Tal Simmons

Debugging decomposition data - comparative taphonomic studies and the influence of insects and carcass size on decomposition rate.

Abstract:  Comparison of data from a variety of environments and ambient temperatures has previously been difficult as few studies used standardized measures of time/temperature and decomposition. In this paper, data from previous studies and recent experiments are compared using simple conversions. These conversions allow comparison across multiple environments and experiments for the first time. Plotting decomposition score against logADD allows the exponential progression of decomposition to be expressed as a simple linear equation. Data comparison from many environments and temperatures shows no difference in decomposition progression when measured using Accumulated Degree Days. The major effector of change in rate was insect presence, regardless of depositional environment, species, or season. Body size is significant when carcasses are accessed by insects; when insects are excluded, while bodies are indoors, submerged, or buried, then decomposition progresses at the same rate regardless of body size.

Reconsidering the auricular surface as an indicator of age at death.

Using standards established by Lovejoy et al. to estimate age at death from auricular surface morphology, 266 individuals of documented age, sex, and ancestry from the Terry and Bass Donated Collections were scored. Analysis of covariance (ANCOVA) indicates that for the factors that could be controlled, age is the sole influence on auricular surface morphology. Ancestry and sex had no significant effect on auricular phase expression. No evidence of secular changes was detected when comparing the Terry Collection (early 20th century) to the Bass Collection (later 20th century). Pearson correlations reveal that several of the subcomponents of the auricular surface (superior and inferior demifaces, left and right sides, transverse organization, texture) correspond with age equally well, although a combined scoring of all features performs slightly better than any one indicator taken alone. Not surprisingly, only 33% of the sample was correctly aged when using the 5-year age ranges provided by Lovejoy et al., suggesting that the published ranges are much too narrow to be used in forensic contexts. To assess the variation in age per phase, standard descriptive statistics and error ranges were calculated and can be employed by forensic anthropologists when estimating the age of an unidentified decedent. Because the mean ages of some of the eight phases did not differ significantly from one another, a modified six-phase system is presented. The auricular surface performs as well as any other single skeletal indicator of adult age. This research suggests that a statistically-informed approach should be taken in order to fully understand the drawbacks and limitations of any aging method.

The Effect of Repeated Physical Disturbance on Soft Tissue Decomposition?Are Taphonomic Studies an Accurate Reflection of Decomposition?

Abstract:  Although the relationship between decomposition and postmortem interval has been well studied, almost no studies examined the potential effects of physical disturbance occurring as a result of data collection procedures. This study compares physically disturbed rabbit carcasses with a series of undisturbed carcasses to assess the presence and magnitude of any effects resulting from repetitive disturbance. Decomposition was scored using visual assessment of soft tissue changes, and numerical data such as weight loss and carcass temperature were recorded. The effects of disturbance over time on weight loss, carcass temperature, soil pH and decomposition were studied. In addition, this study aimed to validate some of the anecdotal evidence regarding decomposition. Results indicate disturbance significantly inversely affects both weight loss and carcass temperature. No differences were apparent between groups for soil pH change or overall decomposition stage. An insect‐mediated mechanism for the disturbance effect is suggested, along with indications as to why this effect may be cancelled when scoring overall decomposition.

The Influence of Insects on Decomposition Rate in Buried and Surface Remains

Abstract:  This article reports results of a comparative study of decomposition rates of wild rabbit (Oryctolagus cuniculus) which were either (i) buried after exposure to insect activity, (ii) buried without exposure, (iii) kept above ground behind an insect screen, or (iv) continuously exposed above ground in a field experiment. Results showed that dipteran oviposition occurred consistently in groups i and iv only. Decomposition rates (measured by Total Body Score every c. 50 accumulated degree days [ADD]) of rabbits kept behind the screen and those buried without exposure showed no difference (p = 0.450). This was significantly slower than those buried after exposure (p = 0.0016) which was in turn significantly slower than those continuously exposed (p << 0.001). Temperatures collected from animals showed the presence of feeding larvae increased intra‐abdominal temperatures to >5°C above ambient. The findings support the assertion that insect presence is the primary agent affecting decomposition rate via tissue consumption and also the heat they generate.

The Influence of Penetrative Trauma on the Rate of Decomposition

Abstract:  An understanding of the factors affecting decomposition is important for the accurate estimation of postmortem interval. An experimental study on the influence of penetrating trauma on decomposition rate was carried out using the domestic pig, Sus scrofa. The results of this study were: (i) Diptera were preferentially attracted to and oviposited at natural orifices. Trauma sites were not preferentially selected for oviposition; (ii) no differences between trauma and non‐trauma groups were found in time to skeletonization, weight loss (p = 0.906), total body score (p = 0.824), body temperature (p = 0.967), or changes in soil pH (p = 0.684); and (iii) the effect of investigator disturbance was significant when decomposition was measured as weight loss (p = 0.000). This study suggests that penetrating trauma of the type used in this study cannot be considered a major factor in the rate of decomposition and time to skeletonization of a gunshot trauma victim.

Predicting the Postmortem Submersion Interval for Human Remains Recovered from U.K. Waterways

Abstract:  This article aims to increase accuracy in estimating the postmortem submersion interval (PMSI) for bodies recovered from rivers in the United Kingdom. Data were collected from closed case files, crime scene reports, and autopsy files concerning bodies recovered over a 15‐year period from the River Clyde, Scotland, and the River Mersey and canals in northwest England. One hundred and eighty‐seven cases met the study criteria and were scored by quantifying the overall amount of decomposition observed in each case. Statistical analysis showed that the duration of a body’s submergence in water and the temperatures to which it was exposed, as measured in accumulated degree days (ADD), had a significant effect on the decay process. Further analysis indicated that there were no significant differences in decomposition between the waterways. By combining the data from all study samples, it was possible to produce a single linear regression model for predicting ADD from observed decomposition.

Frontal bone morphometrics of southwest Asian Pleistocene hominids

Abstract Morphometric relationships among late middle and early late Pleistocene fossil hominids from southwestern Asia are examined utilizing multivariate analyses of frontal bones. Particular emphasis is placed on assessing the interaction of size and shape factors in determining relationships among these specimens. Results of these analyses can be summarized in five points. First, techniques which maximize pattern recognition based primarily on shape factors provide the most reliable information pertinent to phylogenetic relationships among these hominids. Second, the Zuttiyeh specimen does not exhibit a greater similarity to the early “modern” Skhu¯l/Qafzeh hominids than to Levantine Neandertals. Third, the Shanidar Neandertals do not cluster closely with Levantine archaic humans. Fourth, the Mousterian-associated Skhu¯l/Qafzeh hominids exhibit distinct similarities to archaic humans, but the Skhu¯l hominids give no unequivocal indication of being “hybrids” between the Qafzeh people and Neandertals. Finally, clear patterns of change occur in frontal bone morphology from the early “modern” (Mousterian-associated) Skhu¯l/Qafzeh hominids to early Upper Paleolithic-associated humans from the Levant.

The avifauna of the early Epipalaeolithic site of Ohalo II (19 400 years BP), Israel: species diversity, habitat and seasonality

The early Epipalaeolithic site of Ohalo II offers evidence that, some 19 400 years BP, prehistoric people on the shore of the Sea of Galilee exploited birds in large numbers as a food source and for the decorative value of their feathers and claws. The superb preservation of even the most delicate fauna at this site enabled an extensive analysis of a type rarely possible with avian remains of this antiquity. Certain types of birds were obtained preferentially, although a broad variety of avifauna was taken; preliminary analysis of some 488 identifiable bone fragments indicates that 16 families, 40 genera, and 68 different species are represented in the archaeological assemblage. As might be expected from a lakeshore site, the remains of waterfowl abound. The most diversity within a family occurs among the Anatidae, with ten genera and 22 species; however, the most frequently occurring birds are those of the family Podicipidae, or grebes, which account for approximately one-third of the assemblage. Species common to a variety of other environments are found in significant numbers as well (namely the Accipitridae). Large birds dominate the assemblage and the number of species represented by each family is disproportionate to the numerical frequency of those species at present, with passeriformes relatively poorly represented. The regular migration pattern of birds today broadly indicates that the site was occupied during the months of September–November and February–April. There are, however, a number of species that appear in this region today only from December through to March, which might indicate a longer, semi-permanent encampment. A biseasonal, or perhaps extended winter occupation pattern at Ohalo II seems to support a shift away from the generalized foraging economy of hunter–gatherers and to indicate the onset of planned intensive collecting, thus foreshadowing the initial steps toward sedentism.

The Influence of Preburial Insect Access on the Decomposition Rate

Abstract:  This study compared total body score (TBS) in buried remains (35 cm depth) with and without insect access prior to burial. Sixty rabbit carcasses were exhumed at 50 accumulated degree day (ADD) intervals. Weight loss, TBS, intra‐abdominal decomposition, carcass/soil interface temperature, and below‐carcass soil pH were recorded and analyzed. Results showed significant differences (p << 0.001) in decomposition rates between carcasses with and without insect access prior to burial. An approximately 30% enhanced decomposition rate with insects was observed. TBS was the most valid tool in postmortem interval (PMI) estimation. All other variables showed only weak relationships to decomposition stages, adding little value to PMI estimation. Although progress in estimating the PMI for surface remains has been made, no previous studies have accomplished this for buried remains. This study builds a framework to which further comparable studies can contribute, to produce predictive models for PMI estimation in buried human remains.

Oral Inflammation, Tooth Loss, Risk Factors, and Association with Progression of Alzheimer's Disease

Periodontitis is a polymicrobial chronic inflammatory disease of tooth-supporting tissues with bacterial etiology affecting all age groups, becoming chronic in a subgroup of older individuals. Periodontal pathogens Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola are implicated in the development of a number of inflammatory pathologies at remote organ sites, including Alzheimers disease (AD). The initial inflammatory hypothesis proposed that AD hallmark proteins were the main contributors of central nervous system (CNS) inflammation. This hypothesis is expanding to include the role of infections, lifestyle, and genetic and environmental factors in the pathogenesis of AD. Periodontal disease (PD) typifies a condition that encompasses all of the above factors including pathogenic bacteria. These bacteria not only are the source of low-grade, chronic infection and inflammation that follow daily episodes of bacteremia arising from everyday tasks such as brushing, flossing teeth, chewing food, and during dental procedures, but they also disseminate into the brain from closely related anatomical pathways. The long-term effect of inflammatory mediators, pathogens, and/or their virulence factors, reaching the brain systemically or otherwise would, over time, prime the brains own microglia in individuals who have inherent susceptibility traits. Such susceptibilities contribute to inadequate neutralization of invading agents, upon reaching the brain. This has the capacity to create a vicious cycle of sustained local inflammatory milieu resulting in the loss of cytoarchitectural integrity and vital neurons with subsequent loss of function (deterioration in memory). The possible pathways between PD and AD development are considered here, as well as environmental factors that may modulate/exacerbate AD symptoms.