Many aspects of limb function, including strength and fatigue resistance, are determined by muscl... more Many aspects of limb function, including strength and fatigue resistance, are determined by muscle dimensions. Reconstructions of fossil hominin locomotor abilties are hampered by a lack of reliable methods for estimating muscle dimensions from skeletal elements. Here, we test whether the patella, a sesamoid bone of the quadriceps complex tendon, is a reliable indicator of physiological cross-sectional area of the quadriceps muscle group. We examined the relationship between linear dimensions of the patella and the physiological cross-sectional area (PCSA) of the quadriceps muscle complex in hominoids (Hylobates, Nomascus, Symphalangus, Pongo, Gorilla, Pan, and Homo), a strepsirhine (Lemur fulvus), a common European rabbit (Oryctolagus cuniculus), and a common housecat (Felis catus). We calculated patellar cross-sectional area in two planes: sagittal (the product of anterior-posterior thickness and superior-inferior height), and transverse (the product of anterior-posterior thickness and mediolateral width). Both the sagittal plane cross-sectional area (SCSA) and the transverse plane cross-sectional area (TCSA) were significantly correlated with the PCSA of the quadriceps complex (P<0.001 for both; r²=0.99, 0.97 respectively), independent of osteological indices of body size (e.g., femoral head dimensions). These relationships across the primate and greater mammalian sample provide a new approach for reconstructing locomotor performance and ecology in extinct taxa where the patella is preserved. Estimates of fossil hominin PCSA from the SCSA and TSCA regressions suggest an increase in quadriceps size beginning in the genus Homo.
The morphology and positional behavior of the last common ancestor of humans and chimpanzees are ... more The morphology and positional behavior of the last common ancestor of humans and chimpanzees are critical for understanding the evolution of bipedalism. Early 20th century anatomical research supported the view that humans evolved from a suspensory ancestor bearing some resemblance to apes. However, the hand of the 4.4 million-year-old hominin Ardipithecus ramidus, purportedly provides evidence that the hominin hand was derived from a more generalized form. Here we use morphometric and phylogenetic comparative methods to show that Ardipithecus retains suspensory adapted hand morphologies shared with chimpanzees and bonobos. We identify an evolutionary shift in hand morphology between Ardipithecus and Australopithecus that renews questions about the coevolution of hominin manipulative capabilities and obligate bipedalism initially proposed by Darwin. Overall, our results suggest that early hominins evolved from an ancestor with a varied positional repertoire including suspension and ...
Geometrically complex anatomical regions are difficult to represent in 2D images presented to stu... more Geometrically complex anatomical regions are difficult to represent in 2D images presented to students in lecture slides and reference texts. This problem has been traditionally mitigated by interactions with cadaveric specimens or other 3D anatomical models. However, given a recent trend away from cadaver-based anatomy education and exasperated by remote teaching in response to the COVID-19 pandemic, student access to more interactive means of learning have been limited. In response to these issues, we have created an immersive, web-based tour of the heart using the Mozilla Hubs platform. A 3D model of a human heart displaying all internal features, coronary arteries, and great vessels was developed into a virtual space to serve as a digital classroom. To supplement the morphology of the heart, additional informational panels, structure labels, and pathways through the heart were added. Students choose an avatar and navigate using keyboard commands reminiscent of PC and web-based g...
The suspensory hand of Ardipithecus untangles the relationship between bipedalism and stone tool ... more The suspensory hand of Ardipithecus untangles the relationship between bipedalism and stone tool use in human evolution.
Body size is highly variable among modern human populations, as it is influenced by the interacti... more Body size is highly variable among modern human populations, as it is influenced by the interactions between genetic information and external nutritional and environmental variables during growth. Across traditional societies a relationship between life history strategy, relative adult body size, and extrinsic variables (e.g. ecology, subsistence strategies) has been documented and serves as a theoretical foundation to explain observed variability. However, individual populations are known to deviate from this pattern. Cross-sectional data on height and weight were taken from an ontogenetic sample of Daasanach individuals (n=223) from Ileret, Kenya to test the null hypothesis that the Daasanach conform to the expected growth timings and adult body size parameters for traditional populations of similar ecologies and subsistence strategies. Mean adult male body size was compiled from twenty previously studied traditional societies among which stature differed significantly among ecolo...
ABSTRACT It has been suggested that megadont mandibular premolars in fossil hominins is an adapta... more ABSTRACT It has been suggested that megadont mandibular premolars in fossil hominins is an adaptation for the consumption of mechanically challenging food items. This study used an extant primate model to test the hypothesis that megadont premolars correlate with diets that are especially hard or tough. We investigated several mixed-sex groups of closely-related, sympatric primates (e.g., Callimico-Saguinus, Cebus sp., Cercocebus-Lophocebus, Hylobates-Pongo, Macaca sp., Papio-Theropithecus). Although there is significant overlap in the dietary items these sympatric primates consume, they differ in their mandibular postcanine morphology. Standard metric and 2D geometric morphometric analyses were conducted on the mandibular postcanines of these taxa in the collection of the NMNH. Even when the effects of differences in body size are taken into account, relative premolar size is significantly and consistently larger in taxa that consume harder diets than closely-related, sympatric taxa. Relative premolar size was not consistently larger in taxa that consume tougher diets than closely-related, sympatric taxa. These results indicate that relatively large P4 crown areas may be an adaptation that allows taxa to shift to diets with higher percentages of mechanically challenging food items, specifically hard food items. The results of this study have implications for reconstructing the dietary ecology of sympatric Paranthropus and early Homo and may be evidence of character displacement in the evolution of the postcanines of early hominins.
The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila mela... more The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have higher transposon density (25%-50%) than euchromatic reference regions (3%-11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% versus 11%-27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density ...
ABSTRACT Many aspects of limb function, including strength and fatigue resistance, are determined... more ABSTRACT Many aspects of limb function, including strength and fatigue resistance, are determined by muscle dimensions. Reconstructions of fossil hominin locomotor abilties are hampered by a lack of reliable methods for estimating muscle dimensions from skeletal elements. Here, we test whether the patella, a sesamoid bone of the quadriceps complex tendon, is a reliable indicator of physiological cross-sectional area of the quadriceps muscle group. We examined the relationship between linear dimensions of the patella and the physiological cross-sectional area (PCSA) of the quadriceps muscle complex in hominoids (Hylobates, Nomascus, Symphalangus, Pongo, Gorilla, Pan, and Homo), a strepsirhine (Lemur fulvus), a common European rabbit (Oryctolagus cuniculus), and a common housecat (Felis catus). We calculated patellar cross-sectional area in two planes: sagittal (the product of anterior-posterior thickness and superior-inferior height), and transverse (the product of anterior-posterior thickness and mediolateral width). Both the sagittal plane cross-sectional area (SCSA) and the transverse plane cross-sectional area (TCSA) were significantly correlated with the PCSA of the quadriceps complex (P&lt;0.001 for both; r²=0.99, 0.97 respectively), independent of osteological indices of body size (e.g., femoral head dimensions). These relationships across the primate and greater mammalian sample provide a new approach for reconstructing locomotor performance and ecology in extinct taxa where the patella is preserved. Estimates of fossil hominin PCSA from the SCSA and TSCA regressions suggest an increase in quadriceps size beginning in the genus Homo.
The morphology and positional behavior of the last common ancestor of humans and chimpanzees are ... more The morphology and positional behavior of the last common ancestor of humans and chimpanzees are critical for understanding the evolution of bipedalism. Early 20th century anatomical research supported the view that humans evolved from a suspensory ancestor bearing some resemblance to apes. However, the hand of the 4.4-million-year-old hominin Ardipithecus ramidus purportedly provides evidence that the hominin hand was derived from a more generalized form. Here, we use morphometric and phylogenetic comparative methods to show that Ardipithecus retains suspensory adapted hand morphologies shared with chimpanzees and bonobos. We identify an evolutionary shift in hand morphology between Ardipithecus and Australopithecus that renews questions about the coevolution of hominin manipulative capabilities and obligate bipedalism initially proposed by Darwin. Overall, our results suggest that early hominins evolved from an ancestor with a varied positional repertoire including suspension and ...
Many aspects of limb function, including strength and fatigue resistance, are determined by muscl... more Many aspects of limb function, including strength and fatigue resistance, are determined by muscle dimensions. Reconstructions of fossil hominin locomotor abilties are hampered by a lack of reliable methods for estimating muscle dimensions from skeletal elements. Here, we test whether the patella, a sesamoid bone of the quadriceps complex tendon, is a reliable indicator of physiological cross-sectional area of the quadriceps muscle group. We examined the relationship between linear dimensions of the patella and the physiological cross-sectional area (PCSA) of the quadriceps muscle complex in hominoids (Hylobates, Nomascus, Symphalangus, Pongo, Gorilla, Pan, and Homo), a strepsirhine (Lemur fulvus), a common European rabbit (Oryctolagus cuniculus), and a common housecat (Felis catus). We calculated patellar cross-sectional area in two planes: sagittal (the product of anterior-posterior thickness and superior-inferior height), and transverse (the product of anterior-posterior thickness and mediolateral width). Both the sagittal plane cross-sectional area (SCSA) and the transverse plane cross-sectional area (TCSA) were significantly correlated with the PCSA of the quadriceps complex (P<0.001 for both; r²=0.99, 0.97 respectively), independent of osteological indices of body size (e.g., femoral head dimensions). These relationships across the primate and greater mammalian sample provide a new approach for reconstructing locomotor performance and ecology in extinct taxa where the patella is preserved. Estimates of fossil hominin PCSA from the SCSA and TSCA regressions suggest an increase in quadriceps size beginning in the genus Homo.
The morphology and positional behavior of the last common ancestor of humans and chimpanzees are ... more The morphology and positional behavior of the last common ancestor of humans and chimpanzees are critical for understanding the evolution of bipedalism. Early 20th century anatomical research supported the view that humans evolved from a suspensory ancestor bearing some resemblance to apes. However, the hand of the 4.4 million-year-old hominin Ardipithecus ramidus, purportedly provides evidence that the hominin hand was derived from a more generalized form. Here we use morphometric and phylogenetic comparative methods to show that Ardipithecus retains suspensory adapted hand morphologies shared with chimpanzees and bonobos. We identify an evolutionary shift in hand morphology between Ardipithecus and Australopithecus that renews questions about the coevolution of hominin manipulative capabilities and obligate bipedalism initially proposed by Darwin. Overall, our results suggest that early hominins evolved from an ancestor with a varied positional repertoire including suspension and ...
Geometrically complex anatomical regions are difficult to represent in 2D images presented to stu... more Geometrically complex anatomical regions are difficult to represent in 2D images presented to students in lecture slides and reference texts. This problem has been traditionally mitigated by interactions with cadaveric specimens or other 3D anatomical models. However, given a recent trend away from cadaver-based anatomy education and exasperated by remote teaching in response to the COVID-19 pandemic, student access to more interactive means of learning have been limited. In response to these issues, we have created an immersive, web-based tour of the heart using the Mozilla Hubs platform. A 3D model of a human heart displaying all internal features, coronary arteries, and great vessels was developed into a virtual space to serve as a digital classroom. To supplement the morphology of the heart, additional informational panels, structure labels, and pathways through the heart were added. Students choose an avatar and navigate using keyboard commands reminiscent of PC and web-based g...
The suspensory hand of Ardipithecus untangles the relationship between bipedalism and stone tool ... more The suspensory hand of Ardipithecus untangles the relationship between bipedalism and stone tool use in human evolution.
Body size is highly variable among modern human populations, as it is influenced by the interacti... more Body size is highly variable among modern human populations, as it is influenced by the interactions between genetic information and external nutritional and environmental variables during growth. Across traditional societies a relationship between life history strategy, relative adult body size, and extrinsic variables (e.g. ecology, subsistence strategies) has been documented and serves as a theoretical foundation to explain observed variability. However, individual populations are known to deviate from this pattern. Cross-sectional data on height and weight were taken from an ontogenetic sample of Daasanach individuals (n=223) from Ileret, Kenya to test the null hypothesis that the Daasanach conform to the expected growth timings and adult body size parameters for traditional populations of similar ecologies and subsistence strategies. Mean adult male body size was compiled from twenty previously studied traditional societies among which stature differed significantly among ecolo...
ABSTRACT It has been suggested that megadont mandibular premolars in fossil hominins is an adapta... more ABSTRACT It has been suggested that megadont mandibular premolars in fossil hominins is an adaptation for the consumption of mechanically challenging food items. This study used an extant primate model to test the hypothesis that megadont premolars correlate with diets that are especially hard or tough. We investigated several mixed-sex groups of closely-related, sympatric primates (e.g., Callimico-Saguinus, Cebus sp., Cercocebus-Lophocebus, Hylobates-Pongo, Macaca sp., Papio-Theropithecus). Although there is significant overlap in the dietary items these sympatric primates consume, they differ in their mandibular postcanine morphology. Standard metric and 2D geometric morphometric analyses were conducted on the mandibular postcanines of these taxa in the collection of the NMNH. Even when the effects of differences in body size are taken into account, relative premolar size is significantly and consistently larger in taxa that consume harder diets than closely-related, sympatric taxa. Relative premolar size was not consistently larger in taxa that consume tougher diets than closely-related, sympatric taxa. These results indicate that relatively large P4 crown areas may be an adaptation that allows taxa to shift to diets with higher percentages of mechanically challenging food items, specifically hard food items. The results of this study have implications for reconstructing the dietary ecology of sympatric Paranthropus and early Homo and may be evidence of character displacement in the evolution of the postcanines of early hominins.
The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila mela... more The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have higher transposon density (25%-50%) than euchromatic reference regions (3%-11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% versus 11%-27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density ...
ABSTRACT Many aspects of limb function, including strength and fatigue resistance, are determined... more ABSTRACT Many aspects of limb function, including strength and fatigue resistance, are determined by muscle dimensions. Reconstructions of fossil hominin locomotor abilties are hampered by a lack of reliable methods for estimating muscle dimensions from skeletal elements. Here, we test whether the patella, a sesamoid bone of the quadriceps complex tendon, is a reliable indicator of physiological cross-sectional area of the quadriceps muscle group. We examined the relationship between linear dimensions of the patella and the physiological cross-sectional area (PCSA) of the quadriceps muscle complex in hominoids (Hylobates, Nomascus, Symphalangus, Pongo, Gorilla, Pan, and Homo), a strepsirhine (Lemur fulvus), a common European rabbit (Oryctolagus cuniculus), and a common housecat (Felis catus). We calculated patellar cross-sectional area in two planes: sagittal (the product of anterior-posterior thickness and superior-inferior height), and transverse (the product of anterior-posterior thickness and mediolateral width). Both the sagittal plane cross-sectional area (SCSA) and the transverse plane cross-sectional area (TCSA) were significantly correlated with the PCSA of the quadriceps complex (P&lt;0.001 for both; r²=0.99, 0.97 respectively), independent of osteological indices of body size (e.g., femoral head dimensions). These relationships across the primate and greater mammalian sample provide a new approach for reconstructing locomotor performance and ecology in extinct taxa where the patella is preserved. Estimates of fossil hominin PCSA from the SCSA and TSCA regressions suggest an increase in quadriceps size beginning in the genus Homo.
The morphology and positional behavior of the last common ancestor of humans and chimpanzees are ... more The morphology and positional behavior of the last common ancestor of humans and chimpanzees are critical for understanding the evolution of bipedalism. Early 20th century anatomical research supported the view that humans evolved from a suspensory ancestor bearing some resemblance to apes. However, the hand of the 4.4-million-year-old hominin Ardipithecus ramidus purportedly provides evidence that the hominin hand was derived from a more generalized form. Here, we use morphometric and phylogenetic comparative methods to show that Ardipithecus retains suspensory adapted hand morphologies shared with chimpanzees and bonobos. We identify an evolutionary shift in hand morphology between Ardipithecus and Australopithecus that renews questions about the coevolution of hominin manipulative capabilities and obligate bipedalism initially proposed by Darwin. Overall, our results suggest that early hominins evolved from an ancestor with a varied positional repertoire including suspension and ...
The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila mela... more The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have higher transposon density (25%-50%) than euchromatic reference regions (3%-11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% versus 11%-27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density ...
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