Scott A. Williams | New York University (original) (raw)
Papers by Scott A. Williams
ABSTRACT shape of the innominates. Here a series of VOIs proceeding from the level of the posteri... more ABSTRACT shape of the innominates. Here a series of VOIs proceeding from the level of the posterior inferior iliac spine (PIIS) toward the acetabulum were used. They were scaled by the geometric means of measurements of each ilium, to facilitate comparison of homologous regions. Bone volume fell in both ilia as the scans proceeded inferiorly, likely due to the relief of this region from the actions of the gluteal muscles. No differences in SVD were found. Bone volume was higher in the chimpanzee than in the orangutan, consistent with the prediction. This study was funded by a Bigel Endowment Grant, a Zelnick Research Award, and the Center for Human Evolutionary Studies at Rutgers University. An examination of pubertal development in human skeletal remains from medieval England. FIONA C. SHAPLAND. Archaeology, University of Reading. In societies where date of birth was rarely formally recorded, the perception of individuals as children or adults was inevitably dependent on the physical process of puberty, but this subject has to date received little attention in bioarchaeology. Based on modern data, it is possible to identify specific dental and skeletal maturation events that closely correspond with the external changes of puberty: the development of the mandibular canine, hamate, hand phalanges, iliac crest, cervical vertebrae and distal radius. This paper presents the results of an application of these methods to two large skeletal collections from Medieval England: St Peter's Church, Barton-upon-Humber and St Mary Spital, London. Examining pubertal development alongside chronological age in these two very different populations provides an insight into the possible environmental and social factors that affected this maturation process in the past. In both populations, the onset of puberty appears to be occurring at a similar age to 20 th century adolescents, but the later stages of puberty were significantly delayed, in some cases by four or five years in comparison to modern standards. Age at menarche also seems to have been being affected, particularly in the urban group. This analysis suggests that the timing and progress of puberty in medieval England was being influenced by environmental factors including nutrition, exposure to infection and physical labour. Funded by the Leverhulme Trust as part of the three year project: 'Adolescence, health and migration in Medieval England'. The evolution of brain size and longevity in mammals.
ABSTRACT maturation of Neandertals, a large sample (n = 42) of fossil infants, juveniles, subadul... more ABSTRACT maturation of Neandertals, a large sample (n = 42) of fossil infants, juveniles, subadults and adults is compared to an ontogenetic sequence for modern humans (n = 294) using an interpolation of growth trajectories generated from piecewise regression. Modeled growth trajectories and shape changes in the calvarium, face and mandible are subsequently explored in a multivariate framework. The two species of Pan (P. troglodytes, n = 156 and P. paniscus, n = 151) provide a benchmark upon which to evaluate the differences between Neandertals and modern humans. Craniofacial changes during the postnatal maturation of Neandertals and modern humans are complex and no single description can adequately characterize differences in growth rates and the duration of the growth of traits. Although Neandertals are larger at birth for many craniofacial features, modeled growth curves indicate Neandertal life cycle maturation was accelerated only for some mandibular and palatal dimensions. For dimensions of the calotte, such as upper cranial height and cranial length, it is modern humans who exhibit a more rapid growth rate but with a shorter duration of growth compared to Neandertals. To the extent that life cycle age can be reconstructed from dental eruption, modeled growth curves for Neandertals imply that they achieved craniofacial maturation at ages comparable to those characterizing modern humans suggesting fundamental patterns of human life history arose in an ancestor of archaic and modern Homo., 3 Institute for the Study of the Ancient World, New York University, 4 National Museum of Natural History, Smithsonian Institution. Stable isotope analysis has been used to reconstruct infant feeding practices, and to evaluate developmental metabolic conditions. Several studies have documented isotopic changes during growth of tissues with relatively fast accretion rates, however intra-individual isotopic variation within these tissues has not been fully addressed. To evaluate intra-individual variation, 40 bone samples were collected from a well-preserved fetal individual (37 weeks gestation) from the Kellis 2 Cemetery (c. 100-360 AD), Dakhleh Oasis, Egypt. Samples were selected based on known time-sensitive fetal development of primary and secondary ossification centers. Results from analyses of bone collagen (n = 22) indicate intra-individual variation greater than 1.2‰ for δ 13
International Journal of Primatology, 2010
eLife, May 9, 2017
The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Cham... more The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial ...
PaleoAnthropology, 2018
Australopithecus sediba is known from two partial skeletons, Malapa Hominins 1 and 2 (MH1 and MH2... more Australopithecus sediba is known from two partial skeletons, Malapa Hominins 1 and 2 (MH1 and MH2), a juvenile
male and an adult female, respectively. Forty-eight elements of the axial skeleton, including vertebrae, ribs, a
sternum, and a sacrum, are known from MH1 and MH2. Here, we describe these ~2.0 Ma fossils and provide raw
data and plots of standardized measurements. We revisit the serial positions of the previously described vertebrae
and ribs proposed in their initial announcements and provide revised identifications. Additionally, we include
in our descriptions and analyses new axial material. Finally, we also test the hypothesis that multiple species are
represented in the MH1 and MH2 material and specifically that MH1’s lumbar vertebrae belong to a member of
the genus Homo, whereas those of MH2 belong to Australopithecus. We do not find support for this hypothesis, and
instead attribute differences between MH1 and MH2 to their age difference and incomplete growth of the vertebral
body in juvenile MH1.
American journal of physical anthropology, Jan 27, 2018
Lower thoracic widths and curvatures track upper pelvic widths and iliac blades curvatures in hom... more Lower thoracic widths and curvatures track upper pelvic widths and iliac blades curvatures in hominins and other primates (torso integration hypothesis). However, recent studies suggest that sexual dimorphism could challenge this assumption in Homo sapiens. We test the torso integration hypothesis in two modern human populations, both considering and excluding the effect of sexual dimorphism. We further assess covariation patterns between different thoracic and pelvic levels, and we explore the allometric effects on torso shape variation. A sex-balanced sample of 50 anatomically connected torsos (25 Mediterraneans, 25 Sub-Saharan Africans) was segmented from computed tomography scans. We compared the maximum medio-lateral width at seventh-ninth rib levels with pelvic bi-iliac breadth in males and females within both populations. We measured 1,030 (semi)landmarks on 3D torso models, and torso shape variation, mean size and shape comparisons, thoraco-pelvic covariation and allometric ...
The social brain hypothesis posits that social complexity is the primary driver of primate cognit... more The social brain hypothesis posits that social complexity is the primary driver of primate cognitive complexity, and that social pressures ultimately led to the evolution of the large human brain. Although this idea has been supported by studies indicating positive relationships between relative brain and/or neocortex size and group size, reported effects of different social and mating systems are highly conflicting. Here, we use a much larger sample of primates, more recent phylogenies, and updated statistical techniques, to show that brain size is predicted by diet, rather than multiple measures of sociality, after controlling for body size and phylogeny. Specifically, frugivores exhibit larger brains than folivores. Our results call into question the current emphasis on social rather than ecological explanations for the evolution of large brains in primates and evoke a range of ecological and developmental hypotheses centred on frugivory, including spatial information storage, ex...
American Journal of Physical Anthropology, 2018
Differences in thorax shape between humans and the great apes are well documented, with the narro... more Differences in thorax shape between humans and the great apes are well documented, with the narrow upper thorax and wide lower thorax of apes contrasting with the opposite pattern in fossil Homo and extant humans. Interestingly, current reconstructions of thoraces in small-bodied hominins, such as the Australopithecus afarensis A.L. 288-1, may feature a smaller, more apelike pulmonary thorax (upper thorax), while its larger-bodied conspecific KSD-VP-1/1 is suggested to be more human with a relatively expanded upper thorax. Toward understanding this dichotomy, we examine the relationship between body size and thorax shape, and model trajectories of the upper limb relative to differently shaped thoraces. We show that variation in thorax shapes facilitate or constrain certain locomotor patterns, as a small upper with an expanded lower thorax facilitates knuckle-walking, orienting the upper limb close to the sagittal midline and center of gravity during locomotion, and confers efficient scapular movement around the ribcage. Conversely, an expanded upper and small lower thorax better facilitates bipedality, facilitating more efficient arm swing and energy return from upper limb momentum, while lower thoracic expansion constrains arm swing in bipedal locomotion. Since lung volume and body mass scale isometrically, increases in lung capacity (and concomitant expansion of the thorax) would be best apportioned to the lower thorax in knuckle-walkers. By contrast, increases in lung capacity and thorax expansion in bipeds are best apportioned superiorly. Thus, locomotor constraints, in concert with the isometric relationship between body size and lung size, may explain thoracic shape variation in early hominins.
American Journal of Physical Anthropology, 2012
Journal of Human Evolution, 2021
Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft repres... more Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft represents pathological traumatic bowing from a childhood fall. Shape analysis in a sample of apes, hominins and modern humans, including clinical humans with this pathology rejects the traumatic bowing hypothesis. Instead, the ‘Little Foot’ ulna reflects a natural degree of curvature observed in apes and several early hominins.
Journal of Human Evolution, 2021
Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft repres... more Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft represents pathological traumatic bowing from a childhood fall. Here we perform Elliptical Fourier shape analysis in a sample of apes, hominins and modern humans, including clinical humans with this pathology, and we reject the traumatic bowing hypothesis. Instead, the ‘Little Foot’ ulna reflects a natural degree of curvature observed in apes and several early hominins.
Nature, 2020
Danuvius guggenmosi is a new species of Miocene hominoid from the 11.62 Ma site of Hammerschmiede... more Danuvius guggenmosi is a new species of Miocene hominoid from the 11.62 Ma site of Hammerschmiede. Based on interpretations of vertebrae and limbs, Böhme and colleagues infer that Danuvius exhibited “joint positions and loading patterns of both hominin bipedalism...and extant great ape suspension” (p.2). While we agree that Danuvius was suspensory, we find the functional interpretation of bipedality to be unfounded on morphological grounds. We therefore call into question the evolutionary scenario for the origin of hominin bipedalism proposed by Böhme and colleagues.
American journal of physical anthropology, 2016
Ever since Tyson (1699), anatomists have noted and compared differences in the regional numbers o... more Ever since Tyson (1699), anatomists have noted and compared differences in the regional numbers of vertebrae among humans and other hominoids. Subsequent workers interpreted these differences in phylogenetic, functional, and behavioral frameworks and speculated on the history of vertebral numbers during human evolution. Even in a modern phylogenetic framework and with greatly expanded sample sizes of hominoid species, researchers' conclusions vary drastically, positing that hominins evolved from either a "long-backed" (numerically long lumbar column) or a "short-backed" (numerically short lumbar column) ancestor. We show that these disparate interpretations are due in part to the use of different criteria for what defines a lumbar vertebra, but argue that, regardless of which lumbar definition is used, hominins are similar to their great ape relatives in possessing a short trunk, a rare occurrence in mammals and one that defines the clade Hominoidea. Furtherm...
Ever since the seminal papers of Keith and Schultz, hominoid primate ribcages have been described... more Ever since the seminal papers of Keith and Schultz, hominoid primate ribcages have been described as either " funnel-" or " barrel-shaped. " Following this dichotomic typology, it is currently held that Homo sapiens and hylobatids (gibbons and siamangs) share a barrel-shaped ribcage and that they are more similar to each other than to the funnel-shaped thoraces of great apes (Gorilla, Pan, and Pongo). Other researchers hypothesized that thoracic width and the invagination of the thoracic spine into the thorax are related to allometry. However, analyses that take into account the complex three-dimensional (3D) shape of the ribcage are lacking. Here, we address hypotheses about thorax shape and evolution using 3D morphometrics of thoraces in anatomical connection obtained by computed tomography scans of 23 hominoid cadavers and 10 humans and examining thorax compartments composed of seven ribs (1e7 thorax) and of 11 ribs (1e11 thorax). In the 1e7 thorax analyses, the human thorax is uniquely flat because of torsion of the upper and central ribs, differing from all non-human hominoids including hylobatids. In the 1e11 thorax analyses, humans are markedly different from African great apes, with hylobatids and orangutans intermediate. In full shape space analyses, affinities between orangutans and humans on the one hand and between hylobatids and African great apes on the other are evident. Therefore, we reject the hypothesis that humans and hylobatids bear any special affinities in overall 3D thorax shape to each other. We find that larger thoraces are wider and flatter, with a more invaginated spine, supporting the allometric hypothesis. Hominoid thorax variation shows complex interactions between allometry, rib curves, torsion, and declination, and the morphology of the costo-vertebral joint and the thoracic vertebral column. When considering functional specializations alongside phylogenetic relationships, an overly simplistic dichotomy between funnel-shaped and barrel-shaped thoraces is not supported.
The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Cham... more The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens,
within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but
more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of
approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species.
The social brain hypothesis posits that social complexity is the primary driver of primate cognit... more The social brain hypothesis posits that social complexity is the primary driver of primate cognitive complexity, and that social pressures ultimately led to the evolution of the large human brain. Although this idea has been supported by studies indicating positive relationships between relative brain and/or neocortex size and group size, reported effects of different social and mating systems are highly conflicting. Here, we use a much larger sample of primates, more recent phylogenies, and updated statistical techniques, to show that brain size is predicted by diet, rather than multiple measures of sociality, after controlling for body size and phylogeny. Specifically, frugivores exhibit larger brains than folivores. Our results call into question the current emphasis on social rather than ecological explanations for the evolution of large brains in primates and evoke a range of ecological and developmental hypotheses centred on frugivory, including spatial information storage, extractive foraging and overcoming metabolic constraints.
Cervical vertebrae are rare in the early hominin fossil record, presenting a challenge for unders... more Cervical vertebrae are rare in the early hominin fossil record, presenting a challenge for understanding the evolution of the neck and head carriage in hominin evolution. Here, we examine the cervical vertebrae of Australopithecus sediba, which unlike other South African taxa is known from associated cervical vertebrae. The A. sediba cervical vertebrae exhibit human-like values for wedging, pedicle cross-sectional areas, and articular facet heights, indicating reduced ventral loading relative to African apes. These features combine with a pattern of vertebral body bone distribution and caudally progressive size expansion suggesting a mode of cervical lordosis, load mitigation, and head carriage similar to humans and distinct from the cantilevered mode of head carriage of the extant African great apes. Yet these derived features in A. sediba are accompanied by ape-like vertebral body and dorsal pillar sizes, articular facet orientation, and uncinate process morphology signaling reduced lateral and rotational coupled movements between vertebral elements and indicate a considerably stiffer neck than in humans. A primitively long and horizontally-oriented C7 spinous process is likely related to a prognathic viscer-ocranium, although the complimentary C3 spinous process is short, implying large moments emanating from scapular and shoulder elevators rather than large muscles of head stabilization. Cross-sectional spinous process shape and robust anterior tubercles similarly signal increased arm elevation consistent with climbing behavior in corroboration with arboreal signatures previously observed in the shoulder, arms, and hand of A. sediba. Spinal canal shape and size suggests that A. sediba lacked the cervical spinal cord enlargement of Homo that confers humans with enhanced motor control to the upper limbs. The cervical spine of A. sediba thus presents a mosaic of primitive and derived characters, with anatomical features relating to neck posture and head carriage mirroring humans juxtaposed with most other aspects of functional anatomy resembling chimpanzees.
ABSTRACT shape of the innominates. Here a series of VOIs proceeding from the level of the posteri... more ABSTRACT shape of the innominates. Here a series of VOIs proceeding from the level of the posterior inferior iliac spine (PIIS) toward the acetabulum were used. They were scaled by the geometric means of measurements of each ilium, to facilitate comparison of homologous regions. Bone volume fell in both ilia as the scans proceeded inferiorly, likely due to the relief of this region from the actions of the gluteal muscles. No differences in SVD were found. Bone volume was higher in the chimpanzee than in the orangutan, consistent with the prediction. This study was funded by a Bigel Endowment Grant, a Zelnick Research Award, and the Center for Human Evolutionary Studies at Rutgers University. An examination of pubertal development in human skeletal remains from medieval England. FIONA C. SHAPLAND. Archaeology, University of Reading. In societies where date of birth was rarely formally recorded, the perception of individuals as children or adults was inevitably dependent on the physical process of puberty, but this subject has to date received little attention in bioarchaeology. Based on modern data, it is possible to identify specific dental and skeletal maturation events that closely correspond with the external changes of puberty: the development of the mandibular canine, hamate, hand phalanges, iliac crest, cervical vertebrae and distal radius. This paper presents the results of an application of these methods to two large skeletal collections from Medieval England: St Peter's Church, Barton-upon-Humber and St Mary Spital, London. Examining pubertal development alongside chronological age in these two very different populations provides an insight into the possible environmental and social factors that affected this maturation process in the past. In both populations, the onset of puberty appears to be occurring at a similar age to 20 th century adolescents, but the later stages of puberty were significantly delayed, in some cases by four or five years in comparison to modern standards. Age at menarche also seems to have been being affected, particularly in the urban group. This analysis suggests that the timing and progress of puberty in medieval England was being influenced by environmental factors including nutrition, exposure to infection and physical labour. Funded by the Leverhulme Trust as part of the three year project: 'Adolescence, health and migration in Medieval England'. The evolution of brain size and longevity in mammals.
ABSTRACT maturation of Neandertals, a large sample (n = 42) of fossil infants, juveniles, subadul... more ABSTRACT maturation of Neandertals, a large sample (n = 42) of fossil infants, juveniles, subadults and adults is compared to an ontogenetic sequence for modern humans (n = 294) using an interpolation of growth trajectories generated from piecewise regression. Modeled growth trajectories and shape changes in the calvarium, face and mandible are subsequently explored in a multivariate framework. The two species of Pan (P. troglodytes, n = 156 and P. paniscus, n = 151) provide a benchmark upon which to evaluate the differences between Neandertals and modern humans. Craniofacial changes during the postnatal maturation of Neandertals and modern humans are complex and no single description can adequately characterize differences in growth rates and the duration of the growth of traits. Although Neandertals are larger at birth for many craniofacial features, modeled growth curves indicate Neandertal life cycle maturation was accelerated only for some mandibular and palatal dimensions. For dimensions of the calotte, such as upper cranial height and cranial length, it is modern humans who exhibit a more rapid growth rate but with a shorter duration of growth compared to Neandertals. To the extent that life cycle age can be reconstructed from dental eruption, modeled growth curves for Neandertals imply that they achieved craniofacial maturation at ages comparable to those characterizing modern humans suggesting fundamental patterns of human life history arose in an ancestor of archaic and modern Homo., 3 Institute for the Study of the Ancient World, New York University, 4 National Museum of Natural History, Smithsonian Institution. Stable isotope analysis has been used to reconstruct infant feeding practices, and to evaluate developmental metabolic conditions. Several studies have documented isotopic changes during growth of tissues with relatively fast accretion rates, however intra-individual isotopic variation within these tissues has not been fully addressed. To evaluate intra-individual variation, 40 bone samples were collected from a well-preserved fetal individual (37 weeks gestation) from the Kellis 2 Cemetery (c. 100-360 AD), Dakhleh Oasis, Egypt. Samples were selected based on known time-sensitive fetal development of primary and secondary ossification centers. Results from analyses of bone collagen (n = 22) indicate intra-individual variation greater than 1.2‰ for δ 13
International Journal of Primatology, 2010
eLife, May 9, 2017
The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Cham... more The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens, within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of approximately 610 ml and associated postcranial ...
PaleoAnthropology, 2018
Australopithecus sediba is known from two partial skeletons, Malapa Hominins 1 and 2 (MH1 and MH2... more Australopithecus sediba is known from two partial skeletons, Malapa Hominins 1 and 2 (MH1 and MH2), a juvenile
male and an adult female, respectively. Forty-eight elements of the axial skeleton, including vertebrae, ribs, a
sternum, and a sacrum, are known from MH1 and MH2. Here, we describe these ~2.0 Ma fossils and provide raw
data and plots of standardized measurements. We revisit the serial positions of the previously described vertebrae
and ribs proposed in their initial announcements and provide revised identifications. Additionally, we include
in our descriptions and analyses new axial material. Finally, we also test the hypothesis that multiple species are
represented in the MH1 and MH2 material and specifically that MH1’s lumbar vertebrae belong to a member of
the genus Homo, whereas those of MH2 belong to Australopithecus. We do not find support for this hypothesis, and
instead attribute differences between MH1 and MH2 to their age difference and incomplete growth of the vertebral
body in juvenile MH1.
American journal of physical anthropology, Jan 27, 2018
Lower thoracic widths and curvatures track upper pelvic widths and iliac blades curvatures in hom... more Lower thoracic widths and curvatures track upper pelvic widths and iliac blades curvatures in hominins and other primates (torso integration hypothesis). However, recent studies suggest that sexual dimorphism could challenge this assumption in Homo sapiens. We test the torso integration hypothesis in two modern human populations, both considering and excluding the effect of sexual dimorphism. We further assess covariation patterns between different thoracic and pelvic levels, and we explore the allometric effects on torso shape variation. A sex-balanced sample of 50 anatomically connected torsos (25 Mediterraneans, 25 Sub-Saharan Africans) was segmented from computed tomography scans. We compared the maximum medio-lateral width at seventh-ninth rib levels with pelvic bi-iliac breadth in males and females within both populations. We measured 1,030 (semi)landmarks on 3D torso models, and torso shape variation, mean size and shape comparisons, thoraco-pelvic covariation and allometric ...
The social brain hypothesis posits that social complexity is the primary driver of primate cognit... more The social brain hypothesis posits that social complexity is the primary driver of primate cognitive complexity, and that social pressures ultimately led to the evolution of the large human brain. Although this idea has been supported by studies indicating positive relationships between relative brain and/or neocortex size and group size, reported effects of different social and mating systems are highly conflicting. Here, we use a much larger sample of primates, more recent phylogenies, and updated statistical techniques, to show that brain size is predicted by diet, rather than multiple measures of sociality, after controlling for body size and phylogeny. Specifically, frugivores exhibit larger brains than folivores. Our results call into question the current emphasis on social rather than ecological explanations for the evolution of large brains in primates and evoke a range of ecological and developmental hypotheses centred on frugivory, including spatial information storage, ex...
American Journal of Physical Anthropology, 2018
Differences in thorax shape between humans and the great apes are well documented, with the narro... more Differences in thorax shape between humans and the great apes are well documented, with the narrow upper thorax and wide lower thorax of apes contrasting with the opposite pattern in fossil Homo and extant humans. Interestingly, current reconstructions of thoraces in small-bodied hominins, such as the Australopithecus afarensis A.L. 288-1, may feature a smaller, more apelike pulmonary thorax (upper thorax), while its larger-bodied conspecific KSD-VP-1/1 is suggested to be more human with a relatively expanded upper thorax. Toward understanding this dichotomy, we examine the relationship between body size and thorax shape, and model trajectories of the upper limb relative to differently shaped thoraces. We show that variation in thorax shapes facilitate or constrain certain locomotor patterns, as a small upper with an expanded lower thorax facilitates knuckle-walking, orienting the upper limb close to the sagittal midline and center of gravity during locomotion, and confers efficient scapular movement around the ribcage. Conversely, an expanded upper and small lower thorax better facilitates bipedality, facilitating more efficient arm swing and energy return from upper limb momentum, while lower thoracic expansion constrains arm swing in bipedal locomotion. Since lung volume and body mass scale isometrically, increases in lung capacity (and concomitant expansion of the thorax) would be best apportioned to the lower thorax in knuckle-walkers. By contrast, increases in lung capacity and thorax expansion in bipeds are best apportioned superiorly. Thus, locomotor constraints, in concert with the isometric relationship between body size and lung size, may explain thoracic shape variation in early hominins.
American Journal of Physical Anthropology, 2012
Journal of Human Evolution, 2021
Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft repres... more Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft represents pathological traumatic bowing from a childhood fall. Shape analysis in a sample of apes, hominins and modern humans, including clinical humans with this pathology rejects the traumatic bowing hypothesis. Instead, the ‘Little Foot’ ulna reflects a natural degree of curvature observed in apes and several early hominins.
Journal of Human Evolution, 2021
Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft repres... more Previous work suggests the significant curvature of the StW 573 (‘Little Foot’) ulna shaft represents pathological traumatic bowing from a childhood fall. Here we perform Elliptical Fourier shape analysis in a sample of apes, hominins and modern humans, including clinical humans with this pathology, and we reject the traumatic bowing hypothesis. Instead, the ‘Little Foot’ ulna reflects a natural degree of curvature observed in apes and several early hominins.
Nature, 2020
Danuvius guggenmosi is a new species of Miocene hominoid from the 11.62 Ma site of Hammerschmiede... more Danuvius guggenmosi is a new species of Miocene hominoid from the 11.62 Ma site of Hammerschmiede. Based on interpretations of vertebrae and limbs, Böhme and colleagues infer that Danuvius exhibited “joint positions and loading patterns of both hominin bipedalism...and extant great ape suspension” (p.2). While we agree that Danuvius was suspensory, we find the functional interpretation of bipedality to be unfounded on morphological grounds. We therefore call into question the evolutionary scenario for the origin of hominin bipedalism proposed by Böhme and colleagues.
American journal of physical anthropology, 2016
Ever since Tyson (1699), anatomists have noted and compared differences in the regional numbers o... more Ever since Tyson (1699), anatomists have noted and compared differences in the regional numbers of vertebrae among humans and other hominoids. Subsequent workers interpreted these differences in phylogenetic, functional, and behavioral frameworks and speculated on the history of vertebral numbers during human evolution. Even in a modern phylogenetic framework and with greatly expanded sample sizes of hominoid species, researchers' conclusions vary drastically, positing that hominins evolved from either a "long-backed" (numerically long lumbar column) or a "short-backed" (numerically short lumbar column) ancestor. We show that these disparate interpretations are due in part to the use of different criteria for what defines a lumbar vertebra, but argue that, regardless of which lumbar definition is used, hominins are similar to their great ape relatives in possessing a short trunk, a rare occurrence in mammals and one that defines the clade Hominoidea. Furtherm...
Ever since the seminal papers of Keith and Schultz, hominoid primate ribcages have been described... more Ever since the seminal papers of Keith and Schultz, hominoid primate ribcages have been described as either " funnel-" or " barrel-shaped. " Following this dichotomic typology, it is currently held that Homo sapiens and hylobatids (gibbons and siamangs) share a barrel-shaped ribcage and that they are more similar to each other than to the funnel-shaped thoraces of great apes (Gorilla, Pan, and Pongo). Other researchers hypothesized that thoracic width and the invagination of the thoracic spine into the thorax are related to allometry. However, analyses that take into account the complex three-dimensional (3D) shape of the ribcage are lacking. Here, we address hypotheses about thorax shape and evolution using 3D morphometrics of thoraces in anatomical connection obtained by computed tomography scans of 23 hominoid cadavers and 10 humans and examining thorax compartments composed of seven ribs (1e7 thorax) and of 11 ribs (1e11 thorax). In the 1e7 thorax analyses, the human thorax is uniquely flat because of torsion of the upper and central ribs, differing from all non-human hominoids including hylobatids. In the 1e11 thorax analyses, humans are markedly different from African great apes, with hylobatids and orangutans intermediate. In full shape space analyses, affinities between orangutans and humans on the one hand and between hylobatids and African great apes on the other are evident. Therefore, we reject the hypothesis that humans and hylobatids bear any special affinities in overall 3D thorax shape to each other. We find that larger thoraces are wider and flatter, with a more invaginated spine, supporting the allometric hypothesis. Hominoid thorax variation shows complex interactions between allometry, rib curves, torsion, and declination, and the morphology of the costo-vertebral joint and the thoracic vertebral column. When considering functional specializations alongside phylogenetic relationships, an overly simplistic dichotomy between funnel-shaped and barrel-shaped thoraces is not supported.
The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Cham... more The Rising Star cave system has produced abundant fossil hominin remains within the Dinaledi Chamber, representing a minimum of 15 individuals attributed to Homo naledi. Further exploration led to the discovery of hominin material, now comprising 131 hominin specimens,
within a second chamber, the Lesedi Chamber. The Lesedi Chamber is far separated from the Dinaledi Chamber within the Rising Star cave system, and represents a second depositional context for hominin remains. In each of three collection areas within the Lesedi Chamber, diagnostic skeletal material allows a clear attribution to H. naledi. Both adult and immature material is present. The hominin remains represent at least three individuals based upon duplication of elements, but
more individuals are likely present based upon the spatial context. The most significant specimen is the near-complete cranium of a large individual, designated LES1, with an endocranial volume of
approximately 610 ml and associated postcranial remains. The Lesedi Chamber skeletal sample extends our knowledge of the morphology and variation of H. naledi, and evidence of H. naledi from both recovery localities shows a consistent pattern of differentiation from other hominin species.
The social brain hypothesis posits that social complexity is the primary driver of primate cognit... more The social brain hypothesis posits that social complexity is the primary driver of primate cognitive complexity, and that social pressures ultimately led to the evolution of the large human brain. Although this idea has been supported by studies indicating positive relationships between relative brain and/or neocortex size and group size, reported effects of different social and mating systems are highly conflicting. Here, we use a much larger sample of primates, more recent phylogenies, and updated statistical techniques, to show that brain size is predicted by diet, rather than multiple measures of sociality, after controlling for body size and phylogeny. Specifically, frugivores exhibit larger brains than folivores. Our results call into question the current emphasis on social rather than ecological explanations for the evolution of large brains in primates and evoke a range of ecological and developmental hypotheses centred on frugivory, including spatial information storage, extractive foraging and overcoming metabolic constraints.
Cervical vertebrae are rare in the early hominin fossil record, presenting a challenge for unders... more Cervical vertebrae are rare in the early hominin fossil record, presenting a challenge for understanding the evolution of the neck and head carriage in hominin evolution. Here, we examine the cervical vertebrae of Australopithecus sediba, which unlike other South African taxa is known from associated cervical vertebrae. The A. sediba cervical vertebrae exhibit human-like values for wedging, pedicle cross-sectional areas, and articular facet heights, indicating reduced ventral loading relative to African apes. These features combine with a pattern of vertebral body bone distribution and caudally progressive size expansion suggesting a mode of cervical lordosis, load mitigation, and head carriage similar to humans and distinct from the cantilevered mode of head carriage of the extant African great apes. Yet these derived features in A. sediba are accompanied by ape-like vertebral body and dorsal pillar sizes, articular facet orientation, and uncinate process morphology signaling reduced lateral and rotational coupled movements between vertebral elements and indicate a considerably stiffer neck than in humans. A primitively long and horizontally-oriented C7 spinous process is likely related to a prognathic viscer-ocranium, although the complimentary C3 spinous process is short, implying large moments emanating from scapular and shoulder elevators rather than large muscles of head stabilization. Cross-sectional spinous process shape and robust anterior tubercles similarly signal increased arm elevation consistent with climbing behavior in corroboration with arboreal signatures previously observed in the shoulder, arms, and hand of A. sediba. Spinal canal shape and size suggests that A. sediba lacked the cervical spinal cord enlargement of Homo that confers humans with enhanced motor control to the upper limbs. The cervical spine of A. sediba thus presents a mosaic of primitive and derived characters, with anatomical features relating to neck posture and head carriage mirroring humans juxtaposed with most other aspects of functional anatomy resembling chimpanzees.
American Journal of Physical Anthropology
The bony pelvis is perhaps one of the most complicated structures in the body. Considering its co... more The bony pelvis is perhaps one of the most complicated structures in the body. Considering its complex structure, using three-dimensional (3D) geometric morphometrics in analyzing shape variation between primate groups is important as it maintains the 3D shape of the innominate. Locomotor modes can vary within and between species, and primates are not restricted to a single style. Platyrrhines are mainly arboreal quadrupeds that also display leaping behaviors. The exception are the atelines, a group of species who use suspensory and climbing behaviors while locomoting and feeding similar to apes, albeit with prehensile tails. The aim of this study is to investigate if there is convergence in shape of the pelvis in suspensory primates, and to elucidate what factors (such as function, phylogeny, and/or allometry) might be driving variation in shape. Following Lewton (2015), 3D landmarks were collected from a range of anthropoid primates (n=133) with a focus on atelids and hominoids. Results show that the first axis of Procrustes-adjusted variance (accounting for 52% of total shape variation) correlates strongly with centroid size and is therefore driven by allometry. Subsequent axes demonstrate clear separation of locomotor groups. A phylomorphospace analysis shows that Ateles, hylobatids, and some colobines pull away from their respective outgroups in similar directions. Future analyses will include semi-landmarks to better capture the complex shape of the pelvis and the inclusion of fossil pelves to test hypotheses of locomotor behavior in extinct primates.
The human pubic symphysis develops, fuses on a late schedule, and degenerates in a systematic way... more The human pubic symphysis develops, fuses on a late schedule, and degenerates in a systematic way such that it is often considered the gold standard of non-dental aging methods. One of the most commonly used aging systems is that of Suchey-Brooks. It is unknown if humans’ closest living relatives, the African apes, share delayed fusion of the pubic symphysis with humans and if the Suchey-Brooks method can be used to age ape pubic remains. Here gorilla (N=20) and chimpanzee (N=25) pubic symphyses from specimens whose chronological age is not known are visually examined, seriated and assigned to the appropriate phase of Suchey-Brooks then correlated with age ranges provided by dental and skeletal fusion.
Fusion of the pubic symphysis in the African apes is maturational, unlike in humans. Therefore, the pubic symphysis is of limited use in aging as it does not extend the ability to age skeletal remains beyond the schedules known for teeth and other bones. The phases of symphysis maturation correlate with the fusion of other bones and the eruption of permanent teeth. Thus rough age ranges can be assessed for phases I-III, but apes are generally mature by phase IV and thus phases IV-VI cannot be correlated with any age group.
Future studies require chronologically aged samples in order to create phases specific to the apes that do not need to rely on correlation with maturational events. The lack of delayed fusion confirms that this trait evolved in the hominin lineage, likely due to obstetric pressures.
Numbers of precaudal vertebrae are relatively stable in mammals, with cervical vertebrae fixed at... more Numbers of precaudal vertebrae are relatively
stable in mammals, with cervical vertebrae
fixed at seven in nearly all species, 19-20 thoracolumbar
vertebrae (TL), and 29-30 precaudal
vertebrae (PC), whereas the number of tail vertebrae
is highly variable both within and between
major clades. Hominoid primates have varyingly
short trunks, generally between 16 (orangutans,
eastern gorillas) and 18 (hylobatids) TL, 28-31
PC, and 1-5 coccygeal vertebrae (Co); they lack
external tails. Researchers have focused mostly
on numbers of PC and the observation that
chimpanzees and especially bonobos (panins)
possess more PC vertebrae than humans and
other hominoids. More appropriately, if Co are
included to yield a total vertebra count, humans
and panins possess similar numbers of total
vertebrae (TV=33). This is because humans tend
to possess one less sacral segment and one
more Co than panins. When combined, humans and panins possess 17 TL and 9 sacrocaudal
vertebrae (SC). Together, the evidence from TV is
best interpreted in a homeotic framework, which
reflects the expression boundaries of underlying
Hox genes. Hox10 expression boundaries correspond
with the TL and SC borders; thus, a cranial
shift of Hox10 expression in an ancestor with a
chimpanzee- or bonobo-like vertebral formula
(7C:13T:4L:6S:3Co; TV=33) would result in homeotic
changes at the TL and SC boundaries while
maintaining the integrity of the lumbosacral
boundary (and TL number), resulting in a humanlike
vertebral formula (7C:12T:5L:5S:4Co; TV=33).
This evolutionary scenario involves neither the
extensive homoplasy in extant apes nor reversals
in human evolution proposed by some
researchers.
Nearly all mammals possess seven cervical vertebrae, and many groups retain the primitive number ... more Nearly all mammals possess seven cervical
vertebrae, and many groups retain the primitive
number of 19 thoracolumbar vertebrae (TL),
implying long-term evolutionary stasis. Recently,
Galis and colleagues proposed that stabilizing
selection for agility and fast running canalizes variation
because evolutionary change in TL number
can result in incomplete homeotic changes at
the lumbo-sacral boundary; the resulting partially
sacralized vertebrae might potentially impede
intervertebral movement and leave individuals
at a disadvantage for chasing prey or escaping
predators. Galis et al. showed that slow-running
species are characterized by higher levels of
variation than fast-running species in two clades
(Carnivora and Artiodactyla), with two additional
clades composed of slow-moving members
(Afrotheria and Monotremata) showing elevated
levels of TL variation. We test the hypothesis
proposed by Galis and colleagues by including
additional clades of mammals (Marsupalia,
Xenarthra, Rodentia, and Primates) in our analyses.
Our results do not fully support Galis et
al.’s hypothesis: slow-running species do not
have elevated levels of variation in TL number
compared to fast-moving species. Rather, we find that mammals adapted to antipronograde positional
behaviors (e.g., hominoid primates, sloths,
lorisids) and others with distinct, non-pronograde
body plans (e.g., bats, cetaceans) are characterized
by high levels of variation. This suggests that
pronogrady, not strictly the need for fast speed,
might be the source of stabilizing selection and
canalization on TL number in mammals. Release
of this constraint in hominoids may have allowed
for the evolution of the diverse locomotor behaviors
observed in this clade.
Long bone cross-sectional properties are reflective of mechanical loading environment and have be... more Long bone cross-sectional properties are reflective
of mechanical loading environment and
have been used to make behavioral inferences.
However, the genetic basis of this complex
morphology remains unknown. Human chromosome
region 11q12-13 has been identified
multiple times as a potential region housing
gene(s) associated with variation in bone mineral
density (BMD) and cross-sectional geometric
properties. Specifically, two candidate genes–
LRP5 and TCIRG1–have been singled out from
this region because of their functional roles in
bone development and remodeling and their
associations with diseases of the skeleton such
as osteoporosis and osteopetrosis.
Given that selection acting on a phenotypic
character would also have an effect on the
underlying genetic mechanism and vice versa.
We expect that evolutionary changes in bone
cross-sectional properties would be reflected in
the underlying gene sequences. Using selection
analysis, we estimated the rate of nonsynonymous
changes (dN) to synonymous changes
(dS) of these two genes in 12 primate species.
Preliminary results showed that both loci were
under purifying (negative) selection, which is
expected as mutations in both genes would
lead to detrimental consequences. Specifically,
TCIRG1 showed species-specific dN/dS ratios as
opposed to the little variation observed in LRP5.
The branch leading to the human-chimpanzee
clade also has a significantly higher ratio than
the rest of the tree. Whether phenotypic variation
in cross-sectional geometric properties in these
primate species correspond to the change in
evolutionary rate of TCIRG1 will be a main focus
for further study.
The thorax and pelvis are integrated systems, important for understanding human body shape and ev... more The thorax and pelvis are integrated systems,
important for understanding human body shape
and evolution. Research has shown that in the
lower thorax, sexual dimorphism and allometry
produce wider ribcages in larger males and
narrower ones in smaller females. If the pelvis
and thorax are integrated, we would expect that
the upper pelvis would similarly be wider in larger
males and narrower in smaller females. Within
this framework of torso integration, we explore
allometry and sexual dimorphism in ossa coxae.
From a human sample with variation in body
size (25 males, 25 females, Bass Collection;
N=3 small-bodied humans, AMNH), we measured
142 (semi)landmarks on coxal bones and
analyzed them using Geometric morphometrics.
These results explore how sexual dimorphism
and allometry affect torso width measured from
pelvis morphology compared to previous studies
of the ribcage. Males and females differ both allometrically
and non-allometrically. Allometrically,
smaller individuals have wider ossa coxae than
larger individuals, regardless of sex; non-allometrically,
females have a wider pelvic inlet than
males, presumably due to obstetric adaptations.
Both findings contradict previous results on lower
ribcage dimensions. Our results show that while
allometry and sexual dimorphism are important
factors explaining ossa coxae morphology, they affect the pelvis and thorax differently, challenging
the torso integration model. Morphological and
positional relations between both hip bones and
the sacrum could account for this. However, interactions
between 3D-pelvis shape and size and
stature are likely important in the context of pelvis
reconstructions and body shape in small-bodied
humans and hominins.
H. naledi shows a mosaic morphological pattern with several derived (Homo-like) features of the s... more H. naledi shows a mosaic morphological pattern
with several derived (Homo-like) features of the
skull, hands and feet, and primitive (australopith-
like) features in the ribcage, shoulder, and
pelvis. This pattern reflects a morphology that
might be expected of a hominin at the evolutionary
transition between Australopithecus and
Homo. Two thoracic vertebrae from levels 10
and 11 and the proximal aspect of an 11th rib
were found in near anatomical connection in
the Dinaledi Chamber of Rising Star cave, therefore
likely belonging to the same individual.
In this study we explore this association and
report our ongoing work towards a quantitative
3D reconstruction of the H. naledi thorax. We
measured 512 3D-(semi)landmarks on human
and other hominoid ribcages (hylobatids, Pongo,
Gorilla, Pan; N=33) for geometric morphometric
analyses. Covariation between the 11th rib and
remaining thorax shape was analyzed by partial
least squares analysis (PLS) and overall thorax
variation by principal components analysis
(PCA). PCA results show wide ranges of complex
thoracic variation. Gorilla and Pan are characterized
by highly constricted upper thoraces when
compared to their wide lower ribcages. Pongo and
hylobatids have less narrow upper but also wide
lower thoraces. Those of humans are expanded
superiorly, narrow inferiorly, and with declined
ribs. PLS analyses suggest that the morphology
of the articulated rib-vertebra complex at the 11th
level of H. naledi is compatible with a ribcage with
declined ribs and inferiorly wider than observed
in humans. This corresponds with evidence for
laterally flared iliac blades of the H. naledi pelvis.
The rapid spread of Homo erectus from Africa, especially into the more temperate climates of Eura... more The rapid spread of Homo erectus from Africa,
especially into the more temperate climates of
Eurasia, has been variously attributed to technological,
energetic, and foraging shifts. The
temporal and regional anatomical variation in H.
erectus suggests a high level of developmental
plasticity, or the ability to modify development
in response to environmental conditions.
Developmental plasticity, a key factor in the ability
of H. sapiens to occupy a variety of habitats worldwide,
results in differences in size, shape, and
dimorphism across populations. These differences
predict regional variation, overall smaller
adult sizes, and lower levels of dimorphism in
instances of resource scarcity and high predator
load. However, determining whether the human
pattern of variability is unique and relatively great
compared to other widely dispersed nonhuman
primates, and whether it can be retrieved from
the skeletal record of these taxa is a non-trivial
question. As part of a broader study that looks
at metric variation in 35 human and nonhuman
primate ‘populations’ from known environmental
contexts and 14 time- and space- restricted paleodemes
of H. erectus and other fossil Homo, here
we delve deeper into the relationship between somatic and skeletal variation in recent Homo
sapiens and Macaca mulatta. We find that
skeletal measurements track somatic measurements
with varying accuracy across different
types of variables but with similar patterns in
both humans and macaques. Further, skeletal
and somatometric variables yield similar patterns
of sexual dimorphism within groups, suggesting
that inferences about fleshed bodies may be
made from carefully chosen skeletal proxies.
Modern humans experience rotational birth, and the size of the neonatal head and shoulders closel... more Modern humans experience rotational birth, and
the size of the neonatal head and shoulders
closely fits the maternal birth canal. It is unclear
when this form of birth evolved. Fossils such
as Sts 14—a partial Australopithecus africanus
pelvis—can shed light on this issue, but it is
incomplete and partly deformed. Sts 14 has been
reconstructed manually and digitally by different
researchers using different methods. Since each
reconstruction is a hypothesis, new methods
can be used to test previous reconstructions and
help narrow down the range of possible pelvic
morphologies, which in turn affects the interpretation
of the mechanism of birth in A. africanus.
Here, we reconstruct Sts 14 using 3D surface
models of the original fossils. Complete,
undistorted portions on the left side were
mirror-imaged across the sagittal midplane to
fill in missing portions on the right. The auricular
surfaces of the sacrum and ilium were aligned
by matching landmarks on the two surfaces.
The pubis was recreated using an expectation
maximization algorithm utilizing a sample of
modern human females. Measurements were
taken and compared to those reported from a
reconstruction by Berge and Goularas (2010)
and differed by less than 6%. Therefore, their
conclusion that the mechanism of birth was
human-like in Sts14, is supported in our study.
A.L. 288-1 (Australopithecus afarensis) and MH2
(Australopithecus sediba) pelves were also reconstructed
using these methods in order to explore
pelvic morphology within the australopith clade.
Considered individually, many aspects of early hominin cervical anatomy appear more similar to th... more Considered individually, many aspects of early
hominin cervical anatomy appear more similar
to the African great apes than to humans,
suggesting an ape-like pattern of load transfer,
and by extension points to significant differences
with human head carriage.
However, when the australopith cervical spine
is examined as a whole, rather than as separate
isolated elements, a more human-like pattern
emerges. In this context anatomical differences
appear to have only insignificant functional implications
and may be explained as developmental
reciprocates of cranial base morphogenesis.
Corroborating this observation is a nearly
complete series of new cervical vertebrae from
Australopithecus afarensis (KSD-VP-1/1) from
Woranso-Mille, Ethiopia, dated to ~3.6 million
years before present, which we compare to a
sample of Homo sapiens (N=57), Pan troglodytes
(20), Gorilla gorilla (20) Au afarensis (2) Au. sediba (2), Homo erectus (2), Pleistocene hominins from
Sima de los Huesos (3), and Neandertals (7).
The new Au. afarensis fossils from Woranso-Mille
reveal an aggregate biomechanical and enthesopathological
signature typical of Homo sapiens
and present a surprisingly human-like kinematic
signal. These lines of evidence evince a mode
of head posture in early hominins very similar to
modern humans as early as 3.6 million years ago.
Spinal Evolution: Morphology, Function, and Pathology of the Spine in Hominoid Evolution, 2019
The early hominin (Ardipithecus and Australopithecus) fossil record contains over 100 preserved v... more The early hominin (Ardipithecus and Australopithecus) fossil record contains over 100 preserved vertebral elements (n = 107; approximately half of which are well-preserved), ~65% of which haven’t been described since the turn of the millennium (Table 1). Many are fragments, some for which detailed descriptions are pending (e.g., those of Australopithecus anamensis; Meyer and Williams, in review). Australopithecus afarensis and Australopithecus sediba are known from cervical, thoracic, and lumbar vertebrae, whereas Australopithecus africanus is known from thoracic and lumbar vertebrae but not cervical vertebrae. A partial skeleton from Member 4 of Sterkfontein, StW 573, preserves vertebrae from all presacral regions, but its species designation is debated and not yet announced in the literature. Other early hominin species, such as Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus kadabba, Australopithecus deyiremeda, Australopithecus barelghazali, and Australopithecus garhi do not preserve vertebrae. Vertebrae from Swartkrans and Cooper’s Cave are thought to belong to either Paranthropus or Homo and are discussed in Meyer and Williams (this volume). The vertebrae discussed in this chapter are from five sites in East and South Africa: Aramis, Asa Issie, and Hadar from the Afar Depression of Ethiopia, and Sterkfontein and Malapa in the Cradle of Humankind, South Africa.
Spinal Evolution: Morphology, Function, and Pathology of the Spine in Hominoid Evolution, 2019
In this chapter, we summarize vertebral remains from early Pleistocene Homo, including H. erectus... more In this chapter, we summarize vertebral remains from early Pleistocene Homo, including H. erectus, as well as H. naledi and H. floresiensis fossils from the Middle and Late Pleistocene, respectively. Two partial immature H. erectus skeletons where vertebrae are well represented are KNM-WT 15000 (“Turkana boy”) and the D2700 individual from Dmanisi. Vertebrae from H. naledi are also considered here, including those from the LES1 partial skeleton (“Neo”), despite their younger date to the Middle Pleistocene. We review the fossil record of presacral vertebrae in early Homo, and summarize work on the functional morphology, metameric patterning, and postcranial neuroanatomy of early Homo, comparing and contrasting the presacral spine with their putative australopith forbears and extant apes and humans. Based on the current evidence, the vertebral column of H. erectus possessed a modal number of twelve thoracic and five lumbar segments, as is the case in australopiths, as well as modern humans. The spine of H. erectus reveals key changes relative to earlier hominins, with an expanded thoracolumbar spinal canal offering increased neurovascular capacities, and a ventral pillar (formed by the vertebral bodies) better equipped to mitigate compressive loads and provide energy return. These biological developments are germane to understanding the advent of derived human behaviors, including efficient long-range locomotion and the first hominin expansion out of Africa.