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Browsing by Author "Du, Andrew, committee member"

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    Cut it out: a novel, quantifiable approach to kerf mark analysis using 3D confocal microscopy and machine learning
    (Colorado State University. Libraries, 2023) Benson, Wyatt H., author; Pante, Michael C., advisor; Du, Andrew, committee member; Jackson, Jessica, committee member
    Forensic methods must adhere to the Daubert standard to be deemed as admissible evidence in court. Current critiques regarding how well this standard is upheld have also challenged whether current forensic practices truly meet the Daubert standard. For example, kerf mark analyses can reveal trace evidence in sharp force trauma cases but a lack of quantitative studies and standardized analytical methods leave the field open to potential scrutiny. While previous research frequently classifies marks as either the product of serrated or non-serrated blades, further identifications are rarely made confidently. The goal of this project is to determine whether variations in 3D micromorphological variables can be used to quantitatively discriminate between kerf marks made by different knife types and blade classes. Here, kerf marks were produced using five different knives on bovid diaphyses, 3D scanned using profilometric microscopy, measured for both volumetric and profile variables, then analyzed using quadratic discriminant analysis. Results show individual knives were classified correctly in only 52% of attempts. However, blade class – serrated vs. non-serrated vs. partially serrated – was successfully identified in 97% of attempts. Significantly, our results differentiate between kerfs produced by serrated blades, non-serrated blades, and partially serrated blades, not only allowing for more specific blade identifications but also producing a quantifiable and replicable method meeting the Daubert criteria.
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    Unpacking the trunk: pelvic-thoracic relationships in modern Homo sapiens
    (Colorado State University. Libraries, 2024) Shaw, Zoë G., author; Glantz, Michelle, advisor; Du, Andrew, committee member; Throckmorton, Zachary, committee member
    It is generally accepted that throughout the history of the genus Homo, shifts in body morphology have aligned with the emergence of distinct hominin populations (Ruff, 1991, 1994, 2010; Schmid et al., 2013; Walker & Leakey, 1993). The human trunk, comprised of the ribcage, pelvis, and spine, contributes the most to overall body shape. However, how the thorax and pelvis are morphologically related in modern humans is not well understood. The fragmented nature of the human fossil record poses challenges in reconstructing the morphology of the trunk. Research on extant nonhuman ape morphology has suggested covariance between the inferior ribcage and upper pelvis, and it has been proposed that this pattern holds for premodern hominin groups (Schmid, 1983; Schmid et al., 2013). This expectation of covariance between the upper and lower portions of the trunk has allowed researchers to infer body shape and size with incomplete remains (Schmid, 1983; Schmid et al., 2013; Jellema et al., 1993). However, recent findings have served to challenge previously accepted trends in hominin body shape, calling into question whether the hominin trunk is integrated as was previously thought (Arsuaga et al., 1999; Day, 1971; Rosenberg, 2007; Simpson et al., 2008). The current study expands on previous work by Torres-Tamayo et al. (2018, 2020). Five linear measurements from a mixed sample of 85 living humans were taken from computed topography scans rendered in 3D. Results suggest a minimal correlation between pelvic dimensions and inferior ribcage width, with some variations observed by sex. Understanding this relationship in modern humans aids in evaluating researchers' expectations when interpreting past hominin body shapes and offers new insights into the origins of modern human and neandertal anatomy. Since evidence of integration is weak, results suggest that the thorax and pelvis may be under different selective pressures in modern H. sapiens.