The upper limb of Paranthropus boisei from Ileret, Kenya
Introduction
Over six decades of discoveries and analyses have made Paranthropus boisei one of the best documented early hominin taxa in terms of its craniodental anatomy, diet, and biogeography. It is well known for a number of remarkably derived characteristics, including a structurally strong facial skeleton, large and anteriorly positioned attachments for chewing muscles, distinctive zygomatic shape, huge postcanine and small front teeth, and thicker enamel than found in any hominin or modern primate (Tobias, 1967, Rak, 1983, Smith et al., 2015). Its postcranial anatomy, however, has remained largely unknown, hampering our understanding of many important aspects of the paleobiology of this member of the human family tree.
Domínguez-Rodrigo et al. (2013) reported their breakthrough discovery of postcranial fossils associated with premolars reliably attributable to P. boisei. The associated remains (OH 80) include shaft fragments of a tibia and femur, a proximal radius, and a distal humerus fragment. OH 80 provides compelling evidence that the postcranial skeleton of P. boisei is robust compared with that of other hominins but leaves open many questions about the postcranial anatomy and paleobiology of this species.
Here, we report the discovery of the first upper limb skeleton, KNM-ER 47000 (Fig. 1), attributable to P. boisei. It provides evidence of scapular morphology, hand and upper limb proportions, upper limb robusticity, and locomotor and manual dexterity capabilities. We provide basic morphometric and comparative analyses with living hominoids and fossils attributed to Australopithecus, Paranthropus, and early Homo from eastern and South Africa.
Section snippets
Discovery and stratigraphic and paleoecological context
KNM-ER 47000 was found along the slope of an exposure in area 1A of the Koobi Fora Formation (Fig. 2), at the site FwJj14E where hominin footprints were later discovered as a result of our work to document the discovery of KNM-ER 47000 (Bennett et al., 2009, Dingwall et al., 2013, Hatala et al., 2016, Hatala et al., 2017). Hillary Sale found the first element, the right third metacarpal (MC), on July 12, 2004, near the end of the field season. Intensive survey led to the discovery of several
Preservation and morphology
Most of KNM-ER 47000's elements are well preserved, with undamaged and undistorted articular and shaft anatomy. The close spatial association of recovered fragments along with refitting pieces that display similar sediment abrasion and trampling damage indicates recent erosion from nearby exposures. In addition, dry bone fractures suggest this specimen was exposed for 1–3 years before burial (Behrensmeyer, 1978). The humerus has a tooth mark on the anterior distal shaft produced by a large
Scapular shape
Two scapular shape variables were considered to assess glenohumeral joint (ventral bar/glenoid angle) and scapular spine orientation (axillary border/spine angle). These two variables enable comparison of KNM-ER 47000 with representatives of Australopithecus afarensis (A.L. 288-1 [first order cast from the Cleveland Museum of Natural Sciences] and KSD-VP-1/1 [data from the study by Melillo, 2016]), Australopithecus africanus (Sts 7 and StW 162 [original fossils]); Australopithecus sediba (MH2
Scapula
Both KNM-ER 47000A and KNM-WT 15000 have ventral bar/glenoid angles that approach the modern human mean and fall in the upper ranges observed for nonhuman hominids. This morphology is indicative of a more derived, laterally oriented shoulder joint than typically occurs in apes and contrasts with the more cranial (ape-like) glenoid orientation seen in Australopithecus (Fig. 8). At the same time, the KNM-ER 47000A scapula possesses an obliquely oriented spine that suggests a narrow, long
Discussion
The Okote Member (1.4–1.6 Ma) near Ileret has yielded taxonomically identifiable craniodental remains of three hominin taxa: H. erectus, H. habilis, and P. boisei (Constantino and Wood, 2007, Spoor et al., 2007). The northern areas of the Koobi Fora Formation include some of the most intensively prospected and studied paleoanthropological regions in Africa, with a half-century of active research and sampling, making it unlikely that any other hominin taxon lived there at the time and has
Acknowledgments
This research would not have been possible without the support and assistance of the Ileret Community. Research was facilitated by a research permit issued to the collaborative project that included the National Museums of Kenya and colleagues at The George Washington University issued by the National Council of Science and Technology. We are also grateful for the continued enthusiasm and support of the students of the Koobi Fora Field School. We thank Hannah Carter-Menn and Kathryn C. Braun,
References (67)
Pleistocene fossil woods from the Okote Member, site FwJj 14 in the Ileret region, Koobi Fora Formation, northern Kenya
Journal of Human Evolution
(2017)- et al.
Hominin stature, body mass, and walking speed estimates based on 1.5 million-year-old fossil footprints at Ileret, Kenya
Journal of Human Evolution
(2013) - et al.
Evolution and homologies of primate and modern human hand and forearm muscles, with notes on thumb movements and tool use
Journal of Human Evolution
(2012) - et al.
Limb-size proportions in Australopithecus afarensis and Australopithecus africanus
Journal of Human Evolution
(2007) - et al.
Metacarpal proportions in Australopithecus africanus
Journal of Human Evolution
(2008) - et al.
Scapular anatomy of Paranthropus boisei from Ileret, Kenya
Journal of Human Evolution
(2018) - et al.
Principles for the virtual reconstruction of hominin crania
Journal of Human Evolution
(2009) - et al.
Hominin track assemblages from Okote Member deposits near Ileret, Kenya, and their implications for understanding fossil hominin paleobiology at 1.5 Ma
Journal of Human Evolution
(2017) - et al.
Cross-sectional properties of the humeral diaphysis of Paranthropus boisei: implications for upper limb function
Journal of Human Evolution
(2019) - et al.
Humeral anatomy of the KNM-ER 47000 upper limb skeleton from Ileret, Kenya: implications for taxonomic identification
Journal of Human Evolution
(2019)
Descriptions of the upper limb skeleton of Homo floresiensis
Journal of Human Evolution
A diagnosis of crocodile feeding traces on larger mammal bone, with fossil examples from the Plio-Pleistocene Olduvai Basin, Tanzania
Journal of Human Evolution
Landscape scale heterogeneity in the East Turkana ecosystem during the Okote Member (1.56–1.38 Ma)
Journal of Human Evolution
Biomechanics of phalangeal curvature
Journal of Human Evolution
Recently identified postcranial remains of Paranthropus and early Homo from Swartkrans Cave, South Africa
Journal of Human Evolution
Hand pressure distribution during Oldowan stone tool production
Journal of Human Evolution
The manual pressures of stone tool behaviors and their implications for the evolution of the human hand
Journal of Human Evolution
Morphological and taxonomic affinities of the Olduvai Ulna (OH36)
American Journal of Physical Anthropology
Taphonomic and ecologic information from bone weathering
Paleobiology
Early hominin foot morphology based on 1.5-million-year-old footprints from Ileret, Kenya
Science
Morphometric tools for landmark data: geometry and biology
Earliest known Oldowan artifacts at >2.58 Ma from Ledi-Geraru, Ethiopia, highlight early technological diversity
Proceedings of the National Academy of Sciences of the United States of America
Hominid carpal, metacarpal, and phalangeal bones recovered from the Hadar Formation: 1974-1977 collections
American Journal of Physical Anthropology
The upper limb of Australopithecus sediba
Science
The evolution of Zinjanthropus boisei
Evolutionary Anthropology
First Partial skeleton of a 1.34-million-year-old Paranthropus boisei from Bed II, Olduvai Gorge, Tanzania
PLoS ONE
Generalized procrustes analysis
Psychometrika
Australopithecus afarensis scapular ontogeny, function, and the role of climbing in human evolution
Science
Ontogeny of the hominoid scapula: the influence of locomotion on morphology
American Journal of Physical Anthropology
3.3-million-year-old stone tools from Lomekwi 3, West Turkana, Kenya
Nature
Footprints reveal direct evidence of group behavior and locomotion in Homo erectus
Scientific Reports
R: a language for data analysis and graphics
Journal of Computational and Graphical Statistics
Morphology of the Pliocene partial hominid skeleton (A.L. 288-1) from the Hadar Formation, Ethiopia
American Journal of Physical Anthropology
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2022, Journal of Human EvolutionCitation Excerpt :This fossil consists of a partial scapula, distal humerus, a good part of the shaft and proximal end of an ulna, three metacarpals, and three proximal phalanges, all from the right side. The fossil derives from the Okote Member of the Koobi Fora Formation and is geochronologically constrained by the Ileret Tuff (1.52 ± 0.01 Ma) above and the Lower Ileret Tuff (1.53 ± 0.01 Ma) below (Richmond et al., 2020). As such, it falls within the known geochronological ranges of both P. boisei and H. erectus.
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2022, Anthropologie (France)Citation Excerpt :Furthermore, according to Kivell et al. (2011), individuals belonging to a more recent Australopithecus species: A. sebiba (Malapa site, South Africa, 1.977 Ma) possessed forceful precision gripping and hand proportions that show enhanced dexterity, confirmed by other recent studies using trabecular bone analyses and musculoskeletal modeling (Bardo et al., 2018; Dunmore et al., 2020). Concerning Paranthropus genus, the anatomy of the hand of specimens belonging to P. boisei (e.g. specimens from East Turkana, Kenya), highlights that this species exhibit manual dexterity required to use or make stone tools, but did not possess the robust thumb observed in H. erectus, which are linked to the intensification of forceful precision grips and tool use (Richmond et al., 2020). In southern Africa, the remains (phalanges and metacarpals) discovered mainly from Member 1 and allocated to P. robustus (Susman, 1988, 1994, 1998), made it possible to highlight that these hominins possessed, in particular, the opposing muscle of the thumb and the fifth finger.