition and mate-seeking behavior) and parenting effort may be associated with variation in testosterone levels. The Ariaal present an interesting test case because marital relations tend to be aloof and direct paternal care minimal by cross-cultural standards. Polygyny is prevalent and increases with age, and the age-set system highly structures the transition to marriage. A test of the effect of marital status on testosterone levels among the Ariaal involved 205 men aged 20 and older from a settled agropastoral community and nomadic populations. Each participant provided morning and afternoon saliva samples in which testosterone levels were measured, provided demographic background during interviews, and had anthropometrics taken. As predicted, during the dynamic ages (20-39) of transition from life as a bachelor and warrior to monogamous marriage, men with one wife had significantly lower testosterone levels than unmarried men. Contrary to prediction, however, polygynously married men did not have higher testosterone levels than their monogamously married counterparts. While variation in testosterone may be associated with mating effort in young Ariaal men, political networks and wealth may be better predictors of marital status in older men. [ABSTRACT FROM AUTHOR]

Over the last thirty years, investigations in the Nachukui Formation (West Turkana, Kenya) have revealed the importance of the region for human evolution studies within an archaeological sequence spanning the period 3.3 million years (Ma) to 0.7 Ma. Despite the numerous sites discovered, little is known about pounding activities during this time period in the region. In this paper, we present an analysis of percussive tools from three West Turkana archaeological sites: Lokalalei 2C, Kokiselei 1 and Kokiselei 4, dated between 2.3 Ma and 1.76 Ma. Their chronological range allows us to conduct a diachronic comparison of the percussive activities during a time span with two hominin genera (Australopithecus boisei, early Homo and Homo erectus). The three assemblages are compared with others from the Early Stone Age and with experimental percussive tools. Despite the stable predominance of hammerstones associated with stone knapping activities over time in the Nachukui Formation, our macro- and microscopic analyses reveal an inter-site variability in the type and re-use of percussive tools for specific heavy-duty pounding activities. When compared with other Early Stone Age sites, Lokalalei 2C, Kokiselei 1 and Kokiselei 4 similarly present a low frequency of pounding tools but a high number of blanks used for both flaking and pounding activities, suggesting that the reutilization of the tools and the change in their functionality was common in the ESA lithic record. • We analyse synchronic and diachronic variability of pounding tools from West Turkana sites dated to 2.3–1.76 Ma. • Oldowan (Localalei 2C, Kokiselei 1) and Acheulean (Kokiselei 4) percussive tools are compared. • Hammerstones used for flaking dominate in the studied assemblages. • Cores re-utilized as hammerstones make up a significant component of the pounding tools identified. [ABSTRACT FROM AUTHOR]

The article discusses the findings of paleoanthropology research by Brian Richmond of George Washington University (GWU) in Washington, D.C. and colleagues, presented at a Paleoanthropology Society meeting held in Honolulu, Hawaii from April 2-3, 2013. Topics include the team's discovery of 1.5-million-year-old hominin footprints in Ileret, Kenya, the size and direction of the prints, which indicated they belonged to a group of males, and social behavior in early humans.

Summary: Two new fossil jawbones from Kenya are claimed to confirm a diversity of early Homo species. However, archaic species concepts and an inadequate fossil record continue to obscure the origins of our genus. [ABSTRACT FROM AUTHOR]