Dental microwear of Neogene cercopithecoids from the Turkana Basin, Kenya

Journal of Human Evolution · 2025-02-17 · 4 citations

Eighteen million years of diverse enamel proteomes from the East African Rift

Nature · 2025-07-09 · 8 citations

Research into the palaeobiology of extinct taxa through ancient DNA and proteomics has been mostly limited to Plio-Pleistocene fossils1–9, due to molecular breakdown over time, which is exacerbated in tropical settings1–3. Here we sample small proteomes from the interior enamel of fossils at palaeontological sites from the Pleistocene to the Oligocene in the Turkana Basin, Kenya, which has produced a rich record of Cenozoic mammalian evolution10. Through a mass-spectrometry-based proteomic workflow, and using criteria to locate diagenetiforms derived from enamel, we recover fragments of enamelin, ameloblastin, matrix metalloprotease-20 and dentin matrix acidic phosphoprotein 1 from an Early Miocene rhinocerotid and several proboscideans collected from the sites of Buluk (16 million years ago; Ma) and Loperot (18 Ma). Diagenetiform counts decline in progressively older fossils, and we observe variability in Early Miocene preservation across sites. Phylogenetic analyses reveal the contribution of these sequences to the systematic placement of extinct taxa, although we caution that this approach must account for sparse fragments, uncertainty in fragment identification and possible sequence diagenesis. We identify likely modifications that support the ancient age of these proteins, and some of the oldest examples of advanced glycation end-products yet known. The discovery of protein sequences within dense enamel tissues in one of the persistently warmest regions on Earth promises the discovery of much older proteomes that will aid in the study of the palaeobiology and evolutionary relationships of extinct taxa. The isolation of dental proteins from fossils deposited 1.5 million to 18 million years ago in the Turkana Basin in Kenya, a tropical region, demonstrate the promise of dental enamel for palaeoproteomic and evolutionary studies.

Empirical Test of the Relationship Between Pelvic Organs and Pelvic Cavity Dimensions as an Explanation for Female‐Biased Pelvic Sex Differences

American Journal of Biological Anthropology · 2025-06-01

OBJECTIVES: Growing evidence obfuscates the role obstetrics is thought to have played in the evolution of female-biased pelvic dimorphism. An alternative explanation is offered by the "Virile, Active Gonads and Genitalia in Nether Area (VAGGINA) hypothesis," which posits that females' larger pelvic organs drive female-biased pelvic dimorphism. The present study tests this hypothesis by evaluating whether females have larger pelvic organs than males and whether dimensions of pelvic organs influence those of the bony pelvic cavity. MATERIALS AND METHODS: Non-pathological pelvic MRIs were compiled from de-identified patients evaluated at Stony Brook University Hospital. Organ and pelvic cavity volumes were determined from segmented structures. Mediolateral and anteroposterior organ and pelvic cavity dimensions were derived from landmark data. T-tests and ordinary least squares regression were employed to test specific predictions of the "VAGGINA hypothesis." RESULTS: Comparisons of non-reproductive pelvic organ dimensions varyingly demonstrate both female- and male-biased dimorphism. Reproductive organs, however, demonstrate female-biased dimorphism of such magnitude that female-biased dimorphism is retained in analyses of summed pelvic organs. Despite this sexual dimorphism in organ dimensions, organ dimensions do not have a predictive relationship with corresponding bony pelvic cavity dimensions. DISCUSSION: The central argument of the "VAGGINA hypothesis," that large pelvic organs produce large bony pelves, is not supported, indicating more work is needed to understand what forces cause female-biased pelvic dimorphism. Future research may benefit from broader comparative and evolutionary contexts by exploring phylogenetic signals in female pelvic morphology.

Revised Body Mass Estimates for Extinct Lemurs

American Journal of Biological Anthropology · 2025-11-01 · 1 citations

ABSTRACT Objectives Body mass estimates for extinct animals are critical for informing hypotheses and analyses related to behavioral ecology, extinction risk, and locomotor modes. These estimates underpin reconstructions of behavioral ecology, especially for Madagascar's extinct subfossil lemurs. Previous estimates, based on femoral and humeral midshaft cortical areas, did not account for phylogenetic relatedness, potentially impacting their accuracy. This study updates body mass estimates for extinct lemurs using phylogenetically informed methods. Materials and Methods We analyzed 64 femora from 10 extinct lemur species. Each specimen was scanned using a Bruker SkyScan 1178 micro‐CT scanner to obtain high‐resolution images of femoral cortical areas. These data were combined to form a dataset comprising more than 125 subfossil lemur specimens across 15 identifiable species. Phylogenetically informed regression models (pGLS) incorporating femoral cortical surface area (FCSA) and femoral length (FL) as predictors were applied. Model fits were evaluated using Akaike information criterion (AIC) and adjusted R 2 values to determine the optimal predictors of body mass (BM). Results Natural log‐transformed FCSA emerged as the best predictor of natural log‐transformed BM among living primates. This pGLS regression equation was used to estimate body mass and lower and upper 95% prediction limits for all subfossil specimens, and weighted average BM estimates were obtained for each species. Our updated body mass estimates are consistently smaller than those previously reported. Discussion These estimates provide a more accurate basis for understanding extinct lemur life history traits, morphometrics, and ecological adaptations. These findings underscore the importance of incorporating evolutionary context in paleontological and ecological research.

An ape partial postcranial skeleton (KNM-NP 64631) from the Middle Miocene of Napudet, northern Kenya

Journal of Human Evolution · 2024-06-05 · 6 citations

African apes and the evolutionary history of orthogrady and bipedalism

American Journal of Physical Anthropology · 2023 · 32 citations

• Evolutionary biology
• Biology
• Paleontology

Abstract Since the first discovery of human fossils in the mid‐19th century, two subjects—our phylogenetic relationship to living and fossil apes and the ancestral locomotor behaviors preceding bipedalism—have driven the majority of discourse in the study of human origins. With few fossils and thus limited comparative evidence available to inform or constrain them, morphologists of the 19th and early mid‐20th centuries posited a range of scenarios for the evolution of bipedalism. In contrast, there exists a rich hominin fossil record and the acceptance of Pan (chimpanzees and bonobos) as our closest living relatives is nearly universal, yet consensus about the ancestral condition from which hominins evolved remains elusive. Notably, while the earliest known hominins are generally congruent with parsimonious inferences of an African ape‐like last common ancestor, our more distantly related Miocene ape cousins are frequently invoked as evidence in favor of more complex scenarios that require substantial homoplasy. Debate over these alternatives suggests that how we infer ancestral nodes and weigh evidence to test their relative likelihoods remains a stumbling block. Here we argue that a key contributor to this impasse includes the history of terminology associated with positional behavior, which has become confused over the last century. We aim to clarify positional behavior concepts and contextualize knuckle‐walking and other forms of posture and locomotion chimpanzees and gorillas engage in, while arguing that the presence of homoplasy in ape evolution does not alter the weight of evidence in favor of an African ape‐like evolutionary history of hominins.

Presence of a giant amphicyonid and other carnivores (Mammalia) from the Middle Miocene of Napudet, Kenya

Journal of Vertebrate Paleontology · 2022-08-31 · 1 citations

Morphological affinities of a fossil ulna (KNM-WS 65401) from Buluk, Kenya

Journal of Human Evolution · 2022-04-04 · 9 citations

Only the Good Die Old? Ontogenetic Determinants of Locomotor Performance in Eastern Cottontail Rabbits (<i>Sylvilagus floridanus</i>)

Integrative Organismal Biology · 2022-01-01 · 8 citations

Synopsis For many animals, the juvenile stage of life can be particularly perilous. Once independent, immature animals must often complete the same basic survival functions as adults despite smaller body size and other growth-related limits on performance. Because, by definition, juveniles have yet to reproduce, we should expect strong selection for mechanisms to offset these ontogenetic limitations, allowing individuals to reach reproductive adulthood and maintain Darwinian fitness. We use an integrated ontogenetic dataset on morphology, locomotor performance, and longevity in wild cottontail rabbits (Sylvilagus floridanus, Allen 1848) to test the hypothesis that prey animals are under selective pressure to maximize juvenile performance. We predicted that (1) juveniles would accelerate more quickly than adults, allowing them to reach adult-like escape speeds, and (2) juveniles with greater levels of performance should survive for longer durations in the wild, thus increasing their reproductive potential. Using high-speed video and force platform measurements, we quantified burst acceleration, escape speed, and mechanical power production in 38 wild-caught S. floridanus (26 juveniles, 12 adults; all rabbits &amp;gt;1 kg in body mass were designated to be adults, based on published growth curves and evidence of epiphyseal fusion). A subsample of 22 rabbits (15 juveniles, 7 adults) was fitted with radio-telemetry collars for documenting survivorship in the wild. We found that acceleration and escape speed peaked in the late juvenile period in S. floridanus, at an age range that coincides with a period of pronounced demographic attrition in wild populations. Differences in mass-specific mechanical power production explained ∼75% of the variation in acceleration across the dataset, indicating that juvenile rabbits outpace adults by producing more power per unit body mass. We found a positive, though non-significant, association between peak escape speed and survivorship duration in the wild, suggesting a complex relationship between locomotor performance and fitness in growing S. floridanus.

Author response: New fossils of Australopithecus sediba reveal a nearly complete lower back

2021-09-02

Article Figures and data Abstract eLife digest Introduction Results Discussion Materials and methods Appendix 1 Data availability References Decision letter Author response Article and author information Metrics Abstract Adaptations of the lower back to bipedalism are frequently discussed but infrequently demonstrated in early fossil hominins. Newly discovered lumbar vertebrae contribute to a near-complete lower back of Malapa Hominin 2 (MH2), offering additional insights into posture and locomotion in Australopithecus sediba. We show that MH2 possessed a lower back consistent with lumbar lordosis and other adaptations to bipedalism, including an increase in the width of intervertebral articular facets from the upper to lower lumbar column (‘pyramidal configuration’). These results contrast with some recent work on lordosis in fossil hominins, where MH2 was argued to demonstrate no appreciable lordosis (‘hypolordosis’) similar to Neandertals. Our three-dimensional geometric morphometric (3D GM) analyses show that MH2’s nearly complete middle lumbar vertebra is human-like in overall shape but its vertebral body is somewhat intermediate in shape between modern humans and great apes. Additionally, it bears long, cranially and ventrally oriented costal (transverse) processes, implying powerful trunk musculature. We interpret this combination of features to indicate that A. sediba used its lower back in both bipedal and arboreal positional behaviors, as previously suggested based on multiple lines of evidence from other parts of the skeleton and reconstructed paleobiology of A. sediba. eLife digest One of the defining features of humans is our ability to walk comfortably on two legs. To achieve this, our skeletons have evolved certain physical characteristics. For example, the lower part of the human spine has a forward curve that supports an upright posture; whereas the lower backs of chimpanzees and other apes – which walk around on four limbs and spend much of their time in trees – lack this curvature. Studying the fossilized back bones of ancient human remains can help us to understand how we evolved these features, and whether our ancestors moved in a similar way. Australopithecus sediba was a close-relative of modern humans that lived about two million years ago. In 2008, fossils from an adult female were discovered at a cave site in South Africa called Malapa. However, the fossils of the lower back region were incomplete, so it was unclear whether the female – referred to as Malapa Hominin 2 (MH2) – had a forward-curving spine and other adaptations needed to walk on two legs. Here, Williams et al. report the discovery of new A. sediba fossils from Malapa. The new fossils are mainly bones from the lower back, and they fit together with the previously discovered MH2 fossils, providing a nearly complete lower spine. Analysis of the fossils suggested that MH2 would have had an upright posture and comfortably walked on two legs, and the curvature of their lower back was similar to modern females. However, other aspects of the bones’ shape suggest that as well as walking, A. sediba probably spent a significant amount of time climbing in trees. The findings of Williams et al. provide new insights in to our evolutionary history, and ultimately, our place in the natural world around us. Our lower back is prone to injury and pain associated with posture, pregnancy and exercise (or lack thereof). Therefore, understanding how the lower back evolved may help us to learn how to prevent injuries and maintain a healthy back. Introduction Bipedal locomotion is thought to be one of the earliest and most extensive adaptations in the hominin lineage, potentially evolving initially 6–7 million years (Ma) ago. Human-like bipedalism evolved gradually, however, and early hominins appear to have been facultative bipeds on the ground and competent climbers in the trees (Senut et al., 2001; White et al., 2015; Prang, 2019; Prang et al., 2021). How long climbing adaptations persisted in hominins and when adaptations to obligate terrestrial bipedalism evolved are major outstanding questions in paleoanthropology. Australopithecus sediba – an early Pleistocene (~2 Ma) hominin from the site of Malapa, Gauteng province, South Africa – has featured prominently in these discussions, as well as those concerning the origins of the genus Homo (Berger et al., 2010; Berger, 2012; Irish et al., 2013; Dembo et al., 2015; Kimbel and Rak, 2017; De Ruiter et al., 2018; Williams et al., 2018a; Du and Alemseged, 2019). Previous studies support the hypothesis that A. sediba possessed adaptations to arboreal locomotion and lacked traits reflecting a form of obligate terrestriality observed in later hominins (Schmid et al., 2013; Prang, 2015a; Prang, 2015b; Prang, 2016; Holliday et al., 2018). Malapa Hominin 2 (MH2) metacarpals are characterized by trabecular density most similar to orangutans, which suggests power grasping capabilities (Dunmore et al., 2020), and the MH2 ulna was estimated to reflect a high proportion of forelimb suspension in the locomotor repertoire of A. sediba (Rein et al., 2017). Evidence from the lower limb also suggests that A. sediba lacked a robust calcaneal tuber (Prang, 2015a) and a longitudinal arch (Prang, 2015b), both thought to be adaptations to obligate, human-like bipedalism, and demonstrates evidence for a mobile subtalar joint proposed to be adaptively significant for vertical climbing and other arboreal locomotor behaviors (Prang, 2016; DeSilva et al., 2013; Zipfel et al., 2011; DeSilva et al., 2018). The upper thorax (Schmid et al., 2013), scapula (Churchill et al., 2013; Churchill et al., 2018), and cervical vertebrae (Meyer et al., 2017) of A. sediba suggest shoulder and arm elevation indicative of arboreal positional behaviors requiring overhead arm positions, and the limb joint size proportions are ape-like (Prabhat et al., 2021). Furthermore, analysis of dental calculus from Malapa Hominin 1 (MH1) indicates that this individual’s diet was high in C3 plants like fruit and leaves, similar to savannah chimpanzees and Ardipithecus ramidus (Henry et al., 2012). Despite the presence of climbing adaptations, A. sediba also demonstrates clear evidence for bipedal locomotion. The knee and ankle possess human-like adaptations to bipedalism, demonstrating a valgus angle of the femur and a human-like ankle joint (Zipfel et al., 2011; DeSilva et al., 2013; DeSilva et al., 2018). Evidence for strong dorsal (lordotic) wedging of the two lower lumbar vertebrae suggests the presence of a lordotic (ventrally convex) lower back (Williams et al., 2013; Williams et al., 2018b). However, the initial recovery of just the last two lumbar vertebrae of MH2 limited interpretations of spinal curvature, and a study of the MH2 pelvis reconstruction (Kibii et al., 2011) suggests that A. sediba was characterized by a small lordosis angle estimated from calculated pelvic incidence (Been et al., 2014). A separate pelvis reconstruction of MH2 produces a pelvic incidence angle more in line with other hominins (Tardieu et al., 2017). The presence of a long, mobile lower back and a Homo-like lower thorax morphology indicating the presence of a waist further suggest bipedal adaptations in A. sediba (Schmid et al., 2013; Williams et al., 2013). However, missing and incomplete lumbar vertebrae prevented comparative analysis of overall lower back morphology and allowed only limited interpretations of A. sediba back posture and implications for positional behavior. Here, we report the discovery of portions of four lumbar vertebrae from two ex situ breccia blocks that were excavated from an early 20th century mining road and dump at Malapa. The former mining road is represented by a trackway located in the northern section of the site approximately 2 m north of the main pit that yielded the original A. sediba finds (Dirks et al., 2010; Figure 1). The trackway traverses the site in an east-west direction and was constructed using breccia and soil removed from the main pit by the historic limestone miners. Specimens U.W.88–232, −233,–234, and –281 were recovered in 2015 from the upper section of layer 2 (at a depth of 10 cm) and formed part of the foundation layer of the mining road. The trackway can be distinguished from the surrounding deposits by a section of compacted soil (comprising quartz, cherts, and flowstone) and breccia that extends between layers 1 and 2. Breccia recovered from the trackway, including the block containing U.W.88–232, −233,–234, and –281 similarly presented with quantities of embedded quartz fragments and grains. The breccia block containing specimen U.W.88–280, along with U.W.88–43, –44, and –114 (Williams et al., 2013; Williams et al., 2018b), were recovered from the miner’s dump comprised of excess material (soil and breccia) used for the construction of the miner’s road. The composition of the road matrix and associated breccia, as well as the breccia initially recovered from the mine dump, corresponds to the facies D and E identified in the main pit (Dirks et al., 2010). Facies D includes a fossil-rich breccia deposit that contained the fossil material associated with MH2 (Dirks et al., 2010; Val et al., 2018). Therefore, the geological evidence suggests that the material used for the construction of the miner’s road was sourced on-site, and most probably originated from the northern section of the main pit. Figure 1 Download asset Open asset Malapa site map showing the location of the new discoveries. The new fossils were discovered during excavations of an early 20th century mining road north of the main pit at Malapa. The location of the block containing the new fossils in the mining trackway is shown with a red X. The newly discovered vertebrae (second and third lumbar) are preserved in articulation with each other (Figure 2, Figure 2—figure supplement 1) and refit at multiple contacts with the previously known penultimate (fourth) lumbar vertebra (Figure 3). Together, the new and previously known (Williams et al., 2013; Williams et al., 2018b) vertebral elements form a continuous series from the antepenultimate thoracic vertebra through the fifth sacral element, with only the first lumbar vertebra missing major components of morphology (Figure 3—figure supplement 1). The presence of a nearly complete lower back of MH2 allows us to more comprehensively evaluate the functional morphology and evolution of purported adaptations to bipedalism in A. sediba and test the hypotheses that the following fundamental features are similar to modern humans (Homo sapiens) and distinct from extant great apes: (1) lumbar lordosis, (2) progressive widening of the articular facets and laminae (pyramidal configuration) of the lower back, and (3) overall middle lumbar vertebra shape. Specifically, for these hypotheses, we predict that measurements of combined lumbar wedging (representing degree of lordosis ascertained from available lumbar vertebrae) will fall within the human range (H1), that the configuration of the articular facets and laminae will progressively widen caudally (rather than remaining constant or becoming increasingly narrow) as seen in modern humans (H2), and that the most complete lumbar vertebra of MH2 (U.W.88–233) will fall within the human range of variation in shape analyses (H3). Figure 2 with 1 supplement see all Download asset Open asset New lumbar vertebrae of Malapa Hominin 2 (MH2). Vertebrae in (A) superior, (B) inferior, (C) ventral, (D) dorsal, (E) left lateral, and (F) right lateral views. The partial inferior articular facets of the first lumbar vertebra are embedded in matrix (see Figure 2—figure supplement 1). The second lumbar vertebra (U.W.88–232) is in the superior-most (top) position, the third lumbar vertebra (U.W.88–233) is in the middle, and portions of the upper neural arch of the fourth lumbar vertebra (U.W.88–234) are in the inferior-most (bottom) position. These fossils are curated and available for study at the University of the Witwatersrand. Figure 3 with 1 supplement see all Download asset Open asset The lower back of Malapa Hominin 2 in ventral (left) and dorsal (right) views. New second and third lumbar vertebrae (U.W.88–232, U.W.88–233) are positioned at the top, and U.W.88–234 contributes to the upper portion of the fourth lumbar vertebra (U.W.88–127/153/234). The fifth lumbar vertebra (U.W.88–126/138) sits atop the sacrum (U.W.88–137/125). The lower back elements are preserved together in four blocks, each containing multiple elements held together in matrix and/or in partial articulation: (1) The vertebral body fragment of L1 (U.W.88–280) is preserved within the matrix of a block containing the lower thoracic vertebrae (U.W.88–43/114 and U.W.88–44) (Figure 2—figure supplement 1, Figure 3—figure supplement 1); (2) L1 inferior neural arch (U.W.88–281; concealed in matrix), L2 (U.W.88–232), L3 (U.W.88–233), and upper neural arch of L4 (U.W.88–234); (3) the L4 (U.W.88–127) and L5 (U.W.88–126) vertebral bodies, and partial S1 body (U.W.88–125); (4) most of the sacrum (U.W.88–137), the neural arch of L5 (U.W.88–153), the inferior portion of the neural arch of L4 (U.W.88–138). Results The five new fossils, U.W.88–232, U.W.88–233, U.W.88–234, U.W.88–280, and U.W.88–281, are described below and shown in Figure 4. Measurements are included in Table 1. A depiction of the anatomical features mentioned in the descriptions below and throughout the manuscript is shown in Figure 4—figure supplement 1. Figure 4 with 1 supplement see all Download asset Open asset Surface models of vertebrae from the new lumbar block. (A) U.W.88–232 (L2) and (B) U.W.88–233 (L3) shown in ventral (top left), dorsal (top right), superior (middle left), inferior (middle right), left lateral (bottom left), and right lateral (bottom right) views. (C) U.W.88–234 (L4) in ventral (top left), dorsal (top right), superior (top middle), left lateral (bottom left), right lateral (bottom right), and inferior (bottom middle) views. (D) Left half of U.W.88–233 showing the 48 landmarks used in the three-dimensional geometric morphometric (3D GM) analyses. Table 1 Measurements on lumbar vertebrae in mm for linear data and degrees for angles (measurement definitions are included in the supplementary material). U.W.88–232(L2)U.W.88–233(L3)U.W.88-127/153/234(L4)U.W.88-126/138(L5)1. Body sup. transv. width29.530.131.432.82. Body sup. dorsoven. dia.20.821.422.221.43. Body inf. transv. width29.031.432.428.84. Body inf. dorsoven. dia.21.121.021.219.85. Body ventral height21.021.7522.121.06. Body dorsal height22.522.2521.517.07. Body wedging angle (calculated)4.1°1.3°–1.6°–10.7°8. Vertebral foramen dorsoven. dia.10.58.85–23.09. Vertebral foramen transv. dia.17.617.3–16.310. Sup.-inf. inter-AF height–37.032.631.511. Max. inter-SAF dist.–24.0–28.512. Min. inter-SAF dist.–14.5––13. Max. inter-IAF dist.23.025.0(28.0)*(33.0)14. Min. inter-IAF dist.11.09.511.615.615. SAF sup.-inf. dia.–12.8–13.416. SAF transv. dia.–11.5–10.817. IAF sup.-inf. dia.11.511.514.714.418. IAF transv. dia.8.18.99.211.719. Spinous process angle176°160°163°166°20. Spinous process length27.028.028.023.621. Spinous process terminal trans. width6.97.48.16.8522. Spinous process terminal sup.-inf. height13.811.7512.77.1523. Costal process base sup.-inf. height11.512.2–13.924. Costal process angle78°82°–50°25. Costal process length–31.0––26. SAF orientation (in degrees)–31°33°26°27. Pedicle sup.-inf. height10.910.6–11.228. Pedicle transv. width5.97.19.010.929. Pedicle dorsoven. length5.05.66.57.030. Lamina sup.-inf. height16.115.4–14.031. Lamina transv. width20.022.0–30.5 * Parentheses indicate that the structure is incomplete and its measurement if estimated. Descriptions of new fossil material We determine the seriation of the vertebrae described here based on their direct articulation with one another and refits with previously known vertebrae. Most of the sacrum (U.W.88–137) is preserved in articulation with the neural arch of the last lumbar vertebra (U.W.88–138), which articulates in turn with the inferior portion of the neural arch of the penultimate lumbar vertebra (U.W.88–154). Corresponding vertebral bodies (U.W.88–126 and U.W.88–127, respectively) are preserved together and can be refitted with the neural arches (Williams et al., 2013). The new lumbar vertebrae are preserved in partial articulation, including an upper neural arch that refits in two places with U.W.88–154. Therefore, portions of five vertebrae are preserved, followed by a sacrum and preceded by at least three lower thoracic vertebrae (Williams et al., 2018b). U.W.88–280: This is a partial, superior portion of a vertebral body concealed in the matrix of a previously known block containing lower thoracic vertebrae (U.W.88–114, U.W.88–43, and U.W.88–44, antepenultimate, penultimate, and ultimate thoracic vertebrae, respectively, of MH2) (Williams et al., 2018b). U.W.88–280 was revealed in the segmentation of micro-CT (hereafter, µCT) data. U.W.88–280 represents the right side of an upper vertebral body with preservation approaching the sagittal midline. The preserved portions measure 16.5 mm dorsoventrally and 14.0 mm mediolaterally at their maximum lengths. The lateral portion of the vertebral body is only preserved ~5.0 mm inferiorly from the superior surface, but there is no indication of a costal facet on the preserved portion. We identify this as part (along with U.W.88–281) of the first lumbar vertebra of MH2 based on its position below the vertebral body of what is almost certainly the last thoracic vertebra (U.W.88–44) (Williams et al., 2018b; Figure 2—figure supplement 1). U.W.88–281: This is the partial neural arch of a post-transitional, upper lumbar vertebra concealed in matrix above the subjacent lumbar vertebra (U.W.88–232). It was revealed through the segmentation of µCT data. It consists of the base and caudal portion of the spinous process and parts of the inferior articular processes. The remainder of the vertebra is sheared off and unaccounted for in the block containing the new lumbar vertebrae. U.W.88–281 is fixed in partial articulation with the subjacent second lumbar vertebra (L2), U.W.88–232. Therefore, we identify U.W.88–281 as part of the first lumbar vertebra based on its morphology and position within the block. The left inferior articular facet (IAF) is more complete than the right, with approximately 6.0 mm of its superior-inferior (SI) height preserved, and is complete mediolaterally, measuring ~8.0 mm in width. The minimum distance between the IAF is 12.5 mm, and the maximum preserved distance between them is 21.75 mm. The preserved portion of the spinous process is 12.75 mm in dorsoventral length. U.W.88–232: This vertebra is the L2 and remains in articulation with the third lumbar vertebra (L3), U.W.88–233, held together with matrix. Some portions of U.W.88–232 are covered by adhering matrix or other fossil elements (U.W.88–281 and U.W.88–282, the latter being the sternal end of a clavicle), so µCT data were used to visualize the whole vertebra (Figure 4). U.W.88–232 is mostly complete, missing the cranial portions of its superior articular processes and distal portions of its costal (transverse) processes. It is distorted due to crushing dorsally from the right side and related breakage and slight displacements of the left superior articular process at the pars interarticularis and the right costal process at its base. Although broken at its base and displaced slightly ventrally, the right costal process is more complete than the left side, which is broken and missing ~10.0 mm from its base. Because of crushing, the neural arch is displaced toward the left side, and the vertebral foramen is significantly distorted. A partial mammillary process is on the left superior articular sheared off along with the remainder of the right superior articular process ~8.0 mm from its base. The left side is similar but much of the mammillary process is sheared off in the as the right side, only its base on the lateral of the right superior articular The vertebral body is complete and and the spinous process and inferior articular processes are complete but by measurements of are in Table 1. This is the L3 and the most complete vertebra in the lumbar some aspects of the neural arch are and It is held in matrix and partial articulation with U.W.88–234, the subjacent partial fourth lumbar vertebra to its position between elements U.W.88–232 and and some adhering U.W.88–233 was using µCT data. U.W.88–233 is however, like U.W.88–232, the neural arch is from the dorsal with and the right pars interarticularis and the right costal process at its with additional around the latter the base of the of the right superior articular in a crushing of the vertebral The vertebral spinous and superior and inferior articular processes are complete, as are the and costal processes from the The left costal process is by measurements of are in Table 1. This is a partial neural arch of the previously known penultimate lumbar vertebra (L4) U.W.88–234 refits in two places with the previously known its partial with the vertebral body (U.W.88–127) and its spinous process with the inferior base of the spinous process and inferior articular processes the spinous process and right costal superior articular processes, and partial are and in articulation with to the spinous process and costal so for this µCT data were used to visualize and refit it with a partial L4 missing the left superior articular costal most of the the right lateral of the inferior articular a portion of the the inferior of the costal and a of the lateral measurements are in Table 1. angles and lumbar lordosis of vertebrae contribute to the multiple sagittal of the human with dorsal wedging of lower lumbar vertebrae to a ventrally curvature of the lumbar spine This configuration the upper body the pelvis and allows for the of and in of the human and and et al., et al., 2010; et al., et al., 2017). angles for lumbar vertebrae and combined wedging were calculated for A. sediba and the comparative and are presented in (Figure Figure supplement 1, Figure supplement and Table 2 and Table MH2 the most combined wedging of adult early hominin Although all fossil hominins fall within the of modern only MH2 the of great apes in combined wedging (Figure Table 2 for lumbar wedging angles of the extant comparative Figure with 2 see all Download asset Open asset vertebral body wedging vertebral body wedging angles are from L2 through fossil the last four lumbar vertebrae are included Australopithecus 2, 3). For the extant are shown with Table 2 includes Table 3 fossil hominin and Figure data 1 the data. Figure data 1 wedging angles and combined wedging angles of extant Download Table 3 wedging angles and combined wedging of fossil hominin of lumbar demonstrate that MH2’s vertebrae from ventral to dorsal (lordotic) wedging between the L3 and L4 however, all adult fossil hominins fall within the of modern humans (Figure Figure supplement 1). shown previously (Williams et al., 2013), the last lumbar vertebra of MH2 is dorsally like that of the 2 and the specimen whereas other fossil hominins demonstrate this Although vertebral wedging is characterized by high of variation within in combined wedging (Figure Table the of lumbar wedging angles observed in MH2 from penultimate to ultimate lumbar and its combined wedging fall within the modern human and those of great apes (Figure Figure supplement 1, Figure supplement The hypothesis that A. sediba is human-like in lumbar be of the neural arch The recovery of new lumbar vertebrae of MH2 allows for the and of facet width increase in A. sediba. are characterized by a configuration of the articular facets that they increase in width progressively the lumbar column from cranial to and and an of the last maximum distance to that of lumbar vertebrae three in hominins, in chimpanzees and we show that Australopithecus and and A. sediba fall at the end of the range of modern human variation in this (Figure We that at the end of human variation other if the preserved lumbar vertebra is as an L3 and et al., et al., but the range of human variation and within that of if it is as an L2 et al., Homo and fall well within the range of modern human The presence of a configuration of the lumbar articular facets is in our hypothesis that A. sediba was to a human-like configuration of the neural Figure Download asset Open asset configuration of articular facet in The facets of the last and those of lumbar vertebrae three elements in the column in chimpanzees and with four lumbar in are included as the and respectively, in a lumbar facet These are on the left in red in both a human (top) and a The the range of variation observed in the modern human great apes are significantly from modern humans The data for facet can be in Figure data 1. Figure data 1 facet of fossil hominins and extant Download lumbar vertebra (L3) comparative morphology The new middle lumbar U.W.88–233, is complete, and the neural arch is ventrally into the vertebral foramen it can be reconstructed from µCT data (see