New fossils of Australopithecus anamensis from Kanapoi,West Turkana,Kenya (2003–2008)

Renewed fieldwork from 2003 through 2008 at the Australopithecus anamensis type-site of Kanapoi, Kenya, yielded nine new fossils attributable to this species. These fossils all date to between 4.195 and 4.108 million years ago. Most were recovered from the lower fluvial sequence at the site, with one from the lacustrine sequence deltaic sands that overlie the lower fluvial deposits but are still below the Kanapoi Tuff. The new specimens include a partial edentulous mandible, partial maxillary dentition, two partial mandibular dentitions, and five isolated teeth. The new Kanapoi hominin fossils increase the sample known from the earliest Australopithecus, and provide new insights into morphology within this taxon. They support the distinctiveness of the early A. anamensis fossils relative to earlier hominins and to the later Australopithecus afarensis. The new fossils do not appreciably extend the range of observed variation in A. anamensis from Kanapoi, with the exception of some slightly larger molars, and a canine tooth root that is the largest in the hominin fossil record. All of the Kanapoi hominins share a distinctive morphology of the canine–premolar complex, typical early hominin low canine crowns but with mesiodistally longer honing teeth than seen in A. afarensis, and large, probably dimorphic, canine tooth roots. The new Kanapoi specimens support the observation that canine crown height, morphology, root size and dimorphism were not altered from a primitive ape-like condition as part of a single event in human evolution, and that there may have been an adaptive difference in canine function between A. anamensis and A. afarensis.     

New hominid fossils from Woranso‐Mille (Central Afar,Ethiopia) and taxonomy of early Australopithecus

The phylogenetic relationship between Australopithecus anamensis and Australopithecus afarensis has been hypothesized as ancestor‐descendant. However, the weakest part of this hypothesis has been the absence of fossil samples between 3.6 and 3.9 million years ago. Here we describe new fossil specimens from the Woranso‐Mille site in Ethiopia that are directly relevant to this issue. They derive from sediments chronometrically dated to 3.57–3.8 million years ago. The new fossil specimens are largely isolated teeth, partial mandibles, and maxillae, and some postcranial fragments. However, they shed some light on the relationships between Au. anamensis and Au. afarensis. The dental morphology shows closer affinity with Au. anamensis from Allia Bay/Kanapoi (Kenya) and Asa Issie (Ethiopia) than with Au. afarensis from Hadar (Ethiopia). However, they are intermediate in dental and mandibular morphology between Au. anamensis and the older Au. afarensis material from Laetoli. The new fossils lend strong support to the hypothesized ancestor‐descendant relationship between these two early Australopithecus species. The Woranso‐Mille hominids cannot be unequivocally assigned to either taxon due to their dental morphological intermediacy. This could be an indication that the Kanapoi, Allia Bay, and Asa Issie Au. anamensis is the primitive form of Au. afarensis at Hadar with the Laetoli and Woranso‐Mille populations sampling a mosaic of morphological features from both ends. It is particularly difficult to draw a line between Au. anamensis and Au. afarensis in light of the new discoveries from Woranso‐Mille. The morphology provides no evidence that Au. afarensis and Au. anamensis represent distinct taxa. Am J Phys Anthropol 2010. © 2009 Wiley‐Liss, Inc.     

Australopithecus afarensis and the single species hypothesis

Ferguson (1989) has recently argued that the variability seen in the fossils assigned toA. afarensis is far more than expected for a single hominid species, and therefore proposes they represent multiple taxa. In particular, he utilizes data on variation in dental metrics and in premolar morphology in support of this hypothesis. A re-evaluation of these data finds the above conclusion to be unwarranted. Variation in dental metrics providesno basis for separating this sample into multiple taxa, regardless of the analog that is used (i.e. modern primate species or fossil hominid species). Additionally, data on P₃ morphology indicate that thepattern of variation seen in the Laetoli/Hadar sample is comparable to the sexual variation seenwithin a single hominoid species. Overall, the balance of the evidence at present indicates that the fossils from Laetoli and Hadar represent a single hominid species,A. afarensis.     

Evidence for a Late Pliocene faunal transition based on a new rodent assemblage from Oldowan locality Hadar A.L. 894, Afar Region, Ethiopia

The time interval between 3 Ma and 2 Ma marks several important transitions in human evolution, including the extinction of Australopithecus afarensis, the origin of the genus Homo, and the appearance of concentrated stone tool assemblages forming recognizable archaeological sites. The period also marks important changes in Earth’s climatic history, with the onset of northern hemisphere glaciation starting sometime between 2.8 Ma and 2.5 Ma, and it remains an unresolved question in paleoanthropology whether or not the global climatic events influenced in whole or in part, local terrestrial paleoenvironments in Africa and, through this, the course of human evolution.Changes in the terrestrial mammalian faunas of East Africa during this time interval are an important source of data about terrestrial paleoenvironments, and it has been argued that during this time period the mammalian faunas of Africa experienced a sudden pulse in the extinction and origination of taxa. The data corroborating this Turnover Pulse Hypothesis derive from both large mammal and micromammal data, though the fossil record of the former is much more abundant in this interval. New micromammal fossils recovered from ca. 2.4 Ma deposits at locality A.L. 894, low in the Busidima Formation in the Hadar study area of the Afar region, Ethiopia, reveal a significant faunal turnover when compared with previously published material from older 3.2 Ma micromammal assemblages from the Hadar Formation deposits. The results support the hypothesis of a major faunal transition, but larger sample sizes and more extensive temporal sampling are needed to refine the time and rate of change within this interval at Hadar.     

The paleoanthropology of Hadar,Ethiopia

Field research at the fossil-bearing deposits in the Afar Depression began in the 1970s. Prior to this, hominin fossils older than 3.0 Mya consisted of only a handful of fragments. During Phase I, the International Afar Research Expedition to Hadar, Ethiopia collected some 240 fossil hominins from Hadar over a time range of 3.0–3.4 Mya. Along with hominin fossils from Laetoli, they were deemed a new species, Australopithecus afarensis. This taxon was posited as the last common ancestor to robust Australopithecus and the Homo lineage in eastern Africa. Phase II research under the Hadar Research Project has added strength to the Phase I results, including the first association of a Homo fossil with stone tools at 2.4 Mya. This presentation is a cursory synopsis of the importance and implications of the hominin fossils recovered at Hadar during over the last 34 years.     

Phylogeny of early Australopithecus: new fossil evidence from the Woranso-Mille (central Afar,Ethiopia)

The earliest evidence of Australopithecus goes back to ca 4.2 Ma with the first recorded appearance of Australopithecus ‘anamensis’ at Kanapoi, Kenya. Australopithecus afarensis is well documented between 3.6 and 3.0 Ma mainly from deposits at Laetoli (Tanzania) and Hadar (Ethiopia). The phylogenetic relationship of these two ‘species’ is hypothesized as ancestor–descendant. However, the lack of fossil evidence from the time between 3.6 and 3.9 Ma has been one of its weakest points. Recent fieldwork in the Woranso-Mille study area in the Afar region of Ethiopia has yielded fossil hominids dated between 3.6 and 3.8 Ma. These new fossils play a significant role in testing the proposed relationship between Au. anamensis and Au. afarensis. The Woranso-Mille hominids (3.6–3.8 Ma) show a mosaic of primitive, predominantly Au. anamensis-like, and some derived (Au. afarensis-like) dentognathic features. Furthermore, they show that, as currently known, there are no discrete and functionally significant anatomical differences between Au. anamensis and Au. afarensis. Based on the currently available evidence, it appears that there is no compelling evidence to falsify the hypothesis of ‘chronospecies pair’ or ancestor–descendant relationship between Au. anamensis and Au. afarensis. Most importantly, however, the temporally and morphologically intermediate Woranso-Mille hominids indicate that the species names Au. afarensis and Au. anamensis do not refer to two real species, but rather to earlier and later representatives of a single phyletically evolving lineage. However, if retaining these two names is necessary for communication purposes, the Woranso-Mille hominids are best referred to as Au. anamensis based on new dentognathic evidence.     

An enlarged postcranial sample confirms Australopithecus afarensis dimorphism was similar to modern humans

In a previous study, we introduced the template method as a means of enlarging the Australopithecus afarensis postcranial sample to more accurately estimate its skeletal dimorphism. Results indicated dimorphism to be largely comparable to that of Homo sapiens. Some have since argued that our results were biased by artificial homogeneity in our Au. afarensis sample. Here we report the results from inclusion of 12 additional, newly reported, specimens. The results are consistent with those of our original study and with the hypothesis that early hominid demographic success derived from a reproductive strategy involving male provisioning of pair-bonded females.     

Cercopithecoid primate postcranial fossils from Cooper's D,South Africa

Among several highly fossiliferous localities in the Bloubank Valley (Gauteng, South Africa), the Cooper's Cave System has been known since 1938 and has produced a rich fossil assemblage, including some remains of the early hominin Paranthropus robustus. In 2001, excavations began at a new locality, Cooper's D, which dates to ～1.4-1.5 Ma. Although hominins are relatively rare in the assemblage, remains of cercopithecoid primates are much more common. Craniodental fossils currently indicate the possible presence of at least three large-bodied cercopithecoid primate genera at Cooper's D: Gorgopithecus, Papio, and Theropithecus. In this study, we identify and describe > 100 cercopithecoid primate postcranial fossils representing all regions of the appendicular skeleton. The specimens come from several age classes and size morphs; more than one third of the fossils described are from sub-adult and juvenile individuals. The adult postcranial fossils vary substantially in size, with body masses estimated between 30 and 60 kg (from 16 of the better preserved specimens). The functional morphology of the postcranial remains indicate that these elements come from animals that likely utilized terrestrial substrates, but they remain difficult to definitively attribute to Gorgopithecus, Theropithecus, or Papio given the absence of associated skeletons. The smaller specimens likely belong to Papio while the larger ones can be attributed to the other two genera. Because Cooper's D has also yielded fossils of the early hominin Paranthropus robustus, this raises the question of how these four large-bodied, mostly terrestrial primates sympatrically utilized the landscape.     

An alternative interpretation ofAustralopithecus afarensis fossil material

Hominoid fossils from Hadar, in Ethiopia and Laetoli, in Tanzania, and dated from the late Pliocene, were described as a new species of hominid, “Australopithecus afarensis,”Johanson, White andCoppens, 1978. A comparative morphological analysis of the lectotype and several paralectotypes reveal that that two taxa were synthesized and that “Australopithecus afarensis” represents a hominid and a pongid. The hominid is relatively unspecialized, and the pongid is remarkably similar toDryopithecus (Sivapithecus) sivalensis (Lydekker), 1879. The pongid is the first anthropoid ape recorded from the late Pliocene in Africa.     

Australopithecus afarensis : bipédie stricte ou associée à une composante arboricole ? Critiques et révision du matériel fémoral

Although much research has been carried out on Australopithecus afarensis locomotion, no consensus has yet been reached. Our new critic study on femoral material brings to the fore a strictly bipedal behaviour within this taxon. Our results are based on the pertinence of human anatomical characteristics among A. afarensis and on the absence of characteristics revealing arboreal displacement. These results have emerged from our different observation and interpretation of some preceding authors concerning the anatomy of these fossil hominids. It is important to underline that apomorphic characteristics of this species are difficult to interpret. They must not however be used to support the idea of arboreal displacement simply based on the fact of a no totally human morphe. We believe that present day humans do not necessarily reflect the earliest strict bipedal anatomic model. An the other hand, it appears that the disagreement between the two locomotor hypothesis for A. afarensis that are bipedalism and arboreal displacement, facing the possibility of bipedalism associated with negligible arboreal displacement, results more from an evolutionary fact than from a real scientific conflict.     

Reassessing manual proportions in Australopithecus afarensis

Previous analyses of hand morphology in Australopithecus afarensis have concluded that this taxon had modern human‐like manual proportions, with relatively long thumbs and short fingers. These conclusions are based on the A.L.333 composite fossil assemblage from Hadar, Ethiopia, and are premised on the ability to assign phalanges to a single individual, and to the correct side and digit. Neither assignment is secure, however, given the taphonomy and sample composition at A.L.333. We use a resampling approach that includes the entire assemblage of complete hand elements at Hadar, and takes into account uncertainties in identifying phalanges by individual, side and digit number. This approach provides the most conservative estimates of manual proportions in Au. afarensis. We resampled hand long bone lengths in Au. afarensis and extant hominoids, and obtained confidence limits for distributions of manual proportions in the latter. Results confirm that intrinsic manual proportions in Au. afarensis are dissimilar to Pan and Pongo. However, manual proportions in Au. afarensis often fall at the upper end of the distribution in Gorilla, and very lower end in Homo, corresponding to disproportionately short thumbs and long medial digits in Homo. This suggests that manual proportions in Au. afarensis, particularly metacarpal proportions, were not as derived towards Homo as previously described, but rather are intermediate between gorillas and humans. Functionally, these results suggest Au. afarensis could not produce precision grips with the same efficiency as modern humans, which may in part account for the absence of lithic technology in this fossil taxon. Am J Phys Anthropol 152:393–406, 2013. © 2013 Wiley Periodicals, Inc.     

Premolar microwear and tooth use in Australopithecus afarensis

The mandibular third premolar (P₃) of Australopithecus afarensis is notable for extensive morphological variability (e.g., metaconid presence/absence, closure of the anterior fovea, root number) and temporal trends in crown length and shape change over its 700 Ka time range. Hominins preceding A. afarensis have unicuspid, mesiodistally elongated P₃s with smaller talonids, and subsequent australopiths have bicuspid, more symmetrically-shaped P₃ crowns with expanded talonids. For these features, A. afarensis is intermediate and, thus, evinces the incipient stages of P₃ molarization. Here, we examine A. afarensis P₃ Phase II microwear and compare it with that of Australopithecus africanus and Cercocebus atys, an extant hard-object specialist, to assess whether the role of the P₃ in food processing changed over time in A. afarensis. Premolar Phase II microwear textures are also compared with those of the molars to look for evidence of functional differentiation along the tooth row (i.e., that foods with different mechanical properties were processed by separate regions of the postcanine battery). Microwear textures were also examined along the mesial protoconid crest, the site of occlusion with the maxillary canine, of the A. afarensis P₃ and compared with the same region in Pan troglodytes to determine whether microwear can be useful for identifying changes in the occlusal relationship between the P₃ and maxillary canine in early Australopithecus. Finally, temporal trends in P₃ Phase II and mesial microwear are considered. Results indicate that 1) both the P₃ and molar Phase II facets of A. afarensis have less complex microwear textures than in A. africanus or C. atys; 2) A. afarensis P₃ and molar Phase II textures differ, though not to the extent seen in taxa that eat hard and tough items; 3) microwear along the A. afarensis mesial protoconid crest is clearly distinct from that of the P. troglodytes, indicating that there is no honing equivalent in A. afarensis; and 4) there is little evidence of change over time in A. afarensis P₃ microwear on either the mesial or Phase II facet. In sum, these results provide no evidence that A. afarensis routinely loaded either its premolars or molars to process hard objects or that A. afarensis P₃ function changed over time.     

The geological context of the Kanapoi fossil hominids

Recent study of the geological succession at Kanapoi reveals that there are at least three series of sediments younger than the early Pliocene Kanapoi sediments which repose unconformably on them. Both sets of terrace and placage deposits contain an admixture of reworked Pliocene fossils and younger fossils preserved at the time of deposition of the younger sediments. This discovery throws doubt on the homogeneous nature of the Kanapoi fossil hominid sample, and suggests instead thatAustralopithecus anamensis may consist of a chimera of an early Pliocene hominid with generally ape-like dentognathic and postcranial anatomy and considerably youngerHomo specimens with more human-like post-cranial bones.     

The alpha taxonomy of Australopithecus at Sterkfontein: The postcranial evidence

The possibility that the fossils attributed to Australopithecus africanus represent more than a single species is of significance because of the pivotal role that A. africanus has played in discussions about hominin evolution. The A. africanus hypodigm that is currently widely recognized evinces considerable variation in a number of craniodental characters, and this has led to speculation that more than one australopith taxon may be represented among the specimens from Sterkfontein. Although crania, mandibles and teeth have dominated these taxonomic discussions, the Sterkfontein postcranial remains also have been invoked. While several workers have proposed that some of the craniodental remains from Sterkfontein can be partitioned into two groups, there is a notable lack of agreement among them as to their actual sorting. Most of the craniodental observations that have been put forward in support of arguments for taxonomic heterogeneity of the Sterkfontein australopith assemblage have been subjective and anecdotal in nature. So too, the postcranial evidence that has been cited in support of more than one australopith species at Sterkfontein has been largely subjective, and limited to a small number of elements. The results of quantitative statistical analyses of the craniodental and postcranial fossils that have been undertaken to date are not necessarily consistent with the hypothesis of taxonomic heterogeneity.     

New proconsuloid postcranials from the early Miocene of Kenya

New early Miocene forelimb fossils have been recovered from the Songhor and Lower Kapurtay localities in southwestern Kenya. We describe four specimens that are similar in size and functional capabilities. Their specific allocation is problematic but these forelimb specimens must belong to either Rangwapithecus gordoni or Proconsul africanus. If these new postcranial specimens should belong to R. gordoni, on the basis of size and common dental specimens found at Songhor, they represent a new elbow complex. The morphology of these fossils is anatomically and functionally similar to that of Proconsul. The proconsuloid elbow complex allows extensive forelimb rotations and is capable of performing arboreal quadrupedalism and climbing activities. No suspensory adaptations are apparent. The proconsuloid elbow complex remains a good ancestral condition for hominoid primates.     

French Contribution to the study of Human Origins: The case ofAustralopithecus afarensis

For a long time, French scientists have been involved in the study of human evolution and especially of human origins. Their key works in Eastern Africa have led to the discovery of major fossil hominid sites, especially in the Afar region in Ethiopia, where numerous remains ofAustralopithecus afarensis have been unearthed. The major contribution of the French scholars to the interpretation of the Hadar sample was to demonstrate the impact of the postcranial features on taxonomy and phylogeny. Two groups were identified in the sample and by comparison with modern populations of wild primates, these groups are assigned to different taxa. The other major impact was to show that early hominid bipedalism was an exact replica of modern human bipedality.     

Fossil Tragelaphini (Artiodactyla: Bovidae) from the Late Pliocene Hadar Formation,Afar Regional State,Ethiopia

The fossil tragelaphins from the late Pliocene of Hadar are described. These are Tragelaphus lockwoodi, new species, and Tragelaphus aff. T. nakuae. Tragelaphus lockwoodi bears long horns that define one complete spiral and that are mediolaterally compressed at the base. In these and other morphological characteristics it approaches the greater kudu, T. strepsiceros, and makes a good ancestral candidate for this living species. The Hadar T. aff. T. nakuae is similar to other specimens of this species from sites >2.8 Ma in East Africa and demonstrates well the major differences between the earlier and later representatives of this taxon. The sizes and morphological variation in the large Hadar T. aff. T. nakuae sample supports the idea that female individuals of this species were horned as is the case today in the elands and the bongo. Tragelaphus lockwoodi is present only in the lower beds of the Hadar Formation, and in small numbers, while T. aff. T. nakuae is recovered in relative abundance from throughout the ca. 3.4-ca. 2.9 Ma sequence.     

Size and shape variation in Australopithecus afarensis proximal femora

The degree of size and shape variation in the A. afarensis fossil sample has been interpreted in a variety of ways. Size variation has been described as exceeding that of extant hominoids, similar to that of strongly sexually dimorphic hominoids, and best matched to modern humans. The degree of shape variation has been characterized both as great and negligible. Recent fieldwork has increased the proximal femoral sample, providing new data with which to examine variation. The proximal femur of A. afarensis is analyzed in a comparative framework in order to gauge the magnitude of size and shape variation in this element.Seven of the best-preserved A. afarensis proximal femora contribute to the analysis (A.L. 128-1, A.L. 152-2, A.L. 211-1, A.L. 288-1ap, A.L. 333-3, A.L. 333-123, A.L. 827-1). Comparative samples from Pan, Pongo, Gorilla, and Homo provide context for interpreting variation among the fossils. The coefficient of variation (CV) of linear measurements is used to estimate size variation. Bootstrap resampling of CVs from extant hominoids provides distributions for comparison to A. afarensis CVs. Ratios of linear measurements provide scale-free shape variables that are used in pairwise comparisons. The Euclidean distance between pairs of A. afarensis are compared to the Euclidean distances between extant hominoid pairs.As found in some earlier analyses, size variation in A. afarensis is accommodated best in gorillas and orangutans. The magnitude of difference in shape between A. afarensis pairs is exceeded by most taxa, indicating that shape variation is not extreme. These general findings are contradicted by a few instances of excessive size and shape variation. These are uncharacteristic results and could point to temporal bias, although other alternatives are explored. The signal from the proximal femur is that size variation in A. afarensis is like that of the strongly sexually dimorphic apes, and shape variation is well within the range of most hominoids irrespective of their degree of size dimorphism.     

Four-million-year-Old hominids from East Lake Turkana,Kenya

A piece of mandible and several isolated teeth are reported from fluviatile sediments older than 4 million years at East Lake Turkana. They most closely resemble hominids from Laetoli, Tanzania and Hadar, Ethiopia which have been assigned to Australopithecus afarensis. © 1994 Wiley-Liss, Inc.