Hominin Research Articles

Frontal bone virtual reconstruction and geometric morphometric analysis of the mid-Pleistocene hominin KNM-OG 45500 (Olorgesailie, Kenya).

KNM-OG 45500 is a hominin fossil composed of parts of a frontal bone, left temporal bone, and cranial vault pieces. Since its discovery along the Olorgesailie Formation (Kenya) in 2003, it has been associated with the Homo erectus hypodigm. The specimen, derived from a geological context dated to ca. 900 Ka BP, has been described as a very small individual of probable female sex. However, despite its status as an important hominin specimen, it has not been used in a quantitative comparative framework because of its fragmentary condition. Here, we undertake a virtual reconstruction of the better-preserved fragment, the frontal bone. We additionally apply geometric morphometric analyses, using a geographically diverse fossil and modern human sample, in order to investigate the morphological affinities of KNM-OG 45500. Our results show that the frontal shape of KNM-OG 45500 exhibits similarities with Early Pleistocene fossils from Eurasia and Africa that are assigned to H. erectus sensu lato (s.l.). Its size, on the other hand, is notably smaller than most other Homo erectus fossils and modern humans and similar to the specimens from Dmanisi (Georgia) and to Homo naledi. Taken together, our analyses of the frontal bone suggest a taxonomic attribution of KNM-OG 45500 to H. erectus s.l. and extend even further the range of size variability associated with this taxon around 900 Ka BP.

DNA barcoding of primates and the selection of molecular markers using African Great Apes as a model.

Ambiguities within species description and identification may compromise research validity. Species identification has typically been based upon morphological characteristics, yet recent technological advances have led to identifications achieved via DNA approaches, including DNA barcoding. DNA barcoding studies typically use cytochrome c oxidase subunit I (COI) as the proposed universal molecular marker for animals. Here, we test 12 mitochondrial protein coding genes for the presence of a clear barcoding gap allowing us to unequivocally define species. Using the African Great Apes as our model group, we assess this at the species (Pan troglodytes), genus (Pan) and family (Hominidae) level. Based on 279 complete mitochondrial genomes, sequences were partitioned by gene for analysis and pairwise distances were calculated. No barcoding gap was observed at the within species level, i.e., the four recognised chimpanzee taxa were not distinguishable through DNA barcoding. However, NADH dehydrogenase subunit 5 (ND5) and cytochrome c oxidase subunit II (COII) produce the largest barcoding gaps at the genus (ND5 2%, COII 0.5%) and family (ND5 1.5%, COII 0.5%) level. Rather than focusing on COI, our analysis suggests that these two genes may be more, or at least as, appropriate markers in primate species delineation, with uses in the identification of extinct and extant species. Further use may be beneficial to taxonomists, providing additional evidence and new insights for these morphologically similar species.

Mapping suitable great ape habitat in and around the Lobéké National Park, South-East Cameroon.

As a result of extensive data collection efforts over the last 20–30 years, there is quite a good understanding of the large‐scale geographic distribution and range limits of African great apes. However, as human activities increasingly fragment great ape spatial distribution, a better understanding of what constitutes suitable great ape habitat is needed to inform conservation and resource extraction management. Chimpanzees (Pan troglodytes troglodytes) and gorillas (Gorilla gorilla gorilla) inhabit the Lobéké National Park and its surrounding forest management units (FMUs) in South‐East Cameroon. Both park and neighboring forestry concessions require reliable evidence on key factors driving great ape distribution for their management plans, yet this information is largely missing and incomplete. This study aimed at mapping great ape habitat suitability in the area and at identifying the most influential predictors among three predictor categories, including landscape predictors (dense forest, swampy forest, distance to water bodies, and topography), human disturbance predictors (hunting, deforestation, distance to roads, and population density), and bioclimatic predictor (annual precipitation). We found that about 63% of highly to moderately suitable chimpanzee habitat occurred within the Lobéké National Park, while only 8.4% of similar habitat conditions occurred within FMUs. For gorillas, highly and moderately suitable habitats occurred within the Lobéké National Park and its surrounding FMUs (82.6% and 65.5%, respectively). Key determinants of suitable chimpanzee habitat were hunting pressure and dense forest, with species occurrence probability optimal at relatively lower hunting rates and at relatively high‐dense forest areas. Key determinants of suitable gorilla habitat were hunting pressure, dense forests, swampy forests, and slope, with species occurrence probability optimal at relatively high‐dense and swampy forest areas and at areas with mild slopes. Our findings show differential response of the two ape species to forestry activities in the study area, thus aligning with previous studies.

The endangered African Great Ape: Pesticide residues in soil and plants consumed by Mountain Gorillas (Gorilla beringei) in Bwindi Impenetrable National Park, East Africa

Bwindi Impenetrable National Park situated southwest of Uganda is a biodiversity hotspot that is home to about half of the world's endangered mountain gorilla (Gorilla beringei). Given its ecological significance and mounting pressures from agricultural activities such as tea growing, continuous monitoring of the levels of chemical toxins like pesticides in the park and surrounding areas is needed for effective conservation strategies. Furthermore, persistent organochlorine pesticides (OCPs) like DDT were used in agricultural gardens and indoor spraying in Kanungu district between the 1950s and 80s. The focus of this study was to explore the possible exposure of mountain gorillas to OCPs and cypermethrin used by the farmers in the areas near the park. Data from our interviews revealed that glyphosate is the most widely used pesticide by the farmers in areas surrounding the park, followed by cypermethrin, and mancozeb. Samples of leaves from plants consumed by mountain gorillas along the forest edges of the park and surficial soils (15–20 cm depths) were collected from three sites (Ruhija, Nkuringo and Buhoma) and analysed for the presence of cypermethrin and OCPs residues. Concentrations of total (∑) DDTs and ∑endosulfans were up to 0.34 and 9.89 mg/kg dry weight (d.w), respectively in soil samples. Concentrations of ∑DDTs and ∑endosulfans in samples of leaves ranged from 0.67 to 1.38 mg/kg d.w (mean = 1.07 mg/kg d.w) and 0.9 to 2.71 mg/kg d.w (mean = 1.68 mg/kg d.w), respectively. Mean concentration of ∑DDTs in leaves exceeded the European pharmacopeia and United States pharmacopeia recommended maximum residue limit values for DDTs in medicinal plants (1.0 mg/kg). In addition, calculated hazard indices for silverbacks (36.35), females (57.54) and juveniles (77.04) suggested potential health risks to the mountain gorillas. o,p′-DDT/p,p′-DDT ratios (0.5–0.63) in samples of leaves confirmed recent input of dicofol-DDT type in Bwindi rainforest.

Assessing conservation attitudes and behaviors of Congolese children neighboring the world's first bonobo (Pan paniscus) release site.

Poaching and habitat destruction in the Congo Basin threaten African great apes including the bonobo (Pan paniscus), chimpanzees (Pan troglodytes), and gorillas (Gorilla spp.) with extinction. One way to combat extinction is to reintroduce rescued and rehabilitated apes and repopulate native habitats. Reintroduction programs are only successful if they are supported by local populations. Ekolo ya Bonobo, located in Equateur province of the Democratic Republic of Congo (DRC), is the world's only reintroduction site for rehabilitated bonobos. Here we assess whether children, of the Ilonga-Pôo, living adjacent to Ekolo ya Bonobo demonstrate more pro-ape conservation attitudes than children living in, Kinshasa, the capital city. We examined children's attitudes toward great apes because children are typically the focus of conservation education programs. We used the Great Ape Attitude Questionnaire to test the Contact Hypothesis, which posits that proximity to great ape habitat influences pro-conservation attitudes toward great apes. Ilonga-Pôo children who live in closer contact with wild bonobos felt greater responsibility to protect great apes compared to those in Kinshasa who live outside the natural habitat of great apes. These results suggest that among participants in the DRC, spatial proximity to a species fosters a greater sense of responsibility to protect and conserve. These results have implications for the successful implementation of great ape reintroduction programs in the Congo Basin. The data analyzed in this study were collected in 2010 and therefore provide a baseline for longitudinal study of this reintroduction site.

Human engagement and great ape conservation in Africa.

Despite large investments of funding into great ape conservation in Africa, wild populations of gorillas (Gorillassp), chimpanzees (Pan troglodytesssp) and bonobos (Pan paniscus) continue to decline. Causes for this decline fall into three broad categories: habitat loss, illegal hunting, and disease. Contributing factors to all of these causes are linked to pressure from the expanding human population competing for forest resources. We have moved beyond the time of debating the pros and cons of including human engagement activities in conservation. If humans are part of the problem, they must also be part of the solution. To move our understanding of which human engagement activities are effective, what methodologies are being used and best practices for setting up a successful framework, we interviewed practitioners representing 53 projects working in great ape habitat in Africa. The interviewees represented almost 900 years of experience with African great ape conservation. We found that all practitioners agreed that for conservation to succeed, projects must engage with humans utilizing resources from great ape habitats. However, evaluation of such work was elusive. Projects that employed at least one person designated as an educator were more likely to have structured programs, regular engagement activities, and to evaluate their work. To date, little information on the success or failure of the activities has been published, thus perpetuating the problem of relying on personal experience rather than evidence when developing new engagement programs. Additionally, linking human engagement activities to biological impact remains a challenge. The results presented in this paper demonstrate the importance placed on human engagement activities to effectively conserve great apes in Africa while at the same time identifies gaps in our understanding on the link between such activities and project success.

Ape Origins of Human Malaria.

African apes harbor at least twelve Plasmodium species, some of which have been a source of human infection. It is now well established that Plasmodium falciparum emerged following the transmission of a gorilla parasite, perhaps within the last 10,000 years, while Plasmodium vivax emerged earlier from a parasite lineage that infected humans and apes in Africa before the Duffy-negative mutation eliminated the parasite from humans there. Compared to their ape relatives, both human parasites have greatly reduced genetic diversity and an excess of nonsynonymous mutations, consistent with severe genetic bottlenecks followed by rapid population expansion. A putative new Plasmodium species widespread in chimpanzees, gorillas, and bonobos places the origin of Plasmodium malariae in Africa. Here, we review what is known about the origins and evolutionary history of all human-infective Plasmodium species, the time and circumstances of their emergence, and the diversity, host specificity, and zoonotic potential of their ape counterparts.

Isotopic evidence for the timing of the dietary shift toward C4 foods in eastern African Paranthropus

New approaches to the study of early hominin diets have refreshed interest in how and when our diets diverged from those of other African apes. A trend toward significant consumption of C4 foods in hominins after this divergence has emerged as a landmark event in human evolution, with direct evidence provided by stable carbon isotope studies. In this study, we report on detailed carbon isotopic evidence from the hominin fossil record of the Shungura and Usno Formations, Lower Omo Valley, Ethiopia, which elucidates the patterns of C4 dietary utilization in the robust hominin Paranthropus The results show that the most important shift toward C4 foods occurred at ∼2.37 Ma, within the temporal range of the earliest known member of the genus, Paranthropus aethiopicus, and that this shift was not unique to Paranthropus but occurred in all hominins from this fossil sequence. This uptake of C4 foods by hominins occurred during a period marked by an overall trend toward increased C4 grazing by cooccurring mammalian taxa from the same sequence. However, the timing and geographic patterns of hominin diets in this region differ from those observed elsewhere in the same basin, where environmental controls on the underlying availability of various food sources were likely quite different. These results highlight the complexities of dietary responses by hominins to changes in the availability of food resources.

Insertion sites in manual proximal phalanges of African apes and modern humans.

The primary aim of this study was to describe the insertion sites of the ligaments holding the flexor digitorum profundus and superficialis muscles (flexor ridges) in proximal phalanges 2-5 of African apes and modern humans. To interpret differences in flexor ridge size based on general behavioral differences among taxa. We analyzed 3D models of manual proximal phalanges 2-5 from 29 gorillas (Gorilla beringei and Gorilla gorilla), 30 chimpanzees (Pan troglodytes) and 36 recent modern humans. Flexor ridges (mm2) were compared within and across genera. Gorillas and chimpanzees had larger flexor ridges for phalanges 2-4 than humans and this difference subsists when controlling for body size. Each genus had a unique insertion size pattern across the digits, with the most heterogeneous pattern found in chimpanzees, followed by humans, and lastly gorillas. These patterns corresponded strongly to the differences in the size of the phalanges within each genus, except for phalanx 5 in humans, which had a larger flexor ridge than expected. When comparing these genera, the flexor ridges signal differences between taxa that use their hands for manipulation and locomotion (gorillas and chimpanzees) and taxa that use them exclusively for manipulation (humans). This functional signal was also apparent in the PP5 of humans, whose larger FR may be indicating the high recruitment of this digit during forceful precision grip characteristic of humans.

An evolutionary driver of interspersed segmental duplications in primates

BackgroundThe complex interspersed pattern of segmental duplications in humans is responsible for rearrangements associated with neurodevelopmental disease, including the emergence of novel genes important in human brain evolution. We investigate the evolution of LCR16a, a putative driver of this phenomenon that encodes one of the most rapidly evolving human–ape gene families, nuclear pore interacting protein (NPIP).ResultsComparative analysis shows that LCR16a has independently expanded in five primate lineages over the last 35 million years of primate evolution. The expansions are associated with independent lineage-specific segmental duplications flanking LCR16a leading to the emergence of large interspersed duplication blocks at non-orthologous chromosomal locations in each primate lineage. The intron-exon structure of the NPIP gene family has changed dramatically throughout primate evolution with different branches showing characteristic gene models yet maintaining an open reading frame. In the African ape lineage, we detect signatures of positive selection that occurred after a transition to more ubiquitous expression among great ape tissues when compared to Old World and New World monkeys. Mouse transgenic experiments from baboon and human genomic loci confirm these expression differences and suggest that the broader ape expression pattern arose due to mutational changes that emerged in cis.ConclusionsLCR16a promotes serial interspersed duplications and creates hotspots of genomic instability that appear to be an ancient property of primate genomes. Dramatic changes to NPIP gene structure and altered tissue expression preceded major bouts of positive selection in the African ape lineage, suggestive of a gene undergoing strong adaptive evolution.

Characterisation of an exo-(α-1,3)-3,6-anhydro-d-galactosidase produced by the marine bacterium Zobellia galactanivorans DsijT: Insight into enzyme preference for natural carrageenan oligosaccharides and kinetic characterisation on a novel chromogenic substrate

Flavobacteriia are important degraders in the marine carbon cycle, due to their ability to efficiently degrade complex algal polysaccharides. A novel exo-(α-1,3)-3,6-anhydro-D-galactosidase activity was recently discovered from a marine Flavobacteriia (Zobellia galactanivorans DsijT) on red algal carrageenan oligosaccharides. The enzyme activity is encoded by a gene found in the first described carrageenan-specific polysaccharide utilization locus (CarPUL) that codes for a family 129 glycoside hydrolase (GH129). The GH129 family is a CAZy family that is strictly partitioned into two niche-based clades: clade 1 contains human host bacterial enzymes and clade 2 contains marine bacterial enzymes. Clade 2 includes the GH129 exo-(α-1,3)-3,6-anhydro-D-galactosidase from Z. galactanivorans (ZgGH129). Despite the discovery of the unique activity for ZgGH129, finer details on the natural substrate specificity for this enzyme are lacking. Examination of enzyme activity on natural carrageenan oligomers using mass spectrometry demonstrated that ZgGH129 hydrolyses terminal 3,6-anhydro-D-galactose from unsulfated non-reducing end neo-β-carrabiose motifs. Due to the lack of chromogenic substrates to examine exo-(α-1,3)-3,6-anhydro-D-galactosidase activity, a novel substrate was synthesised to facilitate the first kinetic characterisation of an exo-(α-1,3)-3,6-anhydro-D-galactosidase, allowing determination of pH and temperature optimums and Michaelis-Menten steady state kinetic data.

Revised estimates of Taung’s brain size growth

Cranial capacity, a proxy for the volume of the brain and associated cranial contents, is an important yardstick used to compare early hominin species because increasing brain size is a key characteristic of our lineage. In 1925, Raymond Dart claimed that a natural endocast found at the Buxton Limeworks near Taung, South Africa (which he named Australopithecus africanus), showed signs of neural reorganisation, but its juvenile status complicated comparison to other hominoid species. In an attempt to put its brain size and reorganisation into a comparative context, subsequent researchers have tried to estimate Taung’s adult cranial capacity by comparison to coarse-grained hominoid growth data. In this study, we simulated brain growth in A. africanus using asymptotic growth models in known-age mountain gorillas, chimpanzees and modern humans, and show that, at just under 4 years old, Taung’s brain had already finished or nearly finished growing according to hominoid developmental schedules. Percentage-growth remaining estimates are lower here than in previous studies using cross-sectional ontogenetic samples of unknown chronological age. Our new adult estimates (between 404 cm3 and 430 cm3 overall and 405–406 cm3 for chimpanzee models) are smaller than previous estimates with a ‘starting’ cranial capacity of 404 cm3, supporting the hypothesis that Taung’s adult brain size would have fallen toward the lower end of the A. africanus range of variation and strengthening the case that Taung was female.
 Significance:
 
 This is one of several recent studies to show that brain growth is completed in African apes and humans earlier than previously appreciated.
 New adult cranial capacity estimates for Taung are lower than previous estimates, supporting the hypothesis that Taung was female.
 Cessation of brain growth in hominoids at earlier ages than previously reported suggests that adult cranial capacities for hominin juvenile specimens have been overestimated.
 
 Open data set:
 http://dx.doi.org/10.17632/wyfvwd4s22

The biomechanics of knuckle-walking: 3-D kinematics of the chimpanzee and macaque wrist, hand and fingers.

The origin and evolution of knuckle-walking has long been a key focus in understanding African ape, including human, origins. Yet, despite numerous studies documenting morphological characteristics potentially associated with knuckle-walking, little quantitative three-dimensional (3-D) data exist of forelimb motion during knuckle-walking. Nor do any comparative 3-D data exist for hand postures used during quadrupedalism in monkeys. This lack of data has limited the testability of proposed adaptations for knuckle-walking in African apes. This study presents the first 3-D kinematic data of the wrist, hand and metacarpophalangeal joints during knuckle-walking in chimpanzees and in macaques using digitigrade and palmigrade hand postures. These results clarify the unique characteristics of, and commonalities between, knuckle-walking and digitigrady/palmigrady in multiple planes of motion. Notably, chimpanzees utilized more wrist ulnar deviation than any macaque hand posture. Maximum extension of the chimpanzee wrist was slight (5-20deg) and generally overlapped with macaque digitigrady. Metacarpophalangeal joint motion displayed distinct differences between digits in both species, likely related to the timing of force application. These data also reveal that maximum metacarpophalangeal extension angles during knuckle-walking (26-59deg) were generally higher than previously considered. In macaques, maximum metacarpophalangeal extension during digitigrady and palmigrady overlapped for most digits, highlighting additional complexity in the interpretation of skeletal features that may be related to limiting metacarpophalangeal motion. Most importantly, however, these new 3-D data serve as a fundamental dataset with which evaluation of proposed musculoskeletal adaptations for knuckle-walking can be tested.

Mechanics of heel-strike plantigrady in African apes

The initiation of a walking step with a heel strike is a defining characteristic of humans and great apes but is rarely found in other mammals. Despite the considerable importance of heel strike to an understanding of human locomotor evolution, no one has explicitly tested the fundamental mechanical question of why great apes use a heel strike. In this report, we test two hypotheses (1) that heel strike is a function of hip protraction and/or knee extension and (2) that short-legged apes with a midfoot that dorsiflexes at heel lift and long digits for whom digitigrady is not an option use heel-strike plantigrady. This strategy increases hip translation while potentially moderating the cost of redirecting the center of mass (‘collisional costs’) during stance via rollover along the full foot from the heel to toes. We quantified hind limb kinematics and relative hip translation in ten species of primates, including lemurs, terrestrial and arboreal monkeys, chimpanzees, and gorillas. Chimpanzees and gorillas walked with relatively extended knees but only with moderately protracted hips or hind limbs, partially rejecting the first hypothesis. Nonetheless, chimpanzees attained relative hip translations comparable with those of digitigrade primates. Heel-strike plantigrady may be a natural result of a need for increased hip translations when forelimbs are relatively long and digitigrady is morphologically restricted. In addition, foot rollover from the heel to toe in large, short-legged apes may reduce energetic costs of redirecting the center of mass at the step-to-step transition as it appears to do in humans. Heel strike appears to have been an important mechanism for increasing hip translation, and possibly reducing energetic costs, in early hominins and was fundamental to the evolution of the modern human foot and human bipedalism.

On the Earliest Representations of Chimpanzees (Pan troglodytes): Were African Apes Traded to Bronze Age Elam?

There is no literature referring to the ancient iconographic depiction of apes in the eastern circum-Mediterranean region and the Near East. Written reports such as the Old Testament mention apes, but this may be a reference to monkeys, while Hanno the Carthaginian Navigator referred to chimpanzees in the 5th–6th century BC. Here we describe two marble figures, belonging to a private gallery, allegedly from Middle Bronze Age Elam. They represent a “seated monkey” and a “crouched monkey.” Detailed observation and analysis of the morphological characters of both figures show that they almost certainly represent chimpanzees. If the dates and provenance of this material are correct, they are the earliest known representations of African apes. It would follow that chimpanzees were traded, as living animals, as artifacts or imageries, along an extended distance from the Central African forests to the east coast of Africa towards Elam, by the 2nd millennium BC. Alternatively, the figures may date from the Roman period, in which case the circulation of these apes or ape representations occurred centuries later, possibly from other parts of Africa. As these figures are relevant for the archaeoprimatological record, their archeological contexts require further detailed studies. Nevertheless, whether the figures are of Elamite or Roman origin, they are the earliest known representations of chimpanzees.

Occurrence and transmission of flu-like illness among neighboring bonobo groups at Wamba

Infectious diseases constitute one of the major threats to African great apes. Bonobos (Pan paniscus) may be particularly vulnerable to the transmission of infectious diseases because of their cohesive grouping and frequent social and sexual interactions between groups. Here we report two cases of a flu-like illness and possible transmission of the illness among neighboring wild bonobo groups at Wamba, DR Congo. The first flu-like outbreak started in the PE group on July 28, 2013, 2days after they had encounters with the BI and PW groups. All PE members, except for one infant, subsequently developed flu-like symptoms, including coughing and running nose. The second flu-like outbreak occurred in the E1 group on October 14, 2013, after E1 had encountered the PE group and the two groups stayed together from October 7 to 11. Eleven out of the 15 observed party members developed symptoms over the next 4days. The pathogens underlying the two outbreaks may have been related as two temporary immigrant females, who had previously shown symptoms while in the PE group, stayed briefly in the E1 group during the second outbreak, but did not show any symptoms.

The <italic>Australopithecus</italic> Taun child skull: A fossil that changed human evolution history

The <italic>Australopithecus</italic> Taun child skull: A fossil that changed human evolution history

Yaws Disease Caused by Treponema pallidum subspecies pertenue in Wild Chimpanzee, Guinea, 2019.

Yaws-like lesions are widely reported in wild African great apes, yet the causative agent has not been confirmed in affected animals. We describe yaws-like lesions in a wild chimpanzee in Guinea for which we demonstrate infection with Treponema pallidum subsp. pertenue. Assessing the conservation implications of this pathogen requires further research.

Reassessment of the TM 1517 odonto-postcranial assemblage from Kromdraai B, South Africa, and the maturational pattern of Paranthropus robustus.

The Pleistocene taxon Paranthropus robustus was established in 1938 following the discovery at Kromdraai B, South Africa, of the partial cranium TM 1517a and associated mandible TM 1517b. Shortly thereafter, a distal humerus (TM 1517g), a proximal ulna (TM 1517e), and a distal hallucial phalanx (TM 1517k) were collected nearby at the site, and were considered to be associated with the holotype. TM 1517a-b represents an immature individual; however, no analysis of the potentially associated postcranial elements has investigated the presence of any endostructural remnant of recent epiphyseal closure. This study aims at tentatively detecting such traces in the three postcranial specimens from Kromdraai B. By using μXCT techniques, we assessed the developmental stage of the TM 1517b's C-M3 roots and investigated the inner structure of TM 1517g, TM 1517e, and TM 1517k. The M2 shows incompletely closed root apices and the M3 a half-completed root formation stage. The distal humerus was likely completely fused, while the proximal ulna and the distal hallucial phalanx preserve endosteal traces of the diaphyseo-epiphyseal fusion process. In the hominin fossil record, there are few unambiguously associated craniodental and postcranial remains sampling immature individuals, an essential condition for assessing the taxon-specific maturational patterns. Our findings corroborate the original association of the craniodental and postcranial remains representing the P. robustus type specimen. As with other Plio-Pleistocene hominins, the odonto-postcranial maturational pattern of TM 1517 more closely fits an African great ape rather than the extant human pattern.

Great apes and humans evolved from a long-backed ancestor

There is current debate whether the Homo/Pan last common ancestor (LCA) had a short, stiff lumbar column like great apes or a longer, flexible column observed in generalized Miocene hominoids. Beyond having only four segments, three additional features contribute to lumbar stiffening: the position of the transitional vertebra (TV), orientation of the lumbar spinous processes, and entrapment of lumbar vertebrae between the iliac blades. For great apes, these features would be homologous if inherited from a short-backed LCA but likely functionally convergent through dissimilar phenotypes if evolved from a long-backed LCA. We quantitatively and qualitatively analyzed human, ape, and monkey thoracic and lumbar vertebrae using 3D surface scanning and osteological measurements to compare spinous process morphology and sacral depth. We also used a large sample of hominoid vertebral counts to assess variation in the position of the TV and lumbosacral boundary. All extant hominoids modally place the TV at the ultimate thoracic. However, humans and orangutans place the TV at the 19th postcranial vertebral segment, whereas other apes place the TV at the 20th. Furthermore, chimpanzees, gorillas, and orangutans each have distinct patterns of spinous process angulation and morphology associated with lumbar stiffening, while human spinous process morphology is similar to that of longer backed gibbons, monkeys, and Miocene hominoids Morotopithecus and Pierolapithecus. Finally, chimpanzees are unique compared with other hominoids with a greater sacral depth facilitating lumbar entrapment, and there are differences among African apes with respect to the mechanisms governing variation in the lumbosacral boundary. These differences suggest that lumbar stiffening is convergent among great apes and that human bipedalism evolved from a more generalized long-backed ancestor. Such a model is more consistent with evidence of TV placement in Australopithecus.