Biology subjects

Hlusko, L. J.

Publications and source records attributed to Hlusko, L. J..

6 recordsLinked to original sources

bioRxiv2026

DeMoDa: A global open access database for comparative research in human dental morphological variation

Human dental morphology is diverse and varies both within and between populations worldwide. Common variants include different numbers of cusps and roots, as well as different configurations in the fissures, ridges, and grooves on tooth crowns. Because teeth preserve well in taphonomic contexts and retain strong genetic signatures in their morphology, researchers across disciplines use dental form for research ranging from population affinity identification in forensic cases to the reconstruction of population history in archaeological and paleontological studies, and to explore the genetic underpinnings of dental development. However, these analyses are limited, as no publicly available comprehensive database of human dental morphological variation currently exists. Data are typically shared only within professional networks, excluding scientists outside those circles. Information is dispersed across repositories and the supplementary materials that accompany peer-reviewed publications, creating a fragmented and difficult-to-navigate data landscape. Although numberous dental anthropologists devoted their careers to collecting extensive datasets from thousands of individuals worldwide, their data have not yet been published in raw form nor made compatible. Here, we introduce the Dental Morphological Database (DeMoDa), an open access repository comprising 246 dental traits for 17,308 individuals across 32 major geographic regions worldwide spanning the past several thousand years. These data are from the legacy datasets of Turner, Hanihara, Scott, and Irish. Because these researchers used different scoring systems, we developed a scoring system with two steps that enables the three most-common scoring systems to be combined. We provide two versions of the data that correspond to these two steps: one with more nuanced trait scores at the cost of a smaller sample size, and another with less nuanced trait scores but broader sample coverage. We discuss the implications of publishing these legacy data and outline our decision-making process that guided their release in accordance with both the FAIR and CARE principles of open science.

evolutionary biology↗

bioRxiv2025

Tracking molar wear in captive baboons: sex and age effects using a modified Scott scoring system

ObjectivesThis study evaluates molar wear progression in a captive baboon population under controlled dietary and environmental conditions. By comparing the dentin exposure ratio (DER) with a newly developed quadrant-based modification of Scotts dental wear scoring system (Krueger-Scott method), we evaluate how wear patterns vary by age, sex, and occlusal region. Materials and MethodsMandibular second molars (M2) were assessed at two timepoints, during life and postmortem, in 201 captive baboons from the Southwest National Primate Research Center. Krueger-Scott and DER data were collected from 3D intraoral scans processed in MEDIT Link software. The Krueger-Scott scores assigned ordinal scores (1-10) to four equal quadrants of each M2 based on enamel facet development and dentin exposure. Statistical analyses tested relationships between wear progression, quadrant location, sex, and age. ResultsKrueger-Scott scores and DER values increased significantly between timepoints, indicating wear progression. However, Krueger-Scott scores revealed strong functional patterning: buccal and lingual cusps showed high within-group correlations and weaker cross- group correlations. Males showed significantly higher wear than females, despite being younger on average. The relationship between age and wear progression differed by sex. DiscussionThe Krueger-Scott method provided a more anatomically informative and efficient approach to tracking occlusal wear than DER. It captured regional wear variation and functional asymmetries that DER could not detect. Even under controlled conditions, sex-based differences in wear emerged, likely reflecting behavioral, morphological, or enamel structural variation. These findings offer a comparative baseline and demonstrate the utility of quadrant- level scoring for interpreting wear in extant and extinct taxa.

animal behavior and cognition↗

bioRxiv2024

Assessing tooth wear progression in primates: A longitudinal study using intraoral scanning technology

Intraoral scanners are widely used in a clinical setting for orthodontic treatments and tooth restorations, and are also useful for assessing dental wear and pathology progression. In this study, we assess the utility of using an intraoral scanner and associated software for quantifying dental tissue loss in non-human primates. An upper and lower second molar for 31 captive hamadryas baboons (Papio hamadryas) were assessed for dental tissue loss progression over multiple years (n = 62 teeth). The animals are part of the Southwest National Primate Research Center and were all fed the same monkey-chow diet over their lifetimes. Two molds of each dentition were taken at either two- or three-year intervals, and the associated casts scanned using an intraoral scanner (Medit i700). Tissue loss was calculated in WearCompare by superimposition of the two scans followed by subtraction analysis. Four individuals had dental caries, and were assessed separately. The results demonstrate the reliability of these techniques in capturing tissue loss data, evidenced by the alignment consistency between scans, lack of erroneous tissue gain between scans, and uniformity of tissue loss patterns among individuals (e.g., functional cusps showing the highest degree of wear). The average loss per mm{superscript 2} per year for all samples combined was 0.05 mm3 (0.04 mm3 for females and 0.08 mm3 for males). There was no significant difference in wear progression between upper and lower molars. Substantial variation in the amount of tissue loss among individuals was found, despite their uniform diet. These findings foster multiple avenues for future research, including the exploration of wear progression across dental crowns and arcades, correlation between different types of tissue loss (e.g., attrition, erosion, fractures, caries), interplay between tissue loss and microwear/topographic analysis, and the genetic underpinnings of tissue loss variation.

evolutionary biology↗

bioRxiv2023

Uncovering the mosaic evolution of carnivoran skeletal systems

The diversity of vertebrate skeletons is often attributed to adaptations to distinct ecological factors such as diet, locomotion, and sensory environment. Although the adaptive evolution of skull, appendicular skeleton, and vertebral column is well studied in vertebrates, comprehensive investigations of all skeletal components simultaneously are rarely performed. Consequently, we know little of how modes of evolution differ among skeletal components. Here, we tested if ecological and phylogenetic effects led to distinct modes of evolution among the cranial, appendicular, and vertebral regions in extant carnivoran skeletons. Using multivariate evolutionary models, we found mosaic evolution in which only the mandible, hindlimb, and posterior (i.e., last thoracic and lumbar) vertebrae showed evidence of adaptation towards ecological regimes whereas the remaining skeletal components reflect clade-specific evolutionary shifts. We hypothesize that the decoupled evolution of individual skeletal components may have led to the origination of distinct adaptive zones and morphologies among extant carnivoran families that reflect phylogenetic hierarchies. Overall, our work highlights the importance of examining multiple skeletal components simultaneously in ecomorphological analyses. Ongoing work integrating the fossil and paleoenvironmental record will further clarify deep-time drivers that govern carnivoran diversity we see today and reveal the complexity of evolutionary processes in multicomponent systems.

evolutionary biology↗

bioRxiv2023

Severe enamel defects in wild Japanese macaques

Plane-form enamel hypoplasia (PFEH) is a severe dental defect in which large areas of the crown are devoid of enamel. This condition is rare in humans and rarer in wild primates. The etiology of PFEH has been linked to exposure to severe disease, malnutrition, environmental toxins, and other systemic conditions. Similar defects have also been associated with genetic conditions such as amelogenesis imperfecta. In this study, we examined the prevalence of all types of enamel hypoplasia in several populations of wild Japanese macaques (Macaca fuscata) with the aim of providing context for the severe defects found in macaques from Yakushima Island. We found that macaques from other islands and from the mainland of Japan have low prevalence of the more common types of enamel hypoplasia and none exhibit PFEH. In contrast, 10 of the 21 individuals (48%) from Yakushima Island displayed uniform and significant PFEH, with all 10 living in two adjacent locations in the south of the island. All permanent teeth were affected to varying degrees except for first molars, and the mineral content of the remaining enamel in teeth with PFEH is normal (i.e., no hypo- or hyper mineralization). Given that the affected individuals have smaller first molars compared to non-affected macaques, and that they all underwent dental development during a period of substantial human-related habitat change, we conclude that the PFEH likely resulted from environmental stress. Extreme weather events on the island may also have influenced the formation of these defects. Additionally, it is plausible that a documented recent population bottleneck could have heightened the susceptibility of these macaques to PFEH. Further research on living primate populations is needed to better understand the causes of PFEH in wild primates and to evaluate whether such features can be used to assess the impact of human-related disturbance.

ecology↗

bioRxiv2023

OH 89: A newly described ~1.8-million-year-old hominid clavicle from Olduvai Gorge

ObjectivesHere, we describe the morphology and geologic context of OH 89, a [~]1.8million-year-old partial hominid clavicle from Olduvai (Oldupai) Gorge, Tanzania. We compare the morphology and clavicular curvature of OH 89 to modern humans, extant apes, and a sample of other hominid fossil clavicles. Materials and MethodsComparative samples include 25 modern human clavicles, 30 Gorilla, 31 Pan, 7 Papio, and five hominid clavicles. Length regression on midshaft size using the extant comparative samples is used to estimate the total length of OH 89. A set of 9 linear measurements are taken from each individual. We also describe a new methodology for measuring clavicular curvature using measurements of sternal and acromial curvature, from which an overall curvature measurement is calculated. A principal component analysis (PCA) and a t-distributed stochastic neighbor embedding (tSNE) analysis are used to compare the morphology of OH 89 with the extant and fossil comparative samples. ResultsOur new method of measuring clavicular curvature successfully separates the different genera of the extant clavicles. The length estimate and sternal and acromial curve measurements for OH 89 falls within the larger male humans. The PCA shows OH 89 and most of the fossil hominids falling between the modern human and Pan groups, while the t-SNE suggests that OH 89, KSD-VP-1/1, KNM-ER 1808, and OH 48 are more similar to each other than to any of the other groups. This analysis also plots KNM-WT 15000 with the modern humans and Krapina 158 with the Pan individuals. DiscussionThe OH 89 clavicle derives from an individual of unknown hominid species with a shoulder breadth similar to that of a large human male. The curvature of OH 89 is relatively human-like relative to its length. Our new methodology for measuring clavicular curvature, combined with the utilization of t-SNE analyses and comparison of t-SNE results to PCA results, provides greater separation of genera than previously used methods, and wider use of t-SNE may be useful in paleoanthropological work.

evolutionary biology↗