Timothy P. Gocha

Tooth Cementum Annulation for Estimation of Age‐at‐Death in Thermally Altered Remains

Assessment of tooth cementum annulations (TCA) is acknowledged for its potential as a more accurate method for estimating age‐at‐death than conventional macroscopic methods typically employed. Thermal alteration of remains in a forensic context is not uncommon; however, the use of TCA in heat‐treated remains has hitherto received no quantitative assessment of accuracy. This study applies TCA to a sample of modern teeth of known demographics after experimental heat treatment at 600, 800 and 1000°C. Cementum annulations do survive thermal alteration; however, their visibility is dependent on exposure temperature. Physical and chemical changes resulted in TCA being applicable to only 63.3% of samples. An overall correlation to known age of r = 0.522 (p < 0.05) was found, while correlations of r = 0.868 (p < 0.01), r = 0.249, and r = −0.185, were found for 600, 800, and 1000°C subsets, respectively. These results indicate that in teeth exposed to temperatures >600°C, TCA no longer yields accurate enough results to be of use in forensic investigations.

Testing the applicability of six macroscopic skeletal aging techniques on a modern Southeast Asian sample

Most macroscopic skeletal aging techniques used by forensic anthropologists have been developed and tested only on reference material from western populations. This study examined the performance of six aging techniques on a known age sample of 88 Southeast Asian individuals. Methods examined included the Suchey-Brooks method of aging the symphyseal face of the os pubis (Brooks and Suchey, Hum. Evol. 5 (1990) 227), Buckberry and Chamberlains, Am. J. Phys. Anthropol. 119 (2002) 231 and Osborne et al.s, J. Forensic Sci. 49 (2004) 1 revisions of the Lovejoy et al., Am. J. Phys. Anthropol. 68 (1985) 15 method of aging the auricular surface of the ilium, İşcan et al.s, J. Forensic Sci. 29 (1984) 1094, İşcan et al.s, J. Forensic Sci. 30 (1985) 853 method of aging the sternal end of the fourth rib, and Meindl and Lovejoys, Am. J. Phys. Anthropol. 68 (1985) 57 methods for aging both lateral-anterior and vault sutures on the cranium. The results of this study indicate that application of aging techniques commonly used in forensic anthropology to individuals identified as Asian, and more specifically Southeast Asian, should not be undertaken injudiciously. Of the six individual methods tested here, the Suchey-Brooks pubic symphysis aging method performs best, though average age estimates were still off by nearly 10 years or greater. Methods for aging the auricular surface perform next best, though the Osborne et al. method works better for individuals below 50 years and the Buckberry and Chamberlain method works better for those above 50 years. Methods for age estimation from the sternal ends of the fourth rib and vault and lateral-anterior cranial sutures perform poorly and are not recommended for use on remains of Southeast Asian ancestry. Combining age estimates from multiple indicators, specifically the pubic symphysis and one auricular surface method, was superior to individual methods. Data and a worked example are provided for calculating the conditional probability that an individual belongs to a particular age decade, though overall age estimates may still be broad.

Technical note: The use of geographical information systems software for the spatial analysis of bone microstructure.

Geographic information systems (GIS) software is typically used for analyzing geographically distributed data, allowing users to annotate points or areas on a map and attach data for spatial analyses. While traditional GIS-based research involves geo-referenced data (points tied to geographic locations), the use of this technology has other constructive applications for physical anthropologists. The use of GIS software for the study of bone histology offers a novel opportunity to analyze the distribution of bone nano- and microstructures, relative to macrostructure and in comparison to other variables of interest, such as biomechanical loading history. This approach allows for the examination of characteristics of single histological features while considering their role at the macroscopic level. Such research has immediate promise in examining the load history of bone by surveying the functional relationship between collagen fiber orientation (CFO) and strain mode. The diversity of GIS applications that may be utilized in bone histology research is just beginning to be explored. The goal of this study is to introduce a reliable methodology for such investigation and our objective is to quantify the heterogeneity of bone microstructure over an entire cross-section of bone using ArcGIS v 9.3 (ESRI). This was accomplished by identifying the distribution of remodeling units in a human metatarsal relative to bending axes. One biomechanical hypothesis suggests that CFO, manifested by patterns of birefringence, is indicative of mode of strain during formation. This study demonstrates that GIS can be used to investigate, describe, and compare such patterns through histological mapping.

Spatial variation in osteon population density at the human femoral midshaft: histomorphometric adaptations to habitual load environment

Intracortical remodeling, and the osteons it produces, is one aspect of the bone microstructure that is influenced by and, in turn, can influence its mechanical properties. Previous research examining the spatial distribution of intracortical remodeling density across the femoral midshaft has been limited to either considering only small regions of the cortex or, when looking at the entirety of the cortex, considering only a single individual. This study examined the spatial distribution of all remodeling events (intact osteons, fragmentary osteons, and resorptive bays) across the entirety of the femoral midshaft in a sample of 30 modern cadaveric donors. The sample consisted of 15 males and 15 females, aged 21–97 years at time of death. Using geographic information systems software, the femoral cortex was subdivided radially into thirds and circumferentially into octants, and the spatial location of all remodeling events was marked. Density maps and calculation of osteon population density in cortical regions of interest revealed that remodeling density is typically highest in the periosteal third of the bone, particularly in the lateral and anterolateral regions of the cortex. Due to modeling drift, this area of the midshaft femur has some of the youngest primary tissue, which consequently reveals that the lateral and anterolateral regions of the femoral midshaft have higher remodeling rates than elsewhere in the cortex. This is likely the result of tension/shear forces and/or greater strain magnitudes acting upon the anterolateral femur, which results in a greater amount of microdamage in need of repair than is seen in the medial and posterior regions of the femoral midshaft, which are more subject to compressive forces and/or lesser strain magnitudes.

Beyond Taphonomy: Exploring Craniometric Variation Among Anatomical Material.

Anatomical crania are occasionally encountered in forensic anthropology laboratories when that material is mistaken for forensically significant human remains. Using craniometric analyses and statistical measures of sample homogeneity, we determine whether anatomical material can be described as a single, homogenous group or as a diverse mix of populations. Twenty‐one interlandmark distances were collected from 85 anatomical preparations. Distance measures were calculated between all pairs using a pooled within‐sample variance/covariance matrix and then subjected to a Defrise‐Gussenhoven test between each paired distance to test whether each pair was drawn randomly from the same population. In the Defrise‐Gussenhoven analysis, twenty‐two percent (n = 66) of the 300 pairwise combinations were significant at the 0.05 level or below. The level of homogeneity suggests a majority of that material originated from the subcontinent of India or West Asia. Therefore, anatomical material can be viewed as a moderately homogenous group, but with a shared taphonomic history.