Kristian J Carlson

University of Southern California | USC · Department of Integrative Anatomical Sciences

The ca. 3.67 Ma adult skeleton known as ‘Little Foot’ (StW 573), recovered from Sterkfontein Member 2 breccia in the Silberberg Grotto, is remarkable for its morphology and completeness. Preservation of clavicles and scapulae, including essentially complete right-side elements, offers opportunities to assess morphological and functional aspects of...

Late Middle Pleistocene hominins in Africa displaying key modern morphologies by 315 ka are claimed as the earliest Homo sapiens. Evolutionary relationships among East Asian hominins appear complex due to a growing fossil record of late Middle Pleistocene hominins from the region, reflecting mosaic morphologies that contribute to a lack of consensu...

Objectives: This study investigates patterns of bone functional adaptations in extant apes through comparing hindlimb to forelimb bone rigidity ratios in groups with varying levels of arboreality. Materials and methods: Using CT scans, bone rigidity (J) was calculated at three regions of interest (ROI) along femoral and humeral diaphyses in Homo...

The evolution of the medial longitudinal arch (MLA) is one of the most impactful adaptations in the hominin foot that emerged with bipedalism. When and how it evolved in the human lineage is still unresolved. Complicating the issue, clinical definitions of flatfoot in living Homo sapiens have not reached a consensus. Here we digitally investigate t...

Introduction The talus plays an important role in receiving and dissipating the forces and linking the leg and the foot. As such, it is of paramount importance to analyze how its morphology, internal and external, changes during late ontogeny and through adolescence. Method To explore both the external shape and the internal architecture of the ta...

The frontal sinuses are cavities inside the frontal bone located at the junction between the face and the cranial vault and close to the brain. Despite a long history of study, understanding of their origin and variation through evolution is limited. This work compares most hominin species’ holotypes and other key individuals with extant hominids....

In 2015, which marked 35 years since Beaumont had worked at the site, we renewed excavations at Border Cave. Our primary aims were to reassess the stratigraphic context of the sedimentary and cultural sequence, gain insight into site formation processes, make a detailed study of organic remains, identify long term cultural trends, and characterize...

Australopiths, a group of hominins from the Plio-Pleistocene of Africa, are characterized by derived traits in their crania hypothesized to strengthen the facial skeleton against feeding loads and increase the efficiency of bite force production. The crania of robust australopiths are further thought to be stronger and more efficient than those of...

Objective The Late Pleistocene partial right femur from Maludong in southwestern China has been attributed characteristics of early Homo , especially from the Early Pleistocene, putatively representing a late surviving archaic population in the region. Assessment of additional traits is warranted given newly described postcrania from the Late Pleis...

The fossiliferous deposits within the lower-lying Jacovec Cavern in the locality of Sterkfontein yielded valuable hominin remains, including the StW 578 specimen. Because StW 578 mainly preserves the calotte, the taxonomic status of this specimen has been a matter of discussion. Within this context, here we employed high-resolution microtomography...

Background: • All skeletal elements are composed of both cortical and trabecular bone. Most research on skeletal variation in humans and other primates has focused on analyzing only trabecular or cortical bone structure. However, these two levels of bone structural organization are known to have distinct material properties and likely respond diffe...

This project aims to test whether geometric morphometric (GM) and trabecular analyses may be useful tools in identifying talar characteristics related to hypochondroplasia. We quantified the external and internal talar morphology of an hypochondroplasic dwarf (T17) from Modena (northern Italy) dated to the 6th century AD. External talar morphology...

Neanderthal foot bone proportions and morphology are mostly indistinguishable from those of Homo sapiens, with the exception of several distinct Neanderthal features in the talus. The biomechanical implications of these distinct talar features remain contentious, fueling debate around the adaptive meaning of this distinctiveness. With the aim of cl...

The StW 573 skeleton of Australopithecus prometheus from Sterkfontein Member 2 is some 93% complete and thus by far the most complete member of that genus yet found. Firmly dated at 3.67 Ma, it is one of the earliest specimens of its genus. A crucial aspect of interpretation of locomotor behaviour from fossil remains is an understanding of the pala...

The Border Cave 3 (BC3) infant skeleton has been understudied, despite its importance as an example of a well-preserved and fairly complete immature skeleton of early Homo sapiens which potentially provides a rare window into various aspects of ontogenetic development, including locomotor activity (e.g., timing of gait events). Trabecular structure...

Objectives Variation in trabecular and cortical bone properties is often used to infer habitual behavior in the past. However, the structures of both types of bone are rarely considered together and may even contradict each other in functional interpretations. We examine trabecular and cortical bone properties in various athletes and sedentary cont...

Objectives Variation in human trabecular bone morphology can be linked to habitual behavior, but it is difficult to investigate in vivo due to the radiation required at high resolution. Consequently, functional interpretations of trabecular morphology remain inferential. Here we introduce a method to link low‐ and high‐resolution CT data from dry a...

Objectives: Aims of the study are to initially describe and comparatively evaluate the morphology of the new Zhaoguo M1 upper limb remains, and contextualize upper limb functional adaptations among those of other worldwide Upper Paleolithic (UP) humans to make inferences about subsistence-related activity patterns in southwestern China at the Plei...

The intertrochanteric line on the proximal human femur has been the focus of paleoanthropological study for several decades, as it is thought to be a defining characteristic of bipedalism. Expression of this trait is highly variable in human fossils. However, the relatively narrow range of modern human groups in which its expression has been docume...

The adoption of bipedalism is a key benchmark in human evolution that has impacted talar morphology. Here, we investigate talar morphological variability in extinct and extant hominins using a 3D geometric morphometric approach. The evolutionary timing and appearance of modern human–like features and their contributions to bipedal locomotion were e...

Analysis of the trabecular bone structure and midshaft cross-sectional geometry of the distal tibia of several groups of athletes and controls. Each loading modality is associated with a unique and predictable combination of trabecular and cortical bone variables. Our functional interpretations of fossil morphology can be improved by considering bo...

This chapter presents description and analysis of the Sterkfontein tibiae and fibulae, which have not previously been subjected to a careful systematic study. Among these elements, there is a clear range of variation expressed in several functionally relevant features. The distal tibia, StW 358, uniquely exhibits an absence of metaphyseal expansion...

Long bone diaphyseal cross-sectional geometries reflect the mechanical properties of the bones, and can be used to aid in inferences of locomotor behavior in extinct hominins. This chapter considers all available long bone diaphyseal and femoral neck cross-sections of specimens from Sterkfontein Member 4, and presents comparisons of these section p...

This chapter describes 12 tarsal bones from Sterkfontein, and compares them to those of extant hominoids and other fossil hominins, adding new analyses for some of the bones which have been studied previously. In general, the Sterkfontein calcanei and tali more closely resemble those attributed to Australopithecus sediba from nearby Malapa than to...

Functional morphology of the atlas reflects multiple aspects of an organism’s biology. More specifically, its shape indicates patterns of head mobility, while the size of its vascular foramina reflects blood flow to the brain. Anatomy and function of the early hominin atlas, and thus, its evolutionary history, are poorly documented because of a pau...

Objectives: This study examines long bone diaphyseal rigidity and shape of hunter-gatherers at Roonka to make inferences about subsistence strategies and mobility of inhabitants of semi-arid southeastern Australia. Roonka is a cemetery site adjacent to the Lower Murray River, which contains over 200 individuals buried throughout the Holocene. Arch...

Objectives: The primate talus is known to have a shape that varies according to differences in locomotion and substrate use. While the modern human talus is morphologically specialized for bipedal walking, relatively little is known on how its morphology varies in relation to cultural and environmental differences across time. Here we compare tali...

Due to its completeness, the A.L. 288-1 (‘Lucy’) skeleton has long served as the archetypal bipedal Australopithecus. However, there remains considerable debate about its limb proportions. There are three competing, but not necessarily mutually exclusive, explanations for the high humerofemoral index of A.L. 288-1: (1) a retention of proportions fr...

Design for manufacture and assembly is a critical step in the product design life cycle. In this study, design for manufacture and assembly theory was applied to the design of a polycentric paediatric prosthetic knee to resolve assembly and manufacture issues prior to product prototyping. Assembly time and efficiency prior and subsequent to design...

Modern humans have relatively lightly built skeletons compared to other primates and earlier hominins which may predispose recent humans to bone‐related health risks such as osteopenia and osteoporosis. Although recent work suggests a relationship between higher activity/mobility and increased postcranial trabecular bone structure, the amount of va...

The bones of the pectoral girdle and upper limb are well represented among the fossils thus far recovered from Malapa (Gauteng Province, South Africa). Malapa Hominin 2, a partial skeleton representing an adult female of Australopithecus sediba, preserves a largely complete right pectoral girdle and upper limb, including the most complete scapula y...

While the timing, duration, and nature of the shift is debated, human evolution ultimately involved an increase in body size relative to our Miocene ancestors, and a transition from a more arboreal to a more terrestrial way of life. This is reflected not only in the articular and muscular attachment morphology of the upper and lower limbs, but also...

One of the most crucial debates in human paleoneurology concerns the timing and mode of the emergence of the derived cerebral features in the hominin fossil record. Given its exceptional degree of preservation and geological age (i.e., 3.67 Ma), StW 573 (‘Little Foot’) has the potential to shed new light on hominin brain evolution. Here we present...

Due to its completeness, the A.L. 288-1 (Lucy) skeleton has long served as the archetypal bipedal Australopithecus . However, there remains considerable debate about its limb proportions. There are three competing, but not necessarily mutually exclusive, explanations for the high humerofemoral index of A.L. 288-1: (1) a retention of proportions fro...

When measured as a ratio of mean midshaft diameter to bone length, the OH 8 fossil hominin foot exhibits a metatarsal (Mt) robusticity pattern of 1 > 5 > 3 > 4 > 2, which differs from the widely perceived "common" modern human pattern (1 > 5 > 4 > 3 > 2); African apes generally exhibit a third pattern (1 > 2 > 3 > 4 > 5). Largely because of the rel...

The Sterkfontein Caves site is one of the richest early hominin fossil localities in Africa. More specifically, the fossiliferous deposits within the lower-lying Jacovec Cavern have yielded valuable hominin remains; prominent among them is the Australopithecus partial cranium StW 578. Due to the fragmentary nature of the braincase, the specimen has...

The Sterkfontein Caves site is one of the richest early hominid fossil localities in Africa. The fossiliferous deposits within the lower-lying Jacovec Cavern yielded valuable hominid remains, prominent among them is the Australopithecus partial cranium StW 578. Due to the fragmentary nature of the braincase, the specimen has not yet been formally a...

The bow and arrow is thought to be a unique development of our species, signalling higher-level cognitive functioning. How this technology originated and how we identify archaeological evidence for it are subjects of ongoing debate. Recent analysis of the putative bone arrow point from Sibudu Cave in South Africa, dated to 61.7±1.5kya, has provided...

Adaptations indicative of habitual bipedalism are present in the earliest recognized hominins. However, debate persists about various aspects of bipedal locomotor behavior in fossil hominins, including the nature of gait kinematics, locomotor variability across different species, and the degree to which various australopith species engaged in arbor...

Background Regional diversity in the morphology of the H. erectus postcranium is not broadly documented, in part, because of the paucity of Asian sites preserving postcranial fossils. Yet, such an understanding of the initial hominin taxon to spread throughout multiple regions of the world is fundamental to documenting the adaptive responses to sel...

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Regions of denser subchondral bone deep to a joint's articular surface indicate locations where the joint experiences relatively higher or more frequent compressive trans-articular forces than less dense regions. Human clinically-focused studies have hypothesized that regional variation of highest radiodensity (HiRD), acquired with computed tomogra...

StW 352, from Sterkfontein Member 4 (South Africa), is a partial calcaneus attributed to Australopithecus africanus and is dated to ~2.0–2.6 Ma. The unusual robusticity of the peroneal trochlea (PT) of StW 352 has been commented on by several authors. The size of hominin PTs has been hypothesised to be positively correlated with the degree of recru...

Dental root fractures are rarely documented in past human populations, but when they are observed, diagnosing ante-mortem events as causal factors can be difficult due to postmortem alteration. Can high resolution X-ray computed tomography (CT) improve our ability to diagnose if a dental fracture was caused ante- or post-mortem? To test this, a cas...

Tali of several hominin taxa are preserved in the fossil record and studies of the external morphology of these often show a mosaic of human-like and ape-like features. This has contributed to a growing recognition of variability characterizing locomotor kinematics of Australopithecus. In contrast, locomotor kinematics of another Plio-Pleistocene h...

Our results demonstrate that human shape tali are influenced by loading difference, presumably due to a combination of substrate used, lifestyles (nomadic vs. sedentary) and subsistence, resulting in different arthrokinematics in relation to how body weight is borne on the talus over the course of stance phase.

Australopiths exhibit a number of derived facial features that are thought to strengthen the face against high and/or repetitive loads associated with a diet that included mechanically challenging foods. Here, we use finite element analysis (FEA) to test hypotheses related to the purported strengthening role of the zygomatic root and “anterior pill...

Humans, unlike African apes, have relatively robust fifth metatarsals (Mt5) presumably reflecting substantial weight-bearing and stability function in the lateral column of the former. When this morphological difference emerged during hominin evolution is debated. Here we investigate internal diaphyseal structure of Mt5s attributed to Australopithe...

Fossils attributed to Australopithecus sediba are described as having phylogenetic affinities with early Homo to the exclusion of other South African australopiths. With respect to functional anatomy of mastication, one implication of this hypothesis is that A. sediba mandibles should exhibit absolutely and relatively reduced stiffness and strength...

Australopithecus africanus has been interpreted as having a rigid lateral foot. One mechanism contributing to a rigid foot during push-off in humans is a calcaneocuboid joint (CCJ) with limited dorsiflexion and a " close-packed " talocalcaneal joint (TCJ). In contrast, apes likely have a greater CCJ range of motion and lack a close-packed TCJ. Diff...

The type specimen of Australopithecus sediba (MH1) is a late juvenile, prompting some commentators to suggest that had it lived to adulthood its morphology would have changed sufficiently so as to render hypotheses regarding its phylogenetic relations suspect. Considering the potentially critical position of this species with regard to the origins...

During the Quaternary, the hominin evolutionary tree can be best characterised as bushy. Fossil discoveries in recent decades have shown that different hominin taxa co-existed more than was previously thought when Homo habilis was first deemed the earliest member of genus Homo. Such phylogenetic complexity at the origin of Homo is indicative of an...

Studies attempting to discriminate activity patterns via subchondral and trabecular bone in primates have exhibited varying levels of success. Many of these studies examined trabecular bone properties in one or multiple VOIs deep to the joint surface, with some displaying promising signals. This study aims to examine subchondral and trabecular bone...

Functional differentiation between the upper and lower limbs of hominins and other primates is commonly reflected in relative limb bone lengths. Additionally, analyses of the cross-sectional properties (CSPs) of limb bone mid-shafts may reflect functional differences in locomotion between species and permit inferences about early hominin locomotor...

Australopithecus sediba has been hypothesized to be a close relative of the genus Homo. Here we show that MH1, the type specimen of A. sediba, was not optimized to produce high molar bite force and appears to have been limited in its ability to consume foods that were mechanically challenging to eat. Dental microwear data have previously been inter...

Supplementary Figures 1-6, Supplementary Tables 1-4 and Supplementary Reference

The material selection of prostheses in developing countries is currently biased towards what is readily available and ignores important criteria such as patient comfort and structural strength. In this study, the ELECTRE III multiple attribute decision-making method was applied to the material selection of a paediatric prosthetic knee. Light metal...

Therapsids were severely affected by the Permian-Triassic mass extinction event and only a few lineages were able to survive. One of the main behavioural responses that may have aided in Therapsid survival across the extinction was fossorialism. Several fossilized skeletons of the non-mammaliaform cynodont, Thrinaxodon were found in curled up posit...

The zygomatic region and lateral orbital wall are important structural components of the primate craniofacial skeleton, providing attachment for muscles, housing and protecting the eye, and resisting and transmitting forces incurred during feeding and fighting. The design of this region must therefore meet the needs of a number of different functio...

While an avian component within faunal remains from the Dart Deposits, Taung, South Africa, has been discussed for nearly a century, the taxa present have not been identified to species. Here we conduct a systematic analysis of fossilized eggshell fragments in order to document the presence of specific avian taxa at Taung during the Plio-Pleistocen...

Significance The human skeleton is unique in having low trabecular density representing a lightly built human body form. However, it remains unknown when during human evolution this unique characteristic first appeared. To our knowledge, this study is the first to examine trabecular bone density throughout the skeleton of fossil hominins spanning s...

Diaphyseal morphology of long bones, in part, reflects in vivo loads experienced during the lifetime of an individual. The first metatarsal, as a cornerstone structure of the foot, presumably expresses diaphyseal morphology that reflects loading history of the foot during stance phase of gait. Human feet differ substantially from those of other ape...

Assembles a collection of experts to provide a current account of different approaches (e.g., traditional, comparative and experimental) being applied to study mobility. Moreover, the book aims to stimulate new theoretical perspectives that adopt a holistic view of the interaction among intrinsic (i.e. skeletal) and extrinsic (i.e. environmental) f...

Significance The Taung Child ( Australopithecus africanus ) has historical and scientific importance in the fossil record as the first and best example of early hominin brain evolution. It was recently proposed that Taung exhibits adaptive morphology (e.g., persistent metopic suture and open anterior fontanelle), permitting important postnatal brai...