Late Pliocene grassland from Olduvai Gorge,Tanzania

The Olduvai fossil plants documented by us in this paper are the first direct evidence for open grassland in the late Neogene of Africa based on macroplant remains. Silicified remains of herbaceous ground cover are exceptionally well preserved in situ within Late Pliocene sediments below the initial pyroclastic ash surge unit of Tuff IF in the uppermost part of Bed I, Olduvai Gorge, northern Tanzania. Published radiometric and palaeomagnetic dates place this grass layer between 1.839 + 0.005 Ma and 1.785 + 0.01 Ma. Exposed at localities on the south side of the Gorge this herbaceous ground cover grew on a floodplain developed on a dried out lake bed, following pronounced lake retreat of saline–alkaline palaeo-Lake Olduvai during a developing dry climatic phase. Sheathed basal culms, rhizomes and roots are interpreted as those of one or more small mat-forming grasses or less likely, sedges. Small dicotyledonous herbs were probably also present. The proximity of adjacent plants indicates a relatively dense ground cover. Roots extended at least 8 cm below the ground surface. Aerial parts of the plants were absent or were not preserved when the weathered basal culms were covered by a thin layer of brown waxy clay, followed by fallout of pyroclastic ash. Both units were mostly eroded away prior to emplacement of a wet, cool pyroclastic surge which then buried and preserved in situ remnants of the herbaceous ground cover. Preservation of the semi-woody rhizomes implies well-drained soils, otherwise the plant material would have quickly rotted. Collections from discontinuous exposures indicate the grassland covered an area of at least a few hectares. This open grassland would have provided grazing for the Late Pliocene fauna.     

Fossil sedges, macroplants, and roots from Olduvai Gorge, Tanzania

A variety of macroplants has been recorded and collected from the eastern paleolake margin of Olduvai Gorge, Tanzania, from Upper Bed I and Lower Bed II, dated at ∼1.7-1.85 Ma. The plant groups represented are sedges, grasses, and woody and herbaceous dicotyledons. Most of these plants are fragmented, but the roots are in situ. The modes and quality of preservation, however, are very variable. Silicification is the dominant type of preservation; it ranges from high quality faithful replacement of cells resulting in silicified wood and sedge culms that are identifiable on the basis of their internal anatomy, to poor quality biotubes lacking internal anatomy or external features that prevent assignment to a specific plant or invertebrate origin. In between this range are silicified roots and grass culms identified by their external anatomy, and leaf and stem impressions. Interpretation of the paleoecology is limited by the quality of preservation. The in situ root horizons are useful for recognizing paleo-surfaces. The best quality preservation where internal anatomy is preserved occurs at HWK E and MCK, localities that are in the middle of the fault compartments so the vegetation can be reconstructed for these sites. Some sedge culms are described, illustrated, and identified as possible species of Cyperus, Fuirena, and Schoenoplectus.     

The O.H. 7 (Olduvai Gorge,Tanzania) hominid partial brain endocast revisited

The O.H.7 brain endocast was reexamined using a stereoplotting apparatus to quantify the amount of distortion. Some 127 measurements for each of the left and right sides were taken and treated statistically by student t-tests, both in paired and grouped fashion. Grouped data indicated no significant left-right differences. Paired data suggested three small regions of distortion, which produced three pairs of left-right differences that were significantly different. Given the very local nature of these minor distortions, it is concluded that the original reconstruction by Tobias was essentially correct. In addition, multiple regression analyses of selected chord-arc dimensions suggest that a volume in excess of 700 ml is most probable.     

Cranial remains of Homo erectus from Beds II and IV,Olduvai Gorge,Tanzania

Cranial remains of hominids 9 and 12 from Olduvai Gorge are described in detail. O.H. 9 consists of a heavily built braincase, partly damaged and lacking the face, while O.H. 12 is less complete. The Bed II specimen is about 1.2 million years in age and shows anatomical similarities to the cranium designated ER-3733 from Koobi Fora, east of Lake Turkana. Together these African fossils provide valuable information about Homo erectus in the later Lower Pleistocene. Comparisons of O.H. 9 with several of the Choukoutien crania are also carried out. These Chinese and other Asian remains of Homo erectus cannot be placed in a secure chronological framework, but all of the material should be studied systematically in order to assess relatedness among what must be several different populations.     

Middle Pleistocene hominids from Olduvai Gorge, northern Tanzania

Cranial, dental, and mandibular remains of eight Olduvai hominids are described in detail. Four individuals were recovered in situ in Beds II to IV, while three more are most probably derived from Bed IV, the Masek Beds and the Lower Ndutu Beds. One specimen is of uncertain provenance. Deposits from which the fossils were collected range from late Lower Pleistocene to Middle Pleistocene in age. Of particular interest are three fragmentary lower jaws, which can be compared to mandibles of Homo erectus known from localities in Northwest Africa and China. Olduvai hominid 22, a nearly complete half mandible with crowns of P3-M2 in place, shares many anatomical features with fossils from Ternifine and Choukoutien. This individual is also similar to a jaw from the Kapthurin Formation west of Lake Baringo, Kenya. How best to interpret these comparisons is not clear, but in view of marked similarities between specimens representing geographically diverse populations from different time periods, it may be unwise to rely on mandibular evidence alone to document the presence of regional lineages. Gradual change and continuity within a sequence of Northwest African Homo fossils has been endorsed by many workers, but such hypotheses cannot be tested adequately with the fragmentary jaws available.     

Vegetation and plant food reconstruction of lowermost Bed II, Olduvai Gorge, using modern analogs

Vegetation and plant foods for hominins of lowermost Bed II, Olduvai Gorge were modeled by examining vegetation in modern habitats in northern Tanzania (Lake Manyara, Ngorongoro, Serengeti) that are analogous to the paleolandscape in terms of climate, land forms, and soil types, as indicated by previous paleoenvironmental studies of Olduvai. Plant species in the modern habitats were identified in a series of sample plots, and those known to be eaten by modern humans, chimpanzees, or baboons were considered potentially edible for early hominins. Within the 50-80 kyr deposition of lowermost Bed II, periods of drier climate were characterized by low lake stands and a broad eastern lacustrine plain containing a mosaic of springs, marsh, woodland, and edaphic grassland. Based on results of this study, plant food diversity in each of those habitats was relatively low, but the mosaic nature of the area meant that hominins could reach several different habitat types within short distances, with access to potential plant foods including marsh plants, grass grains, roots, shrub fruits, edible parts from palms, leafy herbaceous plants, and Acacia pods, flowers, and gum. Based on Manyara analogs, a greater variety of plant foods, such as tree fruits (e.g., Ficus, Trichilia) and the roots and fruits of shrubs (e.g., Cordia, Salvadora) would be expected further east along the rivers in the lacustrine terrace and alluvial fans. Interfluves of the alluvial fans were probably less wooded and offered relatively fewer varieties of plant foods, but there is sparse paleoenvironmental evidence for the character of Olduvai's alluvial fans, making the choice of appropriate modern analogs difficult. In the western side of the basin, based on modern analogs in the Serengeti, riverine habitats provided the greatest variety of edible plant food species (e.g., Acacia, Grewia, Justicia). If the interfluves were grassland, then a large variety of potentially edible grasses and forbs were present seasonally. Periods of wetter climate resulted in a much expanded paleolake and a shrinking of the eastern lacustrine plain mosaic into a narrow zone. The dominant landscape features were then forest-lined rivers in the eastern alluvial fans, and rivers in the western side of the paleo-Olduvai basin were also better watered at these times, supporting denser woody vegetation with large varieties of edible fruits, leaves, and underground parts.     

The face of Olduvai Hominid 12

Facial remains of Homo erectus are rare and their scarcity hinders our understanding of the variability and relationships in this taxon. Previously undescribed fragments of the peri-orbital region and unidentified matches between fragments of Olduvai Hominid 12 (OH 12) enhance comparison of the African H. erectus hypodigm. The newly reconstructed upper face and maxilla of OH 12 is most similar in size and shape to that of KNM-ER 3733, despite being as much as one million years younger than the Koobi Fora hominin. However, the posterior vault and mastoid region of OH 12 are most similar to OH 9. This combination of morphology suggests that the relationship between the Olduvai and Koobi Fora portions of the H. erectus hypodigm requires reconsideration.     

Quantifying Oldowan Stone Tool Production at Olduvai Gorge,Tanzania

Recent research suggests that variation exists among and between Oldowan stone tool assemblages. Oldowan variation might represent differential constraints on raw materials used to produce these stone implements. Alternatively, variation among Oldowan assemblages could represent different methods that Oldowan producing hominins utilized to produce these lithic implements. Identifying differential patterns of stone tool production within the Oldowan has implications for assessing how stone tool technology evolved, how traditions of lithic production might have been culturally transmitted, and for defining the timing and scope of these evolutionary events. At present there is no null model to predict what morphological variation in the Oldowan should look like. Without such a model, quantifying whether Oldowan assemblages vary due to raw material constraints or whether they vary due to differences in production technique is not possible. This research establishes a null model for Oldowan lithic artifact morphological variation. To establish these expectations this research 1) models the expected range of variation through large scale reduction experiments, 2) develops an algorithm to categorize archaeological flakes based on how they are produced, and 3) statistically assesses the methods of production behavior used by Oldowan producing hominins at the site of DK from Olduvai Gorge, Tanzania via the experimental model. Results indicate that a subset of quartzite flakes deviate from the null expectations in a manner that demonstrates efficiency in flake manufacture, while some basalt flakes deviate from null expectations in a manner that demonstrates inefficiency in flake manufacture. The simultaneous presence of efficiency in stone tool production for one raw material (quartzite) and inefficiency in stone tool production for another raw material (basalt) suggests that Oldowan producing hominins at DK were able to mediate the economic costs associated with stone tool procurement by utilizing high-cost materials more efficiently than is expected and low-cost materials in an inefficient manner.     

Fine resolution of early hominin time, Beds I and II, Olduvai Gorge, Tanzania

Reconstructing paleoenvironments and landscapes within lake-centered, hominin-yielding basinal sequences requires a resolution of time-rock units finer than but complementary to that provided by the present tephrostratigraphy. Although indispensable in providing an absolute time frame at Olduvai, the average 15,000-20,000 year intervals between successive tuff units lack the time resolution to construct a sufficiently contemporary paleolandscape within sedimentary intervals away from the interleaved tuffs. Such control is essential to construct valid paleogeographies in which to contextualize contemporaneous paleoanthropological sites and the traces of hominin land use they contain. Within Beds I and II of the Olduvai Basin a Sequence Stratigraphic analysis has achieved a relative time framework in which time-rock units, “lake-parasequences,” each generated by a major advance and withdrawal of the lake system, are recognizable for average periods of about 4000 years duration. Within each of these time slices at least two paleogeographic landscapes are identifiable, reducing the time constraints of an individual landscape reconstruction to a few thousand years. Within the sedimentary succession both highly incised and less incised unconformities are identifiable to provide sequence boundaries. Within each sequence the higher frequency lake-parasequences can be identified by (1) a disconformable base, (2) accretion of sediment during lake transgression and at maximum, (3) a disconformable top caused by lake withdrawal, and (4) a soil profile generated beneath that disconformable land surface. Individual lake-parasequences can be recognized in lake marginal and fan settings, and their imprint can also be seen in the lake setting where, for example, maximum flooding might be marked by a layer of dolomite. Lower Bed II parasequences represent time intervals of <5000 years, while parasequential periods between Tuffs IB and IC in Bed I are <4300 years. Analogous Holocene lake-level changes of the same order in East Africa have a period close to 4200 years. The estimated period is close to that defined by Stadial/Interstadial Dansgaard-Oeschger Events recorded in the Greenland Ice record, which force cycles of period similar to lake-parasequences, both in the Arabian Sea and Lake Malawi. Lake-parasequences not only aid construction of landscapes, they also allow contextualization of individual paleoanthropological occurrences. For instance, a parasequence lies between Leakey’s Level 1 and her butchered Deinotherium occurrence at FLK N. However, elephantid and giraffid skeletons associated with stone artifacts at VEK, uncovered by OLAPP excavations, are situated on the same land surface as a possibly butchered rhinocerid at KK. To complement the existing absolute radiometric time framework, relative Sequence Stratigraphic techniques might be applied to any lake-centered, hominin-yielding basinal sequence, not only those found within East Africa. Because they are climatically controlled, and might plausibly be related to globally driven Dansgaard-Oeschger Events, lake-parasequences and their associated sequences might be correlatable between various East African basins in the Plio-Pleistocene in the same way as they presently are for the Holocene.     

The age and stratigraphic position of Olduvai Hominid I

A short history of Olduvai Hominid I is given. On the basis of absolute and relative dating its position in the Naisiusiu Bed, part of the former Bed V, is affirmed. Some connection, on morphological grounds, with other hominids in East Africa is postulated, as well as with cultural material.     

Soricidae (Mammalia) from the Early Pleistocene of Olduvai Gorge, Tanzania

Soricid remains collected from Bed I of Olduvai Gorge are described. The great majority of the specimens are mandibles. A survey of the mandibles of living African species revealed many differences in characters of the lower teeth and jaw that can be used for identification. On the basis of these characters, nine species are distinguished in the Olduvai collection, of which six are well enough preserved to permit a discussion of their relationships to living species. Three new species and one new subspecies are described. All the Olduvai shrews differ in some respects from their nearest living relatives; three species are close to species from Makapansgat, Swartkrans and Sterkfontein, RSA, though there appear to be slight differences. A change in the soricid fauna takes place within Bed I, interpreted as due to increasing aridity.     

A note on the Olduvai clavicular fragment

Certain features of the Olduvai clavicular fragment have been examined in the light of data already existing on the form of the clavicle in primates. Although similar to that of modern man, the fragment exhibits features which suggest that its function may have differed somewhat from that of the clavicle in man. The new information correlates well with that obtained from the fragmentary Sterkfontein scapula.     

Carbonate horizons, paleosols, and lake flooding cycles: Beds I and II of Olduvai Gorge, Tanzania

This study documents the petrology and stable isotope geochemistry of carbonates from six horizons from Beds I and II of Olduvai Gorge, Tanzania. The studied succession, immediately below and above Tuff IF, consists of interbedded waxy and earthy claystones with discrete carbonate horizons and thin sandstones. The succession was deposited in response to repeated flooding and withdrawal of a saline-alkaline lake. The carbonates and their overlying disconformities are important because they help define the surfaces on which hominin activity took place and allow very high-resolution correlation of geographically separated levels of hominin exploitation.The range of different carbonates includes unambiguous land-surface and pedogenic features including calcified rootmat horizons, rhizocretions, and micritic nodules, together with less determinate sparry calcite nodules. Stellate nodules are interpreted as pseudomorphs after sulfate-roses. The carbonate nodules are synsedimentary features, truncated by fluvial and other erosional surfaces. The isotopic composition of the carbonates is variable with δ¹⁸O ranging from −7.0‰ to −4.3‰, and δ¹³C from −8.5‰ to −1.6‰. A covariant increase in δ¹³C and δ¹⁸O repeats in each carbonate horizon and in individual nodules (inner to outer layers): it reflects the evolution of synsedimentary groundwaters. At times of low lake level, the carbonates started to precipitate from meteoric waters with low isotopic values and continued to form as lake levels rose and the waters became increasingly saline. Some of the samples have a last-stage cement of strontium rich dolomite, which supports late-stage flooding by the saline-alkaline lake. Previous studies of carbonate horizons from Olduvai have interpreted carbon isotope values in terms of changes in C₃ and C₄ plants that colonized the land surface. This study demonstrates that in some instances the isotope values from carbonates deposited in these lake marginal settings reflect changes in hydrology rather than vegetation.     

Earliest Porotic Hyperostosis on a 1.5-Million-Year-Old Hominin,Olduvai Gorge,Tanzania

Meat-eating was an important factor affecting early hominin brain expansion, social organization and geographic movement. Stone tool butchery marks on ungulate fossils in several African archaeological assemblages demonstrate a significant level of carnivory by Pleistocene hominins, but the discovery at Olduvai Gorge of a child''s pathological cranial fragments indicates that some hominins probably experienced scarcity of animal foods during various stages of their life histories. The child''s parietal fragments, excavated from 1.5-million-year-old sediments, show porotic hyperostosis, a pathology associated with anemia. Nutritional deficiencies, including anemia, are most common at weaning, when children lose passive immunity received through their mothers'' milk. Our results suggest, alternatively, that (1) the developmentally disruptive potential of weaning reached far beyond sedentary Holocene food-producing societies and into the early Pleistocene, or that (2) a hominin mother''s meat-deficient diet negatively altered the nutritional content of her breast milk to the extent that her nursing child ultimately died from malnourishment. Either way, this discovery highlights that by at least 1.5 million years ago early human physiology was already adapted to a diet that included the regular consumption of meat.     

Cranial capacity estimates for Olduvai Hominid 7

Estimation of cranial capacity for Olduvai Hominid (OH) 7 is determined from external parietal dimensions using multiple regressions calculated from an australopithecine grade sample. Capacity estimates for OH 7 (580–600 cc) are much lower than usually claimed. While differences in reconstruction may account for the varying estimates, a regression based only on undistorted and unreconstructed values, as well as a direct comparison of dimensions with other Homo habilis specimens, supports the smaller capacity determination.     

Tool-using strategies by early hominids at bed II, Olduvai Gorge, Tanzania

This study examines the current prevailing model of Oldowan technology-the opportunistic, least-effort strategy of stone tool making and using by early hominids. The sample includes the MNK chert factory site and three contemporaneous assemblages from Olduvai Gorge, all dated between 1.65 and 1.53 m.y.a. The analysis suggests that early hominids at Olduvai may have been selective, applying distinctive strategies in making and using tools depending on the different types of raw materials available to them. The preponderance of lava cores and near absence of flakes associated with the cores suggest that lava cores at Olduvai did not provide a source of flakes. They were primarily heavy-duty core tools, despite the fact that the majority of Olduvai lava is of excellent quality for flaking. Contrary to this pattern, the abundance of chert flakes and the lack of large chert cores suggest that the production of flakes was the most important strategy applied to chert. Original forms and flaking mechanics of the raw materials may have been important factors in the simultaneous application of the different, complementary strategies. The Oldowan tool-using strategy was dynamic and flexible, in response to changes in raw material availability. The use of chert between 1.65 and 1.53 m.y.a. was apparently related to the drastic decrease in flake production in lava and quartz. Finally, lack of initial reduction episodes of lava material challenges the idea of the stone cache strategy at Olduvai between 1.65 to 1.53 m.y.a.