Anthroengineering: an independent interdisciplinary field

In recent decades, funding agencies, institutes and professional bodies have recognized the profound benefits of transdisciplinarity in tackling targeted research questions. However, once questions are answered, the previously abundant support often dissolves. As such, the long-term benefits of these transdisciplinary approaches are never fully achieved. Over the last several decades, the integration of anthropology and engineering through inter- and multidisciplinary work has led to advances in fields such as design, human evolution and medical technologies. The lack of formal recognition, however, of this transdisciplinary approach as a unique entity rather than a useful tool or a subfield makes it difficult for researchers to establish laboratories, secure permanent jobs, fund long-term research programmes and train students in this approach. To facilitate the growth and development and witness the long-term benefits of this approach, we propose the integration of anthropology and engineering be recognized as a new, independent field known as anthroengineering . We present a working definition for anthroengineering and examples of how anthroengineering has been used. We discuss the necessity of recognizing anthroengineering as a unique field and explore potential novel applications. Finally, we discuss the future of anthroengineering, highlighting avenues for moving the field forward

Biomechanics in anthropology

Biomechanics is the set of tools that explain organismal movement and mechanical behavior and links the organism to the physicality of the world. As such, biomechanics can relate behaviors and culture to the physicality of the organism. Scale is critical to biomechanical analyses, as the constitutive equations that matter differ depending on the scale of the question. Within anthropology, biomechanics has had a wide range of applications, from understanding how we and other primates evolved to understanding the effects of technologies, such as the atlatl, and the relationship between identity, society, culture, and medical interventions, such as prosthetics. Like any other model, there is great utility in biomechanical models, but models should be used primarily for hypothesis testing and not data generation except in the rare case where models can be robustly validated. The application of biomechanics within anthropology has been extensive, and holds great potential for the future

Technical note: A freeware, equitable approach to dental topographic analysis

Dental topographic analysis has proved a valuable tool for quantifying dental morphology. Established workflows often use proprietary software for pre-processing dental surfaces, rendering the method expensive and inaccessible to many. This study explores the use of freeware pre-processing alternatives. We tested 4 decimation tools and 13 smoothing tools across 7 different freeware packages. Surfaces generated via proprietary software could not be replicated, but it was possible to obtain statistically similar measurements using freeware. Based on this investigation, we propose a freeware workflow for researchers to conduct dental topographic analysis, with the expectation that their results will be comparable to that obtained through proprietary methods

Food mechanical properties and dietary ecology

Interdisciplinary research has benefitted the fields of anthropology and engineering for decades: a classic example being the application of material science to the field of feeding biomechanics. However, after decades of research, discordances have developed in how mechanical properties are defined, measured, calculated, and used due to disharmonies between and within fields. This is highlighted by “toughness,” or energy release rate, the comparison of incomparable tests (i.e., the scissors and wedge tests), and the comparison of incomparable metrics (i.e., the stress and displacement‐limited indices). Furthermore, while material scientists report on a myriad of mechanical properties, it is common for feeding biomechanics studies to report on just one (energy release rate) or two (energy release rate and Young's modulus), which may or may not be the most appropriate for understanding feeding mechanics. Here, I review portions of materials science important to feeding biomechanists, discussing some of the basic assumptions, tests, and measurements. Next, I provide an overview of what is mechanically important during feeding, and discuss the application of mechanical property tests to feeding biomechanics. I also explain how 1) toughness measures gathered with the scissors, wedge, razor, and/or punch and die tests on non‐linearly elastic brittle materials are not mechanical properties, 2) scissors and wedge tests are not comparable and 3) the stress and displacement‐limited indices are not comparable. Finally, I discuss what data gathered thus far can be best used for, and discuss the future of the field, urging researchers to challenge underlying assumptions in currently used methods to gain a better understanding between primate masticatory morphology and diet

Detecting and Characterizing the Fabella with High Frame-Rate Ultrasound Imaging

The fabella is a sesamoid bone usually located in the tendon of the lateral head of the gastrocnemius muscle, behind the knee joint. Prevalence rates in human populations vary widely with an average of 42.5% people having a fabella. Clinically, it is associated with a number of knee ailments, most notably the osteoarthritis of the knee and generalized knee pain (i.e., fabella syndrome). As the function of the fabella remains unknown, the biomechanical consequences of fabella presence/absence can only be speculated. Successfully detecting the fabella, measuring its size and determining its shape, are off importance for clinical and evolutionary researchers. In this work, we compare plane wave imaging with conventional focused imaging and evaluate their performance for detecting and characterizing the fabella

On the relationship between tooth shape and masticatory efficiency: a finite element study

Dental topography has successfully linked disparate tooth shapes to distinct dietary categories, but not to masticatory efficiency. Here, the relationship between four dental topographic metrics and brittle food item breakdown efficiency during compressive biting was investigated using a parametric finite element model of a bunodont molar. Food item breakdown efficiency was chosen to represent masticatory efficiency as it isolated tooth–food item interactions, where most other categories of masticatory efficiency include several aspects of the masticatory process. As relative food item size may affect the presence/absence of any relationship, four isometrically scaled, hemispherical, proxy food items were considered. Topographic metrics were uncorrelated to food item breakdown efficiency irrespective of relative food item size, and dental topographic metrics were largely uncorrelated to one another. The lack of a correlation between topographic metrics and food item breakdown efficiency is not unexpected as not all food items break down in the same manner (e.g., nuts are crushed, leaves are sheared), and only one food item shape was considered. In addition, food item breakdown efficiency describes tooth–food item interactions and requires location and shape specific information, which are absent from dental topographic metrics. This makes it unlikely any one efficiency metric will be correlated to all topographic metrics. These results emphasize the need to take into account how food items break down during biting, ingestion, and mastication when investigating the mechanical relationship between food item shape, size, mechanical properties, and breakdown, and tooth shape

The landscape of tooth shape: Over 20 years of dental topography in primates

Diet plays an incontrovertible role in primate evolution, affecting anatomy, growth and development, behavior, and social structure. It should come as no surprise that a myriad of methods for reconstructing diet have developed, mostly utilizing the element that is not only most common in the fossil record but also most pertinent to diet: teeth. Twenty years ago, the union of traditional, anatomical analyses with emerging scanning and imaging technologies led to the development of a new method for quantifying tooth shape and reconstructing the diets of extinct primates. This method became known as dental topography. [Abstract copyright: © 2020 The Authors. Evolutionary Anthropology published by Wiley Periodicals LLC.

Extant ape dental topography and its implications for reconstructing the emergence of early Homo

Dental topography has successfully predicted the diets of species in several extant and extinct 11 mammalian clades. However, dental topographic dietary reconstructions have high success rates only 12 when closely related taxa are compared. Given the dietary breadth that exists among extant apes and 13 likely existed among fossil hominins, dental topographic values from many species and subspecies of 14 great apes are necessary for making dietary inferences about the hominin fossil record. Here, we 15 present the results of one metric of dental topography, Dirichlet normal energy (DNE), for seven groups 16 of great apes (Pongo pygmaeus pygmaeus, Pan paniscus, Pan troglodytes troglodytes and 17 schweinfurthii, Gorilla gorilla gorilla, Gorilla beringei graueri and beringei). DNE was inadequate at 18 differentiating folivores from frugivores, but was adequate at predicting which groups had more fibrous 19 diets among sympatric African apes. Character displacement analyses confirmed there is substantial 20 dental topographic and relative molar size (M1:M2 ratio; length, width, and area) divergence in sympatric 21 apes when compared to their allopatric counterparts, but character displacement is only present in 22 relative molar size when DNE is also considered. Presence of character displacement is likely due to 23 indirect competition over similar food resources. Assuming similar ecological conditions in the Plio-24 Pleistocene, the derived masticatory apparatuses of the robust australopithecines and early Homo may 25 be due to indirect competition over dietary resources between the taxa, causing dietary niche 26 partitioning. Our results imply that dental topography cannot be used to predict dietary categories in 27 fossil hominins without consideration of ecological factors such as dietary and geographic overlap. In 28 addition, our results may open new avenues for understanding the community compositions of early 29 hominins and the formation of specific ecological niches among hominin taxa

Human biological variation in sesamoid bone prevalence: the curious case of the fabella

The fabella is a sesamoid bone located in the gastrocnemius behind the lateral femoral condyle. In humans, fabellae are 3.5 times more common today than they were 100 years ago, with prevalence rates varying between and within populations. In particular, fabellae have been assumed to be more common in Asians than non‐Asians, equally common in men and women, potentially more common in older individuals, and bilateral cases (one per knee) appear to be more common than unilateral ones. The roles of genetic and environmental factors in this phenotypic variation have been hypothesized, but not rigorously investigated. Given its clinical and evolutionary significance (i.e. being associated with several knee ailments, causing medical issues on its own, interfering with medical devices, and being less common in humans than in other mammals), it is important comprehensively to understand prevalence rate variation, and the roles of genetics and environmental factors in that variation. To address these questions, we performed a meta‐analysis on data from studies published from 1875 to 2018 to investigate possible variation in sexual dimorphic (n = 22 studies, 7911 knees), ontogenetic (n = 10 studies, 4391 knees), and global (n = 65 studies, 21 626 knees) fabella prevalence rates. In addition, we investigated what proportion of cases are bilateral (n = 37 studies, 900 individuals), and among unilateral cases (n = 20 studies, 204 individuals), if fabellae are more common in the left or right knee. Our results show that, today, fabellae are 2.47–2.60% more common in men than women, and prevalence rates increase ontogenetically in old age (i.e. 70 years old), implying that fabellae can ossify early (i.e. 12 years old) or late in life. Approximately 72.94% of cases are bilateral, and among unilateral ones, fabellae are equally common in right and left knees. There is marked regional variation in fabella prevalence rates, with rates being highest in Asia, followed by Oceania, South America, Europe, Middle East, and North America, and lowest in Africa. Worldwide, an average of 36.80% of knees has ossified fabellae detectable by dissection. These results imply that, while the ability to form a fabella may be genetically controlled, the mechanisms that trigger fabella ossification may be environmentally controlled. What these environmental factors are, can only be speculated

Unique myological changes associated with ossified fabellae: a femorofabellar ligament and systematic review of the double-headed popliteus

The fabella is a sesamoid bone embedded in the tendon of the lateral head of the gastrocnemius. It is the only bone in the human body to increase in prevalence in the last 100 years. As the fabella can serve as an origin/insertion for muscles, tendons, and/or ligaments (e.g., the oblique popliteal and fabellofibular ligaments), temporal changes in fabella prevalence could lead to temporal changes in “standard” knee anatomy. The aim of this study was to investigate unique myological changes to the posterolateral corner knee associated with ossified fabella presence and perform a systematic review to contextualize our results. Methods Thirty-three fresh frozen cadaveric knees were considered. As the knees were all used for previous experimentation, the knees were in variable levels of preservation. Those with adequate preservation were used to determine ossified fabella presence/absence. When ossified fabellae were present, unique myologies associated with the fabella were recorded. A systematic review was performed on the double-headed popliteus to investigate possible correlations between this anatomical variant and the fabella. Results Of the 33 knees, 30 preserved enough soft tissue to determine fabella presence/absence: 16/30 knees had fabellae (five cartilaginous and 11 ossified). Eight of the eleven knees with ossified fabellae retained enough soft tissue to investigate the posterolateral knee anatomy. Of these, 4/8 exhibited unique myological changes. One knee had a double-headed popliteus muscle where one head originated from the medial side of a large, bulbous fabella. A systematic review revealed double-headed popliteus muscles are rare, but individuals are 3.7 times more likely to have a fabella if they have a double-headed popliteus. Another knee had a large, thick ligament stretching from the lateral edge of the fabella to the inferoposterior edge of the lateral femoral epicondyle, deep to the lateral collateral ligament (LCL) and near the popliteal sulcus. We found no mention of such a ligament in the literature and refer to it here as the “femorofabellar ligament”. In all four knees, the plantaris and lateral gastrocnemius appeared to share a common tendinous origin, and the fabella was located at/near the junction of these muscles. In the case of the double-headed popliteus, the fabella clearly served as an origin for the plantaris. Conclusions Despite being found in an average of 36.80% of human knees, most standard anatomical models fail to account for the fabella and/or the unique myological changes associated with fabella presence. Although our sample is small, these data highlight aspects of human biological variability generally not considered when creating generalized anatomical models. Further work is needed to identify additional changes associated with ossified fabellae and the functional consequences of omitting these changes from models