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Frozen Environments and Soft Tissue Preservation
... Decomposition of cadavers is a dynamic ecological process dependent upon the environment, climate, insect, and vertebrate scavenging activity, microbial activity, and intrinsic properties of the individual antemortem [1]. Alteration of the ecosystem, such as exclusion of insects or burial, may lead to a unique trajectory for decomposition and potentially anomalous results [2][3][4]; therefore, it is critical to forensics that the interplay of ecological factors be understood. However, despite possible variation, certain patterns exist. ...
... Purge is associated with an opening of the abdominal cavity to the environment [11], at which point, the rate of decay may greatly increase as larval flies remove large portions of tissues [2,[13][14][15][16]. The final stages of decomposition last through to complete skeletonization and are the driest stages [2,3,9,17]. ...
... Bacteria are credited as a major driving force for the process of decomposition with numerous studies attempting to catalog the microbiome of decomposition [3,11,12,[17][18][19][20][21][22][23][24][25][26]. However, most of these studies have relied on culture-dependent techniques, which can limit the number of microorganisms documented. ...
Decomposition is a dynamic ecological process dependent upon many factors such as environment, climate, and bacterial, insect, and vertebrate activity in addition to intrinsic properties inherent to individual cadavers. Although largely attributed to microbial metabolism, very little is known about the bacterial basis of human decomposition. To assess the change in bacterial community structure through time, bacterial samples were collected from several sites across two cadavers placed outdoors to decompose and analyzed through 454 pyrosequencing and analysis of variable regions 3-5 of the bacterial 16S ribosomal RNA (16S rRNA) gene. Each cadaver was characterized by a change in bacterial community structure for all sites sampled as time, and decomposition, progressed. Bacteria community structure is variable at placement and before purge for all body sites. At bloat and purge and until tissues began to dehydrate or were removed, bacteria associated with flies, such as Ignatzschineria and Wohlfahrtimonas, were common. After dehydration and skeletonization, bacteria associated with soil, such as Acinetobacter, were common at most body sites sampled. However, more cadavers sampled through multiple seasons are necessary to assess major trends in bacterial succession.
... At this point, the rate of decay is reported by several authors to greatly increase as larval flies remove large portions of tissues; however, mummification may also occur, thus serving to preserve tissues6789. The final stages of decomposition last through to skeletonization and are the driest stages [7,10111213. When determining the time since death, or postmortem interval (PMI), forensic researchers may focus on progression through stages of decomposition as a function of temperature to help establish maximum and minimum time intervals for decomposition . ...
... (Figure 1). Accumulated degree-days above a base of 4oC (Figure 2) for each cadaver were calculated using the method of Micozzi et al. [12]. ...
... Using a base of 4oC the cadavers varied by 2.83 heatenergy units at the end of the study: STAFS 2011-006 accumulated 197.14 heat-energy units while STAFS 2011-016 accumulated 199.97 heat-energy units when end-bloat samples were taken (Figure 2). The thermal minimum of 4oC was chosen for this comparison with the assumption that the internal microorganisms are mesophiles and metabolism is inhibited at this temperature [12]. While we used a thermal base of 4oC, it is important to note that not all researchers in the field agree on an appropriate thermal minimum to use for the ADD calculations. ...
Human decomposition is a mosaic system with an intimate association between biotic and abiotic factors. Despite the integral role of bacteria in the decomposition process, few studies have catalogued bacterial biodiversity for terrestrial scenarios. To explore the microbiome of decomposition, two cadavers were placed at the Southeast Texas Applied Forensic Science facility and allowed to decompose under natural conditions. The bloat stage of decomposition, a stage easily identified in taphonomy and readily attributed to microbial physiology, was targeted. Each cadaver was sampled at two time points, at the onset and end of the bloat stage, from various body sites including internal locations. Bacterial samples were analyzed by pyrosequencing of the 16S rRNA gene. Our data show a shift from aerobic bacteria to anaerobic bacteria in all body sites sampled and demonstrate variation in community structure between bodies, between sample sites within a body, and between initial and end points of the bloat stage within a sample site. These data are best not viewed as points of comparison but rather additive data sets. While some species recovered are the same as those observed in culture-based studies, many are novel. Our results are preliminary and add to a larger emerging data set; a more comprehensive study is needed to further dissect the role of bacteria in human decomposition.
... The process of freezing can lead to tissue damage that may affect tissue decomposition rate. During freezing the withdrawal of water from cells leads to a decrease in diffusion and material Forensic Science International 183 (2009) [6][7][8][9][10][11][12][13] The study of decaying organisms and death assemblages is referred to as forensic taphonomy, or more simply the study of graves. This field is dominated by the fields of entomology, anthropology and archaeology. ...
... Cadavers frozen prior to being placed on a soil surface decayed aerobically while fresh cadavers decayed predominantly via anaerobic decomposition (putrefaction) [5]. This author suggested that this was caused by a biocidal effect on the enteric microbiota as a result of the temperatures associated with complete freezing of a cadaver [5][6][7]. This taphonomic study was a surface decomposition experiment rather than a burial event, limiting cadaver to soil contact. ...
... The pattern of decomposition appeared to progress from the outside in with relatively good preservation of internal organs [15]. It seems likely that freezing has at least a partial biocidal effect on the enteric flora [6,7] and may have caused some enzymes to lose their functional conformation. However in both situations the cadavers were on a soil surface rather than buried in a soil environment, while the current study is conducted in a burial environment. ...
Traditionally, soil evidence in forensic science has focused predominantly on the transference of soil particles from a victim
or suspect and a crime scene. However, a recent increase in forensic taphonomy research has highlighted the potential of soil
to provide key information to an investigation involving decomposed remains. A decomposing carcass can release a significant
pulse of nutrients into the surrounding soil (gravesoil) resulting in the retention of decomposition products in the soil
for a considerable period of time. In order to understand the complex associations between a decomposing carcass and the soil
system, research must be conducted in both controlled laboratory environments and outdoor field environments. This chapter
discusses two contrasting decomposition studies which aimed to investigate the cadaver/soil interaction. The first study investigated
the decomposition of small mouse carcasses buried in soil and was conducted within a controlled laboratory environment in
Western Australia. The second study investigated the decomposition of large pig carcasses placed on the soil surface and was
conducted in an outdoor field environment in southern Ontario. Both studies investigated a range of decomposition products
particularly focusing on carbon-based, nitrogen-based and phosphorus-based compounds as these were considered to offer the
most valuable information to address the research questions. The results of both studies provide the opportunity to comment
on the effect of carcass size, soil type and decomposition environment on the influx of decomposition products into the soil.
... Elevated temperatures alternately accelerate decomposition. Temperatures between 15 and 37°e provide a favorable environment for increased bacterial action (Micozzi 1997). Bodies in warm, moist climates decompose more rapidly due to the favorable conditions for the growth of putrefactive bacteria (Gonzales et al. 1954). ...
... The above processes may be slowed or even halted ifthe body is in an extremely cold climate or refrigerated. Micozzi observed that animals which were frozen and then thawed experienced prominent decay (from the outside in), whereas unfrozen animals experience mainly putrefaction (from the inside out) (Micozzi 1991Micozzi , 1997). He states "no putrefaction occurs at temperatures less than 4°e" (Micozzi 1991:37). ...
... Elevated temperatures alternately accelerate decomposition. Temperatures between 15 and 37°e provide a favorable environment for increased bacterial action (Micozzi 1997). ...
Thesis (M.A.)--University of Tennessee, Knoxville, 2002. Vita. Includes bibliographical references (p. 68-72).
... Some well-preserved bodies were found in Greenland back in the fifteenth century (Hart Hansen 1989), in circumpolar regions (e.g., Aleutians, Canada, and Siberia) (Hart Hansen 1998), in the Canadian Arctic (Beattie and Geiger 1987); on the island of Svalbard (Albrethsen 1989), in Argentina (Ceruti 2003 and of course the Tyrolian Iceman in the Alps (an exhaustive review of these cases was published by Lynnerup in 2007). Other studies showed the taphonomic effects of the freezing and thawing cycle on bones (Micozzi 1986;Calce and Rogers 2007) or, more generally, the effects of the cold climate during the decomposition process (Micozzi 1997;Bunch 2009). Recently, Pilloud et al. (2016) reported the taphonomical effects of an Alaska glacier on the remains of WWII soldiers. ...
... Continuous cycles of freezing and thawing affect the soil and surroundings. The environment and the soil are influenced by the effects of freezing (expansion of water within the soil) and by conformational changes due to crystallization of water at 4°C and subsequent thawing (Micozzi 1997). ...
The authors report the results obtained by a multidisciplinary investigation of nine cases of human remains belonging to unknown Austrian WWI soldiers found in a glacial environment in the North-Eastern Alps. The aim of this research is to investigate the biological profile, pathology and cause of death, and taphonomic details of the soldiers’ bodies preserved in the glacial environment of the Alps. The human remains were recovered by forensic archeological methods. The approach to the postmortem analysis was specifically chosen on a case by case basis according to the conditions of the different corpses, which varied from advanced decomposition to skeletonization. A multidisciplinary approach was applied to the human remains, including anthropological and taphonomical analysis and, in one case, botanic investigations on the intestinal contents. Soft tissues, where present, were mainly saponified, presenting pseudo-mummified areas and only in one case were partially mummified. Trauma analysis revealed several perimortem injuries. In addition peculiar weathering such as cracking, deformations, wear and abrasions were found on the bones of these individuals. This study, by means of a multidisciplinary approach, allowed the recovery and interpretation of much information on the life and death of these men who fought in incredible and merciless conditions, and increases and implements the data provided by documents during the “White War” phase of WWI.
... Evans site occurred after day 27, not associated with migration of larval calliphorids from the carcass, but rather to dehydration and drainage of ßuids. Catts (1990) stated that decomposition should be accelerated greatly at high elevations because of frequent, repeated freezing and thawing, and Micozzi (1986Micozzi ( , 1997 demonstrated experimentally that frozen and thawed carcasses have accelerated rates of decomposition and skeletal disarticulation. The carcasses in the current study did not freeze, even though they were often subjected to temperatures Ͻ0ЊC, and the decomposition process was prolonged instead of accelerated. ...
... The carcasses in the current study did not freeze, even though they were often subjected to temperatures Ͻ0ЊC, and the decomposition process was prolonged instead of accelerated. Insect activity and subsequent metabolic heat generation may have kept the carcass microenvironment at temperatures above that which inhibits bacterial growth (Micozzi 1997). Additionally, because of the small size of these carcasses, dehydrating more than decaying may have contributed to the delayed pattern of decomposition (Hewadikaram and Goff 1991). ...
Six rabbit carcasses were exposed during summer at elevations ranging from 2,713 to 4,191 m in Colorado to determine decomposition rates and arthropod succession patterns. Biomass removal, bloat, and internal and ambient air temperatures were measured and the arthropod community was monitored during 51-d succession studies. A total of 53 taxa was collected (range, 8-36 taxa), with diversity apparently decreasing as a negative function of elevation. Extensive scavenging altered decomposition rates and arthropod succession. Rates and duration of biomass removal and bloating of carcasses were slowed and prolonged at higher elevations.
... Temperatures in warm climates are conducive to registering visible changes in the decomposition process (bacteria, fungi, and scavengers); however, during winter the decomposition speed is reduced due to the suppression of biological activity (enzymes, bacteria, and insects) (Bunch 2009), freezing will preserve soft tissue (Micozzi 1997), and the detection of the body is difficult because the odor remains close to the body (Forbes et al. 2014). Therefore, the decomposition encompasses a series of consecutive physical-chemical disintegrative processes, whose start and end times depend on internal and external factors that surround the corpse. ...
... According to the information provided in Chapter 3, the nearest Pueblo III residences were some 8 to 9 km (5 miles (Duday and Guillon, 2007:126;Micozzi, 1996). Moreover, material evidence of shrouding and woven willow mats suggests that some or all P3WR corpses were wrapped at deposit within Wallace Ruin. ...
This thesis presents the results of a multi-disciplinary investigation of a variant Ancestral Pueblo mortuary rite at Wallace Ruin, southwest Colorado (USA). This multi-storey building is one of four Lakeview Group great houses connected to the Pueblo II regional system centred at Pueblo Bonito of Chaco Canyon some 100 km to the south. From c. AD 1060-1150, Wallace Ruin functioned as a ritual- economic centre with a small residential component. Then, habitation of this great house, the Lakeview Group and all domiciles within 10 kilometres ceased. However, three or more decades later at least six rooms were used as a non- residential, Pueblo III mortuary facility for a minimum of 32 individuals. This use was in marked contrast to the enduring Ancestral Pueblo practice of residential burial, usually in the extramural midden. The interrogation of several hypotheses concerning this anomaly entails a bioarchaeological approach that integrates skeletal evidence with spatial analyses regarding diachronic mortuary location choices at Wallace Ruin. Taphonomic methods that segregate bone displacements during corpse decomposition in a filled versus a void space provide accurate determinations of the depositional versus discovered mortuary microenvironments. The diachronic analysis of data from over 100 San Juan Region sites reveals additional ways in which Wallace’s Pueblo III mortuary program departs from longstanding communities of practice, whether great house or domicile. Chief among these are the use of a surface room floor and the postural arrangement of supine bodies with flexed knees upright. These results, in combination with material culture evidence, form the basis of this thesis: The Pueblo III mortuary program at Wallace Ruin is a variant rite that entails a Mesa Verde Region reformulation of a Pueblo Bonito house society. The sanctioned retrieval of objects of memory offers a plausible explanation for intentional intrusions into two mortuary contexts. Beyond addressing questions concerning Wallace Ruin, a major contribution of this study includes advancement of the house society model as an interpretive scheme for evaluating Mesa Verde Region socio-ritual dynamics. This research also demonstrates the effectiveness of anthropologie de terrain (Duday, 2006) to retrospectively determine the original status of Ancestral Pueblo mortuary microenvironments. The refinement developed for this study, in which Range of Motion criteria are used to detect large-scale movements of lower limbs during corpse decomposition, is suitable for bioarchaeological analyses the world over.
... According to the information provided in Chapter 3, the nearest Pueblo III residences were some 8 to 9 km (5 miles (Duday and Guillon, 2007:126;Micozzi, 1996). Moreover, material evidence of shrouding and woven willow mats suggests that some or all P3WR corpses were wrapped at deposit within Wallace Ruin. ...
This version of Volume 1 of my doctoral thesis contains no photographs of Ancestral Pueblo human remains.
... The long-term preservative effects of frozen environments upon soft tissue are well known (Micozzi 1991(Micozzi , 1997 and require little elaboration here. The most famous recent example of this process is the 1991 find of the frozen remains later dubbed "Ötzi" at an altitude over 3200 m in the Italian Alps. ...
The burial environment of remains, deposited in direct contact with soil or (starting) within a coffin, brings about multiple, often distinctive taphonomic effects that can be used to diagnose this type of postmortem history. This determination often indicates that the remains are of cemetery origin, therefore having a different path to ultimate case resolution. The taphonomic effects examined in this chapter include acidic soil corrosion, plant root invasion, bioturbation, surface staining, mineral oxide staining, adipocere formation, warping, cortical exfoliation of bone surfaces, water ring formation from pooling water, general state of bone preservation, and plowing disturbance. The more specialized effects associated with coffin burials include coffin wear (the erosion and flattening of bone surfaces in contact with the coffin) and signs/artifacts of previous autopsy or embalming. This chapter also examines and illustrates common types of coffin hardware used historically in the US and their use in dating a set of associated remains.
... The shift to surface rooms as mortuary locations in many Pueblo III residential sites means that the temporary placement of a corpse in such locations may have been open to consideration. Assuming climatic factors, the corpse would be subjected to freezing temperatures, in which case decomposition would likely have been delayed or stalled (Duday and Guillon, 2007:126;Micozzi, 1996). Moreover, material evidence of shrouding and woven willow mats suggests that some or all P3WR corpses were wrapped at deposit within Wallace Ruin. ...
This thesis presents the results of a multi-disciplinary investigation of a variant Ancestral Pueblo mortuary rite at Wallace Ruin, southwest Colorado (USA). This multi-story building is one of four Lakeview Group great houses connected to the Pueblo II regional system centered at Pueblo Bonito of Chaco Canyon some 100 km to the south. From c. AD 1060-1150, Wallace Ruin functioned as a ritual- economic centre with a small residential component. Then, habitation of this great house, the Lakeview Group and all domiciles within 10 kilometres ceased. However, three or more decades later at least six rooms were used as a non- residential, Pueblo III mortuary facility for a minimum of 32 individuals. This use was in marked contrast to the enduring Ancestral Pueblo practice of residential burial, usually in the extramural midden. The interrogation of several hypotheses concerning this anomaly entails a bioarchaeological approach that integrates skeletal evidence with spatial analyses regarding diachronic mortuary location choices at Wallace Ruin. Taphonomic methods that segregate bone displacements during corpse decomposition in a filled versus a void space provide accurate determinations of the depositional versus discovered mortuary microenvironments. The diachronic analysis of data from over 100 San Juan Region sites reveals additional ways in which Wallace’s Pueblo III mortuary program departs from longstanding communities of practice, whether great house or domicile. Chief among these are the use of a surface room floor and the postural arrangement of supine bodies with flexed knees upright. These results, in combination with material culture evidence, form the basis of this thesis: The Pueblo III mortuary program at Wallace Ruin is a variant rite that entails a Mesa Verde Region reformulation of a Pueblo Bonito house society. The sanctioned retrieval of objects of memory offers a plausible explanation for intentional intrusions into two mortuary contexts. Beyond addressing questions concerning Wallace Ruin, a major contribution of this study includes advancement of the house society model as an interpretive scheme for evaluating Mesa Verde Region socio-ritual dynamics. This research also demonstrates the effectiveness of anthropologie de terrain (Duday, 2006) to retrospectively determine the original status of Ancestral Pueblo mortuary microenvironments. The refinement developed for this study, in which Range of Motion criteria are used to detect large-scale movements of lower limbs during corpse decomposition, is suitable for bioarchaeological analyses the world over.
... The local temperature inside the sampling boxes was measured hourly by RC-5 USB Temperature Data Loggers (Elitech, China). Temperature data was converted into accumulated degree-days (ADD) according to the method of Micozzi [30] using a base temperature of 4 C and a maximum of 47 C. ...
Aims:
Bacteria are considered one of the major driving forces of the mammalian decomposition process and have only recently been recognised as forensic tools. At this point, little is known about their potential use as 'post-mortem clocks'. This study aimed to establish the proof of concept for using bacterial identification as post-mortem interval (PMI) indicators, using a multi-omics approach.
Methods and results:
Pieces of pork were placed in the University's outdoor facility and surface swabs were taken at regular intervals up to 60 days. Terminal restriction fragment length polymorphism (T-RFLP) of the 16S rDNA was used to identify bacterial taxa. It succeeded in detecting two out of three key contributors involved in decomposition and represents the first study to reveal Vibrionaceae as abundant on decomposing pork. However, a high fraction of present bacterial taxa could not be identified by T-RFLP. Proteomic analyses were also performed at selected time points, and they partially succeeded in the identification of precise strains, subspecies and species of bacteria that colonized the body after different PMIs.
Conclusion:
T-RFLP is incapable of reliably and fully identifying bacterial taxa, whereas proteomics could help in the identification of specific strains of bacteria. Nevertheless, microbial identification by next generation sequencing might be used as PMI clock in future investigations and in conjunction with information provided by forensic entomologists.
Significance and impact of the study:
To the best of our knowledge, this work represents the first attempt to find a cheaper and easily accessible, culture-independent alternative to high-throughput techniques to establish a 'microbial clock', in combination with proteomic strategies to address this issue.
... In theory, decomposition should still proceed at 0 °C because of the concentration of salts in a cadaver. However, Micozzi (1997) observed a lack of putrefaction at temperatures below 4 °C. This phenomenon is believed to be the result of the simultaneous suppression of decomposer activity and promotion of desiccation (Janaway 1996). ...
... Dekompozisyon süreci ve PMİ tahminine yönelik veriler ilk zamanlar daha çok Amerika Birleşik Devletleri Hawaii ve Tennessee eyaletlerindeki vaka çalışmalarından ve deneysel araştırmalardan elde edilmekteydi. Günümüzde Tennessee Üniversitesi olmak üzere Western Carolina Üniversitesi, Texas State Üniversitesi, Sam Houston State Üniversitesi ve Southern Illinois Üniversitesi içinde tahsis edilen araştırma sahalarında dekompozisyon süreci ve PMİ konusunda çalışmalar yürütülmektedir (27,47,56,58,59,(65)(66)(67)(68). Kuzey Amerika'da birikmiş gün sıcaklıkları PMİ'nin belirlenmesinde kullanılırken (41,47,58,69,70) Megyesi'nin geliştirmiş olduğu yöntem ise Montana, Iowa ve Indiana eyaletlerinde kullanılmış ve başarılı bir şekilde uygulanmıştır (69,70). ...
Postmortem interval arises one of the most important research topics in worldwide modern forensic science applications. In spite of utilizing morphological, biochemical, flow-cytometric, microbiological, entomological, anthropological, spectroscopic and main postmortem changes in postmortem interval estimation, it does not seem possible to get certain results by only one test or method. Because, there are many physical, chemical and biological processes affecting the parameters. Therefore, postmortem interval estimation needs development of previous methods and implementation of novel methods. In this regard, taphonomic methods need to be improved in postmortem interval estimation and regional factors and climate impact need to be determined by experimental studies. In particular, we are of the opinion that that more accurate estimation of postmortem interval will be achieved by determining regional factor involving postmortem period. This paper aims to evaluate the relationship between postmortem interval and accumulated degree days in respect of decomposition stages.
Key Words: Forensic Taphonomy, Postmortem Interval, Forensic Anthropology
... In theory, decomposition should still proceed at 0 °C because of the concentration of salts in a cadaver. However, Micozzi (1997) observed a lack of putrefaction at temperatures below 4 °C. This phenomenon is believed to be the result of the simultaneous suppression of decomposer activity and promotion of desiccation (Janaway 1996). ...
... The periosteum was left on the bone after removing the soft tissue. No freezing or heating of samples occurred before they were placed in the field because frozen and thawed tissues are more prone to insect and bacterial activity, which can increase decomposition rates [2,17]. Some refrigeration was necessary because the animals were slaughtered 24-120 h prior to pickup. ...
Twenty-five defleshed pig femora and 25 metatarsals were placed outdoors and observed over 291 days to establish: (1) bone weathering patterns for use in estimating time since death in Southern Ontario and (2) whether larger (femora) or smaller (metatarsals) bones provide a better indicator of time since death. Pig hind limbs were observed to determine a timeline for decomposition of soft tissues during the fall and winter. Ambient air temperature, humidity, precipitation, sunlight, soil pH, and freezing and thawing were considered as factors affecting the breakdown of bone. Weathering patterns were observed based on the extent of bleaching, amount of periosteum and soft tissues present, as well as the appearance of greasiness, cracking and flaking of cortical bone. Both entomological activity and climatic conditions affected soft tissue decomposition. Animal activity affected both the process of bone weathering and soft tissue decomposition, causing variability in sample decomposition and bone breakdown. The variation in microenvironment, partially caused by soil composition, introduced variability in bone weathering rates. Four bone weathering stages were established based on patterns observed. Femora proved to be more resilient and showed more degrees of change due to weathering, thus proving to be a better indicator of time since death than metatarsals.
Simple Summary
Understanding changes that occur after death, or post-mortem changes, based on decomposition, is very important to relate them to a post-mortem interval (PMI), the time elapsed between the moment of death and discovery of a body. Most studies on decomposition focus on large cadavers, leaving a knowledge gap for small cadavers, which are representative for infants and subadults. To fill this knowledge gap, a season-based subaerial outdoor decomposition study was conducted with small pig cadavers at the Forensic Anthropological Outdoor Research Facility located in Den Ham, The Netherlands, over a period of 4 years. This study revealed important findings related to a deviating decomposition rate during winter and the subsequent spring, reproducibility, the effect of body weight, post-mortem movement, the effect of heavy rainfall on insect activity, delayed bloating, the interaction of different insect species, and invertebrate activity.
Abstract
Studying post-mortem changes based on signs of decomposition (e.g., using scoring models) is one of the methods used in scientific studies to relate observable changes to the post-mortem interval (PMI). The majority of the studies on cadaver decomposition are based on large cadavers. There is limited literature on the decomposition pattern and rate of small cadavers, even though it is at least as important to be able to estimate the PMI for infants and subadults. Therefore, it is crucial to acquire knowledge of the decomposition process of child-sized remains. To fill this knowledge gap, a season-based subaerial outdoor decomposition study was conducted with small pig cadavers at the Forensic Anthropological Outdoor Research Facility located in Den Ham, The Netherlands, over a period of 4 years. Den Ham is located in the eastern part of the Netherlands, close to the German border, and has a temperate maritime climate, with a Cfb classification according to the Köppen–Geiger system. Salient findings were acquired during the decomposition study, specifically regarding a deviating decomposition rate during winter and the subsequent spring, reproducibility, the effect of body weight, post-mortem movement, the effect of heavy rainfall on insect activity, delayed bloating, the interaction of different insect species, and invertebrate activity. This article includes a systemic review of the results obtained during this four-year decomposition study and discusses the impact of the findings on the estimation of the PMI.
Forensic taphonomy is the study of human decomposition to determine circumstances and time-of- death. The taphonomic processes of decomposition commence almost immediately following death. Decomposition is a continuum and there are many taphonomic agents which will act on the body. Changes must be considered in the context of the decomposition environment. Scavengers contribute to the decomposition process. External factors that can affect the rate of decomposition are predominantly environmental variables. The deceased body itself also impacts its own rate of decay. Taken together this can provide for the formulation of the taphonomic expectation for a crime scene or a search area in which a clandestine grave or decomposed or decomposing body may be present.
In addition to differential culture-specific burial practices, the relative absence of juvenile skeletal remains in historic cemetery excavations has been explained by a comparatively rapid breakdown of immature bone. While the idea of differing breakdown rates between immature and mature bone is widely accepted, few experiments have provided evidence to support it.
This study uses a porcine model to explore the role of bone maturity with regards to the overall susceptibility of the skeleton to physical and compositional degradation in an experimental buried environment. Samples (n = 104) were mechanically defleshed and left to degrade in a climate-controlled greenhouse environment, buried 10 cm below the soil surface. Every month, for the span of 12 months, 4 immature and 4 mature bones were collected. Weight loss on ignition analysis was performed to determine changes in the composition of bone, and bone weathering analysis was carried out to quantify the physical breakdown of bone.
The results of this study indicate that in the first year after skeletonization of buried skeletal remains the compositional and physical breakdown of immature bones differ significantly from the changes seen in their mature bone counterparts. Immature bones seem more susceptible to compositional changes, but less affected by physical surface weathering. How these early differences in degradation affect the long-term survival of bone material and its post-depositional history in archaeological contexts, however, requires a longer study interval.
Although domestic pigs (Sus scrofa domesticus Erxleben) are generally accepted as appropriate human taphonomic proxies, taphonomic studies have used a wide variety of mammalian analogues. These include, among others, cattle (Bos taurus Linnaeus), sheep (Ovis aries Linnaeus), mice (Mus musculus Linnaeus) and brown rats (Rattus norvegicus Berkenhout), and their respective laboratory-reared subspecies. Furthermore, organs/tissue types from different species have been used, both with and without molecular analysis, notably in forensic entomology studies. The relevance, applicability and limitations of common, disparate and novel approaches must, therefore, be deliberated within the multi-disciplinary forensic ecogenomics and related forensic sub-disciplines. The implications of differences in animal model species, their organs/tissues and related parameters are explored and assessed to inform protocol standardization and knowledge transferability to often restricted cadaver-based analyses. The ultimate goal is potential validation and adoption of forensic ecogenomics in real crime scene toolkits in the determinations of postmortem, postmortem submersion, and postburial intervals.
This study's objective is to obtain accuracy and precision in estimating the postmortem interval (PMI) for decomposing human remains discovered in indoor settings. Data were collected prospectively from 140 forensic cases with a known date of death, scored according to the Total Body Score (TBS) scale at the post-mortem examination. In our model setting, it is estimated that, in cases with or without the presence of blowfly larvae, approximately 45% or 66% respectively, of the variance in TBS can be derived from Accumulated Degree-Days (ADD). The precision in estimating ADD/PMI from TBS is, in our setting, moderate to low. However, dividing the cases into defined subgroups suggests the possibility to increase the precision of the model. Our findings also suggest a significant seasonal difference with concomitant influence on TBS in the complete data set, possibly initiated by the presence of insect activity mainly during summer. PMI may be underestimated in cases with presence of desiccation. Likewise, there is a need for evaluating the effect of insect activity, to avoid overestimating the PMI. Our data sample indicates that the scoring method might need to be slightly modified to better reflect indoor decomposition, especially in cases with insect infestations or/and extensive desiccation. When applying TBS in an indoor setting, the model requires distinct inclusion criteria and a defined population.
The decomposition process of human remains can be used to estimate the post-mortem interval (PMI), but decomposition varies due to many factors. Temperature is believed to be the most important and can be connected to decomposition by using the accumulated degree days (ADD). The aim of this research was to develop a decomposition scoring method and to develop a formula to estimate the PMI by using the developed decomposition scoring method and ADD.
A decomposition scoring method and a Book of Reference (visual resource) were made. Ninety-one cases were used to develop a method to estimate the PMI. The photographs were scored using the decomposition scoring method. The temperature data was provided by the Royal Netherlands Meteorological Institute. The PMI was estimated using the total decomposition score (TDS) and using the TDS and ADD. The latter required an additional step, namely to calculate the ADD from the finding date back until the predicted day of death.
The developed decomposition scoring method had a high interrater reliability. The TDS significantly estimates the PMI (R² = 0.67 and 0.80 for indoor and outdoor bodies, respectively). When using the ADD, the R² decreased to 0.66 and 0.56.
The developed decomposition scoring method is a practical method to measure decomposition for human remains found on land. The PMI can be estimated using this method, but caution is advised in cases with a long PMI. The ADD does not account for all the heat present in a decomposing remain and is therefore a possible bias.
Electronic supplementary material
The online version of this article (10.1007/s00414-017-1700-9) contains supplementary material, which is available to authorized users.
This chapter presents the factors that may affect the preservation of human skeletal remains from the time of death of the individual to the moment of laboratory examination. The main osseous modifications produced by the natural environment and animal and human activity are outlined. Special emphasis is placed on the calculation of the minimum and the most likely numbers of individuals from commingled assemblages. For this purpose, step-by-step instructions are provided for the implementation of various methods, and a macro that automates calculations is given as online supplementary material. Examples of forms for recording the degree of skeletal preservation as well as taphonomic alterations are included as appendices.
The Southeast Texas Applied Forensics Science (STAFS) facility is one of five US centers dedicated to studying human decomposition. As cadavers decompose, they pass through five recognizable stages, with microorganisms and insects driving the initial “wet” stages. Microbiologically, cadavers decompose first from the inside out and shift from aerobic to anaerobic before outside microbes come to predominate. Knowledge about relative abundances of particular bacteria during decomposition could help in tracking the stages of cadaver decomposition since death. By developing more accurate measurements of additional ecosystem components surrounding cadavers, scientists will be better prepared to gauge progression through each stage of decomposition. © 2016, American Society for Microbiology. All rights reserved.
Bioarchaeology projects need to consider a full range of issues involved in carrying out a project. The legal aspects need to be attended to prior to designing the research to see if there are any caveats or conditions under which some research might be deemed unacceptable (such as destructive analytical techniques). Tribal authorities should be consulted and invited to participate in the project in situations where collaboration is desired. In conducting research, bioarchaeologists generally start with an interest that they have in answering a question or explaining an aspect of human behavior. Following a research strategy that includes (1) a thorough literature search, (2) framing a question that can be answered with the data, and (3) infusing the research project with a theoretical perspective can produce studies that are both integrated and engaged with important issues. In this way, bioarchaeological research will be of interest to a broad audience.
Forensic taphonomy is the study of postmortem processes which affect the preservation and recovery of human remains and help reconstruct the circumstances surrounding the death event. Many taphonomic processes affect the state of preservation of remains, including decomposition, diagenesis, scavenging, transport by physical and/or natural forces, and human action. Environmental factors such as temperature, humidity, and pH also influence the state of preservation. Human remains go through a series of decompositional stages that are somewhat predictable, with temperature being the primary factor responsible for the rate of decomposition. Forensic anthropologists study human decomposition to understand which taphonomic agents affected human remains, to aid in reconstructing the death event at a scene, and for estimating the postmortem interval. The postmortem interval can be estimated using accumulated degree days (ADD), which is used to count backward from the date of discovery to a likely time of death. A comprehensive understanding of taphonomy is also essential for differentiating postmortem changes on remains from causes such as trauma.
Human decomposition is a complex biological process driven by an array of variables which are not clearly understood. The medico-legal community have long been searching for a reliable method to establish the post-mortem interval (PMI) for those whose deaths have either been hidden, or gone un-noticed. To date, attempts to develop a PMI estimation method based on the state of the body either at the scene or at autopsy have been unsuccessful. One recent study has proposed that two simple formulae, based on the level of decomposition humidity and temperature, could be used to accurately calculate the PMI for bodies outside, on or under the surface worldwide. This study attempted to validate 'Formula I' [1] (for bodies on the surface) using 42 Canadian cases with known PMIs. The results indicated that bodies exposed to warm temperatures consistently overestimated the known PMI by a large and inconsistent margin for Formula I estimations. And for bodies exposed to cold and freezing temperatures (less than 4°C), then the PMI was dramatically under estimated. The ability of 'Formulae II' to estimate the PMI for buried bodies was also examined using a set of 22 known Canadian burial cases. As these cases used in this study are retrospective, some of the data needed for Formula II was not available. The 4.6 value used in Formula II to represent the standard ratio of time that burial decelerates the rate of decomposition was examined. The average time taken to achieve each stage of decomposition both on, and under the surface was compared for the 118 known cases. It was found that the rate of decomposition was not consistent throughout all stages of decomposition. The rates of autolysis above and below the ground were equivalent with the buried cases staying in a state of putrefaction for a prolonged period of time. It is suggested that differences in temperature extremes and humidity levels between geographic regions may make it impractical to apply formulas developed in one region to any other region. These results also suggest that there are other variables, apart from temperature and humidity that may impact the rate of human decomposition. These variables, or complex of variables, are considered regionally specific. Neither of the Universal Formulae performed well, and our results do not support the proposition of Universality for PMI estimation.
Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.
This paper reviews alterations to the human body that occur after death, and the numerous factors that serve to alter the rate and nature of decomposition. Forensic dating methods, with a focus on forensic anthropological techniques, currently in use and those that have only recently been introduced are outlined, with the strengths and weaknesses of each technique reviewed critically. Finally, recommendations for future research are proposed which highlight the problems that plague current research, serving to render much of the work currently being published as potentially inapplicable to forensic scientists concerned with time since death.
Human decomposition is a dynamic process that is influenced by both abiotic and biotic factors. Measuring these influences, in particular abiotic factors, on the decomposition process is often a challenge for scientists. Recently, researchers have turned to the use of advanced remote sensing technologies in forensic investigations. In this study, a new methodology is described that utilizes precise 3D images captured using terrestrial laser scanning (TLS) to calculate total solar irradiance on a cadaver in a partially forested environment. To test this new measurement approach under actual field conditions, three cadavers were placed in an outdoor environment to decompose. Laser scans were taken the day of placement and used to calculate the total solar irradiance at time points of 24 h, 1 week, and 1 month from placement. The results show that as time progresses, different cadavers at the field site and different areas of the same cadaver receive varying amounts of solar irradiance. The modeling based on these laser scans can be used to create predictive images of solar irradiance that may provide researchers with a new tool to help quantitatively assess the effect of solar irradiance on a cadaver ecosystem.
Timing of blunt force trauma in human bone is a critical forensic issue, but there is limited knowledge on how different environmental conditions, the duration of postmortem interval (PMI), different bone types and different animal models influence fracture morphology. This study aims at evaluating the influence of the type of postmortem environment and the duration of the postmortem period on fracture morphology, for distinguishing perimortem from postmortem fractures on different types of long bones from different species. Fresh limb segments from pig and goat were sequentially left to decompose, under 3 different environmental circumstances (surface, buried and submerged), resulting in sets with different PMI lengths (0, 28, 56, 84, 112, 140, 168 and 196 days), which were then fractured. Fractured bones (total=325; pig tibia=110; pig fibula=110; goat metatarsals=105) were classified according to the Fracture Freshness Index (FFI). Climatic data for the experiment location was collected. Statistical analysis included descriptive statistics, correlation analysis between FFI and PMI, Mann-Whitney U tests comparing FFI medians for different PMI's and linear regression analysis using PMI, pluviosity and temperature as predictors for FFI. Surface samples presented increases in FFI with increasing PMI, with positive correlations for all bone types. The same results were observed in submerged samples, except for pig tibia. Median FFI values for surface samples could distinguish bones with PMI=0 days from PMI≥56 days. Buried samples presented no significant correlation between FFI and PMI, and nonsignificant regression models. Regression analysis of surface and submerged samples suggested differences in FFI variation with PMI between bone types, although without statistical significance. Adding climatic data to surface regression models resulted in PMI no longer predicting FFI. When comparing different animal models, linear regressions suggested greater increases in FFI with increasing PMI in pig, compared to goat, in both surface and submerged environments, although statistically not significant. No differences were found between environments except for buried vs. submerged goat samples and surface vs. buried/submerged tibia pig samples. FFI showed a weak association with PMI and it seems to be affected by various factors, such as different bone types, decomposition environments and climatic factors. Nonetheless, the FFI shows promising discriminating power during the early postmortem period. The apparent variation between bone types from different species suggests that extrapolations to humans can be challenging.
Interest in the diseases that afflicted ancient populations (paleoepidemiology) has been increasing rapidly during the past several decades. It is now clear that a substantial amount of medical information present in the body at the moment of death remains accessible by laboratory studies of human mummies centuries or even millennia after death. However, both endogenous and environmental influences during the postmortem interval can alter the gross appearance and biochemical constituents of the corpse's tissues. Such diagenetic and structural changes can lead to diagnostic challenges. This presentation represents a review of the known effects of the postmortem alterations in structure and biochemical content in specimens of human mummies. Awareness of such variations can help prevent misinterpretations of studied findings. Unfortunately this topic's current database is dangerously small. A plea is included to encourage investigators to target this field for serious research goals.
constraints reveal that the opisthotonic posture is not a peri-but a postmortem phenomenon. By analysing the timeline of decomposition, it is possible to recognise different stages of decay, depending on the varying decay resistance of soft tissues. Adipocere formation must have blocked further decay until embedding was completed by minimal sedimen-tation. Analyses of the palaeoenvironment of the basins of the Solnhofen Archipelago show that the conditions of deposition of individual basins cannot be considered to be similar, even inside the same time frame. Therefore, a gen-eralised approach of looking at the depositional setting must be excluded. Assumptions by Faux and Padian (2007) that the accepted palaeoenvironmental reconstruction of the Solnhofen Fossillagerstätte has to be questioned in the light of the opisthotonic posture hypothesis enforce the need for a review of palaeoecological factors of the Franconian Plat-tenkalks from a taphonomic perspective.
Decomposition, a postmortem process including autolysis and putrefaction, is affected by many factors (e.g., humidity, microbial activity, soil properties). The purpose of this study was to determine the importance of soil type in decomposition process. Changes occurred in two intervals (3 and 6months) were evaluated using a total of 32 Sus scrofa limbs by burying in four different types of soil (loamy, clayey, sandy and organic). The extremities in all soils had lost weight over time; however, mass loss was greater in loamy and organic soils in both intervals. Entomological findings were also assessed. Obtained findings of soil analysis and evaluation of decomposition were compatible. In conclusion, the present study revealed that soil properties and textures should be taken into account in evaluation of decomposition and estimating postmortem interval in crime scene investigation.
Mummification processes, either artificial or natural, preserve the tissues from postmortem decay, but change them from their original state. In this study we provided the first comprehensive set of Hounsfield Unit (HU) ranges specific for tissues mummified under different environmental conditions (peat bog, cold-dry and hot-dry environment). We also analyzed the impact of different museal preservation techniques on the HU ranges, as e.g. in the Tollund Man and Grauballe Man, two bog bodies from Denmark. The HU results for mummies were compared with HU results from forensic cases, cremated and inhumated ancient human skeletal remains, and fossil animal bones. Knowledge of the typical HU range for the different tissues in mummies may help to avoid misinterpretation of increased or reduced radiodensity as evidence of paleopathological conditions. Finally, we demonstrate the practical benefit of using our re-defined HU ranges by showing the improved results of 3D visualization from automatic segmentation in an Inca mummy from Mount Llullaillaco.
The use of human braincases as drinking cups and containers has extensive historic and ethnographic documentation, but archaeological examples are extremely rare. In the Upper Palaeolithic of western Europe, cut-marked and broken human bones are widespread in the Magdalenian (∼15 to 12,000 years BP) and skull-cup preparation is an element of this tradition.
Here we describe the post-mortem processing of human heads at the Upper Palaeolithic site of Gough's Cave (Somerset, England) and identify a range of modifications associated with the production of skull-cups. New analyses of human remains from Gough's Cave demonstrate the skilled post-mortem manipulation of human bodies. Results of the research suggest the processing of cadavers for the consumption of body tissues (bone marrow), accompanied by meticulous shaping of cranial vaults. The distribution of cut-marks and percussion features indicates that the skulls were scrupulously 'cleaned' of any soft tissues, and subsequently modified by controlled removal of the facial region and breakage of the cranial base along a sub-horizontal plane. The vaults were also 'retouched', possibly to make the broken edges more regular. This manipulation suggests the shaping of skulls to produce skull-cups.
Three skull-cups have been identified amongst the human bones from Gough's Cave. New ultrafiltered radiocarbon determinations provide direct dates of about 14,700 cal BP, making these the oldest directly dated skull-cups and the only examples known from the British Isles.
The structural breakdown of skeletal remains follows a lengthy decomposition process, progressing from the appearance of cracking along the bone to complete loss of shape and skeletal integrity, that can occur in as early as 6 years or as long as 30. The length of time a set of skeletal remains takes to decompose depends heavily upon its micro-environment, the local context in which decomposition agents act on remains. Critical changes in the micro-context can drastically increase or slow the process. The burial of remains below the surface has been found to effectively shut out many of the most destructive decaying agents, such as the natural elements and insect and animal activity. This causes an increase in the amount of time needed to breakdown the skeletal remains. A better understanding of the decomposition process in varying micro-contexts is important for the ability to correctly estimate time since burial. This can aid not only in understanding of archaeological remains, but also in the identification of individuals in modern forensic and human rights cases. This study details the observations made during the excavation and analysis of burials on the Isla de Coiba off the coast of Panama. The excavation took place during the summer 2003 in an effort to identify several individuals who were believed to be part of the 'disappeared', people who went missing and believed to have been murdered under orders by the Torrijos and Noriega military regimes. Through the fieldwork analysis a decomposition timeline, specific for the Coiba micro-environment, was created. This new set of stages can be used to estimate time since burial in other areas whose local context is similar to that found on Coiba.
Exhumations of mass graves containing the remains of those executed during the Spanish Civil War and the subsequent Franco regime are currently being conducted at the request of surviving relatives. This individual case report illustrates how soft tissue preservation, through copper ion contact in one particular victim aided in preserving the projectile in an anatomical context, thereby permitting the correct interpretation of the projectile's path and angle, which otherwise would not have been possible as no bone tissue was affected. The information obtained has important relevance for human rights investigations and the work of the forensic anthropologist.
The study of decaying organisms and death assemblages is referred to as forensic taphonomy, or more simply the study of graves. This field is dominated by the fields of entomology, anthropology and archaeology. Forensic taphonomy also includes the study of the ecology and chemistry of the burial environment. Studies in forensic taphonomy often require the use of analogues for human cadavers or their component parts. These might include animal cadavers or skeletal muscle tissue. However, sufficient supplies of cadavers or analogues may require periodic freezing of test material prior to experimental inhumation in the soil. This study was carried out to ascertain the effect of freezing on skeletal muscle tissue prior to inhumation and decomposition in a soil environment under controlled laboratory conditions. Changes in soil chemistry were also measured. In order to test the impact of freezing, skeletal muscle tissue (Sus scrofa) was frozen (-20 degrees C) or refrigerated (4 degrees C). Portions of skeletal muscle tissue (approximately 1.5 g) were interred in microcosms (72 mm diameter x 120 mm height) containing sieved (2mm) soil (sand) adjusted to 50% water holding capacity. The experiment had three treatments: control with no skeletal muscle tissue, microcosms containing frozen skeletal muscle tissue and those containing refrigerated tissue. The microcosms were destructively harvested at sequential periods of 2, 4, 6, 8, 12, 16, 23, 30 and 37 days after interment of skeletal muscle tissue. These harvests were replicated 6 times for each treatment. Microbial activity (carbon dioxide respiration) was monitored throughout the experiment. At harvest the skeletal muscle tissue was removed and the detritosphere soil was sampled for chemical analysis. Freezing was found to have no significant impact on decomposition or soil chemistry compared to unfrozen samples in the current study using skeletal muscle tissue. However, the interment of skeletal muscle tissue had a significant impact on the microbial activity (carbon dioxide respiration) and chemistry of the surrounding soil including: pH, electroconductivity, ammonium, nitrate, phosphate and potassium. This is the first laboratory controlled study to measure changes in inorganic chemistry in soil associated with the decomposition of skeletal muscle tissue in combination with microbial activity.
Previous research into postmortem interval (PMI) estimation has been restricted to temperate and arid climates. Results suggest that decomposition rates may be significantly slower in cold weather regions. Preliminary research to conduct a cold weather time since death study has begun in Edmonton, which experiences mean monthly temperatures below freezing five months of the year. A case review at Edmonton's Office of the Chief Medical Examiner from 1990 to 1996 provided background information on a sample of 20 cases involving advanced decomposition, with partial to complete skeletonization of remains. Cases with a PMI of less than seven months were compared with regional weather records to establish the mean PMI temperature. Results indicate that skeletonization can occur in less than six weeks in summer and four months in winter, despite freezing temperatures. In some cases, postmortem animal activity accelerated decomposition rates.
Inferences of purposeful Middle Palaeolithic (MP) burial are almost universally accepted, despite published arguments that the pre-1960s discoveries are equally well explained by natural processes. In the modern human origins debate (perhaps the most hotly disputed question in palaeoanthropology) inferences of MP burial are crucial in arguments for an early Upper Pleistocene emergence of modern humans. The present paper contributed to that debate by re-examining a number of post-1960s excavations of MP hominid remains. Because these were excavated with meticulous attention to depositional circumstances and stratigraphic context, most palaeoanthropologists consider these inferences of purposeful burial to be based on irrefutable evidence. This paper focuses on the reasoning behind such claims, especially the assumption that articulated sketetal material is prima facie evidence for deliberate burial. First it reviews a range of processes operating in caves and rockshelters that condition the probability of articulated skeletal material preserving without hominid intervention. Processes such as deposition, decomposition, and disturbance are inherently more variable in caves and rockshelters than is usually acknowledged. The first section concludes that purposeful protection is not necessary to account for the preservation of articulated skeletal remains. The second part of the paper examines the published record from Qafzeh, Saint-Césaire, Kebara, Amud and Dederiyeh, where the majority of the remains claimed to have been buried are fragmented, incomplete, and disarticulated. This re-examination suggests that in all of the post-1960s cases of putative burial, the hominid remains occur in special depositional circumstances, which by themselves are sufficient to account for the preservation in evidence at these sites. This conclusion severely weakens arguments for purposeful burial at the five sites. Moreover, the equivocal nature of the evidence in the more recent cases renders even less secure the similar claims made for discoveries of hominid skeletal remains at La Chapelle-aux-Saints, Le Mousterier, La Ferrassie, Teshik-Tash, La Grotte du Régourdou, Shanidar, and several others. Finally, by highlighting the equivocal nature of the evidence, this paper underscores the ongoing need for palaeoanthropologists to specify as wide a range of taphonomic processes as possible when interpreting the archaeological record. This will aid in producing robust inferences, and will bring about increasingly accurate knowledge of when hominids became human.
A carrion study of the baby pig, Sus scrofa Linnaeus, was conducted during the summers of 1962 and 1963 in a mixed mesophytic hardwood-pine community at Clemson, South Carolina. Six stages of decomposition were delimited for carrion exposed to arthropods: fresh, bloated, active decay, advanced decay, dry, and remains. Five stages were recognized for carrion protected from arthropods: fresh, bloating and decomposition, flaccidity and dehydration, mummy, and desiccation and disintegration. Carrion free of insects decomposed and dried very slowly, retaining its form for many months, while 90% of the carrion open to insects was removed in 6 days. Carrion temperature during the bloated through advanced decay stages differed widely from that of air or soil. A definite ecological succession occurred among the fauna of carrion. Each stage of decay was characterized by a particular group of arthropods, each of which occupied a particular niche. Their activities were influenced by physical properties of carrion, rapidity of putrefaction, time of day, and weather. A total and 522 species representing 3 phyla, 9 classes, 31 orders, 151 families, and 359 genera were collected from decomposing pigs. Four orders of arthropods (Coleoptera, Diptera, Hymenoptera, and Araneida) accounted for 78% of the carrion fauna. Two coleopterous families, Histeridae and Staphylinidae and three dipterous families, Sarcophagidae, Calliphoridae, and Muscidae, represented 26% of the fauna.