Variation among early Homo crania from Olduvai Gorge and the Koobi Fora region

Fossils recognized as early Homo were discovered first at Olduvai Gorge in 1959 and 1960. Teeth, skull parts and hand bones representing three individuals were found in Bed I, and more material followed from Bed I and lower Bed II. By 1964, L.S.B. Leakey, P.V. Tobias, and J.R. Napier were ready to name Homo habilis. But almost as soon as they had, there was confusion over the hypodigm of the new species. Tobias himself suggested that OH 13 resembles Homo erectus from Java, and he noted that OH 16 has teeth as large as those of Australopithecus. By the early 1970s, however, Tobias had put these thoughts behind him and returned to the opinion that all of the Olduvai remains are Homo habilis. At about this time, important discoveries began to flow from the Koobi Fora region in Kenya. To most observers, crania such as KNM-ER 1470 confirmed the presence of Homo in East Africa at an early date. Some of the other specimens were problematical. A.C. Walker and R.E. Leakey raised the possibility that larger skulls including KNM-ER 1470 differ significantly from smaller-brained, small-toothed individuals such as KNM-ER 1813. Other workers emphasized that there are differences of shape as well as size among the hominids from Koobi Fora. There is now substantial support for the view that in the Turkana and perhaps also in the Olduvai assemblages, there is more variation than would be expected among male and female conspecifics. One way to approach this question of sorting would be to compare all of the new fossils against the original material from Olduvai which was used to characterize Homo habilis in 1964. A problem is that the Olduvai remains are fragmentary, and none of them provides much information about vault form or facial structure. An alternative is to work first with the better crania, even if these are from other sites. I have elected to treat KNM-ER 1470 and KNM-ER 1813 as key individuals. Comparisons are based on discrete anatomy and measurements. Metric results are displayed with ratio diagrams, by which similarity in proportions for several skulls can be assessed in respect to a single specimen selected as a standard. Crania from Olduvai examined in this way are generally smaller than KNM-ER 1470, although OH 7 has a relatively long parietal. In the Koobi Fora assemblage, there is variation in brow thickness, frontal flattening and parietal shape relative to KNM-ER 1470. These comparisons are instructive, but vault proportions do not help much with the sorting process. Contrasts in the face are much more striking. Measurements treated in ratio diagrams show that both KNM-ER 1813 and OH 24 have relatively short faces with low cheek bones, small orbits and low nasal openings. Also, they display more projection of the midfacial region, just below the nose. This is not readily interpreted to be a female characteristic, since in most hominoid primates the females tend to have flatter lower faces than the males. The obvious size differences among these individuals have usually been interpreted as sex dimorphism, but, in fact, two taxa may be sampled at Olduvai and in the Turkana basin at the beginning of the Pleistocene. One large-brained group made up of KNM-ER 1470, several other Koobi Fora specimens, and probably OH 7, can be called Homo habilis. If these skulls go with femora such as KNM-ER 1481 and the KNM-ER3228 hip, then this species is close in postcranial anatomy to Homo erectus. The other taxon, including small-brained individuals such as KNM-ER 1813 and probably OH 13, seems also to be Homo rather than Australopithecus. If the OH 62 skeleton is part of this assemblage, then the small hominids have postcranial proportions unlike those of Homo erectus. However, it is too early to point unequivocally to one or the other of these groups as the ancestors of later humans. Both differ from Homo erectus in important ways, and both need to be better understood before we can map the earliest history of the Homo clade. © 1993 Wiley-Liss, Inc.     

Forward from Taung

The hominine grade of organization should preferably be defined by those morphological characters of the braincase and face which are first recognizable in Homo erectus. Provisionally, then, Olduvai hominid 24 and East Rudolf 1470 are regarded as protanthropine, irrespective of whether they both belong to “Homo habilis” or not. It is possible that either or both of these hominids can be considered directly prehominine, while A. africanus reflects an earlier prehominine stage.     

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.     

Olduvai Bed I post-cranial fossils: A reassessment

New fossil specimens can be interpreted as strong indications that there were two Plio-Pleistocene hominid post-cranial morphotypes. This new evidence may alter the functional interpretations placed on the important specimens, OH 8 and OH 10 from Olduvai Gorge, Tanzania. When these interpretations are critically examined there is now doubt that the OH 8 foot belongs to Homo and that the OH 10 terminal plalanx is necessarily part of a functional limb complex like that of modern Man.     

Dental microwear texture analysis of hominins recovered by the Olduvai Landscape Paleoanthropology Project, 1995-2007

Dental microwear analysis has proven to be a valuable tool for the reconstruction of aspects of diet in early hominins. That said, sample sizes for some groups are small, decreasing our confidence that results are representative of a given taxon and making it difficult to assess within-species variation. Here we present microwear texture data for several new specimens of Homo habilis and Paranthropus boisei from Olduvai Gorge, bringing sample sizes for these species in line with those published for most other early hominins. These data are added to those published to date, and microwear textures of the enlarged sample of H. habilis (n = 10) and P. boisei (n = 9) are compared with one another and with those of other early hominins. New results confirm that P. boisei does not have microwear patterns expected of a hard-object specialist. Further, the separate texture complexity analyses of early Homo species suggest that Homo erectus ate a broader range of foods, at least in terms of hardness, than did H. habilis, P. boisei, or the “gracile” australopiths studied. Finally, differences in scale of maximum complexity and perhaps textural fill volume between H. habilis and H. erectus are noted, suggesting further possible differences between these species in diet.     

The mid-face of lower Pleistocene hominins and its bearing on the attribution of SK 847 and StW 53

SK 847 and StW 53 have often been cited as evidence for early Homo in South Africa. To examine whether midfacial morphology is in agreement with these attributions, we analyze Euclidean distances calculated from 3-D coordinates on the maxillae of SK 847 and StW 53, as well as Australopithecus africanus (Sts 5, Sts 71), Paranthropus robustus (SK 46, SK 48, SK 52, SK 83), early Homo (KNM-ER 1813, KNM-ER 1805, KNM-ER 3733, KNM-WT 15000), P. boisei (KNM-ER 406, KNM-WT 17000, KNM-WT 17400), Gorilla gorilla (n = 116), Homo sapiens (n = 342), Pan paniscus (n = 21) and P. troglodytes (n = 65). Multivariate analyses separate extant hominoids suggesting we have captured taxonomic affinity. With the exception of SK 847 and SK 52, South African fossils tend to cluster together. P. robustus differs substantially from East African robust megadonts. SK 847 and StW 53 resemble the East African Homo specimens that are the most australopith-like, such as KNM-WT 15000 and KNM-ER 1813. The resemblance between StW 53 and Homo is driven partly by similarities in maxillary size. When distances are scaled, StW 53 aligns with A. africanus, while SK 847 clusters primarily with early Homo.     

Improved age control on early Homo fossils from the upper Burgi Member at Koobi Fora,Kenya

To address questions regarding the evolutionary origin, radiation and dispersal of the genus Homo, it is crucial to be able to place the occurrence of hominin fossils in a high-resolution chronological framework. The period around 2 Ma (millions of years ago) in eastern Africa is of particular interest as it is at this time that a more substantial fossil record of the genus Homo is first found. Here we combine magnetostratigraphy and strontium (Sr) isotope stratigraphy to improve age control on hominin-bearing upper Burgi (UBU) deposits in Areas 105 and 131 on the Karari Ridge in the eastern Turkana Basin (Kenya). We identify the base of the Olduvai subchron (bC2n) plus a short isolated interval of consistently normal polarity that we interpret to be the Pre-Olduvai event. Combined with precession-forced (∼20 kyr [thousands of years]) wet–dry climate cycles resolved by Sr isotope ratios, the magnetostratigraphic data allow us to construct an age model for the UBU deposits. We provide detailed age constraints for 15 hominin fossils from Area 131, showing that key specimens such as cranium KNM-ER 1470, partial face KNM-ER 62000 and mandibles KNM-ER 1482, KNM-ER 1801, and KNM-ER 1802 can be constrained between 1.945 ± 0.004 and 2.058 ± 0.034 Ma, and thus older than previously estimated. The new ages are consistent with a temporal overlap of two species of early Homo that can be distinguished by their facial morphology. Further, our results show that in this time interval, hominins occurred throughout the wet–dry climate cycles, supporting the hypothesis that the lacustrine Turkana Basin was a refugium during regionally dry periods. By establishing the observed first appearance datum of a marine-derived stingray in UBU deposits at 2.058 ± 0.034 Ma, we show that at this time the Turkana Basin was hydrographically connected to the Indian Ocean, facilitating dispersal of fauna between these areas. From a biogeographical perspective, we propose that the Indian Ocean coastal strip should be considered as a possible source area for one or more of the multiple Homo species in the Turkana Basin from over 2 Ma onwards.     

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.     

A new species of the genusHomo (primates: Hominidae) from the Plio/Pleistocene of Koobi Fora,in Kenya

Reassessment of the hominine cranium, KNM-ER 1813, from the Plio/Pleistocene of Koobi Fora, in Kenya, shows that it is not a small-brained, extreme female variant ofH. habilis Leakey, Tobias, & Napier, 1964. Its cranial and dental morphology, morphometrics, and proportions do not conform with eitherH. habilis orH. antiquus Ferguson, 1984. On the basis of its distinctive morphological pattern and mensural gaps which distinguish it fromH. habilis andH. antiquus, the cranium KNM-ER 1813 is described as a common variant representing a male of a small-brained, intermediate population linkingH. habilis 1.83 Myr BP withH. antiquus 2.9 Myr BP, and a new paleospecies of the genusHomo. A key to the Homininae is provided and the phylogenetic relationship of KNM-ER 1813 toH. habilis andH. antiquus is discussed. This paper is dedicated to the memory of my wife,Grace, whose assistance will be sorely missed.     

A new species of cormorant (Aves: Phalacrocoracidae) from the Pleistocene of Olduvai Gorge,Tanzania

Phalacrocorax owrei nov. sp. is a small cormorant from the Lower Pleistocene of Olduvai Gorge. Osteological proportions are established for the four subgenera of Phalacrocorax, and P. owrei is assigned to the subgenus Stictocarbo. The species was the most abundant bird in the Bed I deposits and is also represented by a few specimens in the middle part of Bed II. Its last known appearance coincides with a change in the local environment when the climate became more arid and the Olduvai Lake became more saline and more alkaline. At other localities in Bed II the extinct P. tanzanice occurs, as well as P. africanus and P. corbo, which breed on the African lakes and seacoast today.     

Découverte d’un nouvel hominidé à Dmanissi (Transcaucasie,Géorgie)

Four human remains: one mandible, two skulls and one metatarsus were discovered between 1991 and 1999 at the open-air site of Dmanisi, Georgia, in a precise stratigraphic, palaeontological and archaeological context, in volcanic ashes dated to 1.81 ± 0.05 Ma. The first studies of these fossils enable the authors to compare them with the morphology of archaic African Homo erectus, ascribed to Homo ergaster, and to ascertain hominid presence at the gates of Europe 300 000 years earlier than the classical scenario forecasted. In September 2000, the discovery of a second more complete and robust mandible D 2600 presents a threefold interest: palaeontological, functional and pathological. A comparison with Homo habilis and Homo erectus leads to the recognition of a new Homo species: H. georgicus sp. nov. The morphofunctional characteristics and the antiquity of H. georgicus characterise the root of a long Eurasian line.     

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.     

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.     

Taxonomic attribution of the Olduvai hominid 7 manual remains and the functional interpretation of hand morphology in robust australopithecines

In this paper, we test the currently accepted taxonomic hypothesis that the hand of the Homo habilis holotype Olduvai hominid 7 (OH7) from Olduvai Gorge can be unambiguously assigned to Homo. Morphometric and morphological comparison with humans and australopithecines (Australopithecus and Paranthropus) indicate that the OH7 hand most likely belongs to P. boisei. The morphological adaptations of Paranthropus are thus further evaluated in the light of the alternative taxonomic hypothesis for OH7. Functional analyses suggest that morphological features related to human-like precision grasping, previously considered diagnostic of toolmaking by some, may be alternatively attributed to specialized manual feeding techniques in robust australopithecines.     

The Belohdelie frontal: new evidence of early hominid cranial morphology from the Afar of Ethiopia

Study of the Belohdelie frontal has demonstrated that this four-million-year-old specimen belongs to a very generalized hominid that may be close to the divergence point of the hominid and African ape clades. Features associated with the temporalis muscle in the Belohdelie frontal and other new hominids from Hadar (AL 333-125) and West Turkana (KNM-ER 17000) suggest that the earliest hominids shared a large anterior component of this muscle relative to the extinct and extant apes. Results of this study support the phylogenetic hypothesis put forward by many workers that A. afarensis gave rise to the “robust” Australopithecus and A. africanus clades.     

Body proportions of Homo habilis reviewed

The ratio of fore- to hindlimb size plays an important role in our understanding of human evolution. Although Homo habilis was relatively modern craniodentally, its body proportions are commonly believed to have been more apelike than in the earlier Australopithecus afarensis. The evidence for this, however, rests, on two fragmentary skeletons, OH 62 and KNM-ER 3735. The upper limb of the better-preserved OH 62 from Olduvai Gorge is long and slender, but its hindlimb is represented mainly by the proximal portion of a thin femur of uncertain length. The present analysis shows that upper-to-lower limb shaft proportions of both OH 62 and AL 288-1 (A. afarensis) fall in the modern human range of variation, although OH 62 also falls inside that of chimpanzees due to their overlap in small individuals. Despite being more fragmentary, the larger-bodied KNM-ER 3735 lies outside the chimpanzee range and close to the human mean. Because the differences between any of the three individuals are compatible with the range of variation seen in extant hominoid groups, it is not legitimate to infer more primitive upper-to-lower limb shaft proportions for either H. habilis or A. afarensis. Femur length of OH 62 can only be estimated by comparison. Its closest match in size and morphology is with the gracile OH 34 specimen, which therefore provides a better analogue for the reconstruction of OH 62 than the stocky AL 288-1 femur that is traditionally used. OH 34's slender proportions are hardly due to abrasion, but match those of a modern human of that body-size, suggesting that the relative length of OH 62's leg may have been human-like. Brachial proportions, however, remained primitive. Long legs may imply long distance terrestrial travel. Perhaps this adaptation evolved early in the genus Homo, with H. habilis providing an early representative of this important change.     

Metatarsal fusion pattern and developmental morphology of the Olduvai Hominid 8 foot: Evidence of adolescence

The morphology of the Olduvai Hominid (OH) 8 foot and the sequence of metatarsal epiphyseal fusion in modern humans and chimpanzees support the hypothesis that OH 8 belonged to an individual of approximately the same relative age as the OH 7 subadult, the holotype of Homo habilis. Modern humans and chimpanzees exhibit a variety of metatarsal epiphyseal fusion patterns, including one identical to that observed in OH 8 in which metatarsal 1 fuses before metatarsals 2-5. More than the metatarsal fusion sequence, however, the principal evidence of the youthful age of OH 8 lies in the morphology of metatarsals 1, 2, and 3. Because both OH 8 and OH 7 come from the same stratum at the FLK NN type site, the most parsimonious explanation of the OH 8 and OH 7 data is that this material belonged to the same individual, as originally proposed by Louis Leakey. The proposition that OH 8 belonged to an adult is unsupported by morphology, including radiographic evidence, and the fusion sequences in human and chimpanzee skeletal material reported here and in the literature.     

The puzzle from JK2—A femur and a tibial fragment (O.H.34) from Olduvai Gorge,Tanzania

During excavations in Bed III, Olduvai Gorge, Tanzania in 1962, a slender fossil femur and part of a tibial shaft were recovered. Their strange appearance resulted in their neglect for many years. Anatomical examination now confirms that these bones are hominid, probably hominine, yet distorted in form. The distortion does not appear to be the result of pathology but due to damage and abrasion while in the deposits; deposits dated at approximately 1 million years B.P. O.H. 34 is the first hominid to be recovered from Bed III, Olduvai Gorge.     

Assessing the longitudinal structure of the early hominid foot: A two-dimensional architecture analysis

Early hominid feet are often very fragmentary preserved and their architectural approaches stayed limited and subject to controversy. This study proposes an architectural analysis of the primate foot realised on dislocated skeleton. It is based on the angular analysis of geometrical relationships between the joint areas. We investigate the longitudinal structure of the primate foot and we present the results concerning someAustralopithecus afarensis specimens from Hadar (Ethiopia) and theHomo habilis Olduvai Hominid 8 foot (Tanzania). The architectural analysis argues for the lack of a longitudinal medial arch inA. afarensis, their joints being in neutral position. On the contrary, the more recent OH8 specimen is arched both medially and laterally.     

The taxonomic status ofpraeanthropus africanus (primates: Pongidae) from the late pliocene of Eastern Africa

The taxonPraeanthropus africanus (Weinert, 1950), represented by the Garusi maxilla, is valid and reinstated. The morphological pattern of the Garusi maxilla is not that of a primitive hominid, but of a relatively generalized pongid. Since the apelike lectotype L.H.-4 and paralectotype A.L.200-1a ofAustralopithecus afarensis Johanson et al. 1978 are conspecific withP. africanus, and originate from the same formation, they are reassigned toPraeanthropus africanus.