In their recent article "The atlas of StW 573 and the late emergence of human-like head mobility ... more In their recent article "The atlas of StW 573 and the late emergence of human-like head mobility and brain metabolism" Beaudet and colleagues (Scientific Reports, March 2020) contend that StW 573 had lower metabolic costs for cerebral tissues and that blood perfusion of these tissues increased recently over the course of hominin evolution 1. This conclusion is in large part based on the assumption of a correlation between the size of the fossil vertebra's transverse foramen and arterial canal diameters, and by extension, they use the foramen's cross-sectional area in conjunction with the size of the cranium's carotid canal to reconstruct blood flow volume to the brain as a proxy of the brain's metabolic demands 2. As I show here, these assumptions are unsupported because the C1 cervical vertebra cannot help indicate hemodynamics or investment in brain metabolism.
American journal of biological anthropology, Sep 21, 2022
ObjectivesIn humans and known fossil hominins, lumbar lordosis is produced by vertebral body wedg... more ObjectivesIn humans and known fossil hominins, lumbar lordosis is produced by vertebral body wedging and other bony and soft tissue features such as the shape of the intervertebral discs. Current techniques for quantifying the wedging of vertebral bodies are limited in utility, especially when analyzing incomplete fossil material. Here, we introduce a 3D method to quantify vertebral body wedging angles that yields the angles between two “best fit” planes in the software GeoMagic Wrap (3D Systems).Materials and MethodsTo test that this new method is repeatable with existing methods, we measure the wedging of 320 lumbar vertebrae representing 64 modern human individuals. For each vertebra, wedging angles were calculated from linear measurements taken with calipers and compared with estimates generated from the 3D best fit plane method. We also apply the 3D plane method to fossil hominin lumbar vertebrae, including newly described lumbar vertebrae of Homo naledi, the majority of which do not preserve the four landmarks necessary to calculate wedging angles using the traditional approach.ResultsThe results of the two methods are highly and significantly correlated (r2 = 0.98, p < 0.0001). The 3D plane method was successfully applied to nearly all of the fossil hominin specimens included in the study.DiscussionThe new 3D plane method introduced here is repeatable with the traditional linear measurement method and allows for the estimation of wedging angles in incomplete material. When applied to Homo naledi lumbar vertebrae, similarities to other fossil hominins and modern humans are found.
Homo naledi is a previously unknown species of extinct hominin discovered within the Dinaledi Cha... more Homo naledi is a previously unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Gauteng, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations, with a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including H. erectus, H. habilis, or H. rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike leg and foot. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, fingers, pelvis, and proximal femur. Nonetheless, the shared derived features that connect H. naledi with other members of Homo occupy most regions of the H. naledi skeleton and represent distinct functional systems, including locom...
Because the ulna supports and transmits forces during movement, its morphology can signal aspects... more Because the ulna supports and transmits forces during movement, its morphology can signal aspects of functional adaptation. To test whether, like extant apes, some hominins habitually recruit the forelimb in locomotion, we separate the ulna shaft and ulna proximal complex for independent shape analyses via elliptical Fourier methods to identify functional signals. We examine the relative influence of locomotion, taxonomy, and body mass on ulna contours in Homo sapiens (n ¼ 22), five species of extant apes (n ¼ 33), two Miocene apes (Hispanopithecus and Danuvius), and 17 fossil hominin specimens including Sahelanthropus, Ardipithecus, Australopithecus, Paranthropus, and early Homo. Ulna proximal complex contours correlate with body mass but not locomotor patterns, while ulna shafts significantly correlate with locomotion. African apes' ulna shafts are more robust and curved than Asian apes and are unlike other terrestrial mammals (including other primates), curving ventrally rather than dorsally. Because this distinctive curvature is absent in orangutans and hylobatids, it is likely a function of powerful flexors engaged in wrist and hand stabilization during knuckle-walking, and not an adaptation to climbing or suspensory behavior. The OH 36 (purported Paranthropus boisei) and TM 266 (assigned to Sahelanthropus tchadensis) fossils differ from other hominins by falling within the knuckle-walking morphospace, and thus appear to show forelimb morphology consistent with terrestrial locomotion. Discriminant function analysis classifies both OH 36 and TM 266 with Pan and Gorilla with high posterior probability. Along with its associated femur, the TM 266 ulna shaft contours and its deep, keeled trochlear notch comprise a suite of traits signaling African ape-like quadrupedalism. While implications for the phylogenetic position and hominin status of S. tchadensis remain equivocal, this study supports the growing body of evidence indicating that S. tchadensis was not an obligate biped, but instead represents a late Miocene hominid with knuckle-walking adaptations.
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 have not been described since the turn of the millennium. Many are fragments, some for which detailed descriptions are pending (e.g., those of Australopithecus anamensis). 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 formalized in the literature. Other early hominin species, such as Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus kadabba, Australopithecus deyiremeda, Australopithecus bahrelghazali, 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.
Lumbar lordosis is a key adaptation to bipedal locomotion in the human lineage. Dorsoventral spin... more Lumbar lordosis is a key adaptation to bipedal locomotion in the human lineage. Dorsoventral spinal curvatures enable the body's center of mass to be positioned above the hip, knee, and ankle joints, and minimize the muscular effort required for postural control and locomotion. Previous studies have suggested that Neandertals had less lordotic (ventrally convex) lumbar columns than modern humans, which contributed to historical perceptions of postural and locomotor differences between the two groups. Quantifying lower back curvature in extinct hominins is entirely reliant upon bony correlates of overall lordosis, since the latter is significantly influenced by soft tissue structures (e.g. intervertebral discs). Here, we investigate sexual dimorphism, ancestry, and lifestyle effects on lumbar vertebral body wedging and inferior articular facet angulation, two features previously shown to be significantly correlated with overall lordosis in living individuals, in a large sample of...
tionary biologist and science historian, argued that ‘‘unconscious manipulation of data may be a ... more tionary biologist and science historian, argued that ‘‘unconscious manipulation of data may be a scientific norm’ ’ because ‘‘scientists are human beings rooted in cultural contexts, not automatons directed toward external truth’’ [1], a view now popular in social studies of science [2–4]. In support of his argument Gould presented the case of Samuel George Morton, a 19th-century physician and phys-ical anthropologist famous for his measure-ments of human skulls. Morton was consid-ered the objectivist of his era, but Gould reanalyzed Morton’s data and in his prize-winning book The Mismeasure of Man [5] argued that Morton skewed his data to fit his preconceptions about human variation.Mor-ton is now viewed as a canonical example of scientific misconduct. But did Morton really fudge his data? Are studies of human variation inevitably biased, as per Gould, or are objective accounts attainable, as Morton attempted? We investigated these questions by remeasuring Morton’s skulls and reexa...
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.
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.
ABSTRACT Photocopy. Thesis (Ph. D.)--University of Pennsylvania, 2005. Includes bibliographical r... more ABSTRACT Photocopy. Thesis (Ph. D.)--University of Pennsylvania, 2005. Includes bibliographical references and index.
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 have not been described since the turn of the millennium. Many are fragments, some for which detailed descriptions are pending (e.g., those of Australopithecus anamensis). 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 formalized in the literature. Other early hominin species, such as Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus kadabba, Australopithecus deyiremeda, Australopithecus bahrelghazali, and Australopithecus garhi, do not preserve vertebrae. Vertebra...
Danuvius guggenmosi is a species of Miocene hominoid from the 11.62-million-year-old site of Hamm... more Danuvius guggenmosi is a species of Miocene hominoid from the 11.62-million-year-old site of Hammerschmiede. On the basis of interpretations of its vertebrae and limbs, Böhme and colleagues infer that Danuvius exhibited ‘joint positions and loading patterns of both hominin bipedalism that emphasize hindlimb extension and spinal curvatures, and extant great ape suspension’. Although we agree that Danuvius was suspensory, we find the functional interpretation of bipedalism 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.
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.
We describe the earliest evidence for neoplastic disease in the hominin lineage. This is reported... more We describe the earliest evidence for neoplastic disease in the hominin lineage. This is reported from the type specimen of the extinct hominin Australopithecus sediba from Malapa, South Africa, dated to 1.98 million years ago. The affected individual was male and developmentally equivalent to a human child of 12 to 13 years of age. A penetrating lytic lesion affected the sixth thoracic vertebra. The lesion was macroscopically evaluated and internally imaged through phase-contrast X-ray synchrotron microtomography. A comprehensive differential diagnosis was undertaken based on gross- and micro-morphology of the lesion, leading to a probable diagnosis of osteoid osteoma. These neoplasms are solitary, benign, osteoid and bone-forming tumours, formed from well-vascularised connective tissue within which there is active production of osteoid and woven bone. Tumours of any kind are rare in archaeological populations, and are all but unknown in the hominin record, highlighting the importa...
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.
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.
Pearce and Dunbar (2011) posit that ambient light levels have an inverse rela onship with orbit s... more Pearce and Dunbar (2011) posit that ambient light levels have an inverse rela onship with orbit size in humans, as they find a la tudinal increase in orbital size in modern humans (N=55) greater than that predicted by total brain or body size, sugges ng that there has been independent selec on for larger orbits in progressively lower light condi ons. By extension, Pearce et al. (2013) hypothesize that because larger eyes necessitate larger visual cor ces, Neandertal brains were propor onately skewed more towards vision, and as a result Neandertals were cogni vely deficient compared with humans.
In their recent article "The atlas of StW 573 and the late emergence of human-like head mobility ... more In their recent article "The atlas of StW 573 and the late emergence of human-like head mobility and brain metabolism" Beaudet and colleagues (Scientific Reports, March 2020) contend that StW 573 had lower metabolic costs for cerebral tissues and that blood perfusion of these tissues increased recently over the course of hominin evolution 1. This conclusion is in large part based on the assumption of a correlation between the size of the fossil vertebra's transverse foramen and arterial canal diameters, and by extension, they use the foramen's cross-sectional area in conjunction with the size of the cranium's carotid canal to reconstruct blood flow volume to the brain as a proxy of the brain's metabolic demands 2. As I show here, these assumptions are unsupported because the C1 cervical vertebra cannot help indicate hemodynamics or investment in brain metabolism.
American journal of biological anthropology, Sep 21, 2022
ObjectivesIn humans and known fossil hominins, lumbar lordosis is produced by vertebral body wedg... more ObjectivesIn humans and known fossil hominins, lumbar lordosis is produced by vertebral body wedging and other bony and soft tissue features such as the shape of the intervertebral discs. Current techniques for quantifying the wedging of vertebral bodies are limited in utility, especially when analyzing incomplete fossil material. Here, we introduce a 3D method to quantify vertebral body wedging angles that yields the angles between two “best fit” planes in the software GeoMagic Wrap (3D Systems).Materials and MethodsTo test that this new method is repeatable with existing methods, we measure the wedging of 320 lumbar vertebrae representing 64 modern human individuals. For each vertebra, wedging angles were calculated from linear measurements taken with calipers and compared with estimates generated from the 3D best fit plane method. We also apply the 3D plane method to fossil hominin lumbar vertebrae, including newly described lumbar vertebrae of Homo naledi, the majority of which do not preserve the four landmarks necessary to calculate wedging angles using the traditional approach.ResultsThe results of the two methods are highly and significantly correlated (r2 = 0.98, p < 0.0001). The 3D plane method was successfully applied to nearly all of the fossil hominin specimens included in the study.DiscussionThe new 3D plane method introduced here is repeatable with the traditional linear measurement method and allows for the estimation of wedging angles in incomplete material. When applied to Homo naledi lumbar vertebrae, similarities to other fossil hominins and modern humans are found.
Homo naledi is a previously unknown species of extinct hominin discovered within the Dinaledi Cha... more Homo naledi is a previously unknown species of extinct hominin discovered within the Dinaledi Chamber of the Rising Star cave system, Gauteng, South Africa. This species is characterized by body mass and stature similar to small-bodied human populations, with a small endocranial volume similar to australopiths. Cranial morphology of H. naledi is unique, but most similar to early Homo species including H. erectus, H. habilis, or H. rudolfensis. While primitive, the dentition is generally small and simple in occlusal morphology. H. naledi has humanlike manipulatory adaptations of the hand and wrist. It also exhibits a humanlike leg and foot. These humanlike aspects are contrasted in the postcrania with a more primitive or australopith-like trunk, shoulder, fingers, pelvis, and proximal femur. Nonetheless, the shared derived features that connect H. naledi with other members of Homo occupy most regions of the H. naledi skeleton and represent distinct functional systems, including locom...
Because the ulna supports and transmits forces during movement, its morphology can signal aspects... more Because the ulna supports and transmits forces during movement, its morphology can signal aspects of functional adaptation. To test whether, like extant apes, some hominins habitually recruit the forelimb in locomotion, we separate the ulna shaft and ulna proximal complex for independent shape analyses via elliptical Fourier methods to identify functional signals. We examine the relative influence of locomotion, taxonomy, and body mass on ulna contours in Homo sapiens (n ¼ 22), five species of extant apes (n ¼ 33), two Miocene apes (Hispanopithecus and Danuvius), and 17 fossil hominin specimens including Sahelanthropus, Ardipithecus, Australopithecus, Paranthropus, and early Homo. Ulna proximal complex contours correlate with body mass but not locomotor patterns, while ulna shafts significantly correlate with locomotion. African apes' ulna shafts are more robust and curved than Asian apes and are unlike other terrestrial mammals (including other primates), curving ventrally rather than dorsally. Because this distinctive curvature is absent in orangutans and hylobatids, it is likely a function of powerful flexors engaged in wrist and hand stabilization during knuckle-walking, and not an adaptation to climbing or suspensory behavior. The OH 36 (purported Paranthropus boisei) and TM 266 (assigned to Sahelanthropus tchadensis) fossils differ from other hominins by falling within the knuckle-walking morphospace, and thus appear to show forelimb morphology consistent with terrestrial locomotion. Discriminant function analysis classifies both OH 36 and TM 266 with Pan and Gorilla with high posterior probability. Along with its associated femur, the TM 266 ulna shaft contours and its deep, keeled trochlear notch comprise a suite of traits signaling African ape-like quadrupedalism. While implications for the phylogenetic position and hominin status of S. tchadensis remain equivocal, this study supports the growing body of evidence indicating that S. tchadensis was not an obligate biped, but instead represents a late Miocene hominid with knuckle-walking adaptations.
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 have not been described since the turn of the millennium. Many are fragments, some for which detailed descriptions are pending (e.g., those of Australopithecus anamensis). 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 formalized in the literature. Other early hominin species, such as Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus kadabba, Australopithecus deyiremeda, Australopithecus bahrelghazali, 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.
Lumbar lordosis is a key adaptation to bipedal locomotion in the human lineage. Dorsoventral spin... more Lumbar lordosis is a key adaptation to bipedal locomotion in the human lineage. Dorsoventral spinal curvatures enable the body's center of mass to be positioned above the hip, knee, and ankle joints, and minimize the muscular effort required for postural control and locomotion. Previous studies have suggested that Neandertals had less lordotic (ventrally convex) lumbar columns than modern humans, which contributed to historical perceptions of postural and locomotor differences between the two groups. Quantifying lower back curvature in extinct hominins is entirely reliant upon bony correlates of overall lordosis, since the latter is significantly influenced by soft tissue structures (e.g. intervertebral discs). Here, we investigate sexual dimorphism, ancestry, and lifestyle effects on lumbar vertebral body wedging and inferior articular facet angulation, two features previously shown to be significantly correlated with overall lordosis in living individuals, in a large sample of...
tionary biologist and science historian, argued that ‘‘unconscious manipulation of data may be a ... more tionary biologist and science historian, argued that ‘‘unconscious manipulation of data may be a scientific norm’ ’ because ‘‘scientists are human beings rooted in cultural contexts, not automatons directed toward external truth’’ [1], a view now popular in social studies of science [2–4]. In support of his argument Gould presented the case of Samuel George Morton, a 19th-century physician and phys-ical anthropologist famous for his measure-ments of human skulls. Morton was consid-ered the objectivist of his era, but Gould reanalyzed Morton’s data and in his prize-winning book The Mismeasure of Man [5] argued that Morton skewed his data to fit his preconceptions about human variation.Mor-ton is now viewed as a canonical example of scientific misconduct. But did Morton really fudge his data? Are studies of human variation inevitably biased, as per Gould, or are objective accounts attainable, as Morton attempted? We investigated these questions by remeasuring Morton’s skulls and reexa...
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.
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.
ABSTRACT Photocopy. Thesis (Ph. D.)--University of Pennsylvania, 2005. Includes bibliographical r... more ABSTRACT Photocopy. Thesis (Ph. D.)--University of Pennsylvania, 2005. Includes bibliographical references and index.
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 have not been described since the turn of the millennium. Many are fragments, some for which detailed descriptions are pending (e.g., those of Australopithecus anamensis). 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 formalized in the literature. Other early hominin species, such as Sahelanthropus tchadensis, Orrorin tugenensis, Ardipithecus kadabba, Australopithecus deyiremeda, Australopithecus bahrelghazali, and Australopithecus garhi, do not preserve vertebrae. Vertebra...
Danuvius guggenmosi is a species of Miocene hominoid from the 11.62-million-year-old site of Hamm... more Danuvius guggenmosi is a species of Miocene hominoid from the 11.62-million-year-old site of Hammerschmiede. On the basis of interpretations of its vertebrae and limbs, Böhme and colleagues infer that Danuvius exhibited ‘joint positions and loading patterns of both hominin bipedalism that emphasize hindlimb extension and spinal curvatures, and extant great ape suspension’. Although we agree that Danuvius was suspensory, we find the functional interpretation of bipedalism 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.
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.
We describe the earliest evidence for neoplastic disease in the hominin lineage. This is reported... more We describe the earliest evidence for neoplastic disease in the hominin lineage. This is reported from the type specimen of the extinct hominin Australopithecus sediba from Malapa, South Africa, dated to 1.98 million years ago. The affected individual was male and developmentally equivalent to a human child of 12 to 13 years of age. A penetrating lytic lesion affected the sixth thoracic vertebra. The lesion was macroscopically evaluated and internally imaged through phase-contrast X-ray synchrotron microtomography. A comprehensive differential diagnosis was undertaken based on gross- and micro-morphology of the lesion, leading to a probable diagnosis of osteoid osteoma. These neoplasms are solitary, benign, osteoid and bone-forming tumours, formed from well-vascularised connective tissue within which there is active production of osteoid and woven bone. Tumours of any kind are rare in archaeological populations, and are all but unknown in the hominin record, highlighting the importa...
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.
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.
Pearce and Dunbar (2011) posit that ambient light levels have an inverse rela onship with orbit s... more Pearce and Dunbar (2011) posit that ambient light levels have an inverse rela onship with orbit size in humans, as they find a la tudinal increase in orbital size in modern humans (N=55) greater than that predicted by total brain or body size, sugges ng that there has been independent selec on for larger orbits in progressively lower light condi ons. By extension, Pearce et al. (2013) hypothesize that because larger eyes necessitate larger visual cor ces, Neandertal brains were propor onately skewed more towards vision, and as a result Neandertals were cogni vely deficient compared with humans.
Uploads
Papers by Marc Meyer