Reconstructing patterns of domestication in reindeer using 3D muscle attachment areas.

The use of reindeer has been a crucial element in the subsistence strategies of past Arctic and Subarctic populations. However, the spatiotemporal occurrence of systematic herding practices has been difficult to identify in the bioarchaeological record. To address this research gap, this study proposes a new virtual anthropological approach for reconstructing habitual physical activity in reindeer, relying on the protocols of the "Validated Entheses based Reconstruction of Activity" (VERA) method. Following blind analytical procedures, we focused on eight muscle attachment sites ("entheses") in 36 reindeer free ranging in the wild, 21 specimens in captivity (zoo), and eight racing reindeer (habitual runners). Importantly, our analyses accounted for the effects of variation by subspecies, sex, age, and estimated body size. Our results showed clear differences across activity groups, leading to the development of discriminant function equations with cross-validated accuracies ranging from approximately 88 to 100%. The reliability of our functions was additionally confirmed using a blind test involving six zoo individuals not included in the initial dataset. Our findings support the use of the proposed approach for identifying domestication-related activities in zooarchaeological contexts, introducing a valuable tool for locating suspected domestication hotspots and elucidating the nature of past human-reindeer interactions. Supplementary Information: The online version contains supplementary material available at 10.1007/s12520-023-01910-5.

Sexing the sternal rib end in modern Greeks: A virtual osteometric approach using high-resolution 3D surface models.

Sex determination is one of the first biological attribute to be assessed when unidentified remains surface. In material of forensic interest, being able to use every skeletal element available for identification purposes is of paramount importance. The osteometric method from the sternal rib end has been found to generate accurate sex estimates, but as various studies have proved, all osteometric methods should be population-specific, as one equation does not fit all. The aim of this study is to assess sexual dimorphism in a contemporary Greek population sample of 68 males and 43 females, with the use of discriminant function analysis. The superior-inferior height (SIH) and anterior-posterior breadth (APB) from the third to fifth sternal rib ends of both sides were taken from 3D models created with the use of a hand-held 3D scanner. The results demonstrated that SIH is more sexually dimorphic than APB (alpha value of .05) while the application of Iscan's (1985) formula on the contemporary Greek sample, provided results of low accuracy, ranging from 48.6-52.4%. The cross-validated discriminant functions equations for the current sample, produced results ranging between 74.0-82.9% indicating that population-specific formulas produce results of higher accuracy, that are vital in cases of forensic interest.

The Application of Bony Labyrinth Methods for Forensic Affinity Estimation.

Population affinity identification is important for reconstructing the biological profile of human skeletal remains. Most anthropological methods for predicting population affinity rely on complete crania or cranial parts. However, complete parts are frequently not found in forensic and bioarchaeological contexts. In contrast, the petrous portion of the cranium presents a unique rate of preservation in the field. Therefore, this study aimed to develop stepwise discriminant function formulae to determine population affinity using measurements on three-dimensional models of the human adult bony labyrinth. The sample utilised consisted of 30 German, 38 African Zulu, and 30 Oneota individuals. A total of four function equations were developed. The function involving all three populations presented an average accuracy of 90.8%. Mathematical equations were also derived to discriminate between Zulu and Germans (91.2%), Zulu and Oneota (95.5%), as well as Oneota and Germans (96.7%). These results indicate this new method of population affinity identification is highly successful, even with fragmentary remains.

Practical and technical aspects for the 3D scanning of lithic artefacts using micro-computed tomography techniques and laser light scanners for subsequent geometric morphometric analysis. Introducing the StyroStone protocol.

Here, we present a new method to scan a large number of lithic artefacts using three-dimensional scanning technology. Despite the rising use of high-resolution 3D surface scanners in archaeological sciences, no virtual studies have focused on the 3D digitization and analysis of small lithic implements such as bladelets, microblades, and microflakes. This is mostly due to difficulties in creating reliable 3D meshes of these artefacts resulting from several inherent features (i.e., size, translucency, and acute edge angles), which compromise the efficiency of structured light or laser scanners and photogrammetry. Our new protocol StyroStone addresses this problem by proposing a step-by-step procedure relying on the use of micro-computed tomographic technology, which is able to capture the 3D shape of small lithic implements in high detail. We tested a system that enables us to scan hundreds of artefacts together at once within a single scanning session lasting a few hours. As also bigger lithic artefacts (i.e., blades) are present in our sample, this protocol is complemented by a short guide on how to effectively scan such artefacts using a structured light scanner (Artec Space Spider). Furthermore, we estimate the accuracy of our scanning protocol using principal component analysis of 3D Procrustes shape coordinates on a sample of meshes of bladelets obtained with both micro-computed tomography and another scanning device (i.e., Artec Micro). A comprehensive review on the use of 3D geometric morphometrics in lithic analysis and other computer-based approaches is provided in the introductory chapter to show the advantages of improving 3D scanning protocols and increasing the digitization of our prehistoric human heritage.

Effects of selective breeding for voluntary exercise, chronic exercise, and their interaction on muscle attachment site morphology in house mice.

Skeletal muscles attach to bone at their origins and insertions, and the interface where tendon meets bone is termed the attachment site or enthesis. Mechanical stresses at the muscle/tendon-bone interface are proportional to the surface area of the bony attachment sites, such that a larger attachment site will distribute loads over a wider area. Muscles that are frequently active and/or are of larger size should cause attachment sites to hypertrophy (training effect); however, experimental studies of animals subjected to exercise have provided mixed results. To enhance our ability to detect training effects (a type of phenotypic plasticity), we studied a mouse model in which 4 replicate lines of High Runner (HR) mice have been selectively bred for 57 generations. Selection is based on the average number of wheel revolutions on days 5 & 6 of a 6-day period of wheel access as young adults (6-8 weeks old). Four additional lines are bred without regard to running and serve as non-selected controls (C). On average, mice from HR lines voluntarily run ~3 times more than C mice on a daily basis. For this study, we housed 50 females (half HR, half C) with wheels (Active group) and 50 (half HR, half C) without wheels (Sedentary group) for 12 weeks starting at weaning (~3 weeks old). We tested for evolved differences in muscle attachment site surface area between HR and C mice, plastic changes resulting from chronic exercise, and their interaction. We used a precise, highly repeatable method for quantifying the three-dimensional (3D) surface area of four muscle attachment sites: the humerus deltoid tuberosity (the insertion point for the spinodeltoideus, superficial pectoralis, and acromiodeltoideus), the femoral third trochanter (the insertion point for the quadratus femoris), the femoral lesser trochanter (the insertion point for the iliacus muscle), and the femoral greater trochanter (insertion point for the middle gluteal muscles). In univariate analyses, with body mass as a covariate, mice in the Active group had significantly larger humerus deltoid tuberosities than Sedentary mice, with no significant difference between HR and C mice and no interaction between exercise treatment and linetype. These differences between Active and Sedentary mice were also apparent in the multivariate analyses. Surface areas of the femoral third trochanter, femoral lesser trochanter, and femoral greater trochanter were unaffected by either chronic wheel access or selective breeding. Our results, which used robust measurement protocols and relatively large sample sizes, demonstrate that muscle attachment site morphology can be (but is not always) affected by chronic exercise experienced during ontogeny. However, contrary to previous results for other aspects of long bone morphology, we did not find evidence for evolutionary coadaptation of muscle attachments with voluntary exercise behavior in the HR mice.

Accurate and semi-automated reassociation of intermixed human skeletal remains recovered from bioarchaeological and forensic contexts.

Commingled remains describes the situation of intermixed skeletal elements, an extremely common occurrence in contemporary forensic cases, archaeological mass graves, as well as fossil hominin assemblages. Given that reliable identification is typically impossible for commingled contexts, a plethora of previous studies has focused on the development of refined methods for reassociating the bones of each individual skeleton. Here, a novel virtual approach for quantifying the degree of three-dimensional shape compatibility between two adjoining bone articular surfaces is put forth. Additionally, the integrability of this method with traditional osteometric techniques is evaluated. We focus on the paradigm of the hip joint, whose articulating bone elements (the femur and the innominate bone) are crucial for reconstructing the biological profile of unidentified human remains. The results demonstrate that this new semi-automated methodology is highly accurate both for large commingled assemblages (such as those resulting from mass disasters or burials) as well as smaller-scale contexts (such as those resulting from secondary burials).

New horizons in reconstructing past human behavior: Introducing the "Tübingen University Validated Entheses-based Reconstruction of Activity" method.

An accurate reconstruction of habitual activities in past populations and extinct hominin species is a paramount goal of paleoanthropological research, as it can elucidate the evolution of human behavior and the relationship between culture and biology. Variation in muscle attachment (entheseal) morphology has been considered an indicator of habitual activity, and many attempts have been made to use it for this purpose. However, its interpretation remains equivocal due to methodological shortcomings and a paucity of supportive experimental data. Through a series of studies, we have introduced a novel and precise methodology that focuses on reconstructing muscle synergies based on three-dimensional and multivariate analyses among entheses. This approach was validated using uniquely documented anthropological samples, experimental animal studies, histological observations, and geometric morphometrics. Here, we detail, synthesize, and critically discuss the findings of these studies, which overall point to the great potential of entheses in elucidating aspects of past human behavior.

Biomechanics of the human thumb and the evolution of dexterity.

Systematic tool production and use is one of humanity's defining characteristics, possibly originating as early as >3 million years ago.1-3 Although heightened manual dexterity is considered to be intrinsically intertwined with tool use and manufacture, and critical for human evolution, its role in the emergence of early culture remains unclear. Most previous research on this question exclusively relied on direct morphological comparisons between early hominin and modern human skeletal elements, assuming that the degree of a species' dexterity depends on its similarity with the modern human form. Here, we develop a new approach to investigate the efficiency of thumb opposition, a fundamental component of manual dexterity, in several species of fossil hominins. Our work for the first time takes into account soft tissue as well as bone anatomy, integrating virtual modeling of musculus opponens pollicis and its interaction with three-dimensional bone shape form. Results indicate that a fundamental aspect of efficient thumb opposition appeared approximately 2 million years ago, possibly associated with our own genus Homo, and did not characterize Australopithecus, the earliest proposed stone tool maker. This was true also of the late Australopithecus species, Australopithecus sediba, previously found to exhibit human-like thumb proportions. In contrast, later Homo species, including the small-brained Homo naledi, show high levels of thumb opposition dexterity, highlighting the increasing importance of cultural processes and manual dexterity in later human evolution.

Biocultural evidence of precise manual activities in an Early Holocene individual of the high-altitude Peruvian Andes.

OBJECTIVES: Cuncaicha, a rockshelter site in the southern Peruvian Andes, has yielded archaeological evidence for human occupation at high elevation (4,480 masl) during the Terminal Pleistocene (12,500-11,200 cal BP), Early Holocene (9,500-9,000 cal BP), and later periods. One of the excavated human burials (Feature 15-06), corresponding to a middle-aged female dated to ~8,500 cal BP, exhibits skeletal osteoarthritic lesions previously proposed to reflect habitual loading and specialized crafting labor. Three small tools found in association with this burial are hypothesized to be associated with precise manual dexterity. MATERIALS AND METHODS: Here, we tested this functional hypothesis through the application of a novel multivariate methodology for the three-dimensional analysis of muscle attachment surfaces (entheses). This original approach has been recently validated on both lifelong-documented anthropological samples as well as experimental studies in nonhuman laboratory samples. Additionally, we analyzed the three-dimensional entheseal shape and resulting moment arms for muscle opponens pollicis. RESULTS: Results show that Cuncaicha individual 15-06 shows a distinctive entheseal pattern associated with habitual precision grasping via thumb-index finger coordination, which is shared exclusively with documented long-term precision workers from recent historical collections. The separate geometric morphometric analysis revealed that the individual's opponens pollicis enthesis presents a highly projecting morphology, which was found to strongly correlate with long joint moment arms (a fundamental component of force-producing capacity), closely resembling the form of Paleolithic hunter-gatherers from diverse geo-chronological contexts of Eurasia and North Africa. DISCUSSION: Overall, our findings provide the first biocultural evidence to confirm that the lifestyle of some of the earliest Andean inhabitants relied on habitual and forceful precision grasping tasks.

Technical note: Development of regression equations to reassociate upper limb bones from commingled contexts.

The major upper limb skeletal elements (scapulae, humeri, ulnae and radii) are frequently utilized for sex determination and stature estimation. Consequently, in forensic cases that involve commingled remains, it is crucial to reassociate the aforementioned bones and attribute them to the right individual. The aim of the present study is to develop simple and multiple regression equations for sorting commingled human skeletal elements of the upper limb. In that context, ten common anthropological linear measurements of the articular surfaces of scapulae, humeri, ulnae, and radii were performed on 222 adult skeletons from the Athens Collection. The functions developed for sorting adjoining bones presented a strong positive linear relationship (r=0.69-0.93, p<0.05). The values of the determination coefficient statistics (r2=0.47-0.86) were found to be high and those of the standard errors of the estimate were found to be low (SEE=0.88-1.61). Blind tests indicated that when metric and morphoscopic sorting techniques are combined, a reliable sorting of the skeletal elements of the upper limbs is possible.

Experimental proof that multivariate patterns among muscle attachments (entheses) can reflect repetitive muscle use.

Reconstructions of habitual activity in past populations and extinct human groups is a primary goal of paleoanthropological research. Muscle attachment scars (entheses) are widely considered as indicators of habitual activity and many attempts have been made to use them for this purpose. However, their interpretation remains equivocal due to methodological limitations and a paucity of empirical data supporting an interaction between systematic muscle forces and entheseal morphology. We have recently addressed the first issue with precise three-dimensional measuring protocols and rigorous multivariate analysis focusing on the patterns among different entheses rather than comparing each entheseal structure separately. In a previous study, the resulting entheseal correlations reflected synergistic muscle groups that separated individuals according to their lifelong occupational activities. Here we address the second issue by applying this methodology to existing micro-computed tomography data from rats that have undergone muscle stimulation under experimental conditions. In contrast to previous animal studies, we relied on blind analytical procedures across two research institutions and controlled for most factors of interindividual variability. Results demonstrated that the multivariate associations among different entheseal surfaces can directly reflect repetitive muscle recruitment and provide essential information on muscle use.

Experimental evidence that physical activity affects the multivariate associations among muscle attachments (entheses).

The morphology of entheses (muscle/tendon attachment sites) on bones is routinely used in paleontological and bioarcheological studies to infer the physical activity patterns of ancient vertebrate species including hominins. However, such inferences have often been disputed owing to limitations of the quantitative methods commonly employed and a lack of experimental evidence demonstrating direct effects of physical activity on entheseal morphology. Recently, we introduced a new and improved method of quantifying and analyzing entheseal morphology that involves repeatable three-dimensional measurements combined with multivariate statistics focused on associations among multiple entheses. Here, to assess the validity of our method for investigating variation in entheseal morphology related to physical activity patterns, we analyzed femora of growing turkeys that were experimentally exercised for 10 weeks on either an inclined or declined treadmill or served as controls (N=15 individuals, 5 per group). Our multivariate approach identified certain patterns involving three different entheses (associated with the gluteus primus, medial gastrocnemius, vastus medialis and adductor magnus muscles) that clearly differentiated controls from runners. Importantly, these differences were not observable when comparing groups within each of the three entheseal structures separately. Body mass was not correlated with the resulting multivariate patterns. These results provide the first experimental evidence that variation in physical activity patterns has a direct influence on entheseal morphology. Moreover, our findings highlight the promise of our newly developed quantitative methods for analyzing the morphology of entheses to reconstruct the behavior of extinct vertebrate species based on their skeletal remains.

Is Bone Elevation in Hand Muscle Attachments Associated with Biomechanical Stress? A Histological Approach to an Anthropological Question.

In anthropological sciences, muscle attachments are typically utilized for reconstructing the physical activities of past human populations. This approach relies on the concept that entheseal bone morphology is influenced by cumulative biomechanical stress. A fundamental criterion for assessing the stage of entheseal change involves the proportion of elevated bone area. However, it is not yet clear if bone elevation is associated with biomechanical forces exerted during physical activity, while the histology of the entheses of the human hand, the least-bodyweight-bearing anatomical area, is not fully investigated. Multiple previous studies on entheses have concluded that the concentration of calcified fibrocartilage reflects the level of applied forces. On this basis, if hand entheseal surface elevation was associated with the level of biomechanical stress, then a greater amount of calcified fibrocartilage would be expected in entheses' central and more projecting bone areas. More importantly, individual entheses with a greater proportion of elevated bone areas would present a higher total concentration of calcified fibrocartilage. To test these hypotheses, this pilot study conducted a histological quantitative analysis on two thumb entheses of four fully-documented body donors. Across individuals, all central entheseal regions presented greater calcified fibrocartilage, while the entheses showing additional bone elevation in their marginal areas comprised substantially higher total values. The observations of this small-scale pilot study support the concept that interindividual differences in entheseal bone morphology are related to varying levels of biomechanical loading. Furthermore, they encourage future research to compile larger sample sizes, for comparing individuals with distinct lifelong activities. Anat Rec, 302:1093-1103, 2019. © 2018 Wiley Periodicals, Inc.

Evidence for precision grasping in Neandertal daily activities.

Neandertal manual activities, as previously reconstructed from their robust hand skeletons, are thought to involve systematic power grasping rather than precise hand movements. However, this interpretation is at odds with increasing archeological evidence for sophisticated cultural behavior. We reevaluate the manipulative behaviors of Neandertals and early modern humans using a historical reference sample with extensive genealogical and lifelong occupational documentation, in combination with a new and precise three-dimensional multivariate analysis of hand muscle attachments. Results show that Neandertal muscle marking patterns overlap exclusively with documented lifelong precision workers, reflecting systematic precision grasping consistent with the use of their associated cultural remains. Our findings challenge the established interpretation of Neandertal behavior and establish a solid link between biological and cultural remains in the fossil record.

A repeatable geometric morphometric approach to the analysis of hand entheseal three-dimensional form.

OBJECTIVES: The purpose of this study was to put forth a precise landmark-based technique for reconstructing the three-dimensional shape of human entheseal surfaces, to investigate whether the shape of human entheses is related to their size. The effects of age-at-death and bone length on entheseal shapes were also assessed. MATERIALS AND METHODS: The sample comprised high-definition three-dimensional models of three right hand entheseal surfaces, which correspond to 45 male adult individuals of known age. For each enthesis, a particular landmark configuration was introduced, whose precision was tested both within and between observers. The effect of three-dimensional size, age-at-death, and bone length on shape was investigated through shape regression. RESULTS: The method presented high intra-observer and inter-observer repeatability. All entheses showed significant allometry, with the area of opponens pollicis demonstrating the most substantial relationship. This was particularly due to variation related to its proximal elongated ridge. The effect of age-at-death and bone length on entheses was limited. DISCUSSION: The introduced methodology can set a reliable basis for further research on the factors affecting entheseal shape. Using both size and shape, variables can provide further information on entheseal variation and its biomechanical implications. The low entheseal variation by age verifies that specimens under 50 years of age are not substantially affected by age-related changes. The lack of correlation between entheseal shape and bone length or age implies that other factors may regulate entheseal surfaces. Future research should focus on multivariate shape patterns among entheses and their association with occupation.

Morphometric variation and ray allocation of human proximal hand phalanges.

ABSTRACT: In previous studies, the anatomy of proximal hand phalanges has been described and techniques of anatomical allocation have been developed. However, these rely on the observation of small phalangeal traits without providing a multivariate analysis of morphological variation. In bioarchaeological contexts, the form of these distinctive traits is often not clear and the use of alternative supplementary methods is vital. This study aims to conduct a multivariate analysis of proximal phalanges and introduce a new methodology of ray allocation for isolated proximal phalanges. The sample utilized involves 60 Greek individuals of the Athens Collection as well as 48 African-American and 49 European-American individuals of the Hamann-Todd collection. Multivariate analyses of variation were performed to assess differences across three population samples, sexes, and the five hand rays. Subsequently, a metric method for identifying the ray of isolated specimens was developed and a blind test was utilized to assess its value. The results demonstrated that there is extensive overlapping among population samples and substantial sexual dimorphism. Across rays, three morphological groups were observed. Identifying correctly the 1st and the 5th rays was possible in 100% and 93.0% of the cases, respectively. The classification accuracy for the 2nd ray reached the 91.0%. Sex-specific functions provided moderate accuracy for the 3rd and 4th rays, which ranged from 77.2 to 83.3%. The blind test indicated that the combined use of morphological and metric methods can provide a more certain anatomical allocation of proximal hand phalanges than each of these approaches separately.

Occupational manual activity is reflected on the patterns among hand entheses.

OBJECTIVES: In anthropological sciences, entheses are widely utilized as occupational stress markers. However, the reaction of entheseal surfaces to mechanical loading is not well understood. Furthermore, previous studies on entheses relied on the individuals' occupation-at-death. Past research by one of us has identified two patterns among hand entheses, proposing that they reflect two synergistic muscle groups. Here, we investigate the association between these patterns and habitual manual activity using an extensively documented skeletal sample and a three-dimensional system of quantification. MATERIALS AND METHODS: The hand bones utilized belong to 45 individuals from mid-19th century Basel. These were male adults (18 to 48 years old) who were not directly related, showed no manual pathological conditions, and whose occupational activities during their lifetime were clearly documented and could be evaluated according to historical sources. The patterns of entheses were explored using principal component analysis on both raw and size-adjusted variables. The influence of age-at-death, body mass, and bone length was assessed through correlation tests. RESULTS: The analysis showed that the previously proposed patterns of entheses are present in our sample. Individuals with the same or comparable occupations presented similar entheseal patterns. These results were not considerably affected by entheseal overall size, age-at-death, body mass, or bone length. DISCUSSION: Individuals involved in intense manual labor during their lifetime presented a distinctive pattern of hand entheses, consistent with the application of high grip force. By contrast, individuals with less strenuous and/or highly mechanized occupations showed an entheseal pattern related to the thumb intrinsic muscles.

Morphometric patterns among the 3D surface areas of human hand entheses.

OBJECTIVES: This study aimed to put forth a new and precise methodology for calculating the 3D areas of hand entheses. Furthermore, it investigated some of the factors affecting hand entheses development through an assessment of their correlations and morphometric patterns. MATERIALS AND METHODS: Fifty individuals from late-medieval San Pablo were studied. The sample consisted of high-definition 3D models of 17 entheses from the first, second, and fifth hand rays. A new methodology was introduced for quantifying their areas. Precision was verified using intraobserved and interobserver tests. Both raw and relative entheseal size (ratio of entheseal size to total bone surface size) were calculated. Bivariate analyses assessed the effect of age-group on entheses as well as the correlations across entheses of muscles that act synergistically, bone length, and articular surface size. The morphometric patterns among hand entheses were explored using a multivariate analysis. RESULTS: The methodology presented no significant error. Age-group variation does not seem to affect hand entheses. In relative size, only particular pairs presented significant association and the entheses involved were not correlated with bone length or articular surface size. The multivariate analysis demonstrated high sexual dimorphism in overall entheseal size as well as two morphometric trends among hand entheses. DISCUSSION: The proposed methodology can set the basis for further morphological 3D analysis of entheses. If biomechanical stress affects hand entheses, its impact would possibly be greater on their relative size. The morphometric patterns among entheses seem to reflect the performance of prehensile grips. Am J Phys Anthropol 160:694-707, 2016. © 2016 Wiley Periodicals, Inc.