The functional anatomy of the hominin foot has played a crucial role in studies of locomotor evolution in human ancestors and extinct relatives. However, foot fossils are rare, often isolated, and ...fragmentary. Here, we describe a complete hominin second metatarsal (StW 89) from the 2.0–2.6 million year old deposits of Member 4, Sterkfontein Cave, South Africa. Like many other fossil foot bones, it displays a mosaic of derived human-like features and primitive ape-like features. StW 89 possesses a domed metatarsal head with a prominent sulcus, indicating dorsiflexion at the metatarsophalangeal joint during bipedal walking. However, while the range of motion at the metatarsophalangeal joint is human-like in dorsiflexion, it is ape-like in plantarflexion. Furthermore, StW 89 possesses internal torsion of the head, an anatomy decidedly unlike that found in humans today. Unlike other hominin second metatarsals, StW 89 has a dorsoplantarly gracile base, perhaps suggesting more midfoot laxity. In these latter two anatomies, the StW 89 second metatarsal is quite similar to the recently described second metatarsal of the partial foot from Burtele, Ethiopia. We interpret this combination of anatomies as evidence for a low medial longitudinal arch in a foot engaged in both bipedal locomotion, but also some degree of pedal, and perhaps even hallucal, grasping. Additional fossil evidence will be required to determine if differences between this bone and other second metatarsals from Sterkfontein reflect normal variation in an evolving lineage, or taxonomic diversity.
The abundant femoral assemblage of Homo naledi found in the Dinaledi Chamber provides a unique opportunity to test hypotheses regarding the taxonomy, locomotion, and loading patterns of this species. ...Here we describe neck and shaft cross-sectional structure of all the femoral fossils recovered in the Dinaledi Chamber and compare them to a broad sample of fossil hominins, recent humans, and extant apes. Cross-sectional geometric (CSG) properties from the femoral neck (base of neck and midneck) and diaphysis (subtrochanteric region and midshaft) were obtained through CT scans for H. naledi and through CT scans or from the literature for the comparative sample. The comparison of CSG properties of H. naledi and the comparative samples shows that H. naledi femoral neck is quite derived with low superoinferior cortical thickness ratio and high relative cortical area. The neck appears superoinferiorly elongated because of two bony pilasters on its superior surface. Homo naledi femoral shaft shows a relatively thick cortex compared to the other hominins. The subtrochanteric region of the diaphysis is mediolaterally elongated resembling early hominins while the midshaft is anteroposteriorly elongated, indicating high mobility levels. In term of diaphyseal robusticity, the H. naledi femur is more gracile that other hominins and most apes. Homo naledi shows a unique combination of characteristics in its femur that undoubtedly indicate a species committed to terrestrial bipedalism but with a unique loading pattern of the femur possibly consequence of the unique postcranial anatomy of the species.
The “negrito” and African “pygmy” phenotypes are predominately exhibited by hunter-gatherers living in rainforest habitats. Foraging within such habitats is associated with a unique set of locomotor ...behaviors, most notably habitual vertical climbing during the pursuit of honey, fruit, and game. When performed frequently, this behavior is expected to correlate with developmentally plastic skeletal morphologies that respond to mechanical loading. Using six measurements in the distal tibia and talus that discriminate nonhuman primates by vertical climbing frequency, we tested the prediction that intraspecific variation in this behavior is reflected in the morphology of the ankle joint of habitually climbing human populations. First, to explore the plasticity of climbing-linked morphologies, we made comparisons between chimpanzees, gorillas, and orangutans from wild and captive settings. The analysis revealed significant differences in two climbing-linked traits (anterior expansion of the articular surface of the distal tibia and increased degree of talar wedging), indicating that these traits are sensitive to climbing behavior. However, our analyses did not reveal any signatures of climbing behavior in the ankles of habitually climbing hunter-gatherers. These results suggest that the detection of fine-grained differences in human locomotor behaviors at the ankle joint, particularly those associated with arboreality, may be obscured by the functional demands of terrestrial bipedalism. Accordingly, it may be difficult to use population-level characteristics of ankle morphology to make inferences about the climbing behavior of hominins in the fossil record, even when facultative arborealism is associated with key fitness benefits.
Morphology of the Homo naledi femora from Lesedi Walker, Christopher S.; Cofran, Zachary D.; Grabowski, Mark ...
American journal of physical anthropology,
September 2019, 2019-09-00, 20190901, Letnik:
170, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Objectives
The femoral remains recovered from the Lesedi Chamber are among the most complete South African fossil hominin femora discovered to date and offer new and valuable insights into the ...anatomy and variation of the bone in Homo naledi. While the femur is one of the best represented postcranial elements in the H. naledi assemblage from the Dinaledi Chamber, the fragmentary and commingled nature of the Dinaledi femoral remains has impeded the assessment of this element in its complete state.
Materials and methods
Here we analyze and provide descriptions of three new relatively well‐preserved femoral specimens of H. naledi from the Lesedi Chamber: U.W. 102a‐001, U.W. 102a‐003, and U.W. 102a‐004. These femora are quantitatively and qualitatively compared to multiple extinct hominin femoral specimens, extant hominid taxa, and, where possible, each other.
Results
The Lesedi femora are morphologically similar to the Dinaledi femora for all overlapping regions, with differences limited to few traits of presently unknown significance. The Lesedi distal femur and mid‐diaphysis preserve anatomy previously unidentified or unconfirmed in the species, including an anteroposteriorly expanded midshaft and anteriorly expanded patellar surface. The hypothesis that the Lesedi femoral sample may represent two individuals is supported.
Discussion
The Lesedi femora increase the range of variation of femoral morphology in H. naledi. Newly described features of the diaphysis and distal femur are either taxonomically uninformative or Homo‐like. Overall, these three new femora are consistent with previous functional interpretations of the H. naledi lower limb as belonging to a species adapted for long distance walking and, possibly, running.
Walking mechanics are influenced by body morphology. Foot arch height is one aspect of body morphology central to walking. However, generalizations about the relationship between arch height and ...walking are limited due to previous methodologies used for measuring the arch and the populations that have been studied. To gain the knowledge needed to support healthy gait in children and adults, we need to understand this relationship in unimpaired, typically developing children and adults using dynamic measures. The purpose of the current study was to examine the relationship between arch height and gait in a sample of healthy children and adults using dynamic measures.
Data were collected from 638 participants (n = 254 children and n = 384 adults) at the Museum of Science, Boston (MOS) and from 18 4- to 8-year-olds at the Motor Development and Motor Control Laboratories. Digital footprints were used to calculate two arch indices: the Chippaux-Smirak (CSI) and the Keimig Indices (KI). The height of the navicular bone was measured. Gait parameters were captured with a mechanized gait carpet at the MOS and three-dimensional motion analyses and in-ground force plates in the Motor Development and Motor Control Laboratories.
Linear regression analyses on data from the MOS confirmed that as age increases, step length increases. With a linear mixed effect regression model, we found that individuals who took longer steps had higher arches as measured by the KI. However, this relationship was no longer significant when only adults were included in the model. A model restricted to children found that amongst this sample, those with higher CSI and higher KI values take longer relative step lengths. Data from the Motor Development and Motor Control Laboratories showed that both CSI and KI added to the prediction; children with lower anterior ground reaction forces had higher CSI and higher KI values. Arch height indices were correlated with navicular height.
These results suggest that more than one measure of the arch may be needed elucidate the relationship between arch height and gait.
Abstract The accurate measurement of tissue mineral density, ρm , in specimens of unequal size or quantities of bone mineral using polychromatic μCT systems is important, since studies often compare ...samples with a range of sizes and bone densities. We assessed the influence of object size on μCT measurements of ρm using (1) hydroxyapatite rods (HA), (2) precision-manufactured aluminum foams (AL) simulating trabecular bone structure, and (3) bovine cortical bone cubes (BCt). Two beam-hardening correction (BHC) algorithms, determined using a 200 and 1200 mg/cm3 HA wedge phantom, were used to calculate ρm of the HA and BCt. The 200 mg/cm3 and an aluminum BHC algorithm were used to calculate the linear attenuation coefficients of the AL foams. Equivalent ρm measurements of 500, 1000, and 1500 mg HA/cm3 rods decreased ( r2 > 0.96, p < 0.05 for all) as HA rod diameter increased in the 200 mg/cm3 BHC data. Errors averaged 8.2% across these samples and reached as high as 29.5%. Regression analyses suggested no size effects in the 1200 mg/cm3 BHC data but differences between successive sizes still reached as high as 13%. The linear attenuation coefficients of the AL foams increased up to approximately 6% with increasing volume fractions ( r2 > 0.81, p < 0.05 for all) but the strength of the size-related error was also BHC dependent. Equivalent ρm values were inversely correlated with BCt cube size ( r2 > 0.92, p < 0.05). Use of the 1200 mg/cm3 BHC ameliorated the size-related artifact compared to the 200 mg/cm3 BHC but errors with this BHC were still significant and ranged between 5% and 12%. These results demonstrate that object size, structure, and BHC algorithm can influence μCT measurements of ρm . Measurements of ρm of specimens of unequal size or quantities of bone mineral must be interpreted with caution unless appropriate steps are taken to minimize these potential artifacts.
Abstract Home runs in baseball—fair balls hit out of the field of play—have risen since 1980, driving strategic shifts in gameplay. Myriad factors likely account for these trends, with some ...speculating that global warming has contributed via a reduction in ballpark air density. Here we use observations from 100,000 Major League Baseball games and 240,000 individual batted balls to show that higher temperatures substantially increase home runs. We isolate human-caused warming with climate models, finding that >500 home runs since 2010 are attributable to historical warming. Several hundred additional home runs per season are projected due to future warming. Adaptations such as building domes on stadiums or shifting day games to night games reduce temperature’s effects on America’s pastime. Our results highlight the myriad ways that a warmer planet will restructure our lives, livelihoods, and recreation, some quantifiable and easily adapted to, as shown here, many others, not.
Funding agencies and institutions are creating initiatives to encourage interdisciplinary research that can be more easily translated into community initiatives to enhance health. Therefore, the ...current research environment calls for interdisciplinary education and skills to create sustained partnerships with community institutions. However, formalized opportunities in both of these areas are limited for students embarking on research careers. The purpose of this paper is to underscore the historical and current importance of providing interdisciplinary training and community dissemination for research students. We also suggest an approach to begin to address the existing gap. Specifically, we suggest embedding a 10‐week summer rotation into existing research curricula with the goals of: (1) providing students with a hands‐on interdisciplinary research experience, (2) facilitating dialogue between research students and community settings to disseminate science to the public, and (3) sparking collaborations among researchers who seek to create a way to sustain summer program rotations with grant funding.
PDF
