Jackson K. Njau

Taphonomic, Avian, and Small-Vertebrate Indicators of Ardipithecus ramidus Habitat

Thousands of vertebrate specimens were systematically collected from the stratigraphic interval containing Ardipithecus ramidus. The carcasses of larger mammals were heavily ravaged by carnivores. Nearly 10,000 small-mammal remains appear to be derived primarily from decomposed owl pellets. The rich avifauna includes at least 29 species, mostly nonaquatic forms. Modern analogs of the most abundant birds and of a variety of rodents are associated with mesic woodland environments distant from large water bodies. These findings support inferences from associated geological, isotopic, invertebrate, and large-vertebrate assemblages. The combined results suggest that Ar. ramidus occupied a wooded Pliocene habitat.

A New Horned Crocodile from the Plio-Pleistocene Hominid Sites at Olduvai Gorge, Tanzania

Background The fossil record reveals surprising crocodile diversity in the Neogene of Africa, but relationships with their living relatives and the biogeographic origins of the modern African crocodylian fauna are poorly understood. A Plio-Pleistocene crocodile from Olduvai Gorge, Tanzania, represents a new extinct species and shows that high crocodylian diversity in Africa persisted after the Miocene. It had prominent triangular “horns” over the ears and a relatively deep snout, these resemble those of the recently extinct Malagasy crocodile Voay robustus, but the new species lacks features found among osteolaemines and shares derived similarities with living species of Crocodylus. Methodology/Principal Findings The holotype consists of a partial skull and skeleton and was collected on the surface between two tuffs dated to approximately 1.84 million years (Ma), in the same interval near the type localities for the hominids Homo habilis and Australopithecus boisei. It was compared with previously-collected material from Olduvai Gorge referable to the same species. Phylogenetic analysis places the new form within or adjacent to crown Crocodylus. Conclusions/Significance The new crocodile species was the largest predator encountered by our ancestors at Olduvai Gorge, as indicated by hominid specimens preserving crocodile bite marks from these sites. The new species also reinforces the emerging view of high crocodylian diversity throughout the Neogene, and it represents one of the few extinct species referable to crown genus Crocodylus.

Landscape distribution of Oldowan stone artifact assemblages across the fault compartments of the eastern Olduvai Lake Basin during early lowermost Bed II times.

The density and composition of Oldowan stone artifact assemblages deposited during the first ca. 20,000 years of lowermost Bed II times show a recurrent pattern of variation across recognized synsedimentary faults that compartmentalized landscapes of the eastern Olduvai Lake Basin. When active, the faults created minor topographic relief. The upthrown fault footwalls accumulated assemblages with relatively high densities of artifacts, including types retaining potential usefulness, particularly volcanic flaked pieces, manuports, pounded pieces, and split cobbles. Values for these assemblage characteristics decline toward the lower-lying hangingwall of the fault compartments, accompanied by an increase in the proportionate weight of artifact assemblages comprising quartzite, particularly flaking shatter and potentially useful detached pieces. Values reverse once again at faults, either on the downthrown, hangingwall side or on the upthrown side. The patterns are stronger for the volcanic components of the artifact assemblages than for the quartzite components, reflecting the additional influence of distance from the local source on quartzite assemblage characteristics reported previously. The landscape distributions of artifact assemblages are consistent with a landscape-fault model in which minor fault-induced topographic relief at times created a mosaic of vegetation environments repeated within each of the three fault compartments of the lake margin and distal alluvial fan. The fault-compartmentalized landscape model is currently supported only by sediment thickness and facies changes across synsedimentary faults, but it provides predictions for spatial variation in the cover abundance of trees, freshwater reservoirs and associated distributions of resources and hazards associated with stone artifact use and discard that can be tested if sample sizes of key paleoenvironmental indicators are increased.

Crocodylian and mammalian carnivore feeding traces on hominid fossils from FLK 22 and FLK NN 3, Plio-Pleistocene, Olduvai Gorge, Tanzania.

Taphonomic analysis of the Olduvai Hominid (OH) 8 left foot from FLK NN Level 3 and the OH 35 left leg from FLK Level 22 (Zinjanthropus level) in Middle Bed I, Olduvai Gorge, indicates that both were fed upon by crocodiles. Both bear extensive tooth marking, including bisected tooth marks diagnostic of crocodylian feeding. The location of the bisected tooth marks on the distal tibia and the talus indicates disarticulation of the foot by crocodiles. The broken proximal ends of the tibia and fibula are more typical of feeding by a leopard-like carnivore, as is damage to the OH 7 mandible and parietals that are associated with and may derive from the same individual as OH 8. Previous work showing a close articulation of the foot and the leg has been used to suggest that the two specimens belong to the same individual despite deriving from sites separated by 200 m and slightly different stratigraphic levels according to previous work. The location and agent of tooth marking and the nature of gross damage do not refute this hypothesis, but the punctures on the talus and distal tibia differ in size and sharpness. Recent work shows that the stratigraphic discrepancy between OH 8 and OH 35 is greater than previously thought, refuting the single-individual hypothesis. Although seemingly unlikely, this denotes that two hominids represented by rarely found leg and foot elements both lost their left foot to crocodiles at nearby sites within a 6,000 year interval. We cannot determine if the hominids were preyed upon by crocodiles or mammalian carnivores. However, the carnivore damage to them and associated faunal remains suggests that high predation risk constrained hominid activities involving discard of the stone artifacts found at these sites. This finding is inconsistent with the interpretation of the sites as home bases or living floors.

A new high-resolution 3-D quantitative method for identifying bone surface modifications with implications for the Early Stone Age archaeological record

Bone surface modifications have become important indicators of hominin behavior and ecology at prehistoric archaeological sites. However, the method by which we identify and interpret these marks remains largely unchanged despite decades of research, relying on qualitative criteria and lacking standardization between analysts. Recently, zooarchaeologists have begun using new technologies capable of capturing 3-D data from bone surface modifications to advance our knowledge of these informative traces. However, an important step in this research has been overlooked and after years of work, we lack both a universal and replicable protocol and an understanding of the precision of these techniques. Here we propose a new standard for identifying bone surface modifications using high-resolution 3-D data and offer a systematic and replicable approach for researchers to follow. Data were collected with a white-light non-contact confocal profilometer and analyzed with Digital Surfs Mountains® software. Our data show that when methods are standardized, results between researchers are statistically indistinguishable. Multivariate analyses using the measured parameters allow discrimination between stone tool cut marks and mammalian carnivore tooth marks with 97.5% accuracy. Application of this method to fossil specimens resulted in 100% correspondence with identifications made by an experienced analyst using macroscopic observations of qualitative features of bone surface modifications. High-resolution 3-D analyses of bone surface modifications have great potential to improve the reliability and accuracy of taphonomic research, but only if our methods are replicable and precise.

Crocodile ecology and the taphonomy of early Australasian sites

Abstract Humans and human ancestors have exploited wetland resources for at least two million years. The most significant predators in these landscapes are crocodiles, which leads to two potential taphonomic problems: 1) human-accumulated bones may become intermingled with crocodile-modified bones; and 2) hominins themselves may have been victims of crocodiles. Davidson and Solomon (1990) significantly contributed to this literature through theirsuggestion that a crocodile attack led to the tooth marks on the type specimen of Homo habilis (OH 7) found in Olduvai Gorge, Tanzania. The Australasian tropics were also home to a variety of crocodilian species, crocodile damage to hominin bones being inferred in Trinil and Sangiran, Java. Furthermore, two Pleistocene Australian archaeological sites have stone artefacts in association with crocodile-damaged bone. A referential taphonomic framework is needed to understand the degree and nature of crocodile-hominin interactions on paleolandscapes of Sunda, the ancient Pleistocene landmass incorporating the islands of SE Asia, and Sahul, the Pleistocene landmass of ancient Australia incorporating Papua New Guinea, Australia and Tasmania. This paper provides initial results from crocodile feeding experiments aimed at characterising feeding damage inflicted on bones by the largest extant Australasian crocodile, Crocodylus porosus. Due to close similarity among Crocodylus species in dental and cranial morphology there are some general patterns in the way they modify bones. However, some differences arise when the taphonomic signatures are compared to those of the Nile crocodile (Crocodylus niloticus). We suggest that these differences are attributable to evolved differences in the feeding ecologies of the two species.

Fine-tuning paleoanthropological reconnaissance with high-resolution satellite imagery: the discovery of 28 new sites in Tanzania

IntroductionFossils,artifacts, andtheirgeological settingsaretherawdata ofhuman evolutiondthey evince what actually happened when andwhere,and its ecological context. As such, field research representsthe essential foundation upon which the discipline of paleoan-thropology rests.Many discoveries aremadefromlargeoutcrops ofsedimentary rock in the East African Rift Valley, and researchershave thus concentrated explorations on these extensive exposures(e.g., Omo, Koobi Fora, Olduvai). However, smaller outcrops, wherehuman evolution may also be documented, have received littleattention. Due to fast infrastructure development and rapid pop-ulation growth in East Africa there is an urgent need to implementa research strategy that will increase our ability to identify smallerexposures.We have incorporated high resolution satellite imagery (HRSI)into our survey methodology, greatly improving our ability tosystematically locate and efficiently identify smaller outcrops (e.g.,<10 km

A one‐million‐year‐old hominid distal ulna from Olduvai Gorge, Tanzania

OBJECTIVE Our aim was to recover new evidence of the evolution of the hominid lineage. METHODS We undertook paleontological fieldwork at Olduvai Gorge, Tanzania, in one of the richest paleoanthropological sites in the world, documenting the evolution of our lineage and its environmental contexts over the last 2 million years. RESULTS During field work in 2012, the Olduvai Vertebrate Paleontology Project discovered the distal end of a hominid ulna (OH 82) on the north side of Olduvai Gorge a few meters west of the Third Fault, eroding from Bed III sediments that are ∼1 million years in age. DISCUSSION The size and morphology of this distal ulna falls within the normal range of variation seen in humans, although at the larger end of the distribution.

From the Oldowan to the Acheulean at Olduvai Gorge, Tanzania – An introduction to the special issue

Even before setting foot at Olduvai Gorge, Louis Leakey was certain that he would find handaxes there (Leakey, 1951). Apparently, he did so on the very first day of the 1931 expedition, the first that Louis Leakey ever conducted at Olduvai. More unexpectedly, Louis Leakey also found an archaic, handaxefree industry in the lower beds of Olduvai (Leakey et al., 1931), which then he formally termed Oldowan (Leakey, 1936). In one way or another, all studies on the transition from the Oldowan to the Acheulean in East Africa and elsewhere, stem from Louis Leakey’s (e.g., 1936, 1951) initial reports at Olduvai, the first site where a stratigraphic sequence showed that handaxes emerged after a coreand-flake technology.