An evaluation of soil chemistry in human cadaver decomposition islands: Potential for estimating postmortem interval (PMI).

Soil samples from the Forensic Anthropology Research Facility (FARF) at Texas State University, San Marcos, TX, were analyzed for multiple soil characteristics from cadaver decomposition islands to a depth of 5centimeters (cm) from 63 human decomposition sites, as well as depths up to 15cm in a subset of 11 of the cadaver decomposition islands plus control soils. Postmortem interval (PMI) of the cadaver decomposition islands ranged from 6 to 1752 days. Some soil chemistry, including nitrate-N (NO3-N), ammonium-N (NH4-N), and dissolved inorganic carbon (DIC), peaked at early PMI values and their concentrations at 0-5cm returned to near control values over time likely due to translocation down the soil profile. Other soil chemistry, including dissolved organic carbon (DOC), dissolved organic nitrogen (DON), orthophosphate-P (PO4-P), sodium (Na+), and potassium (K+), remained higher than the control soil up to a PMI of 1752days postmortem. The body mass index (BMI) of the cadaver appeared to have some effect on the cadaver decomposition island chemistry. To estimate PMI using soil chemistry, backward, stepwise multiple regression analysis was used with PMI as the dependent variable and soil chemistry, body mass index (BMI) and physical soil characteristics such as saturated hydraulic conductivity as independent variables. Measures of soil parameters derived from predator and microbial mediated decomposition of human remains shows promise in estimating PMI to within 365days for a period up to nearly five years. This persistent change in soil chemistry extends the ability to estimate PMI beyond the traditionally utilized methods of entomology and taphonomy in support of medical-legal investigations, humanitarian recovery efforts, and criminal and civil cases.

Metric variation in the human occipital bone: forensic anthropological applications.

Sex and race variation of the occipital bone have been previously investigated, but particular examination of the effect of age and ancestry on sexual dimorphism has not been addressed. This paper examines morphological variation associated with sex and ancestry in the condylar region of the occipital bone and the effect of age and ancestry on the estimation of sex. Models previously published by Holland are also tested, and methodological problems are addressed. The results indicate that age does not have an effect on sexual dimorphism, but that whites exhibit greater, although not significantly, more sexual dimorphism than blacks. Significant sex and ancestry variation is present in the condylar region of the occipital bone, but neither sex nor ancestry could be estimated accurately using measurements of this anatomical region defined by Holland.

Sex variation in the second cervical vertebra.

The second cervical vertebra can be used to estimate sex with 83% accuracy in unidentified human skeletal remains. Reported here are the necessary statistics, based on 8 dimensions taken from 400 second cervical vertebrae, for the computation of customized discriminant functions. Discriminant function equations developed using variables selected in a stepwise procedure are also presented here as an example of the usefulness of this bone in estimating sex.

Anthropometric variation among the Sioux and the Assiniboine.

Historically, the Assiniboine are thought to have split from the Yanktonai Sioux some time in the early 17th century, but this view has been challenged by some linguists, archeologists, and skeletal biologists. Our purpose here is to examine the population structure of the Sioux and the Assiniboine, as reflected in 6 head and 6 body anthropometric dimensions, and to investigate the hypothesis that the Assiniboine diverged relatively recently from the Yanktonai Sioux. For both males and females there is an overall significant division effect, and the FST value indicates a fair amount of differentiation among these closely related groups. The Assiniboine are clearly distinct from all 3 Sioux divisions. The Assiniboine also exhibit a higher within-group phenotypic variance than expected, indicating that their differentiation is due to time and gene flow from outside groups. Among the Sioux divisions the Santee and Yankton-Yanktonai are the most similar, especially in head and face dimensions. The results of this study do not support the historical account of Assiniboine origins. The high degree of differentiation between the Yanktonai and Assiniboine suggests a much more distant split between the Assiniboine and the Sioux than has been traditionally put forth.